Molecular Genetics of Schizophrenia from Approximately Dehydrogenase (PRODH2, 22Q11.21), G72 (13Q34) with the Middle of 2001

Moleculargenetics of schizophrenia:a review of the recent literature DouglasF. Levinson

Purpose of review Abbreviations

The recent literatureon the moleculargenetics of schizophrenia ASP affected sibling pair is reviewed, to familiarizethe reader with several important LD linkage disequilibrium NIMH National Institute of Mental Health developments as well as a broad range of research efforts in a NMDA N-methyl-o-asparlate rapidly progressing field. SNP single-nucleotidepolymorphism UTR untranslated region Recent findings VCFS velo-cardio facial svndrome New genome scan projects, seen in the light of previousscans, provide support for schizophreniacandidate regions on :a.,2003 LippincottWilliams & Wilkins -7367 chromosomes1q, 2q, 5q, 6p, 6q, 8p, 10p, 13q, 15q and 22q. 0951 Linkage disequilibriummapping studiesof severalof these regions have produced evidence from relativelylarge samples lntroduction supportingthe associationof schizophreniato neuregulin-1 This article will revicw new literature relevant ro rhe (NRG1, 8p21-p12), dysbindin(DfNBPt, 6p22.3),protine molecular genetics of schizophrenia from approximately dehydrogenase (PRODH2, 22q11.21), G72 (13q34) with the middle of 2001. Remarkable progress has been made weaker evidence implicating its interactinggene o-amino acid in the 15 years since serious investigation began in this oxidase (DAAO, 12q24), and catechol-O-methyltransferase field. The past year alone witnessed the publication of (COMT,22q11.21). Other reportshave described including the eight new genome scans [,"-6",7',8"] and a meta- application of microarray techniques to schizophreniapost- analysis of published genome scans [9"], rvirh evidence mortem tissue, candidate gene studies in diverse regions, that gcnome scan data are starting to converge on a sct of efforts to develop quantitativephenotypes (e.g. neuroimaging chromosomal regions; five reporusof substantial evidence and neuropsychologicalvariables) and proposed models of for the associationof schizophrenia with specific genes in schizophreniapathogenesis. positional candidate regions [10"-14"], and rwo reporrs Summary of thc use of microarray technology to screen for genes Schizophrenialinkage findings are beginningto convergeon a showing differential expression in the brains of schizo- number of chromosomalregions. Linkage disequilibrium phrenia patients [15',16"], one of which detectcd a gene mapping studies are beginningto produce findingsof great for which evidence for generic association was also interestin some of these regions,and additionalfindings should observed ll7"l.It appears likely that positional cloning, be expected. Enlarged linkage and associationsamples, microarray and other tcchnologies will soon producc combined with rapidlyevolving technologies, hold out the rcplicable findings that will begin ro elucidate the promise that in the next 5-10 years, the role of some specific pathophysiology of this severe comn-ron disease. schizophreniasusceptibility genes will be confirmedresulting in an initial understandingof the pathogenesisof schizophrenia. Progress in finding genes through positional cloning methods Keywords Positional cloning is the primary srraregyavailable for schizophrenia,genetics, genetic linkage,genetic association, finding susceptibilitygcnes for disorderswith no knor,vn candidate genes pathoprhysiology.The strategyis summarizedin Table 1.

CurrOpin Psychlatry 16:157-170. rr 2OO3 Lippincott Williams & Wilkins. Multiply affected families are screencd with a DNA markermap of all chrornosomes(genome scan). Statistical Department of Psychiatry, Universityof PennsylvaniaSchool of Medicine, analyscsconsider whether ill relativcs Philadelphia,PA 19104-3309, USA have inherited the samemarker alleles, indicating the proximity of a disease Correspondenceto DouglasF. Levinson,MD, Departmentof Psychiatry,University of susceptibility gene. For complex disorders (such as PennsylvaniaSchool of Medicine,3535 Market Street,Room 4006, Philadelphia,pA schizophrenia) 19104-3309, USA that probably have multiple interacting Tel:+1 215746 5151;fax: +1 2157465155; e-mail:[email protected],upenn.edu susceptibilitygencs, genome scanscan only locategcnes within 10000 000-30 000 000 basepair (bp) regions. Current Opinion in Psychiatry 2003, 16:157-170

In thcsc candidatc regions, additional markers are gcnotyped 1-? cM apart,which somerinlcsnarrou,s the candidatcregion.

DOI: 10. 1 097/01 .vco.000005861 7.61 505.a5 157 158 Schizophrenia

Table1. Stagesof positionalcloning studies

Stage Clinicalsamole Molecularstrategy Outcome

Genome scan Multiplyaffected pedigrees Genotype microsatelliteDNA markers Evidence for linkage in 1O-30 cM at 5000000-10000000 bo candidate region(s) (5-10 cM) spacing,or denser SNP markers Fine-mapping Multiply affected pedigrees Genotype microsatellitemarkers in Evidencefor linkagein 2-10 cM candidate regions aI 1-2 cM spacing candidate region(s) (or denser SNPs) LD mapping Cases versus controls or Genotype markers (primarilySNPs) at Evidence for associationof small sets case-parent trios 10000-50000 bp (10-50 kb) spacing of adjacent markers with disease, implicatingone or two specific genes 'knockout' Functionalgenomics Animalmodels (e.9. Physiologicalstudies to establishthe Plausibleevidence that the gene plays mice), cases, postmorlem tissue role of the gene and protein, effects of a role in disease susceptibility; mutationson physiologyand behavior, detection of other interactinggenes and response to treatmentsfor the and oroteins disease

LD, Linkagedisequilibrium; SNP, singlenucleotide polymorphism.

Linkagc disecluilibrium (LD) mapping is bascd on a New genome scans differcnt principlc: mosr of the gcnome's DNA Eight new scans and one partial scan \l/erc published scqucnce variations have arisen only oncc or a few this past ycar. Regarding the interpretation of scan 'unrclated' 'gcnome-wide times. Somc ill individuals may havc results, significance' usually refcrs to a inherited from a single ancient ancesror an identical result that is expected to occur by chancc once in 20 'suggcstive DNA scgment that incrcascs rhe risk of diseasc. Each scans, and significance' refers to a result paticnt's complcte DNA sequencc cannot yer be that would occur once per scan on average t261. scquenced cost-effectively, but one can study many However, for complex disorders, statistically significant variations (single-nuclcotide polymorphisms; SNPs) linkage is not reliably obscrved at feasiblc sample 10000-50000 bp (10-50 kb) apart in the candidatc sizes, and the pattern of results across studies may 'unrelate 'haplotypes' 'narrow' rcgion in d' cases ro look for prove to bc more important. In this discussion, (adjaccnt variations on rhe samc chromosome) that are diagnoses rcfcr generally to schizophrenia and schizo- 'broad' 'spectrum' more common in ill individuals. It is believed that affective disorder, and or diagnoses somc (not all) susceptibility variants underlying com- refer to schizophrenia-related psvchoscs and personality non complex disorders can be identified in this way disorders. with larger samples, improved SNP maps and cvolving molecular mcthods. Straub et o/. [1"] published scan results for 270 kish pedigrees. They prcviously reported evidence for Functional studies can rhen bc initiated to determinc linkage on chromosomc 6p2l-24, which approached thc genc's function, inrcractions and possiblc rclation- gcnome-wide significance dcpending on horv one ship to tl-rc disease. corrccts for multiplc tests [27], and suggesrive evidence on 5q21-31[28], Bp22-21t29] and 10p15-p11t301. Gencrally, two gcnome scan strategics have becn Resultssuggested at least two suscepribiliryloci on employed. One is to study srnall samples of familics chromosome6p, both of which have been supportedby with as many ill relatives as tr-rossiblc,in the hopc that other studies(see below), but peaks this closc rogerher one or a few genes are conferring rnost of the risk of are difficult to provc with currcnr methods. This diseasc [18",19"]. The other is to collect many farnilies relatively large samplc was drawn from one ethnic with at least an affccted sibling pair (ASP), assuming that population, which might improve the power to dctect multiple intcrzrcting gcnes each confer a small proportion linkage [31]. But the scanwas completcd someyears ago of risk [20], so that hundreds to thousands of families rvill using threc different, sparse (20-30 cN,,I) maps in bc nccded t?t1. Thc complexitics of this debate are subsamplesof 90 farnilics. A range of diagnostic and beyond thc scopc of this paper. Existing data abotrt genetic models werc analysedto cxplore rhe data fullv, fan-rilial pattcrns of schizophrenia tend to slrpporr rhe btrt this also makes thc findines more difficult ro second vicw [20]. Srnall samples tend to exaggcrarc rhe intcrprct. gcnetic cff-ectsof somc loci whilc missing orhcrs entirely [22,23]. Howevcr, somc of chc bettcr-su1-rportcdlinkzrge Delisi et a/. l2"l published rwo scans.The largest findings in schizophrenia wcre initially detectccl in srnall schizophreniascan to date was of 291 fan-rilies(333 samples124,251. indcpcnclcnt ASPs). Tu,o slrggesrive findings \\rcre Moleculargenetics of schizophreniaLevinson 159

obscrved, on chromosornes 10p and Z (centromcric reports (including some but not all of the above data) region),lr,ith more modest evidenceon 22q, The sccond reported P values < 0.001 in candidate regions of scanwas of 99 families from the Ccntral Vallcy region of clrrcrmosomes1q, Zcl, 8p, 13q and 22q 19"1. (A larger Costa Rica (62 ASPs by a narrow diagnosticn-rod el, l0Z meta-zrnalysisis being carried out by a collaborationof by a spectrllm modcl) [3"]. The maximum evidcnce for investigators and should be availablc soon.) Pou'er linkagc (falling short of the suggesrivclevel, as has been analysessuggest that replicable linkagc u'ould require thc casc for a number of scans) \\ras obsen,cd in multiple samplcs of 500-1000 ASPs or more. Tu,o chromosome5q34. samples of 500 and 900 ASPs are clrrrenrly being collected for thc National Institute of Mcntal Health Paunio et a/. f4"] analysedscan data for two subsarnples; (NIMH) ccll repository.A series of multicenrer colla- 163 Finnish gencralpopulation families (191 ASPs), and borationsin which samplesof 500-800 pedigreeswere 47 nuclearfamilies (60 ASPs)from an isolatedand inbred genotypcd produced evidence supporuinglinkagc on rcgion. This group had previously reported suggesrive chromosomes6p [35], 6q [36], 10p t36l and Bp [35], cvidence for linkage in two differcnt regions of distal althoughnot 1q 137'1,5q[36] or 13q [36].It is likely that chromosome1q, one in the nationaland the other in the that some or perhaps many of these candidateregions isolatc sample t321. Thc scan prodr-rcedsignificant contain schizophreniasusceptibility loci, cach contribut- findings on distal 2q (isolate sample) and on 5q31 ing to a small increascin population-widerisk (although (nationalsample). some loci could have larger effects in indir.idual familics). Gtrrling et a/. [5"] studied 13 British and Icelandic pedigrees.Suggestive linkage was observcdon chromo- Candidate genes in positional candidate regions somes 1q32.2, 5q33.2, BpZl-Z?, llqZ3.2-q24 and For the first time, LD mapping studies of positional ?0q12.t-11.23. czrndidateregions have implicated specific genes in schizophreniasusceptibility. Previously, no strong and Camp et a/. 16"] studied scvcn extendcd pedigrecs from replicablecandidate genes had emerged from studiesof thc isolatcd island nation of Palau. Significant linkage genes involved in antipsychoticdrug mechanisms(c.g. was obscrved on chromosomcs 2pl3-14 (as reported dopamine receptors) or in central nervous svsrem previously I33l) and 13q12*22,and suggcsrivelinkage processesthat could be hypotheticallyrelated to schizo- on SqZZ-cryer. phrenia. In the absence of evidence for linkage in a region, thc prior probability for the associationof a genc Garveret a/. 17'l studied 30 US pcdigrees.No suggesrive is so low that statisticalproof becomesexrremely difficult resultswere observed.The most positive scoreswere on t381. These new reports (Table 2) are therefore chromosomes1p, 5p, 20q and Bp. important new developmcnts. F'urther replication will be needed before the validity of these associationscan Lindholn'r et n/. [8"] studicd a set of pedigrees from be evaluated. northern Sweden (39 narrow and four broad cases)that wcre intcr-relatcd going back 1Z generations.Significant NRGl linkage was observcd on chromosome 6q25. A six- A genome scan in 33 Icelandic pedigrees with 105 marker haplotype segregatedwas observcd in most ill cases of schizophreniaproduced suggesriveevidence relatives.Additional peaks includcd chromosomes3p25, for linkage on chromosome 8p [10"], near where 20p11.2,6p24 and 8p21-22. suggestive linkage has been reported by others [18",19"]. LD mapping studiesin casesand controls Maziade et a/. [34"] reported a parrial scan (denser in suggestedthc associationof individual SNPs and SNP candidate regions) in 19 Quebecoise pedigrees with haplotypes in MGI (neuregulin-l, 8p21-pl2). The 'core' schizopl"rreniaor bipolar disordcr.Suggcstive linkage to haplotypc was observedin 15/% of 478 affected schizophreniawas observed on chromosomcs6pZ2-24 cascsand 7.5% of 394 controls,with P:0.000087 for and 18q. cascsnot known to be related.IVRGI is a glycoprorein with a variety of isoformsthat bind to the ErbB farnilv Although most scansto nor replicatceach other, therc is of tyrosine kinase transmembranereceprors. NRGI and in fact substantialconvergence in the rcsults acrossall ErbB4 l-reterozygousmutant mice demonstratedhvper- studies. Prcvious linkage findings have bccn reviewed activity that was rcduced by very lor,v doses of reccntly by Watcrwort et a/. fl8"] and Baron [19"], and clozapine, slightly dcficient pre-pulse inhibition, and r,r.ill not be thoroughly rcvicwed hcre, but there is a small reduction in functional I/-rnetl-rvl-D-aspartate support fion-r sevcral studics for (at least) regions of (NN,IDA) reccptors. Note that IVRGI lies 9-25 cN,I clrromosomcs1c1, 2c1, 5q, 6p, 6q, 8p, 10p, 13c1,15c1 zrnd towards the centromere from previously rcported 81-, 22q. t\ mcta-analysisof ptrblishedschizophrcnia linkage linkagc pcaks, and it is possiblerhar anothcr gene in 160 Schizophrenia

Table2. schizophreniacandidate genes in positionalcandidate regions

Gene(s) Location Study population(s) Comments Neuregulin (NRGl) 1 [10..] 8p12-21 lcelandic. Linkage: 33 pedigrees. NRGl lies outside the 8p region where Association:478 cases versus positive linkage evidence has been 394 controls reported, and might not explainthose repons. Dysbindin(DTNBPT) [11..] 6p22 lrish. Linkage: 27O pedigrees. The gene product is part of the dystro- Association:same (family-based phin protein complex involvedin muscu- method) lar dystrophy,but may also be involvedin signal transduction and receptor gene expression. Proline dehydrogenase 22q11 107 US triads (adultschizophrenia); Association was observed in early-onset (PRODH2) 29 US childhood schizophreniatriads; cases. Sample sizes were small and P .'|09 75 Afrikaner cases and controls valueswere modest (= 0.001), but positive evidence was observed in three samoles. G72 (o-amino acid oxidase; 13q34(12q2a) 213 FrenchCanadian cases and G72 was identifiedthrough LD mapping DAAO) [13.{ 241 controls;183 Russiancases and of linkage regions from other reports. 183 controls Yeast two-hybrid experimentsidentified DAAO as interactingwith G72; modest association was observed for DAAO. Catechol-O-methyltransferase 22q11 Ashkenazi.Association : 7 14-7 24 cases COMT is in (coMl) the VCFS deletion region. 114--l and 2849-4899 controls It degrades catecholaminesincluding dooamine.

LD, Linkagedisequilibrium; VCFS, velo-cardiofacial svndrome.

tlrat rcgion, rarher than a variation in IVRG/, will provc linkage was reported in rwo samples [25,431. Strong to cxplain thosc findings. associationwas observed in one French Canadian samplc between schizophrenia and SNPs in a novel genc, G7Z, DINBPl with weaker associarion in a Russian samplc. Yeast two- Straub el o/. [11"] reported the association of schizo- hybrid expcriments and subscquent studies demon- phrcnia to SNPs and SNP haplotypes on chromosome strated that G72 acrivares D-amino acid oxidase (DAAO, 6;t22.3, implicating thc DTMPI (dysbindin) gcne, in 12q24), an enzyme that oxidizcs D-serine, an acrivaror of the linkage region from their and orhers' genome scans NN4DA receptors. Weak association was observcd [18",19",?,71. Dysbindin binds to dystrobrevin, part of between schizophrenia and DAAO. the protcin complex involved in the pathogenesis of muscular dystrophy. Thesc proteins have diverse func- COMT tions rclated ro ncurotransmitter signal transduction. Catechol-O-methyltransferase(COMT, 22q|LZ1, in the Evidence suppoming this association has recently been VCFS region) is one of the major degradative parh- rcported in two German samplcs [39]. ways for catecholamincs including dopamine. Associa- tion with schizophrenia has been inconsistent for a PRODH2 Val/Met polymorphism [18"], with several recenr Individuals rvith velo-cardio ftrcial syndrome (VCFS) are additional ncgativc reporrs 144'46',47,48.1, although at a strbstantially increascd risk of schizophrenia l401Zl, two of the studies reported modest associations for so that the idcntification of the relevant gcnes in thc symptom severity 144'l or age ar onser 146.1. 221111microdelction region is an important task. Liu r/ Recently, Shifman et a/. [14"] screcned new COIIT a/. llz"l rcportcd the association of schizophrenia to SNPs with pooled genotyping in morc than 700 (proline SNPs in PRODHZ dehydrogenase, ZZctll.Zl), Ashkenazi Jewish cases and 3000-5000 controls, rvith particularly in childhood cases and in aclults with agc at individual genotyping confirming srrong associations onsct bclow thc age of 18 yeirrs. Eviclence for association for trvo SNPs (P:0.00016-0.00003). Weinberger et o/. was modest, but was obscrved in three scparate small [49'] proposed that CO,+IT scqlrence variation modifics san'rplcs. Proline dehydrogcnase is a mitochrondrial cognition through cffects on dopaminergic transmission cnzymc involvcd in transferring reclox porential across in prefrontal cortex. the mitochondrial membranc. Such reports usher in a new era in schizophrenia G72 and DAAO gene tics. One might cxpecr more such repofts ro Chrrmakov et n/. [13"] initiated LD rnapping stuciiesof Llppear ovcr the next 3-5 years, u,ith increasingly large chromosome 13q34 in thc region lvherc significant samplcs supporting thc association of schizophreniir Moleculargenetics of schizophreniaLevinson 161 rvith plausible candidate gcnes in linkage candidate Genes related to serotonergic neurotransmission regions, or gencs idcntified by large-scaleexprcssion A rnodest but significant associationbcru'een schizo- studies. Initial rcports may bc difficult ro interprct: phrcnia and a polymorphism in the serotonin-2A many tests musr be performcd on SNPs and haplo- receptor gene (HTRZA, l3ql4-q21) rvas reported in a types, and there is no definitive threshold for ^ large multicenter analysis t57) and a mera-analvsis significant finding. Data rnining tcchniques arc evol- [18",19",58]. Therc are two new negarive reports ving in this field, and rcplication is likely to be the [59,60].Association had been reported in Han Chincse corncrstone of data intcrpretation. Thc allthor u,ould individuals for the serotonin transporucrgene (SLC6A, prcdict that, despite these difficulties, the pattcrn of formerly 1HTT, 17qll.l-q12) [61], and a very modest rcplication studies and physiological findings will replication (P :0.043) was rcported in the san-re ultimately become clear and convincing for ar lcast population 162'1.Negative studies of 5HTRI B (6c113) some of thc new candidate gcnes. Throtrgh this t63l and 1HTR3A (llq23.l-c123.2) 164l have been process,the first real clues ro rhe parhophysiologyof published. schizophreniaare likely ro cmcrgc. Genes related to glutamatergic neurotransmission Other studies of candidate regions and genes A numbcr of lines of cvidence have suggesteda role for Othcr notcworthy reports include applicationsof micro- glutamatergicdysfunction in the pathogenesisor phar- array technology and studies of candidate gencs in macology of schizophrenia[65']. A modest association pharmacological ly-relevant ncurotrans rni tter systems and (P:0.0105) was rcported betwcen schizophreniaand in positionalcandidate regions. GRIK3 (ionotropicglutamate receprorkainate 3, 1p34- 33) in 99 casesand 116controls [66']; and an association Probing the genome with microarrays (P:0.0022) was reported for GR,M,I (metabatropic Severalsttrdies demonstrated the emerging porcntial of glutamatereceptor 3, 7q7l.l-qZl.Z) in 265 casesand microarraymethods to probe the genome or protcome ZZ7 controls, which could not be replicated in an for candidate pathways. The decrcasedexpression of additional 2BB cases or 128 trios [67'l.Negative RGSI (regulatorof G-protein signalling4, lqZl-q?D had association results were reportcd for GR'M4 (meta- been observed in a complemenrary DNA microarray botropic glutamate receptor 4, 6p21.?) [68'], GRIKI study of brains from schizophreniaand control indivi- (ionotropic glutamate rcceptor kainate 1, 21q22.11) duals [15']. SNPs were idcntified in the region, zrnd [69'] and GkM2 (metabotropic glutamate recepror Z, haplotype analysis revcalcd four SNPs with a modest 3ptZ-p11) [70']. associationto schizophrcniain two indcpendenr samples,with a trend in a rhird sample117").The gene is Chromosome 1q located in a linkage candidate region 15",241. In a Significantlinkage was rcported on chromosome1q21- 'Celtic' second study, Hemby et a/. [16"] probed 1B000 q22 (ry 158MB from pter on chromosome1) in a messengcr RNAs in case and control brains and Canadian sample lZ+1, and suggestive linkage was demonstrated significant differences in the expression reported on lclZl-qZ3 (1165 MB) in Icelandic and for a numbcr of genes.A further exampleis discussedfor British pedigrees[5"], on lq41-q42 (x208 MB) in chromosome 22q (below). farniliesfrom a genericisolate in Finland f5",321,and on 1q42.1 (x230 MB) in a Finnish general population Genes related to dopaminergic neurotransmission affected sib-pair sample [5",321. The latter region Schizophrcnia has nor been convincingly associated contains the breakpoint of a balanced (1;11) (q42.I: with polymorphisms in genes rclated to doptrminergic q14.3) translocation linked to psychotic and mood function, although meta-analyseshave suggesteda small disorders in an extended Scottish pedigree, rvith but significant associationfor homozygosityat a ;roly- maximum lod scoresof 3.6 for schizophrenia,4.5 for morplrism in DRD3 (3q13.3)[50]. Therc are rwo rcccnr mood disordersand 7.1 for both [71]. The DISCI and reportsof slightly positive evidencc for an associationat DISCZgenes are disrupted by this breakpoint[72"], but DRDZ (I1c122-q23)lnl',52'1, and one repon [53'] was no variationassociated with schizophreniahas ver bccn negative. Therc was a rcport of thc association found in these gcnes 173'1. The genes in thc llq (P = 0.0001-0.05) betwccn measures of eye-tracking breakpoint region have also been identified [74']. dysftrnctionin schizophreniapatients and DRD3 [54'], Linkage was not supported in a multicenter samplc clf as well as a negative study of DRD-I homozygosityand 779 pedigreesusing a 5 cNt[ markcr map of lq2l-q42 of several new polymorphisms in alternarivc promoter [37'1, or in 1q21-(PZ in extended French Canadian and 5'untranslatedregions (tiTl{s) in the gene [55']. A pedigrces[75']. There have been mixed reporusregard- furthcr report fonnd a moclest associationbcnvecn ing thc associationwith thc CAG repear polvrnorpl'risn-r schizophreniaand two markersin or near DIIDS (ap16) in KCI{AB (lqZI.Z) [18"]. A new Japanesestudy u'as [5(r']. ncgative [76'l; but in Israelis, longer alleles wcrc 162 Schizophrenia itssociated with morc severe negarive and parzrnoid cvidcnce fbr linkage h:rs been modest, a mcta-analysis symptonts [77']. suggcsted significant linkagc [9"]. Evidencc for PRODHZ and COMT \vas discussed above. VCFS Chromosome 6 clclctionswere again found to be rare in schizophrenia N,{oclest irssociation was reportcd for SNPs in TIYFZA - one in 300 Japanesecases [99']. For genes in the (tumor nccrosis factor irlpha,6p21.1-21.3) [78']. A highly dclction region, moclest evidence for association\\/as significzrnt associzrtion had bccn reported in NOTCH4 observcd for two polymorphisms in promoter regions, (6p21.3) in a srnall sample 1791,but there havc been including UFDIL (ubiquitin fusion dcgradation 1-likc) many non-replicarions [80,81,82',83',84]. A suggcstive in two small sarnples[100'], andSNAP29 (synaptosomal- linkage was reportcd in tl-re acljaccnr HLA rcgion associatedprotcin, 29000 M,) [101']; and for SNPs in (6p2l.Z) [85']. I-Iowever, although an imn"runological ZA|F74 (zinc finger protein 74) ro agc-at-onserbur nor role in the pathogenesis of schizophrenia is plausible schizophrcniain 300 Japancsccases and 300 controls [18",19"], no associ:rtionrvas observed in recent reports ll0z'1. The latter agc-rlt-onsetfinding was replicatedin on class I allelcs in Japanesecases and controls [86'], in another 769 cascs |02'| Children with VCFS had class II DRlll, DOAI, DOII| and DPBI allclcs in Han sin-rilarbchavioral and psychiatricdisorders to childrcn Cl-rinesc trios [87'], or in DOB 1, DRB t, DgAl, or HLA-A matchcd for the level of cognitive function, lcading the alleles or haplorypcs in primarily European sib-pair authorsto doubt the specificrclationship betwccn VCFS fanrilies and trios [85']. Reports on DTNBPI and on (rc1 and schizophrcnia[103'], but this conclusionignorcs the linkage have bccn discussed above. 20Vo prevalencc of schizophrenia svmptoms among adults u,ith VCFS t411.Outsidc the deletion region, Chromosome 8p Ntleyer et a/. [104'] described a purarive porassium No association with schizophrcnia was obscrved for channef gcne, WKLI (AF319633_1, 22q73.33), and markers in three plausible candidate gencs (PIVOC, reported that a missense muration in this gene co- CHRAIAZ and lVAZ1) [U8'] in the 8p2l-22linkage rcgion segregatedwith pcriodic catatonia in one extended discussed above. pedigree.Three groups failed to find the mutation or associationto other SNPs in the region in schizophrenia Chromosome 15q samples[105',106',107]. In periodiccararonia, an asso- Frcedman and collcaglres [89] dcmonstrated the highly ciation was not observedfor CELSRI (cadherinEGF (7 significant linkage of chromosomc 15q13-q14 to defi- cpidermal growth factor-like repeats)LAG (2 laminin cicnt inhibition of thc P50 auditory evoked porential AG-type repeats)seven-pass G-type recepror1,22q1.3.3) (pre-pulse inhibition) in schizophrenia probands and [108']. Finally, Mimrnack el o/. [109'] carried our a thcir affccted and unaffected rclatives, and showed that cDNA microarray-basedgcne expression analysis of tlrc alpha-7 nicotinic receptor gcne (CHRArATl was schizophreniaand control brains from ru.o collections, involved in this deficit in animals and was a plausible and in both they found an increased expression of candidate genc for schizophrenia t90-921. Howcver, APOL|, APOLZ and APOL4 (apolipoproteins7,2 and 4, evidence for linkage ro schizophrenia in this region all in 22qlZ outside the VCFS deletion region).Tl'rese had becn modest. Now, a re-analysis of the NIMH findings suggcst a possible pathway in schizophrcnia Schizophrcnia Gcnetics Initiative genome scan using a pathclgenesis. dominant paramctric lod scorc analysis produced significant evidcnce for linkage on 15q13-q14 [93"]. Other candidate genes Suggestive evidence for linkage was also reportcd near A role in schizophrenia has been hypothesized for 'I'aiwancsc CHRMZ in families f94'1, with more modest cholecystokinin (CCK, (3p22-p21,.3),which modulates support in two Amcrican samplcs [95',96']. An associa- dopaminergicneurotransmission [110']. Recenr rcporrs tion was also observecl (P: 0.0004) bcnveen mtrrkcrs ar include slightly positive evidence for the associationof CHIIATAT and schizophrcnia in 31 pedigrees frorn the scl-rizophreniawith a polymorphism in the promorer Azorcs 197'1, but not in pedigrccs with thc periodic rcgionin US cases[111'] and u,ith polyrnorphismsin the catatonia phenotype, which had shown linkage to this promotcr region of the CCK-A recepror genc (CCKAR, rcgion [98']. On thc basis of thcsc resulrs, 15q13-q14 4p15.1pf5.2) in Japanesecascs and controls[110'], but cmergcs as a strongcr schizotr-rhrcniacandidatc rcgion. not to a microsatcllite in the CCK-II rccepror gcne (CCKIlll, 11p15.4-p15.1)in Japanesecases and controls Chromosome 22q lll2l. An association(P:0.031-0.0001) u'as reportcd Microdclctions of 22c111.21(VCFS) rcpresenr rhc only betu'ccn schizophrcniaand threc SNPs in myo-inositol cytogcnctic abnormality that is clcarly associatcclrvith a monophospl'ratasc2 (IIIPAZ, 18p11.2),in 302 Japanese substantial risk of chronic schizophrenia, suggestir-rgthart schizophrcniacerses vcrsus 308 controlsand 205 affective onc or more gcnes in this rcgion could play a role in disordcrcases [113']. Ntlodestevidcnce for associilrion schizophrcnia in the abscncc of dclctions. Although was reportcd for a SNP in CTL|I-1 (c_vtotoric T- Moleculargenetics of schizophreniaLevinson 163

lymphocytc anrigen-4,2q33) in 116 Korean casesand Clinicaldimensions 'first-rank' 149 controls (P:0.003), as a result of fcwer hctero- Cardno et a/. [I44'] showed that symprorns zygotesin the cascs[114']. Sirnilarly,268 lapancsecascs (such as dclusionsof bcing controlled or hcaring voices showed increased homozygosity at linked SNPs in conversing)u'ere heritable in the Maudsley tlvin series, GRIATZB(rhe Ar,4,lDA-28recepror, l?plZ) versus 337 but lcss so than the category of schizophrenia.Thev controls(P:0.004) [115']. Nlaeset a/. [116'] revieu'ed also rcported that generic liability ro schizophrenic, cvidence for alterationsin thc acutc phaseinflammzrrory manic and depressivc symproms appeared ro ovcrlap responscin schizclplrrcnia,and reportcd an associationof substantially when rated non-hierarchicallv [145']. polymorphicvariation in haptoglobin(HP, I6q22.1)and Kendler U46'1, in a commentary on rhe latter study, haptoglobin plasma levcls in 98 Italian cases versus suggested that the data are better interpreted as establisheddistributions in the localpopulation. Finally, showing that manic and depressive syndromes are Hong et a/. l1l7'l observed a modcst association somewhat heritablc in individuals rvith schizophrenia, betu,een schizophrenia and TPH (tryptophan h1'droxy- because no genetic overlap was shown between lasc, 11p14-p15.3)in 196 I{an Chinesc casesand 251 individuals with primary diagnoses of schizophrenic controls. and rnood disorders.

Additional ncgative associationstudics of candidatc Models for genetic studies of schizophrenia genes publishcd during the rcview pcriod will not bc Several intriguing models have been proposed for discussedin detailhere [118-136]. conccptualizing gcnetic factors in schizophrenia.

Progress in identifying quantitative traits for Advancing paternal age and de-novo mutations genetic studies A re-analysisof data from a birth cohort study demon- Therc werc sevcral reporrsabout schizophrcnia-relatcd strated that advancingpaternal age slightly but signifi- quantitativetraits that showedpromisc as phenotypes for cantly increasedthc risk of schizophrenia,after adjusring geneticstudies. for possible confounding factors such as maternal age U47"1. In anotherstudy [148'], schizophreniapatients Neuropsycholog ical measures without a known family history of schizophreniahad In 264 casesand rclativcs from a geographicalisolate in significantly older fathcrs than those with a family Finland, measuresof working memory showed srrong history. Malaspina [I49'] integrated these and othcr hcritability, possibly becausc of a small number of data into an intriguing hypothesisthat de-novogermline contributing loci U37'). Measures of memory and IQ mutations can increasethe risk of schizophrenia,which declined before the onser of psychosis in high-risk suggeststhat novel stratcgiesmay be needed to identifv individuals in thc Edinburgh high-risk project [138]. these mutations ll49'1. However, in the same project, attenrional dysfunction did not differentiare rhe relativesof schizophrenicversus Neurodevelopmental hypotheses control subjects[139']. l.ewis and Levitt [150"] reviewed the evidence for a neurodevelopmental hypothesis of schizophrenia, Neuro-imaging measures suggesting a polygenic-multifactorialmodel whereby In a crcative analysis from thc Edinburgh project, a genctic predisposition alters development, gene- reduced volume of the amygdalohippocampalcomplex environment interactions influence or trigger gencric 'obligate was observedin carriers'(well individualswith cffects, and cumulative effects of altered dcvelopment a schizophrcnicsibling and offspring) [140']. In a study lead to a relatively stable and treacment-resistanrstate. of monozygotic and dizygotic twins discordant for Maynard eta/. 1151']proposed a two-hit model requiring schizophrcniaand control rwins, an Llpwardbowing of genctic or early environmentalpredisposing factors plus thc corpuscallosum was alsosuggested to be a markcr of triggcring factorscloser to onser. Schiffman et a/. [152"] vulncrability[141']. reported that among 93 high-risk offspring,the number of physical anomalies at age 11-13 years predicted Neurologicalsigns schizophreniaspectrum disorders at age 31-33 vears. Ncurological signs wcrc increascd in thc relatives of Therc were high rates of anomaliesand of spectrum schizophrcniapatienrs, bur the low rclative risk versus disordersin the samplcs.Bassett and colleagues[153'] controls suggestcd rhat thcy might bc poor gcnetic rcviewed evidcnce for ncurodevelopmentalhypothcses, markcrs [142'). A pattern of dysmorphic featurcs was focusing on physical anomaliesand the implicationsof found to diffcrenriare a subgroup of 1B schizophrcnia syndromessuch as VCFS. DeLisi [154'] suggestedtl-rat cirscs from othcr clusrcrs in a sample of 123 clinical schizophrcnic patients have language clisordersthat schizophreniacascs and 36 cascs referred for possible could be related to genes underlying the uniquelv vcFS [143]. human characteristicsof spccch. 164 Schizophrenia

Conclusion studics (and perhaps in thc future, microarray studies) in The pacc of discovery is accelerating in the ficld of a critical \\'Lry- cognizant of me thodological shortcornings schizophrenia genetics. The mosr striking dcvelopments and realistic about the strcngth of results and the po\\rer in thc past year have included the zrpparenrconvcrgcnce of samples it should bc possible to move from of new and older linkage data on zr number of canclidate regions to candidate genes to thc beginnings chromosomal rcgions, zrnd the first reporrs of LI) of an undcrstanding of schizophrcnia pathophysiolog_yin rnapping data slrpporring s;recific candidatc gcnes in the ncxt decade. linkagc candidatc regions. A|RGl, DT'ArBP1, GT2IDAAO and COMZ r.vere all studied in 400 or ntore cases, rnore than in most previons candidate gene studies. Hou,evcr, Referencesand recommended reading inadcquatc powcr remains a problem in both linkagc and Papers o{ particularinterest, published within the annual period of review, nave been highlightedas: LD mapping studies: ideally, it would be prcfcrable to ' of special interest " have scveral linkagc samprlesof 500-1000 pedigrees and of outstanding interest sever:rl association samplcs of 1000-3000 cases and controls or probancl-parent trios. Associartion data fron-r 1 Straub RE, Maclean CJ, Ma Y, et a/. Genome-wide scans of three " independentsets of 90 lrish multiplexschizophrenia families and follow-up of very small samples remain difficLrlt to interpret. selected regions in all families provides evidence for multiple susceptibility genes. Mol Psychiatry 2OO2; 7 :542-559. Genome scan resultsare reported for 27O lrish pedigrees.The scan was initiated The next fcw years are likcly ro see thc completion of and mostly completed when genotypingthis large sample was considerablymore the haplotypc strucrure map ('HapMap') and a rapid expensive.lt was thus divided into three subsets, each of which was scanned using a different 2O-30 cM map, and positive regions as well as candidate regions decline in thc cosr of vcry high-throughput SNP reported by others were typed in all subsets. Multiplediagnostic and transmission genotyping. Thc HapMap project will identify a minimal models were tested. Results on chromosome 6p21-24 approached genome-wide significance,with a suggestion oJ at least two loci in the region, and suggestive set of approximately 100 000-500 000 SNPs, which evidence for linkage was observed on 5q21-31 , 8p22-21 and 10p15-p11. definc local 10-50 000 bp blocks of LD, i.e. the old, 2 Delisi LE, Shaw SH, Crow TJ, et al. A genome-wide scan for linkage to corrurron variation in thc human gcnome [155-158]. The " chromosomal regions in 382 sibling pairs with schizophreniaor schizoaffec- hypothesis to be testcd is thac at least somc of the tive disorder.Am J PsychiaIry2QO2;159:803-812. This is the largest genome scan published to date, including 294 {amilies of predisposing DNA sequencc variations for common predominantly European ancestry with 333 independent ASPs. Suggestive complcx disorders may be in LD lvith thcse blocks. evidence for linkage was observed on chromosome 10p15-p13 and around the centromere of chromsome 2, with a smaller peak on chromosome 22o12. However, therc may be roo many diffcrcnt predisposing variations in diffcrcnt popularions, with little correlation 3 Delisi LE, Mesen A, Rodriguez C, et al. Genome-wide scan for linkage to " schizophreniain a Spanish-origincohort from Costa Rica. Am J Med Genet betwcen thc obscrvable phcnotype and underlying 2OO2; 114:497-508. gcnotypc t1591. It is likcly rhat cost-efficienr mcrhods Genome scan data are reported for 99 families from the Central Valley region of Costa Rica (62-102 ASPs depending on the model). Modest evidencefor linkage will be dcvelopcd to detcct all sequence variations in was observed in chromosome 5q34. candidate rcgions [160], so rhar one might also detect an 4 PaunioT, EkelundJ, VariloT, et al.Genome-wide scan in a nationwidestudy cxcess of rare variations in cases. Diverse microarray " sample of schizophrenia families in Finland reveals susceptibility loci on strategies offcr additional tools to identify functionally chromosomes 2q and 5q. Hum Mol Genet 2001; 1O:3037-3048. Two genome scans are reported,one of 163 families(191 ASPs) from the general relevant gcnes, proteins and parhways, and although Finnish population,and one of 47 nuclearfamilies (approximately60 ASPs) from thesc will not always be causal [159], they are likely to an isolated,inbred region. Resultsfor chromosome 1q are reported in Ref. [32]. Significantfindings were observed on very distal 2q (isolate sample) and 5q31 yield insights for trcatment and ultimately fcrr better (nationalsample). causal hypothcses. 5 Gurling HM, Kalsi G, Brynjolfson J, et a/. Genomewide genetic linkage " analysis confirms the presence of susceptibility loci for schizophrenta, on An articlc by a social scientist suggested some conclud- chromosomes 1q32.2, 5q33.2, and 8p21-22 and provides support for linkageto schizophrenia,on chromosomes 11q23.3-24 and 20ql2.1-11.23. ing reflections: Conrad [161'] critiqued the widesprcad Am J Hum Genet 2001; 68:661-673. 'genetic 'which mcdia cndorsement of optimism', Agenome scan is reporled for 13 British and lcelandic pedigrees (56 cases with schizophreniaspectrum psychoses and 12 with broader diagnoses). Suggestive emphasizcs the inevitability of discovering genes and evidence for linkage was observed on chromosomes 1q32.2, 5q33.2, 8p21-22, thc good outcomcs of those discoveries, whilc negarive 11 q23.2-q24 and 20ql 2.1-1 1.23. or retracted findings reccivc no attenrion. Scientific 6 Camp NJ, Neuhausen SL, Tiobech J, et al. Genomewide multipointlinkage " collcagues in genctics and othcr fields arc prone to analysis of seven extended Palauan pedigrees with schizophrenia, by a Markov-chainMonte Carlo method.Am J Hum Genet 2001;69:1278-1289. similar distortions' (p. 225). However, optimism is far This is a repod on a genome scan of seven pedigrees from Palau (an old but genetically isolated population with an elevated - 2o/o lifetime prevalence - of from the dominanr rheme in thc scicntific community. 'spectrum' schizophrenia),with 40 narrowly defined and 45 cases available.A Rather, wc sec an unfbrtunarc oscillation: scientists as 10 cM map was genotyped and linkageanalyses performed using Markov chain r,vell trs the media tcncl to make exaggeratedly positive Monte Carlo methods to reconstruct haplotypes followed by Non-Parametric 'ncgative Linkage (NPL) and paramelric lod score analyses. claims, and then thc and rctractecl findings' havc lcd to profound skepticisrn. What is necdccl is a 7 Garver DL, Holcomb J, Mapua FM, et al. Schizophreniaspectrum disorders: ' an autosomal-wide scan in multlplex pedigrees. Schizophr Res 2001; b:rlanccd ancl stcady approach for the long haul. In this 52:145-1 60. author's vierv, the corncrstonc of progress shotrlcl be thc A genome scan was per{ormed on 30 US European and African-American pedigrees with 62 schizophreniacases, 35 other psychoses and 23 spectrum logic of positional cloning: b_vutilizing data frorn linkage personalitydisorders, using a 10 cM map and NPL analysis. Molecular genetics of schizophreniaLevinson 165

8 Lindholm E, Ekholm B, Shaw S, et a/. A schizophrenia-susceptibilitylocus at 15 Mirnics K, Middleton FA, Stanwood GD, et a/. Disease-specificchanges in " ' 6q25, in one of the world's largest reported pedigrees. Am J Hum Genet regulator of G-protein signaling 4 (RGS4) expressionin schizophrenia.Mol 2001;69:96-105. Psychiatry2001 ; 6:293-301. This is one of the most significantfindings in schizophrenialinkage research, in Using cDNA microarrays,the authors demonstratedthat in brains of schizophrenia 6q25.2 in a large multigenerationalpedigree (actuallyan inter-relatedset of such subjects, expression was consistently decreased for RGS4 (regulator of G-protein pedigrees) from northernsweden. The relationshipswithin this family go back 12 signalling ,1q21-q22), and not for other RGS genes or for 70 other genes in this generations, presenting a challenge for linkage analysis, and analyses with cytogenetic region. This is one of the first sophisticated microarray studies of alternative allele frequencies produced somewhat different P values. This is one of schizophrenia,and it is likelythat these studies will yield imporlantinformation that the few examples of highly significant results from the study of this type of rare will inform genetic studres. pedigree. The linkage region is slightlydistal to that reported by other groups. 16 Hemby SE, Ginsberg SD, Brunk B, ef a/. Gene expression profile for " schizophrenia: discrete neuron transcription patterns in the entorhinal cortex. 9 Badner JA, Gershon ES. Meta-analysisof whole-genome linkage scans of Arch Gen Psychiatry2002; 59:631-640. " bipolar disorder and schizophrenia.Mol Psychiatry2OO2;7:4e5-411. In one of the first applications of sophisticated microarray technologies to A meta-analysiswas carried out on published schizophreniaand bipolar linkage schizophrenia, these authors constructed an array of 18 000 mRNAs and studied data, using a novel method for combining P values for broad regions of linkage. expression in EC-ll stellate neurons from brains from eight schizophreniacases For schizophrenia,P values of less than 0.001 across studies were observed on (older patientswith chronic illness,four on no medication)and nine controls. The chromosomes 1q, 2q, 8p, 13q and 22q. most prominent differences observed in a secondary more specific analysis were the decreased expressionof GRINl (NMDA receptor 1, 9q34,3), GNAIl [guanine nucleotide binding protein (G-protein) alpha inhibiting activity polypeptide 1, 10 Stefansson H, Sigurdsson E, SteinthorsdottirV, et at. Neuregulin 1 and (synaptophysin, " 7q211, SYP Xp1 1.23-p1 1.22), SNAP23 (synaptosomat-asso- susceptibilityto schizophrenia.Am J Hum Genet 2OO2;21.B7Z-8g2. ciated protein 23, 15q14) and SNAP21 Qapl2-p11.2), and the increased ln 33 lcelandic families with 105 available individuals with schizophrenia, expressionof GNG2 (G-protein gamma subunit 2, 14q21). suggestive evidence for linkage was observed on 8pi2-21 . fhe region was densely mapped in 478 schizophrenia cases and 394 controls, and evidence for 17 Chowdari KV, Mirnics K, Semwal P, et al. Associationand linkage analyses " association was observed within NRGI (neuregulin1) (P=0.000062 for a core of RGS4 polymorphismsin schizophrenia.Hum Mol Genet 20Q2; 11:1373- haplotypein one of many tests). The finding is 8-10 cM centromericto numerous 1380. other reports of 8p linkage, raising a question about whether this gene can explain Mirnics etal. [15'] had demonstratedthe reduced expressionof RGS4 (1q23.1, that previous evidence. Hemizygous knockout mice were produced and exhibited regulator of G-protein signalling 4) in brains from schizophrenia subjects in an modest evidence of deficient pre-pulse inhibition of startle and for a reduction in elegant series of microarray studies. In this report, SNPs were identified in the NMDA receptors. This thus becomes an important candidate gene for region, and haplotype analysis revealed four SNPs with a modest association with schizophrenia. schizophreniain two independent samples with a trend in a third sample.

18 Waterwort DM, Bassett AS, Brzustowicz LM. Recent advances in the " genetics 11 Straub RE, Jiang Y, Maclean CJ, et al.Genetic variationin the 6p22.3 gene of schizophrenia.Cell Mol Life Sci 2002; 59:331-348. " An excellent review DTNBP1, the human ortholog of the mouse dysbindin gene, is associated of schizophreniadiagnosis, epidemiology,and linkage and associationfindings. with schizophrenia. [Erratum appears in Am J Hum Genet 2OO2;72:lOOZl. Am J Hum Genet 2002; 71:337-348. 19 Baron M. Genetics of schizophreniaand the new millennium:progress ano ln a candidate region (6p22) supported by several studies in diverse populations, " pitfalls.Am J Hum Genet 2001; 68:299-312. these authors describe evidence for the association of schizophrenia with An excellentreview of schizophrenialinkage and associationfindings, focusing on DINBP1, dystrobrevin binding protein 1 or dysbindin, based on family-based methodological issues. The author argues for the use o{ larger pedigrees and association analyses of SNPs genotyped in a multiplexlrish sample in which 6p model-based linkage analyses, but carefully reviews findings from all study linkage was first described. Although dysbindin is part of the protein comprex designs. related to muscular dystrophy, these authors summarize evidence that it may play a 20 Risch N. Linkage strategies for genetically complex role in signal transductionincluding in the NMDA and i'-aminobutyricacid systems. diseases, with special This locus will receive intensive study in schizophreniasamples in the coming referenceto psychiatricdisorders. Gene Epidemiol 1990; 7:3-16. years. 21 Hauser ER, Boehnke M, Guo SW, Risch N. Affected sib-pair interval mapping and exclusion for complex genetic traits: sampling considerations. Genet Epidemiol1996; 13:11 7-138. 12 Liu H, Heath SC, Sobin C, et al. Genetic variationat the 22q l 1 pRODH2l " DGCR6 locus presents an unusual pattern and increases susceptibility to 22 Suarez BK, Hampe CL, van Eerdewegh PV. Problems of replicatinglinkage schizophrenia.Proc Natl Acad Sci U S A 2002; 99:3717-3722. claims in psychiatry. In: Gershon ES and Cloninger CR, editors. Genetic This group has been studying possible 22q candidate genes for some time. Here approaches to mental disorders. Washington, DC: American Psychiatric they present their most compelling evidence to date: several SNPs in the PRODH2 Press; 1994. pp.23-46. (proline dehydrogenase) gene, in the VCFS deletion region, show association with 23 Goring HH, Terwilliger Blangero schizophrenia in three samples: adult schizophreniapatients, childhood schizo- JD, J. Large upward bias in estimation of locus-specific genomewide phrenic patients, and an adult replication sample from South Africa (Afrikaners). effects from scans. Am J Hum Genet 2001; 69:1357-1 369. The association was observed for individuals with early age at onset. P values were (P= modest O.OO1for the strongest associations). The estimated relative risk 24 Brzustowicz LM, Hodgkinson KA, Chow EW, et al. Location of a major for the most strongly associated haplotypes were in the range of 3-5. The susceptibility locus for familial schizophrenia on chromosome 1q21-q22. evidence here is not definitive but this is an important hypothesis that will be Science 2000; 288:678-682. carefullystudied in the field. 25 Blouin JL, Dombroski BA, Nath SK, et a/. Schizophreniasusceptibility loci on chromosomes13q32,8p21. Nat Genet 1998; 2Q:7O-73. 13 Chumakov l, Blumenfeld M, Guerassimenko O, et al. Genetic and " 26 Lander E, Kruglyak L. Genetic dissection of complex traits: guidelines for physiological data implicating the new human gene G72 and the gene for interpretingand reporting linkage results. Nat Genet 1995; 11:241-247. d-amino acid oxidase in schizophrenia. Proc Natl Acad Sci U S A 2OO2; 99:13675-1 3680. 27 Straub RE, Maclean CJ, O'Neill FA, et a/. A potentialvulnerability locus for LD mapping studies on chromosome 13q34 were initiatedbecause of previous schizophrenia on chromosome 6p24*22: evidence for genetic heterogeneity. repods of significant linkage. SNP haplotypes in a novel gene, GZ2, were found to Nat Genet 1995; 11:287-293. be associated with schizophrenia in 213 French Canadian cases and 24 1 28 Straub RE, MacLean CJ, O'Neill FA, possible controls, with a modest replicationin 183 Russiancases and 183 controls. Yeast et a/. Support for a schizophrenia vulnerability two-hybrid experiments led to the identificationof o-amino acid oxidase (DAA?, locus in region 5q22-31 in lrish families. Mol Psychiatry1997; 2:148-155. 12q2 ) interacting with G72, and a modest associationwith schizophreniawas demonstrated for SNPs at DAAO. Physiological studies supported the 29 Kendler KS, Maclean CJ, O'Neill FA, et al. Evidence for a schizophrenia plausibilityof these genes as schizophreniacandidate genes. vulnerabilitylocus on chromosome 8p in the lrish Study of High-Density SchizophreniaFamilies. Am J Psychiatry 1996; 153:1534-1540. '14 Shifman S, Bronstein M, Sternfeld M, et a/. A highly significantassociation 30 Straub RE, Maclean CJ, Martin RB, et al. A schizophrenialocus may be " between a COMT haplotype and schizophrenia.Am J Hum Genet 2002; locatedin region 10p15-p11. Am J Med Genet 1998; 81:296-301. 7 1:1296-13O2. 31 Altmuller J, Palmer LJ, Fischer G, et al. Genomewide scans of complex New SNPs were identified within COMT (22q11), a gene in the VCFS deletion human diseases:true linkageis hard to find. Am J Hum Genet 2001; 69:936- region, and tested with pooled genotyping in approximately700 Ashkenazi cases 950. and 3000-5000 controls. Positive results were followed up with individual genotyping, and a strong associationof schizophreniawas observed for several 32 Ekelund J, Hovatta l, Parker A, ef a/. Chromosome 1 loci in Finnish SNP haplotypes. schizophreniafamilies. Hum Mol Genet 2001; 10:1611-1617. 166 Schizophrenia

33 Coon H, Myles-Worsley M, Tiobech J, et al. Evidence for a chromosome 50 Wong AH, Buckle CE, Van Tol HH. Polymorphismsin dopamine receptors: 2p13-14 schizophrenia susceptibility locus in families from Palau, Micro- what do they tell us? Eur J Pharmacol 2000; 410:183-203. nesia.Mol Psychiatry1998; 3:521-527. 51 Dubertret C, Gorwood P, Gouya L, et al. Association and excess of 34 Maziade M, Roy MA, Rouillard E, et al. A search for specific and common ' transmission of a DRD2 haplotype in a sample of French schizophrenic " susceptibilityloci for schizophreniaand bipolar disorder:a linkagestudy in 13 patients.Schizophr Res 2001 i 49:2Q3-212. target chromosomes. Mol Psychiatry2OO1; 6:684-693. A modest association (P=0.02-0.05) is reporled by schizophrenia and two Partial genome scan data (focused on candidate regions) for 19 Ouebecoise polymorphismsin DRD2 (dopamine receptor 2, 11q22-q23) in 50 French cases pedigrees with 70 narrow and nine broad cases (as well as bipolar cases and versus controls and by transmissiondisequilibrium test (TDT) in the same cases, some purely bipolar pedigrees). Suggestive linkage was observed on chromo- with a trend towards a later age of onset predicting the association. Previous somes 6p22-24 and'l 8q. DRD2 studies are also reviewed.

35 SchizophreniaLinkage CollaborativeGroup for Chromosomes 3, 6 and 8. 52 Virgos C, MartorellL, Valero J, et al. Associationstudy of schizophreniawith Additional support for schizophrenia linkage on chromosomes 6, 8: a ' polymorphismsat six candidate genes. Res 2001; '1 Schizophr 49:65-7 1. multicenterstudy. Am J Med Genet 996; 67:580-594. ln 262 Spanish cases versus 278 controls, an association at P=0.035 was observed aI DRD2, but not at five other loci (DRD3, 36 Levinson DF, 5HTR2A, Nf-3, BDNF or Holmans P, Straub RE, et a/. Multicenter linkage study of cNrfl. schizophrenia candidate regions on chromosomes 5q, 6q, 10p and 13q: Schizophrenia Linkage Collaborative Group lll. Am J Hum Genet 2O0O; 53 Hori H, Ohmori O, Shinkai T, et al. Association analysis between two 67:652-663. ' {unctional dopamine D2 receptor gene polymorphisms and schizophrenia. Am J Med Genet 2001; 105:176-178. 37 Levinson DF, Holmans PA, Laurent C, et al. No major schizophrenialocus ' No associationwas observed between schizophreniaand two polymorphismsin detected on chromosome 1q in a large multicentersample. Science 2002; 296:739-741. DRD2 in 241 Japanesecases versus 201 contrors. A large multicenter (779 sample pedigrees from eight schizophreniasamples) did 54 RybakowskiJK, Borkowska A, Czerski PM, Hauser J. Dopamine D3 receptor not produce significant evidence for linkage on chromosome 1q. The authors ' (DRD3) gene polymorphism is associated with the intensity of eye movement typed a 5 cM map spanning proximaland distal linkage findings. disturbances in schizophrenicpatients and healthy subjects. Mol Psychiatry 2OO1;6:718-724. 38 Sullivan PF, Eaves Li, Kendler KS, Neale MC. Genetic case-control An association (P=0.001-0.05) was observed between associationstudies in neuropsychiatry.Arch Gen Psychiatry2Q01; 58:1015- the severity of eye 1024. tracking deficits in schizophrenia patients and the Ser9Gly polymorphism in DRD3. 55 Anney RJ, Rees Ml, Bryan 39 Schwab SG, Knapp M, Mondaboni S, et a/. Support for association of E, et al. Characterisation,mutation detection, and ' association analysis promoters schizophreniawith genetic variationin the 6p22.3 gene, dysbindin,in sib-pair of alternative and 5' UTRs of the human dopamine D3 receptor gene families with linkage and in an additionalsample of triad families.Am J Hum in schizophrenia.Mol Psychiatry2OO2; 7:493- Genet 2003; 72:185-190. 502. No association was observed between schizophrenia and polymorphisms in 40 Pulver AE, Nestadt G, Goldberg R, et a/. Psychotic illness in patients alternative promoter and S'UTR regions of DRD3, and the finding of excess diagnosed with velo-cardio-facialsyndrome and their relatives.J Nerv Ment homozygosity of DRDS (dopamine 3 receptor,3q13.3) in schizophrenia Dis 1994;182:476-478. (previously reported by this and other groups) was not observed.

41 Karayiorgou M, Morris MA, Morrow B, et al. Schizophrenia susceptibility 56 Muir WJ, Thomson ML, McKeon P, et al. Markers close to the dopamine D5 ' associated with interstitial deletions of chromosome 22q11. Proc Natl Acad receptor gene (DRDS) show significant association with schizophrenia but Sci USA 1995; 92:7612-7616. not bipolardisorder. Am J Med Genet 2001; 105:152-158. Modest associations were observed between schizophrenia and a polymorphism 42 Murphy KC, Jones RG, Griffiths E, etal. Chromosome 22q11 deletions.An in DRD5 (dopamine 5 receptor,4p16) (P=0.024) and in a nearby microsatellite under-recognisedcause of idiopathiclearning disability. Br J Psychiatry1998; marker, D45615 (P=0.001), although the two markers were not in linkage 172:1 8O-1 83. disequilibrium(150 kb region). 43 Brzustowicz LM, Honer WG, Chow EW, et al. Linkage of familial 57 Williams J, Spurlock G, McGuffin P, et a/. Association between schizo- schizophreniato chromosome 13q32. Am J Hum Genet 1999; 65:1096- phrenia and T102C polymorphism of the 5-hydroxytryptamine 1103. type 2a- receptor gene. European Multicentre Association Study of Schizophrenia 44 Herken H, Erdal ME. Catechol-O-methyltransferasegene polymorphism in (EMASS) Group. Lancet 1996; 347:1 294-1296. ' schizophrenia: evidence for association between symptomatology and 58 Williams J, McGuffin P, Nothen M, Owen MJ. Meta-analysisof association prognosis.Psychiatr Genet 2001; 11:105-109. between the 5-HT2a receptor T1O2C polymorphism and schizophrenia. No association with schizophrenia was observed for the val/met polymorphism in EMASS Collaborative Group. European Multicentre Association Study of 129 cases and 165 controls from Turkey, althougha modest associationwith the Schizophrenia.Lancet 1997;,349:1221. severity of illness was noted. 59 Chen RY, Sham P, Chen EY, et al. No association between T102C 45 Norton N, Kirov G, Zammit S, et al. Schizophrenia and functional ' polymorphism of serotonin-2A receptor gene and clinical phenotypes of polymorphisms in the MAOA and COMf genes: no evidence for association Chinese schizophrenicpatients. PsychiatryRes or epistasis.Am J Med Genet 2002; 114:491-496. 2001; 105:175-185. No association was observed between schizophrenia and the vali 58met 60 Haider MZ, Zahid MA. No evidence for an association between the 5- polymorphism in COMT in 346 British cases and 334 controls. The A287G hydroxytryptamine5-HT2a receptor gene and schizophrenia in Kuwaiti Arabs. polymorphism was also negative in half of the sample. PsychiatryClin Neurosci 2OO2;56:465-467. 46 Liou YJ, Tsai SJ, Hong CJ, et a/. Associationanalysis of a functionalcatechol- 6'1 Liu W, Gu N, Feng G, et al. Tentative association of the serotonin transporter ' o-methyltransferasegene polymorphism in schizophrenicpatients in Taiwan. with schizophreniaand unipolar depression but not with bipolar disorder in Neuropsychobiology 2OO1; 43l.11-1 4. Han Chinese. Pharmacogenetics1999; 9:491-495. No association was observed between schizoohrenia and the val158met polymorphism in COMT in 198 Chinese cases and 188 controls, although a 62 Tsai SJ, Ouyang WC, Hong CJ. Associationfor serotonintransporter gene modest association (P=0.005) was reported. ' variable number tandem repeat polymorphismand schizophrenicdisorders. Neuropsychobiology2002; 45: 131 -1 33. 47 Semwal P, Prasad S, Bhatia T, et al. Family-based association studies of Very modest replication (P=0.043) was reported for the association of the monoaminergic gene polymorphismsamong North Indians with schizophre- serotonintransporter gene (S-HII-) with schizophreniain Han Chinese (1 14 cases nia. Mol Psychiatry2OO1; 6:220-224. versus 127 controls),the population in which such an associationwas previously 48 de Chaldee M, Corbex M, Campion D, et al. No evidence for linkage reoorted. ' between COMT and schizophreniain a French population. Psychiatry Res 63 Sanders AR, Cao O, Taylor J, et al.Genetic diversityof the human serotonin 2001; 102:87-90. receptor1B (HfR1B) gene. Genomics200.1 ;72:1-14. One of the negative association studies for older polymorphismsin COMf, in a small multiplexfamily sample, using family-basedassocation and NPL analyses. 64 Niesler B, Weiss B, Fischer C, et al. Serotonin receptor gene HTR3A variants in schizophrenic and bipolar affective patients. Pharmacogenetics 49 Weinberger DR, Egan MF, Berlolino A, et a/. Prefrontal neurons and the ' 2001; 11:21-27. genetics of schizophrenia.Biol Psychiatry2001; 50:825-844. A thoughtfulreview of animal and human studies of the physiologyof the cognitive 65 Schiffer HH. Glutamate receptor genes: susceptibility factors in schizo- role of prefrontalcortex, and of evidence that sequence variationin COMf is an ' phrenia and depressive disorders? Mol Neurobiol 2OO2;25:191-212. example of a polymorphism that directly influences this physiology through its A useful review of the evidencesupporting a role for glutamatergicmechanisms in effects on dopaminergic transmission. schizophrenia. Moleculargenetics of schizophreniaLevinson 167

66 Begni S, Popoli M, Moraschi S, et a/. Association between the ionotropic 78 Boin F, Zanardini R, Pioli R, et al. Association between G308A tumor ' ' glutamate receptor kainate 3 (GR/l(3) ser310ala polymorphism and necrosis factor alpha gene polymorphismand schizophrenia.Mol Psychiatry schizophrenia.Mol Psychiatry 2QO2;7:416-418. 2001;6:79-82. A modest association (P=0.0105) was reporled between schizophreniaand a In 84 patients versus 138 controls, modest association (P=0.0024) is reported ser31Oala polymorphism in GR/KS (ionotropic glutamate receptor kainate 3, between schizophreniaand an SNP in TNF2A (tumor necrosis factor alpha) in 1p34-33) in 99 ltaliancases and 116 controls. 6p21.1-21.3, the most centromeric portion of the rather broad candidate region on 6p. 67 Marti SB, Cichon S, Propping P, Nothen M. Metabotropicglutamate receptor ' 3 (GRM3) gene variation is not associated with schizophrenia or bipolar 79 Wei J, Hemmings GP. The NOTCH4 locus is associated with susceptibility affectivedisorder in the German population.Am J Med Genet 2002; i14:46- to schizophrenia. Nat Genet 2000; 25:376-377. 50. 80 Sklar P, Schwab SG, Williams NM, et al. Association analysisof NOTCH4 An association observed between schizophrenia and GRM3 (metabatropic loci in schizophrenia using family and population-based controls glutamate receptor 3, 7q21 .1-q21.2) in 265 cases versus 227 controls [Journal Articlel. Nat Genet 2QO1;28:126-128. (P=O.OO22) could not be confirmed in an additional 288 cases versus 162 controls and 128 trios (German). 81 McGinnis RE, Fox H, Yates P, et al. Failureto confirm NOTCH4 association with schizophreniain a large population-basedsample from Scotland. Nat 68 Ohtsuki T, Toru M, Arinami T. Mutation screening of the metabotropic ' Genet 2001 ; 28:128-129. glutamate receptor mGluR4 (GRM4) gene in patients with schizophrenia. PsychiatrGenet 2001; 11:79-83. 82 Fan JB, Tang JX, Gu NF, et al.A family-basedand case-control association ' No association was observed between schizophrenia and GRM4 (metabotropic study of the NOTCH4 gene and schizophrenia.Mol Psychiatry2OO2;7:1OO- glutamatereceptor 4,6p21.2), using nine newly discovered sequence variants,in 103. Japanese cases and controls. No association was observed between schizophrenia and NOfCH4 SNPs in 544 Han Chinese cases and 621 controls, as well as an analysisof over 300 trios. 69 Shibata H, Joo A, Fujii Y, et al. Association study of polymorphisms in the ' GluRb kainate receptor gene (GRIK1) with schizophrenia.Psychiatr Genet 83 lmai K, Harada S, Kawanishi Y, et a/. The (CTG)n polymorphism in the 2001;11:139-144. ' NOTCH4 gene is not associated with schizophrenia in Japanese individuals. No association was observed between schizophrenia and GR/KI (ionotropic BMC Psychiatry2001; 1:1. glutamate receptor kainate 1,21q22.11) using three new and three previously No association was observed between schizophrenia and NOfCH4 SNPs in 102 described SNPs in approximately200 Japanese cases and controls per analysis. Japanesecases versus 100 controls.

70 Joo A, Shibata H, Ninomiya H, et al. Structure and polymorphisms of the 84 Ujike H, Takehisa Y, Takaki M, et al. NOTCH4 gene polymorphism and ' human metabotropic glutamate receptor type 2 gene (GRM2): analysis of susceptibility to schizophrenia and schizoaffective disorder [Journal Article]. associationwith schizophrenia.Mol Psychiatry2001; 6:186-192. Neurosci Lett 2001; 3O1:41-44. No association was observed between schizophrenia and GRM2 (metabotropic 85 Schwab SG, Hallmayer J, Freimann J, et al. Investigationof linkage and glutamate receptor 2,3p12-p11) in 213 Japanese cases and 220 controls. ' association/linkagedisequilibrium of HLA A-, DQA|-, DAg-, and DRBl- allelesin 69 sib-pair-and 89 trio-families 71 Blackwood DHR, Fordyce A, Walker MT, et a/. Schizophrenia and affective with schizophrenia.Am J Med Genet 2OO2;114:315-320. disorders - cosegregation with a translocation at chromosome 1q42 that In 69 sib-pair families and 89 trios (mostly directlydisrupts brain-expressedgenes: clinicaland p3O0 findings in a family. European, a few non-Ashkenazi Am J Hum Genet 2001; 69:428-433. lsraelis), no significant association was observed between schizophrenia and DAil, DRBI, DAA| , or HLA-A alleles or haplotypes, although this group 72 Millar iK, Christie S, Anderson S, et al. Genomic structure and localisation continuedto observe suggestiveevidence of linkage (P= 0.0004) peakingat HLA- " within a linkage hotspot oI Disrupted In Schizophrenia 1, a gene disrupted by DABICAR (6p21.2). a translocationsegregating with schizophrenia.Mol Psychiatry2001; 6:123- 86 Matsumoto S, Sasaki T, lmamura 178. A, et al. HLA class I distribution in ' Japanese patients with schizophrenia. Am J Med Genet 2OO2; 114:42-45. This is the initial report on the genes DISCl and D/SC2 (parallel antisense genes) No association was observed between schizophrenia and any of 45 class I HLA found in the 1q breakpointregion of a (1;11) (q42.1; ql4.3) translocationthat alleles (i.e. the lowest uncorrected P value was 0.01), in 98 Japanese cases segregates with schizophrenia and other psychiatric disorders in a large Scottish peorgree. versus 393 controls. A7 Li T, UnderhillJ, Liu XH, et al. Transmissiondisequilibrium analysis of HLA 73 Devon RS, Anderson S, Teague PW, et al. ldentification of polymorphisms ' ' class ll DRBI, DAA| , DOB1 and DPB1 polymorphisms in schizophrenia within Disrupted in Schizophrenia 1 and Disrupted in Schizophrenia 2, and an using family trios from a Han Chinese population. Schizophr Res 2001; investigation of their association with schizophrenia and bipolar affective 49:73-78. disorder. Psychiatr Genet 2001; 11:71-78. In 165 Han Chinese proband-parent trios, no significant association of HLA Two plausible candidate genes for schizophrenia were discovered in the DRB1, DAAI , DOB or DPB alleles or haplotypes was observed after correction breakpoint of a (1;11) q14.3) translocation that segregates @a21i with for multipletesing (the lowest global Pvalue was 0.019). schizophrenia and other psychiatric disorders in a previously described very large Scottish pedigree. Although association with schizophrenia was not observed for 88 Blaveri E, Kalsi G, Lawrence J, et al. Genetic association studies of the SNPs described here in these genes, these genes may be of importance given ' schizophrenia using the 8p21-22 genes: prepronociceptin (PNOC), neuronal that this is one of the few relevantcytogenetic findings in schizophrenia. nicotinic cholinergic receptor alpha polypeptide 2 (CHRNA2) and arylamine N-acetyltransferase1 (NAf1). Eur J Hum Genet 2001; 9:469-472. 74 Semple CA, Devon RS, Le Hellard S, Porteous DJ. ldentificationof genes No association with schizophrenia was observed for markers in three genes in the ' from a schizophrenia-linkedtranslocation breakpoint region. Genomics 2OO1; ap21-22 region implicatedby schizophrenialinkage studies. 73:123-126. This paper describes the possible schizophrenia candidate genes in the 89 Freedman R, Coon H, Myles-Worsley M, et a/. Linkage of a neurophysio- breakpoint region on chromosome 11, for the 1;11 breakpoint described in this logical deficit in schizophrenia to a chromosome 15 locus. Proc Natl Acad Sci group's papers on the 1q breakpointregion. No associationdata for schizophrenia U S A 1997;94:587-592. are presented. 90 Freedman R, Adams CE, Adler LE, et a/. Inhibitoryneurophysiological deficit 75 Maziade M, Fournier A, Phaneuf D, et al. Chromosome 1q12-g22 linkage as a phenotype for genetic investigation of schizophrenia. Am J Med Genet ' results in eastern Ouebec families affected by schizophrenia. Am J Med 2000; 97:58-64. Genet 2OO2;114:51-55. 91 Freedman R, Adams CE, Leonard S. The alphaT-nicotinicacetylcholine Linkage was not observed on proximal chromosome 1q in 21 large French receptor and the pathology of hippocampal interneuronsin schizophrenia.J Canadian pedigrees. Chem Neuroanat 2000; 20:299-306.

76 lmamura A, Tsujita T, Kayashima T, et al. Lack of association between the 92 Freedman R, Leonard S, Gault JM, et a/. Linkage disequilibrium for ' hKCa3 gene and Japanese schizophreniapatients. Psychiatr Genet 2001; schizophreniaat the chromosome 15q13-14 locus of the alphaT-nicotinic 11:227-229. acetylcholinereceptor subunit gene (CHRNA4. Am J Med Genet 200 1; No association was observed between schizophrenia and a CAG reoeat in 1Q5:2Q-22. KCNN3 (1q21.2) in 1 12 Japanese cases and 102 controls. 93 Freedman R, Leonard S, Olincy A, et al. Evidence for the multigenic 77 Ritsner M, Modai l, Ziv H, et a/. An association of CAG repeats at the " inheritanceof schizophrenia.Am J Med Genet 2001; 105:794-800. ' KCNN3 locus with symptom dimensions of schizophrenia. Biol Psychiatry The authors re-analysedall families from the NIMH Genetics Initiativeschizo- 2OO2;51:788-794. phrenia project, combining European and African-Americanpedigrees (they had Longer alleles of the CAG repeat in KCNN3 (1q21 .2) predicted a greater severity previously been separately analysed) and using a parametric analysis under a of negative symptoms and of paranoid symptoms and an earlier age at onset in dominant transmission.Significant linkage was observed on chromosome 15q 117 lsraelicases (P<0.001 overall multivariateanalvsis of variance). near the CHRNAT locus. 168 Schizophrenia

94 Liu CM, Hwu HG, Lin MW, et a/. Suggestive evidence for linkage o{ l06Jorgensen TH, Borglum AD, Mors O, etal. Search for common haplotypes ' schizophreniato markers at chromosome 15q13-14 in Taiwanese families. ' on chromosome 22q in patients with schizophreniaor bipolar disorder from Am J Med Genet 2001; 105:658-661. the Faroe lslands. Am J Med Genet 2002; 114:245-252. Suggestive evidence for linkage was observed to markers near CHRNAT This is a report on progress towards finding shared haplotypes on chromosome (P=0.0003 and 0.0008 under broad and narrow diagnostic models by NPL 22q in schizophreniacases from a populationisolate. No missensemutations were analysis)in 52 Taiwanese schizophreniafamilies. found in WKL| , a gene in the region of interest in these families.

95 Tsuang DW, Skol AD, Faraone SV, et al. Veterans Affairs Cooperative Study. 107 McOuillinA, Kalsi G, Moorey H, et al. A novel polymorphismin exon 1 1 of the ' .l Examinationof genetic linkage of chromosome 5 to schizophreniain a large WKL| gene, shows no association with schizophrenia.Eur J Hum Genet Veterans Affairs Cooperative Study sample. Am J Med Genet 2O0l; 2OO2; 10:491-494. 105:662-668. Modest evidence for linkageto markers near CHRNAZ on chromosome 1bq was 108Gross J, Grimm O, Ortega G, et a/. Mutational analysis of the neuronal ' observed in 166 schizophreniafamilies (216 affected sib-pairs),with a maximum cadherin gene CELSRl and exclusion as a candidate for catatonic NPL score of 1.65. schizophreniain a large family. PsychiatrGenet 2001; 1 1:197-200. A negative association study in periodic catatonia (a phenotypic variant of 96 Gejman PV, Sanders AR, Badner )A, et al. Linkage analysisof schizophrenia schizophrenia) tor a 22q13.3 gene. ' to chromosome15. Am J Med Genet 2001; 105:789-793. Modest evidence for linkageto markers near CHRNAZ on chromosome 15q was 109 Mlmmack ML, Ryan M, Baba H, et a/. Gene expression analysis in ' observed in 68 schizophreniafamilies with a maximum lod score (Genehunter schizophrenia: reproducible up-regulation of several members of the Plus)of 2.0. apolipoproteinL family located in a high-susceptibilitylocus for schizophrenia on chromosome 22. Proc Natl Acad Sci U S A 2002; 99:4680-4685. 97 Xu J, Pato MT, Torre CD, et al. Evidence for linkagedisequilibrium between This is an intriguingstudy. A custom-made microarraywas used to screen ' brains the alpha 7-nicotinic receptor gene (CHRNAZ) locus and schizophreniain of schizophreniaand control subjects for differences in expression.Upregulation Azoreanfamilies. Am J Med Genet 2001; 105:669-674. was detected for APOL| (apolipoproteinL1) (2.6{old), a finding that was then An association between 9HRNAT and schizophrenia was observed in 31 families replicated in a second brain collection.APOL2 and APOL4 were then shown to from the Azores, with P=o.ooo4 for one marker. Differencesrelated to paternally be similarlyupregulated in two braincollections. All o{ these loci are in 22q12, near and maternallytransmitted alleles were also observed.The small sample size limits but not in the VCFS region. the interpretationof these findings. 110 Tachikawa H, Harada S, Kawanishi Y, et a/. Linked polymorphisms 98 Meyer J, Ortega G, Schraut K, et al. Exclusion of the neuronal nicotinic ' (- 333G > T and - 2BOA> G) in the promoter ' region of the CCK-A receptor acetylcholine receptor alphaT subunit gene as a candidate for catatonic gene may be associated with schizophrenia. Psychiatry Res 2OO1; 103l.147- schizophreniain a large family supporting the chromosome 15q13-22 locus. 155. Mol Psychiatry2OO2; 7 :220-223. Association is reporled between schizophreniaand linked polymorphismsin the These authors had observed linkage between the region of 15q containing CCKAR promoter region. CHRNAT and an alternative phenotype (periodic catatonia), but assocation with markers in CHRNAT was not observed. 111 Wang Z, Wassink T, Andreasen NC, Crowe RR. Possible associationof a ' cholecystokininpromoter variant to schizophrenia.Am J Med Genet 2OO2; 99 Arinami T, Ohtsuki T, Takase K, et al. Screening for 22q11 deletions in a 1 14:479-482. ' schizophreniapopulation. Schizophr Res 2001; 52:162-170. Modest association (P<0.05 in several tests) was reported between schizo- Of 300 Japanese patients, schizophrenia one had a 22q11.2 (VCFS) deletion, phreniaand a polymorphismin the CCK promoter region, in 85 cases versus 247 with no obvious stigmata of VCFS. controls, and in 60 trios (from the same cases). 100 De Luca A, Pasini A, Amati F, et al. Association study of a promoter 112 Hattori E, Yamada K, Toyota f , et al. Association studies of the CT repeat ' polymorphism of gene UFDlL with schizophrenia.Am J Med Genet 2001; polymorphism in the 5' upstream region of the cholecystokinin B receptor 105:529-533. gene with panic disorder and schizophreniain Japanesesubjects. Am J Med In BB patients and 92 controls from ltaly, evidence for the association of Genet 2001 ; 105:779-782. schizophreniawirh UFDlL was observed (P=0.009 {or the variantallele), with a modest confirmation(P= 0.03) in 38 proband-parent trios from Canada. This is an 113 Yoshikawa T, Kikuchi M, Saito K, et al. Evidencefor associationo{ the myo- ubiquitinfamily gene in the VCFS deletion region. ' inositol monophosphatase 2 (\MPA2) gene with schizophrenia in Japanese samples. Mol Psychiatry2QO1 ; 6:202-210. 101 Saito T, Guan F, Papolos DF, et al. Polymorphism gene in SNAP29 promoter Association (P=0.031-0.000.|) was reported between schizophreniaand three ' region associated with schizophrenia. Mol Psychiatry2001; 6:193-20'l . SNPs in myo-inositolmonophosphatase 2 (\MPA2, 18p11.2), in 302 Japanese A modest association (P= 0.009) was (a gene observed for SNAP29 in the VCFS schizophrenia cases versus 308 controls and 205 affective disorder cases. deletion region) and schizophrenia,but not bipolar disorder. 114Jun TY, Pae CU, Chae JH, eta/. Polymorphismof CTLA-4 gene at position 102 Takase K, Ohtsuki T, Migita O, et al. Association ZNF74 gene genotypes of ' 49 of exon I may be associatedwith schizophreniain the Korean population. ' with age-at-onsetof schizophrenia.Schizophr Res 2001;52:161-.|65. PsychiatryRes 2002; 1 1O:19-25. Association (P<0.0001) is reported here for age at onset of schizophrenia(but CTLA4 (cytotoxic T-lymphocyte antigen-4, 2q33) was studied in 1 16 cases versus not schizophrenia)with SNPs in the ZNF74 gene in 22q11.2 in the VCFS deletion 149 controls from Korea, based on an immune hypothesis.Modest evidence for region, in 300 Japanese cases versus 300 controls, and the finding was replicated associationwas reported (P=0.003 for alleles). in a second sample of 169 schizophreniapatients (P= O.OOOl), makingthis one of the few findings replicated in samples this large. ll5Ohtsuki T, Sakurai K, Dou H, et al. Mutation analysis of the NMDAR2B ' (GRIN2B) gene in schizophrenia.Mol Psychiatry2001 ;6:211-216. l03Feinstein C, Eliez S, Blasey C, Reiss AL. Psychiatric disorders and ' Although only modest evidence of association (P= 0.004 for homozygosity of behavioral problems in children with velocardiofacialsyndrome: usefulness linked SNPs) was reported between schizophreniaand GRIN2B (12p12), the as phenotypicindicators of schizophreniarisk. Biol Psychiatry2002; 51 :312- NMDA receptor 28, the sample size of 268 Japanese cases and 337 controls 31B. makes the study of some interest in generating hypotheses. The authors compared 28 children with VCFS with 29 children with comparable cognitive function, and found similar behavioraland psychiatricdisorders. They 116 Maes M, Delanghe J, Bocchio Chiavetto L, et a/. Haptoglobin polymorphism ' suggest that the specificity of the association of schizophreniawith the VCFS and schizophrenia: genetic variation on chromosome 16. Psychiatry Res deletion is unproved. However, they fail to account {or the high rate of 2001;104:1-9. schizophreniain adults with VCFS, certainly higher than in other groups with Modest association is reported between schizophrenia and Hp (haptoglobin, mild mental retardation. 16q22.1), in 98 schizophrenia cases compared with established genotype and plasma leveldistributions in this northernltalian population. The authors present a 104 Meyer J, Huberth A, Ortega G, et a/. A missense mutation in a novel gene ' brief but useful summary of evidence for involvement in the inflammatory system in encoding a pulative cation channel is associated with catatonic schizophrenia schizophrenia;Hp is one of the acute phase inflammatoryreaction proteins. in a large pedigree. Mol Psychiatry200 1; 6:302-306. These authors had reported linkage of periodic catatonia (a phenotypic variant of 117 Hong CJ, Tsai SJ, Wang YC. Association between tryptophan hydroxylase ' schizophrenia)to chromosome 22q13. Here they report the co-segregationof a gene polymorphism (4218C) and schizophrenic disorders. Schizophr Res missense mutation in WKL| (22q13.33) with the disorder in one extended 2001; 49:59-63. pedigree. Association between schizophrenia and the A218C polymorphism in TPH (tryptophan hydroxylase,11p14-p15.3) was observed (P=0.002) in 196 Han 105 DevaneyJM, Donarum EA, Brown KM, et a/. No missensemutation of WKL| ' Chinese cases versus 251 controls. This is the rate-limitingenzyme for serotonin in a subgroup of probands with schizophrenia.Mol Psychiatry2OO2; Z:419- biosynthesis. 423. A negative study of the association of schizophreniawith the WKL| gene on 118Chen CH, Hung CC, Wei FC, Koong FJ. Debrisoquine4-hydroxyrase 22q13.33, a region where linkage had been reported to the periodic catatonia (CYP2DO) genetic polymorphisms and susceptibility to schizophrenia in phenotype. Chinesepatients from Taiwan.Psychiatr Genet 2001; 11:153-155. Molecular genetics of schizophreniaLevinson 169

119Chiu HJ, Wang YC, Chen JY, et al. Association study of the p53-gene 140 Steel RM, Whalley HC, Miller P, et al. Structural MRI of the brain in ' ProT2Arg polymorphism in schizophrenia. Psychiatry Res 2OO1; 105:279- presumed carriers of genes for schizophrenia, their affected and unaffected 283. siblings. J Neurol, Neurosurg Psychiatry2OO2; 72:455458. 'obligate Based on a unique set of analyses of carriers' (well individuals who are 120 Chowdari KV, Brandstaetter B, Semwal P, et al. Association studies ol siblingsof a schizophreniapatient and who also have a schizophrenico{fspring), a cytosolic phospholipase A2 polymorphisms and schizophreniaamong two reduced volume of the amygdalohippocampal complex is suggested to be a independent family-basedsamples. PsychiatrGenet 2001 ; 11:2O7-212. specific correlate of genetic risk. 121 lshiguro H, Ohtsuki T, Okubo Y, et al. Association analysis of the pituitary adenyl cyclase activating peptide gene (PACAfl on chromosome 18p11 with 141 Narr KL, Cannon TD, Woods RP, et al. Genetic contributions to altered schizophrenia and bipolar disorders. J Neural Transm - Gen Sect 2001; ' callosal morphology in schizophrenia.J Neurosci 2OO2;22:3720-3729. 108:849-854. An upward bowing of the corpus callosum was suggested to be a neuroanato- mical marker for vulnerability to schizophrenia in the co{wins of cases. 122 lshiguro H, Okubo Y, Ohtsuki T, et al. Mutation analysis of the retinoid X receptor beta, nuclear-related receptor 1, and peroxisome proliferator- 142Egan MF, Hyde TM, Bonomo JB, et al. Relativerisk neurological activated receptor alpha genes in schizophrenia and alcohol dependence: of signs in ' siblings of patients with schizophrenia.Am J Psychiatry 2001; possible haplotype association of nuclear-related receptor 1 gene to alcohol 158:1827- 1834. dependence. Am J Med Genet 2002; 114:15-23. Neurological signs were found to be increased in the relatives of schizophrenia 123Jun TY, Pae CU, Chae JH, et al. Report on lL-10 gene polymorphism at patients, but the low relative risk suggested that these signs might be poor position 819 for major depression and schizophreniain Korean population. markers for genetic studies. Psychiatr Clin Neurosci 2OA2; 56:1 77-180. 143 Scutt LE, Chow EW, Weksberg R, et a/. Patterns of dysmorphic l24Chiavetto LB, Boin F, Zanardini R, et a/. Association between promoter features in schizophrenia.Am J Med Genet 2001 105:713-723. polymorphic haplotypes of interleukin-10 gene and schizophrenia. Biol ; Psychiatry 2AO2; 51 :480-484. '144 Cardno AG, Sham PC, Farmer AE, et al. Heritability of Schneider's Jirst-rank '1 125 Kunugi H, Kato T, Fukuda R, et al. Association study of C825T polymorphism ' symptoms. Br J Psychiatry 2002; 80:35-38. of the G-protein b3 subunit gene with schizophrenia and mood disorders. J First-rank psychotic symptoms were shown to be heritable in twins, although less - Neural Transm Gen Sect 2002; 109:213-218. so than the categorical diagnosis of schizophrenia. 126 Lee K, Kunugi H, Nanko S. Glial cell line-derivedneurotrophic factor (GDNF) gene and schizophrenia:polymorphism screening and 145 Cardno AG, RijsdijkFV, Sham PC, et al. A twin study of genetic relationships association analysis. ' Psychiatr Res 2001; 1Q4:11-17. between psychotic symptoms [see Comments]. Am J Psychiatry 2002; 159:539-545. 127 Leroy S, Griffon N, Bourdel MC, et al. Schizophrenia and the cannabinoid Using the Maudsley twin series, the authors suggest that if schizophrenic, manic receptor type 1 (CB1): association study using a single-base polymorphism and depressive syndromes are assigned non-hierarchically,they show substantial in coding exon 1. Am J Med Genet 2001 ; 105:749-752. overlap in their genetic etiology.See comment by Kendler [146.]. 128 Matsumoto C, Ohmori O, Hori H, et al. Analysis of associalion between the Gln192Arg polymorphism of the paraoxonase gene 146 Kendler KS. Hierarchy and heritability:the role of diagnosis and modeling in and schizophrenia in ' humans.Neurosci Lett 2002; 321:165-168. psychiatricgenetics. Am J Psychiatry2OO2;159:515-518. Commenting on Cardno et al. [144'1, the author points out that their data are more 129Ouyang WC, Wang YC, Hong CJ, Tsai SJ. Estrogen receptor alpha gene consistent with genetic factors influencing mood syndromes in individuals with polymorphism in schizophrenia: frequency, age at onset, symptomatology and schizophrenia, rather than for genetic overlap in the etiology of schizophrenia and prognosis. Psychiatr Genet 2001; 11:95-98. bipolar disorder. l30Ventriglia M, Bocchio Chiavetto L, Bonvicini C, etal. Allelic variationin the human prodynorphin gene promoter 147 Brown AS, Schaefer CA, Wyatt RJ, et al. Paternal age and risk of and schizophrenia. Neuropsychobiology " 2OO2;46:17-21. schizophreniain adult offspring. Am J Psychiatry2OQ2; 159:1528-1533. Using a birth cohort from which individuals with schizophrenia spectrum disorders 131 Segman RH, Shapira Y, Modai l, etal. Angiotensinconverting enzyme gene had previously been ascertained, the authors demonstrate a small but significant insertion/deletion polymorphism: case-control association studies in schizo- relationship between advancing paternal age and the risk of these disorders, after phrenia, major affective disorder, and tardive dyskinesia and a family-based controlling for confounding variables such as maternal age. This suggests the association study in schizophrenia.Am J Med Genet 2002; 114:31G-314. possibility of de-novo genetic mutations in older fathers as factors in schizophrenia. '132 Zhang B, Tan Z, Zhang C, et al. Polymorphisms of chromogranin B gene associated with schizophrenia population. 148 Mafaspina D, Corcoran C, Fahim C, et al. Paternal age and sporadic in Chinese Han Neurosci Lett ' 2OO2: 323:229-233. schizophrenia: evidence for de novo mutations. Am J Med Genet 2002; 1 14:299-303. 133 Hattori M, Kunugi H, Akahane A, etal. Novel polymorphismsin the promoter Schizophrenia patients without a family history had significantly older fathers than region of the neurotrophin-3 gene and their associations with schizophrenia. those with a family history, supporting the hypothesis of de-novo genetic mutations Am J Med Genet 2002; 114:304-309. in older fathers. 134 Leszczynska-Rodziewicz A, Czerski PM, Kapelski P, et a/. A polymorphism of 149 Malaspina D. Paternal factors the norepinephrinetransporter gene in bipolar disorder and schizophrenia: and schizophrenia risk: de novo mutations and ' imprinting. lack of association. Neuropsychobiology 2OO2; 45:1 82-1 85. Schizophr Bull 2001; 27:379-393. The author reviews neurodevelopmental disorders previously associated with de- 135 Feng J, Zheng J, Gelernter J, et al. An in-frame deletion in the alpha (2C) novo germline mutations in older fathers, and discusses mechanisms by which this adrenergic receptor is common in African-Americans.Mol Psychiatry2001; effect can occur, relating it to data for schizophrenia. 6:168-1 72. 150 Lewis DA, Levitt P. Schizophrenia as a disorder neurodevelopment 136 Frieboes RM, Moises HW, Gattaz WF, et a/. Lack of association between of " 18 re{s] Annu Rev Neuroscience 2QO2;25:409-432. schizophreniaand the phospholipase-A(2)genes IPLA2 and sPLA2. Am J [Review]. [1 Med Genet 2OQ1; 105:246-249. This is a comprehensive review of evidence favoring a neurodevelopmental etiology ('pathogenetic biological events are present much earlier in life than the 137 Tuulio-HenrikssonA, Haukka J, Partonen T, et al. Heritabilityand number of onset of the features of the illness', p.411). Evidence for such influencesare ' quantitative trait loci of neurocognitive functions in families with schizophrenia. reviewed by time period (prenatal, perinatal, childhood and adolescence). Am J Med Genet 2002; 114:483-490. Emphasis is placed on the strength of evidence for a relationship between Based on data from 264 schizophrenia patients and their relatives from a schizophreniaand complications during labor and delivery,and the presence of genetically isolated region in Finland, the authors suggest that measures of subtle behaviors that predate active illness by many years. A polygenic- working memory show strong heritability, perhaps as a result of a very small multifactorial model is favored whereby genetic predisposition which alters number of genetic loci, and could be used for mapping studies. development, gene-environment interactions that influence or trigger the genetic effects, and cumulative effects over time of the altered development, leading to a 138 Cosway R, Byrne M, Clafferty R, et a/. Neuropsychologicalchange in young comparably siable state that is relatively difficult to alter. people at high risk for schizophrenia: results from the first two neuropsycho- logical assessments of the Edinburgh High Risk Study. Psychol Med 2OOO; 30:11 1 1-1121. 151 Maynard TM, Sikich L, Lieberman JA, LaMantia AS. Neural development, ' cell-cell signaling, and the two-hit hypothesis of schizophrenia.Schizophr 139 Cosway R, Byrne M, Clafferly R, et a/. Sustained attention in young people at Bull 2001: 273:457-476 ' 'two-hit' high risk for schizophrenia. Psychol Med 2002; 32:277-286. These authors argue for a hypothesis of schizophrenia whereby genetic or Measures of attention were not found to differentiate significantly between the environmental factors alter early development, and then a second factor closer to relatives of schizophrenia and control subjects. the time of onset triggers the actual disease. 17O Schizophrenia

'f 152 Schiffman J, Ekstrom M, LaBrie J, et al. Minor physical anomalies and 55 Judson R, SalisburyB, Schneider J, et al. How many SNPs does a genome- " schizophrenia spectrum disorders: a prospective investigation. Am J wide haplotype map require? Pharmacogenomics2002; 3:379-391. Psychiatry 2002; 159:238-243. In this uniquestudy, 265 childrenfrom a 1959-1961 Danish birth cohort (90 with a 156 Gabriel SB, SchaffnerSF, Nguyen H, et al. The structureof haplotypeblocks parent with schizophrenia, 93 with a parent with some other psychiatric disorder, in the human genome. Science 2OO2;296:2225-2229. and 82 with no record of a psychiatrically ill parent) had been rated for minor physical anomalies at 11-13 years of age. Psychiatric diagnosis was then determined at 31-33 years by direct interview or records. of 131 children with 157 Daly MJ, RiouxJD, Schaffner SF, et al. High-resolutionhaplotype structure in three or more anomalies, 20 (15.3%) developed a schizophrenia spectrum the human genome. Nat Genet 2OO1;29:229-232. disorder, compared with six out of 1 1 1 children with two or fewer anomalies (5.4%) (P<0.01). For the high-risk group the proportions were 12 out of 39 158 Bouchie A. Haplotype map planned. Nat Biotechnol 2001; 19:704. (30.1%) versus five out of 42 (11.9%) (P<0.04). These are striking results suggesting early, physical-developmental effects of genetic factors, although the high rate of schizophreniaspectrum disorders in this study population is a bit 159 Weiss KM, TerwilligerJD. How many diseases does it take to map a gene surprising. with SNPs? Nat Genet 2000; 26:151-157. 153 Bassett AS, Chow EW, O'Neill S, Brzustowicz LM. Genetic insightsinto the ' ',| neurodevelopmental hypothesis of schizophrenia. Schizophr Bull 2001; 60 Faham M, Baharloo S, Tomitaka S, ef al. Mismatch repair detection (MRD): 27:417-43O. high{hroughput scanning for DNA variations. Hum Mol Genet 200.1; This article provides a useful review of neurodevelopmental research in 10:1 657-1 664. schizophreniafrom a group that has focused on the study of classic genetic features such as physical anomaliesand the VCFS syndrome. 161 Conrad P. Genetic optimism: framing genes and mental illness in the news. 154Delisi LE. speech disorder in schizophrenia: review of the literatureand ' Cult Med Psychiatry2001;25:225-247. ' exploration of its relation to the uniquely human capacity for language. The author analyzes news reports about psychiatric genetics findings and critiques 'genetic Schizophr Bull 2001 ; 27:481-496. the optimism' that emphasizesthe inevitabilityof discovering genes and Based on data from a study oJ structured ratings of elements of language in free- the good outcomes of those discoveries, whereas negative or retracted findings form speech, the author proposes that the pathology of schizophrenia may be receive no attention. Scientific colleagues in genetics and other fields are prone to related to genes underlyinguniquely human characteristicsof language. similardistortions, as discussed in the present article.