Ophthalmogenetics Prof. Maciej Krawczyński, MD, PhD

 the first modern description of a hereditary disorder (protanopia, Dalton, 1798);  the first linkage of a disease locus to a chromosome (daltonism linked to X chromosome, Wilson, 1911);  the first linkage of a disease locus to other trait (daltonism and haemophilia, Bell & Haldane, 1937);  the first book on genetics (Waardenburg, 1938);  the first linkage of a disease locus to an autosome (catar. centr. pulver. to Duffy blood group on chrom. 1, 1963);  the first mtDNA mutation in (11778G>A in LOHN, Wallace, 1988)  the first description of a digenic disorder in humans (RDS and ROM1 genes in pigmentosa, Dryja, 1995).

Ophthalmogenetics in numbers  OMIM (On-line Mendelian Inheritance in Man) database lists 1417 hereditary disorders, related to eye pathology:  1202 – known phenotype and known gene;  123 – known phenotype and mendelian inheritance;  92 – known phenotype with suspected mendelian inheritance.

Ophthalmogenetics in numbers  RetNet database lists 256 cloned or mapped genes that cause hereditary retinal disorders.

Oculogenesis Process of embryonal eye ball development:  genetically controlled;  susceptible to damaging environmental factor (teratogens);  embryo (fetus) age dependent.

Genetic regulation of oculogenesis  primary switch – PAX6 gene;  leading role of cascade: PAX6-EYA1/SIX3-DACH1;  complex network of dependences, synergies and inhibitions;  evolutionary and tissue conservative process;  mutations of these genes are the cause of many developmental defects.

PAX6 gene  locus: 11p13; transcriptional factor;  the main oculogenesis regulator – it is electively expressed in the developing eye:  initially in major part of head ectoderm;  later - only in optic vesicle and placode (lens vesicle).  mutations of PAX6 gene cause;  (with macular hypoplasia, , corneal opacities);  Peters anomaly, with late ;  hereditary , isolated macular hypoplasia;  isolated dislocation;  multiple eye defects without aniridia;  homozygotic mutations – cause congenital anophthalmia !  11p13 microdeletion – WAGR syndrome.

Aniridia  always bilateral, 1:50.000 births;  PAX6 gene mutations; AD inheritance;  clinical classification (6 types):  I: total, with low VA, macular hypoplasia and ;  II: partial with normal VA;  III: with ataxia and MR (Gillespie s.) – AR, very rare;  IV: with Wilms tumour, genitourinary system defects and MR (WAGR s., Miller s.) – 11p13 microdeletion or AD;  V: with other eye defects;  VI: with other systemic defects.  in 75% of patients - – needs early surgical intervention;  regular ultrasound examination of kidneys;  karyotype analysis is necessary (to exclude microdeletion).

Other oculogenesis genes  EYA1 – its mutations cause BOR s. (branchio-oto-renal syndrome);  SIX3 – its mutations cause holoprosencephaly with severe eye defects (cyclopia, microphthalmia, hypotelorismus);  SIX6 (OPTX2) – its mutations cause microphthalmia with congenital cataract;  PAX2 – its mutations cause head defects and colobomas with kidneys defects (papillo-renal syndrome);  PAX3 – its mutations cause Waardenburg syndrome;  CHX10 – its mutations cause complex microphthalmia;  PITX2 – its mutations cause Axenfeld-Rieger syndrome.

Axenfeld-Rieger syndrome  AD inheritance, PITX2 gene;  posterior embryotoxon !  prominent, anteriorly displaced Schwalbe line;  peripheral streaks connected to embryotoxon;  developmental iris defects (pseudopolycoria, corectopia, hypotrophia);  glaucoma risk: 50-60%;  hypo-, oligo-, anodontia;  malar hypoplasia, hypertelorismus;  umbilical hernia;  „empty saddle” syndrome.

Waardenburg syndrome  AD inheritance;  PAX3 and MITF genes  heterochromatic irides;  uveal hypopigmentation;  telecanthus and dislocation of lacrimal points;  white forelock;  local skin decoloration;  neurosensory deafness.

Tumour suppressor genes in  retinoblastoma - RB1 - 13q14;  von Hippel-Lindau disease - VHL - 3p26;  neurofibromatosis type 1 - NF1 - 17q11;  neurofibromatosis type 2 - NF2 - 22q12;  tuberous sclerosis - TSC1 - 9q34, TSC2 – 16p13;  malignant melanoma - CDKN2/p16 - 9p21;  polypous colon cancer - APC - 5q21

Retinoblastoma  malignant embryonic neoplasm of , in children before 5 yrs;  white or grey pupil (leucocoria);  persistent unilateral ;  eye or inflammatory reaction;  secondary glaucoma.  60% - non-hereditary cases;  40% - hereditary cases;  germinal RB1 gene mutations;  90-95% penetrance;  in 3-6% children with retinoblastoma – 13q14 microdeletion:  facial dysmorphy, low-set ears, MR;

Neurofibromatosis  AD inheritance, NF1 gene;  Lisch nodules on the iris;  multiple skin neurofibromas;  „cafe-au-lait” skin spots;  optic nerve gliomas (15%);  other CNS tumours (1-2%), pheochromocytomas (1-3%);  arterial hypertension (2%), epilepsy (3%);

Tuberous sclerosis  AD inheritance, TSC1, TSC2 genes;  facial fibroangiomas (adenoma sebaceum, 50%);  retinal astrocytoma (50%);  skin decoloration spots;  shagreen skin (20-40%);  enamel defects (70%);  intracranial calcifications;  epilepsy (90%), MR (50%), kidneys tumours (60%), heart myomas (30%).

Von Hippel-Lindau disease  AD inheritance, VHL gene;  retinal haemangiomas (60%);  embryonic haemangiomas of cerebellum, spinal cord and brain stem (70%);  renal cancers (28%);  pheochromocytomas (7%);  renal, pancreatic, hepatic and epidydymic cysts.

Sturge-Webera syndrome  usually sporadic;  facial haemangioma;  ipsilateral soft meninges haemangioma  uveal eye haemangioma and secondary glaucoma;  sometimes: epilepsy, paresis, MR.

Hereditary optic nerve neuropathies  Leber hereditary optic nerve neuropathy (LHON) - Mt;  Kjer hereditary optic nerve neuropathy (ADOA) - AD;  simple, recessive optic nerve neuropathy - AR;  hereditary XR optic nerve neuropathy – OPA2 gene (Xp11);  complex Behr optic nerve neuropathy - AR.

LHON  mitochondrial inheritance;  85% - males (40-80% penetrance), usually in 15-30 yrs.;  15% - females (10-20% penetrance);  1/7 – sporadic cases, 6/7 – affected maternal family members;  Wallace (1988) - identification of the first point mutation (11778 mtDNA) – present in 50-75% of patients in Europe.

Unusual phenomena in LHON genetics  mutations heterogeneity:  primary: mainly 11778, 3460, 14484;  secondary (synergy);  suppressor - eg. 4136.  heteroplasmy – normal and mutant mtDNA in one person:  different recurrence risks;  changes from one generation to the next.  mtDNA interaction with nuclear genome:  suspected specific XR allele of loss of vision predisposition – not confirmed.

Kjer optic nerve neuropathy (ADOA)  AD inheritance;  3 genes: OPA1 (3q28-29), OPA3 (19q13) and OPA4 (18q12);  differential diagnosis with LHON:  earlier onset (usually<10 yrs); blue color vision defect;  better visual prognosis;  acute phase present in LHON (peripapillar teleangiectatic microangiopathy).

Recessive optic nerve neuropathy  AR inheritance;  rare, age of onset - usually < 5yrs;  very pale optic head with retinal vessels narrowing (like in retinal dystrophies);  Behr syndrome – complex optic nerve neuropathy (with: cerebellar ataxia, spasticity, muscular hypertonia, MR).

Hereditary hypopigmentations  melanine production defects:  oculo-cutaneous albinism (OCA) - AR,  ocular albinism (OA) - XR;  OCA-associated syndromes.  melanocytes migration defects:  albinoidism - AD,  piebaldism - AD,  Waardenburg syndrome - AD.

Oculo-cutaneous albinism (OCA)  OCA1 – linked to tyrosinase:  1A - „classical”,  1B - „yellow”,  1MP, 1TS – milder forms;  OCA2 – linked to P gene: (P protein in melanosome membrane is responsible for tyrosine transport);  OCA3 – linked to TRP1 gene: (protein that takes part in melanine production).

Chediak-Higashi syndrome  AR inheritance;  partial OCA;  High predisposition to infections in children;  hepatomegaly and lymphadenopathy;  lymphomas in youth.

Hermansky-Pudlak syndrome  AR inheritance;  classical or partial OCA;  blood plates dysfunction;  subcutaneous haemorrhages;  pulmonary fibrosis;  enterocolitis.

Ocular albinism  Nettleship-Falls type - XR;  the most frequent type of OA,  in female-carriers: partial iris translucency and granular eye fundus depigmentation;  Aland Islands type - XR;  autosomal recessive type – very rare.

Retinal dystrophies  macular dystrophies (central);  peripheral retinal dystrophies;  hereditary vitreoretinopathies;  choroidal dystrophies;  stationary photoreceptor dystrophies:

Macular dystrophies  – AR,  Leber congenital amaurosis (LCA) – AR,  Best vitelliform macular dystrophy – AD,  cone-rod dystrophy („bull’s eye”) – AD, XR,  juvenile – XR,  pattern macular dystrophies – AD,  Sorsby pseudo-inflammatory dystrophy – AD,  North Carolina macular dystrophy – AD,  familal macular drusen – AD,  cystic macular dystrophy – AD.

Stargardt disease  s.c. juvenile , 1:10.000;  first description – Stargardt, 1909;  diagnosis: in 35% <10yrs, in 70% <20yrs, in 95% <40yrs;  course: progressive central vision loss, in early onset – VA: 0.1 in the beginning of the second life decade;  prognosis: in 5 years VA decreases to 0.1 – than very slowly.

Stargardt disease  Diagnosis:  decreased VA (often suspected simulation), (central );  ophtalmoscopy – initially normal, than yellow granularities in macula, and typical (sometimes „fundus flavimaculatus”);  fluorescein angiography (FA) !!! – „masked choroidea” in 80% of patients;  family history – usually negative;  ABCR gene molecular analysis.

Stargardt disease  Genetics:  AR inheritance, ABCR gene (locus: 1p21-p22);  population carrier frequency – 1:50;  retina-specific, ATP-binding transport protein, expressed in outer segments of photoreceptors;  >600 different mutations;

Leber congenital amaurosis (LCA)  the first description – Leber, 1869;  AR inheritance – approx. 20 genes;  1:30.000, 10-20% of congenital blindness in developed countries;  in children: usually VA<2/50, in 10-20% - 5/50-5/16;  adults are usually blind.

Leber congenital amaurosis (LCA)  Diagnosis:  nystagmus, , „eye-fingers” symptom;  no pupil light reaction;  hyperopia, very low VA;  totally absent ERG responses !!!  0-3yrs – normal eye fundus, than – „leopard skin” appearance;  molecular analysis of causative genes !

LCA genetics  mutations identified in 80% of patients;  20 mapped genes, 18 cloned genes;  LCA1 – GUCY2D (6-21%);  LCA2 – RPE65 (3-16%);  LCA3 – RDH12 (~4%);  LCA4 – AIPL1 (4-8%);  LCA5 – locus 6q11-q13 – lebercilin;  LCA6 – RPGRIP1 (~5%);  LCA7 – CRX (~3%);  LCA8 – CRB1 (5-15%);  LCA9 – locus 1p36 – gene ???  LCA10 – CEP290 (10-22%);  LCA11 – IMPDH1;  LCA12 – RD3;  LCA13 – locus 14q24 – gene ???  LRAT i TULP1.

Leber congenital amaurosis (LCA)  Treatment:  natural animal model – French Briard dogs – often suffer from RPE65-dependent LCA;  successful gene therapy with AAV virus (vector);  permanent functional, electrophysiologic and biochemical success;  V. i X. 2007 – first clinical tests on 9 persons – Univ. College of London, Univ. of Pennsylvania, Univ. of Florida  28.04.2008 – first results described (N.Engl.J.Med.)

Cone-rod dystrophies  many entities with similar symptoms but different dynamics;  usually AD inheritance, rare XR, min. 25 genes;  Diagnostic:  photophobia, nystagmus (not always);  decreased VA, defects;  ophthalmoscopy and FA – „bull’s eye” maculopathy;  visual field (central scotoma);  ERG – photopic response reduction !;

Alström syndrome  AR inheritance;  cone-rod dystrophy;  obesity, hypogonadism;  diabetes, asthma;  hypothyroidism;  cardiomyopathy, hypertension;  sensorineural hearing loss;  normal IQ.

Juvenile retinochisis  first symptoms: <10yrs;  XR inheritance - RS1 gene – retinoschisin;  >100 known mutations;  protein that is responsible for intracellular adhesion;  Diagnosis:  ophtalmoscopy – always typical „bicycle-wheel” maculopathy, than – vitreo-retinal tractions;  FA – usually normal;  ERG – elective B wafe reduction !!!  family history, gene molecular analysis.

Best vitelliform macular dystrophy  first description – Best, 1905;  AD inheritnace, BEST1 (VMD2) gene – bestrophin;  elective expression in cell membrane of RPE and forms a chlorine channel;  typical, atypical (VMD1 gene), adults forms;  beginning: decreased VA and metamorphopsia, vitelliform changes in macula present directly after birth or with later onset, typical evolution;  prognosis: useful VA – until 7. decade.

Best vitelliform macular dystrophy  Diagnosis:  VA, Amsler test;  ophthalmoscopy;  ERG – normal;  EOG – typical !!! – no increase in light (Arden factor <1,5);

Peripheral retinal dystrophies  - AD, AR, XR, AD, Mt;  juvenile retinoschisis - XR;  Leber congenital amaurosis - AR;  fundus flavimaculatus - AR;  fundus albipunctatus - AR.

Retinitis pigmentosa  many entities with similar symptoms;  prevalence: 1:4000;  inheritance: AD, AR, XR, XD, Mt, digenic;  approx. 60 different genes:  phototransduction proteins;  rod outer segments proteins;  retinol metabolism proteins;  other proteins – eg. RPGR (GTPase regulator).  molecular analysis of causative genes.

Retinitis pigmentosa - diagnosis  ophthalmoscopy – typical triade of symptoms;  visual field – concentric narrowing !  night blindness – first sign !  ERG – scotopic resonse reduction, than no response;  molecular analysis of causative genes !

Usher syndrome  AR inheritnace, min. 12 genes;  several types;  retinitis pigmentosa;  congenital sensorineural hearing loss (deafness);  sometimes labirynthine dysfunction and psychotic symptoms.

Bardet-Biedl syndrome  inheritance: oligogenic triallelic or AR;  atypical retinitis pigmentosa with maculopathy;  obesity and hypogonadism;  polydactyly, renal defects;  sensorineural hearing loss;  sometimes MR.

Kearns-Sayre syndrome  mitochondrial inheritance;  large mtDNA deletions;  chronic progressive external ophthalmoplegia;  retinitis pigmentosa (atypical);  short stature, ataxia, heart block, deafness, diabetes, hypothyroidism, hypogonadism, myopathy.

Cohen syndrome  AR inheritance (Finland, Israel, Libanon);  progressive ;  retinitis pigmentosa (atypical);  muscular hypotony in infancy; MR;  obesity, elongated fingers;  prominent incisors;  dysmorphic features.

Hereditary vitreoretinopathies  Norrie disease - XR;  juvenile retinoschisis - XR;  Goldmann-Favre syndrome - AR;  Wagner s., Stickler s., Marshall s. - AD;  familial exsudative vitreoretinopathy (FEVR):  ADFEVR (Criswick-Schepens s.) - AD;  XLFEVR - XR;  familial neovascular inflammatory vitreoretinopathy (ADNIVR) - AD;  familial vitreoretinochoroidopathy (ADVIRC) - AD.

Choroidal dystrophies  - XR;  atrophia gyrata - AR;  central areolar choroidal dystrophy - AR, AD;  generalized choroidal dystrophy - AD.

Stationary photoreceptors dystrophies  congenital stationary night blindness (CSNB):  known 8 genes - AD, AR, XR;  congenital olor blindness (daltonism):  protanopia, deuteranopia - XR;  tritanopia - AD;  blue-cone monochromacy - XR;  rod monochromacy () - AR.

Multifactorial eye disorders  Age-related macular degeneration (AMD)  Primary open angle glaucoma (POAG)

AMD predisposition genes  ARMD1 – 1q24-q25 – FBLN6 (HMCN1) (2003)  ARMD2 – 1p21-p13 – ABCR (1997)  ARMD3 – 14q32 – FBLN5 (2004)  ARMD4 – 1q32 – CFH (2005)  ARMD5 – 10q11 – ERCC6 (2006)  ARMD6 – 19p13 – RAXL1 (2005)  ARMD7 – 10q25-q26 – HTRA1 (2006)  ARMD8 – 10q25-q26 – ARMS2 (2005)  ARMD9 – 9p13 – C3 (2007)  ARMD10 – 9q32-q33 – TLR4 (2005)  ARMD11 – 20p11 – CST3 (2006)  1q31-q32 – CFHR1 and CFHR3 (2006)  6p21 – CFB and C2 (2006)  3pter-p21 – CX3CR1 (2007)  6q25 – ESR1 (2007)  mtDNA – MTTL1 (2006)

POAG predisposition genes  GLC1A – 1q24-q25 – TIGR (MYOC) gene 1997r.  GLC1B – 2cen-q13 1996r.  GLC1C – 3q14-q24 1997r.  GLC1D – 8q23 1998r.  GLC1E – 10p14-p15 – OPTN gene 2002r.  GLC1F – 7q35-q36 1999r.  GLC1G – 5q22 – WDR36 gene 2005r.  GLC1H – 2p15-p16 2007r.  GLC1I – 15q11-q13 2000/2005r.  GLC1J – 9q22 2004r.  GLC1K – 20p12 2004r.  GLC1L – 3p 2005r.  GLC1M – 5q22-q32 2004/2007r.  GLC1N – 15q22-q24 2006r.

Alarming eye symptoms in infants  corneal diameter (normal: 10-12mm);  corneal transparency (leucoma ?);  pupil color ( ?);  shape and size of the pupil (aniridia, coloboma);  permanent unilateral strabismus;  congenital nystagmus (in first 3 months);  photophobia (usually with lacrimation);  no visual contact (3-month-old children).