ORIGINAL CONTRIBUTION A Novel Duplication Confirms the Involvement of 5q23.2 in Autosomal Dominant Leukodystrophy Inge A. Meijer, PhD; Ana A. Simoes-Lopes, MD; Sandra Laurent; Tanya Katz, BSc; Judith St-Onge, DEC; Dominique J. Verlaan, PhD; Nicolas Dupre´, MD, MSc; Manon Thibault, MD; Johanne Mathurin, MD; Jean-Pierre Bouchard, MD; Guy A. Rouleau, MD, PhD Objective:: To identify the underlying locus and disease- Results: The thorough candidate gene approach did not causing mutation for adult-onset autosomal dominant leu- identify any mutation. Consequently, a whole-chromo- kodystrophy (ADLD). some comparative genomic hybridization for chromo- some 5 identified a 280-kilobase duplication within the Design: Previously, an adult-onset ADLD locus on chro- chromosomal band 5q23.2 in 2 affected individuals. This mosome 5q23 was mapped between markers D5S1495 duplication contains 3 genes: LMNB1, FLJ36242, and and CTT/CCT15. This region contains 13 known and pu- MARCH3. tative candidate genes. A 2-point linkage analysis con- firmed linkage of a large multigenerational French Ca- Conclusion: We have identified a novel duplication on nadian family to chromosome 5q23. In addition, screening chromosomal band 5q23.2 in a French Canadian family of the 13 genes within the candidate interval as well as 5 with ADLD that supports the implication of duplicated neighboring genes was completed, followed by compara- LMNB1 as the disease-causing mutation. However, ad- tive genomic hybridization. ditional functional studies of lamin B1 overexpression are necessary to elucidate the involvement of lamin B1 Subjects: A multigenerational French Canadian family with ADLD mimicking progressive multiple sclerosis was in myelination and in degenerative disorders such as identified and studied. Eight affected family members were ADLD and multiple sclerosis. available for the study and presented with autonomic dys- function as well as upper motorneuron signs affecting gait. Arch Neurol. 2008;65(11):1496-1501 EREDITARY LEUKODYSTRO- Autosomal dominant adult-onset leu- phies are genetic disor- kodystrophy mimicking multiple sclero- ders that affect mainly the sis (MS) is an adult-onset leukodystrophy cerebral white matter. characterized by autonomic dysregula- The most common forms tion, pyramidal signs, and cerebellar dys- Hare childhood-onset diseases with a reces- function. The main feature is symmetrical sive inheritance pattern. Several mutant primary demyelination in the central ner- genes leading to biochemical abnormali- vous system of patients that is visible on ties have been identified as the cause of computed tomographic scans or magnetic these recessive leukodystrophies includ- resonance images. This disease was first Author Affiliations: Centre of 4 Excellence in Neuromics, Centre ing arylsulfatase A, galactocerebrosidase, described by Eldridge et al, and several Hospitalier de l’Universite´ and very-long-chain fatty acids. More re- families with ADLD from different ethnic de Montreal and Ste-Justine cently, the subunits of the eukaryotic ini- origins have since been described, namely Hospital, Montreal (Drs Meijer, tiation factor 2B, an important transla- 2 Irish American,5 1 Swedish,6 4 Japa- Lopes, Verlaan, and Rouleau and tion initiation factor, have been linked to nese,7-10 1 French,11 and 1 Italian12 family. Mss Laurent and Katz); Centre vanishing white matter disease (OMIM These families generally presented in the Hospitalier Affilie´ Universitaire 603896) and childhood ataxia with cere- same way except for the autonomic fea- de Quebe´c–Hoˆpital bral hypomyelination.1 tures, which were only reported for cer- de l’Enfant-Je´sus, Department of The known causes of autosomal domi- tain families with ADLD.6 Linkage studies Neurological Sciences, Universite´ nant adult-onset leukodystrophy (ADLD) initially localized the gene to chromo- Laval, Que´bec City (Drs Dupre´, 2 13 Thibault, and Bouchard); Centre were reviewed by Baumann and Turpin and some 5q31. Further fine mapping in the Hospital Affilie´Hoˆtel-Dieu many are late-onset forms of the childhood Swedish family narrowed down the candi- de Le´vis, Department of leukodystrophies. Two X-linked forms, Peli- date region to a 1.5–megabase pair (Mb) re- Radiology, Le´vis, Quebec, zaeus-Merzbacher disease and adrenoleu- gion on chromosome 5q23 between mark- Canada (Dr Mathurin). kodystrophy, have also been described.2,3 ers D5S1495 and CT/CCT15. (REPRINTED) ARCH NEUROL / VOL 65 (NO. 11), NOV 2008 WWW.ARCHNEUROL.COM 1496 ©2008 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/26/2021 During a candidate gene analysis, Padiath et al5 iden- 6% denaturing polyacrylamide gels and visualized on autora- tified 3 tandem duplications in the ADLD candidate re- diographic film. Key markers were initially genotyped in and gion by means of single-nucleotide polymorphism (SNP) around the ADLD locus, followed by more extensive fine map- ping. Linkage analysis was performed using the MLINK pro- sequence-peak comparisons. In the study, they pre- 20 sented 4 families including 2 Irish American families with gram of the LINKMAP software package (National Institutes of Health, Bethesda, Maryland) assuming equal recombina- a common ancestor and 2 Japanese families. The bor- tion frequency; a disease frequency of 1/1000 persons; age li- ders of 2 of the 3 duplications were determined; they ability classes of 0-46 years, 50% penetrance; older than 47 years, spannedapproximately341 kilobase pairs (kb) and169 90% penetrance; and a phenocopy rate of 0. Haplotype con- kb, respectively. The duplicated regions consistently con- struction assuming minimal recombination was performed tained 3 genes: LMNB1, FLJ36242, and MARCH3.5 manually and ordered according to the goldenpath physical map Lamin B1 (LMNB1) belongs to the family of lamins (UCSC Genome Browser; http://www.genome.ucsc.edu/). (LMNA, LMNB1, and LMNB2), which are type V inter- mediate filaments in the nuclear lamina.14 However, the function of LMNB1 has not been well characterized. Mice MUTATION DETECTION deficient in LMNB1 die shortly after birth and display bone and lung abnormalities.15 On a molecular level, the nuclear Genomic primers were designed to amplify the 18 candidate genes (LOX, ZNF474, SNCAIP, SNX24, SNX2, PRDM6, membrane of the deficient mouse embryonic fibroblasts CCDC100, CSNK163, ZNF608, KIAA1281, GRAMD3, ALDH7A1, showed nuclear blebs possibly due to impaired cellular RNUXA, LMNB1, MARCH3, MEGF10, FLJ00410, PRRC1) found differentiation. Overexpression of the fly ortholog, la- within the extended candidate interval. All coding exons and min DMo as well as a human LMNB1 transgene in a Dro- at least 50 base pairs of the flanking intronic sequence were sophila melanogaster model using different drivers showed amplified. Primer sequences will be made available on re- increased lethality, most notably in the glial-specific quest. Polymerase chain reaction products were sequenced at model.5 Mutations have also been described in other lam- the Genome Quebec Centre for Innovation. ins; for example, mutations in LMNA cause different types More specifically, primers for the LMNB1 gene were de- signed to amplify the 11 exons, including the complete 5Ј and of muscular dystrophies, lipodystrophy, and premature Ј aging diseases. Similar phenotypes were also found in 3 untranslated regions. The samples tested included 2 affected individuals, 1 control (a spouse), and hybrid cell line DNA de- LMNA-null mice. Interestingly, LMNB1 is ubiquitously rived from individual R17697 (patient IV:9) (GMP genetics Inc, expressed throughout development, whereas LMNA is Waltham, Massachusetts).21 The hybrid cell line allowed us to only expressed in differentiated cells. Mutations in LMNB2 analyze the affected allele of chromosome 5 in isolation. are associated with acquired partial lipodystrophy.16 In Using comparative genomic hybridization technology per- addition, the autosomal dominant Pelger-Huet anomaly formed by Nimblegen Systems, Inc (Madison, Wisconsin), 2 is caused by reduced expression of the LMNB receptor, individuals were also tested for copy-number variants.22 The 2 which affects neutrophil nuclear shape and chromatin samples were compared with a reference sample consisting of distribution in a dose-dependent manner.17 These dis- pooled DNA from 6 healthy individuals. The analysis of SNP eases are called laminopathies and are caused by muta- peaks visible on sequence traces was also performed to con- tions in the nuclear lamins.14,18 In this study we present firm the extent of the duplication. A list of analyzed SNPs will be made available on request. a French Canadian family with ADLD, a likely laminopa- thy, in which anapproximately280-kb duplication on chromosome 5q23 has been identified. RESULTS METHODS CLINICAL DATA Figure 1 shows the multigenerational French Cana- SUBJECTS dian family with ADLD with autosomal dominant seg- Informed written consent was obtained from subjects to par- regation in 16 affected members over 3 generations. In- ticipate in the study, which was approved by the local ethics terestingly, an affected branch of the family also carries review board of the Centre Hospitalier de Charlevoix, where a disease allele for the sacsin-encoding gene; therefore all of the subjects were recruited. Peripheral blood samples were individual IV:1 was affected with both ADLD and auto- obtained from 21 individuals including 8 affected family mem- somal recessive spastic ataxia of Charlevoix-Saguenay bers.