ß 2008 Wiley-Liss, Inc.
American Journal of Medical Genetics Part A 146A:3034 – 3037 (2008)
Geroderma Osteodysplastica Maps to a 4 Mb Locus on Chromosome 1q24 William G. Newman,1,2* Jill Clayton-Smith,1,2 Kay Metcalfe,2 Rachel Cole,2 Marco Tartaglia,3 Francesco Brancati,4,5 Sara Morara,4 Antonio Novelli,4 Xiangdong Liu,6,7 Katherine A. Siminovitch,6,7 Stefan Mundlos,8 May Tassabehji,1 and Graeme C.M. Black1,2 1
Academic Department of Medical Genetics, University of Manchester, Manchester, UK 2 Regional Genetics Service, St Mary’s Hospital, Manchester, UK 3 Dipartimento di Biologia Cellulare e Neuroscienze, Istituto Superiore di Sanita`, Rome, Italy 4 CSS Mendel Institute, Rome, Italy 5 Department of Biomedical Sciences, Ce.S.I., G. d’Annunzio University, Chieti, Italy 6 Department of Medicine, University of Toronto and Mount Sinai Hospital, Toronto, Canada 7 Department of Immunology and Medical Genetics and Microbiology, University of Toronto and Mount Sinai Hospital, Toronto, Canada 8 Institut fu¨r Medizinische Genetik Charite´, Universita¨ts-Medizin Berlin, Berlin, Germany Received 20 March 2008; Accepted 28 August 2008
Important insights into the etiology of osteoporosis have been gained by the study of single gene disorders, including osteogenesis imperfecta. We report on the genetic mapping of geroderma osteodysplastica (GO), a rare autosomal recessive disorder of the connective tissue, characterized by wrinkly skin and severe osteoporosis. We undertook autozygosity mapping in one Libyan and four consanguineous Pakistani families with a total of 10 affected individuals to define a 4 Mb homozygous region on chromosome 1q24, which harbors the GO causative gene. No obvious candidate
genes that encode known protein constituents of the extracellular matrix are found in the linked region. Importantly, our study demonstrates that GO is not allelic to wrinkly skin syndrome caused by mutations in ATP6V0A2. ß 2008 Wiley-Liss, Inc.
Key words: geroderma osteodysplastica; autozygosity; chromosome 1q24; osteoporosis; wrinkly skin
How to cite this article: Newman WG, Clayton-Smith J, Metcalfe K, Cole R, Tartaglia M, Brancati F, Morara S, Novelli A, Liu X, Siminovitch KA, Mundlos S, Tassabehji M, Black GCM. 2008. Geroderma osteodysplastica maps to a 4 Mb locus on chromosome 1q24. Am J Med Genet Part A 146A:3034–3037.
INTRODUCTION
Geroderma osteodysplastica (GO; OMIM 231070) is a rare autosomal recessive disorder of the connective tissue. Clinical features include wrinkled, lax skin present at birth, precocious aging of the skin, a characteristic facial appearance due to flattening of the malar and maxillary bones, hyperextensible joints and severe osteoporosis with vertebral deformity and fractures [Al-Gazali et al., 2001]. Phenotypic overlap with wrinkly skin syndrome (OMIM 278250) and cutis laxa with developmental delay (OMIM 219200) has been described [Al-Gazali et al., 2001; Nanda et al., 2008], with osteoporosis a more characteristic feature of GO. Recently, mutations in the vesicular Hþ-ATPase subunit ATP6V0A2 on chromosome 12q24 have been identified as the cause of both wrinkly skin syndrome and cutis laxa with developmental delay [Kornak et al., 2008], but the underlying genetic etiology of GO has yet to be
determined. No previous mapping studies have been published on GO to determine if the conditions are allelic or discrete entities. We undertook an autozygosity mapping on one Libyan and four Pakistani families to define the genetic basis of GO. METHODS
To map the GO locus, we employed autozygosity mapping, a powerful technique to define chromosomal loci containing causative genes underlying Grant sponsor: Manchester NIHR Biomedical Research Centre; Grant sponsor: Italian Ministry of Health; Grant number: Ricerca Corrente 2008. *Correspondence to: Dr. William G. Newman, Department of Medical Genetics, St Mary’s Hospital, University of Manchester, Manchester M13 0JH, UK. E-mail:
[email protected] Published online 12 November 2008 in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/ajmg.a.32564
American Journal of Medical Genetics Part A
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GERODERMA OSTEODYSPLASTICA LINKS TO 1q24
recessive conditions in consanguineous families [Gibbs and Singleton, 2006]. In the Libyan family, we genotyped 380 microsatellite markers covering the whole genome, at an average distance of 10 cM (ABI PRISM Linkage Mapping Set, version 2) in the three affected individuals. After amplification, following the manufacturer’s instructions, markers were run on an automated DNA sequencer (ABI PRISM 3100) and analyzed using GeneMapper software. Haplotypes were manually constructed, and phase was assigned based on the smallest number of recombinants. Physical distances between markers were taken from the University of California Santa Cruz draft of the human genome, release ‘‘March 2006,’’ available at www.genome.ucsc.edu. To refine the upper and lower limits and saturate the linked region, eight novel polymorphic markers (named on the basis of chromosome position, type and number of repeat, i.e., D1S24CA) were selected from the Human Genome Working Draft using the Tandem Repeat Finder software (primers and conditions are available on request). For each pair, the forward primer
was fluorescently labeled with either a FAM or a HEX dye. The position of these novel markers on the physical map of human chromosome 1 is reported in Figure 1 for Family E. Concurrently, in the Pakistani families, only the affected individuals were genotyped using a single nucleotide polymorphism (SNP) array approach. Array experiments were performed according to the Affymetrix GeneChip Mapping 50K array standard protocol (Affymetrix, Inc., Santa Clara, CA). The Mapping 50K array is designed to hybridize labeled PCR fragments from XbaI-cleaved DNA detecting 58,960 SNPs. We obtained a minimum call rate of 92.6%. Ethical approval for the study was obtained from the University of Manchester (06138) and NHS ethics committee (06/Q1406/52). RESULTS
We ascertained 10 individuals affected with GO in five families (Fig. 1). Seven patients from four families lived in the North West of England. All four
FIG. 1. Simplified pedigrees of five consanguineous Pakistani (A–D) and Libyan (E) families with individuals affected by GO (filled in symbols) with haplotypes at the chromosome 1q24 locus. For Families A–D, the linked region is shown based on the genotypes observed at the single nucleotide polymorphisms (SNP) included in the Affymetrix GeneChip Mapping 50K array (positions on the physical map according to the dbSNP build 128). Note the minimum region of homozygosity among all the five families (highlighted in gray) flanked by SNPs rs1200150 and rs9286879 (bold). For Family E, the locus is delimitated by markers D1S24AC and D1S24CA (bold and black bars). Positions were taken from the human reference chromosome 1 sequence (NCBI Build 36.1). The arrow indicates the proband; numbers in parentheses are inferred genotypes.
American Journal of Medical Genetics Part A
22 M þþ þ 160 (>3rd) þ B þ NA NA Scoliosis 19 M þþ þ 139 (10th) þ B þþ NA þ NA 14 M þþ þþ 170 (25th) þþ þþ þ Torticollis 17 F þþ þþ 157 (25th) þ þ NA þ NA 1 F þ 53 (