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Mapping one form of autosomal dominant postaxial polydactyly type A to chromosome 7p15-q11.23 by linkage analysis.

ABSTRACT: Postaxial polydactyly type-A (PAP-A) in humans is an autosomal dominant trait characterized by an extra digit in the ulnar and/or fibular side of the upper and/or lower extremities. The extra digit is well formed and articulates with the fifth, or extra, metacarpal/metatarsal, and thus it is usually functional. In order to map the gene responsible for PAP-A, we studied a five-generation Indian family of 37 individuals (15 of whom were affected). A genomewide search with highly informative polymorphic markers on part of the pedigree showed linkage between the PAP-A phenotype and markers on chromosome 7p15-q11.23 (no crossovers were found with D7S526, D7S795, D7S528, D7S521, D7S691, D7S667, D7S478, D7S1830, D7S803, D7S801, or ELN). The highest LOD score was obtained with marker D7S801 (zeta max = 4.21; theta = 0). Haplotype analysis enabled the mapping of the PAP-A phenotype in this family between markers D7S2848 and D7S669. Analysis of additional families with PAP-A will narrow down the critical genomic region, facilitate positional cloning of the PAP-A gene, and/or uncover potential genetic heterogeneity.

SUBMITTER: Radhakrishna U

PROVIDER: S-EPMC1712530 | biostudies-other | 1997 Mar

REPOSITORIES: biostudies-other

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Mapping one form of autosomal dominant postaxial polydactyly type A to chromosome 7p15-q11.23 by linkage analysis.

Radhakrishna U U Blouin J L JL Mehenni H H Patel U C UC Patel M N MN Solanki J V JV Antonarakis S E SE

American journal of human genetics 19970301 3

Postaxial polydactyly type-A (PAP-A) in humans is an autosomal dominant trait characterized by an extra digit in the ulnar and/or fibular side of the upper and/or lower extremities. The extra digit is well formed and articulates with the fifth, or extra, metacarpal/metatarsal, and thus it is usually functional. In order to map the gene responsible for PAP-A, we studied a five-generation Indian family of 37 individuals (15 of whom were affected). A genomewide search with highly informative polymo ...[more]

PMID: 9042919

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Project description:The osteopetroses are a heterogeneous group of conditions characterized by a bone-density increase due to impaired bone resorption. As well as the two or more autosomal recessive types, two autosomal dominant forms of osteopetrosis, differentiated by clinical and radiological signs, are described. Autosomal dominant osteopetrosis (ADO) type II, also known as "Albers-Schönberg disease," is characterized by sclerosis, predominantly involving the spine (vertebral end-plate thickening, or Rugger-Jersey spine), the pelvis ("bone-within-bone" structures), and the skull base. An increased fracture rate can be observed in these patients. By linkage analysis, the presence, on chromosome 1p21, of a gene causing ADO type II was previously suggested. However, analysis of further families with ADO type II indicated genetic heterogeneity within ADO type II, with the chromosome 1p21 locus being only a minor locus. We now perform a genomewide linkage scan of a French extended family with ADO type II, which allows us to localize an ADO type II gene on chromosome 16p13.3. Analysis of microsatellite markers in five further families with ADO type II could not exclude this chromosomal region. A summed maximum LOD score of 12.70 was generated with marker D16S3027, at a recombination fraction (straight theta) of 0. On the basis of the key recombinants in the families, a candidate region of 8.4 cM could be delineated, flanked by marker D16S521, on distal side, and marker D16S423, on the proximal side. Surprisingly, one of the families analyzed is the Danish family previously suggested to have linkage to chromosome 1p21. Linkage to chromosome 16p13.3 clearly cannot be excluded in this family, since a maximum LOD score of 4.21 at theta=0 is generated with marker D16S3027. Because at present no other family with ADO type II has proved to have linkage to chromosome 1p21, we consider the most likely localization of the disease-causing gene in this family to be to chromosome 16p13.3. This thus reopens the possibility that ADO type II is genetically homogeneous because of a single gene on chromosome 16p13.3.

Dataset Information

Mapping one form of autosomal dominant postaxial polydactyly type A to chromosome 7p15-q11.23 by linkage analysis.

Publications

Mapping one form of autosomal dominant postaxial polydactyly type A to chromosome 7p15-q11.23 by linkage analysis.

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