Topic
Synpolydactyly-1
About: Synpolydactyly-1 is a research topic. Over the lifetime, 3 publications have been published within this topic receiving 67 citations.
Papers
TL;DR: A large consanguineous family from Pakistan with SPD showing a wide variation in phenotype is analyzed, and the first nonsense mutation in the HOXD13 gene underlying a severe form of SPD in the homozygous state is revealed, and a milder version of SPD with ∼50% penetrance in the heterozygousState is shown.
Abstract: Synpolydactyly 1 (SPD1; OMIM 186000), also known as type II syndactyly, is a dominantly inherited limb malformation that is characterized by an increased number of digits. SPD1 is most commonly caused by polyalanine repeat expansions in the coding region of the HOXD13 gene, which are believed to show a dominant-negative effect. In addition, missense and out-of-frame deletion mutations in the HOXD13 gene are also known to cause SPD, and the mechanism responsible for the phenotype appears to be haploinsufficiency. Here, we analyzed a large consanguineous family from Pakistan with SPD showing a wide variation in phenotype among affected individuals. We performed genetic linkage analysis, which identified a region on chromosome 2 containing the HOXD13 gene. Haplotype analysis with microsatellite markers suggested segregation of the phenotype with HOXD13 gene with incomplete penetrance. Direct sequencing analysis of HOXD13 gene revealed a nonsense mutation, designated as Q248X. All affected individuals with the severe SPD phenotype are homozygous for the mutation, whereas those with the mild SPD phenotype are heterozygous for the mutation. Furthermore, some unaffected individuals also carry the mutation in the heterozygous state, showing incomplete penetrance. Our results show the first nonsense mutation in the HOXD13 gene underlying a severe form of SPD in the homozygous state, and a milder form of SPD with ∼50% penetrance in the heterozygous state, most likely because of the production of 50% of protein compared with normal individuals.
28 citations
TL;DR: A splice donor site mutation in HOXD13 associated in most cases with cortical bone thinning is reported and truncated protein analysis indicated that c.781+1G>A mutation results in truncated HOxD13 protein p.G190fsX4.
6 citations
TL;DR: It is noted that metacarpal and metatarsal involvement and middle phalangeal hypoplasia of the feet are the consistent features of SPD and should be considered as characteristic of this phenotype.
Abstract: A very large Turkish family with syndactyly type II (synpolydactyly (SPD)) is described, which originated from and is mainly concentrated in the village of Derbent, Afyon. The kindred consists of 425 subjects over seven generations, of whom 182 are affected. It appears that a founder effect in this village has led to this extensive kindred. This condition is inherited as an autosomal dominant trait with variable expressivity and an estimated penetrance of 96%. Penetrance is different between the upper (96%) and lower (69.5%) extremities. No excess of affected males or females or other associated features were documented in this condition. Variations in the involvement of one or both hands, upper or lower extremities, bone and soft tissue, as well as variation in the affected subjects of two successive generations were documented. We also noted that metacarpal and metatarsal involvement and middle phalangeal hypoplasia of the feet are the consistent features of SPD and, therefore, should be considered as characteristic of this phenotype. We observed four different phenotypes in various branches of the Derbent kindred: (1) subjects presenting typical features of SPD; (2) subjects exhibiting both pre- and post-axial polydactyly simultaneously; (3) persons manifesting postaxial polydactyly type A; and (4) subjects born to two affected parents with severe hand and foot deformities that have not been previously described in any other SPD families (that is, homozygotes). A total of 27 affected offspring were born to two such affected parents, of whom seven are expected to be homozygous for the SPD gene. This group is presented in an accompanying paper in this issue of the Journal. A molecular study is currently under way to identify the chromosomal location of the defective gene.
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2013 | 1 |
| 2011 | 1 |
| 1995 | 1 |