Genetic analysis of the epidermal differentiation complex (EDC) on human chromosome 1q21: chromosomal orientation, new markers, and a 6-Mb YAC contig.

The epidermal differentiation complex (EDC) unites a remarkable number of structurally, functionally, and evolutionarily related genes that play an important role in terminal differentiation of the human epidermis. It is localized within 2.05 Mb of region q21 on human chromosome 1. We have identified and characterized 24 yeast artificial chromosome (YAC) clones by mapping individual EDC genes, sequence-tagged site (STS) markers (D1S305, D1S442, D1S498, D1S1664), and 10 new region-specific probes (D1S3619-D1S3628). Here we present a contig that covers about 6 Mb of 1q21 including the entire EDC. Fluorescence in situ hybridization on metaphase chromosomes with two YACs flanking the EDC determined its chromosomal orientation and established, in conjunction with physical mapping results, the following order of genes and STSs: 1cen-D1S442-D1S498-S100A10-THH-FLG- D1S1664-IVL-SPRR3-SPRR1-SPRR2-LOR- S100A9-S100A8-S100A7-S100A6-S100A5-S100 A4- S100A3-S100A2-S100A1-D1S305-1qtel. These integrated physical, cytogenetic, and genetic mapping data will be useful for linkage analyses of diseases associated with region 1q21 and for the identification of novel genes and regulatory elements in the EDC

A missense mutation in connexin26, D66H, causes mutilating keratoderma with sensorineural deafness (Vohwinkel's syndrome) in three unrelated families.

The multiplicity of functions served by intercellular gap junctions is reflected by the variety of phenotypes caused by mutations in the connexins of which they are composed. Mutations in the connexin26 (Cx26) gene ( GJB2 ) at 13q11-q13 are a major cause of autosomal recessive hearing loss (DFNB1), but have also been reported in autosomal dominant deafness (DFNA3). We now report a Cx26 mutation in three families with mutilating keratoderma and deafness [Vohwinkel's syndrome (VS; MIM 124500), as originally described]. VS is characterized by papular and honeycomb keratoderma associated with constrictions of digits leading to autoamputation, distinctive starfish-like acral keratoses and moderate degrees of deafness. In a large British pedigree, we have mapped the defect to the Cx26 locus. All 10 affected members were heterozygous for a non-conservative mutation, D66H, in Cx26. The same mutation was found subsequently in affected individuals from two unrelated Spanish and Italian pedigrees segregating VS, suggesting that D66H in Cx26 is a common mutation in classical VS. This mutation occurs at a highly conserved residue in the first extracellular domain of the Cx26 molecule, and may exert its effects by interfering with assembly into connexons, docking with adjacent cells or gating properties of the gap junction. Our results provide evidence that a specific mutation in Cx26 can impair epidermal differentiation, as well as inner ear function