No description available.

No description available.

No description available.

Clouston hidrotic ectodermal dysplasia (BED) is an autosomal dominant skin disorder that is characterized by nail dystrophy, hair defects and palmoplantar hyperkeratosis. This condition has been described in families of various ethnic origins but is particularly common in the French Canadian population. Using linkage analysis in eight French Canadian families segregating HED, we mapped the HED gene to the pericentromeric region of chromosome 13q with a combined two-point lod score of 8.12 at zero recombination from the marker D13S175. Haplotype analysis allowed us to define D13S143 as the telomeric flanking marker for the HED candidate region. We tested five genes that map to this region, connexin 26, connexin 46, fibroblast growth factor 9, zinc-finger ZNF198 and alpha tubulin TUBA2, for involvement in HED by PCR-SSCP analysis. No mutation specific to HED was found in any of them suggesting that they most likely are not defective in this disease. / To facilitate the identification of the HED gene, we constructed a radiation hybrid (RH) map of 48 loci surrounding the HED locus on chromosome 13q. This map integrates 3 genes (TUBA2, GJbeta2 and FGF-9) and 18 ESTs with 27 markers including 19 polymorphic loci. A major inconsistency in order involving a reversed interval of six loci was found between our RH map and a YAC contig established in the region. We used Fiber-FISH and FISH on interphase nuclei to confirm our order. To refine the localization of the HED gene, we isolated eight new chromosome 13q polymorphic (CA)n markers and used seven of them along with three others in genetic analysis of a multiethnic group of 29 HED families. We demonstrated genetic homogeneity in HED in four families of French, Spanish, African and Malaysian origins and showed evidence for a strong founder effect in families of French Canadian origin. Recombination mapping placed the HED gene in a 2.4 cM region flanked by D13S1828 proximally and D13S1830 distally. Multipoint linkage and linkage disequilibrium analyses finely mapped the HED gene at 0--0.08 cM telomeric to D13S1835. These studies will greatly facilitate the physical mapping and positional cloning of the HED gene.