Genomic amplification of the human plakophilin 1 gene and detection of a new mutation in ectodermal dysplasia/skin fragility syndrome.

Ectodermal dysplasia/skin fragility syndrome is a recently described autosomal recessive disease affecting skin, nails, and hair (MIM 604536), that results from mutations in plakophilin 1, a structural component of desmosomes. We report a new plakophilin 1 mutation in an affected patient as well as detailing the intron-exon organization of the gene to facilitate future polymerase chain reaction-based mutation screening. Using polymerase chain reaction amplification of genomic DNA, we identified 15 exons spanning approximately 50 kb. Direct sequencing disclosed several nonpathogenic intragenic polymorphisms, as well as a homozygous splice site mutation (1233-2 A-->T; GenBank Z73678) in a 17 y old affected male. The clinical features comprised skin erosions, dystrophic nails, sparse hair, and painful thickening and cracking of palms and soles. Skin biopsy showed negative immunolabeling with an anti-plakophilin 1 antibody and small desmosomes. These results expand the database of plakophilin 1 mutations and demonstrate the importance of this protein in the stabilization of desmosomal adhesion in terminally differentiating keratinocytes.