Mutations in the gene encoding SLURP-1 in Mal de Meleda.

Mal de Meleda (MDM) is a rare autosomal recessive skin disorder, characterized by transgressive palmoplantar keratoderma (PPK), keratotic skin lesions, perioral erythema, brachydactyly and nail abnormalities. We report the refinement of our previously described interval of MDM on chromosome 8qter, and the identification of mutations in affected individuals in the ARS (component B) gene, encoding a protein named SLURP-1, for secreted Ly-6/uPAR related protein 1. This protein is a member of the Ly-6/uPAR superfamily, in which most members have been localized in a cluster on chromosome 8q24.3. The amino acid composition of SLURP-1 is homologous to that of toxins such as frog cytotoxin and snake venom neurotoxins and cardiotoxins. Three different homozygous mutations (a deletion, a nonsense and a splice site mutation) were detected in 19 families of Algerian and Croatian origin, suggesting founder effects. Moreover, one of the common haplotypes presenting the same mutation was shared by families from both populations. Secreted and receptor proteins of the Ly-6/uPAR superfamily have been implicated in transmembrane signal transduction, cell activation and cell adhesion. This is the first instance of a secreted protein being involved in a PPK.