A -96C-T mutation in the promoter of the collagen type VII gene (COL7A1) abolishing transcription in a patient affected by recessive dystrophic epidermolys bullosa

Hereditary dystrophic epidermolysis bullosa (DEB) refers to a group of clinically heterogeneous skin blistering diseases due to mutations in the collagen type VII gene (COL7A1). We report two novel mutations found in a patient affected by the most severe form of DEB, the recessive Hallopeau-Siemens variant (HS-RDEB): the R1978X nonsense mutation, in exon 72, and the -96C-->T transition, in the promoter region. The allele specific analysis of the transcripts from skin fibroblasts of the patient showed that the -96C-->T mutation is associated to the absence of collagen type VII (COLVII) mRNA. This mutation, the first one ever identified in the promoter of COL7A1, falls in an Sp1 motif, localized between nucleotides -96 and -91. Gel shift analysis indicated that the -96/-91 sequence is a functional Sp1 site and that the -96C-->T transition inhibits the binding of the trascription factor. These data indicate that the -96/-91 sequence is a crucial Sp1 site whose integrity is necessary for COL7A1 expression. The compound heterozygosity for the -96C-->T null mutation and for the R1978X mutation leads to the absence of COLVII at skin level and to the severe phenotype of the HS-RDEB patient.