Identical Glycine Substitution Mutations in Type VII Collagen May
Underlie Both Dominant and Recessive Forms of Dystrophic Epidermolysis Bullosa
Noor Almaani, Lu Liu, Patricia J. C. Dopping-Hepenstal, Joey E. Lai-Cheong, Alvin Wong, Arti Nanda, Celia Moss, Anna E. Martinez, Jemima E. Mellerio, John A. McGrath
Autosomal dominant and recessive forms of dystrophic epidermolysis bullosa (DEB) result from mutations in the type VII collagen gene (COL7A1). Although paradigms have emerged for genotype/phenotype correlation in DEB, some pathogenic mutations in COL7A1, notably glycine substitutions within the type VII collagen triple helix, may lead to diagnostic difficulties, since certain glycine substitutions can result in either dominant or recessive mutant alleles. Delineation of glycine substitution mutations into two discrete groups, however, is made difficult by observations that, for some particular glycine substitutions in type VII collagen, the same mutation can result in both dominant and recessive disease. In this report we describe four further glycine missense mutations: p.Gly1483Asp, p.Gly1770Ser, p.Gly2213Arg and p.Gly2369Ser, which can lead to either dominant or recessive DEB, and which result in a spectrum of clinical abnormalities. We also identify a further 30 new glycine substitution mutations that cause either dominant or recessive DEB, but not both. In screening the COL7A1 gene for mutations in individuals with DEB our data highlight that delineation of glycine substitutions in type VII collagen has important implications for genetic counselling.