Compound heterozygosity for missense (L156P) and nonsense (R554X) mutations in the beta4 integrin gene (ITGB4) underlies mild, nonlethal phenotype of epidermolysis bullosa with pyloric atresia

Abstract

Mutations in the genes encoding the subunit polypeptides of the alpha6beta4 integrin (ITGA6 and ITGB4, respectively) have been previously demonstrated in patients with a lethal form of epidermolysis bullosa with congenital pyloric atresia (OMIM #226730). In this study, we demonstrate for the first time ITGB4 mutations in nonlethal phenotype of epidermolysis bullosa with congenital pyloric atresia. Specifically, the proband was shown to be a compound heterozygote for a missense mutation (L156P) and a nonsense mutation (R554X). The leucine substitution by proline was shown to affect a residue, which was precisely conserved in different human, rodent, and drosophila integrin-beta polypeptides, and consequently disrupts the alpha-helix formation of the polypeptide segment as determined by Garnier alpha-helicity plot. The nonsense mutation in another allele was accompanied by undetectable levels of the corresponding mRNA transcript, as determined by reverse transcription-polymerase chain reaction. The presence of a missense mutation, when combined with a premature termination codon mutation, may explain the milder blistering tendency of the skin in this patient.