Splicing modulation of integrin beta 4 pre-mRNA carrying a branch point mutation underlies epidermolysis bullosa with pyloric atresia undergoing spontaneous amelioration with ageing

A general improvement with ageing has been reported in a few cases of epide rmolysis bullosa with pyloric atresia (PA-JEB), an autosomal recessive skin disease characterized by extensive disadhesion of epithelia, In a patient who improved from severe to mild PA-JEB, a search for mutations in the inte grin beta 4 gene (IGTB4) detected heterozygosity for a novel base substitut ion 3986-19T-->A in the putative branchpoint sequence of intron 31, and a p oint mutation 3802+1G-->A in the donor splice site of intron 30 previously associated with severe PA-JEB, Analysis of mRNA showed that the intronic mu tation prevents legitimate splicing of the beta 4 pre-mRNA. Functional spli cing can be restored in vitro by seeding the proband's keratinocytes an fee ders of irradiated fibroblasts, Study of mRNA in wild-type keratinocytes tr ansfected with IGTB4 minigenes containing intron 31 with or without mutatio n 3986-19T-->A, confirmed the causative role of the intronic mutation in PA -JEB, and highlighted the influence of feeders on the maturation process of the mutated beta 4 pre-mRNA, Our results show that in a context of overall reduction of the beta 4 mRNA levels, activation of the legitimate splice s ite in the aberrant beta 4 pre-mRNA underlies the transient severity of the condition, The results also point to the relevance which the interaction b etween epithelial and stromal cells may have in modulating expression of in tegrin receptors.