Splicing abnormality of integrin β4 gene (ITGB4) due to nucleotide substitutions far from splice site underlies pyloric atresia-junctional epidermolysis bullosa syndrome

Background: Pyloric atresia-junctional epidermolysis bullosa syndrome (PA-JEB) is a rare subgroup of epidermolysis bullosa, which is inherited disorder characterized by skin fragile. PA-JEB is caused by mutation of ITGB4 or ITGA6, which encodes integrin β4 or α6, respectively. Objective: To clarify the molecular basis of PA-JEB and to expand the mutational database, we carried out the mutational analysis of a 29-year-old Japanese PA-JEB patient. Methods: Standard methods were used to prepare, PCR-amplify, and sequence DNA or mRNA in peripheral blood or skin samples, respectively. Results: Sequence analysis revealed two novel mutations in ITGB4, c.264+2TtoA and c.1762-25TtoA. The paternal c.264+2TtoA resided within a splice site consensus region and generated two splice variants resulting in a premature termination codon (PTC). The maternal c.1762-25TtoA was a unique mutation because of its location, 25. bp away from the splice site, and resided in branch-point consensus sequence. This c.1762-25TtoA substitution resulted in generation of two abnormal transcripts each with a PTC. Genotype-phenotype correlation in this case was also unique because the proband showed a non-lethal phenotype regardless of both mutations resulted in only abnormal transcripts with a PTC. Conclusion: The present case expands the mutational database and further elucidates the genotype-phenotype correlation for this rare disease, PA-JEB.