Structural Defects of Laminin β3 N-terminus Underlie Junctional Epidermolysis Bullosa with Altered Granulation Tissue Response

Mutations in the laminin-332 (alpha 3A beta 3 gamma 2) genes cause junctional epidermolysis bullosa (JEB), a recessively inherited disease characterized by blistering and altered wound repair. In addition, specific mutations that affect the N-terminus of the alpha 3A chain cause a JEB-related non-blistering condition characterized by chronic production of granulation tissue, suggesting a critical role of this region in epithelial-mesenchymal communication. We report here a 9-year-old patient with JEB with a few long-standing skin ulcers with prominent granulation tissue in the absence of active blistering. He bears a homozygous missense mutation, p.Gly254Asp, within the first laminin epidermal growth factor-like (LE) repeat of the beta 3 short arm. We show that p.Gly254Asp causes mis-folding of the LE motif, leading to reduced secretion of laminin-332 and structural alterations of the cutaneous basement membrane zone. These findings demonstrate, in a patient in vivo, that the beta 3 short arm is also involved in the outcome of the granulation tissue response.