Targeted Inactivation of Murine Laminin γ2-Chain Gene Recapitulates Human Junctional Epidermolysis Bullosa

Junctional forms of epidermolysis bullosa (JEB) are associated with mutations in six distinct genes expressed in the cutaneous basement membrane zone; these include LAMA3, LAMB3, and LAMC2, which encode laminin 5 subunit polypeptides, the α3-, β3-, and γ2-chains, respectively. Here we generated a mouse model for JEB by inactivating the laminin γ2-chain gene by targeted frameshift deletion of exon 8 in Lamc2. Heterozygous mice were phenotypically normal, whereas the majority of Lamc2-/- mice showed blistering phenotype on days 1 to 2 and died within 5 days of birth. The Lamc2-/- mice demonstrated absent expression of laminin γ2-chain on the basement membrane zone as well as attenuated expression of α3- and β3-chains of laminin. Transmission electron microscopy revealed rudimentary, poorly developed hemidesmosomes. The epidermis of the Lamc2–/– mice revealed induced apoptosis in the basal cells of the blistered skin, suggesting that cell-matrix adhesion provided by laminin 5 plays a role in cell survival in vivo . Cultured Lamc2–/– keratinocytes demonstrated slightly positive staining with γ2-chain-specific antibodies, which could be explained by the presence of a transcript with partial restoration of the reading frame owing to alternative splicing in vitro . These cells proliferated in different matrices and attached to type IV collagen and Matrigel as efficiently as the wild-type keratinocytes, whereas their attachment on plastic and laminin was significantly weaker. In summary, Lamc2–/– mouse recapitulates human JEB and provides novel insight into the role of laminin 5 in keratinocyte biology.