1. ^*Department of Dermatology and Cutaneous Biology, Jefferson Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
2. ^†Department of Pathology, Anatomy and Cell Biology, Jefferson Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
3. ^§Department of Biochemistry and Molecular Pharmacology, Jefferson Medical College, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
4. ^‡Max-Planck Institute for Biochemistry, Munich, Germany

Correspondence: Jouni Uitto MD PhD, Department of Dermatology and Cutaneous Biology, Jefferson Medical College, 233 S. 10th Street, Suite 450 BLSB, Philadelphia, PA 19107. Email: Jouni.Uitto@Jefferson.edu

Received 12 February 2003; Revised 16 April 2003; Accepted 13 May 2003.

Abstract

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 3-, 3-, and 2-chains, respectively. Here we generated a mouse model for JEB by inactivating the laminin 2-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 2-chain on the basement membrane zone as well as attenuated expression of 3- and 3-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 2-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.