The Dowling-Meara variant of epidermolysis bullosa simplex (EBS-DM) is a severe blistering disease inherited in an autosomal-dominant fashion. Here we report the generation of a mouse model that allows focal activation of a mutant keratin 14 allele in epidermal stem cells upon topical administration of an inducer, resulting in EBS phenotypes in treated areas. Using laser capture microdissection, we show that induced blisters healed by migration of surrounding nonphenotypic stem cells into the wound bed. This observation provides an explanation for the lack of mosaic forms of EBS-DM. In addition, we show that decreased mutant keratin 14 expression resulted in normal morphology and functions of the skin. Our results have important implications for gene therapy of EBS and other dominantly inherited diseases.

No abstract

The Smads are the signaling mediators of the TGFb superfamily. In the present study, we examined Smad expression in mouse epidermis and chemically-induced skin tumors. Mutations in Smad2 and -4 genes were also screened. Transcripts of Smad1 through -5 were constantly expressed in the epidermis regardless of changes in TGFb signaling, state of dierentiation and stages of carcinogenesis. Smad7 transcripts were barely detectable in keratinocytes, but were induced by TGFb1 treatment and in chemically-induced skin tumors. At the protein level, Smad1 was detected throughout the epidermis, whereas Smad2 through -5 exhibited greater levels in suprabasal layers than basal keratinocytes. In cultured keratinocytes, Smad2, -3 and -4 underwent nuclear translocation upon TGFb1 treatment. Furthermore, nuclear translocation of Smads correlated with decreased BrdU labeling in proliferative keratinocytes. Although no mutations were detected in the Smad2 and -4 genes in tumors, proteins of Smad1 through -5 were partially or completely lost in carcinomas. These data document that Smads are expressed at high levels in the epidermis and mediate signaling of the TGFb superfamily. During skin carcinogenesis, loss of Smad1 through -5 and overexpression of Smad7 may contribute to the loss of growth inhibition mediated by TGFb superfamily members, thus resulting in tumor progression. Oncogene (2001) 20, 471 ± 483.

The rough coat (rc), an autosomal-recessive mutation, arose spontaneously in C57BL/6J mice. Homozygous rc mice develop severe skin and hair abnormalities, including cyclic and progressive hair loss and sebaceous gland hypertrophy. The rc locus was previously mapped to Chromosome 9. To elucidate the genetic basis underlying the rc phenotype development, we carried out positional cloning, and mapped the rc locus to a 246-kb interval. We identified a missense mutation within a novel open reading frame in the rc/rc mice, which is predicted to encode a cell adhesion molecule with the highest homology to myelin protein zero (MPZ) and myelin protein zero-like 2 (MPZL2, also called epithelial V-like antigen). We therefore named this gene Mpzl3 (myelin protein zero-like 3). The mutation in the rc/rc mice occurred at a highly conserved residue within the conserved Ig-like V-type domain, thus likely altering the MPZL3 protein function. Reverse transcriptase-PCR and Western blot analyses revealed expression of the Mpzl3 gene in various adult organs, including the skin. Using indirect immunofluorescence, we detected MPZL3 protein in the keratinocytes and sebocytes in the skin. Results from this study identified a novel gene encoding a predicted adhesion protein whose mutation in the rc/rc mice likely caused the rc phenotype.

No abstract