Skin abnormality in aged fyn-/- fak+/- mice.

Focal adhesion kinase (FAK) is a novel non-receptor protein tyrosine kinase implicated in transducing signals from cell surface receptors. Its association with Fyn, a member of the Src family of tyrosine kinases, has been observed in cell lines. To examine in vivo the interaction between these two proteins, Fyn-deficient mice were bred with fak heterozygous mutants (Fak deficiency is embryonic lethal). A majority of animals with the double mutation (fyn-/- fak+/-) displayed a transient impairment in thymocyte development at four weeks of age. However, all of them developed skin abnormalities at the age of 8-12 months. The most prominent among abnormalities was a greatly increased number and size of sebaceous glands. Also, the epidermis was thickened and hyperkeratotic. These observations would suggest involvement of Fyn and FAK in keratinocyte differentiation.