ISOLATION AND CHARACTERIZATION OF A PUTATIVE KERATIN-ASSOCIATED PROTEIN GENE EXPRESSED IN EMBRYONIC SKIN OF MICE

Embryonic mouse skin undergoes substantial morphologic changes from 13 days post-coitus (dpc) to 16 dpc, i.e., from simple layers of epithel ial cells and periderm at 13.5 dpc to almost fully differentiated stra tified epithelium with the rudiments of hair follicles at 16.5 dpc. Us ing RNA differential display, we isolated a gene involved in the devel opment of mouse epidermis, This gene, tentatively designated as 4C32, encodes 197 amino acids containing six direct repeats of 10 amino acid s with the CQ motif, The repetitive structure with the CQ motif is see n in most keratin-associated protein families, which are known to be s pecifically expressed in hair follicles, 4C32 is expressed in the oute rmost layer of the embryonic epidermis at 15.5 and 16.5 dpc, and abrup tly disappears at 17.5 dpc, suggesting that 4C32 is expressed in the p eriderm. The periderm is a superficial layer of embryonic epidermis, a nd is known to disappear at 17 dpc in mouse embryos. The 4C32 transcri pts were also detected in the developing and matured tongue tissues an d in the tail scale, but not at any stage in hair follicles.