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 epithelial cells and periderm at 13.5 dpc to almost fully differentiated stratified epithelium with the rudiments of hair follicles at 16.5 dpc. Using RNA differential display, we isolated a gene involved in the development of mouse epidermis. This gene, tentatively designated as 4C32, encodes 197 amino acids containing six direct repeats of 10 amino acids with the CQ motif. The repetitive structure with the CQ motif is seen in most keratin-associated protein families, which are known to be specifically expressed in hair follicles. 4C32 is expressed in the outermost layer of the embryonic epidermis at 15.5 and 16.5 dpc, and abruptly disappears at 17.5 dpc, suggesting that 4C32 is expressed in the periderm. The periderm is a superficial layer of embryonic epidermis, and is known to disappear at 17 dpc in mouse embryos. The 4C32 transcripts were also detected in the developing and matured tongue tissues and in the tail scale, but not at any stage in hair follicles.