Epoc-1: a POU-domain gene expressed in murine epidermal basal cells and thymic stromal cells.

POU-domain transcription factors are known as developmental regulators which control organ development and cell phenotypes. In order to clarify the roles of POU-domain transcription factors in cell differentiation, we cloned a novel POU family gene, Epoc-1, from a murine thymus cDNA library. The amino acid (aa) sequence of the POU-specific domain of Epoc-1 is almost identical to those of Oct-1 and Oct-2. However, within the POU-homeodomain, 13 out of 60 aa differ between Epoc-1 and Oct-2. Recombinant Epoc-1 products were found to bind specifically to the octamer sequence. Epoc-1 was found to be expressed in skin, thymus, stomach and testis. In situ hybridization experiments and RNase protection assays indicated that Epoc-1 is expressed in the epidermal basal cells of the skin, which contain stem cells unipotent for keratinocyte differentiation and in thymic stromal elements. These results suggest that Epoc-1 might be one of the developmental regulators which controls epidermal development and thymic organogenesis.