p54c-ets-1 and p68c-ets-1, the two transcription factors encoded by the c-ets-1 locus, are differentially expressed during the development of the chick embryo.

The chicken c-ets-1 proto-oncogene encodes two transcription factors, p54c-ets-1 and p68c-ets-1, which contain the same DNA-binding domain but differ in their transactivating activities. We have investigated the spatial and temporal distribution of the transcripts encoding p54c-ets-1 and p68c-ets-1 throughout the development of the chick embryo. We report that p68c-ets-1 as well as p54c-ets-1 is expressed in a wide variety of cells of mesodermal origin, including endothelial cells and mesenchymal cells interacting with epithelium. However, whereas p54c-ets-1 transcripts are detected in most cells, p68c-ets-1 transcripts are restricted to a subset of these cells, randomly distributed. In contrast, p54c-ets-1 is expressed in the absence of p68c-ets-1 in T and B lymphocytes. We show that, during erythropoiesis, both p68c-ets-1 and p54c-ets-1 are expressed in immature erythroid cells in extraembryonic blood islands. The pattern of expression of p54c-ets-1 and p68c-ets-1 during embryonic development suggests the involvement of these transcription factors in the regulation of morphogenetic processes. In addition, we provide the first clue that p68c-ets-1, the cellular progenitor of the v-ets oncogene, is expressed in erythroid cells. This result is very important with respect to the properties of the v-ets oncogene, which confers on the retrovirus E26 the ability to transform erythroid cells.