Ets-1 and Ets-2 proto-oncogenes exhibit differential and restricted expression patterns during Xenopus laevis oogenesis and embryogenesis

Xenopus Xl-ets-1 and Xl-ets-2 are maternally expressed. From late oogenesis to early embryogenesis their transcripts are localized to the animal pole and the intermediate zone, suggesting a function in the differentiation of animal blastomeres and future mesoderm. Their presence at the level of germ plasm suggests also a role in the differentiation of the germinal lineage. Both zygotic genes are expressed ubiquitously beginning at MET, and then restricted to a circumblastoporal collar. In neurula and tailbud stages, ets-1 and ets-2 transcripts are detected in neural crest cells and their derivatives. Specific transcription can also be observed for ets-1 in the hemangioblastic precursors, in endothelial cells of the forming heart and blood vessels. Ets-P is itself specifically expressed in the putative pronephros and in the forming pronephric tubules and extending pronephric duct. Like another member of the ets-gene family (Xl-fli), both genes are transcribed in regions of the embryo undergoing important morphogenetic modifications, especially in migrating cells and/or along their migration pathways. We postulate that these genes orchestrate modifications of cellular adhesion. Changes in the expression of cadherins and integrins repertories would be consistent with such a role and could account for the phenotypes we reported earlier for Xl-fli overexpression. Such a role would be critical for tumor cell dissemination, in addition to the one already ascribed to ets-1 in the expression of proteases specific for the extracellular matrix.