The Ets-transcription factor family in embryonic development: lessons fromthe amphibian and bird

This chapter reviews the expression and role of Ets-genes during embryogene sis of amphibians and birds. In addition to overlapping expression domains, some of them exhibit cell type-specific expression. Many of them are expre ssed in migratory cells: neural crest, endothelial and pronephric duct cell s for instance. They are also transcribed in embryonic areas affected by ep itheliomesenchymal transitions. Both processes involve modifications of cel lular adhesion. Ets-family genes appear to coordinate changes in the expres sion of adhesion molecules and degradation of the extracellular matrix upon regulation of matrix metalloproteinases and their specific inhibitors. The se functions are essential for physiological processes like tissue remodell ing during embryogenesis or wound healing. Unfortunately they also play a h armful role in metastasis. Recent studies in the nervous system showed that Ets-genes contribute to the establishment of a cellular identity. This ide ntity could rely on definite cell-surface determinants, among which cadheri ns could play an important role. In addition to cell-type specific expressi on, other factors contribute to the specificity of function of Ets-genes, T hese genes have a broad specificity of recognition of target sequences in g ene promoters, insufficient for accurate control of gene expression. A fine tuning could arise from combinatorial interactions with other Ets- or acce ssory proteins.