C-FES EXPRESSION IN ONTOGENIC DEVELOPMENT AND HEMATOPOIETIC DIFFERENTIATION

The c-fes protein (NCP92) is a tyrosine-specific protein kinase, capab le of both autophosphorylation and phosphorylation of other substrates . We have analysed c-fes RNA expression in human/murine ontogenetic de velopment and in homogenous populations of embryonic and adult human h ematopoietic cells. c-fes expression has been observed in rapidly prol iferating embryonic-fetal tissues originating from different germinal layers, but not in adult non-hematopoietic tissues. In particular, a s patially and temporally regulated transcription was observed in the ce ntral nervous system and in developing cartilage. Expression in hemato poietic cells was evaluated in progenitors purified from embryonic-fet al liver and adult peripheral blood differentiating gradually and spec ifically along the erythroid or granulomonocytic lineage. In both embr yonic and adult hematopoietic cells c-fes was abundantly expressed in undifferentiated progenitors of both lineages, as well as in different iated granulomonocytic precursors, but not in erythroblasts. This expr ession pattern correlates with that of GM-CSF and in part IL-3 recepto rs (Testa et al., 1993 and our unpublished results). Altogether, these results suggest a possible role for c-fes in signal transduction, in both embryonic non-hematopoietic tissues and embryonic/ adult hematopo ietic cells, following interaction of growth factors with their tyrosi ne-kinase negative receptors (i.e., GM-CSF and IL-3 receptors in adult hematopoietic cells and other hypothetical growth factor(s) receptors during embryonic development).