THE ETS TRANSCRIPTION FACTORS ENCODED BY THE DROSOPHILA GENE POINTED DIRECT GLIAL-CELL DIFFERENTIATION IN THE EMBRYONIC CNS

The Drosophila gene pointed (pnt) encodes two putative transcription f actors (P1 and P2) of the Ets family, which in the embryonic CNS are f ound exclusively in glial cells. Loss of pnt function leads to poorly differentiated glial cells and a marked decrease in the expression of the neuronal antigen 22C10 in the MP2 neurons, which are known to inte ract intimately with the pnt(P1)-expressing longitudinal glial cells. Ectopic expression of pnt(P1) RNA forces additional CNS cells to enter the glial differentiation pathway. Interestingly, the additional glia l-like cells are often flanked by cells that ectopically express the n euronal antigen 22C10. Therefore, both the pnt loss-of-function as wel l as the gain-of-function phenotype suggest that glial cells are able to induce 22C10 expression on neighboring neurons. This was further ve rified by cell transplantation experiments. Thus, pnt is not only requ ired but also sufficient for several aspects of glial differentiation.