ID GENES ENCODING INHIBITORS OF TRANSCRIPTION ARE EXPRESSED DURING IN-VITRO ASTROCYTE DIFFERENTIATION AND IN CELL-LINES DERIVED FROM ASTROCYTIC TUMORS

Id proteins belong to a class of nuclear transcription factors known a s helix-loop-helix proteins, It has been reported that Id genes functi on as negative regulators of differentiation, and Id gene expression i s downregulated during cell differentiation. We examined the regulatio n of Id genes during astrocyte differentiation in a murine nervous sys tem precursor cell line, NSEHip2-28, which is able to differentiate al ong the astroglial lineage, as well as in human astroglial tumor cell lines. Upon induction of NSEHip2-28 differentiation, at a time when gl ial fibrillary acidic protein expression became detectable, the expres sion of all four Id family members initially increased dramatically, a nd subsequently decreased. Furthermore, varying levels of Id gene expr ession were found in astroglial tumor cell lines displaying variable d egrees of lineage-specific differentiation. These results suggest that the expression of Id family members may play an important role in the control of astrocyte differentiation.