DROSOPHILA HOMEOBOX GENE EVE ENHANCES TROL, AN ACTIVATOR OF NEUROBLAST PROLIFERATION IN THE LARVAL CNS

The regulation of stem cell division by developmental cues is critical for the assembly and function of multicellular organisms. Stem cell d ivision in the Drosophila brain is controlled by trol, which is requir ed for activation of proliferation by quiescent neuroblasts at the app ropriate stage of larval development. We show that the transcriptional regulator eve is part of the trol activation pathway by identifying e ve as a dominant enhancer of a weak trol allele, trol(b22). Known eve mutations are capable of enhancing the lethality of trol(b22) and unco vering a defective neuroblast proliferation phenotype. Additionally ge netic and molecular analysis reveals that an independent mutation whic h acts as a dominant enhancer of trol is also an allele of eve. The en hancement of trol(b22) lethality can be suppressed by the presence of an eve transgene. interestingly extra copies of eve supplied by the ev e transgene also enhance trol(b22) lethality, suggesting that the leve l of Eve protein may be critical for neuroblast activation. Finally, a ctivation of neuroblast proliferation is normal in eve(4) hetero zygot es suggesting that the proliferation defect observed in trol(b22);eve/ + animals is due to a synergistic interaction. (C) 1998 Wiley-Liss, In c.