enok encodes a Drosophila putative histone acetyltransferase required for mushroom body neuroblast proliferation

Mushroom bodies in the Drosophila brain are centers for olfactory learning and memory. We have previously shown that the mushroom bodies comprise thre e types of neurons with distinct axonal projections. These three types of n eurons are generated sequentially from common neuroblasts [1], We report he re the identification of a gene that we have named enoki mushroom (enok), w hich when it is mutated gives rise to mushroom bodies with reduced axonal s tructures. enok encodes a putative histone acetyltransferase (HAT) of the M YST family, members of which have been implicated as important modulators o f transcriptional activity [2]. A single amino acid change in the zinc fing er motif of the putative catalytic HAT domain gives the same phenotype as a null allele, and this finding indicates the importance of HAT activity to Enok's function. Further phenotypic analysis demonstrates that the mushroom body defect is due to an arrest in neuroblast proliferation rather than a failure of either cell fate switching or axon branching. Clonal analyses in the wing discs and the ovaries suggest that enok is essential for normal c ell proliferation in some, but not all, tissues. Our results provide in viv o evidence for essential functions of a histone acetyltransferase in the co nstruction of the Drosophila brain.