TRANSCRIPTION OF THE NEUROGENIC GENE MASTERMIND DURING DROSOPHILA DEVELOPMENT

The neurogenic loci of Drosophila encode the components of a cell comm unication pathway that operates during multiple developmental stages a nd in numerous tissues. Activation of the pathway is required for inhi bitory interactions, during partitioning of cells into alternative pat hways of differentiation. Genetic studies of these loci have demonstra ted numerous interactions, suggesting a close relationship among the g ene products; molecular studies have corroborated some of these ideas. The mastermind (mam) locus shows genetic interactions with several ne urogenic loci, yet its role in this pathway is unknown. We have analyz ed mam transcription and further characterized the phenotype associate d with mam alleles. mam is widely expressed in patterns overlapping th ose of other neurogenic loci during embryonic and postembryonic develo pment; embryonic transcription is not dependent upon function of neuro genic genes. mam transcription is widespread during most of embryogene sis; however, late embryonic expression appears limited to the nervous system. Central nervous system expression persists at high levels dur ing larval and pupal stages. Widespread transcription is also observed in ovaries and imaginal discs, with enhanced levels just anterior to the morphogenetic furrow of the eye disc. Phenotypic analyses of mam m utations demonstrate a broad phenotypic range and suggest that particu lar alleles disturb features of the CNS unrelated to neural overgrowth . (C) 1996 Wiley-Liss, Inc.