Mushroom body defect, a gene involved in the control of neuroblast proliferation in Drosophila, encodes a coiled-coil protein

Neurogenesis relies on the establishment of the proper number and precisely controlled proliferation of neuroblasts, the neuronal precursor cells. A r ole for the mushroom body defect (mud) gene in both of these aspects of neu roblast behavior, as well as possible roles in other aspects of fruit fly b iology, is implied by phenotypes associated with mud mutations. We have loc alized mud by determining the sequence change in one point mutant, identify ing a predicted ORF affected by the mutation, and showing that an appropria te segment of the genome rescues mud mutant phenotypes. An analysis of mud cDNAs and a survey of mud transcripts by Northern blotting indicate that th e gene is subject to differential splicing and is expressed primarily durin g embryogenesis but also, at lower levels, during subsequent developmental stages in a sexually dimorphic manner. The gene is predicted to encode a po lypeptide without obvious homologs but with two prominent structural featur es, a long coiled coil that constitutes the central core of the protein and a carboxyl-terminal transmembrane domain.