The role of enhancer of split and groucho during neurogenesis in Drosophila melanogaster and Musca domestica

This study has investigated the role of the E(spl) and groucho genes during neural fate commitment in the fly. It is known that the carboxy-terminal tryptophan-arginine-proline-tryptophan (WRPW) motif of E(spl) binds Groucho to form a complex, which represses the transcription of target genes. The importance of specific residues within WRPW has been investigated by generating a number of mutant derivatives containing single amino acid substitutions within the motif. It has been found that changes in WRPW abolish the in vivo function of the protein, and attenuate interaction with the Groucho protein. To determine the mode of E(spl)-mediated regulation, a series of co-expression assays were performed. E(spl) has been ectopically co-expressed with proneural genes scute or daughterless during allocation of imaginal SOP cells. It was found that E(spl) did repress the neural fate in the context of the co-expression assay, suggesting that, in addition to transcriptional repression of the proneural genes, post-transcriptional modes of regulation also occur. The requirement for an intact WRPW motif further suggest that this mode of repression may involve Groucho. Finally, a region of the groucho gene from the housefly (Musca domestica) has been cloned which encodes the C-terminal WD40 repeats and part of the variable region and displays a high degree of identity with Drosophila Groucho in these regions. In the Musca blastoderm embryo groucho mRNA is ubiquitously expressed, but later becomes confined to the developing CNS. A preliminary functional analysis using the technique of RNA interference suggests that groucho plays a role during neurogenesis in the Musca embryo.