Identification and characterisation of novel genes involved in neural cell fate specification/asymmetric cell division during the development of the Drosophila embryonic nervous system The generation of cellular diversity is a fundamental process in the development of multicellular organisms. The understanding of asymmetric cell division has come mainly from studies involving the early embryonic development of the nematode C. elegans and the CNS development of the fruit fly Drosophila melanogaster. Although a number of proteins which localise to the apical cortex of Drosophila neuroblasts have been identified which are required to facilitate their asymmetric divisions, many questions still remain as to how these proteins interact with the cell cortex and control the downstream processes of mitotic spindle orientation as well as the asymmetric localisation and segregation of cell fate determinants. Other proteins so far unidentified are likely to be involved in these processes. I propose to conduct a mutagenesis screen using the Drosophila melanogaster neuroblasts as a model to identify novel genes involved in asymmetric cell division of the early embryonic CNS. The main problem associated with identifying novel proteins using this model system is the high levels of maternally contributed protein that could allow normal divisions in an apparent mutant background. I intend to use the FLP/FRT system in conjunction with the dominant female sterile insert P[ovoD] to create germline clones within the female germline which will remove the maternally contributed protein. Embryos generated from the germline clones will be assessed to see what effects they have on asymmetric cell divisions as judged by immunohistochemical analysis using a variety of molecular markers for the developing embryonic CNS. The novel genes identified in the screen will be characterised with respect to their role in localising the previously identified proteins involved in asymmetric cell division, as well as on coordinating mitotic spindle orientation. Genetic epistasis studies will be conducted to determine where they lie within the hierarchy of genes already known to be involved in the process. In addition, molecular and biochemical studies will be performed to determine the nature of the gene products and their likely mechanisms of action. The screen is likely to produce a number of novel candidate genes involved in asymmetric cell division, which will extend our current understanding of this field. The novel genes identified from this screen will likely help elucidate presently unanswered questions within this field. Specifically, addressing how do these proteins localise to specific regions on the cell cortex, the mechanism involved in the localisation and maintainance at this site, and also identifying the links between the apically localised protein complex and the mitotic spindle.