A large number of cell types are found in the vertebrate brain but there is little understanding of how this diversity is controlled at the genetic level. To identify regulatory factors that govern neuronal phenotype, we wish to utilise as a starting point a gene whose expression is characteristic of a particular neuronal cell type. The gene encoding the a6 subunit of GABAA receptors serves as a unique marker for differentiated cerebellar granule cells. No expression is found in other brain regions, or in peripheral tissues. My research plan centres around defining the DNA regulatory regions (enhancers/silencers) of the a6 subunit gene using transgenic mice, and mapping DNase I hypersensitive sites. The transcription factors that act on these sites could turn out to be of general importance, and may direct cellular differentiation in a variety of neuronal tissues.