Institut für Entwicklungsbiologie, Universität zu Köln, D-50923 Köln,
Glial cells perfom important functions during the formation of the axonal network. In the embryonic CNS glial cell differentiation requires the spitz group gene pointed. pointed encodes two putative transcription factors, P1 and P2, which share an ETS DNA binding domain. pointed P1 is expressed in lateral glia cells and acts as a transcriptional activator. In order to understand its function during glial cell differentiation we are analysing possible glial specific target genes of pointed. With the help of the enhancer trap technique we have identified loco, a gene that is specifically expressed in embryonic CNS glial cells. In a subset of these, expression of loco is dependent on POINTED function. Using promoter-reporter fusion constructs a POINTED-dependent enhancer element has been localised to a 1 kb region of genomic DNA. loco encodes a cyptoplasmatically localised protein that is a member of the recently described RGS (regulators of G-protein signalling) family. To assess its function in CNS glia cells, we have analysed excision mutants and X-ray induced loco alleles as well as the consequences of ectopic expression of loco.