Institut fuer Genetik, Freie Universitaet Berlin, Arnimallee 7, 14195 Berlin,
Using the established enhancer-trap method to screen for genes showing specific expression in the brain cells of third larvae we have isolated a gene that is expressed in the whole CNS of the embryo and larvae, at least.
By northern analysis a specific 3.5kb transcript could be detected during all developmental stages; with the highest amount of transcript being observed during early pupal development. The amount of RNA (detected by in situ hybridization) and protein (detected by specific antibodies) is particularly high in the cells of the mushroom bodies and both RNA and protein can be detected from stage 14 embryos on. The gene encodes a putative single stranded nucleic acid binding protein that shows high similarity to a family of vertebrate RNA binding proteins containing the KH domain. Some of these proteins have been isolated as the protein part of abundant nuclear RNPs. Because of preferred binding to purine rich sequences they are thought of being nonspecific splicing factors. The most prominent member of this family the FMR1 protein causes "Fragile X Syndrome" if RNA binding is impaired by a mutation in the KH domain. At least two functional KH domains in these proteins have been reported to be necessary for proper binding of RNA or single stranded DNA in vitro. A specific function of two proteins as transcription factors by binding to single stranded DNA within the upstream region of the myc-gene has also been reported. Therefore the isolated gene may encode either a splicing or transcription factor necessary for tissue specific splicing/regulation of a ubiquitously expressed gene.