The neuron-enriched splicing pattern of Drosophila erect wing is dependenton the presence of ELAV protein

Although the Drosophila melanogaster erect wing (ewg) gene is broadly trans cribed in adults, an unusual posttranscriptional regulation involving alter native and inefficient splicing generates a 116-kDa EWG protein in neurons, while protein expression elsewhere or of other isoforms is below detection at this stage. This posttranscriptional control is important, as broad exp ression of EWG can be lethal, In this paper, we show that ELAV, a neuron-sp ecific RNA binding protein, is necessary to regulate EWG protein expression in ELAV-null eye imaginal disc clones and that ELAV is sufficient for EWG expression in wing disc imaginal tissue after ectopic expression. Further, analysis of EWG expression elicited from intron-containing genomic transgen es and cDNA minitransgenes in ELAV-deficient eye discs shows that this regu lation is dependent on the presence of ewg introns. Analyses of the ewg spl icing patterns in wild-type and ELAV-deficient eye imaginal discs and in wi ld-type and ectopic ELAV-expressing wing imaginal discs, show that certain neuronal splice Isoforms correspond to ELAV levels. The data presented in t his paper are consistent with a mechanism in which ELAV increases the splic ing efficiency of ewg transcripts in alternatively spliced regions rather t han with a mechanism in which stability of specific splice forms is enhance d by ELAV, Additionally, we report that ELAV promotes a neuron-enriched spl ice isoform of Drosophila armadillo transcript, ELAV, however, is not invol ved in all neuron-enriched splice events.