Spatial, temporal, and sexually dimorphic expression patterns of the fruitless gene in the Drosophila central nervous system

The fruitless (fru) gene of Drosophila produces both ses-specifically and n on-sex-specifically spliced transcripts. Male-specific fru products are bel ieved to regulate male courtship. To further an understanding of this gene' s behavioral role, we examined the central nervous system (CNS) for tempora l, spatial, and sexually dimorphic expression patterns of sex-specific fru products by in situ hybridization and immunohistochemistry. For the latter, antibodies were designed to detect only male-specific forms of the protein (FRUM) or amino acid sequences that are in common among all translated pro ducts (FRUCOM). Sex-specific mRNAs and male-specific proteins were first ob served in mature larvae and peaked in their apparent abundances during the first half of the pupal period. At later stages and in adults, faint mRNA s ignals were seen in only a few neural clusters; in contrast, relatively str ong FRUM signals persisted into adulthood. Twenty neuronal groups composed of 1700 fru-expressing neurons were identified in the midpupal CNS, These g roups overlap most of the neural sites known to be involved in male courtsh ip. Anti-FRUCOM tell to widespread labeling of neural and nonneural tissues in both sexes, but in the female CNS, only in developing ganglia in a patt ern different from that of the male's FRUM cells. Expression of sex-specifi c fru mRNAs in the CNS of males analyzed from the earliest pupal stages ind icated that sex-specific alternative splicing is not the exclusive mechanis m regulating expression of fruitless transcripts. (C) 2000 John Wiley & Son s, Inc.