Drosophila center divider gene is expressed in CNS midline cells and encodes a developmentally regulated protein kinase orthologous to human TESK1

The Drosophilla center diviner gene (cdi) was isolated in an enhancer trap screen undertaken to identify genes involved in embryonic central nervous s ystem (CNS) midline cell development. Three independent lines with P-elemen t insertions at 91F were analyzed that all showed prominent P-galactosidase expression in the CNS midline precursor cells and other cell types. Null m utations were created by imprecise P-element excision and shown to be larva l lethal, although no severe CNS defects were observed in mutant embryos. T he DNA surrounding the sites of insertion was cloned and found to contain a transcription unit that was dynamically expressed in a pattern correspondi ng to the enhancer trap line P-galactosidase expression. Sequencing of cDNA clones revealed that the cdi gene encodes a 1140-amino acid protein that i s an ortholog of the mammalian testis-specific TESK1 protein kinase. This s erine/threonine kinase is distinct from other protein kinases because of se quence differences in the residues conferring substrate specificity. The un ique sequence is conserved in Cdi, suggesting that Cdi/TESK1 represents a n ovel class of signaling proteins.