Abstracts Biological Sciences

Cloning and sequencing ofpushover, a Drosophila gene affecting neuronal activity and glial morphology

by Stephen Richards

pushover (push) is a mutation that causes neuronal hyperexcitability, uncoordination and male sterility. Here it is also shown that push mutant wandering third instar larvae exhibit segmental nerves that are slightly thickened compared to wild type controls. The additional thickness of these nerves is due to a thicker perineural glia layer surrounding the axon bundle of the nerve. From investigation of push mutant testes, it was determined that mature sperm are produced, but are immotile. The push gene was cloned and sequenced and encodes a 5322 amino acid protein with 12 putative transmembrane helices. Sequencing of the push gene in the push 1 mutant line revealed a premature stop codon at amino acid position 728 and in push2 a premature stop codon at position 883. In situ hybridization experiments show push is expressed in the embryonic CNS and in primary spermatocytes in the adult testes and suggest that push is not expressed in the perineural glia of wandering third instar larvae. Because push affects but is not expressed in these glia, it is hypothesized that push is involved in a signaling pathway connecting the motor neuron to the perineural glia.