MUTATION OF THE DROSOPHILA SODIUM-PUMP ALPHA-SUBUNIT GENE RESULTS IN BANG-SENSITIVE PARALYSIS

A bang-sensitive enhancer trap line was isolated in a behavioral scree n. The flies show a weak bang-sensitive paralysis, recovering after ab out 7 s. The P element insert is localized at 93B1-2 on the salivary c hromosomes, the site of the (Na+,K+)ATPase alpha subunit gene. Molecul ar characterization demonstrates that the transposon is inserted into the first intron of this gene. This insertion leads to normal-sized tr anscripts, but reduced levels of expression. This change is also refle cted in lower amounts of a normal-sized a subunit protein. Mutant flie s show a much greater sensitivity to ouabain, likewise indicating, on a functional level, a reduction in Na+ pump activity. Furthermore, the bang-sensitive behavior can also be mimicked by injecting sublethal d oses of ouabain into wild-type flies. The molecular and functional evi dence indicates that the insertion has produced a hypomorphic mutation of the (Na+,K+)ATPase alpha subunit gene, opening the way to future s tudies of the regulation of the Na+ pump.