The membrane-bound proteins of the voltage gated chloride channel (CLC) family perform crucial roles in stabilising membrane potentials, transepithelial transport, cell volume regulation and acidification of intracellular organelles. Mammals have nine CLCs clustering into three subgroups and disruption of some members result in four notable human diseases; Dent’s disease, Bartter’s syndrome, osteopetrosis and congenital muscle myotonia. The Drosophila genome encodes three CLCs, corresponding to each of the mammalian CLC subgroups.

This study focuses on the functional characterization of the fly CLC-b (hCLC-6-7) and CLC-c (hCLC-3-5). Null mutations have been generated in both these genes. CLC-b^- homozygotes are adult viable but have impaired locomotory activity, a median longevity less than half that of heterozygotes and a pronounced sensitivity to elevated dietary zinc levels. Histological analysis of the CLC-b^- mutant central nervous system will be presented, investigating whether Drosophila lacking CLC-b display signs of Lysosomal Storage Disorders. In contrast, CLC-c^- homozygotes cease to develop beyond 2^nd instar larvae. Mosaic analysis indicated that cells homozygous for the CLC-c mutation have an increased LysoTracker signal prior to being replaced by surrounding heterozygous cells 3-5 days after clone generation. This implies an increase in lysosome production, typically seen in the initiation of autophagy, in the absence of CLC-c. A detailed analysis of the cellular defects caused by loss of CLC-c prior to cell death will be presented.

This research will use the power and flexibility of Drosophila genetics to elucidate the in vivo function of this critical class of Chloride Channel genes and will in future allow us to model the effect of human pathogenic mutations in the fly.