A phospholipid flippase essential for olfactory neuron function in Drosophila . Coral G. Warr, Yu-Chi Liu, Takahiro Honda, Michelle Pearce, Marien de Bruyne. School of Biological Sciences, Monash University, Clayton, VIC, Australia.

   In Drosophila the majority of general odorants are detected by a large family of 62 seven-transmembrane receptor proteins, the odorant receptor (Or) family. To identify new genes involved in Or and olfactory receptor neuron (ORN) function in Drosophila we used electro-antennogram recordings to screen 883 lines from the Zuker collection, a collection of EMS-treated homozygous viable lines1. We identified a recessive mutation that has greatly reduced electro-antennogram responses to all tested general odorants, but not to carbon dioxide. Olfactory sensillum and ORN morphology appear normal in the mutant. The mutation was deficiency mapped to a region at 86E-87B on chromosome III that contained 12 predicted genes. We performed whole genome re-sequencing on the mutant strain and identified a nonsense mutation in one of the 12 genes, CG14741. We also observed the mutant phenotype in a second independent mutant allele of CG14741, a line containing a piggybac transposable element insertion in the coding region, confirming this is the affected gene. Both mutations are predicted to affect all four known isoforms of the protein. RNA in situ hybridisation experiments showed expression of CG14741 in ORNs, and using RNA interference we have shown that this gene is specifically required in ORNs for their function. CG14741 has not previously been functionally characterised but encodes a phospholipid flippase, type 4 P-type ATPases that translocate phospholipids from the exoplasmic to the cytoplasmic leaflet of plasma and internal membranes, and is highly similar to the human flippases ATP8B1-4. We are currently performing further studies to determine how lack of this protein is affecting ORN function.
    1. Koundakjian, E., et al. (2004).The Zuker Collection: A Resource for the Analysis of Autosomal Gene Function in Drosophila melanogaster. Genetics, 167: 203-206.