Analysis of Neprilysins 1-5 in Drosophila melanogaster reveals parallels between mammalian and invertebrate roles in reproductive fitness. J. Sitnik³, C. Francis^1,2, R. Huybrechts⁴, M. Wolfner³, P. Callaerts^1,2. 1) Laboratory of Behavioral and Developmental Genetics, KULeuven, Leuven, Belgium; 2) VIB Center for the Biology of Disease, Leuven, Belgium; 3) Dept. of Molecular Biology and Genetics, Cornell University, Ithaca NY, USA; 4) Zoological Institute, KULeuven, Leuven, Belgium.

   Members of the M13 class of metalloproteases have been implicated in a variety of diseases including cardiovascular disorders and Alzheimer's. In addition to their importance in human disease, some members of this zinc-metalloprotease family are expressed in human reproductive tissues. Further, they have been shown play a role in reproductive fitness for both male and female mice. Beyond the role of one family member, Neprilysin, in degrading tachykinins in the uterus and the sperm of mammals, very little is known about how these proteases regulate reproduction. We sought to use Drosophila as a model to dissect this. The Drosophila melanogaster genome contains 24 M13 class protease homologs, some of which are orthologs of human proteases including Neprilysin and are expressed in the reproductive tracts of either sex. Using RNAi we individually targeted each of the 5 Drosophila Nep genes (Nep1-5) to determine their importance in reproduction. Reducing expression of Nep1 or Nep2 in the CNS or spermathecae of females causes a reduction in egg-laying; expression of Nep2 in females is also important for the hatchability of laid eggs. Females homozygous for a null mutation in Nep2 also show defects as hosts of sperm competition, suggestive of roles for female-derived Nep2 in sperm storage or utilization. Reducing expression of Nep1-5 in males did not cause dramatic fertility defects which suggests that these genes may not be essential for reproductive fitness in the male or that they may overlap in function. Our results are in support for a reproductive role for Neprilysin members of the M13 class of metalloproteases, particularly in the female. Further work is needed to elucidate the roles of the other 19 M13 class homologs in reproduction.