Pontin and Reptin are a pair of closely related proteins conserved throughout eukaryota. Although both are essential for viability in all species tested, their exact biochemical function in the cell remains unknown. Together, Pontin and Reptin associate with a diverse set of macromolecular complexes with various functions, but the two proteins also seem to act independently. Their role in development in multicellular organisms is of particular interest. In this project we aim at addressing the function and interactions of Pontin and Reptin in vivo through several interconnected approaches using Drosophila melanogaster as a model.  We have focused on the role of Pontin and Reptin in the nervous system as well as intracellular localization and interactions. Although both proteins are expressed in the nervous system of various species, no functional studies have been reported. Loss of Pontin or Reptin in the fly causes nervous system abnomalities, which merrit further investigation. In a previous study we found a conserved interaction between Pontin, Reptin and AAA+ ATPases of the proteasome. To study the localization and protein interactions of Pontin and Reptin in Drosophila we have generated fluorescent fusion constructs of Pontin, Reptin and their candidate interaction partners for conditional expression. We have analysed the intracellular distribution of these proteins in neuroblasts, neurons and epithelial cells, and co-localization studies are currently in process.