Midkine and Pleiotrophin are secreted, heparin-binding proteins implicated in diverse developmental processes, yet their in vivo functions remain incompletely understood. This dissertation investigates the roles of their Drosophila homologues, miple1 and miple2. Expression analyses show that miple1 is enriched in central nervous system glia and neurons, while miple2 is expressed in embryonic tissues, larval imaginal discs, and adult gonads. Functional studies using a miple2-null mutant reveal that Miple2 is not required for Anaplastic lymphoma kinase signaling and shows no definitive role in major developmental pathways, including Wingless/Wnt, Hedgehog, and Dpp/TGFβ. Notably, loss of miple2 causes male sterility due to defective sperm individualization, indicating a critical role in spermatogenesis.
