7. PROJECT SUMMARY Small RNAs, including microRNAs, have been shown to play critical roles in the regulation of gene expression in the germ line. However, the specific pathways and targets regulated by individual microRNAs in the process of spermatogenesis remain largely unknown. The identification of direct targets regulated by individual microRNAs remains a central challenge in the field. In this grant, we propose to identify direct targets of germline microRNAs that function in the regulation of spermatogenesis. We are using the model system of C. elegans, which has been instrumental in defining the core principles of individual microRNA regulation of targets in developmental pathways. In prior work, we and others have identified the set of microRNAs that are expressed in C. elegans germ cells and somatic gonad cells. Additionally, we have identified a set of microRNAs that function to regulate sperm formation. However, the pathways and targets that they regulate remain largely uncharacterized. This work will address two central questions: 1) What are the target mRNAs that associate with a germline specific Argonaute protein? 2) How does regulation by microRNAs through the 3’ UTR of target mRNAs act to control spermatogenesis? This work will provide a foundation for future investigation to comprehensively define the microRNA targets that act in the germ line to regulate the process of spermatogenesis.

8. PROJECT NARRATIVE MicroRNAs are indispensable regulators of gene expression that are required for animal development and physiology. In addition, microRNAs have been implicated in a wide spectrum of human diseases, notably cardiovascular disease, neurodegenerative disease, and cancer. We are using the genetically tractable organism, C. elegans, to identify the pathways and targets that are regulated by microRNAs.