The role of MRNIP and Cfap97d1 in male fertility

Male fertility relies on the testis producing large quantities of normal sperm through the intricate process of spermatogenesis. The goal of spermatogenesis is to produce genetically unique male gametes capable of fertilizing an ovum and producing offspring. It is a highly complex temporal event, where the developing germ cells undergo transformative changes from primitive spermatogonial stem cells to large meiotic spermatocytes, dividing into smaller round spermatids and ultimately becoming streamlined compact sperm. This thesis focuses on uncovering and determining the significance of MRN complex interacting protein (Mrnip) and Cfap97 domain containing 1 (Cfap97d1), two poorly characterized genes in the process of spermatogenesis.
We investigated the importance of Mrnip in meiosis I of spermatogenesis. Our findings unveil Mrnip as a sexually dimorphic gene specific to male meiosis, with its deletion resulting in infertility in male mice. Mrnip-/- mice have significantly reduced testes size and weight. Deletion of Mrnip causes a series of defects throughout spermatogenesis, resulting in a block in meiosis progression and the absence of mature and motile sperm (azoospermia), thereby rendering males infertile. Building on these findings, we used biochemical and biophysical methods to characterize the human recombinant MRNIP protein (hMRNIP). We assessed the evolutionary conservation of hMRNIP and provided experimental evidence that hMRNIP is largely an intrinsically disordered protein with a structured N-terminal domain that contains zinc. Lastly, we explored the role of the uncharacterized Cfap97d1 in the spermiogenesis phase of spermatogenesis. We show that deletion of Cfap97d1 leads to sperm motility defects (asthenozoospermia) resulting in subfertility in male mice. Our work demonstrates for the first time that Cfap97d1 is important in maintaining the structural integrity of the sperm flagellum and male fertility. Based on our findings the protein was renamed to ‘Sperm axoneme maintenance protein CFAP97D1’.
Together, these studies contribute to revealing the functions of genes that play pivotal roles in the establishment and maintenance of male fertility.