Requirement for Ubiquitin C-Terminal Hydrolase function in mammalian ovarian health and fertility - PROJECT SUMMARY Approximately 20% of reproductive age women are affected by infertility, with a shocking one third of all cases considering idiopathic, or “unexplained”. Diminished function of the mammalian ovarian reserve is one potential cause of infertility, as it is a finite and non-renewable population of the female gametes (“oocytes”) representing the entire reproductive capacity of a female. These cells also support the endocrine function of the ovary, with their premature depletion resulting in an inability to conceive, as well as other features of aging including an increased risk of ischemia, and overall shorter lifespan. Therefore, understanding and preserving this essential population is critical for female fertility, longevity and quality of life. The goals of this proposal are founded upon our single cell sequencing work elucidating novel regulators of ovarian reserve establishment. We identified deubiquitinating enzyme Ubiquitin C-Terminal Hydrolase-L1 (UCHL1) as highly enriched in mouse and human oocytes during ovarian reserve formation, eventually achieving a steady-state level of expression through later-stage follicle development. Furthermore, we can detect and measure secreted UCHL1 in mouse and human serum, as well as human follicular fluid, suggesting additional paracrine and endocrine signaling roles for UCHL1. Indeed, female mice that lack UCHL1 expression are severely sub-fertile, with morphologically abnormal oocytes, defects in folliculogenesis, and apparent systemic endocrine dysfunction. Our preliminary data also suggest deficits in the ability of UCHL1 deficient oocytes to properly form the zona pellucida and express gap junction proteins. Therefore, we hypothesize that UCHL1 is required for oocyte quality via regulation of zona pellucida protein turnover and assembly, and therefore oocyte-granulosa cell communication as well as systemic endocrine function. This proposal vastly expands upon our initial work to characterize the role of UCHL1 in maintaining oocyte quality as well in regulating ovarian proteostasis and ubiquitin dynamics (Aim 1). We will also elucidate the tissue-specific roles of UCHL1, including how oocyte-specific UCHL1 affects ovarian development, reproductive lifespan and may act in a paracrine manner to promote ovarian somatic cell health and overall endocrine function (Aim 2). These studies will achieve three goals: 1) determine the role of UCHL1 in maintaining oocyte quality through regulation of zona pellucida and gap junction formation 2) comprehensively test the effects of oocyte-specific UCHL1 loss on granulosa cell health and systemic endocrine function, and 3) conclusively elucidate the role of oocyte-expressed UCHL1 in regulating female reproductive lifespan, oocyte and granulosa cell proteostasis, and ovarian gene expression programs. This proposal will not only help us better understand the unique oocyte- and granulosa-cell-specific functions of potentially master regulator of ovarian function, UCHL1, but also will help us refine our understanding of the critical roles of proteostasis in female reproductive health, as well as the interdependence between overall ovarian health and oocyte quality.
