Long-lived cardiac myosins as regulators of oocyte cytoskeletal integrity and reproductive lifespan

The National Institute of Child Health and Human Development awarded the University of Pennsylvania $100,228 on January 1, 2027, under the Child Health and Human Development Extramural Research program (CFDA 93.865) to investigate long-lived cardiac myosins as regulators of oocyte cytoskeletal integrity and reproductive lifespan.

The research examines how exceptionally long-lived proteins—specifically A- and B-cardiac myosin heavy chain proteins (MHC-A/-B)—maintain oocyte cytoskeletal integrity across reproductive aging. The study maps spatiotemporal localization of these cardiac myosins relative to actin and microtubules using super-resolution imaging, characterizes their proteomic and transcriptomic context in germinal vesicle, metaphase I, and metaphase II oocytes, and identifies interacting partners via immunoprecipitation-mass spectrometry. The research determines whether MHC-A/-B are required for meiotic progression and characterizes the consequences of their depletion on oocyte developmental potential and reproductive capacity across lifespan. This work addresses the molecular mechanisms that preserve oocyte integrity during prolonged meiotic arrest, which remain poorly understood and not therapeutically targetable despite their relevance to pregnancy loss, aneuploidy, and congenital disorders associated with reproductive aging.

Work is performed in Philadelphia, Pennsylvania, with a period of performance from January 1, 2027, through August 31, 2029. This is a project grant, the assistance type supporting investigator-initiated biomedical research.

Abstract

Oocyte quality is a critical determinant of female fertility and healthy embryo development, yet IT declines markedly with age. This drastic decline contributes to pregnancy loss, aneuploidy, and congenital disorders, making reproductive aging a major health concern. This proposal seeks to define a novel cytoskeletal mechanism that governs key aspects of reproductive cell biology during developmental aging. Despite extensive studies determining canonical actin-myosin networks as essential for oocyte fidelity, the molecular mechanisms that preserve oocyte integrity across prolonged meiotic arrest remain poorly understood and not therapeutically targetable. Although most cytoskeletal proteins undergo rapid turnover, recent pulse-chase proteomic analysis revealed a surprising class of exceptionally long-lived proteins (ellps) in mammalian oocytes. This study identified MHC-α and MHC-β (α- and β-cardiac myosin heavy chain proteins), which are traditionally restricted to cardiac muscle and have not been previously studied in the oocyte. This discovery challenges current assumptions about oocyte proteostasis and suggests that long-lived cardiac myosins may sustain cytoskeletal integrity over the reproductive lifespan. The hypothesis of this study is that exceptionally long-lived α- and β- cardiac myosins (MHC-α/-β) integrate into oocyte actin networks to maintain cytoskeletal integrity and preserve developmental potential with age. Aim 1 will test this by mapping their spatiotemporal localization relative to actin and microtubules using super-resolution imaging. Then, the proteomic and transcriptomic context of cardiac myosins in GV, MI, and MII oocytes will be characterized and interacting partners will be identified via immunoprecipitation-mass spectrometry. Aim 2 will determine whether MHC-α/-β are required for meiotic progression and how their depletion affects oocyte maturation through pharmacological, protein, and gene expression modulation. Finally, the study will assess whether enhancing MHC-α/-β abundance or activity can restore oocyte quality in aged females. By identifying the molecular pathways that sustain oocyte developmental competence, these studies will advance our understanding of human development and drive improvements in reproductive health and outcomes for women and children.