Unraveling mitochondrial function in germ cell development through enforced mitophagy

/ABSTRACT Mitochondria are multifunctional organelles with an endosymbiotic origin over 1.5 billion years ago. Beyond their classical role in bioenergetics, mitochondria are key regulators of calcium signaling, apoptosis, and epigenetic programming. Importantly, they retain their own genome (mtDNA), which is essential for cellular fitness, germline development, and species continuity. In oocytes, mitochondrial abundance—quantified by mtDNA copy number—correlates strongly with fertility and developmental potential, highlighting mitochondria as critical determinants of reproductive health. Despite this importance, conventional genetic approaches such as mtDNA depletion or gene knockouts often fail to capture the dynamic, tissue-specific, and temporally regulated roles of mitochondria, particularly in vivo. To overcome these limitations, we have developed a novel enforced mitophagy platform that enables controlled modulation of mitochondrial abundance and quality in vivo, across specific tissues and developmental windows. This proposal applies this innovative system to address key gaps in our understanding of mitochondrial dynamics in reproductive biology and aging. We propose: 1) To investigate how mitochondrial abundance influences primordial germ cell (PGC) specification and contributes to the mtDNA genetic bottleneck. 2) To establish an in vivo mitochondrial depletion model targeting developing germ cells, including spermatocytes, spermatozoa, and oocytes, which will clarify longstanding questions and controversies regarding the functional necessity of mitochondria across stages of gametogenesis. 3) To develop a periodic mitochondrial clearance system to enhance mitochondrial quality control in reproductive tissues. As a proof-of- concept, we will evaluate the system in ovarian stromal cells—an aging-sensitive population—with the goal of improving mitochondrial surveillance and extending reproductive lifespan. By establishing a tractable in vivo framework for manipulating mitochondrial abundance, this work will uncover foundational mechanisms underlying germ cell development, mtDNA inheritance, and age-related decline in reproductive function. The outcomes will have broad implications for reproductive biology, regenerative medicine, and the treatment of infertility and mitochondrial diseases. Project Number: 1R01HD121186-01 | Fiscal Year: 2026 | NIH Institute/Center: Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) | Principal Investigator: Jun Wu | Institution: UT SOUTHWESTERN MEDICAL CENTER, DALLAS, TX | Award Amount: $682,848 | Activity Code: R01 | Study Section: Special Emphasis Panel[ZRG1 EMS-C (02)] View on NIH RePORTER: https://reporter.nih.gov/project-details/11318869