The Mammalian Oocyte: A Central Hub for Cellular Reprogramming and Stemness.

Abstract

The mammalian oocyte is pivotal in reproductive biology, acting as a central hub for cellular reprogramming and stemness. It uniquely contributes half of the zygotic nuclear genome and the entirety of the mitochondrial genome, ensuring individual development and health. Oocyte-mediated reprogramming, exemplified by nuclear transfer, resets somatic cell identity to achieve pluripotency and has transformative potential in regenerative medicine. This process is critical for understanding cellular differentiation, improving assisted reproductive technologies, and advancing cloning and stem cell research. During fertilization, the maternal-zygotic transition shifts developmental control from maternal factors to zygotic genome activation, establishing totipotency. Oocytes also harbor reprogramming factors that guide nuclear remodeling, epigenetic modifications, and metabolic reprogramming, enabling early embryogenesis. Structures like mitochondria, lipid droplets, and cytoplasmic lattices contribute to energy production, molecular regulation, and cellular organization. Recent insights into oocyte components, such as ooplasmic nanovesicles and endolysosomal vesicular assemblies (ELVAS), highlight their roles in maintaining cellular homeostasis, protein synthesis, and reprogramming efficiency. By unraveling the reprogramming mechanisms inherent in oocytes, we advance our understanding of cloning, cell differentiation, and stem cell therapy, highlighting their valuable significance in developmental biology and regenerative medicine.