Molecular Biology of the Oocyte

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Gonadogenesis: Female germ cells arrested at the prophase of the first meiotic division form follicles in which they are surrounded by somatic cells in the neonatal ovary. These follicles grow and asymmetrical cell division during meiosis ensures that ovulated eggs contain maternal factors necessary for successful development. Post-natal male germ cells maintain a spermatogonia stem cell niche within the testis from which cohorts are selected to undergo meiosis and are transmogrified into mature spermatozoa during spermiogenesis. Current studies investigate the roles of: 1) FIGLA, a germ cell specific transcription factor required for follicle formation in female mice; 2) SSNP1, a germ cell nuclear protein required for maintenance of spermatogonia stem cells; and 3) BTBD18, a nuclear protein that ensures pachytene piRNA expression necessary for spermiogenesis. Fertilization: The taxon-specificity of sperm-egg recognition in mammals that results in monospermic fertilization is mediated primarily by the zona pellucida, an extracellular matrix surrounding ovulated eggs. Although a simple structure of 3-4 glycoproteins, the molecular basis of this sperm binding to the zona pellucida has been controversial. Current studies investigate: 1) molecular requirements to support taxon-specific sperm-egg recognition on the surface of the zona pellucida; 2) mechanism that result in acrosome exocytosis necessary for gamete fusion; and 3) the processes by which post-fertilization polyspermy is prevented. Early Development: Transcription that terminates during meiotic maturation of mouse eggs resumes only after robust activation of the embryonic genome of the two-cell embryo. This interregnum between oocyte and embryonic gene transcription dictates a role for stored maternal factors. Using mouse transgenesis, the role of individual or complexes of maternal factors is studied in these processes. Current research investigates: 1) novel maternal effect genes that affect early mouse development; 2) the role of maternal organelles in the maternal to zygotic transition; and 3) the degradation of maternal components in activation of the embryonic genome.