Top3a Is Required For The Maintenance Of The Ovarian Follicular Reserve And Oocyte Quality
Purpose: Several lines of evidence from non-vertebrate organisms suggest TOP3A is critical for quality control in oocytes, with roles in the repair of meiotic DNA double strand breaks and DNA damage, and in the maintenance of mitochondrial DNA (mtDNA). Whilst compelling, the role of TOP3A in the gametes of mammalian species has never been established. Hence, this study aims to use novel mouse models to define the importance of TOP3A in the female gametes. Methods: Follicle Enumeration and in vitro fertilisation was conducted to determine the number and quality of TOP3A deficient oocytes. Microinjection of GFP-tagged TOP3A, in vitro oocyte maturation, and measurement of mtDNA copy number were performed to investigate the role of TOP3A in mitochondrial function. Results: Loss of Top3A leads to a dramatic loss of follicles in adult mice. Though the ovarian reserve is not compromised in young TOP3A oocyte-cKO mice, almost all the oocytes fail to be fertilized in vitro. Moreover, GFP-tagged TOP3A and mitochondria co-localized during the whole process of oocyte maturation, and mtDNA copy number in KO oocytes is significantly lower than that in WT oocytes. Conclusions: Top3A is required for healthy oocyte development and fertilization. Additionally, TOP3A is important for maintenance of mitochondrial function.