Nsun2 is critical for mouse oocyte meiosis and early embryonic development

Biallelic variants in the NSUN2 gene cause a rare intellectual disability and female infertility in humans. However, the function and mechanism of NSUN2 during mouse oocyte meiotic maturation and early embryonic development are unknown. Here, we show that NSUN2 is important for mouse oocyte meiotic maturation and early embryonic development. Specifically, NSUN2 is required for ovarian development and oocyte meiosis, and deletion of Nsun2 reduces oocyte maturation and increases the rates of misaligned chromosomes and aberrant spindles. In addition, Nsun2 deficiency results in a low blastocyst rate and impaired blastocyst quality. Strikingly, loss of Nsun2 leads to approximately 35% of embryos being blocked at the 2-cell stage, and Nsun2 knockdown impairs zygotic genome activation at the 2-cell stage. Taken together, these findings suggest that NSUN2 plays a critical role in mouse oocyte meiotic maturation and early embryonic development, and provide key resources for elucidating female infertility with NSUN2 mutations.