O-GlcNAc transferase orchestrates oocyte maturation by modulating the activity of mitochondrial respiratory chain complex I.

Abnormalities in oocyte meiosis are a major cause of female infertility. O-GlcNAc transferase (OGT)-mediated O-GlcNAcylation is a post-translational modification of proteins involved in various biological processes. However, its specific function during oocyte maturation remains unclear. In this study, we demonstrate that conditional knockout of Ogt in developing mouse oocytes using Gdf9-Cre results in complete female infertility accompanied by impaired oocyte maturation and defective follicle development. Despite the absence of discernible differences in spindle morphology and chromosome alignment, OGT deficiency compromised kinetochore-microtubule attachments. Consequently, the spindle assembly checkpoint was activated, leading to meiotic arrest. Multi-omics analysis revealed that Ogt knockout not only disrupted biological processes associated with oocyte meiosis but also impaired the function of mitochondrial respiratory chain complex I. Further validation showed that Ogt knockout disrupts NADH-to-NAD+ conversion, thereby confirming that Ogt knockout impaired the function of mitochondrial respiratory chain complex I. Mechanistically, co-immunoprecipitation followed by mass spectrometry analysis identified an interaction between OGT and the mitochondrial complex I subunit NDUFA8. Ogt knockout reduced the protein level of NDUFA8, potentially contributing to the dysfunction of mitochondrial respiratory chain complex I. Consequently, depletion of OGT led to mitochondrial dysfunction, characterized by abnormal distribution, diminished membrane potential, and elevated oxidative stress, ultimately resulting in reduced ATP production. Taken together, our data confirm that OGT plays a crucial role in oocytes maturation and female reproduction by regulating the function of mitochondrial respiratory chain complex I.