The mitochondrial deoxyguanosine kinase is required for female fertility in mice

Mitochondrial homeostasis plays a pivotal role in oocyte maturation and embryonic development. Deoxyguanosine kinase (DGUOK) is a nucleoside kinase that salvages purine nucleoside in the mitochondria and is critical for mitochondrial DNA replication and homeostasis in non-proliferating cells. Dguok loss-of-function mutations and deletions lead to hepatocerebral mitochondrial DNA deletion syndrome. However, its potential role in reproduction remains largely unknown. We found that Dguok knockout results in female infertility. Mechanistically, the deficiency of DGUOK hinders ovarian development and oocyte maturation. Moreover, Dguok deficiency in oocytes caused a significant reduction in mitochondrial DNA and abnormal mitochondrial dynamics, and impaired germinal vesicle breakdown. Only few DGUOK-deficient oocytes were able to extrude the first polar body during in vitro maturation, and these oocytes showed irregular chromosome arrangement and different spindle lengths. In addition, Dguok deficiency elevated reactive oxygen species and accelerated apoptosis in oocytes. Our findings reveal novel physiological roles for the mitochondrial nucleoside salvage pathway in oocyte maturation and implicate that DGUOK is a potential marker for the diagnosis of female infertility.