Oocyte-specific deletion of Eif5 causes apoptosis of mouse oocytes within the early growing follicles by mitochondrial fission defect and DNA damage

Mutations in several translation initiation factors are closely associated with premature ovarian insufficiency (POI). Here, we demonstrate that the conditional knockout of eukaryotic translation initiation factor 5 (Eif5) in both mouse primordial and growing oocytes resulted in the apoptosis of oocytes within the early growing follicles. The further studies revealed that Eif5 deletion in oocytes downregulated the levels of mitochondrial fission-related proteins (FIS1, MFF, MTFR2 and p-DRP1) and upregulated the levels of the integrated stress response (ISR)-related proteins (SLC7A1, SHMT2 and AARS1) and genes (Atf4, Ddit3 and Fgf21). Consistent with this, Eif5 deletion in oocytes resulted in mitochondrial dysfunction characterized by elongated form, aggregated distribution beneath the oocyte membrane, decreased ATP content and mtDNA copy number, and excessive accumulation of reactive oxygen species (ROS) and mitochondrial superoxide. Meanwhile, Eif5 deletion in oocytes led to a significant increase in the levels of DNAdamageresponse proteins (γH2AX, p-CHK2, and p53) and proapoptotic proteins (PUMA and BAX), as well as a significant decrease in the levels of anti-apoptotic protein BCL-xL. Collectively, these findings indicate that Eif5 deletion in mouse oocytes results in the apoptosis of oocytes within the early growing follicles via mitochondrial fission defect and excessive ROS-induced DNA damage. This study provides new insights into pathogenesis and genetic diagnosis for POI.