DPAGT1-Mediated Protein N-Glycosylation Is Indispensable for Oocyte and Follicle Development in Mice

Posttranslational modification of proteins by N-linked glycosylation is crucial for many life processes. However, the exact contribution of N-glycosylation to mammalian female reproduction remains largely undefined. Here, DPAGT1, the enzyme that catalyzes the first step of protein N-glycosyation, is identified to be indispensable for oocyte development in mice. A recessive missense mutation (c. 497A>G; p. Asp166Gly) of Dpagt1 causes female subfertility without grossly affecting other functions. Mutant females ovulate fewer eggs owing to defects of follicular development beyond the late secondary stage. Oocytes ovulated by mutants carry a thin and fragile zona pellucida, and display poor developmental competence after fertilization in vitro. Moreover, completion of the first meiosis is accelerated in mutant oocytes, which is coincident with the elevation of aneuploidy. Mechanistically, transcriptomic analysis reveals the downregulation of a number of transcripts essential for oocyte meiotic progression and preimplantation development (e.g., Pttgt1, Esco2, Orc6, and Npm2) in mutant oocytes, which could account for the defects observed. Furthermore, conditional knockout (CKO) of Dpagt1 in oocytes recapitulates the phenotypes observed in Dpagt1 mutant females, and causes complete infertility. Taken together, these data indicate that protein N-glycosylation in oocytes is essential for female fertility in mammals by specific control of oocyte development.