MUC1 Protects Preimplantation Embryos In Vitro via Clearance of ROS by Triggering Mitophagy

Embryos being treated using assisted reproductive technology (ART) are unavoidably exposed to physical stressors, thus producing reactive oxygen species (ROS) which trigger mitophagy to support embryonic development. However, the mechanisms underlying the regulation of mitophagy in early embryonic development remain largely unexplored. Here, we found that Mucin 1 (MUC1) exhibited a uniform distribution in both mouse and human oocytes, and its expression peaked at the blastocyst stage. Further analysis revealed that Muc1 knockout impairs blastocyst formation in vitro. Correspondingly, Muc1 knockout led to the accumulation of mitochondrial reactive oxygen species (mtROS) and a reduction in phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1)/Parkinson protein 2 (PARK2/Parkin)-dependent mitophagy. Stimulation of mitophagy via low-dose carbonyl cyanide 3-chlorophenylhydrazone (CCCP) treatment rescued the blastocyst formation defect in Muc1-null embryos. Vitamin C supplementation effectively scavenged mtROS and restored developmental competence. Together, our findings establish that MUC1 safeguards early embryonic development by promoting mitophagy to decrease mtROS levels in vitro. Moreover, vitamin C could compensate for Muc1 deficiency by eliminating mtROS. This study not only identified a new function of MUC1 in protecting early embryonic development in vitro, but also revealed a novel mechanism of mitophagy regulation in early embryos, which has potential applications for ART.