CXXC1 and female infertility: In support of this hypothesis, oocyte-specific deletion of Cxxc1, which encodes a key factor of the SETD1 histone H3 methyltransferase complex, led to a wide spectrum of premature aging-related phenotypes, including 1) aneuploidy after meiotic division, anovulation, and, ultimately, female infertility;34–36 2) some cytoplasmic changes, including increases of ROS levels, aggregation of mitochondria, decreases of mitochondrial DNA copy numbers as well as mitochondrial membrane potential, were observed in both aged oocytes and Cxxc1-null oocytes (Fig. 5).