Fig. 2: DNA damage checkpoints in oocytes.
From: Distinct characteristics of the DNA damage response in mammalian oocytes
a Lack of a robust G2/M DNA damage checkpoint. The canonical ATM-CHK1/2-CDC25 pathway is downregulated in fully grown oocytes and is partly influenced by WIP1 activity. Instead, oocytes use a noncanonical G2/M DNA damage checkpoint, which is associated with the regulation of APC/C-Cdh1 activity. DNA damage induces EMI1 degradation and MDC1 dissociation from APC/C-Cdh1, as well as CDC14B activation, which eventually leads to an increase in APC/C-Cdh1 activity. This, in turn, promotes cyclin B1 degradation, subsequently delaying GVBD. b DNA damage-induced SAC arrest. In general, the SAC is activated in the presence of unattached kinetochores, which leads to the inhibition of APC/C and subsequent anaphase onset. However, in oocytes with DNA damage, the SAC is activated independently of unattached kinetochores during meiosis I.
