As described in our previous study (14 (link)), total RNA was extracted from single oocytes using the SMARTer Ultra Low RNA kit for Illumina sequencing. Synthetic cDNA was used for quantitative real-time PCR (qPCR) with an ABI 7500 PCR machine. Gene expression was normalized to the expression of the housekeeping gene GAPDH. Primers were synthesized by Sangon Biotech (Shanghai) Co., Ltd. For mRNA expression identification, 16 IVM and 16 IVO human oocytes were used to extract RNA from each oocyte, respectively.