In brief, a total of 50 oocytes with zona pellucida removed, and 50,000 GCs were lysed respectively in lysis buffer (10 mM Tris-HCl (pH7.4), 10 mM NaCl, 3mM MgCl2, 0.1%Igepal CA-630, 0.1%Tween-20, 0.01%Digitonin, 1% Cytochalasin B, 0.1%collagenase I) for 10 min on ice to generate the nuclei. Nuclei were then spun at 500g for 5 min immediately to remove the supernatant. Tn5 transposome and tagmentation procedures were subjected at 37°C for 30 min (Vazyme, TD501). DNA were purified using 2×AMPure beads (Beckman, A63881) and conducted to 16 cycles (for oocytes) or 14 cycles (for GCs) of library amplification using the following PCR conditions: 72°C for 3 min; 98°C for 30s; and thermocycling at 98 °C for 15s, 60°C for 30 s and 72°C for 3 min; following by 72°C 5 min.The amplified DNA was size-selected using AMPure beads for 200–500bp DNA fragments. All libraries were sequenced by the Novaseq 6000 platform to at least a depth of 4.0×107 reads accordingly.