For RNA-seq analysis, four independent collections of ten 2-cell embryos were placed in 1 uL of PBS in a 1.5 ml tube and frozen at -80°C until library preparation. For ATAC-seq analysis, two independent collections of 100 late 2-cell embryos/group were performed. Zona pellucidae were removed using acid Tyrode's solution followed by mechanical removal of polar bodies by pipetting embryos up and down in Ca2+/Mg2+-free CZB. Embryos were placed in a 1.5-ml tube containing 4 ul of ice-cold 1x lysis buffer (10mM Tris-HCl, pH 7.4; 3 mM MgCl2, 0.1% IGEPAL CA630 for 15 min, followed by addition of 6 uL of 2x Tris-DMF-tagmentation buffer (20 mM Tris-HCl, pH 8.0; 10 mM MgCl2; 20% dimethylformamide). Transposase reaction was started by the addition of 2 uL of Nextera Tn5 transposase (Illumina) and incubation at 37C for 30 min. To stop the reaction, 0.5 μL of 10% SDS was added. DNA was then purified using the Qiagen MinElute PCR purification Kit, and eluted in 22 uL of elution buffer. mRNA libraries were constructed using the SMART-Seq® v4 Ultra® Low Input RNA Kit (TaKaRa) following the manufacturer's instructions. For ATAC-seq libraries, samples were amplified by 15 cycles of PCR using Phusion High-Fidelity PCR Master Mix with HF Buffer and Nextera universal primer and bar code primers. To deplete mitochondrial fragments from the ATAC-seq libraries, we used the CRISPR/Cas9-assisted removal of mitochondrial DNA (CARM) procedure from (Wu et al., Nature 534, 652-657, 2016).