For ATAC-seq with paternal pronuclei (PPN), 1-cell embryos (12 hpf) were cultured in M2 medium containing 10 mg/ml cytochalasin B (Calbiochem) for 15 min. PPN were collected with minimal cytoplasm carryover using a Piezo-driven micromanipulator (Eppendorf). After washing with 1% BSA/PBS, 75-100 PPN were collected for ATAC-seq following the same protocol as previously described in Zhang et al., Genes & development, 2020.