1. Nucleus extraction: Cell samples refer to ATAC-seq: A Method for Assaying Chromatin Accessibility Genome-Wide to lyse cells and obtain nuclei; Frozen tissue samples refer to An improved ATAC-seq protocol reduces background and enables interrogation of frozen tissues The method in extracts nuclei. 2. Transposition reaction: 40,000 nuclei were taken into Tn5 enzyme (Illumina) for transposition reaction, and the DNA fragments after transposition were recovered with MinElute PCR Purification Kit (Qiagen). 3. Library construction: PCR amplification was performed with 1X NEBNext High-Fidelity PCR Master Mix (New England Biolabs, MA). The amplified products were recovered with MinElute PCR Purification Kit (Qiagen).