CK_liver1
About 30-50 mg frozen liver tissues (n = 3/group) were cut into aliquots with a sterile scalpel, stored in 2 mL EP tubes and then ground for 5 min at 35 Hz using a lapping machine (Scietz-48, Ning Bo, China). The powder together with resuspension were incubated on ice for 10 min. Subsequently, about 1 mL filtrate was obtained using pipette and centrifuged at 1000 rpm for 5 min at 4 C. Finally, cells were lysed using cold lysis buffer (10 mM Tris-Cl, pH 7.4, 10 mM NaCl, 3 mM MgCl2 and 0.1% IGEPAL CA-630). Immediately after lysis, nuclei were spun at 5000 rpm for 10 min under 4 C. Nuclei suspensions were incubated in a transposase reaction mix (25 L 2x TD buffer, 2.5 L transposase (Illumina) and 22.5 L of nuclease free water). The DNA sequence with open chromatin was fragmented by transposase. Simultaneously, adapter sequences were added to the ends of the DNA fragments. The transposition reaction was incubated at 37 C for 30 min and followed by transposition immediately. The products were purified using a QIAGEN minielute kit, and amplified as described previously [43]. Final DNA libraries were validated and sequenced paired-end at 150-nt per sequence read, using an Illumina HiSeqTM 4000 platform (Gene Denovo Biotechnology Co., Guangzhou, China).