CK_liver1
All the experiments were conducted using procedures as previously reported [44, 45]. Briefly, about 3 g genomic DNA of liver samples were isolated by phenol/chloroform extraction. The concentration and integrity of pooled DNA were detected by NanoPhotometer spectrophotometer (IMPLEN, CA, USA) and Agarose Gel Electrophoresis, respectively. The adapters were then added to the pooled genomic DNA (100-300bp), and followed by bisulfite conversion using Methylation-Gold kit (ZYMO, CA, USA). The unmethylated cytosine (C) is converted to uracil during sodium bisulfite treatment [46]. Finally, the converted DNA fragments were PCR amplified (QIAGEN, MD, USA), and sequenced on an Illumina HiSeqTM 2500 platform (Gene Denovo Biotechnology Co., Guangzhou, China).