genomic DNA  from lip tissues of sample SF033
Total tissue genomic DNA was extracted using the QIA amp DNA Mini Kit (Qiagen, Germany) according to the manufacturers instructions. The DNA quality and concentration were evaluated based on the optical density 260/280 and 260/230 ratios using a Nano Drop ND-2000 spectrophotometer (Thermo Fisher Scientific, USA). DNA integrity was assessed by agarose gel electrophoresis. Then the genomic DNA was randomly sheared into 200-311 bp fragments for bisulfite treatment by an EZ DNA Methylation Gold Kit (Zymo Research, USA). Finally, the complete DNA library was constructed for sequencing (Precisiongenes Inc., China).