Genotyping
DNA was extracted from 1–2 ml peripheral whole blood using a blood DNA extraction kit (Tiangen, China) according to the manufacturer’s directions. Gene polymorphism typing was performed using a SNaPshot Multiplex Kit (Thermo Fisher Scientific, Applied Biosystems, Foster City, CA ) according to the manufacturer’s directions.
All the primers were designed using Primer Premier 6.0 (PREMIER Biosoft, San Francisco, CA, USA) and synthesized by BGI Tech Solutions (Beijing Liuhe, China). Primer sequences are listed in Table 1.