Whole blood genome extraction kit

We utilized a commercial whole blood genome extraction kit to extract DNA from peripheral blood leukocytes according to the manufacturer’s instructions (Tiangen Biotech, China). We used SNPscan™ typing assays to detect polymorphisms of the MALAT1 gene. The probes for the identification of primer sequences were 5′-TGCATTTACTTGCCAACAGAACAGAAAG-3′ and 5′-TGCATTTACTTGCCAACAGAACAGAGAA-3′. The universal primer was 5′-ACCTGAAGTCAAGACAACTGCATTC-3′.

Venous blood samples were collected in EDTA-containing tubes from all participants following a 12-h fast. Genomic DNA was purified from the samples using a whole blood genome extraction kit (Tiangen Biotech, Beijing, China) and cryopreserved at −20 °C until use. Tag single nucleotide polymorphisms (SNPs of MAOA were derived from a Chinese Han population in the Haplotype Map database (National Center for Biotechnology Information). SNPs rs6323 and rs1137070 were genotyped with the SNaPshot SNP assay using the primers listed in Table 1. Data were analyzed using GeneMapper 4.1 (Applied Biosystems, Foster City, CA, USA). For quality control, 5% of randomly selected samples were genotyped a second time by different researchers, yielding 100% reproducibility.

Blood samples were collected into ethylene diamine tetraacetic acid tubes during the physicians’ physical examination. Genomic DNA (gDNA) was extracted using the Whole Blood Genome Extraction kit (Tiangen Biotech, Beijing, China) before cryopreservation at −20 °C until further use. The T102C and -1438G/A polymorphisms were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). gDNA (100 ng) was used in each reaction mixture, with the final volume of each reaction mixture totaling 20 μL. gDNA was then amplified using the PCR instrument (MyCycler, Bio-Rad, Hercules, CA, USA). Ten μL of PCR product was then used in each enzyme-digested mixture, with the final volume of each enzyme-digested mixture totaling 30 μL. The fragments were resolved with electrophoresis on 2% agarose gels and visualized with UV light. The primers used and genotype information for T102C and -1438G/A are listed in Table 1 and Table 2.