Different haplotypes of the 4E3 region were generated by site-directed mutagenesis with the Quick change site-directed mutagenesis kit (Stratagene, La Jolla, CA). Primers were designed with the SNP at the center (Table 1b). The amplified products were digested with DpnI to remove the template plasmid, and then transformed into DH5α competent cells (Invitrogen). Transformants were sequenced to confirm the presence of the SNP at the desired site.
