The buccal epithelial cell samples were collected using standard cytology brushes (Fisher Scientific, Fair Lawn, New Jersey). DNA was isolated from the brushes as reported previously.49 All individuals provided informed consent for participation in this study. Sixteen unlinked microsatellite markers and 33 SNPs were genotyped separately for the VAND and VAANX to assess the potential population stratification, and no evidence of stratification was found.48,49
