Genotyping methods and quality control have been previously described in detail (13). Briefly, saliva was collected in Oragene vials (DNA Genotek Inc., Ontario Canada). DNA was extracted using the Agencourt DNAdvance extraction kit (Beckman Coulter Inc., Danvers, MA) then quantified using gel electrophoresis and Quantity One software (Bio-Rad, Hercules, CA) or NanoDrop2000 (Thermo Fisher Scientific Inc., Waltham, MA). The DNA was normalized to10 ng/µl and a total amount of 15 ng or 20 ng of dried down DNA per reaction was used for Taqman and Sequenom reactions, respectively. Sequenom reactions were performed using iPlex reagents on the MassARRAY system (Sequenom Inc., San Diego, CA). Additional reactions were performed on the Taqman ViiA7 Real-Time PCR system using Taqman SNP Genotyping Assays as well as Taqman Genotyping Master Mix or Taqman GTXpress Master Mix (Life Technologies Inc., Carlsbad, CA).
