A SIMPLE MOUTHWASH METHOD FOR OBTAINING GENOMIC DNA IN MOLECULAR EPIDEMIOLOGIC STUDIES

Genomic DNA for genetic analyses has traditionally been derived from b lood samples, With the availability of PCR techniques requiring only m inute amounts of DNA and the current demand for high-volume testing, a less invasive, simpler to perform, and cheaper method to obtain DNA i s desirable. We developed a method to obtain high-quality genomic DNA from buccal cells that has high acceptability and allows for a large n umber of PCR assays from a single sample. Sixty subjects vigorously sw ished 10 ml of undiluted commercial mouthwash in the mouth for 60 s an d expelled the liquid into a collection container. DNA was isolated fr om the buccal cells with a rapid method using proteinase K digestion, phenol-chloroform extraction, and ethanol precipitation. Electrophoret ic analysis of the extracted DNA showed detectable levels of high mole cular weight genomic DNA in all samples, The DNA yields ranged from 0. 2 to 134.0 mu g, for an average of 49.7 mu g. Using these samples, all 60 subjects were successfully genotyped by PCR-based assays for polym orphisms in the CYP1A1 (MspI and exon 7), CYP2E1 (RsaI), GSTM1, GSTT1, and NQO1 genes, confirming that the quality of DNA isolated from mout hwash samples was sufficient to reliably support PCR amplification. St orage of the (unprocessed) specimens at room temperature or at 37 degr ees C for 1 week (temperature conditions that may be encountered when mailing samples) or at -20 degrees C for at least 6 months did not aff ect the DNA yield or ability to PCR amplify the samples. The results s uggest that this mouthwash procedure may be suitable for large communi ty-based studies of genetic susceptibility to disease in which samples can be collected by the participants themselves, mailed back to the s tudy center, and stored for months prior to DNA analysis.