Collection of genomic DNA from adults in epidemiological studies by buccalcytobrush and mouthwash

Blood samples are an excellent source of large amounts of genomic DNA. Howe ver, alternative sources are often needed in epidemiological studies becaus e of difficulties in obtaining blood samples. This report evaluates the buc cal cytobrush and alcohol-containing mouthwash protocols for collecting DNA by mail. Several DNA extraction techniques are also evaluated. The study w as conducted in two phases. In phase 1, we compared cytobrush and mouthwash samples collected by mail in two different epidemiological studies: (a) cy tobrush samples (n = 120) from a United States case-control study of breast cancer; and (b) mouthwash samples (n = 40) from a prospective cohort of ma le United States farmers. Findings from phase 1 were confirmed in phase 2, where we randomized cytobrush (n = 28) and mouthwash (n = 25) samples among participants in the breast cancer study to directly compare both collectio n methods. The median human DNA yield determined by hybridization with a hu man DNA probe from phenol-chloroform extracts was 1.0 and 1.6 mug/2 brushes for phases 1 and 2, respectively, and 27.5 and 16.6 mug/mouthwash sample f or phases 1 and 2, respectively. Most (94-100%) mouthwash extracts containe d high molecular weight DNA (> 23 kb), in contrast to 55-61% of the brush e xtracts. PCR success rates for amplification of beta -globin gene fragments (268, 536, and 989 bp) were similar for cytobrush and mouthwash phenol-chl oroform extracts (range, 94.4-100%). Also, we obtained high success rates i n determining the number of CAG repeats in the androgen receptor gene, char acterizing tetranucleotide microsatellites in six gene loci, and screening for mutations in the BRCA1/2 genes in a subset of phenol-chloroform DNA ext racts. Relative to DNA extracted by phenol-chloroform from cytobrush sample s, DNA extracted by NaOH had lower molecular weight, decreased PCR success rates for most assays performed, and unreliably high spectrophotometer read ings for DNA yields. In conclusion, although DNA isolated from either mouth wash or cytobrush samples collected by mail from adults is adequate for a w ide range of PCR-based assays, a single mouthwash sample provides substanti ally larger amounts and higher molecular weight DNA than two cytobrush samp les.