Saliva as a viable alternative source of human genomic DNA in genetic epidemiology

Saliva is a potentially useful but untapped source of genomic DNA for genetic epidemiological studies. However, current commercial methods are mainly concerned with DNA extraction and do not address important issues concerning saliva preservation and storage. As such, we evaluated how various saliva storage conditions affected DNA yield and quality obtained using a new commercially available method that proposes to integrate these aspects in a single kit.

The conditions involved the extraction of the DNA immediately after saliva collection (condition 1) or when stored at air-conditioned room temperature (20 degrees C) for 1 month (condition 2) and 6 months (condition 3) as well as at -80 degrees C for 6 months (condition 4). The effect of incorporating an additional incubation of saliva samples at 30 degrees C for 2 weeks was also examined.

Overall average DNA yield from 2 ml of saliva was 35.5 microg (8.5-85.2 microg). DNA yield was unaffected by incubation of saliva at 30 degrees C but DNA yield under condition 3 was significantly higher compared to conditions 1 and 2. OD260/280 values were acceptable and comparable across all conditions. Differences in storage conditions did not impact DNA quality in real time PCR experiments and genotyping fidelity remained undiminished.

Saliva is a viable alternative source of human genomic DNA for genetic epidemiological studies and that this new commercial method and possibly other related techniques can be effective means towards this end.