The importance of genetic variation to the etiology of neuropsychiatric disorders is well established and is currently being examined for diagnosis and treatment. The most popular method of obtaining material for genotype analysis, high-yielding DNA extraction from blood, has several limitations, including invasiveness, need for skilled individuals to collect material, and requirement for cold storage. Saliva sampling is non-invasive and trained personnel are less necessary, but it still requires a relatively high level of subject compliance. Buccal mucosa cells sampling is almost completely non-invasive, reducing compliance issues significantly. Samples collected have been shown to produce usable DNA after shipment through conventional mail. However, the DNA produced by rapid elution of these swabs in chaotropic buffers is of limited quality and low purity.
Our aim was to develop a rapid, economical, high-yielding and environmentally-safe method for extraction of high quality genomic DNA, which can be used to determine clinically important genotypes from trace quantity samples.
We developed a method of extracting high-quality genomic DNA from buccal swab, which we termed the `Rapid Method for Swab' (RMS). We compared RMS with two established procedures, specifically the original Rapid Method (RM) [Lahiri et al. J Biochem Biophys Methods. 25, 193-205 (1992)] and the commercially available BuccalAmp (Epicentre Biotechnologies, Madison, WI) method. We assessed the generated genomic DNAs by their i) quality, ii) quantity, iii) restriction enzyme digestibility and v) PCR-based genotyping in addition to time, cost and environmental impact of the procedures.
DNA generated by RMS was of higher purity than that by BuccalAmp. RMS is non-enzymatic and does not use strong chaotropic salts or extreme pH. We also demonstrated the suitability of RMS-DNA for LA/LG genotyping as generated by PCR using 7-deaza dGTP.
The RMS procedure is novel, efficient, safe, and high-yielding, and produces DNA of high quality from a single human buccal swab. RMS is a non-invasive technique and particularly suitable for children and older subjects and in field collection settings.