The collection of samples that will yield large amounts of good quality DNA can be difficult if blood samples are not used. Blood sampling is not always practical, requires skill and should be done...
As the genotyping of single nucleotide polymorphisms (SNPs) becomes more
automated and less costly, the limiting factor for genome-wide genetic
analysis is becoming the limited amount of DNA that can be collected from
study subjects. A renewable source of genomic DNA is desirable. The traditional
method of transforming lymphoblastic cell lines is usually too expensive
for population studies with large sample sizes. A less expensive alternative
is whole genome amplification (WGA), which allows in vitro production
of numerous copies of the entire genome.
Large population-based studies, involving hundreds to thousands of subjects,
are frequently used to investigate the genetic determinants of complex
diseases. Saliva is a convenient source of genomic DNA because it can
be collected in a painless and non-invasive manner. For logistic reasons,
samples often need to be stored prior to the extraction of DNA. Common
storage methods, such as refrigeration and freezing, can add significant
costs and inconvenience to a genetic study. In addition, these methods
may be of limited effectiveness. For example, Ng et al. (2004) observed
as much as a 30% decrease in PCR product yield from saliva samples that
had been stored at -70°C for 1 month.
The number of studies collecting genomic DNA from a large number of individuals
is increasing rapidly. Non-invasive methods and techniques that permit
selfcollection are preferred because they increase compliance rates and
reduce costs. For this reason, many large-scale studies now use buccal
cells from saliva as the source of DNA. The two most common methods are
scraping the inside of the cheek with a brush and swishing the mouth with
a mouthwash. Oragene is a DNA self-collection kit that is non-invasive
and intuitive to use. The donor rinses his or her mouth with water to
clear food particles and then spits 2 mL of saliva into the Oragene vial.
Once the vial is closed, DNA is released and stabilized at room temperature.
Single-nucleotide polymorphisms (SNPs) are highly abundant, and are estimated
to occur at 1 out of every 1,000 bases in the human genome (ref. 1). In
addition to diagnostic applications, SNPs are useful as markers in population
genetics and evolutionary studies (ref. 2). The TaqMan 5’ nuclease assay
is a widely-used SNP genotyping technology from Applied Biosystems. The
purpose of this study was to evaluate the compatibility of Oragene DNA
Self-Collection Kits with TaqMan SNP Genotyping Assays.
Blood leukocytes are the traditional source of DNA for molecular testing,
but collection is invasive and specimens require infectious precautions.
Buccal swabs are a less-invasive method of collecting DNA for sequencing
applications such as HLA typing and prelingual deafness screening (ref.
1, 2) but they tend to have an appreciable failure rate (ref. 3). Oragene
is a non-invasive DNA self-collection kit from saliva that provides significantly
higher DNA yields than buccal swabs (ref. 4). The purpose of this study
was to investigate the suitability of DNA from Oragene for DNA sequencing.