Genetic investigations of athletes- the choice of sample tissue
Brearley, MB & Zhou, S 2001, 'Genetic investigations of athletes- the choice of sample tissue', paper presented to Exercise, muscle and metabolism, an official satellite of the International Congress of Physiological Sciences, Deakin University, Melbourne, Vic.
A host of athletic phenotypes demonstrate evidence of genetic influence, including endurance, strength and motor control characteristics. The challenge facing exercise and sport scientists is to locate the molecular sites exerting the observed influence, thereby, relating genotype to phenotype. Molecular investigations of athletes require consideration for choice of the biological tissue for genotyping. The most suitable tissue would permit collection in the field given limited access to athletes in controlled laboratory conditions. While skeletal muscle is the sample tissue of choice for DNA extraction and blood has been extensively utilised, the invasive nature of sample collection and subsequent narrow window for transportation and storage renders these tissues undesirable for collection in the field.
Hair is an alternative tissue that permits non-invasive sample acquisition and flexible storage conditions, while negating the need for skilled collection techniques. Importantly, hairs allow for field-based collection. Recent research demonstrated routine hair sample collection from cyclists immediately prior to and following competition (Brearley et al., 2001). This research showed that hairs can be successfully reserved in 70% (v/v) ethanol for at least ?months. Various storage mediums were evaluated for an effect on the quantity of extracted DNA. Freshly plucked hairs demonstrated greater DNA yields than hairs stored for three months in ambient conditions and hairs stored in ethanol for three or twelve months. However, the differences in DNA yield were not limiting for subsequent DNA methodologies.
The use of hair samples for genotyping has previously been validated through comparison to DNA markers derived from muscle and blood specimens (Rousselet and Mangin, 1998). Rapid technical progress in the field of molecular biology over the past decades has provided procedures for utilising small quantities of hair derived DNA for analysis. Polymerase Chain Reaction (PCR) technology allows in-vitro amplification of desired genetic sequences to sufficient quantity for genotyping. However, PCR inhibition may occur while utilising genomic DNA derived from hair samples. Melanin, a protein contained with the hard keratin of the hair shaft has previously been shown to inhibit reverse transcription PCR (Giambernardi et al., 1998). The addition of Bovine Serum Albumin (BSA) (20ng) to reaction mixtures demonstrates relief of PCR inhibition. Thus, BSA is a useful addition to PCR reaction mixtures containing DNA derived from hairs. Other methods that also provide relief of the inhibition include diluting template DNA, severing the hair shaft prior to digestion and limiting lyse time.
Research conducted in our laboratory has analysed mitochondrial DNA derived from hundreds of human hairs. Throughout such analysis, data has been acquired to improve the use of hairs in genetic investigations. This research has demonstrated the use of hairs as a superior biological tissue to skeletal muscle and blood with respect to sample acquisition, handling and transportation. Genetic investigations of athletes may benefit from utilising hairs as a non-invasive source of DNA. (should we say "for certain genes"? Do you think hair can be used for any genetic analysis?)