• Ancient mitochondrial DNA from hair

      Gilbert, M.T.P.; Wilson, Andrew S.; Bunce, M.; Hansen, A.J.; Janaway, Robert C.; Willerslev, E.; Shapiro, B.; Higham, T.F.G.; Richards, Michael P.; O'Connell, T.C.; et al. (2004)
      The DNA content of hair [1.] and [2.] is typically low compared to other tissues, as hair cells undergo dehydration and catabolic breakdown of nucleic acids and organelles during keratinisation [3]. As a consequence, ancient hair specimens have not been widely used as a source of ancient DNA. However, mitochondrial DNA (mtDNA) has been extracted from degraded and old hair samples, including burnt specimens [4], 100-year-old Native American samples [5], and wool from a 9,400 year old Bighorn sheep [6]. We have investigated the potential of hair as an aDNA source by analyzing DNA survival in 12 samples which range from 60 to >64,800 years of age and their susceptibility to contamination with modern DNA. mtDNA was successfully amplified, cloned, and sequenced from 10 of the 12 hair samples following decontamination procedures (Table 1). DNA was quantified using Quantitative Real-Time PCR in a subset of the samples (Table 1). The survival of high copy numbers of 16S DNA from the 3,000 year-old Pazyryk horse hairs is consistent with the observation that DNA survives longer at sub-zero temperatures [7]. Of greater surprise was the persistence of high numbers of 16S and Control Region DNA molecules in hairs sampled from a bison mummy 14C dated to >64,800 years. This result was independently replicated and extends the time frame from which authentic DNA has been retrieved from hair by at least seven-fold, placing it on a par with the oldest authentic DNA retrieved from bones and teeth [8]. No nuclear DNA could be amplified from the bison hair, consistent with observations of modern hair samples [1.] and 9. M.R. Wilson, D. Polanskey, J. Butler, J.A. DiZinno, J. Replogle and B. Budowle, Extraction, PCR amplification and sequencing of mitochondrial DNA from human hair shafts, Biotechniques 18 (1995), pp. 662¿669.[9.]. It is probably significant that the bison hairs are exceedingly well preserved ¿ the atomic carbon to nitrogen ratio (3.47) is similar to modern mammal hair [10.] and [11.] and histological analysis of the specimen demonstrates the only structural modifications to be slight cuticular loss and adherent deposits (Supplemental data).