Department of Archaeogenetics, Max Planck Institute for the Science of Human History, Jena, Germany.
Institute for Archaeological Sciences, Archaeo- and Palaeogenetics, University of Tübingen, Tübingen, Germany.
Sci Rep. 2016 Sep 12;6:32969. doi: 10.1038/srep32969.
Sub-fossilised remains may still contain highly degraded ancient DNA (aDNA) useful for palaeogenetic investigations. Whether X-ray computed [micro-] tomography ([μ]CT) imaging of these fossils may further damage aDNA remains debated. Although the effect of X-ray on DNA in living organisms is well documented, its impact on aDNA molecules is unexplored. Here we investigate the effects of synchrotron X-ray irradiation on aDNA from Pleistocene bones. A clear correlation appears between decreasing aDNA quantities and accumulating X-ray dose-levels above 2000 Gray (Gy). We further find that strong X-ray irradiation reduces the amount of nucleotide misincorporations at the aDNA molecule ends. No representative effect can be detected for doses below 200 Gy. Dosimetry shows that conventional μCT usually does not reach the risky dose level, while classical synchrotron imaging can degrade aDNA significantly. Optimised synchrotron protocols and simple rules introduced here are sufficient to ensure that fossils can be scanned without impairing future aDNA studies.
古生物遗骸中可能仍然含有高度降解的古代 DNA（aDNA），可用于古遗传学研究。X 射线计算机断层扫描（[μ]CT）是否会进一步破坏这些化石中的 aDNA 仍然存在争议。虽然 X 射线对活生物体中 DNA 的影响已有充分记录，但对 aDNA 分子的影响仍未得到探索。在这里，我们研究了同步加速器 X 射线辐照对来自更新世骨骼的 aDNA 的影响。在 2000 戈瑞（Gy）以上的累积 X 射线剂量水平下，aDNA 数量的减少与积累之间存在明显的相关性。我们进一步发现，强烈的 X 射线辐照会减少 aDNA 分子末端核苷酸错配的数量。在 200Gy 以下的剂量下，没有检测到代表性的影响。剂量测定表明，常规 μCT 通常不会达到危险剂量水平，而传统的同步加速器成像会显著降低 aDNA 的含量。这里介绍的优化的同步加速器方案和简单规则足以确保在不损害未来 aDNA 研究的情况下对化石进行扫描。
