Manjrekar Johannes
Maharaja Sayajirao University of Baroda, Vadodara 390 002, India.
J Genet. 2017 Jul;96(3):445-456. doi: 10.1007/s12041-017-0798-3.
The field of epigenetics has grown explosively in the past two decades or so. As currently defined, epigenetics deals with heritable, metastable and usually reversible changes that do not involve alterations in DNA sequence, but alter the way that information encoded inDNAis utilized.The bulk of current research in epigenetics concerns itself with mitotically inherited epigenetic processes underlying development or responses to environmental cues (as well as the role of mis-regulation or dys-regulation of such processes in disease and ageing), i.e., epigenetic changes occurring within individuals. However, a steadily growing body of evidence indicates that epigenetic changes may also sometimes be transmitted from parents to progeny, meiotically in sexually reproducing organisms or mitotically in asexually reproducing ones. Such transgenerational epigenetic inheritance (TEI) raises obvious questions about a possible evolutionary role for epigenetic 'Lamarckian' mechanisms in evolution, particularly when epigenetic modifications are induced by environmental cues. In this review I attempt a brief overview of the periodically reviewed and debated 'classical' TEI phenomena and their possible implications for evolution. The review then focusses on a less-discussed, unique kind of protein-only epigenetic inheritance mediated by prions. Much remains to be learnt about the mechanisms, persistence and effects of TEI. The jury is still out on their evolutionary significance and how these phenomena should be incorporated into evolutionary theory, but the growing weight of evidence indicates that likely evolutionary roles for these processes need to be seriously explored.
在过去二十年左右的时间里，表观遗传学领域呈爆发式增长。按照目前的定义，表观遗传学研究的是可遗传、亚稳定且通常可逆的变化，这些变化不涉及DNA序列的改变，但会改变DNA中编码信息的利用方式。目前表观遗传学的大部分研究关注的是发育或对环境线索的反应背后的有丝分裂遗传表观遗传过程（以及这些过程的失调或异常调节在疾病和衰老中的作用），即个体内部发生的表观遗传变化。然而，越来越多的证据表明，表观遗传变化有时也可能从亲代传递给子代，在有性生殖生物中通过减数分裂传递，在无性生殖生物中通过有丝分裂传递。这种跨代表观遗传遗传（TEI）引发了关于表观遗传“拉马克式”机制在进化中可能的进化作用的明显问题，特别是当表观遗传修饰由环境线索诱导时。在这篇综述中，我试图简要概述经过定期综述和辩论的“经典”TEI现象及其对进化的可能影响。然后，综述聚焦于一种较少讨论的、由朊病毒介导的独特的仅蛋白质表观遗传遗传。关于TEI的机制、持续性和影响，仍有许多有待了解的地方。关于它们的进化意义以及这些现象应如何纳入进化理论，尚无定论，但越来越多的证据表明，需要认真探索这些过程可能的进化作用。
