Epigenetic regulation involves changes in gene expression independent of DNA sequence variation that are inherited through cell division. In addition to a fundamental role in cell differentiation, some epigenetic changes can also be transmitted transgenerationally through meiosis. Epigenetic alterations (epimutations) could thus contribute to heritable variation within populations and be subject to evolutionary processes such as natural selection and drift. However, the rate at which epimutations arise and their typical persistence are unknown, making it difficult to evaluate their potential for evolutionary adaptation. Here, we perform a genome-wide study of epimutations in a metazoan organism. We use experimental evolution to characterize the rate, spectrum and stability of epimutations driven by small silencing RNAs in the model nematode Caenorhabditis elegans. We show that epimutations arise spontaneously at a rate approximately 25 times greater than DNA sequence changes and typically have short half-lives of two to three generations. Nevertheless, some epimutations last at least ten generations. Epimutations mediated by small RNAs may thus contribute to evolutionary processes over a short timescale but are unlikely to bring about long-term divergence in the absence of selection.

表观遗传调控涉及基因表达的变化，而该变化不依赖于通过细胞分裂遗传的DNA序列变异。除了在细胞分化中起基本作用外，一些表观遗传学改变也可以通过减数分裂跨代传播。因此，表观遗传改变（表位变异）可能会导致种群内部的遗传变异，并可能经历诸如自然选择和漂移之类的进化过程。但是，尚不清楚表位变异的发生率及其典型的持久性，因此很难评估其进化适应的潜力。在这里，我们对后生生物中的突变进行了全基因组研究。我们使用实验进化来表征模型线虫中小沉默RNA驱动的突变的速率，频谱和稳定性秀丽 隐杆线虫。我们显示表位变异自发地以大约25倍于DNA序列变化的速率出现，并且通常具有两到三代的短半衰期。然而，一些突变至少持续了十代。因此，由小RNA介导的表位变异可能会在短时间内促进进化过程，但在没有选择的情况下，不可能导致长期分歧。