A novel system used by pre-implantation mammalian embryos to amplify environmentally-induced changes in sperm miRNA content after fertilization.

总结 跨代表观遗传包括将经验的影响传递给后代 通过生殖细胞中的表观遗传变化而在几代人之间传播。它在低等生物如C. elegans 越来越多的证据表明，包括人类在内的哺乳动物也存在类似的现象。多 啮齿类动物中这一过程的支持来自于对暴露于慢性心理应激的雄性小鼠的实验。 应激，其中特异性精子miRNAs水平的应激类型特异性变化涉及 将压力相关的特征代代相传。然而，精子中的miRNAs水平要低得多， 包括早期胚胎中的细胞。这一事实意味着一个系统必须存在于胚胎中， 在受精后扩大和延长精子含量的环境变化。实际上，自动放大 系统的存在，是必要的跨代表观遗传遗传在较低的有机体。但安 在哺乳动物中尚未报道类似的系统。这项资助是由我们最近发现的 似乎是精子miR-34/449家族的新扩增系统。这些mRNAs特别 在这种情况下，我们的兴趣，因为我们暗示他们在父亲的传播增强焦虑， 暴露于慢性社会不稳定的雄性小鼠的雌性后代特异性地表现出社交缺陷 (CSI)应力我们发现CSI应激不仅降低了男性精子中miR-34 B/c和miR-449 a/B的水平， 暴露于CSI应激的小鼠，但也在至少通过囊胚期从它们衍生的早期胚胎中 早期胚胎发育，即使这些miRNAs在精子中的水平比正常情况下低得多， 存在于植入前胚胎中。我们发现的扩增系统是基于我们的发现，即miR- 34 c在植入前小鼠中正常正调控其自身基因和miR-449的表达 胚胎，并且该系统似乎在来自CSI应激雄性的胚胎中受到抑制。令人惊讶的是，我们 在这些胚胎中未检测到miR-34 c的初级转录物或部分加工形式的变化， 这表明精子miR-34，可能还有miR-449，调节胚胎产生的这种成员的稳定性。 miRNA家族该系统与人类的潜在相关性得到了我们的发现的支持，即：a）miR-121和miR-122都是一种新的基因。 在经历过严重虐待和/或功能障碍的男性精子中， 年轻时的家庭生活;和B）类似的扩增系统似乎存在于人胚胎干细胞中。 该提案的目标是通过测量miR-34和miR-449的半衰期及其在细胞中的表达来验证这一假设。 它们的“拖尾”和“修剪”程度，这是降解过程的一部分。我们预计， 研究结果将证明更多的长期资助实验，揭示这些miRNAs如何控制自己的基因， 退化，因为这一过程可能是必要的特定形式的跨代表观遗传， 无论是老鼠还是男人。

Summary Transgenerational epigenetic inheritance involves transmission of the effects of experiences to offspring across generations via epigenetic changes in germ cells. It is well established in lower organisms like C. elegans and plants, and growing evidence implies a similar phenomenon occurs in mammals including humans. Much support for this process in rodents derives from experiments on male mice exposed to chronic psychological stress, where stress-type specific changes in the levels of specific sperm miRNAs have been implicated in transmitting stress-associated traits across generations. However, sperm contain much lower levels of miRNAs than those of most cells, including those in early embryos. This fact implies a system must exist in embryos to magnify and extend environmental changes in their sperm content after fertilization. In fact, an auto-amplification systems exists and is necessary for transgenerational epigenetic inheritance in lower organisms. However, an analogous system has not been reported in mammals. This grant is driven by our recent discovery of what appears to be a novel amplification system for the sperm miR-34/449 family. These mRNAs are of particular interest in this context because we implicated them in the paternal transmission of enhanced anxiety and defective sociability displayed specifically to female offspring of male mice exposed to Chronic Social Instability (CSI) stress. We found that CSI stress reduces levels of miR-34b/c and miR-449a/b not only in sperm of male mice exposed to CSI stress but also in early embryos derived from them through at least the blastocyst stage of early embryogenesis, even though the levels of these miRNAs in sperm are much lower than that normally present in preimplantation embryos. The amplification system we uncovered is based on our findings that miR- 34c normally positively regulates the expression of its own gene and that for miR-449 in preimplantation mouse embryos, and that this system appears to be suppressed in embryos from CSI stressed males. Surprisingly, we do not detect changes in the primary transcripts or partially processed forms of miR-34c in these embryos, suggesting sperm miR-34, and possibly miR-449, regulates the stability of embryo produced members of this miRNA family. The potential relevance of this system to humans is supported by our findings that; a) both miR- 34 and miR-449 levels are also reduced in sperm of men who experienced severe abusive and/or dysfunctional family life when young; and b) a similar amplification system appears to exist in human embryonic stem cells. The goal of this proposal is to test this hypothesis by measuring the half-lives of miR-34 and miR-449 and their extent of their “tailing” and “trimming”, which are part of the degradation process. We anticipate that these findings will justify more long-term funding for experiments that reveal the how these miRNAs control their own degradation, since this process may necessary for specific forms of transgenerational epigenetic inheritance in both mice and men.