Investigating the multigenerational link between sperm RNA content and birth defects caused by abnormal folate metabolism

几种疾病(如心血管疾病、糖尿病)和疾病(如自闭症、出生缺陷)在英国流行，但没有已知的遗传原因。越来越明显的是，我们生活的环境影响着我们患这些疾病的风险。例如，高糖/脂肪饮食会增加患糖尿病的风险，或者吸烟会增加患癌症的风险。值得注意的是，科学家们开始揭开证据，证明祖父母的“罪过”会影响他们子孙的健康。即使在环境侮辱不再存在的情况下，这种情况也会发生。我们和其他研究人员目前正在研究在没有基因突变的情况下，疾病是如何在多代人中遗传的。这种现象被称为跨代表观遗传(TEI)。表观遗传学是告诉细胞如何控制基因表达的指令层。它涉及一些化学物质，如甲基，这些化学物质与DNA结合，起到开/关开关的作用，或者说，小RNA也以一种未知的方式调节基因的表达。有可能这些表观遗传信息中的一些是遗传的，当它异常时，后代的疾病风险就会增加。我们对TEI的大部分了解来自植物、果蝇和蠕虫。我们最近创造了一个TEI的小鼠模型，将更好地研究TEI在人类中是如何发生的。老鼠和人类在DNA序列和起作用的表观遗传因素上有许多相似之处。此外，老鼠的世代时间很短，使得多世代研究更有效率。关于TEI如何发挥作用的流行假说是，环境应激源(例如，维生素缺乏、毒物暴露)扰乱了精子或卵细胞中形成新胚胎的表观遗传信息。反过来，这可能会影响婴儿发育过程中哪些基因的开启/关闭，甚至是个体一生中的开启/关闭。例如，如果后代中的某些基因受到影响，可能会导致出生缺陷(例如神经管缺陷[NTDS])或代谢性疾病(例如糖尿病)。代谢性疾病可能是在新精子或卵子中重建异常表观遗传信息的重要因素，从而产生TEI循环。这些关于TEI的复杂问题将在我们拟议的研究中进行探索。我们将研究一种不能正常代谢叶酸的小鼠模型，其结果是，出生缺陷会发生多代遗传。叶酸(也称为叶酸)是一种维生素，对产生表观遗传控制基因表达所需的甲基很重要。叶酸代谢在TEI中的作用尚不清楚，将在本研究中进行探讨。除了叶酸代谢异常外，我们的小鼠在祖父的精子中表现出非典型的表观遗传学特征，包括DNA甲基化和小RNA含量的变化。我们将确定精子中的小RNA含量是否是我们模型中观察到的出生缺陷的具体原因。为此，我们将向1-细胞小鼠胚胎注入特定的小RNA，并与我们的叶酸模型直接比较，评估出生缺陷的频率以及表观基因组和基因表达在多代中的变化。此外，我们将评估我们的模型中是否存在叶酸代谢以外的代谢变化，这些变化可能有助于在精子中重建异常的表观遗传学特征，以帮助维持TEI。总体而言，我们的研究旨在进一步了解TEI是如何在哺乳动物中发生的。在英国，有人建议孕妇服用叶酸来降低婴儿患NTDS的风险，尽管摄入量很低。我们的工作表明，男性在怀孕时也应该考虑叶酸的补充。此外，没有明显原因的人类出生缺陷可能归因于叶酸缺乏的祖父母。这项研究表明，叶酸强化计划在预防出生缺陷方面的重要性，但其全部影响可能需要几代人的时间才能解决。

Several diseases (e.g. cardiovascular disease, diabetes) and disorders (e.g. autism, birth defects) are prevalent in the UK without a known genetic cause. It is becoming clear that the environment in which we live affects our risk for these diseases. For example, a high sugar/fat diet increases your risk for diabetes, or smoking can increase your risk of cancer. Remarkably, scientists are beginning to unravel evidence that suggests that the 'sins' of grandparents affect the health of their children and grandchildren. This occurs even when the environmental insult is no longer present. We and other researchers are currently addressing how diseases are inherited over multiple generations when there are no genetic mutations. This phenomenon is called transgenerational epigenetic inheritance (TEI). Epigenetics is layer of instructions that tells a cell how to control gene expression. It involves chemicals, such as methyl groups, that bind to DNA and act as 'on/off' switches, or small RNA that also regulate gene expression in an unknown manner. It is possible that some of this epigenetic information is inherited, and when it is abnormal, there is increased disease risk in the offspring. Much of our understanding of TEI comes from plants, fruit flies, and worms. We recently generated a mouse model of TEI that will better address how TEI occurs in humans. Mice and humans share many similarities in their DNA sequences and the epigenetic factors at work. Furthermore, the generation time in mice is short making multigenerational research more efficient. The prevailing hypothesis for how TEI works is that an environmental stressor (e.g., vitamin deficiency, toxicant exposure) disrupts the epigenetic information in sperm or egg cells that make a new embryo. This, in turn, might affect which genes turn on/off during development of the baby and even later in that individual's lifetime. For example, if certain genes in the offspring are affected, this might lead to birth defects (e.g. neural tube defects [NTDs]) or metabolic disease (e.g. diabetes). Metabolic disease might be an important factor in recreating abnormal epigenetic information in the new sperm or egg, thus creating a cycle of TEI. These complex questions about TEI will be explored in our proposed research. We will study a mouse model that cannot properly metabolize folate and as a result, inheritance of birth defects over multiple generations occurs. Folate (also known as folic acid) is a vitamin that is important for producing methyl groups required for epigenetic control of gene expression. The role of folate metabolism in TEI is unclear and will be explored in this study. In addition to abnormal folate metabolism, our mice display atypical epigenetic profiles in sperm of the grandfather including alterations in DNA methylation and small RNA content. We will determine whether small RNA content in sperm is specifically responsible for the birth defects observed in our model. To do this, we will inject specific small RNAs into 1-cell mouse embryos and assess the frequency of birth defects alongside changes in the epigenome and gene expression over multiple generations in direct comparison to our folate model. Additionally, we will assess whether there are metabolic changes in our model outside of folate metabolism that might aid in recreating abnormal epigenetic profiles in sperm to help perpetuate TEI. Overall, our study aims to further the understanding of how TEI occurs in mammals. In the UK, it is suggested that pregnant women take folate to reduce the risk of NTDs in the baby, though uptake is low. Our work suggests that men should also consider folate supplementation when conceiving. Furthermore, human birth defects without an apparent cause might be attributed to a folate-deficient grandparent. This research indicates the importance of folate fortification programs in the prevention of birth defects, yet the full effects may take several generations to resolve.