Gene-Environment Interactions Resulting in Neural Tube Defects with 22q11 Deletions

项目摘要/摘要 维生素A及其生物活性代谢物维甲酸(RA)在形成 发育中的胚胎。维生素A缺乏或过量都会导致各种发育异常， 包括颅面和心脏发育缺陷和神经管关闭(神经管缺陷， NTDS)。因此，RA水平和信号必须受到严格调控，才能正常发育。胚胎 通过改变RA缓冲机制(RA合成和降解)的表达来实现这一点 酶和RA结合蛋白)，以缓冲环境暴露中的微小变化。的表达 许多microRNAs(MiRNAs)受RA信号调控，miRNAs针对RA缓冲机制。 因此，miRNAs在调节构成RA的负反馈环和正反馈环方面处于有利地位 胚胎的缓冲能力。 我们公布的数据表明，DiGeorge/22q11缺失综合征的LgDel小鼠模型 (22q11DS)表现出功能失调的RA缓冲能力。这会导致NTDS的发生率增加，当 在RA暴露中面临正常良性改变的挑战。22q11DS是最常见的基因缺失 人类中每4000名活产儿中就有一人患有综合症。22q11DS的特征差异很大，最常见的是 与心脏和颅面部缺陷有关；然而，据报道，许多NTDS病例发生在 22q11缺失。Dgcr8/Pasha是微处理器复合体的基本组件，负责 产生成熟的miRNAs，位于22q11缺失区域。而DgCr8+/-胚胎没有表现出 在出生后的小鼠中，描述了明显的胚胎表型和多种神经功能缺陷。 重要的是，神经缺陷伴随着Dgcr8+/-脑中miRNAs表达的改变 小鼠和其他小鼠模型的22q11DS以及外周血和 诱导22q11DS患者的多能干细胞(IPSCs)。因此，Dgcr8的单倍性不足可能具有 对成熟miRNAs表达的关键影响，可能会在miRNA加工中造成瓶颈。 大多数NTDS、心脏和颅面部缺陷是由于复杂的基因-环境相互作用造成的。 已知一些导致NTDS的环境触发因素，但确定的遗传因素很少。 此外，环境和遗传因素如何相互作用导致NTDS在很大程度上仍未确定。我们的 LgDel胚胎具有发育中NTDS的RA缓冲能力障碍的发现提供了一种新的 有机会剖析基因-环境相互作用可能扭转平衡的机制 NTDS。在这项建议中，我们将测试在LgDel胚胎中Dgcr8单倍性不足的假设 导致miRNA处理的瓶颈和RA缓冲能力的失调。

Project Summary/Abstract Vitamin A and its biologically active metabolite Retinoic Acid (RA) play critical roles in patterning the developing embryo. Vitamin A deficiency or excess can cause a variety of developmental abnormalities, including defects in craniofacial and cardiac development and neural tube closure (Neural Tube Defects, NTDs). Thus, RA levels and signaling must be tightly regulated for normal development to occur. The embryo accomplishes this by altering the expression of the RA buffering machinery (RA synthetic and degradation enzymes along with RA binding proteins) to buffer small alterations in environmental exposure. Expression of many microRNAs (miRNAs) are regulated by RA signaling and miRNAs target the RA buffering machinery. Thus miRNAs are well positioned to mediate the negative and positive feedback loops that constitute the RA buffering capacity of the embryo. Our published data demonstrate that the LgDel mouse model of DiGeorge/22q11 deletion syndrome (22q11DS) exhibits dysfunctional RA buffering capacity. This results in increased incidence of NTDs when challenged with normally benign alterations in RA exposures. 22q11DS is the most frequent gene deletion syndrome in humans affecting 1 in 4000 live births. Features of 22q11DS vary widely and are most commonly associated with cardiac and craniofacial defects; however, many cases of NTDs are reported in patients with 22q11 deletions. Dgcr8/Pasha, is an essential component of the microprocessor complex responsible for generating mature miRNAs and is located within the 22q11 deletion. While Dgcr8+/- embryos do not exhibit obvious embryonic phenotypes, multiple defects in neuronal function are described in postnatal mice. Importantly, neurological deficits are accompanied by altered expression of miRNAs in the brain of Dgcr8+/- mice and other mouse models of 22q11DS as well as altered miRNA expression in peripheral blood and induced pluripotent stem cells (iPSCs) from 22q11DS patients. Thus haploinsufficiency of Dgcr8 can have a critical impact on expression of mature miRNAs, possibly creating a bottleneck in miRNA processing. The majority of NTDs, cardiac and craniofacial defects are due to complex gene-environment interactions. Some environmental triggers contributing to NTDs are known, yet few genetic factors have been identified. Moreover, HOW environmental and genetic factors interact to cause NTDs remains largely undetermined. Our finding that the LgDel embryo has dysfunctional RA buffering capacity developing NTDs provides a novel opportunity to dissect the mechanisms by which gene-environment interactions might tip the balance to cause NTDs. In this proposal we will test the hypothesis that haploinsufficiency of Dgcr8 in the LgDel embryo results in a bottleneck in miRNA processing and dysfunctional RA buffering capacity.