Understanding the role of the Glycine Cleavage System in Neural Tube Defects

了解甘氨酸裂解系统在神经管缺陷中的作用

• 批准号: MR/N003713/1
• 负责人: Nicholas Greene
• 金额: $ 109.42万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FN003713%2F1
• 关键词: Understanding; role; Glycine; Cleavage; System

Neural tube defects (NTDs) are common birth defects that arise in early pregnancy caused by incomplete formation of the neural tube, which will later develop into the brain and spinal cord. As a result, the brain and/or spinal cord of the fetus become irreversibly damaged, resulting in death around birth, or long term disability in surviving children. The most common forms of NTDs are anencephaly, affecting the brain, and spina bifida, which affects the lower spinal cord. They occur in approximately 1-2 per 1,000 pregnancies and total at least 170,000 new cases per year worldwide.The risk of NTDs depends on both inherited factors and environmental influences such as maternal diet, diabetes or exposure to certain chemicals. Because of the many possible contributory factors, the exact causes of NTDs in any affected individual are usually unknown. However, the risk of an affected pregnancy can be substantially reduced if the mother takes folic acid supplements before and during early pregnancy. Unfortunately, not all NTDs are prevented by folic acid - perhaps up to 50% of all cases fail to respond - and so additional therapies are needed. In order to make further progress towards prevention of all NTDs we need a better understanding of their causes, in particular the genes that increase a person's risk of NTD. Moreover, it will be important to identify new preventive therapies for NTDs which may be used individually or in combination with folic acid. In families where genetic risk factors have been identified this also means that family-specific therapies may be offered.All cells require efficient handling of small molecules called folates, which are related to folic acid, for many different functions. It appears that some NTDs are caused by an inherited abnormality in the way cells in the embryo handle folates. We studied a group of proteins called the "glycine cleavage system" (GCS), that are involved in folate handling. Some patients with NTDs had defects in these proteins, whereas unaffected people did not. This finding suggests that problems with the GCS may directly cause NTDs. In support of this idea, mouse embryos that have GCS defects also develop NTDs.This project will make use of mouse models lacking function of glycine decarboxylase (Gldc), part of the GCS. The mouse models provide an opportunity to study the role of these folate handling proteins in the embryo and how the associated NTDs may be prevented. We have found that handling of folates is altered in Gldc-deficient embryos and we will now use detailed metabolic studies to work out exactly how these changes come about. We will use genetic approaches to turn off Gldc function or to restore function only in the neural tube. This will tell us which tissues in the developing embryo need Gldc function, to ensure normal development.The next step is to understand which of the outputs of folate metabolism are disrupted in Gldc-deficient embryos and to test which of the changes are responsible for NTDs. This will be achieved by detailed biochemical analysis and embryo imaging using markers of particular cellular changes, followed by use of supplements to correct these defects. Folate metabolism is essential for synthesis of DNA, which is needed for cells to divide, and methylation reactions that modify gene expression and other functions. Folate metabolism may also be needed for regulation of the level of reactive oxygen species (free radicals) which can be damaging within cells. An imbalance in production and removal of these molecules, termed oxidative stress, is important in a number of diseases, including diabetes. We will examine whether Gldc-deficiency causes oxidative stress in developing embryos, that may contribute to NTDs.Understanding the molecular and cellular causes of NTDs in Gldc-deficient embryos is an important step towards developing new therapies to prevent more NTDs in humans than is currently possible using folic acid alone.

神经管缺陷（NTD）是一种常见的出生缺陷，发生在妊娠早期，由神经管的不完全形成引起，随后将发育成大脑和脊髓。结果，胎儿的大脑和/或脊髓受到不可逆的损伤，导致出生前后死亡，或存活儿童长期残疾。神经管畸形最常见的形式是影响大脑的无脑畸形和影响脊髓下部的脊柱裂。每1,000例妊娠中约有1-2例发生NTD，全世界每年至少有170，000例新病例。NTD的风险取决于遗传因素和环境影响，如母亲饮食、糖尿病或暴露于某些化学品。由于许多可能的促成因素，在任何受影响的个人NTD的确切原因通常是未知的。然而，如果母亲在怀孕前和怀孕早期服用叶酸补充剂，怀孕受影响的风险可以大大降低。不幸的是，并不是所有的NTD都可以通过叶酸预防-可能高达50%的病例没有反应-因此需要额外的治疗。为了在预防所有NTD方面取得进一步进展，我们需要更好地了解其原因，特别是增加NTD风险的基因。此外，重要的是要确定新的预防性治疗NTD可以单独使用或与叶酸联合使用。在已确定遗传风险因素的家庭中，这也意味着可以提供家庭特异性治疗。所有细胞都需要有效处理称为叶酸的小分子，叶酸与叶酸有关，具有许多不同的功能。有些NTD似乎是由胚胎细胞处理叶酸的方式遗传异常引起的。我们研究了一组被称为“甘氨酸裂解系统”（GCS）的蛋白质，它们参与叶酸处理。一些NTD患者在这些蛋白质中存在缺陷，而未受影响的人则没有。这一发现表明，GCS的问题可能直接导致NTD。为支持这一观点，存在GCS缺陷的小鼠胚胎也会产生NTD。本项目将利用缺乏GCS的一部分甘氨酸脱羧酶（Gldc）功能的小鼠模型。小鼠模型提供了研究这些叶酸处理蛋白在胚胎中的作用以及如何预防相关NTD的机会。我们发现Gldc缺陷胚胎中对叶酸的处理发生了改变，我们现在将使用详细的代谢研究来准确地找出这些变化是如何发生的。我们将使用遗传方法来关闭Gldc功能或仅在神经管中恢复功能。这将告诉我们发育中的胚胎中哪些组织需要Gldc功能，以确保正常发育。下一步是了解Gldc缺陷胚胎中叶酸代谢的哪些产物被破坏，并测试哪些变化是NTD的原因。这将通过详细的生化分析和使用特定细胞变化标记的胚胎成像来实现，然后使用补充剂来纠正这些缺陷。叶酸代谢对于细胞分裂所需的DNA合成以及修饰基因表达和其他功能的甲基化反应至关重要。叶酸代谢也可能需要调节活性氧（自由基）的水平，这可能会破坏细胞内。这些分子的产生和去除的不平衡，称为氧化应激，在许多疾病中很重要，包括糖尿病。我们将研究Gldc缺乏是否会导致发育中胚胎的氧化应激，这可能会导致NTDs。了解Gldc缺乏胚胎中NTDs的分子和细胞原因是开发新疗法的重要一步，以防止更多的NTDs在人类比目前可能单独使用叶酸。

项目成果

Glycine Cleavage System H Protein Is Essential for Embryonic Viability, Implying Additional Function Beyond the Glycine Cleavage System.

• DOI: 10.3389/fgene.2021.625120
• 发表时间: 2021
• 期刊: Frontiers in genetics
• 影响因子: 3.7
• 作者: Leung KY;De Castro SCP;Galea GL;Copp AJ;Greene NDE
• 通讯作者: Greene NDE

A targeted sequencing panel identifies rare damaging variants in multiple genes in the cranial neural tube defect, anencephaly.

• DOI: 10.1111/cge.13189
• 发表时间: 2018-04
• 期刊: Clinical genetics
• 影响因子: 3.5
• 作者: Ishida M;Cullup T;Boustred C;James C;Docker J;English C;GOSgene;Lench N;Copp AJ;Moore GE;Greene NDE;Stanier P
• 通讯作者: Stanier P

Oxidative Stress and Apoptosis in Benzo[a]pyrene-Induced Neural Tube Defects.

苯并[a]芘诱导的神经管缺陷中的氧化应激和细胞凋亡

• DOI: 10.1016/j.freeradbiomed.2018.01.004
• 发表时间: 2018-02-20
• 期刊: Free radical biology & medicine
• 影响因子: 7.4
• 作者: Lin S;Ren A;Wang L;Huang Y;Wang Y;Wang C;Greene ND
• 通讯作者: Greene ND

Microtubules, polarity and vertebrate neural tube morphogenesis.

• DOI: 10.1111/joa.12468
• 发表时间: 2016-07
• 期刊: Journal of anatomy
• 影响因子: 2.4
• 作者: Cearns MD;Escuin S;Alexandre P;Greene ND;Copp AJ
• 通讯作者: Copp AJ

Use of high-frequency ultrasound to study the prenatal development of cranial neural tube defects and hydrocephalus in Gldc-deficient mice.

• DOI: 10.1002/pd.5004
• 发表时间: 2017-03
• 期刊: Prenatal diagnosis
• 影响因子: 3
• 作者: Autuori MC;Pai YJ;Stuckey DJ;Savery D;Marconi AM;Massa V;Lythgoe MF;Copp AJ;David AL;Greene ND
• 通讯作者: Greene ND