Malfunctioning DDR and metabolism drive cerebellar pathologies in genetic instability disorders

基因组不断受到内源性和外源性破坏性侮辱的挑战。细胞进化两条关键的DNA损伤反应(DDR)途径，这两条途径由ATM和ATR介导。MRN(Mre11/Rad50/NBS1)复合体主要作用是激活ATM以响应DNA双链断裂(DSB)，并调节ATR的激活以响应复制压力。ATM、ATR、NBS1和Mre11基因突变分别导致共济失调-毛细血管扩张症(A-T)、塞克尔综合征(SS)、奈梅根破裂综合征(NBS)和A-T样障碍(A-TLD)。A-T和A-TLD与小脑变性有关，NBS和ATR-SS以小头畸形和智力低下为特征。众所周知，DDR分子和修复途径的突变会引起神经症状，这些症状往往与小脑缺陷有关，从而导致人类患者和小鼠模型的共济失调；然而，为什么小脑，而不是大脑皮层，容易受到DDR故障的影响，这是一个长期未解的谜。为了了解这些疾病的分子通路，已经建立了Nbs1、Mre11、ATM和ATR突变小鼠模型。我们发现，虽然ATR、Nbs1和Mre11不是有丝分裂后神经元存活所必需的，但它们还具有其他新的生理功能，例如在线粒体和代谢、血管完整性和突触前活动中。我们假设这些基因组不稳定障碍A-T、SS、A-TLD和NBS的神经缺陷是发育和代谢障碍，这些障碍是由这些DDR玩家的规范和非规范功能失效引起的。因此，我们建立了以下目标：(1)研究使小脑神经前体细胞对DDR功能障碍易感的分子途径(2)阐明代谢在DDR缺陷小脑磨损中的调节作用(3)为了发现和表征环境因素，如血管完整性在预防小脑缺陷中的作用，我们将采取以下方法：(I)DDR在小脑发育和维持中的分子和遗传学解剖。(2)综合组学，包括有针对性的代谢分析、神经元和非神经元细胞的单细胞RNA-SEQ以及神经元活动。(Iii)小脑血管完整性与大脑皮层的分子和影像分析。我们的研究将导致在神经疾病中发现受DDR蛋白控制的分子通路，特别是在基因组不稳定综合征中小脑的特异性。对共济失调相关疾病的本质的了解不仅将为个体提供药物治疗策略，还将有助于阐明小脑发育、功能及其维持的基础生物学。

The genome is constantly challenged by endogenous and exogenous damaging insults. Cells evolve two key DNA damage response (DDR) pathways, which are mediated by ATM and ATR. The MRN (MRE11/RAD50/NBS1) complex functions mainly to activate ATM in response to DNA double strand breaks (DSBs) and also regulates the ATR activation in response to replication stress. Mutations of ATM, ATR, NBS1 and MRE11 cause Ataxia-Telangiectasia (A-T), Seckel Syndrome (SS), Nijmegen Breakage Syndrome (NBS) and A-T Like Disorder (A-TLD), respectively. A-T and A-TLD are associated with cerebellar degeneration, NBS and ATR-SS are characterized by microcephaly and mental retardation. It is well known yet puzzling that mutations of DDR molecules and repair pathways cause neurological symptoms, which are often associated with defects in the cerebellum, leading to ataxia in human patients and mouse models; however, why cerebella, but not cerebral cortex, are vulnerable to DDR malfunction is a long-term unsolved mystery. To understand the molecular pathways of these disorders, Nbs1, Mre11, Atm, and Atr mutant mouse models have been generated. We found that although surprisingly Atr, Nbs1 and Mre11 are not required for survival of postmitotic neurons, they have other novel physiological functions, for example in mitochondria and metabolism, vascular integrity and presynaptic activities. We hypotheses that neurological defects of these genomic instability disorders A-T, SS, A-TLD and NBS are developmental as well as metabolic disorders and that these disorders are caused by the failure of the canonical as well as the non-canonical functions of these DDR players. We therefore set up the following objectives: (1) To study the molecular pathways that render the cerebellar neuroprogenitors susceptible to the DDR malfunction (2) To elucidate the function of metabolism as a regulator of cerebellar attrition of DDR deficiency(3) To discover and characterize the environmental factors such as vascular integrity in preventing cerebellar defects We will take the following approaches: (i) Molecular and genetic dissection of the DDR in cerebellar development and maintenance. (ii) Integrated omics including targeted metabolic analysis and single cell RNA-seq in neuron and non-neuronal cells as well as neuronal activity. (iii) Molecular and imaging analyses of vascular integrity in cerebella in comparison with cerebral cortices.Our study will lead to new discovery of molecular pathways that under control by the DDR proteins in neuropathies particularly the specificity of cerebella in genomic instability syndromes. The understanding of the nature of the ataxia related disorders will not only deliver pharmaceutical strategies for the individuals, but also shed light on the fundamental biology of the cerebellum development, functionality and its maintenance.