The role of inhibitory neurons in microcephaly and seizure caused by Asparagine synthetase (ASNS) deficiency

抑制性神经元在天冬酰胺合成酶（ASNS）缺乏引起的小头畸形和癫痫发作中的作用

• 批准号: 9470436
• 负责人: Xiaodi Yao
• 金额: $ 6.76万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-12-01 至 2021-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9470436
• 关键词: Acute Lymphocytic Leukemia; Address; Affect; Asparagine; Aspartate; Aspartate-Ammonia Ligase; Behavior; Behavioral; Biological Models; Blood; Body Size; Brain; Brain Mass; Case Study; Cell Cycle; Cell Cycle Progression; Cell Proliferation; Cell Survival; Cellular biology; Cerebral cortex; Cerebrospinal Fluid; Childhood; Clinic; Clinical; Data; Development; Disease; Electrophysiology (science); Embryo; Epilepsy; Epileptogenesis; Functional disorder; Future; G1 Phase; Generations; Genes; Genetic; Genetic Models; Glutamine; Goals; Growth; Human; Image; Impairment; Intellectual functioning disability; Interneurons; Intervention; Knock-out; Knockout Mice; Knowledge; Link; Mammals; Mentors; Microcephaly; Modeling; Molecular; Molecular Biology; Mus; Mutant Strains Mice; Mutation; Neocortex; Neurobiology; Neurodevelopmental Disorder; Neurologic; Neurologist; Neurons; Non-Essential Amino Acid; Parvalbumins; Pathogenesis; Patients; Penetrance; Perinatal; Phenotype; Physicians; Plasma; Proteins; Reporting; Research; Research Personnel; Role; Scientist; Seizures; Slice; Supplementation; Synapses; System; Techniques; Technology; Testing; Therapeutic; Therapeutic Intervention; Training; asparaginase; brain size; calretinin; cancer cell; career development; cell growth; cell type; chemotherapy; excitatory neuron; experience; experimental study; genetic approach; in vivo; inhibitory neuron; insight; loss of function; mouse model; nerve stem cell; nervous system disorder; nestin protein; neurogenetics; neurophysiology; neurotransmission; novel; patient subsets; postnatal; progenitor; response

Asparagine synthetase deficiency (ASNSD) is a recently identified autosomal recessive neurological disorder characterized by severe microcephaly, intellectual disability and intractable seizures. ASNSD is caused by mutations in the ASNS gene which encodes asparagine synthetase (ASNS). A known function of ASNS is to catalyze the conversion from aspartate and glutamine to asparagine (ASN). Thus, one tempting hypothesis is that ASNS deficiency results in low levels of ASN, which in turn impede neural progenitor cell proliferation during earlier stages of brain development, and subsequent neurological impairments such as microcephaly and seizures. In fact, a subset of ASNSD patients are found to have low plasma or CSF ASN levels. However, it was reported in one case study that an ASNSD patient showed only initial response to ASN intervention. Thus, it is critical to definitively determinate the function of ASNS and effects of ASNS deficiency in brain development, and establish the causal relationship between low ASN levels and ASNSD in a valid model system. To better understand ASNSD, I have generated a number of Asns knockout (KO) mouse models. Importantly, brain-specific KO of Asns results in severe microcephaly and spontaneous seizures, suggesting a specific and critical role for ASNS in brain development. Surprisingly, unlike known microcephaly models which caused by significant loss of cortical excitatory neurons, a drastic reduction in cortical interneurons in brain-specific Asns KO brain was observed. This data suggest a critical role of ASNS in interneuron development. In line with this observation, Asns KO in cortical excitatory neurons fails to induce microcephaly and seizure. Thus, I hypothesize that alterations in the development and function of selective inhibitory neurons underlie the pathophysiology of the microcephaly and seizure phenotypes in ASNSD. The objective of the study is to dissect the mechanistic link underlying the neurological impairments and evaluate the therapeutic intervention of ASN supplementation in various Asns mutant mice. Overall, this proposed study will provide mechanistic insight to the pathogenesis of ASNSD and the role of interneurons in early brain development. Additionally, this proposed research will test for a potential therapeutic strategy to ASNSD. Execution of the proposed training plan will not only expend my knowledge on neurobiology and neurodevelopmental disorder research, but also advance my training in mouse model generation and characterization, and allow me to master a number of neurophysiology techniques, cutting edge imaging and analytic technologies. These newly obtained knowledge and techniques will be critical supplements to my existing expertise in molecular and cell biology research. This broad spectrum of research expertise and diverse research experiences will be essential for my future career development into an independent investigator.

天冬酰胺合成酶缺乏症（ASNSD）是一种常染色体隐性遗传病 以严重小头畸形、智力残疾和顽固性 癫痫发作。ASNSD是由编码天冬酰胺合成酶的ASNS基因突变引起的 （ASNS）。ASNS的一个已知功能是催化天冬氨酸和谷氨酰胺转化为 天冬酰胺（天冬酰胺）。因此，一个诱人的假设是，ASNS缺乏导致低水平的β-淀粉样蛋白， 这反过来又会在大脑发育的早期阶段阻碍神经祖细胞增殖， 随后的神经损伤，如小头畸形和癫痫发作。事实上，ASNSD的一个子集 发现患者具有低血浆或CSF β 2水平。然而，在一个案例研究中报告说， ASNSD患者仅显示出对药物干预的初步反应。因此，至关重要的是， 确定ASNS的功能及ASNS缺乏对脑发育的影响，建立ASNS缺乏的脑发育模型， 在一个有效的模型系统中，低浓度的尼古丁和ASNSD之间的因果关系。更好地 为了了解ASNSD，我已经建立了许多Asns敲除（KO）小鼠模型。重要的是， Asns的脑特异性KO导致严重的小头畸形和自发性癫痫发作，这表明 ASNS在大脑发育中特殊和关键作用。令人惊讶的是，与已知的小头畸形不同， 模型由皮层兴奋性神经元的显著损失，皮层神经元的急剧减少， 观察到脑特异性Asns KO脑中的中间神经元。这些数据表明ASNS在以下方面的关键作用： 中间神经元发育与这一观察结果一致，皮质兴奋性神经元中的Asns KO未能使皮质兴奋性神经元中的Asns KO降低。 导致小头畸形和癫痫发作。因此，我推测，在发育和功能上的改变 选择性抑制性神经元的作用是小头畸形和癫痫发作的病理生理学基础 ASNSD中的表型。这项研究的目的是剖析机械联系的基础上， 神经系统损伤，并评估各种疾病中补充维生素B2的治疗干预 Asns突变小鼠。总的来说，这项拟议的研究将提供机制洞察的发病机制， ASNSD和中间神经元在早期脑发育中的作用。此外，这项研究建议 将测试ASNSD的潜在治疗策略。执行拟议的培训计划不会 我不仅在神经生物学和神经发育障碍研究方面扩展了我的知识，而且 推进我在小鼠模型生成和表征方面的培训，并让我掌握一个 许多神经生理学技术，尖端成像和分析技术。这些新 所获得的知识和技术将是我现有的分子生物学专业知识的重要补充。 和细胞生物学研究。这种广泛的研究专业知识和多样化的研究经验 这对我将来成为一名独立调查员至关重要。