A MITOCHONDRIAL-INTERNEURONAL HYPOTHESIS OF AUTISM

孤独症的线粒体-神经元间假说摘要：孤独症是一种神经行为障碍， 病因不明的疾病，影响68名儿童中的一名。我们假设自闭症的一个主要原因 谱系障碍（ASD）风险是部分线粒体功能障碍，导致中间神经元抑制， 发育性迁移缺陷。这导致皮质神经元兴奋-抑制失衡。部分 在ASD中反复观察到线粒体功能障碍。自闭症谱系障碍患者的脑电图异常为 可能是GABA能抑制性中间神经元来源。中间神经元是高度精力充沛和急性敏感， 线粒体抑制和皮层兴奋-抑制失衡与ASD行为相关 异常广泛的核DNA（nDNA）遗传学研究已经确定了多种ASD相关的 haploinsufficient位点，每一个都占几个病例，这意味着有一千多个ASD位点。的 线粒体基因组由一到两千个nDNA基因加上数千个拷贝的 线粒体DNA（mtDNA），因此部分线粒体功能障碍可由nDNA单倍不足或 有害的mtDNA变异体。我们已经证明，许多ASD相关的nDNA单倍不足变异体， 影响线粒体功能，某些mtDNA谱系（单倍型组）与ASD风险相关， ASD相关的mtDNALeu（UUR）nt 3243 A>G突变导致线粒体功能障碍和线粒体膜电位紊乱 多个ASD nDNA基因的表达，OXPHOS的化学和遗传抑制影响中间神经元 皮质发育迁移，并且携带轻度mtDNA突变的小鼠表现出ASD相关的 包括EEG异常在内的内表型。为了进一步测试线粒体缺陷-中间神经元失衡 假设我们提出三个具体目标。首先，我们将确定ASD患者的mtDNA序列 和对照使用脱靶外显子组序列数据或直接mtDNA测序， 单倍群和最近的有害突变与ASD风险。然后将分析ASD相关的mtDNA 线粒体功能障碍的研究其次，我们将分析16p11.2 CNV ASD 细胞系的线粒体功能障碍和改变的转录谱，并比较结果ASD mtDNALeu（UUR）nt 3243 A>G胞质杂种。然后我们将确定mtDNA变异如何影响临床变异性 与16p11.2 CNVs相关。最后，我们将确定神经元间特异性nDNA的作用， 线粒体基因和系统性mtDNA基因缺陷对皮层中间神经元发育迁移的影响， ASD内在表型和社会行为畸变的相关表现。小鼠 内表型，但非明显的ASD样行为将暴露于多聚（I：C）诱导的子宫内炎症， 确定他们是否更容易诱发类似ASD的行为。如果通过这些实验验证， 线粒体缺陷-中间神经元不平衡假说可以涵盖几乎所有不同的 与ASD相关的观察。

A MITOCHONDRIAL-INTERNEURONAL HYPOTHESIS OF AUTISM Abstract: Autism is a neurobehavioral disorder of unknown etiology that affects one in 68 children. We hypothesize that a major contributor to autism spectrum disorder (ASD) risk is partial mitochondrial dysfunction causing interneuron inhibition and developmental migration defects. This results in cortical neuronal excitation-inhibition imbalance. Partial mitochondrial dysfunction has been repeatedly observed in ASD. ASD patients exhibit EEG abnormalities of likely GABAergic inhibitory interneuron origin. Interneurons are highly energetic and acutely sensitive to mitochondrial inhibition and cortical excitation-inhibition imbalance is associated with ASD behavioral abnormalities. Extensive nuclear DNA (nDNA) genetic studies have identified multiple ASD-associated haploinsufficient loci, each accounting for a few cases, implying that there are over a thousand ASD loci. The mitochondrial genome consists of between one and two thousand nDNA genes plus thousands of copies of the mitochondrial DNA (mtDNA), so partial mitochondrial dysfunction can result from nDNA haploinsufficiency or deleterious mtDNA variants. We have shown that many ASD-associated nDNA haploinsufficiency variants affect mitochondrial functions, that certain mtDNA lineages (haplogroups) correlate with ASD-risk, that the ASD-associated mtDNALeu(UUR) nt 3243A>G mutation results in mitochondrial dysfunction and perturbation of expression of multiple ASD nDNA genes, that chemical and genetic inhibition of OXPHOS impacts interneuron cortical developmental migration, and that mice harboring mild mtDNA mutants exhibit ASD-associated endophenotypes including EEG abnormalities. To further test the mitochondrial defect-interneuron imbalance hypothesis we propose three specific aims. First, we will determine the mtDNA sequences of ASD patients and controls using off-target exome sequence data or direct mtDNA sequencing and correlate the mtDNA haplogroups and recent deleterious mutations with ASD risk. ASD-associated mtDNAs will then be analyzed for mitochondrial dysfunction within transmitochondrial cybrids. Second, we will analyze 16p11.2 CNV ASD cell lines for mitochondrial dysfunction and altered transcription profiles and compare the results to ASD mtDNALeu(UUR) nt 3243A>G cybrids. We will then determine how mtDNA variation affects the clinical variability associated with 16p11.2 CNVs. Finally, we will determine the effect of interneuron-specific nDNA mitochondrial gene and systemic mtDNA gene defects on cortical interneuron developmental migration and associated manifestation of ASD endophenotypes and social-behavioral aberrations. Mice with endophenotypes but non-overt ASD-like behavior will be exposed to poly (I:C)-induced in utero inflammation to determine if they are more prone to induction of ASD-like behavior. If validated by these experiments our mitochondrial defect-interneuron imbalance hypothesis can encompass virtually all of the disparate observations associated with ASD.