SNX14基因突变引起孤独症谱系障碍的致病机理研究

Autism spectrum disorders (ASD) is a neurodevelopmental disorder characterized by impaired social interactions, communication deficits, and repetitive behavior. Although the etiology of ASD remains obscure, it is commonly believed that genetic factors might be largely responsible for the occurrence of ASD. Recently genetic studies reported that individuals with SNX14 loss-of-mutations manifest intellectual disability and autistic-like behaviors. Due to the lack of Snx14-deficient animal models, the molecular mechanism of SNX14 deficiency in ASD is still unclear. Our preliminary results show that Snx14+/- mice exhibit impaired social behaviors, and we also found a reduced expression of synaptic proteins in Snx14+/- brains compared to wild-type control. Therefore, we hypothesize that loss of SNX14 disrupts synaptic function and neuronal circuits, causes autistic phenotype. In this proposal, we aim to generate a Snx14 conditional knockout (cKO) mouse model, and we will take advantage of a series of behavioral, electrophysiological, and synaptic morphological technique to identify their phenotypes and the underlying mechanisms. Moreover, we will determine whether restoration of SNX14 can rescue the behavioral and synaptic deficits of Snx14 cKO mice. Finally, we will elucidate the molecular networks of SNX14 mutation in ASD through identifying SNX14-interacting proteins, especially those synaptic proteins. Successful completion of this project will strengthen our understanding of SNX14 in ASD, and provide a novel genetic model for studying mechanisms of ASD and looking for potential therapies.

孤独症谱系障碍（ASD）是一类发育障碍性疾病，其发病原因不明，多数认为遗传因素占主导作用。新近的遗传学研究发现，携带SNX14基因功能丧失性突变的个体表现出孤独症样行为。但由于缺乏动物水平的研究，SNX14缺陷引起ASD的致病机理还不清楚。我们预实验结果证实Snx14杂合敲除的小鼠表现出孤独症样行为以及突触功能蛋白表达下调。因此我们提出假说：SNX14基因突变通过影响突触功能，使神经元间的连通异常，进而引发ASD。在本项目中，我们将构建Snx14脑特异性敲除小鼠，研究其孤独症样行为以及突触功能的缺陷。我们还将恢复缺陷小鼠脑SNX14表达，探索其行为和突触功能的改善情况。我们也将明确与SNX14的相互作用蛋白，特别是突触功能蛋白，进一步阐明SNX14基因突变导致突触缺陷和ASD的分子机制。本研究将提出ASD发病新的分子遗传学证据，并提供了一种新的ASD动物模型，用于机制研究和药物筛选评价。

SNX14基因突变导致常染色体隐性脊髓小脑共济失调症20（Autosomal recessive spinocerebellar ataxia 20，SCAR20），患者表现出自闭症样行为、智力障碍和运动共济失调，但由于缺乏动物水平的研究，SNX14缺陷引起SCAR20的致病机理还不清楚。在此，我们首次构建了SNX14在中枢条件性敲除的小鼠模型，全面的行为学分析显示该模型能很好地模拟临床病人。借助该模型，我们证实了兴奋性突触功能受损可能是引起SCAR20出现智力障碍的重要机制。我们也首次发现小脑浦肯野细胞自发性死亡是导致SCAR20出现共济失调的关键细胞生物学机制。分子机制方面，SNX14使spastin蛋白不稳定，导致了轴突线粒体运输障碍和线粒体功能受损，进一步引起小脑浦肯野细胞死亡。更重要的，我们发现临床抗癫痫常用药丙戊酸钠（VPA）可有效治疗SNX14缺陷导致的小脑共济失调，这为SCAR20临床治疗提供重要依据。研究达到了国际领先水平，具有较强的转化价值。