Stem cell- based studies of gene-environment interactions in PTEN- associated autism

虽然自闭症谱系障碍(ASD)具有高度的遗传性，但很明显，也有很强的环境因素 在ASD发病机制中起重要作用。ASD经常与大脑增大有关，这通常是存在的。 并影响多种细胞类型，这表明早期干细胞或祖细胞群体的功能障碍 对ASD病因学的贡献。我们假设大脑的增大与增强的自我更新有关 神经干细胞(NSCs)导致神经发生和异常连接的增加 在ASD中观察到。与自闭症相关的肿瘤抑制基因PTEN的突变 巨头畸形的表型几乎都是杂合子(HET)，尽管小鼠的HET突变很少产生或 轻微的脑部异常。人类PTEN HET突变可能与脑部自闭症有关，也可能与其无关 过度生长本身，但可以作为遗传易感性与环境因素相结合， 影响它们的功能。ASD的一个已知环境风险因素可能与遗传风险因素相互作用 母体炎症反应(MIR)。尽管MIR与自闭症和大脑都有关联 对于过度生长，其潜在病理影响的生物学机制仍不清楚。我们将测试 假设MIR暴露产生的活性氧物种(ROS)可以增加干细胞自身 PTEN可逆性氧化失活在人神经干细胞中的更新和神经再生 蛋白质和随后增强的PI3K途径的激活，并且这种作用被 PTEN杂合性突变。为了做到这一点，我们将使用最先进的方法来产生淋巴细胞来源的 从我们独特的临床人群中诱导出具有PTEN HET突变的多潜能干细胞(IPSCs)， 大脑过度生长，自闭症和未受影响的亲属。然后我们将从前脑的神经干细胞 IPSCs来测试PTEN突变与ROS相互作用以促进异常程度的自我 更新增殖和神经再生。这将通过将细胞直接暴露于ROS以及 已知由MIR产生的候选炎性细胞因子，进而可以激活 ROS生产。我们将确定导致细胞表型改变的分子机制 我们可以通过分析PI3K和其他可能与PI3K途径相互作用的途径来观察。 我们还将确定不同形式的PTEN HET突变是否会导致不同水平的 残留的PTEN功能对ROS/细胞因子刺激的反应不同。这些研究将阐明 遗传易感性与接触MIR的关系可能会影响小说的发展 通过确定对共同环境风险因素的易感机制进行干预。调查结果 这项研究也将对环境自闭症风险因素的易感性产生更广泛的影响 由于有许多不同的遗传易感性可以与MIR相互作用，直到最终 在大脑发育的关键时期导致神经干细胞功能改变的常见途径。 。

While autism spectrum disorders (ASD) are highly heritable, it is clear that there is also a strong environmental component to ASD pathogenesis. ASD is frequently associated with brain enlargement, which is often present at birth and affects multiple cell types, suggesting that dysfunction in an early stem or progenitor population contributes to ASD etiology. We hypothesize that brain enlargement is related to enhanced self-renewal of neural stem cells (NSCs) leading in turn to increased neurogenesis and abnormal connectivity that has been observed in ASD. Mutations in the tumor suppressor PTEN that are observed in association with the autism macrocephaly phenotype are almost all heterozygous (HET), although HET mutations in mice produce few or subtle brain abnormalities. PTEN HET mutations in humans may or may not contribute to autism with brain overgrowth on their own but could act as a genetic susceptibility in combination with environmental factors that affect their function. One known environmental risk factor for ASD that might interact with genetic risk factors is the Maternal Inflammatory Response (MIR). Although MIR has been linked to both autism and to brain overgrowth, the biologic mechanisms for its potential pathological effects remain undefined. We will test the hypothesis that reactive oxygen species (ROS) generated by MIR exposure can increase stem cell self- renewal and neurogenesis in human neural stem cells through the reversible oxidative inactivation of PTEN protein and subsequent enhancement of PI3K pathway activation and that this effect is enhanced by heterozygous PTEN mutation. To do this we will use state of the art methods to generate lymphocyte-derived induced pluripotent stem cells (iPSCs) from our unique clinical population with identified PTEN HET mutations, brain overgrowth, and autism and from unaffected relatives. We will then derive forebrain NSCs from the iPSCs to test the hypothesis that PTEN mutations interact with ROS to promote an abnormal degree of self- renewing proliferation and neurogenesis. This will be done by directly exposing cells to ROS as well as to candidate inflammatory cytokines that are known to be produced by MIR, and, which, in turn could activate ROS production. We will determine the molecular mechanisms underlying the altered cellular phenotypes that we may observe through the analysis of the PI3K and other pathways that may interact with the PI3K pathway. We will also determine whether different forms of PTEN HET mutations which may result in different levels of residual PTEN function respond differently to ROS/cytokine stimulation. These studies will elucidate the relationship between genetic susceptibility and exposure to MIR that could inform the development of novel interventions by identifying mechanisms of susceptibility to a common environmental risk factor. The findings obtained in this study will also have broader implications for susceptibility to environmental autism risk factors due to the fact that there are many different genetic susceptibilities that may interact with MIR through final common pathways which lead to altered neural stem cell function during critical periods in brain development. .