Molecular and cellular basis for autism spectrum disorders caused by exacerbated translation

摘要 自闭症谱系障碍(ASD)是一种神经发育障碍，在两个核心领域存在缺陷：社交 互动和交流，以及重复行为或限制性行为。它被诊断了四次 男孩比女孩更常见。在ASD的大量风险基因中，蛋白质合成增加 被认为是一种汇聚的病理机制。ASD与高比例的 PTEN、TSC1、TSC1等负性翻译调控因子基因突变失活患者 TSC2和FMR1。这些突变增加了真核细胞翻译起始因子4E(EIF4E)的可用性， 从而提高了一组选择性mRNAs的翻译。然而，它仍然不知道是哪种类型的 以及翻译水平升高如何导致神经回路功能障碍，进而导致自闭症 行为。我们已经产生了一种敲入小鼠品系，其中eIF4E从rosa26过表达 Cre依赖的方式。我们发现eIF4E在小胶质细胞中过表达，但不是神经元或 星形胶质细胞仅在雄性小鼠中导致ASD样突触和行为异常，包括树突状细胞增加 脊柱密度，兴奋/抑制失衡，社交障碍，重复行为增加，以及 选择性认知缺陷。我们进一步发现，小胶质细胞eIF4E的过度表达提高了两者的翻译水平 但只增加了男性的小胶质细胞密度和大小。鉴于小胶质细胞在突触中的关键作用 我们假设，某些蛋白质的合成增加只会改变雄性小鼠的小胶质细胞功能， 这反过来会损害突触的发育，从而损害偏向男性的自闭症。我们将在 遵循三个具体目标。目的1是研究蛋白质升高的分子机制。 合成改变小胶质细胞；目标2是了解ASD性二型性的机制- 与MG4E小鼠相似的表型；目标3是确定小胶质细胞变化如何通过以下方式影响突触发育 对照和MG4E小鼠树突棘和小胶质细胞的体内成像动态。这项研究项目将 不仅提供了对负翻译调节因子突变的病理机制的洞察 导致ASD，但也显示小胶质细胞功能障碍可能是ASD的病因之一。它还可能揭示一种 ASD强烈的男性偏见的基础机制，这可以指导创新的治疗策略 这是一种混乱。

Summary Autism spectrum disorder (ASD) is a neurodevelopmental disorder with deficits in two core domains: social interaction and communication, and repetitive behaviors or restrictive behaviors. It is diagnosed four times more frequently in boys than in girls. Among a large number of risk loci for ASD, elevated protein synthesis has been recognized as a converging pathological mechanism. ASD is associated with a high percentage of patients with inactivating mutations in genes for several negative translation regulators, such as PTEN, TSC1, TSC2 and FMR1. These mutations increase the availability of eukaryotic translation initiation factor 4E (eIF4E), consequently elevating translation of a selective group of mRNAs. However, it remains unknown in which type of brain cells and how elevated translation leads to dysfunction of neural circuits and subsequently ASD behaviors. We have generated a knock-in mouse strain in which eIF4E is overexpressed from the Rosa26 locus in a Cre-dependent manner. We found that eIF4E overexpression in microglia, but not neurons or astrocytes, led to ASD-like synaptic and behavioral aberrations only in male mice, including increased dendritic spine density, excitation/inhibition imbalance, social interaction impairment, increased repetitive behavior, and selective cognitive deficits. We further found that microglial eIF4E overexpression elevated translation in both sexes but only increased microglial density and size in males. Given critical roles of microglia in synapse development, we posit that elevated synthesis of some proteins alters microglial functions only in male mice, which in turn impairs synapse development and thereby male-biased ASD. We will test this hypothesis in the following three specific aims. Aim 1 is to investigate the molecular mechanism by which elevated protein synthesis alters microglia; Aim 2 is to understand the mechanism underlying the sexual dimorphism of ASD- like phenotypes in MG4E mice; Aim 3 is to determine how microglial alterations impact synapse development by imaging in vivo dynamics of dendritic spines and microglia in control and MG4E mice. This research project will not only provide insights into the pathological mechanism by which mutations in negative translation regulators lead to ASD, but also show microglial dysfunction as a possible etiology of ASD. It may also uncover a mechanism that underlies the strong male bias of ASD, which could guide strategies for innovative therapies of the disorder.