Characterization of the earliest thalamocortical interactions in vivo and in vitro

体内和体外最早丘脑皮质相互作用的表征

• 批准号: 2266057
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2266057
• 关键词: Characterization; earliest; thalamocortical; interactions; vivo

The degree to which intrinsic versus extrinsic factors control the development of the cerebral cortex has been the subject of sustained research. While there is a large body of evidence for an early control of patterning that is intrinsic to the neocortex, a major extrinsic source of patterning is provided by the thalamo-cortical afferents (TCA) that reach to the developing cortex at very early stages, before the peak of neurogenesis and neuronal migration take place. We are interested in this complex array of external signals that regulate region-specific cortical development, and their interplay with the mechanisms intrinsic to cortical progenitors and neurons. We are particularly interested in how area-specific TCA begin to influence corticogenesis in the germinal zone and start to influence initial circuit formation at very early stages, when this extrinsic contribution might underlie major differences in the region-specific developmental programme of cortical progenitors and early postmytotic neurons in higher-order mammals. The first compartment of the developing cortex reached by the early-incoming TCAs is the subplate (SP) zone, a transient embryonic cortical compartment which is greatly expanded in size and complexity during primate evolution, culminating in humans. This structure contains a heterogeneous population of cells and it contributes to the guidance and areal targeting of TCA at early stages of corticogenesis. Intriguingly, SP abnormalities have been implicated in the pathogenesis of human developmental disorders including cerebral palsy, childhood epilepsy, schizophrenia and autism. Moreover, recent observations in our laboratory suggest that the outer subventricular zone (oSVZ), a unique germinal zone present specifically in higher-order mammals, might represent another initial target of TCA during the initial phases of corticogenesis. The establishment of such connection would provide a better explanation to the dramatic reduction in neuronal numbers in primary visual cortex reported in anophtalmic human and enucleated non-human primate models, thus further confirming a crucial role of TCA in shaping the earliest compartments of the developing neocortex. Together these observations raise the hypothesis of an unexpected major role of TCA in early areal specification -especially in primates-, and the SP and oSVZ might represent the anatomical correlates of the interaction between intrinsic and extrinsic regulatory events. We will address the large expansion of the SP and oSVZ in concomitance with TCA early-arrival in the developing cortex, by investigating the cell types as well as the specific molecular mechanisms involved in the establishment of a functional interaction among these components. To this aim, we will perform tracing analysis and immunohistochemical staining in human post-mortem foetal tissues, embryonic macaque tissue (provided by our collaborators), as well as in mouse models, in order to cover a wide range of time-points throughout early cortical development and compare the main processes involved in different species. Once we will characterise the cellular subtypes involved in this interaction, we will further dissect the molecular pathways underlying its effect, and validate the data obtained ex-vivo/in-vivo in an in-vitro setting. The latter approach would entail modelling a simplified version of human (and mouse) early corticogenesis in a dish by organotipic cultures in the first place, and by more complex 3D cellular models (cerebral organoids fused with thalamic organoids) at a later stage of the project. This would allow us not only to confirm the data we will obtained in post-mortem human tissues (and ex-vivo murine samples for direct comparison) but it would also provide a novel optimized in-vitro model of human early thalamo-cortical interaction where further analyses could be done in the future, by testing genetic manipulations and/or pharmacological treatments on this system.

内在因素与外在因素控制大脑皮层发育的程度一直是持续研究的主题。虽然有大量证据表明新皮质固有的模式形成的早期控制，但模式形成的主要外在来源是由丘脑皮质传入神经（TCA）提供的，TCA 在神经发生和神经元迁移高峰发生之前的非常早期阶段到达发育中的皮质。我们对调节特定区域皮质发育的一系列复杂的外部信号及其与皮质祖细胞和神经元固有机制的相互作用感兴趣。我们特别感兴趣的是区域特异性 TCA 如何开始影响生发区的皮质生成，并在非常早期阶段开始影响初始回路的形成，而这种外在贡献可能是高阶哺乳动物皮质祖细胞和早期有丝分裂后神经元的区域特异性发育程序发生重大差异的基础。早期进入的 TCA 到达的发育皮质的第一个区室是板下区 (SP)，这是一个短暂的胚胎皮质区室，在灵长类动物进化过程中其大小和复杂性大大扩展，在人类中达到顶峰。该结构包含异质细胞群，有助于在皮质生成的早期阶段指导和区域靶向 TCA。有趣的是，SP 异常与人类发育障碍的发病机制有关，包括脑瘫、儿童癫痫、精神分裂症和自闭症。此外，我们实验室最近的观察结果表明，外脑室下区（oSVZ）是高阶哺乳动物中特有的独特生发区，可能代表皮质生成初始阶段 TCA 的另一个初始目标。这种联系的建立将为无眼人类和去核非人类灵长类动物模型中报道的初级视觉皮层神经元数量的急剧减少提供更好的解释，从而进一步证实TCA在塑造发育中新皮层的最早区室中的关键作用。这些观察结果共同提出了 TCA 在早期区域规范（尤其是灵长类动物）中发挥意想不到的重要作用的假设，并且 SP 和 oSVZ 可能代表了内在和外在调节事件之间相互作用的解剖学相关性。我们将通过研究细胞类型以及在这些成分之间建立功能相互作用所涉及的特定分子机制，解决 SP 和 oSVZ 的大规模扩张，以及 TCA 早期到达发育中皮层的问题。为此，我们将对人类死后胎儿组织、胚胎猕猴组织（由我们的合作者提供）以及小鼠模型进行示踪分析和免疫组织化学染色，以覆盖整个早期皮质发育的广泛时间点，并比较不同物种涉及的主要过程。一旦我们确定了参与这种相互作用的细胞亚型的特征，我们将进一步剖析其作用背后的分子途径，并在体外环境中验证在体外/体内获得的数据。后一种方法首先需要在培养皿中通过器官培养物模拟人类（和小鼠）早期皮质生成的简化版本，并在项目的后期阶段通过更复杂的 3D 细胞模型（大脑类器官与丘脑类器官融合）进行建模。这不仅使我们能够确认从死后人体组织（以及用于直接比较的离体小鼠样本）中获得的数据，而且还提供了一种新型的优化的人类早期丘脑-皮质相互作用的体外模型，通过测试该系统的基因操作和/或药物治疗，将来可以进行进一步的分析。