Interneuron precursors and the ability to open new periods of cortical plasticity

描述（由申请人提供）：NINDS高级博士后职业过渡奖促进神经科学研究的多样性（K22）将通过扩展和发展他在干细胞移植方法和复杂的测量可塑性方法方面的博士后培训和专业知识，极大地促进候选人作为独立科学家开始职业生涯的能力。大多数前脑中间神经元起源于发育中的内侧神经节隆起（MGE），从那里迁移到皮层、海马、纹状体和杏仁核，形成局部抑制回路。当移植到幼鼠或成年小鼠皮层时，MGE细胞保留了迁移、功能整合和主要分化为表达gaba能的小白蛋白（PV）和生长抑素（SOM）皮质中间神经元的能力。先前的研究表明，gaba能抑制是诱导皮质可塑性和大脑修复所必需的。最近的实验室研究表明，将MGE细胞移植到新生或幼年小鼠的视觉皮层可以诱导一个新的眼优势可塑性（ODP）时期。这些细胞诱导新生可塑性的能力也为研究皮质可塑性的机制和限制提供了有力的工具。目前的建议有四个目的。在目的1中，我们将确定哪种类型的皮层中间神经元负责皮层可塑性的诱导。我们已经开发并验证了从MGE移植物中切除PV、SOM或两种细胞类型的遗传工具。先前的研究表明，PV电池可能对ODP的诱导负责，但这一假设尚未得到正式验证。令人惊讶的是，我们的初步研究表明，即使从MGE移植物中去除大多数PV电池，ODP仍然可以打开。我们将确定SOM中间神经元的损耗是否足以消除ODP，或者两个种群是否都有能力诱导ODP。在Aim 2中，我们将确定皮质中间神经元的移植是否可以扩展到成人大脑以诱导ODP并有助于功能恢复。我们已经开发并验证了光学记录技术来研究成年小鼠的ODP诱导。实验室也有初步证据表明，移植到成年小鼠皮层的MGE细胞可以迁移和整合，这表明它们也可以改变皮层回路，并可能诱发ODP。该奖项的独立阶段，将重点研究移植诱导的皮质可塑性的活动依赖机制。在Aim 3中，我们将探讨来自移植的MGE细胞的强gaba能传递是否对新生皮层可塑性是必要的。我们将利用遗传工具阻断突触传递，并在特定移植的MGE细胞中减少一半的gaba能传递。在Aim 4中，我们将使用基因编码的钙指标来测量移植和内源性PV+和SOM+中间神经元在新生竞争性皮质可塑性期间对两只眼睛的视觉反应变化。确定负责诱导可塑性的皮质中间神经元、可诱导的皮质可塑性的年龄范围和类型、gaba能传递的作用以及移植的MGE细胞在可塑性过程中如何变化，将为MGE细胞在脑修复中的治疗应用提供有价值的新信息。总而言之，本次职业转型奖提出的研究将使候选人能够开发一个完全独立的研究项目，能够以技术先进和高影响力的方式整合广泛的细胞和分子和系统方法，包括：(1)细胞移植方法在幼年和成年小鼠中开启皮层可塑性的新时期，(2)多点微电极在体内记录以测量所有皮层层的神经元反应和可塑性，(3)遗传方法来操纵特定抑制性微电路的突触传递，(4)一个模型系统来研究皮层可塑性的机制及其治疗潜力。

DESCRIPTION (provided by applicant): The NINDS Advanced Postdoctoral Career Transition Award to Promote Diversity in Neuroscience Research (K22) will significantly facilitate the candidate's ability to begin a career as an independent scientist, by extending and developing his postdoctoral training and expertise in stem cell transplantation methods and sophisticated methods to measure plasticity. Most forebrain interneurons originate in the developing medial ganglionic eminence (MGE), from where they migrate into cortex, hippocampus, striatum, and amygdala to form local inhibitory circuits. When transplanted into the juvenile or adult mouse cortex, MGE cells retain the ability for migration, functional integration, and differentiation primarily into parvalbumin (PV) and somatostatin (SOM) expressing GABAergic cortical interneurons. Previous work has shown that GABAergic inhibition is required for the induction of cortical plasticity and brain repair. Recent work in the laboratory showed that transplantation of MGE cells into the neonatal or juvenile mouse visual cortex can induce a new period of ocular dominance plasticity (ODP). The ability of these cells to induce plasticity de novo also offers a powerful tool to study the mechanisms and limits of cortical plasticity. The present proposal has four Aims. In Aim 1, we will determine which type of cortical interneuron is responsible for the induction of cortical plasticity. We have developed and validated genetic tools to ablate PV, SOM, or both cell types from the MGE grafts. Previous research suggests that PV cells may be responsible for the induction of ODP, but this hypothesis has not been formally tested. Surprisingly, our preliminary studies suggest that ODP can still be opened, even when most PV cells are eliminated from MGE grafts. We will determine if SOM interneuron depletion is sufficient for the elimination of ODP, or whether both populations have the capacity to induce ODP. In Aim 2, we will determine if the transplantation of cortical interneurons can be extended to the adult brain to induce ODP and contribute to recovery of function. We have developed and validated optical recording techniques to study ODP induction in adult mice. The laboratory also has preliminary evidence that MGE cells grafted into the adult mouse cortex migrate and integrate, suggesting that they could also modify cortical circuits and possibly induce ODP. The independent phase of the Award, will focus on the study of activity-dependent mechanisms of transplant- induced cortical plasticity. In Aim 3, we will explore whether potent GABAergic transmission from transplanted MGE cells is necessary for de novo cortical plasticity. We will use genetic tools to block synaptic transmission and reduce by half GABAergic transmission in specific transplanted MGE cells. In Aim 4, we will use genetically encoded calcium indicators to measure the changes in visual responses to the two eyes in transplanted and endogenous PV+ and SOM+ interneurons during de novo competitive cortical plasticity. The identification of cortical interneurons responsible for the induction of plasticity, the age range and types of cortical plasticity that can be induced, the role of GABAergic transmission, and how transplanted MGE cells change during plasticity will provide valuable new information for the therapeutic use of MGE cells in brain repair. In summary, the research proposed in this Career Transition Award will prepare the candidate to develop a fully independent research program capable of integrating a wide range of cellular and molecular and systems approaches in a technically advanced and high impact manner, including: (i) cell transplantation methods to open new periods of cortical plasticity in juvenile and adult mice, (ii) multisite microelectrode recordingsin vivo to measure neuronal responses and plasticity in all cortical layers, (iii) genetic methods to manipulate synaptic transmission of specific inhibitory microcircuits, and (iv) a model system to study the mechanisms of cortical plasticity and their therapeutic potential.