Restoring Brain Functions in Alzheimer Models with Interneuron Transplants

描述（由申请人提供）：阿尔茨海默病（AD）导致认知功能恶化和神经网络活动模式异常，但其潜在机制尚不清楚。我们最近发现，抑制小白蛋白中间神经元中电压门控钠通道Nav1.1水平的降低，对人类淀粉样蛋白前体蛋白（hAPP）转基因小鼠的神经网络活动和认知功能异常至关重要（Verret et al., 2012, Cell）。因此，我们提出验证抑制受损和振荡网络活动改变导致hAPPJ20小鼠和AD患者突触和网络损伤的过度假设。该提案将研究一种基于细胞的治疗方法，通过移植转基因胚胎中间神经元前体来增强hAPP小鼠的抑制性中间神经元功能，减少大脑网络和认知异常。来自内侧神经节隆起（medial ganglionic隆起，MGE）的胚胎前体细胞产生大量nav1.1阳性的抑制性中间神经元。mge衍生的中间神经元在移植到新生儿或成人寄主大脑后，仍然具有显著的迁移和整合能力，在那里它们成熟为功能性和突触活性的抑制性中间神经元。我们的初步数据表明，mge衍生的抑制性中间神经元逆转了hAPPJ20小鼠认知和情绪领域的行为异常，表明抑制性功能障碍有助于这些缺陷。有趣的是，过表达Nav1.1的mge衍生的中间神经元比野生型mge衍生的中间神经元更有效，这表明可能需要对这些前体进行遗传操作，使它们更能抵抗hAPP/A -毒性。因此，我们提出通过将具有野生型、高（Nav1.1 bac）和低（Nav1.1 r1407x） Nav1.1水平的转基因胚胎间神经元前体移植到宿主hAPPJ20和NTG小鼠中，来操纵hAPPJ20和NTG小鼠的抑制细胞活性。我们假设MGE移植会增加hAPPJ20小鼠中功能性抑制细胞的数量（Aim 1），改善或恢复抑制性和兴奋性突触活动（Aim 2），减少网络异常（Aim 3）和认知障碍（Aim 4）。因此，这种基于细胞的治疗方法将针对在hAPPJ20小鼠中诱导网络和认知功能障碍中起因果作用的关键细胞类型（PV细胞）和关键分子改变（降低Nav1.1）。此外，我们将研究基因操纵mge前体的方法，以增强其功能和/或对宿主大脑疾病机制的抵抗力。最初，mge衍生的抑制细胞将通过改变严密控制细胞兴奋性的Nav1.1水平来操纵。最后，这种实验方法将使我们能够在不同的宿主小鼠中特异性地操纵抑制性中间神经元，因此，在很大的机制细节上解决抑制功能的网络和细胞自主效应。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) results in deterioration of cognitive functions and abnormal patterns of neuronal network activity, but the underlying mechanisms are poorly understood. We recently found that reduced levels of the voltage-gated sodium channel Nav1.1 in inhibitory parvalbumin interneurons critically contribute to abnormalities in neuronal network activity and cognitive functions in human amyloid precursor protein (hAPP) transgenic mice (Verret et al., 2012, Cell). Thus, we propose to test the overreaching hypothesis that impaired inhibition and altered oscillatory network activity contribute to synaptic and network impairments in hAPPJ20 mice and possibly in humans with AD. The proposal will investigate a cell-based therapeutic approach to enhanced inhibitory interneuron function and reduce brain network and cognitive abnormalities in hAPP mice by transplanting genetically modified embryonic interneuron precursors. Embryonic precursor cells from the medial ganglionic eminence (MGE) generate large numbers of Nav1.1-postive inhibitory interneurons. MGE-derived interneurons retain a remarkable capacity to migrate and integrate when transplanted into neonatal or adult host brains where they mature into functional and synaptically active inhibitory interneurons. Our preliminary data indicate that MGE-derived inhibitory interneurons reverse behavioral abnormalities in cognitive and emotional domains in hAPPJ20 mice, suggesting that inhibitory dysfunction contributes to these deficits. Interestingly, MGE-derived interneurons overexpressing Nav1.1 were more effective than wildtype MGE-derived interneurons, indicating that genetic manipulations of these precursors might be required to make them more resistant to hAPP/A� toxicity. Thus, we propose to manipulate inhibitory cell activity in hAPPJ20 and NTG mice by grafting genetically modified embryonic interneuron precursors with wildtype, high (Nav1.1BAC), and low (Nav1.1R1407X) Nav1.1 levels into host hAPPJ20 and NTG mice. We hypothesize that MGE transplants will increase the number of functional inhibitory cells in hAPPJ20 mice (Aim 1), ameliorate or restore inhibitory and excitatory synaptic activity (Aim 2), and reduce network abnormalities (Aim 3) and cognitive impairments (Aim 4). Thus, this cell- based therapeutic approach will target a key cell type (PV cells) and a key molecular alteration (reduced Nav1.1) that play causal roles in inducing network and cognitive dysfunction in hAPPJ20 mice. In addition, we will investigate approaches to genetically manipulate MGE-precursors to enhance their functions and/or resistance to disease mechanisms of the host brain. Initially, MGE-derived inhibitory cells will be manipulated by altering Nav1.1 levels, which tightly controls cellular excitability. Finally, this experimental approach will allow us to specifically manipulate inhibitory interneurons in different host mice and, therefore, address network and cell-autonomous effects of inhibitory function in great mechanistic detail.