Tolls and neurotrophins in central nervous system regeneration and repair in Drosophila

中枢神经系统（CNS）中的细胞具有对变化做出反应的天然能力。神经胶质和神经元的数量、轴突、树突、回路和突触可以在发育过程中和整个生命过程中形成或消除，例如随着学习、锻炼和经验。通常，生成和破坏可塑性之间的平衡保持结构完整性和适当的行为。这种平衡会随着衰老、神经退化和脑肿瘤而消失。中枢神经系统在受损后不能再生，因此脑或脊髓损伤、中风和神经变性（例如阿尔茨海默病）会导致毁灭性的永久性残疾。发现和理解细胞可塑性的遗传机制是促进再生和修复的关键。Toll样受体（TLR）和神经营养因子（NT）配体都促进细胞的再生和破坏性变化。TLR是先天免疫的基础。在脑中，TLR存在于所有细胞中，并且TLR的改变是脑疾病的基础，例如中风、神经变性、多发性硬化和焦虑。TLR诱导小胶质细胞活化和碎片吞噬、细胞存活和死亡、神经突生长和塌陷。然而，它们在体内的功能知之甚少，它们的神经元功能和内源性CNS配体都是未知的。NT是主要的神经保护因子，NT问题是大多数脑疾病的基础，从神经变性到癫痫和抑郁症。NT促进神经元存活和连接到突触传递，在发育，学习和经验。NT也具有破坏性功能。我们发现Toll是果蝇神经营养素（DNT）的受体，人类的NT和TLR也可以相互作用。果蝇是一种非常有效的模式生物，可以在体内识别基因网络和测试基因功能，并且经常被用于研究再生和修复。在果蝇中发现的基因在哺乳动物中进行了测试，加快了人类健康的研究成果，并最大限度地减少了动物使用。我们发现了一种新的机制，在涉及DNT和Toll的神经回路中平衡细胞存活和死亡。我们还发现了神经胶质细胞对损伤的再生反应的基因网络，涉及NF κ B，Toll和TLR的通用效应子。初步研究结果表明，DNT和Toll可能参与神经胶质和神经元的再生。利用我们最近的研究结果，我们的目标是找出神经胶质和神经元如何引起协调的变化，以促进再生和修复。我们将测试不同的DNT/Toll/适配器模块调节神经胶质细胞，神经元和神经元-神经胶质细胞相互作用对损伤的反应的假设。22个基因和超过33种蛋白质可能参与其中。我们的策略将是确定与神经元或神经胶质最相关的模块，并在再生和修复中测试2-5。目的是：（1）可视化腹神经索（VNC）中DNT和Toll的分布图，并选择神经元和胶质细胞对。(2)我们预期在DNT-Toll相互作用中存在一些重叠和一些特异性，并且Toll对衔接子Wek的不同亲和力可以将其功能从神经保护转变为促凋亡。因此，为了缩小范围，我们将测试并选择最具体的DNT-Toll和Toll-Wek对。(3)测试所选的2-5个DNT/Toll/adaptor模块是否在体内调节神经胶质（细胞碎片吞噬、神经胶质增殖、轴突包裹）或神经元（神经保护、神经发生、轴突/树突模式和回路）对损伤的反应，以及操纵这些基因是否促进再生和修复。结果将是涉及DNT和Toll的用于CNS再生和修复的基因网络。即使不是所有的细节都是进化上保守的，我们的框架也将提供可以在哺乳动物中测试的精辟预测，最终有利于人类健康。

Cells in the central nervous system (CNS) have a natural ability to respond to change. Glial and neuronal number, axons, dendrites, circuits and synapses can be formed or eliminated during development and throughout life, such as with learning, exercise and experience. Normally, the balance between generative and destructive plasticity maintains structural integrity and appropriate behaviour. This balance fails with ageing, neurodegeneration and brain tumours. The CNS does not regenerate after damage, so injury to the brain or spinal cord, stroke and neurodegeneration (e.g. Alzheimer's disease) result in devastating permanent disability. Discovering and understanding genetic mechanisms underlying cell plasticity is key to promote regeneration and repair.Toll Like Receptors (TLRs) and neurotrophin (NT) ligands both promote generative and destructive cell change. TLRs underlie innate immunity. In the brain TLRs are in all cells, and alterations in TLRs underlie brain diseases, e.g. stroke, neurodegeneration, multiple sclerosis and anxiety. TLRs induce microglia activation and debris phagocytosis, cell survival and death, neurite growth and collapse. However their in vivo functions are poorly understood and their neuronal functions and endogenous CNS ligands, are both unknown. The NTs are the main neuroprotective factors, and NT problems underlie most brain diseases, from neurodegeneration to epilepsy and depression. NTs promote from neuronal survival and connectivity to synaptic transmission, in development, learning and with experience. NTs also have destructive functions. How NT functions are balanced in vivo, across cell types and circuits, is poorly understood.We discovered that Tolls are receptors for Drosophila neurotrophins (DNTs) in the fruit-fly, and that human NTs and TLRs can interact too. Drosophila is a very powerful model organism to identify gene networks and test gene function in vivo, and it is often used to investigate regeneration and repair. Genes discovered in fruit-flies are tested in mammals, expediting research findings for human health and minimizing animal use.We discovered a novel mechanism balancing cell survival and death during neural circuitry involving DNTs and Tolls. We also discovered a gene network underlying the glial regenerative response to injury that involves NFkB, the universal effector of Tolls and TLRs. Preliminary findings indicate that DNTs and Tolls could be involved in both glial and neuronal regeneration.Harnessing our recent findings, we aim to work out how glia and neurons elicit coordinated change, to promote regeneration and repair. We will test the hypothesis that distinct DNT/Toll/adaptor modules regulate the response of glial cells, neurons and neuron-glia interactions to injury. 22 genes and over 33 proteins are potentially involved. Our strategy will be to identify the modules most relevant for neurons or glia and test 2-5 in regeneration and repair. The objectives are: (1) to visualize a map of DNTs and Tolls in the ventral nerve cord (VNC), and select neuronal and glial pairs. (2) We anticipate some overlap and some specificity in DNT-Toll interactions, and differential affinities of Tolls for the adaptor Wek can shift their function from neuroprotective to pro-apoptotic. So to narrow down, we will test and select the most specific DNT-Toll, and Toll-Wek pairs. (3) Test whether the selected 2-5 DNT/Toll/adaptor modules regulate in vivo glial (cell debris phagocytosis, glial proliferation, axonal enwrapment) or neuronal (neuroprotection, neurogenesis, axonal/dendritic patterns and circuitry) responses to injury, and whether manipulating these genes promotes regeneration and repair.The outcome will be a gene network involving DNTs and Tolls for CNS regeneration and repair. Even if not all details were to be evolutionarily conserved, our framework will provide incisive predictions that can be tested in mammals, ultimately for the benefit of human health.