Impact of BDNF SNP on stroke-induced plasticity and motor function

描述（由申请人提供）：由于中风引起结构可塑性和行为适应，促进中风后功能恢复的策略得到了前瞻性的关注。脑源性神经营养因子（BDNF）在中枢神经系统修复和可塑性中起着至关重要的作用。bdnf基因前域的单核苷酸多态性（SNP）在人类中出现频率很高。然而，该SNP对中枢神经系统恢复的影响一直存在争议。目前的提案通过研究BDNF SNP在多大程度上影响中风后运动恢复，使用在两个等位基因（BDNFMet/Met）或一个等位基因（BDNF+/Met）中含有人源化SNP的小鼠来解决这一争议。尽管急性期损伤更大，但与野生型（WT）小鼠相比，BDNFMet/Met小鼠在卒中恢复期表现出意想不到的运动/步态功能增加，特别是在同侧后肢，并且未损伤半球纹状体体积增加。这伴随着这一半球兴奋性突触标记物基因表达的增加。由于活动调节的BDNF分泌对抑制性突触的成熟很重要，而这种类型的分泌在BDNFMet/Met神经元中减少，我们假设BDNFMet等位基因通过减少抑制性突触来促进代偿性运动恢复，从而导致对侧纹状体的突触兴奋和肥大。目的1将验证BDNFMet等位基因通过对侧纹状体的作用促进运动恢复的假设。使用缺血性中风小鼠WT、BDNF+/Met和BDNFMet/Met，我们将评估运动功能，分析亚区体积，并通过评估对侧纹状体急性药物失活后的行为变化来解决对侧纹状体的重要性。目的2将验证BDNFMet等位基因诱导突触变化并将纹状体中的突触平衡转移到兴奋状态的假设。详细的神经元形态和突触特性的变化将被研究。我们已经证明BDNFMet/Met小鼠显示炎症受体CD36的表达增加，CD36在先天免疫和伤口愈合中起作用，它的配体血小板反应蛋白（tsp）也参与兴奋性突触的形成。因此，我们将在Aim 3中验证CD36通路通过对侧纹状体的突触兴奋参与BDNFMet等位基因诱导的突触可塑性和运动恢复的假设。在脑卒中后WT和BDNFMet/Met小鼠中评估CD36、tsp、兴奋性和抑制性突触标志物。CD36在BDNFMet等位基因诱导的脑可塑性中的重要性将在缺乏CD36的BDNFMet/Met小鼠或用CD36拮抗剂治疗的小鼠中得到解决。从这些研究中获得的见解将为预测与BDNF SNP携带者相关的中风恢复过程提供一种手段。此外，确定激活CD36通路的关键窗口可能会导致促进不携带SNP的中风患者运动恢复的治疗策略。

DESCRIPTION (provided by applicant): As stroke induces structural plasticity and behavioral adaptation, strategies that promote functional recovery following stroke have gained prospective attention. Brain-derived neurotrophic factor (BDNF) plays a critical role in CNS repair and plasticity. A single nucleotide polymorphism (SNP) of the prodomain of the bdnf gene occurs with high frequency in humans. However, the effect of this SNP on CNS recovery has been controversial. The current proposal addresses this controversy by investigating the extent to which BDNF SNP impacts motor recovery following stroke using mice that contain humanized SNP in both alleles (BDNFMet/Met) or one allele (BDNF+/Met). In spite of greater impairments during the acute phase, BDNFMet/Met mice displayed an unexpected increase in motor/gait function during the stroke recovery phase, especially in the ipsilateral hind limb, and increased striatal volume in the non-injured hemisphere compared to wild type (WT) mice. This was accompanied by increased gene expression of excitatory synaptic markers in this hemisphere. Since activity-regulated BDNF secretion is important for the maturation of inhibitory synapses, and this type of secretion is reduced in BDNFMet/Met neurons, we hypothesize that the BDNFMet allele promotes compensatory motor recovery by reducing the inhibitory synapses leading to synaptic excitation in, and hypertrophy of, the contralateral striatum. Aim 1 will test the hypothesis that the BDNFMet allele promotes motor recovery via effects in the contralateral striatum. Using WT, BDNF+/Met, and BDNFMet/Met mice subjected to ischemic stroke, we will assess motor functions, analyze sub-region volume, and address the importance of the contralateral striatum by assessing behavior changes after acute pharmacological inactivation of the contralateral striatum. Aim 2 will test the hypothesis that the BDNFMet allele induces synaptic changes and shifts synaptic balance to an excitatory status in the striatum. Detailed neuronal morphology and changes in synaptic properties will be investigated. We have shown that BDNFMet/Met mice display increased expression of the inflammatory receptor CD36, which functions in innate immunity and wound healing, and also of its ligand thrombospondins (TSPs) that are involved in the formation of excitatory synapses. We will therefore test the hypothesis that the CD36 pathway contributes to BDNFMet allele-induced synaptic plasticity and motor recovery through synaptic excitation in the contralateral striatum in Aim 3. CD36, TSPs, excitatory and inhibitory synaptic markers will be assessed in WT and BDNFMet/Met mice following stroke. The importance of CD36 in BDNFMet allele-induced brain plasticity will be addressed in BDNFMet/Met mice that lack CD36 or in mice that have been treated with a CD36 antagonist. The insight gained from the studies will provide a means to predict the course of stroke recovery relevant to BDNF SNP carriers. In addition, defining a critical window for activating the CD36 pathway may lead to therapeutic strategies for promoting motor recovery in stroke patients who do not carry the SNP.