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

描述(申请人提供)：由于中风导致结构可塑性和行为适应，促进中风后功能恢复的策略受到了预期的关注。脑源性神经营养因子在中枢神经系统的修复和可塑性中起着重要作用。BDNF基因前结构域的单核苷酸多态(SNP)在人类中发生频率很高。然而，这种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的小鼠来研究BDNF SNP对中风后运动恢复的影响程度，以解决这一争议。尽管BDNFMet/Met小鼠在急性期受到更大的损害，但在中风恢复期，BDNFMet/Met小鼠的运动/步态功能意外增加，尤其是在同侧后肢，与野生型(WT)小鼠相比，非损伤半球的纹状体体积增加。伴随着这一半球兴奋性突触标志物基因表达的增加。由于活性调节的BDNF分泌对抑制性突触的成熟很重要，而且这种分泌在BDNFMet/Met神经元中减少，我们假设BDNFMet等位基因通过减少导致对侧纹状体突触兴奋和肥大的抑制性突触来促进代偿性运动恢复。目的1将验证BDNFMet等位基因通过影响对侧纹状体促进运动恢复的假设。使用WT、BDNF+/Met和BDNFMet/Met小鼠进行缺血性卒中，我们将评估运动功能，分析次区域体积，并通过评估对侧纹状体急性药物失活后的行为变化来说明对侧纹状体的重要性。目的2验证BDNFMet等位基因引起纹状体突触改变并使突触平衡进入兴奋性状态的假说。详细的神经元形态和突触特性的变化将被研究。我们发现BDNFMet/Met小鼠的炎症受体CD36及其配体血栓反应蛋白(TSP)的表达增加，CD36在先天免疫和伤口愈合中起作用，TSP参与兴奋性突触的形成。因此，我们将在Aim 3中验证CD36通路通过突触兴奋在对侧纹状体促进BDNFMet等位基因诱导的突触可塑性和运动恢复的假设。将在WT和BDNFMet/Met小鼠中风后评估CD36、TSPs、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小鼠或使用CD36拮抗剂治疗的小鼠中得到解决。从这些研究中获得的洞察力将为预测与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途径的关键窗口可能导致促进未携带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.