Inhibition of MMP-9 Activity Impairs Working Memory in Zebrafish Through Changes in Overall Hippocampal Excitation

摘要 全世界有超过3亿人患有重度抑郁症（MDD），这是一种异质性疾病， 无法治愈MDD与依赖于大脑的记忆障碍有关，包括严重的工作记忆障碍。 记忆（WM）缺陷。新获得的经验的编码和巩固依赖于精心调整的 锥体兴奋性神经元和GABA能小清蛋白阳性（PV）中间神经元之间的相互作用， 控制海马体中的兴奋与抑制（E/I）平衡。这两个神经元之间的相互作用 海马体中的细胞群导致锥体神经元的时间协调放电， 到θ/伽马振荡和尖波波纹（SWR）事件，作为适当编码的基础， 信息整合，分别。 在患有MDD的患者中，由于转变，编码和巩固经验都受到损害 海马体E/I平衡降低到不那么兴奋的状态。引人注目的是，我们的实验室已经证明抗抑郁药 文拉法辛通过增加γ振荡和SWR丰度挽救应激小鼠模型中的WM 在海马区。这种增加依赖于基质金属蛋白酶-9（MMP-9），一种明胶酶， 重塑细胞外基质并在MDD中改变。在这条研究路线之后，我的论文重点关注 MMP-9活性在脑缺血后海马依赖性神经元网络正常功能中的作用 斑马鱼我的行为数据表明，MMP-9抑制损害WM，这是伴随着变化， 海马体中的E/I平衡降低到较低的兴奋状态，如通过SWR丰度的降低所证明的。 此外，我的蛋白质组学数据表明，E/I平衡的变化可以通过两种蛋白质的变化来解释。 锥体和PV神经元。例如，纤溶酶原，兴奋性神经元活动的标志物， MMP-9抑制后下降。神经元周围网（PNN）的组成部分，调节PV的放电 神经元如多能蛋白聚糖显著增加。这些变化有助于减少兴奋性 类似于我们在抑郁症患者身上看到的。然后我的数据假设MMP-9活性 调节作为治疗抑郁症相关症状的潜在治疗靶点。 对于D-SPAN F99/K00培训补助金，我有两个具体目标。关于目标1（F99阶段），我概述了 到目前为止，我的进展，以及我将如何掌握全细胞膜片钳和光学传感记录，以区分 MMP-9抑制如何不同地影响锥体和PV神经元的内在特性，以及是否 θ/γ振荡也受到影响。顺利毕业后，对于K00阶段我会加入我的理想 R1机构的博士后实验室致力于科学卓越，专业和智力发展， 建立网络，增加和留住学术界的不同科学家。我也会继续研究细胞 以及在退化过程中导致神经回路受损的分子机制， 成为一名全面的神经科学家研究员和导师。

ABSTRACT Over 300 million people worldwide suffer from Major Depressive Disorder (MDD), a heterogenous disorder with no cure. MDD is associated with hippocampal-dependent memory impairments, including severe working memory (WM) deficits. The encoding and consolidation of newly acquired experiences rely on the finely tuned interplay between pyramidal excitatory neurons and GABAergic parvalbumin positive (PV) interneurons that control the excitation to inhibition (E/I) balance in the hippocampus. The interplay between these two neuronal populations in the hippocampus results in the temporally coordinated firing of pyramidal neurons that give rise to theta/gamma oscillations and sharp wave ripple (SWR) events, underlying the proper encoding and consolidation of information, respectively. In patients suffering from MDD both encoding and consolidation of experiences are impaired due to a shift in their hippocampal E/I balance to a less excitatory state. Strikingly, our lab has shown that the antidepressant venlafaxine rescues WM in a stress mouse model through increasing gamma oscillations and SWR abundance in the hippocampus. This increase was dependent on Matrix Metalloproteinase-9 (MMP-9), a gelatinase that remodels the extracellular matrix and is altered in MDD. Following in this line of research, my dissertation focuses on the role of MMP-9 activity in the proper functioning of hippocampal-dependent neuronal networks in the zebrafish. My behavioral data indicates that MMP-9 inhibition impairs WM, which was accompanied by changes in the E/I balance in the hippocampus to a less excitatory state as evidenced by a decrease in SWR abundance. Additionally, my proteomics data suggest that the shift in E/I balance can be explained by changes in both pyramidal and PV neurons. For instance, plasminogen, a marker for excitatory neuronal activity was significantly decreased after MMP-9 inhibition. Components of the Perineuronal Nets (PNN), that regulate the firing of PV neurons, such as versican, were significantly increased. These changes contribute to a less excitatory hippocampus similar to what we see in patients suffering from MDD. My data then postulates MMP-9 activity modulation as a potential therapeutic target to treating depression-related symptoms. For the D-SPAN F99/K00 training grant, I have two specific aims. For Aim 1 (F99 phase) I have outlined my progress thus far and how I will master whole-cell patch clamp and optical sensing recordings to distinguish how MMP-9 inhibition differentially affects the intrinsic properties of pyramidal and PV neurons and whether theta/gamma oscillations are also affected. After successfully graduating, for the K00 phase I will join my ideal postdoctoral lab at an R1 institution dedicated to scientific excellence, professional and intellectual development, networking, and increasing and retaining diverse scientists in academia. I will also continue studying the cellular and molecular mechanisms leading to neural circuitry impairment during degeneration while fostering my training towards becoming a well-rounded neuroscientist researcher and mentor.