Role of HCN1 channels in the function and malfunction of parvalbumin positive interneurons

项目摘要 最近的临床发现涉及编码超极化激活的基因的从头突变 严重形式的儿童癫痫患者的HCN1阳离子通道。与此同时，全基因组的关联 研究表明，HN1基因与精神分裂症有很强的联系。在这里，我们旨在提供一个详细的 描述甲型流感病毒在正常神经功能中的作用，并确定甲型流感病毒如何致病 突变会扰乱神经活动，导致大脑功能紊乱。甲型H1N1流感渠道的不同寻常之处在于 被膜超极化激活，但传导向内去极化的Na/K电流，并表现出 在表达它们的不同类别的神经元中，亚细胞定位的对比模式。 因此，该通道在海马CA1层和新皮质第5层锥体神经元中强烈表达，其中 它的目标是顶端树突，其密度随着距离的增加而显著增加。 索玛。HCN1也在小白蛋白阳性抑制神经元(PV INS)中强烈表达，相比之下， 对于锥体神经元，它定位于PV的轴突和突触前终末。小鼠全身或全身炎症反应的研究 前脑限制性基因缺失揭示了该通道作为负性基因的重要作用 限制海马区锥体神经元树突整合和长时程突触可塑性 依赖海马体的空间记忆。HCN1基因缺失降低锥体神经元定位细胞的精确度 空间编码，同时增加了空间表示的稳定性。与经过充分研究的角色不同 HCN1在锥体神经元功能中的作用，目前对其在抑制性神经元中的作用知之甚少。这 缺乏信息阻碍了对甲型H1N1流感如何对正常大脑功能和 鉴于抑制性神经元，特别是PV INS在这些过程中的重要性，疾病。此外, 因为在被检测的hcn1基因敲除小鼠中，hcn1被同时从兴奋性和抑制性神经元中删除。 到目前为止，已报道的学习和记忆以及体内激发特性的变化反映了 HCN1在兴奋性神经元和抑制性神经元中的作用尚不清楚。在我们的应用程序中，我们建议在 详细说明甲型H1N1流感如何在细胞、体内网络和行为水平上促进PV IN的功能。我们会 因此，探索：野生型HCN1在调节PV的内在兴奋性和突触前功能中的作用(AIM 1)；癫痫相关的HCN1突变如何扰乱PV IN的功能(目标3a)；如何选择性地删除 来自PV INS的野生型HCN1改变了体内对空间信息以及空间和非空间信息的编码 记忆行为(目标2)；以及某些抗癫痫药物增加癫痫发作的矛盾效应 携带癫痫相关的HCN1突变的小鼠(目标3b)。我们在这些研究中的目标是既提供 关于在特定类别神经元中表达的给定通道如何对大脑做出贡献的基本信息 功能，并提供对疾病机制的新见解，可能会提出新的治疗方法。

Project Summary Recent clinical findings implicate de novo mutations in the gene encoding the hyperpolarization-activated HCN1 cation channel in severe forms of childhood epilepsy. At the same time genome-wide association studies demonstrate a strong link of the HCN1 locus with schizophrenia. Here we aim to provide a detailed characterization of the role of HCN1 in normal neural function, and to determine how disease-causing HCN1 mutations perturb neural activity to generate disordered brain function. HCN1 channels are unusual in that they are activated by membrane hyperpolarization, yet conduct an inward depolarizing Na+/K+ current, and show a contrasting pattern of subcellular localization in the distinct classes of neurons in which they are expressed. Thus, the channel is strongly expressed in hippocampal CA1 and neocortical layer 5 pyramidal neurons, where it is targeted to the apical dendrites in a striking gradient of increasing density with increasing distance from the soma. HCN1 is also strongly expressed in parvalbumin-positive inhibitory neurons (PV INs), where, in contrast to pyramidal neurons, it is targeted to PV IN axons and presynaptic terminals. Studies of mice with a general or forebrain-restricted genetic deletion of HCN1 have revealed the important role of this channel as a negative constraint of hippocampal pyramidal neuron dendritic integration and long-term synaptic plasticity, and of hippocampal-dependent spatial memory. Loss of HCN1 decreases the precision of pyramidal neuron place cell spatial coding while increasing the stability of spatial representations. In contrast to the well-studied role of HCN1 in pyramidal neuron function, relatively little is known about the role of HCN1 in inhibitory neurons. This lack of information prevents a full appreciation as to how HCN1 contributes to both normal brain function and disease, given the importance of inhibitory neurons, and PV INs in particular, in these processes. In addition, because HCN1 was deleted from both excitatory and inhibitory neurons in the HCN1 knockout mice examined to date, the extent to which the reported alterations in learning and memory and in vivo firing properties reflect the role of HCN1 in excitatory versus inhibitory neurons is unclear. In our application we propose to examine in detail how HCN1 contributes to PV IN function at the cellular, in vivo network, and behavioral levels. We will thus explore: the role of wild-type HCN1 in regulating PV IN intrinsic excitability and presynaptic function (Aim 1); how PV IN function is perturbed by epilepsy-associated HCN1 mutations (Aim 3a); how selective deletion of wild-type HCN1 from PV INs alters the in vivo coding of spatial information, as well as spatial and non-spatial memory behavior (Aim 2); and the paradoxical effects of certain anti-epileptic drugs to increase seizures in mice harboring epilepsy-associated HCN1 mutations (Aim 3b). Our goal in these studies is to both provide basic information about how a given channel expressed in a specific class of neurons contributes to brain function, and to provide new insights into disease mechanisms that may suggest new therapeutic approaches.