Hippocampal channelopathies in Fragile X Syndrome

 描述(申请人提供)：我们建议从脆性X综合征(FXS)的fmr1/y小鼠模型中研究最近发现的两种树突状通道病在海马锥体神经元中的生理后果。尽管它们在神经元功能的调节中至关重要，但令人惊讶的是，关于FXS中离子通道功能的生理学研究很少。这一点特别值得注意，因为FXS中缺失的FMRP蛋白与20多个编码许多离子通道蛋白的mRNAs结合，包括推测的A型K+通道亚基KV4.2和h通道亚基HCN2，并通过蛋白质-蛋白质相互作用调节离子通道功能。A型K+通道和h通道对海马树突状细胞的综合特性有很强的影响，部分原因是它们具有很高的树突状表达和特定的生物物理特性。我们建议使用全细胞和细胞附着电生理记录结合单细胞钙成像来研究iH和IkA的变化如何改变fmr1-/y小鼠CA1锥体神经元远端树突的整合特性。我们还将使用电生理学结合免疫组织化学和Western blotting来研究这两种通道病变是否持续存在于海马体的背腹轴。最后，我们将调查成年小鼠局部恢复FMRP表达是否可以挽救FXS中发生的细胞和行为异常。该项目将首次对脆性X综合征中通道病变对树突状细胞功能的影响进行生理学研究。

 DESCRIPTION (provided by applicant): We propose to investigate the physiological consequences of two recently identified dendritic channelopathies in hippocampal pyramidal neurons from the fmr1-/y mouse model of Fragile X syndrome (FXS). Despite their critical importance in the regulation of neuronal function, there have been surprisingly few physiological investigations of ion channel function in FXS. This is particularly noteworthy, because FMRP, the protein that is missing in FXS, binds to more than twenty mRNAs encoding a number of ion channel proteins, including the putative A-type K+ channel subunit KV4.2 and the h-channel subunit HCN2, and modulates ion channel function via protein-protein interactions. A-type K+ channels and h-channels have a strong influence over the integrative properties of hippocampal dendrites in part because of their very high dendritic expression and specific biophysical properties. We propose to use whole-cell and cell-attached electrophysiological recording in combination with single cell calcium imaging to investigate how changes in Ih and IKA alter the integrative properties of the distal dendrites of CA1 pyramidal neurons in the fmr1-/y mouse. We will also use electrophysiology in combination with immunohistochemistry and western blotting to investigate whether these two channelopathies persist across the dorsal-ventral axis of the hippocampus. Lastly, we will investigate whether regional restoration of FMRP expression in adult mice can rescue the cellular and behavioral abnormalities that occur in FXS. This project will provide the first physiological investigation of the impact of channelopathies on dendritic function in Fragile X syndrome.