Background

CNIH3 is an AMPA receptor (AMPAR) auxiliary protein prominently expressed in the dorsal hippocampus (dHPC), a region that plays a critical role in spatial memory and synaptic plasticity. However, the effects of CNIH3 on AMPAR-dependent synaptic function and behavior have not been investigated.

Methods

We assessed a gain-of-function model of Cnih3 overexpression in the dHPC and generated and characterized a line of Cnih3^−/− C57BL/6 mice. We assessed spatial memory through behavioral assays, protein levels of AMPAR subunits and synaptic proteins by immunoblotting, and long-term potentiation in electrophysiological recordings. We also utilized a super-resolution imaging workflow, SEQUIN (Synaptic Evaluation and Quantification by Imaging of Nanostructure), for analysis of nanoscale synaptic connectivity in the dHPC.

Results

Overexpression of Cnih3 in the dHPC improved short-term spatial memory in female mice but not in male mice. Cnih3^−/− female mice exhibited weakened short-term spatial memory, reduced dHPC synapse density, enhanced expression of calcium-impermeable AMPAR (GluA2-containing) subunits in synaptosomes, and attenuated long-term potentiation maintenance compared with Cnih3^+/+ control mice; Cnih3^−/− males were unaffected. Further investigation revealed that deficiencies in spatial memory and changes in AMPAR composition and synaptic plasticity were most pronounced during the metestrus phase of the estrous cycle in female Cnih3^−/− mice.

Conclusions

This study identified a novel effect of sex and estrous on CNIH3’s role in spatial memory and synaptic plasticity. Manipulation of CNIH3 unmasked sexually dimorphic effects on spatial memory, synaptic function, AMPAR composition, and hippocampal plasticity. These findings reinforce the importance of considering sex as a biological variable in studies of memory and hippocampal synaptic function.

中文翻译：

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CNIH3 对空间记忆和突触可塑性作用的性别差异

背景

CNIH3 是一种 AMPA 受体 (AMPAR) 辅助蛋白，在背侧海马体 (dHPC) 中显着表达，该区域在空间记忆和突触可塑性中起着关键作用。然而，尚未研究 CNIH3 对 AMPAR 依赖性突触功能和行为的影响。

方法

我们评估了 dHPC 中Cnih3过表达的功能获得模型，并生成并表征了一系列Cnih3 ^-/- C57BL/6 小鼠。我们通过行为分析评估空间记忆，通过免疫印迹评估 AMPAR 亚基和突触蛋白的蛋白质水平，以及电生理记录中的长期增强。我们还利用超分辨率成像工作流程 SEQUIN（通过纳米结构成像进行突触评估和量化）来分析 dHPC 中的纳米级突触连接。

结果

dHPC 中Cnih3的过度表达改善了雌性小鼠的短期空间记忆，但在雄性小鼠中没有。与Cnih3 ⁺ /+对照小鼠相比， Cnih3 ^-/-雌性小鼠表现出短期空间记忆减弱、dHPC 突触密度降低、钙不可渗透 AMPAR（含 GluA2）亚基表达增强以及长期增强维持减弱; Cnih3 ^-/-雄性未受影响。进一步的研究表明，空间记忆的缺陷以及 AMPAR 组成和突触可塑性的变化在雌性Cnih3 ^-/-小鼠发情周期的发情末期最为明显。

结论

这项研究确定了性别和发情对 CNIH3 在空间记忆和突触可塑性中的作用的新影响。操纵 CNIH3 揭示了对空间记忆、突触功能、AMPAR 组成和海马体可塑性的性别二态效应。这些发现强化了在记忆和海马突触功能研究中将性别视为生物学变量的重要性。