Impact of intracellular chloride-dependent modulation of radial glia-like stem cells on hippocampal neurogenesis and the associated cognitive function in the aging brain

在啮齿动物、灵长类动物和人类的整个生命周期中，海马齿状回中的放射状胶质样干细胞（RGL）具有产生新神经元的能力。先前的研究表明，海马神经发生与学习、记忆和情绪行为密切相关。抑制性神经递质GABA通过GABAA受体起作用，调节成体神经发生的多个阶段，包括神经祖细胞增殖和迁移、神经元成熟、突触整合和存活。先前的研究已经调查了GABAA信号传导对神经干细胞和祖细胞增殖和分化的影响，以及其对海马干细胞网络活性控制的影响。然而，NKCC 1和KCC 2调节的细胞内氯离子水平在RGLs的年龄依赖性活性、神经干细胞自我更新、分化和存活中的作用仍然未知。几项研究表明，成年神经发生在老年大脑中严重受损，其特征在于RGL数量的持续减少。这种下降与年龄相关的认知能力下降和老年大脑再生能力下降有关。我们的初步数据显示，RGL中的NKCC 1敲除显著增加了老年脑中RGL、成熟神经元和星形胶质细胞的数量。本提案的目的是分析与细胞内氯离子水平的调制相关的海马中RGL激活和成人神经发生的新机制。因此，我们将利用新的转基因小鼠模型，在海马齿状回的RGL中特异性NKCC 1敲除（NestinCreERT 2/NKCC 1fl/fl/tdTomato小鼠）和KCC 2过表达（Nestin-rtTA/tetOKCC 2/tdTomato小鼠）。我们将确定细胞内氯化物水平调节对海马齿状回神经发生和衰老大脑认知功能的影响。在提案的第一部分，我们将确定RGL在不同年龄的单细胞（克隆分析）和群体水平（项目A）上的自我更新水平和命运。此外，我们将使用不同的认知行为测试（项目B），分析随着年龄增长而改变RGL激活的功能影响。我们的研究将有助于理解RGL激活的潜在机制及其参与的ag

Throughout the lifespan of rodents, primates and humans, radial glia-like stem cells (RGLs) in the hippocampal dentate gyrus have the capacity to produce new neurons. Previous studies have shown that hippocampal neurogenesis is critically involved in learning, memory and emotional behaviour. The inhibitory neurotransmitter GABA, acting via the GABAA receptor, regulates multiple stages of adult neurogenesis, including neural progenitor cell proliferation and migration, neuronal maturation, synaptic integration and survival. Previous studies have investigated the impact of GABAA signalling on proliferation and differentiation of neural stem and progenitor cells, as well as its influence on the control of network activity of hippocampal stem cells. However, the role of NKCC1- and KCC2-modulated intracellular chloride levels in the age-dependent activity of RGLs, neural stem cell self-renewal, differentiation and survival in the dentate gyrus remains unknown. Several studies showed that adult neurogenesis is severely impaired in the aged brain and is characterised by a continuous decrease in the number of RGLs. This decrease has been associated with the age-related cognitive decline and reduced regenerative capacity of the aged brain. Our preliminary data show that NKCC1 knockout in RGLs significantly increases the number of RGLs, mature neurons and astrocytes in the aged brain. The aim of the present proposal is to analyse new mechanisms of RGL activation and adult neurogenesis in the hippocampus associated with the modulation of intracellular chloride levels. Therefore, we will utilise novel transgenic mouse models for specific NKCC1 knockout (NestinCreERT2/NKCC1fl/fl/tdTomato mice) and KCC2 overexpression (Nestin-rtTA/tetOKCC2/tdTomato mice) in RGLs in the hippocampal dentate gyrus. We will determine the impact of intracellular chloride level modulation on neurogenesis in the hippocampal dentate gyrus and on cognitive function in the aging brain. In the first part of the proposal, we will determine the level of self-renewal and the fate of RGLs on the single-cell (clonal analysis) and population levels at different ages (Project A). Further, we will analyse the functional impact of changing RGL activation with increasing age, using different cognitive behavioural tests (Project B). Our study will contribute to the understanding of underlying mechanisms of RGL activation and their involvement in the ag