整个小鼠大脑中 CRH 神经元的单细胞形态特征,BMC Biology

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整个小鼠大脑中 CRH 神经元的单细胞形态特征
BMC Biology ( IF 4.4 ) Pub Date : 2021-03-15 , DOI: 10.1186/s12915-021-00973-x
Yu Wang ₁ , Pu Hu ₁ , Qinghong Shan ₁ , Chuan Huang ₁ , Zhaohuan Huang ₁ , Peng Chen ₁ , Anan Li _{2,

3} , Hui Gong _{2,

3} , Jiang-Ning Zhou _{1,

2}

Affiliation

促肾上腺皮质激素释放激素 (CRH) 是一种重要的神经调节剂，广泛分布于大脑中，在介导应激反应和自主神经功能中起关键作用。虽然已经在不同的转基因小鼠品系中研究了荧光标记的 CRH 表达神经元的分布模式，但对这一群体的广泛多样性和局部神经连接的全面了解只能来自将单细胞形态信息整合为一个定义特征。然而，单个 CRH 神经元的形态和由这些神经元形成的局部回路尚未在全脑和树突尺度水平上获得。我们筛选了表达 EYFP 的 CRH-IRES-Cre；Ai32 小鼠系通过使用荧光微光学切片断层扫描 (fMOST) 系统揭示整个小鼠大脑中单个 CRH 神经元的形态。在不同的大脑区域中发现了 CRH 神经元的不同树突形态和投射纤维。后续重建显示下丘脑 CRH 神经元具有最小的体体积和最简单的树突分支，并且几个大脑区域的 CRH 神经元具有共同的双极形态。对内侧前额叶皮层局部 CRH 神经元的进一步研究揭示了 CRH 神经元的体细胞深度依赖性形态，表现出三种类型的相互连接：基底树突（上层）与顶端树突（第 3 层）；树突体细胞连接（在第 2/3 层）；和树突-树突连接（在第 4 层中）。而且，下丘脑CRH神经元根据其躯体位置和树突静脉曲张的特征分为两种类型。前小细胞区的延髓突出 CRH 神经元的树突静脉曲张越来越少，而脑室周围区域的 CRH 神经元有更多和更大的静脉曲张，存在于投射到第三脑室的树突中。检测到CRH神经元的树枝状树突棘，其中最复杂的类型在杏仁核中发现，最简单的类型在下丘脑中发现。通过使用 CRH-IRES-Cre;Ai32 小鼠系和 fMOST 成像，我们获得了整个小鼠大脑中树突水平的 CRH 神经元区域特异性形态分布。综合起来，

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Single-cell morphological characterization of CRH neurons throughout the whole mouse brain

Corticotropin-releasing hormone (CRH) is an important neuromodulator that is widely distributed in the brain and plays a key role in mediating stress responses and autonomic functions. While the distribution pattern of fluorescently labeled CRH-expressing neurons has been studied in different transgenic mouse lines, a full appreciation of the broad diversity of this population and local neural connectivity can only come from integration of single-cell morphological information as a defining feature. However, the morphologies of single CRH neurons and the local circuits formed by these neurons have not been acquired at brain-wide and dendritic-scale levels. We screened the EYFP-expressing CRH-IRES-Cre;Ai32 mouse line to reveal the morphologies of individual CRH neurons throughout the whole mouse brain by using a fluorescence micro-optical sectioning tomography (fMOST) system. Diverse dendritic morphologies and projection fibers of CRH neurons were found in various brain regions. Follow-up reconstructions showed that hypothalamic CRH neurons had the smallest somatic volumes and simplest dendritic branches and that CRH neurons in several brain regions shared a common bipolar morphology. Further investigations of local CRH neurons in the medial prefrontal cortex unveiled somatic depth-dependent morphologies of CRH neurons that exhibited three types of mutual connections: basal dendrites (upper layer) with apical dendrites (layer 3); dendritic-somatic connections (in layer 2/3); and dendritic-dendritic connections (in layer 4). Moreover, hypothalamic CRH neurons were classified into two types according to their somatic locations and characteristics of dendritic varicosities. Rostral-projecting CRH neurons in the anterior parvicellular area had fewer and smaller dendritic varicosities, whereas CRH neurons in the periventricular area had more and larger varicosities that were present within dendrites projecting to the third ventricle. Arborization-dependent dendritic spines of CRH neurons were detected, among which the most sophisticated types were found in the amygdala and the simplest types were found in the hypothalamus. By using the CRH-IRES-Cre;Ai32 mouse line and fMOST imaging, we obtained region-specific morphological distributions of CRH neurons at the dendrite level in the whole mouse brain. Taken together, our findings provide comprehensive brain-wide morphological information of stress-related CRH neurons and may facilitate further studies of the CRH neuronal system.

更新日期：2021-03-15

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