LSFM 实验和数据分析部分采用先进的光学显微镜, 在中央研究院仪器服务部门, 并在舒沈女士的协助下进行。我们感谢 IMB 的成像核心设施, Imaris 图像分析的大量技术援助苏女士。IMB 的科学英语编辑核心审查了手稿。这项工作由中央研究院职业发展奖 (CDA-107-L05)、多数 (104-2311-001-030-MY3) 和人权机构 (NHRI-EX106-10315NC) 资助。

所有活的动物都保存在一个特定的病原体免费 (SPF) 动物设施, 批准和监督的 IACUC 研究院。
1. 固定
<ol><li>收集胚胎12.5 天 (E12.5) 然后斩首和阉割他们。</li>
	<li>在1x 磷酸缓冲盐水 (PBS) 一夜之间, 将胚胎单独固定在24井板上, 1 毫升/井的新鲜制备的4% 多聚甲醛。在一个振动筛上孵化4摄氏度。</li>
	<li>将固定的胚胎至少洗 3x, 每5-10 分钟, 用1毫升 1x PBS, 并在4摄氏度在一夜床上孵化, 以除去残留的多聚甲醛。</li>
</ol>2. 全芒染色
<ol><li>Permeabilize 每个胚在1毫升 0.5% PBS-Triton-X-100 (PBST) 过夜在4°c 在一个振动筛。</li>
	<li>在 1x PBS 中, 每晚在4摄氏度的一个振动筛上, 用1毫升10% 胎的样品来阻断每个样本。</li>
	<li>用1毫升的抗 GFP 原抗体 (1:1, 000 稀释10% 血清) 在4摄氏度上孵化胚胎, 持续晃动以强化运动神经神经的 GFP 信号。</li>
	<li>在主抗体孵化后, 用1毫升 0.5% PBST, 在1-2 天的时间内, 在4摄氏度的振动筛上冲洗, 改变 0.5% PBST 至少三次。</li>
	<li>应用1毫升二次抗体 (1:1, 000 稀释在10% 血清) 和孵化夜间在黑暗中在4°c 与恒定的震动。</li>
	<li>洗涤3x 与1毫升 0.5% PBST 在4°c 在一个振动筛在2-3 天期间。将样品保持在 1x PBS 的4摄氏度, 直到成像前一天。 注意: 胚胎在清除前可以解剖成较小的部分, 这取决于胚胎的哪个部分会被成像。前肢是保存在这个实验方法 (图 1A)。</li>
	<li>在一个具有1.49 和1.5 毫升管的折射率的商业清除试剂中孵化胚胎, 在室温下防止夜间的光线, 从而使胚胎成像透明。 注: 清除试剂的体积约为样品体积的五倍。</li>
</ol>3. LSFM (2–3 h)
<ol><li>
示例设置
	<ol>
<li>设置 5 x/0.1 照明光学和 5 x/0.16 检测光学。组装样品持有人和样品毛细管 (1.5 毫米内径, 绿色), 并把它们放到显微镜。 注: 请参阅显微镜的操作手册, 以进行详细的设置程序。</li>
		<li>安装胚胎如下:<ol>
<li>P200 吸管尖端的切割, 使其适合毛细管直径, 并删除尖部 (~ 3 毫米) 的样品附件。</li>
			<li>用小火焰融化吸管尖端的钝端。</li>
			<li>熄灭火焰, 并迅速将胚胎垂直附着在融化的末端上。</li>
			<li>将吸管尖端的上部与样品毛细管配合使用。</li>
		</ol>
</li>
		<li>允许室缓冲与胚胎平衡1分钟清除碎片或气泡。</li>
		<li>使用成像软件, 在定位选项卡下选择定位毛细管, 并调整 x、y、z 轴以定位毛细管。</li>
		<li>选择定位示例并缩放到0.6X 以关注胚胎。旋转胚胎以确保成像肢体的长轴与两个光源 (图 1B) 的光路径对齐。</li>
	</ol>
</li>
	<li>
图像采集
	<ol>
<li>在获取选项卡下, 定义光路径参数, 如检测目标、激光阻挡过滤器、光束分配器、照相机和激光器。 注: GFP 通道用于本实验 (激发波长: 488 nm; 发射过滤器: BP 505 至 545 nm, 分束: SPS LP 560)。</li>
		<li>选中 "透视扫描" 复选框以减少阴影。</li>
		<li>定义采集设置: 位深度, 16 位;变焦, 0.36-0, 7 x;单侧照明 (左/右) 或双侧照明。</li>
		<li>单击连续并设置激光强度、曝光时间、激光功率和光片位置以获取更清晰的图像。 注: 激光功率保持尽可能低, 以最小化光损伤。</li>
		<li>按停止结束图像获取。</li>
	</ol>
</li>
	<li>
多维获取
	<ol>
<li>通过移动第一个和最后一个图像的 z 位置来定义 z 堆栈。单击最佳设置切片编号。</li>
		<li>单击开始实验获取选定的 z 堆栈。</li>
		<li>完成后, 将图像保存为. czi 格式。</li>
	</ol>
</li>
	<li>
图像处理 (可选)
	<ol>
<li>如果应用了双侧光照, 则在Lightsheet 处理通道下进行双侧融合。如果获取多视图来组合多个角度的图像, 则需要Multiview 处理。</li>
		<li>使用最大强度投影通道中沿投影轴的最高强度像素的数据创建2D 图像。</li>
		<li>在复制通道下, 单击子集从原始集选择图像子集。</li>
	</ol>
</li>
</ol>4. 轴突树枝状的定量 (每个人神经30分钟)
<ol><li>在成像分析软件中打开图像文件 (默认情况下, 包含 XYZ 数据的图像将以超越模式打开, 并作为3维渲染视图)。</li>
	<li>使用显示调整窗口调整图像颜色、亮度和对比度 (编辑 |显示调整) 以根据局部强度对比度检测花丝。</li>
	<li>单击添加新细丝图标, 然后在下拉菜单中选择Autopath (无循环)算法。</li>
	<li>选择感兴趣的区域 (在这种情况下, 细分轴的兴趣)。完成后, 单击下一步。</li>
	<li>通过指定最大和最薄直径测量来定义起始和种子点, 可以使用切片模式对其进行测量。</li>
	<li>在感兴趣区域的边缘分配一个起始点。要实现手动添加或删除起始点, 请首先更改指针模式 (导航 |选择), 然后Shift + 右键单击在感兴趣的点。</li>
	<li>为种子点选择手动阈值, 以确保标记了所有可见的树枝状。更改指针模式 (导航 |选择), 然后Shift + 左键单击在感兴趣的点, 以手动添加或删除种子点。 注意: 手动删除周围神经的背景噪声和信号是很重要的。</li>
	<li>选中在起始点周围移除种子点复选框。</li>
	<li>检查删除断开连接的段以允许排除距离太远且可能表示背景噪音的点。指示下一步骤中的最大间隙长度, 以定义排除的上限。</li>
	<li>调整背景减法的阈值, 使用高斯滤波器估计每个体素的背景强度。</li>
	<li>使用近似截面面积算法设置枝晶直径的自动阈值。</li>
	<li>跳过脊柱计算的步骤。</li>
	<li>完成该过程并选择所需的样式和颜色。</li>
	<li>取消选中属性中的卷框以仅查看重建的轴突。</li>
	<li>在统计选项卡下, 选择详细。使用灯丝号。枝晶末端点量化电机神经终端作为电机轴突树枝状的指示器。 注意: 如果需要, 可以添加统计注释。</li>
	<li>将重建后轴突的图像导出为. tif 文件。</li>
</ol>

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作者没有什么可透露的。

在某些情况下, 议定书中的若干步骤可能会受到变化。例如, 固定时间取决于胚胎的年龄, 从2小时到1天或更多的时候使用新鲜的多聚甲醛。由于固定是在整个染色之前进行的, 对于蛋白质交联敏感的抗体, 甲醇可以用作替代的固液剂。对于染色时的高信噪比, 必须优化洗涤剂浓度 (0.1-0.5%)。抗体孵化前后的额外洗涤步骤也可以增加信噪比。此外, 组织清除步骤对于确保在整个深轴突投影中的光路畅通?...

脊髓的 MNs 是中枢神经系统的一部分, 但支配周围的肌肉来控制运动。在发育中的脊髓中, 根据脊索和相邻胚胎背部发出的信号建立锰祖细胞 (pMNs)。所有分化后有丝分裂后的 MNs, 然后产生从 pMNs, 最终产生一系列锰亚型沿 rostrocaudal 轴的脊髓1,2。脊髓的地形和解剖良好组织。它们的形态学排列与各自目标在外围3中的位置相关。在达到他们的肌肉目标, 轴突接收细胞和外源性神经营养因子, 促使他们扩大和分支进一步进入肌肉。神经支配和分支缺陷可能导致无法形成肌电结 (NMJ)。例如, 神经胶质源性神经营养因子 (GDNF) 诱发的 Pea3 是必不可少的轴突树枝状到皮肤阔肌 (CM) 和后背筋 (LD) 肌肉 4, 5.此外,进餐挖空小鼠胚胎显示膈神经有缺陷的树枝状在隔膜, 导致呼吸衰竭和死亡后立即出生 6, 7.因此, 这最后一步的锰成熟 (即, 轴突投射和分支) 是至关重要的, 以确保神经元之间的沟通和目标细胞。
为了查看树枝状模式, 研究人员通常进行共焦成像或双光子荧光显微镜的切片或全挂载样本 8, 9, 10.这两种显微技术都能产生可接受的分辨率和深度穿透力。双光子荧光光镜涉及显影的激发, 同时吸收两个低能光子11。由于双光子激励使用近红外辐射, 减少的激发频率有助于减少散射和更好的组织穿透多达1毫米的组织, 从而使成像更深入。共焦显微镜通过过滤出焦点信号并在焦点平面12中收集光来消除。通过这种方法, 可以将来自不同焦平面的样本图像组合起来, 通过 Z 堆栈函数生成三维 (3D) 图像。然而, 由于大部分光线被堵塞, 而且高数值孔径掩盖了景深, 信号强度降低。更重要的是, 这两种技术都有助于严重的光损伤和毒性, 因为整个标本接受照明, 即使只有一架飞机是在给定的时间成像。
为了规避这些缺点, LSFM 已成为一种受青睐的替代方案, 具有快速、高效、光毒性13、14等优点.此外, LSFM 还允许多视图成像。这种方法特别适合于可视化电机轴突及其分散终端, 因为它们分布在3D 空间。LSFM 优于其他两个选项, 因为示例安装在允许围绕垂直轴旋转和沿 x、y 和 z 轴移动的舞台上。这种设置不仅允许对样本进行最小的屏蔽, 而且还可以选择理想的光照路径、双光子和共焦显微镜的缺点, 这两种方法都需要在平面滑动上安装样品。因此, LSFM 是最合适的工具, 3D 成像的轴突树枝状和量化的运动神经终端的小鼠胚胎。

<table>
	<tbody>
		<tr>
			<td>Hb9::GFP</td>
			<td>The Jackson labortory</td>
			<td>005029</td>
			<td>Collect embryos of embryonic day 13.5 (E13.5)</td>
		</tr>
		<tr>
			<td>4% Paraformaldehyde (PFA)</td>
			<td></td>
			<td></td>
			<td>For 200ml: Add 20ml 10X PBS, 8g PFA in ddH2O. Adjust pH to 7.4 with NaOH (10N). Filter sterilize and store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>Phosphate buffer saline 10X (PBS 10X)</td>
			<td></td>
			<td></td>
			<td>For 1L: Add 80 g NaCl, 2 g KCl,14.4g Na2HPO4, 2.4 g KH2PO4 and top up with ddH2O. Autoclave and store at RT.</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma</td>
			<td>X100-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>ThermoFisher</td>
			<td>26140079</td>
			<td></td>
		</tr>
		<tr>
			<td>Sheep polyclonal anti-GFP</td>
			<td>AbD Serotec</td>
			<td>4745-1051</td>
			<td>1:1000</td>
		</tr>
		<tr>
			<td>Alexa Fluor 488 donkey anti-sheep</td>
			<td>Invitrogen</td>
			<td>A-11015</td>
			<td>1:1000</td>
		</tr>
		<tr>
			<td>RapiClear 1.47 clearing reagent</td>
			<td>SunJin Lab</td>
			<td>RC147001</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5ml micro tube</td>
			<td>Sarstedt</td>
			<td>72.690.001</td>
			<td></td>
		</tr>
		<tr>
			<td>24 wells plate</td>
			<td>ThermoFisher</td>
			<td>142475</td>
			<td></td>
		</tr>
		<tr>
			<td>5 SA Tweezer</td>
			<td>ideal-tek</td>
			<td>3480641</td>
			<td></td>
		</tr>
		<tr>
			<td>Iris Scissors striaght sharp/sharp</td>
			<td>Aesculap</td>
			<td>BC110R</td>
			<td></td>
		</tr>
		<tr>
			<td>Microsurgery Scalpels, single use</td>
			<td>Aesculap</td>
			<td>BA365</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting microscope</td>
			<td>Nikon</td>
			<td>SMZ800</td>
			<td></td>
		</tr>
		<tr>
			<td>Shaker</td>
			<td>TKS</td>
			<td>RS-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Lightsheet Z.1 microscope</td>
			<td>Carl Zeiss Microscopy</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Imaris 8.4.0 image analysis software</td>
			<td>Bitplane, Zurich, Switzerland</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>B6.Cg-Tg(Hlxb9-GFP)1Tmj/J (Hb9::GFP mice)</td>
			<td>The Jackson Laboratory</td>
			<td>005029</td>
			<td></td>
		</tr>
	</tbody>
</table>

visualization of motor axon navigation and quantification of axon arborization in mouse embryos using light sheet fluorescence microscopy

脊髓运动神经元 (MNs) 扩展其轴突, 以与其支配目标进行沟通, 从而控制脊椎动物的运动和复杂任务。因此, 在发育和变性过程中, 揭示运动神经轴突如何定位、arborize 和支配其周围肌肉靶点的分子机制至关重要。尽管转基因的Hb9::GFP鼠标线长期用于可视化胚胎发育过程中的马达轴突轨迹, 但由于模式复杂, 对轴突终端树枝状的详细描述仍然不完整,目前光学显微镜的局限性。在这里, 我们描述了一个改进的协议, 结合光片荧光显微镜 (LSFM) 和稳健的图像分析, 定性和定量可视化发展电机轴突。该系统可以很容易地用于交叉遗传突变体或锰疾病模型与Hb9::GFP线, 揭示了新的分子机制, 导致缺陷的电机轴突导航和树枝状。

LSFM 提供详细的3D 可视化的锰弹道和轴突树枝状在小鼠胚胎。在明亮的领域, 在被浸泡在商业清除试剂之后, 组织显得完全透明。无收缩或肿胀的样本被发现后, 一个星期的存储在清除试剂成像前。在荧光通道下, 电机神经元被标记为 transgenically 表达的 GFP (影片 1)。在某些情况下, 轴突结构的细节被破坏。例如,图 2表示低质量映像。有几个?...

Watch this Scientific Journal Video about Visualization of Motor Axon Navigation and Quantification of Axon Arborization In Mouse Embryos Using Light Sheet Fluorescence Microscopy at JoVE.com

Visualization of Motor Axon Navigation and Quantification of Axon Arborization In Mouse Embryos Using Light Sheet Fluorescence Microscopy

在这里, 我们描述了一个协议, 以可视化的运动神经元投射和轴突树枝状在转基因 Hb9::GFP 小鼠胚胎. 在对运动神经元进行染色后, 我们用光片荧光显微镜对图像胚胎进行了定量分析。本协议适用于中枢神经系统的其它神经元导航过程。

用光片荧光显微镜观察运动轴突导航和小鼠胚轴突树枝状的定量化

Spinal motor neurons (MNs) extend their axons to communicate with their innervating targets, thereby controlling movement and complex tasks in ...

visualization-motor-axon-navigation-quantification-axon-arborization

Research

JoVE Journal

Neuroscience

7.6K 次观看.  National Defense Medical Center. 在这里, 我们描述了一个协议, 以可视化的运动神经元投射和轴突树枝状在转基因 Hb9::GFP 小鼠胚胎. 在对运动神经元进行染色后, 我们用光片荧光显微镜对图像胚胎进行了定量分析。本协议适用于中枢神经系统的其它神经元导航过程。

视频: Visualization of Motor Axon Navigation and Quantification of Axon Arborization In Mouse Embryos Using Light Sheet Fluorescence Microscopy

Study Glial Cell Heterogeneity Influence on Axon Growth Using a New Coculture Method

In the central nervous system of all mammals, severed axons after injury are unable to regenerate to their original targets and functional recovery is very poor 1. The failure of axon regeneration is a combined result of several factors including the hostile glial cell environment, inhibitory myelin related molecules and decreased intrinsic neuron regenerative capacity 2. Astrocytes are the most predominant glial cell type in central nervous system and play important role in axon functions under physiology and pathology conditions 3. Contrast to the homologous oligodendrocytes, astrocytes are a heterogeneous cell population composed by different astrocyte subpopulations with diverse morphologies and gene expression 4. The functional significance of this heterogeneity, such as their influences on axon growth, is largely unknown.
To study the glial cell, especially the function of astrocyte heterogeneity in neuron behavior, we established a new method by co-culturing high purified dorsal root ganglia neurons with glial cells obtained from the rat cortex. By this technique, we were able to directly compare neuron adhesion and axon growth on different astrocytes subpopulations under the same condition.
In this report, we give the detailed protocol of this method for astrocytes isolation and culture, dorsal root ganglia neurons isolation and purification, and the co-culture of DRG neurons with astrocytes. This method could also be extended to other brain regions to study cellular or regional specific interaction between neurons and glial cells.

In this protocol, we described a new method to study the influence of glial cell heterogeneity on axon growth with an in vitro co-culture system. Rat cortical glial cells were cultured to confluence and cocultured with highly purified rat dorsal root ganglia neurons. Different glial cell influence on neurons adhesion and axon growth was compared directly in the same culture. This method provides a new way to directly study the glial cell heterogeneity influence on neuron adhesion and axon growth.

研究胶质细胞轴突的生长异质性的影响，使用一个新的共培养法

In the central nervous system of all mammals, severed axons after injury are unable to regenerate to their original targets and functional recovery is ...

科研

神经科学

Micron-scale Resolution Optical Tomography of Entire Mouse Brains with Confocal Light Sheet Microscopy

Understanding the architecture of mammalian brain at single-cell resolution is one of the key issues of neuroscience. However, mapping neuronal soma and projections throughout the whole brain is still challenging for imaging and data management technologies. Indeed, macroscopic volumes need to be reconstructed with high resolution and contrast in a reasonable time, producing datasets in the TeraByte range. We recently demonstrated an optical method (confocal light sheet microscopy, CLSM) capable of obtaining micron-scale reconstruction of entire mouse brains labeled with enhanced green fluorescent protein (EGFP). Combining light sheet illumination and confocal detection, CLSM allows deep imaging inside macroscopic cleared specimens with high contrast and speed. Here we describe the complete experimental pipeline to obtain comprehensive and human-readable images of entire mouse brains labeled with fluorescent proteins. The clearing and the mounting procedures are described, together with the steps to perform an optical tomography on its whole volume by acquiring many parallel adjacent stacks. We showed the usage of open-source custom-made software tools enabling stitching of the multiple stacks and multi-resolution data navigation. Finally, we illustrated some example of brain maps: the cerebellum from an L7-GFP transgenic mouse, in which all Purkinje cells are selectively labeled, and the whole brain from a thy1-GFP-M mouse, characterized by a random sparse neuronal labeling.

In this article we describe the full experimental procedure to reconstruct, with high resolution, the fine brain anatomy of fluorescently labeled mouse brains. The described protocol includes sample preparation and clearing, specimen mounting for imaging, data post-processing and multi-scale visualization.

整个老鼠大脑与光共聚焦显微镜板微米级分辨率光学层析成像

Understanding the architecture of mammalian  brain at single-cell resolution is one of the key issues of neuroscience.  However, mapping neuronal soma and ...

Whole-mount Imaging of Mouse Embryo Sensory Axon Projections

The visualization of full-length neuronal projections in embryos is essential to gain an understanding of how mammalian neuronal networks develop. Here we describe a method to label in situ a subset of dorsal root ganglion (DRG) axon projections to assess their phenotypic characteristics using several genetically manipulated mouse lines. The TrkA-positive neurons are nociceptor neurons, dedicated to the transmission of pain signals. We utilize a TrkAtaulacZ mouse line to label the trajectories of all TrkA-positive peripheral axons in the intact mouse embryo. We further breed the TrkAtaulacZ line onto a Bax null background, which essentially abolishes neuronal apoptosis, in order to assess growth-related questions independently of possible effects of genetic manipulations on neuronal survival. Subsequently, genetically modified mice of interest are bred with the TrkAtaulacZ/Bax null line and are then ready for study using the techniques described herein. This presentation includes detailed information on mouse breeding plans, genotyping at the time of dissection, tissue preparation, staining and clearing to allow for visualization of full-length axonal trajectories in whole-mount preparation.

We present here an optimized protocol to genotype, stain and prepare fetal mice for the imaging of peripheral nociceptor axon projections in the whole animal, as an effective method to assess sensory axon growth phenotypes in developing genetically engineered mice.

小鼠胚胎感觉轴突预测整个安装成像

The visualization of full-length neuronal projections in embryos is essential to gain an understanding of how mammalian neuronal networks develop. Here we ...

The Neuromuscular Junction: Measuring Synapse Size, Fragmentation and Changes in Synaptic Protein Density Using Confocal Fluorescence Microscopy

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. Structural changes at the NMJ can result in neurotransmission failure, resulting in weakness, atrophy and even death of the muscle fiber. Many studies have investigated how genetic modifications or disease can alter the structure of the mouse NMJ. Unfortunately, it can be difficult to directly compare findings from these studies because they often employed different parameters and analytical methods. Three protocols are described here. The first uses maximum intensity projection confocal images to measure the area of acetylcholine receptor (AChR)-rich postsynaptic membrane domains at the endplate and the area of synaptic vesicle staining in the overlying presynaptic nerve terminal. The second protocol compares the relative intensities of immunostaining for synaptic proteins in the postsynaptic membrane. The third protocol uses Fluorescence Resonance Energy Transfer (FRET) to detect changes in the packing of postsynaptic AChRs at the endplate. The protocols have been developed and refined over a series of studies. Factors that influence the quality and consistency of results are discussed and normative data are provided for NMJs in healthy young adult mice.

The neuromuscular junction (NMJ) is altered in a variety of conditions that can sometimes culminate in synaptic failure. This report describes fluorescence microscope-based methods to quantify such structural changes.

神经肌肉接头处:测量突触大小，碎片和改变突触蛋白密度利用共聚焦荧光显微镜

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. ...

Imaging Ca2+ Dynamics in Cone Photoreceptor Axon Terminals of the Mouse Retina

Retinal cone photoreceptors (cones) serve daylight vision and are the basis of color discrimination. They are subject to degeneration, often leading to blindness in many retinal diseases. Calcium (Ca2+), a key second messenger in photoreceptor signaling and metabolism, has been proposed to be indirectly linked with photoreceptor degeneration in various animal models. Systematically studying these aspects of cone physiology and pathophysiology has been hampered by the difficulties of electrically recording from these small cells, in particular in the mouse where the retina is dominated by rod photoreceptors. To circumvent this issue, we established a two-photon Ca2+ imaging protocol using a transgenic mouse line that expresses the genetically encoded Ca2+ biosensor TN-XL exclusively in cones and can be crossbred with mouse models for photoreceptor degeneration. The protocol described here involves preparing vertical sections (&#8220;slices&#8221;) of retinas from mice and optical imaging of light stimulus-evoked changes in cone Ca2+ level. The protocol also allows &#8220;in-slice measurement&#8221; of absolute Ca2+ concentrations; as the recordings can be followed by calibration. This protocol enables studies into functional cone properties and is expected to contribute to the understanding of cone Ca2+ signaling as well as the potential involvement of Ca2+ in photoreceptor death and retinal degeneration.

Imaging Ca2+ Dynamics in Cone Photoreceptor Axon Terminals of the Mouse Retina

We describe a protocol to monitor Ca2+ dynamics in the axon terminals of cone photoreceptors using an ex-vivo&#160;slice preparation of the mouse retina. This protocol allows comprehensive studies of cone Ca2+ signaling in an important mammalian model system, the mouse.

成像钙<sup&gt; 2+</sup&gt;在小鼠视网膜锥光感受器轴突终末动态

Retinal cone photoreceptors (cones) serve daylight vision and are the basis of color discrimination. They are subject to degeneration, often leading to ...

Utilizing Combined Methodologies to Define the Role of Plasma Membrane Delivery During Axon Branching and Neuronal Morphogenesis

During neural development, growing axons extend to multiple synaptic partners by elaborating axonal branches. Axon branching is promoted by extracellular guidance cues like netrin-1 and results in dramatic increases to the surface area of the axonal plasma membrane. Netrin-1-dependent axon branching likely involves temporal and spatial control of plasma membrane expansion, the components of which are supplied through exocytic vesicle fusion. These fusion events are preceded by formation of SNARE complexes, comprising a v-SNARE, such as VAMP2 (vesicle-associated membrane protein 2), and plasma membrane t-SNAREs, syntaxin-1 and SNAP25 (synaptosomal-associated protein 25). Detailed herein isa multi-pronged approach used to examine the role of SNARE mediated exocytosis in axon branching. The strength of the combined approach is data acquisition at a range of spatial and temporal resolutions, spanning from the dynamics of single vesicle fusion events in individual neurons to SNARE complex formation and axon branching in populations of cultured neurons. This protocol takes advantage of established biochemical approaches to assay levels of endogenous SNARE complexes and Total Internal Reflection Fluorescence (TIRF) microscopy of cortical neurons expressing VAMP2 tagged with a pH-sensitive GFP (VAMP2-pHlourin) to identify netrin-1 dependent changes in exocytic activity in individual neurons. To elucidate the timing of netrin-1-dependent branching, time-lapse differential interference contrast (DIC) microscopy of single neurons over the order of hours is utilized. Fixed cell immunofluorescence paired with botulinum neurotoxins that cleave SNARE machinery and block exocytosis demonstrates that netrin-1 dependent axon branching requires SNARE-mediated exocytic activity.

Light microscopy techniques coupled with biochemical assays elucidate the involvement of SNARE-mediated exocytosis in netrin-dependent axon branching. This combination of techniques permits identification of molecular mechanisms controlling axon branching and cell shape change.

采用组合运用各种方法，定义质膜交付在轴突分支和神经元形态发生中的作用

During neural development, growing axons extend to multiple synaptic partners by elaborating axonal branches. Axon branching is promoted by extracellular ...

Quadruple Immunostaining of the Olfactory Bulb for Visualization of Olfactory Sensory Axon Molecular Identity Codes

The mouse olfactory system is often used to study mechanisms of neural circuit formation&#12288;because of its simple anatomical structure. An Olfactory Sensory Neuron (OSN) is a bipolar cell with a single dendrite and a single unbranched axon. An OSN expresses only one Olfactory Receptor (OR) gene, OSNs expressing a given type of OR converge their axons to a few sets of invariant glomeruli in the Olfactory Bulb (OB). A remarkable feature of OSN projection is that the expressed ORs play instructive roles in axonal projection. ORs regulate the expression of multiple axon-sorting molecules and generate the combinatorial molecular code of axon-sorting molecules at the OSN axon termini. Thus, to understand the molecular mechanisms of OR-specific axon guidance mechanisms, it is vital to characterize their expression profiles at the OSN axon termini within the same glomerulus. The aim of this article was to introduce methods for collecting as many glomeruli as possible on a single OB section and for performing immunostaining using multiple antibodies. This would allow the comparison and analysis of the expression patterns of axon-sorting molecules without staining variation between OB sections.

Olfactory sensory neurons express a wide variety of axon-sorting molecules to establish proper neural circuitry. This protocol describes an immunohistochemical staining method to visualize combinatorial expressions of axon-sorting molecules at the axon termini of olfactory sensory neurons.

嗅球的四次免疫染色用于嗅觉感觉轴突分子识别码的可视化

The mouse olfactory system is often used to study mechanisms of neural circuit formation&#12288;because of its simple anatomical structure. An Olfactory ...

Visualization of Thalamocortical Axon Branching and Synapse Formation in Organotypic Cocultures

Axon branching and synapse formation are crucial processes for establishing precise neuronal circuits. During development, sensory thalamocortical (TC) axons form branches and synapses in specific layers of the cerebral cortex. Despite the obvious spatial correlation between axon branching and synapse formation, the causal relationship between them is poorly understood. To address this issue, we recently developed a method for simultaneous imaging of branching and synapse formation of individual TC axons in organotypic cocultures.
This protocol describes a method which consists of a combination of an organotypic coculture and electroporation. Organotypic cocultures of the thalamus and cerebral cortex facilitate gene manipulation and observation of axonal processes, preserving characteristic structures such as laminar configuration. Two distinct plasmids encoding DsRed and EGFP-tagged synaptophysin (SYP-EGFP) were co-transfected into a small number of thalamic neurons by an electroporation technique. This method allowed us to visualize individual axonal morphologies of TC neurons and their presynaptic sites simultaneously. The method also enabled long-term observation which revealed the causal relationship between axon branching and synapse formation.

This protocol describes a method for simultaneous imaging of thalamocortical axon branching and synapse formation in organotypic cocultures of the thalamus and cerebral cortex. Individual thalamocortical axons and their presynaptic terminals are visualized by a single cell electroporation technique with DsRed and GFP-tagged synaptophysin.

脊髓 Cocultures 丘脑-皮质轴突分支和突触形成的可视化研究

Axon branching and synapse formation are crucial processes for establishing precise neuronal circuits. During development, sensory thalamocortical (TC) ...

Investigating Mammalian Axon Regeneration: In Vivo Electroporation of Adult Mouse Dorsal Root Ganglion

Electroporation is an essential non-viral gene transfection approach to introduce DNA plasmids or small RNA molecules into cells. A sensory neuron in the dorsal root ganglion (DRGs) extends a single axon with two branches. One branch goes to the peripheral nerve (peripheral branch), and the other branch enters the spinal cord through the dorsal root (central branch). After the neural injury, the peripheral branch regenerates robustly whereas the central branch does not regenerate. Due to the high regenerative capacity, sensory axon regeneration has been widely used as a model system to study mammalian axon regeneration in both the peripheral nervous system (PNS) and the central nervous system (CNS). Here, we describe a previously established approach protocol to manipulate gene expression in mature sensory neurons in vivo via electroporation. Based on transfection with plasmids or small RNA oligos (siRNAs or microRNAs), the approach allows for both loss- and gain-of-function experiments to study the roles of genes-of-interests or microRNAs in regulation of axon regeneration in vivo. In addition, the manipulation of gene expression in vivo can be controlled both spatially and temporally within a relatively short time course. This model system provides a unique tool to investigate the molecular mechanisms by which mammalian axon regeneration is regulated in vivo.

Investigating Mammalian Axon Regeneration: In Vivo Electroporation of Adult Mouse Dorsal Root Ganglion

Electroporation is an effective approach to deliver genes of interests into cells. By applying this approach in vivo on the neurons of adult mouse dorsal root ganglion (DRG), we describe a model to study axon regeneration in vivo.

哺乳动物轴突再生: 成年小鼠背根神经节体内电穿孔的研究

Electroporation is an essential non-viral gene transfection approach to introduce DNA plasmids or small RNA molecules into cells. A sensory neuron in the ...

Morphological and Functional Evaluation of Axons and their Synapses during Axon Death in Drosophila melanogaster

Axon degeneration is a shared feature in neurodegenerative disease and when nervous systems are challenged by mechanical or chemical forces. However, our understanding of the molecular mechanisms underlying axon degeneration remains limited. Injury-induced axon degeneration serves as a simple model to study how severed axons execute their own disassembly (axon death). Over recent years, an evolutionarily conserved axon death signaling cascade has been identified from flies to mammals, which is required for the separated axon to degenerate after injury. Conversely, attenuated axon death signaling results in morphological and functional preservation of severed axons and their synapses. Here, we present three simple and recently developed protocols that allow for the observation of axonal morphology, or axonal and synaptic function of severed axons that have been cut-off from the neuronal cell body, in the fruit fly Drosophila. Morphology can be observed in the wing, where a partial injury results in axon death side-by-side of uninjured control axons within the same nerve bundle. Alternatively, axonal morphology can also be observed in the brain, where the whole nerve bundle undergoes axon death triggered by antennal ablation. Functional preservation of severed axons and their synapses can be assessed by a simple optogenetic approach coupled with a post-synaptic grooming behavior. We present examples using a highwire loss-of-function mutation and by over-expressing dnmnat, both capable of delaying axon death for weeks to months. Importantly, these protocols can be used beyond injury; they facilitate the characterization of neuronal maintenance factors, axonal transport, and axonal mitochondria.

Morphological and Functional Evaluation of Axons and their Synapses during Axon Death in Drosophila melanogaster

Here, we provide protocols to perform three simple injury-induced axon degeneration (axon death) assays in Drosophila melanogaster to evaluate the morphological and functional preservation of severed axons and their synapses.

在果蝇黑色无gaster的Axon死亡期间，对Axon及其突触的形态和功能评估

Axon degeneration is a shared feature in neurodegenerative disease and when nervous systems are challenged by mechanical or chemical forces. However, our ...