The authors would like to thank Stefano Di Talia, Alberto Puliafito, Venkatraman Seshan and Panagiotis Xenopoulos, for input on data handling, analysis and representation, Berenika Plusa for assistance in the design of the immunofluorescence protocol and antibody testing and members of the Hadjantonakis lab for comments on the manuscript and on the development of this protocol. Work in our lab is supported by the National Institutes of Health R01-HD052115 and R01-DK084391, and by NYSTEM N13G-236.

<ol>
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The authors declare no conflicts of interest.

本协议描述在植入前阶段的小鼠胚胎进行全挂载免疫荧光定量分析的方法。一个强大的免疫协议22后跟高分辨率，整个安装使用定制的软件4聚焦成像和图像分割。而免疫协议的选择不是关键，我们发现这里呈现22是快速，可靠，并为许多我们已经测试了抗体的提供可靠的信号之一。其它协议可遵循，条件是它们的应用是在整个等效实验一致。虽然许多因素会影响每个单独?...

鼠标植入前胚胎是一个范例来研究细胞命运说明书和哺乳动物从头上皮的研究出现和体内的多能性的维持，以及一个模型。哺乳动物发育的胚胎植入前阶段致力于建立三种细胞谱系构成囊胚，即多能性外胚层 ​​- 这引起了大多数体细胞组织和生殖细胞 - 和两个胚谱系，滋养外胚层（TE）和原始内胚层（PRE）（图1A）1,2。这个协议描述的步骤（1）收获并修复植入前阶段的小鼠胚胎，（2）执行免疫荧光标记的感兴趣的蛋白质，（3）进行整个安装使用共聚焦显微镜用z-切片功能和成像（4）执行共聚焦图像和随后的定量图像分析的核分割。这条管道可以牛逼他无偏蛋白水平的测量小区标识的分配来表征原位细胞亚群。这种协议可以在少至3来进行-第4天为一个单一垫料（通常最多10个小鼠胚胎），从胚胎收集到数据分析（图1B）。几个窝的同时分析会增加成像和数据分析时间负担，从而延长了协议的总长度。 植入前阶段的小鼠胚胎是一个听话的实验系统，其中，由于其体积小，定型形态3， 在单细胞分辨率的细胞过程TOTO成像非常适合。开展胚胎的统计相关数字的公正，制度层面的分析，自动的，定量分析的管道是可取的。然而，由于内细胞团的囊胚（ICM）的高核密度（ <st荣&gt;图1A，2D），传统的图像分割平台不能提供足够的精度，以建立一个自动化或半自动化的工作流程。在另一方面，手动分割准确，还不允许细胞和胚胎的大型队列的处理，也不是适合重复性的，公正的决心小区身份的 - 学习发育阶段时，这是特别重要的地方标记模式表达还没有完全解决的（例如，不表现出跨越人口二进制分布）。我们最近开发并验证了小鼠植入前阶段的胚胎，并为实现高精度的小鼠胚胎干细胞（ES细胞）的量身定制的图像分割方法，同时需要很少的用户输入4-8。 这里提出的分析管道围绕基于MATLAB的图像分割工具，模块化交互式核分割（分）4。敏思performs无监督核分割上共焦的Z堆叠的大批量的用户已经建立图片属性的最少数量后，利用图形用户界面（GUI）（表1）4。这条管道已被证明有效的高通量数据对野生型蛋白表达和细胞定位的产生，处理实验和转基因胚胎和胚胎干细胞5-7。在本协议中，我们描述的MIN到植入前阶段的胚胎图像分割中的应用。有关胚胎干细胞的敏思性能的例子请参考4,7。自动核分割步骤显著降低了小区识别处理时的负担，而空间和荧光强度测量允许小区身份的无偏测定和基因表达结构域和细胞位置的三维地图的产生在胚胎（图1C </strong&gt;）。此外，该工作流程的可扩展性使其适用于个别窝的分析，通过实验处理的胚胎，或不同的遗传背景5,6胚胎的大同伙。敏思是免费提供的http://katlab-tools.org（软件需要MATLAB许可证）。 没有开发迄今方法允许对小鼠植入前胚胎蛋白质表达和细胞定位这样深入的数据的生成。所有的尝试到目前为止在量化这些类型的数据已被限制为手动判定和对于不同人群的细胞数的定量在胚胎（或者完全手动，或软件辅助）9-19。 （结合敏思软件）这种方法已经被量身定做和鼠标胚胎植入前胚胎干细胞和测试;不过其上具有高的核密度的其它系统的性能，虽然尚未检验，预计是等价的。

<table><tbody><tr><td>&lt;strong&gt;Embryo collection&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Blunt probe for plug checking</td><td>Roboz</td><td>RS-9580</td><td></td></tr><tr><td>Forceps</td><td>Roboz</td><td>RS-4978</td><td></td></tr><tr><td>Surgery scissors</td><td>Roboz</td><td>RS-5910</td><td></td></tr><tr><td>Glass Pasteur pipettes</td><td>Fisher</td><td>13-678-20C</td><td></td></tr><tr><td>Pre-assembled aspirator tube &amp;amp; mouthpiece</td><td>Sigma</td><td>A5177</td><td></td></tr><tr><td>Longer rubber tubing</td><td>Fisher</td><td>14-178-2AA&amp;nbsp;&amp;nbsp;&amp;nbsp;</td><td></td></tr><tr><td>M2</td><td>Millipore</td><td>MR-015-D</td><td></td></tr><tr><td>FHM</td><td>Millipore</td><td>MR-024-D</td><td></td></tr><tr><td>Acid Tyrode&#039;s solution</td><td>Millipore</td><td>MR-004-D</td><td></td></tr><tr><td>Penicillin/Streptomycin</td><td>Gibco</td><td>15140</td><td></td></tr><tr><td>Bovine Serum Albumin&amp;nbsp;</td><td>Sigma</td><td>A9647</td><td></td></tr><tr><td>4-well plates</td><td>Nunc/Thermo-Fisher</td><td>12-566-300&amp;nbsp;&amp;nbsp;&amp;nbsp;</td><td></td></tr><tr><td>&lt;strong&gt;Immunofluorescence&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>96-well U-bottom plates</td><td>Fisher</td><td>14-245-73</td><td></td></tr><tr><td>Triton X-100</td><td>Sigma</td><td>T8787</td><td></td></tr><tr><td>Glycine</td><td>Sigma</td><td>G7403</td><td></td></tr><tr><td>Horse serum</td><td>Sigma</td><td>H0146</td><td></td></tr><tr><td>&lt;strong&gt;Primary antibodies&lt;/strong&gt;</td><td></td><td></td><td>&lt;strong&gt;Concentration&lt;/strong&gt;</td></tr><tr><td>CDX2</td><td>Biogenex</td><td>AM392-5M</td><td>1:200</td></tr><tr><td>GATA6</td><td>R&amp;amp;D</td><td>AF1700</td><td>1:100</td></tr><tr><td>GATA4</td><td>Santa Cruz</td><td>sc-9053</td><td>1:100, 10 min fixation</td></tr><tr><td>GATA4</td><td>Santa Cruz</td><td>sc-1237</td><td>1:100, O/N fixation</td></tr><tr><td>SOX17</td><td>R&amp;amp;D</td><td>AF1924</td><td>1:100</td></tr><tr><td>Nanog</td><td>ReproCELL</td><td>RCAB0002P-F</td><td>1:500</td></tr><tr><td>OCT4</td><td>Santa Cruz</td><td>sc-5279</td><td>1:100, 10 min to O/N fixation</td></tr><tr><td>DAB2</td><td>BD</td><td>BD-610464</td><td>1:200</td></tr><tr><td>Secondary antibodies</td><td>Life Technologies</td><td>Various</td><td>1:500</td></tr><tr><td>Hoechst 33342</td><td>Life Technologies</td><td>H3570</td><td></td></tr><tr><td>&lt;strong&gt;Imaging&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>35 mm glass-bottom dishes</td><td>MatTek</td><td>P35G-1.5-14-C</td><td></td></tr><tr><td>&lt;strong&gt;Segmentation&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Computer running 64-bit Windows OS</td><td></td><td>n/a</td><td>Verify minimal system requirements at http://katlab-tools.org and in Lou et al., (2014) Stem Cell Reports</td></tr><tr><td>MATLAB (software)</td><td>Mathworks</td><td>n/a</td><td></td></tr><tr><td>MINS (software)</td><td>Free</td><td>n/a</td><td>http://katlab-tools.org</td></tr></tbody></table>

quantitative analysis of protein expression to study lineage specification in mouse preimplantation embryos

这个协议提供了一个方法来进行定量，原位单细胞蛋白表达的分析，以研究谱系规范 在小鼠植入前胚胎。描述所需胚胎收集，免疫荧光，在共聚焦显微镜成像，和图像分割和分析的过程。此方法允许在胚胎的所有单元中的多个核标志物的表达和空间（XYZ）的定量的坐标。这需要MINS，专门为着床前胚胎和胚胎干细胞（ESC）的菌落的共焦图像的分析开发出一种图像分割的软件工具的优点。 MINS执行通过X，Y和Z维度的无监督核分割，并以最小的用户输入的所有信道产生在三维空间上单元位置信息，以及核荧光水平。虽然该协议已经为图像的分析而优化植入前阶段的小鼠胚胎的，它可以容易地适应于呈现良好信噪比并且其中高核密度带来了障碍的图像分割（例如，胚胎干细胞中的表达分析的任何其他样品的分析（ESC ）菌落，分化培养中的细胞，其它物种或阶段等 ）的胚胎。

为了便于数据解释和介绍，应注意不要收集和操作过程中损坏的胚胎，使所有的细胞和它们的相对位置可分析图2A - D示出了在具有扩展腔的不同阶段的完整胚泡的例子。如果出现损坏，格外小心，应注意分析和解释结果时。 使用该协议生成的数据的质量和可靠性依赖于固定的质量和用于检测所关注的蛋白质的抗体...

Watch this Scientific Journal Video about Quantitative Analysis of Protein Expression to Study Lineage Specification in Mouse Preimplantation Embryos at JoVE.com

Quantitative Analysis of Protein Expression to Study Lineage Specification in Mouse Preimplantation Embryos

蛋白表达的定量分析来研究宗族规范小鼠植入前胚胎

该协议提出对蛋白质表达的原位分析进行定量，单细胞研究在小鼠植入前胚胎沿袭规范的方法。必要的囊胚的汇编程序，整个安装蛋白的免疫检测，在一个共焦显微镜，和核分割和图像分析的样品的成像进行描述。

This protocol presents a method to perform quantitative, single-cell in situ analyses of protein expression to study lineage specification in mouse ...

quantitative-analysis-protein-expression-to-study-lineage

Universidad de Cartagena UDEC

Research

JoVE Journal

Developmental Biology

10.8K 次观看.  Sloan Kettering Institute. 该协议提出对蛋白质表达的原位分析进行定量，单细胞研究在小鼠植入前胚胎沿袭规范的方法。必要的囊胚的汇编程序，整个安装蛋白的免疫检测，在一个共焦显微镜，和核分割和图像分析的样品的成像进行描述。 

视频: Quantitative Analysis of Protein Expression to Study Lineage Specification in Mouse Preimplantation Embryos

Loss- and Gain-of-function Approach to Investigate Early Cell Fate Determinants in Preimplantation Mouse Embryos

Gene silencing and overexpression techniques are instrumental for the identification of genes involved in embryonic development. Direct target gene modification in preimplantation embryos provides a means to study the underlying mechanisms of genes implicated in, for instance, cellular differentiation into the trophectoderm (TE) and the inner cell mass (ICM). Here, we describe a protocol that examines the role of neogenin as an authentic receptor for initial cell fate determination in preimplantation mouse embryos. First, we discuss the experimental manipulations that were used to produce gain and loss of neogenin function by microinjecting neogenin cDNA and shRNA; the effectiveness of this approach was confirmed by a strong correlation between the pair-wise expression levels of either red fluorescent protein (RFP) or green fluorescent protein (GFP) and the immunocytochemical quantification of neogenin expression. Secondly, overexpression of neogenin in preimplantation mouse embryos leads to normal ICM development while neogenin knockdown causes the ICM to develop abnormally, implying that neogenin could be a receptor that relays extracellular cues to drive blastomeres to early cell fates. Given the success of this detailed protocol in investigating the function of a novel embryonic developmental stage-specific receptor, we propose that it has the potential to aid in exploration and identification of other stage-specific genes during embryogenesis.

The goal of this protocol is to describe a loss- and gain-of function method that is applicable to identify neogenin as a stage-specific receptor that leads to trophectoderm and inner cell mass differentiation in preimplantation mouse embryos.

损失 - 和增益的功能角度进行调查研究早期细胞命运决定在植入前小鼠胚胎

 Gene silencing and overexpression techniques are instrumental for the identification of genes involved in embryonic development. Direct target gene ...

科研

发育生物学

Temporal Ordering of Dynamic Expression Data from Detailed Spatial Expression Maps

During somitogenesis, pairs of epithelial somites form in a progressive manner, budding off from the anterior end of the pre-somitic mesoderm (PSM) with a strict species-specific periodicity. The periodicity of the process is regulated by a molecular oscillator, known as the "segmentation clock," acting in the PSM cells. This clock drives the oscillatory patterns of gene expression across the PSM in a posterior-anterior direction. These so-called clock genes are key components of three signaling pathways: Wnt, Notch, and fibroblast growth factor (FGF). In addition, Notch signaling is essential for synchronizing intracellular oscillations in neighboring cells. We recently gained insight into how this may be mechanistically regulated. Upon ligand activation, the Notch receptor is cleaved, releasing the intracellular domain (NICD), which moves to the nucleus and regulates gene expression. NICD is highly labile, and its phosphorylation-dependent turnover acts to restrict Notch signaling. The profile of NICD production (and degradation) in the PSM is known to be oscillatory and to resemble that of a clock gene. We recently reported that both the Notch receptor and the Delta ligand, which mediate intercellular coupling, themselves exhibit dynamic expression at both the mRNA and protein levels. In this article, we describe the sensitive detection methods and detailed image analysis tools that we used, in combination with the computational modeling that we designed, to extract and overlay expression data from distinct points in the expression cycle. This allowed us to construct a spatio-temporal picture of the dynamic expression profile for the receptor, the ligand, and the Notch target clock genes throughout an oscillation cycle. Here, we describe the protocols used to generate and culture the PSM explants, as well as the procedure to stain for the mRNA or protein. We also explain how the confocal images were subsequently analyzed and temporally ordered computationally to generate ordered sequences of clock expression snapshots, hereafter defined as "kymographs," for the visualization of the spatiotemporal expression of Delta-like1 (Dll1) and Notch1 throughout the PSM.

The segmentation clock drives oscillatory gene expression across the pre-somitic mesoderm (PSM). Dynamic Notch activity is key to this process. We use imaging and computational analyses to extract temporal dynamics from spatial expression data to demonstrate that Delta ligand and Notch receptor expression oscillate in the vertebrate PSM.

从详细的空间表达图谱的动态表达数据的时间排序

During somitogenesis, pairs of epithelial somites form in a progressive manner, budding off from the anterior end of the pre-somitic mesoderm (PSM) with a ...

Robust Comparison of Protein Levels Across Tissues and Throughout Development Using Standardized Quantitative Western Blotting

Western blotting is a technique that is commonly used to detect and quantify protein expression. Over the years, this technique has led to many advances in both basic and clinical research. However, as with many similar experimental techniques, the outcome of Western blot analyses is easily influenced by choices made in the design and execution of the experiment. Specific housekeeping proteins have traditionally been used to normalize protein levels for quantification, however, these have a number of limitations and have therefore been increasingly criticized over the past few years. Here, we describe a detailed protocol that we have developed to allow us to undertake complex comparisons of protein expression variation across different tissues, mouse models (including disease models), and developmental timepoints. By using a fluorescent total protein stain and introducing the use of an internal loading standard, it is possible to overcome existing limitations in the number of samples that can be compared within experiments and systematically compare protein levels across a range of experimental conditions. This approach expands the use of traditional western blot techniques, thereby allowing researchers to better explore protein expression across different tissues and samples.

This method describes a robust and reproducible approach for the comparison of protein levels in different tissues and at different developmental timepoints using a standardized quantitative western blotting approach.

利用标准化定量西方印迹技术, 对跨组织和整个开发过程中的蛋白质水平进行可靠比较

Western blotting is a technique that is commonly used to detect and quantify protein expression. Over the years, this technique has led to many advances ...

生物化学

Quantitative Whole-mount Immunofluorescence Analysis of Cardiac Progenitor Populations in Mouse Embryos

The use of ever-advancing imaging techniques has contributed broadly to our increased understanding of embryonic development. Pre-implantation development and organogenesis are two areas of research that have benefitted greatly from these advances, due to the high quality of data that can be obtained directly from imaging pre-implantation embryos or ex vivo organs. While pre-implantation embryos have yielded data with especially high spatial resolution, later stages have been less amenable to three-dimensional reconstruction. Obtaining high-quality 3D or volumetric data for known embryonic structures in combination with fate mapping or genetic lineage tracing will allow for a more comprehensive analysis of the morphogenetic events taking place during embryogenesis.
This protocol describes a whole-mount immunofluorescence approach that allows for the labeling, visualization, and quantification of progenitor cell populations within the developing cardiac crescent, a key structure formed during heart development. The approach is designed in such a way that both cell- and tissue-level information can be obtained. Using confocal microscopy and image processing, this protocol allows for three-dimensional spatial reconstruction of the cardiac crescent, thereby providing the ability to analyze the localization and organization of specific progenitor populations during this critical phase of heart development. Importantly, the use of reference antibodies allows for successive masking of the cardiac crescent and subsequent quantitative measurements of areas within the crescent. This protocol will not only enable a detailed examination of early heart development, but with adaptations should be applicable to most organ systems in the gastrula to early somite stage mouse embryo.

Here, we describe a protocol for whole mount immunofluorescence and image-based quantitative volumetric analysis of early stage mouse embryos. We present this technique as a powerful approach to qualitatively and quantitatively assess cardiac structures during development, and propose that it may be widely adaptable to other organ systems.

小鼠胚胎心肌内祖群的定量全贴免疫荧光分析

The use of ever-advancing imaging techniques has contributed broadly to our increased understanding of embryonic development. Pre-implantation development ...

Tracing Gene Expression Through Detection of &#946;-galactosidase Activity in Whole Mouse Embryos

The Escherichia coli LacZ gene, encoding &#946;-galactosidase, is largely used as a reporter for gene expression and as a tracer in cell lineage studies. The classical histochemical reaction is based on the hydrolysis of the substrate X-gal in combination with ferric and ferrous ions, which produces an insoluble blue precipitate that is easy to visualize. Therefore, &#946;-galactosidase activity serves as a marker for the expression pattern of the gene of interest as the development proceeds. Here we describe the standard protocol for the detection of &#946;-galactosidase activity in early whole mouse embryos and the subsequent method for paraffin sectioning and counterstaining. Additionally, a procedure for clarifying whole embryos is provided to better visualize X-gal staining in deeper regions of the embryo. Consistent results are obtained by performing this procedure, although optimization of reaction conditions is needed to minimize background activity. Limitations in the assay should be also considered, particularly regarding the size of the embryo in whole mount staining. Our protocol provides a sensitive and a reliable method for &#946;-galactosidase detection during the mouse development that can be further applied to the cryostat sections as well as whole organs. Thus, the dynamic gene expression patterns throughout development can be easily analyzed by using this protocol in whole embryos, but also detailed expression at the cellular level can be assessed after paraffin sectioning.

Here we describe the standard protocol for the detection of &#946;-galactosidase activity in early whole mouse embryos and the method for paraffin sectioning and counterstaining. This is an easy and quick procedure to monitor gene expression during development that can also be applied to tissue sections, organs or cultured cells.

通过检测全小鼠胚胎β乳糖酶活性追踪基因表达

The Escherichia coli LacZ gene, encoding &#946;-galactosidase, is largely used as a reporter for gene expression and as a tracer in cell lineage studies. ...

A Semi-high-throughput Imaging Method and Data Visualization Toolkit to Analyze C. elegans Embryonic Development

C. elegans is the premier system for the systematic analysis of cell fate specification and morphogenetic events during embryonic development. One challenge is that embryogenesis dynamically unfolds over a period of about 13 h; this half day-long timescale has constrained the scope of experiments by limiting the number of embryos that can be imaged. Here, we describe a semi-high-throughput protocol that allows for the simultaneous 3D time-lapse imaging of development in 80&#8211;100 embryos at moderate time resolution, from up to 14 different conditions, in a single overnight run. The protocol is straightforward and can be implemented by any laboratory with access to a microscope with point visiting capacity. The utility of this protocol is demonstrated by using it to image two custom-built strains expressing fluorescent markers optimized to visualize key aspects of germ-layer specification and morphogenesis. To analyze the data, a custom program that crops individual embryos out of a broader field of view in all channels, z-steps, and timepoints and saves the sequences for each embryo into a separate tiff stack was built. The program, which includes a user-friendly graphical user interface (GUI), streamlines data processing by isolating, pre-processing, and uniformly orienting individual embryos in preparation for visualization or automated analysis. Also supplied is an ImageJ macro that compiles individual embryo data into a multi-panel file that displays maximum intensity fluorescence projection and brightfield images for each embryo at each time point. The protocols and tools described herein were validated by using them to characterize embryonic development following knock-down of 40 previously described developmental genes; this analysis visualized previously annotated developmental phenotypes and revealed new ones. In summary, this work details a semi-high-throughput imaging method coupled with a cropping program and ImageJ visualization tool that, when combined with strains expressing informative fluorescent markers, greatly accelerates experiments to analyze embryonic development.

A Semi-high-throughput Imaging Method and Data Visualization Toolkit to Analyze C. elegans Embryonic Development

This work describes a semi-high-throughput protocol that allows simultaneous 3D time-lapse imaging of embryogenesis in 80&#8211;100 C. elegans embryos in a single overnight run. Additionally, image processing and visualization tools are included to streamline data analysis. The combination of these methods with custom reporter strains enables detailed monitoring of embryogenesis.

半高通量成像方法和数据可视化工具包，用于分析C. elegans胚胎发育

C. elegans is the premier system for the systematic analysis of cell fate specification and morphogenetic events during embryonic development. One ...

Multiplexed Single Cell mRNA Sequencing Analysis of Mouse Embryonic Cells

Single cell mRNA sequencing has made significant progress in the last several years and has become an important tool in the field of developmental biology. It has been successfully used to identify rare cell populations, discover novel marker genes, and decode spatial and temporal developmental information. The single cell method has also evolved from the microfluidic based Fluidigm C1 technology to the droplet-based solutions in the last two to three years. Here we used the heart as an example to demonstrate how to profile the mouse embryonic tissue cells using the droplet based scRNA-Seq method. In addition, we have integrated two strategies into the workflow to profile multiple samples in a single experiment. Using one of the integrated methods, we have simultaneously profiled more than 9,000 cells from eight heart samples. These methods will be valuable to the developmental biology field by providing a cost-effective way to simultaneously profile single cells from different genetic backgrounds, developmental stages, or anatomical locations.

Here we presented a multiplexed single cell mRNA sequencing method to profile gene expression in mouse embryonic tissues. The droplet-based single cell mRNA sequencing (scRNA-Seq) method in combination with multiplexing strategies can profile single cells from multiple samples simultaneously, which significantly reduces reagent costs and minimizes experimental batch effects.

小鼠胚胎细胞的多路复用单细胞mRNA测序分析

Single cell mRNA sequencing has made significant progress in the last several years and has become an important tool in the field of developmental ...

Preparation of Small RNA Libraries for Sequencing from Early Mouse Embryos

MicroRNAs (miRNAs) are important for the complex regulation of cell fate decisions and developmental timing. In vivo studies of the contribution of miRNAs during early development are technically challenging due to the limiting cell number. Moreover, many approaches require a miRNA of interest to be defined in assays such as northern blotting, microarray, and qPCR. Therefore, the expression of many miRNAs and their isoforms have not been studied during early development. Here, we demonstrate a protocol for small RNA sequencing of sorted cells from early mouse embryos to enable relatively unbiased profiling of miRNAs in early populations of neural crest cells. We overcome the challenges of low cell input and size selection during library preparation using amplification and gel-based purification. We identify embryonic age as a variable accounting for variation between replicates and stage-matched mouse embryos must be used to accurately profile miRNAs in biological replicates. Our results suggest that this method can be broadly applied to profile the expression of miRNAs from other lineages of cells. In summary, this protocol can be used to study how miRNAs regulate developmental programs in different cell lineages of the early mouse embryo.

We describe a technique for profiling microRNAs in early mouse embryos. This protocol overcomes the challenge of low cell input and small RNA enrichment. This assay can be used to analyze changes in miRNA expression over time in different cell lineages of the early mouse embryo.

为早期小鼠胚胎测序准备小型RNA库

MicroRNAs (miRNAs) are important for the complex regulation of cell fate decisions and developmental timing. In vivo studies of the contribution of miRNAs ...

Cell-Lineage Guided Mass Spectrometry Proteomics in the Developing (Frog) Embryo

Characterization of molecular events as cells give rise to tissues and organs raises a potential to better understand normal development and design efficient remedies for diseases. Technologies enabling accurate identification and quantification of diverse types and large numbers of proteins would provide still missing information on molecular mechanisms orchestrating tissue and organism development in space and time. Here, we present a mass spectrometry-based protocol that enables the measurement of thousands of proteins in identified cell lineages in Xenopus laevis (frog) embryos. The approach builds on reproducible cell-fate maps and established methods to identify, fluorescently label, track, and sample cells and their progeny (clones) from this model of vertebrate development. After collecting cellular contents using microsampling or isolating cells by dissection or fluorescence-activated cell sorting, proteins are extracted and processed for bottom-up proteomic analysis. Liquid chromatography and capillary electrophoresis are used to provide scalable separation for protein detection and quantification with high-resolution mass spectrometry (HRMS). Representative examples are provided for the proteomic characterization of neural-tissue fated cells. Cell-lineage-guided HRMS proteomics is adaptable to different tissues and organisms. It is sufficiently sensitive, specific, and quantitative to peer into the spatio-temporal dynamics of the proteome during vertebrate development.

Cell-Lineage Guided Mass Spectrometry Proteomics in the Developing Frog Embryo

Here we describe a mass spectrometry-based proteomic characterization of cell lineages with known tissue fates in the vertebrate Xenopus laevis embryo.

发育（青蛙）胚胎中的细胞谱系引导质谱蛋白质组学

Characterization of molecular events as cells give rise to tissues and organs raises a potential to better understand normal development and design ...

化学

Chromatin Immunoprecipitation Assay for Tissue-specific Genes using Early-stage Mouse Embryos

Chromatin immunoprecipitation (ChIP) is a powerful tool to identify protein:chromatin interactions that occur in the context of living cells 1-3. This technique has been widely exploited in tissue culture cells, and to a lesser extent, in primary tissue. The application of ChIP to rodent embryonic tissue, especially at early times of development, is complicated by the limited amount of tissue and the heterogeneity of cell and tissue types in the embryo. Here we present a method to perform ChIP using a dissociated embryonic day 8.5 (E8.5) embryo. Sheared chromatin from a single E8.5 embryo can be divided into up to five aliquots, which allows the investigator sufficient material for controls and for investigation of specific protein:chromatin interactions.
We have utilized this technique to begin to document protein:chromatin interactions during the specification of tissue-specific gene expression programs. The heterogeneity of cell types in an embryo necessarily restricts the application of this technique because the result is the detection of protein:chromatin interactions without distinguishing whether the interactions occur in all, a subset of, or a single cell type(s). However, examination of tissue-specific genes during or following the onset of tissue-specific gene expression is feasible for two reasons. First, immunoprecipitation of tissue specific factors necessarily isolates chromatin from the cell type where the factor is expressed. Second, immunoprecipitation of coactivators and histones containing post-translational modifications that are associated with gene activation should only be found at genes and gene regulatory sequences in the cell type where the gene is being or has been activated. The technique should be applicable to the study of most tissue-specific gene activation events.
In the example described below, we utilized E8.5 and E9.5 mouse embryos to examine factor binding at a skeletal muscle specific gene promoter. Somites, which are the precursor tissues from which the skeletal muscles of the trunk and limbs will form, are present at E8.5-9.54,5. Myogenin is a regulatory factor required for skeletal muscle differentiation 6-9. The data demonstrate that myogenin is associated with its own promoter in E8.5 and E9.5 embryos. Because myogenin is only expressed in somites at this stage of development 6,10, the data indicate that myogenin interactions with its own promoter have already occurred in skeletal muscle precursor cells in E8.5 embryos.

We demonstrate a chromatin immunoprecipitation (ChIP) method to identify factor interactions at tissue-specific genes during or after the onset of tissue-specific gene expression in mouse embryonic tissue. This protocol should be widely applicable for the study of tissue-specific gene activation as it occurs during normal embryonic development.

使用早期的小鼠胚胎组织特异性基因的染色质免疫沉淀检测

Chromatin immunoprecipitation (ChIP) is a powerful tool to identify protein:chromatin interactions that occur in the context of living cells 1-3. This ...