We would like to thank Olivier Pourqui&#233; and Alexander Aulehla for the LuVeLu reporter strain, the SunJin laboratory for the RapiClear test sample, Hugo Pereira for the help using BigStitcher, Nuno Granjeiro for helping to set up the live imaging apparatus, the IGC animal facility and past and present members of the Mallo lab for useful comments and support during the course of this work.
We thank the technical support of IGC&#39;s Advanced Imaging Facility, which is supported by Portuguese funding ref# PPBI-POCI-01-0145-FEDER-022122 and ref# PTDC/BII-BTI/32375/2017, co-financed by Lisboa Regional Operational Programme (Lisboa 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER) and Funda&#231;&#227;o para a Ci&#234;ncia e a Tecnologia (FCT, Portugal). Work described in this manuscript was supported by grants LISBOA-01-0145-FEDER-030254 (FCT, Portugal) and SCML-MC-60-2014 (Santa Casa da Miseric&#243;rdia, Portugal) to M.M., the research infrastructure Congento, project LISBOA-01-0145-FEDER-022170, and the PhD fellowship PD/BD/128426/2017 to A.D.

The authors declare no conflicts of interest.

Axial elongation and segmentation are two of the most complex and dynamic processes occurring during vertebrate embryonic development. The use of 3D and 4D imaging with single-cell tracking has been applied, for some time, to study these processes in both zebrafish and chicken embryos, for which accessibility and culture conditions facilitate complex imaging19,44,45,46,<sup class="xr...

Vertebrate body axis formation is a highly complex and dynamic process occurring during embryonic development. At the end of gastrulation [in the mouse, around embryonic day (E) 8.0], a group of epiblast progenitor cells known as neuromesodermal progenitors (NMPs) become a key driver of axial extension in a head to tail sequence, generating the neural tube and paraxial mesodermal tissues during neck, trunk and tail formation1,2,3,4. Interestingly, the position that these NMPs occupy in the caudal epiblast seems to play a key role in the decision of differentiating into mesoderm or neuroectoderm5. Although we currently lack a precise molecular fingerprint for NMPs, these cells are generally thought to co-express T (Brachyury) and Sox25,6. The exact mechanisms regulating NMP fate decisions (i.e., whether they take neural or mesodermal routes) are only starting to be precisely defined. Tbx6 expression in the primitive streak region is an early marker of NMP fate decision, as this gene is involved in the induction and specification of mesoderm6,7. Interestingly, early mesoderm cells seem to express high levels of Epha18, and Wnt/&#946;-catenin signalling, as well as Msgn1 were also shown to play important roles in paraxial mesoderm differentiation and somite formation9,10. A complete spatial-temporal analysis of NMPs at a single-cell level will certainly be instrumental to fully understand the molecular mechanisms controlling mesoderm specification.
The formation of somites (vertebrae precursors) is a key feature of vertebrates. During axial elongation, the paraxial mesoderm becomes segmented in a series of bilateral repeating units known as somites. The number of somites and the time required for the formation of new segments varies among species11,12. Somitogenesis involve periodic signaling oscillations (known as the &#34;segmentation clock&#34;) that can be observed by the cyclic expression of several genes of the Notch, Wnt and Fgf signalling pathways in the presomitic mesoderm (e.g., Lfng)11,12. The current model of somitogenesis also postulates the existence of a &#34;maturation wavefront&#34;, a series of complex signalling gradients involving Fgf, Wnt and retinoic acid signaling that define the position of the posterior border of each new somite. A coordinated interaction between the &#34;segmentation clock&#34; and the &#34;maturation wavefront&#34; is therefore fundamental for the generation of these vertebrae precursor modules as perturbations in these key morphogenetic processes can result in embryonic lethality or in the formation of congenital malformations (e.g., scoliosis)13,14,15.
Despite substantial recent advances in imaging techniques, bioimage analysis methods and software, most studies of axial elongation and somitogenesis still rely on single/isolated two-dimensional image data (e.g., sections), which does not allow a full multidimensional tissue visualization and complicates clear differentiation between pathological malformations (i.e. due to mutations) vs normal morphological variation occurring during embryonic development16. Imaging in 3D has already uncovered novel morphogenetic movements, previously not identified by standard 2D methods17,18,19,20, highlighting the power of in toto imaging to understand the mechanisms of vertebrate somitogenesis and axial extension.
3D and 4D microscopy of mouse embryos, particularly live imaging, are technically challenging and require critical steps during sample preparation, image acquisition and data pre-processing in order to allow&#160;accurate and meaningful spatio-temporal analysis. Here, we describe a detailed protocol for live imaging and whole-mount immunofluorescence staining of mouse embryos, that can be used to study both NMPs and mesodermal cells during axial extension and segmentation. In addition, we also describe a protocol for optical projection tomography (OPT) of older embryos and fetuses, that allows 3D in toto visualization and quantification of pathological abnormalities that can result from problems during somitogenesis (e.g., bone fusion and scoliosis)13,21,22. Finally, we illustrate the power of 3D imaging reconstructions in the study and teaching of vertebrate segmentation and axial elongation.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Agarose low gelling temperature</td>
			<td>Sigma</td>
			<td>A9414</td>
			<td>Used to mounting embryos (e.g. for OPT)</td>
		</tr>
		<tr>
			<td>Amira software</td>
			<td>Thermofisher</td>
			<td>-</td>
			<td>Commerial software tool</td>
		</tr>
		<tr>
			<td>Anti-Brachyury (Goat polyclonal)</td>
			<td>R and D Systems</td>
			<td>AF2085 RRID:AB_2200235</td>
			<td>For immunofluorescence</td>
		</tr>
		<tr>
			<td>Anti-Sox2 (Rabbit monoclonal)</td>
			<td>Abcam</td>
			<td>ab92494 RRID:AB_10585428</td>
			<td>For immunofluorescence</td>
		</tr>
		<tr>
			<td>Anti-Tbx6 (Goat polyclonal)</td>
			<td>R and D Systems</td>
			<td>AF4744 RRID:AB_2200834</td>
			<td>For immunofluorescence</td>
		</tr>
		<tr>
			<td>Anti-Laminin111 (Rabbit polyclonal)</td>
			<td>Sigma</td>
			<td>L9393 RRID:AB_477163</td>
			<td>For immunofluorescence</td>
		</tr>
		<tr>
			<td>Anti-goat 488 (Donkey polyclonal)</td>
			<td>Molecular Probes</td>
			<td>A11055 RRID:AB_2534102</td>
			<td>For immunofluorescence</td>
		</tr>
		<tr>
			<td>Anti-rabbit 568 (Donkey polyclonal)</td>
			<td>ThermoFisher &#160; Scientific</td>
			<td>A10042 RRID:AB_2534017</td>
			<td>For immunofluorescence</td>
		</tr>
		<tr>
			<td>Benzyl Alcohol (99+%)</td>
			<td>(any)</td>
			<td>-</td>
			<td>Used to clear embryos (component of BABB)</td>
		</tr>
		<tr>
			<td>Benzyl Benzoate (99+%)</td>
			<td>(any)</td>
			<td>-</td>
			<td>Used to clear embryos (component of BABB)</td>
		</tr>
		<tr>
			<td>Bovine serum albumin</td>
			<td>Biowest</td>
			<td>P6154</td>
			<td>For immunofluorescence</td>
		</tr>
		<tr>
			<td>Coverglass 20x20 mm #0</td>
			<td>(any)</td>
			<td>-</td>
			<td>100um thick</td>
		</tr>
		<tr>
			<td>Coverglass 20x20 mm #1</td>
			<td>(any)</td>
			<td>-</td>
			<td>170um thick</td>
		</tr>
		<tr>
			<td>Coverglass 20x60 mm #1.5</td>
			<td>(any)</td>
			<td>-</td>
			<td>To use as &#8220;slides&#8221;</td>
		</tr>
		<tr>
			<td>DAPI (4&#8217;,6-Diamidino-2- Phenylindole Dihydrochloride)</td>
			<td>Life Technologies</td>
			<td>D3571</td>
			<td>For immunofluorescence</td>
		</tr>
		<tr>
			<td>Drishti software</td>
			<td>(open source)</td>
			<td>-</td>
			<td>Free software tool</td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Sigma</td>
			<td>ED2SS</td>
			<td>For demineralization</td>
		</tr>
		<tr>
			<td>Fiji/ImageJ software</td>
			<td>(open source)</td>
			<td>-</td>
			<td>Free software tool</td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>NZYtech</td>
			<td>MB01401</td>
			<td>For immunofluorescence</td>
		</tr>
		<tr>
			<td>Huygens software</td>
			<td>Scientific Volume Imaging</td>
			<td>-</td>
			<td>Commerial software tool</td>
		</tr>
		<tr>
			<td>HyClone defined fetal bovine serum</td>
			<td>GE Healthcare</td>
			<td>#HYCLSH30070.03</td>
			<td>For live imaging</td>
		</tr>
		<tr>
			<td>Hydrogen peroxide solution 30 %</td>
			<td>Milipore</td>
			<td>1085971000</td>
			<td>For clearing</td>
		</tr>
		<tr>
			<td>Imaris software</td>
			<td>Bitplane / Oxford instruments</td>
			<td>-</td>
			<td>Commerial software tool</td>
		</tr>
		<tr>
			<td>iSpacers</td>
			<td>SunJin Lab</td>
			<td>(varies)</td>
			<td>Use as spacers for preparations</td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>Gibco</td>
			<td>#25030&#8211;024</td>
			<td>For live imaging medium</td>
		</tr>
		<tr>
			<td>Low glucose DMEM</td>
			<td>Gibco</td>
			<td>11054020</td>
			<td>For live imaging medium</td>
		</tr>
		<tr>
			<td>M2 medium</td>
			<td>Sigma</td>
			<td>M7167</td>
			<td>To dissect embryos</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>VWR</td>
			<td>VWRC20847.307</td>
			<td>For dehydration and rehydration steps</td>
		</tr>
		<tr>
			<td>Methyl salicylate</td>
			<td>Sigma</td>
			<td>M6752</td>
			<td>Used to clear embryos</td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma</td>
			<td>P6148</td>
			<td>Used in solution to fix embryos</td>
		</tr>
		<tr>
			<td>Penicillin-streptomycin</td>
			<td>Sigma</td>
			<td>#P0781</td>
			<td>For live imaging medium</td>
		</tr>
		<tr>
			<td>PBS (Phosphate-buffered saline solution)</td>
			<td>Biowest</td>
			<td>L0615-500</td>
			<td>-</td>
		</tr>
		<tr>
			<td>RapiClear</td>
			<td>SunJin Laboratory</td>
			<td>RapiClear 1.52</td>
			<td>Used to clear embryos</td>
		</tr>
		<tr>
			<td>Secure-Sea hybridization chambers</td>
			<td>Sigma</td>
			<td>C5474</td>
			<td>Use as spacers for preparations</td>
		</tr>
		<tr>
			<td>simLab software</td>
			<td>SimLab soft</td>
			<td>-</td>
			<td>Commerial software tool</td>
		</tr>
		<tr>
			<td>Slide, depression concave glass - 75x25 mm</td>
			<td>(any)</td>
			<td>-</td>
			<td>To mount thick embryos.</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma</td>
			<td>T8787</td>
			<td>For immunofluorescence</td>
		</tr>
	</tbody>
</table>

three and four-dimensional visualization and analysis approaches to study vertebrate axial elongation and segmentation

Somitogenesis is a hallmark of vertebrate embryonic development. For years, researchers have been studying this process in a variety of organisms using a wide range of techniques encompassing ex vivo and in vitro approaches. However, most studies still rely on the analysis of two-dimensional (2D) imaging data, which limits proper evaluation of a developmental process like axial extension and somitogenesis involving highly dynamic interactions in a complex 3D space. Here we describe techniques that allow mouse live imaging acquisition, dataset processing, visualization and analysis in 3D and 4D to study the cells (e.g., neuromesodermal progenitors) involved in these developmental processes. We also provide a step-by-step protocol for optical projection tomography and whole-mount immunofluorescence microscopy in mouse embryos (from sample preparation to image acquisition) and show a pipeline that we developed to process and visualize 3D image data. We extend the use of some of these techniques and highlight specific features of different available software (e.g., Fiji/ImageJ, Drishti, Amira and Imaris) that can be used to improve our current understanding of axial extension and somite formation (e.g., 3D reconstructions). Altogether, the techniques here described emphasize the importance of 3D data visualization and analysis in developmental biology, and might help other researchers to better address 3D and 4D image data in the context of vertebrate axial extension and segmentation. Finally, the work also employs novel tools to facilitate teaching vertebrate embryonic development.

The representative results shown in this paper for both the live and the immunofluorescence imaging, were obtained using a two-photon system, with a 20 &#215; 1.0 NA water objective, the excitation laser tuned to 960 nm, and GaAsP photodetectors (as described in Dias et al. (2020)43. Optical projection tomography was done using a custom built OPenT scanner (as described in Gualda&#160;et al. (2013)28.
Live imaging (4D analysis)<b...

Watch this Scientific Journal Video about Three and Four-Dimensional Visualization and Analysis Approaches to Study Vertebrate Axial Elongation and Segmentation at JoVE.com

Three and Four-Dimensional Visualization and Analysis Approaches to Study Vertebrate Axial Elongation and Segmentation

Here, we describe computational tools and methods that allow visualization and analysis of three and four-dimensional image data of mouse embryos in the context of axial elongation and segmentation, obtained by in toto optical projection tomography, and by live imaging and whole-mount immunofluorescence staining using multiphoton microscopy.

Somitogenesis is a hallmark of vertebrate embryonic development. For years, researchers have been studying this process in a variety of organisms using a ...

three-four-dimensional-visualization-analysis-approaches-to-study

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Developmental Biology

3.6K Views.  Instituto Gulbenkian de Ciência. Here, we describe computational tools and methods that allow visualization and analysis of three and four-dimensional image data of mouse embryos in the context of axial elongation and segmentation, obtained by in toto optical projection tomography, and by live imaging and whole-mount immunofluorescence staining using multiphoton microscopy. 

Video: Three and Four-Dimensional Visualization and Analysis Approaches to Study Vertebrate Axial Elongation and Segmentation

Ex Vivo Culture of Pharyngeal Arches to Study Heart and Muscle Progenitors and Their Niche

The pharyngeal mesoderm of developing embryos contributes to broad regions of head and heart musculature. We have developed a novel method to study head and heart progenitor cell development with pharyngeal arches (also known as branchial arches) ex vivo. Using this method, we have recently described that the second pharyngeal arch contains self-renewing heart progenitors and serves as a microenvironment for expansion of the progenitors during mouse heart development. The progenitor cells remain undifferentiated and expansive inside the arch, but quickly become functional cardiomyocytes as they migrate out of the arch. We also reported that first pharyngeal arch contains muscle progenitors giving rise to myotubes after leaving the arch. Here, we demonstrate the procedure for the dissection and ex vivo culture of first and second pharyngeal arches from developing mouse embryos. The method enables one to study head and heart progenitor/muscle development, including cardiomyocyte and myotube formation in detail ex vivo.

Ex Vivo Culture of Pharyngeal Arches to Study Heart and Muscle Progenitors and Their Niche

Here, we present a protocol to culture pharyngeal arches to study the biology of heart and muscle progenitor cells and their microenvironment.

The pharyngeal mesoderm of developing embryos contributes to broad regions of head and heart musculature. We have developed a novel method to study head ...

Visualization of Chondrocyte Intercalation and Directional Proliferation via Zebrabow Clonal Cell Analysis in the Embryonic Meckel&#8217;s Cartilage

Development of the vertebrate craniofacial structures requires precise coordination of cell migration, proliferation, adhesion and differentiation. Patterning of the Meckel&#39;s cartilage, a first pharyngeal arch derivative, involves the migration of cranial neural crest (CNC) cells and the progressive partitioning, proliferation and organization of differentiated chondrocytes. Several studies have described CNC migration during lower jaw&#160;morphogenesis, but the details of how the chondrocytes achieve organization in the growth and extension of Meckel&#8217;s cartilage remains unclear. The sox10 restricted and chemically induced Cre recombinase-mediated recombination generates permutations of distinct fluorescent proteins (RFP, YFP and CFP), thereby creating a multi-spectral labeling of progenitor cells and their progeny, reflecting distinct clonal populations. Using confocal time-lapse photography, it is possible to observe the chondrocytes behavior during the development of the zebrafish Meckel&#8217;s cartilage.
Multispectral cell labeling enables scientists to demonstrate extension of the Meckel&#8217;s chondrocytes.&#160;During extension phase of the Meckel&#8217;s cartilage, which prefigures the mandible, chondrocytes intercalate to effect extension as they stack in an organized single-cell layered row. Failure of this organized intercalating process to mediate cell extension provides the cellular mechanistic explanation for hypoplastic mandible that we observe in mandibular malformations.

Visualization of Chondrocyte Intercalation and Directional Proliferation via Zebrabow Clonal Cell Analysis in the Embryonic Meckel&amp;#8217;s Cartilage

Cell organization of craniofacial bones has long been hypothesized but never directly visualized. Multi-spectral cell labeling and in vivo live imaging allows visualization of dynamic cell behavior in zebrafish lower jaw. Here, we detail the protocol to manipulate Zebrabow transgenic fish and directly observe cell intercalation and morphological changes of chondrocytes in the Meckel&#8217;s cartilage.

Development of the vertebrate craniofacial structures requires precise coordination of cell migration, proliferation, adhesion and differentiation. ...

Kinetic Measurement and Real Time Visualization of Somatic Reprogramming

Somatic reprogramming has enabled the conversion of adult cells to induced pluripotent stem cells (iPSC) from diverse genetic backgrounds and disease phenotypes. Recent advances have identified more efficient and safe methods for introduction of reprogramming factors. However, there are few tools to monitor and track the progression of reprogramming. Current methods for monitoring reprogramming rely on the qualitative inspection of morphology or staining with stem cell-specific dyes and antibodies. Tools to dissect the progression of iPSC generation can help better understand the process under different conditions from diverse cell sources. 
This study presents key approaches for kinetic measurement of reprogramming progression using flow cytometry as well as real-time monitoring via imaging. To measure the kinetics of reprogramming, flow analysis was performed at discrete time points using antibodies against positive and negative pluripotent stem cell markers. The combination of real-time visualization and flow analysis enables the quantitative study of reprogramming at different stages and provides a more accurate comparison of different systems and methods. Real-time, image-based analysis was used for the continuous monitoring of fibroblasts as they are reprogrammed in a feeder-free medium system. The kinetics of colony formation was measured based on confluence in the phase contrast or fluorescence channels after staining with live alkaline phosphatase dye or antibodies against SSEA4 or TRA-1-60. The results indicated that measurement of confluence provides semi-quantitative metrics to monitor the progression of reprogramming.

The protocol presented in this study describes methods for the real-time monitoring of reprogramming progression via the kinetic measurement of positive and negative pluripotent stem cell markers using flow cytometry analysis. The protocol also includes the imaging-based assessment of morphology, and marker or reporter expression during iPSC generation.

Somatic reprogramming has enabled the conversion of adult cells to induced pluripotent stem cells (iPSC) from diverse genetic backgrounds and disease ...

Visualization and Quantitative Analysis of Embryonic Angiogenesis in Xenopus tropicalis

Blood vessels supply oxygen and nutrients throughout the body, and the formation of the vascular network is under tight developmental control. The efficient in vivo visualization of blood vessels and the reliable quantification of their complexity are key to understanding the biology and disease of the vascular network. Here, we provide a detailed method to visualize blood vessels with a commercially available fluorescent dye, human plasma acetylated low density lipoprotein DiI complex (DiI-AcLDL), and to quantify their complexity in Xenopus tropicalis. Blood vessels can be labeled by a simple injection of DiI-AcLDL into the beating heart of an embryo, and blood vessels in the entire embryo can be imaged in live or fixed embryos. Combined with gene perturbation by the targeted microinjection of nucleic acids and/or the bath application of pharmacological reagents, the roles of a gene or of a signaling pathway on vascular development can be investigated within one week without resorting to sophisticated genetically engineered animals. Because of the well-defined venous system of Xenopus and its stereotypic angiogenesis, the sprouting of pre-existing vessels, vessel complexity can be quantified efficiently after perturbation experiments. This relatively simple protocol should serve as an easily accessible tool in diverse fields of cardiovascular research.

Visualization and Quantitative Analysis of Embryonic Angiogenesis in Xenopus tropicalis

This protocol demonstrates a fluorescence-based method to visualize the vasculature and to quantify its complexity in Xenopus tropicalis. Blood vessels can be imaged minutes after the injection of a fluorescent dye into the beating heart of an embryo after genetic and/or pharmacological manipulations to study cardiovascular development in vivo.

Blood vessels supply oxygen and nutrients throughout the body, and the formation of the vascular network is under tight developmental control. The ...

Using In Vivo and Tissue and Cell Explant Approaches to Study the Morphogenesis and Pathogenesis of the Embryonic and Perinatal Aorta

The aorta is the largest artery in the body. The aortic wall is composed of an inner layer of endothelial cells, a middle layer of alternating elastic lamellae and smooth muscle cells (SMCs), and an outer layer of fibroblasts and extracellular matrix. In contrast to the widespread study of pathological models (e.g., atherosclerosis) in the adult aorta, much less is known about the embryonic and perinatal aorta. Here, we focus on SMCs and provide protocols for the analysis of the morphogenesis and pathogenesis of embryonic and perinatal aortic SMCs in normal development and disease. Specifically, the four protocols included are: i) in vivo embryonic fate mapping and clonal analysis; ii) explant embryonic aorta culture; iii) SMC isolation from the perinatal aorta; and iv) subcutaneous osmotic mini-pump placement in pregnant (or non-pregnant) mice. Thus, these approaches facilitate the investigation of the origin(s), fate, and clonal architecture of SMCs in the aorta in vivo. They allow for modulating embryonic aorta morphogenesis in utero by continuous exposure to pharmacological agents. In addition, isolated aortic tissue explants or aortic SMCs can be used to gain insights into the role of specific gene targets during fundamental processes such as muscularization, proliferation, and migration. These hypothesis-generating experiments on isolated SMCs and the explanted aorta can then be assessed in the in vivo context through pharmacological and genetic approaches.

Using In Vivo and Tissue and Cell Explant Approaches to Study the Morphogenesis and Pathogenesis of the Embryonic and Perinatal Aorta

Protocols for studying the embryonic and perinatal murine aorta using in vivo clonal analysis and fate mapping, aortic explants, and isolated smooth muscle cells are detailed here. These diverse approaches facilitate the investigation of the morphogenesis of the embryonic and perinatal aorta in normal development and the pathogenesis in disease.

The aorta is the largest artery in the body. The aortic wall is composed of an inner layer of endothelial cells, a middle layer of alternating elastic ...

Correlative Super-resolution and Electron Microscopy to Resolve Protein Localization in Zebrafish Retina

We present a method to investigate the subcellular protein localization in the larval zebrafish retina by combining super-resolution light microscopy and scanning electron microscopy. The sub-diffraction limit resolution capabilities of super-resolution light microscopes allow improving the accuracy of the correlated data. Briefly, 110 nanometer thick cryo-sections are transferred to a silicon wafer and, after immunofluorescence staining, are imaged by super-resolution light microscopy. Subsequently, the sections are preserved in methylcellulose and platinum shadowed prior to imaging in a scanning electron microscope (SEM). The images from these two microscopy modalities are easily merged using tissue landmarks with open source software. Here we describe the adapted method for the larval zebrafish retina. However, this method is also applicable to other types of tissues and organisms. We demonstrate that the complementary information obtained by this correlation is able to resolve the expression of mitochondrial proteins in relation with the membranes and cristae of mitochondria as well as to other compartments of the cell.

This protocol describes the necessary steps to obtain subcellular protein localization results on zebrafish retina by correlating super-resolution light microscopy and scanning electron microscopy images.

We present a method to investigate the subcellular protein localization in the larval zebrafish retina by combining super-resolution light microscopy and ...

Three-dimensional Rendering and Analysis of Immunolabeled, Clarified Human Placental Villous Vascular Networks

Nutrient and gas exchange between mother and fetus occurs at the interface of the maternal intervillous blood and the vast villous capillary network that makes up much of the parenchyma of the human placenta. The distal villous capillary network is the terminus of the fetal blood supply after several generations of branching of vessels extending out from the umbilical cord. This network has a contiguous cellular sheath, the syncytial trophoblast barrier layer, which prevents mixing of fetal blood and the maternal blood in which it is continuously bathed. Insults to the integrity of the placental capillary network, occurring in disorders such as maternal diabetes, hypertension and obesity, have consequences that present serious health risks for the fetus, infant, and adult. To better define the structural effects of these insults, a protocol was developed for this study that captures capillary network structure on the order of 1 - 2 mm3 wherein one can investigate its topological features in its full complexity. To accomplish this, clusters of terminal villi from placenta are dissected, and the trophoblast layer and the capillary endothelia are immunolabeled. These samples are then clarified with a new tissue clearing process which makes it possible to acquire confocal image stacks to z- depths of ~1 mm. The three-dimensional renderings of these stacks are then processed and analyzed to generate basic capillary network measures such as volume, number of capillary branches, and capillary branch end points, as validation of the suitability of this approach for capillary network characterization.

This study presents a protocol for the reversible tissue clearing, immunostaining, 3D-rendering and analysis of vascular networks in human placenta villi samples on the order of 1 - 2 mm3.

Nutrient and gas exchange between mother and fetus occurs at the interface of the maternal intervillous blood and the vast villous capillary network that ...

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and chromosome dynamics. While the germline is an excellent model, the analysis is often two dimensional due to the time and labor required for three-dimensional analysis. Major readouts in such studies are the number/position of nuclei and protein distribution within the germline. Here, we present a method to perform automated analysis of the germline using confocal microscopy and computational approaches to determine the number and position of nuclei in each region of the germline. Our method also analyzes germline protein distribution that enables the three-dimensional examination of protein expression in different genetic backgrounds. Further, our study shows variations in cytoskeletal architecture in distinct regions of the germline that may accommodate specific spatial developmental requirements. Finally, our method enables automated counting of the sperm in the spermatheca of each germline. Taken together, our method enables rapid and reproducible phenotypic analysis of the C. elegans germline.

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

We present an automated method for three-dimensional reconstruction of the Caenorhabditis elegans germline. Our method determines the number and position of each nucleus within the germline and analyses germline protein distribution and cytoskeletal structure.

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and ...

Visualization and Analysis of Pharyngeal Arch Arteries using Whole-mount Immunohistochemistry and 3D Reconstruction

Improper formation or remodeling of the pharyngeal arch arteries (PAAs) 3, 4, and 6 contribute to some of the most severe forms of congenital heart disease. To study the formation of PAAs, we developed a protocol using whole-mount immunofluorescence coupled with benzyl alcohol/benzyl benzoate (BABB) tissue clearing, and confocal microscopy. This allows for the visualization of the pharyngeal arch endothelium at a fine cellular resolution as well as the 3D connectivity of the vasculature. Using software, we have established a protocol to quantify the number of endothelial cells (ECs) in PAAs, as well as the number of ECs within the vascular plexus surrounding the PAAs within pharyngeal arches 3, 4, and 6. When applied to the whole embryo, this methodology provides a comprehensive visualization and quantitative analysis of embryonic vasculature.

Here, we describe a protocol to visualize and analyze the pharyngeal arch arteries 3, 4, and 6 of mouse embryos using whole-mount immunofluorescence, tissue clearing, confocal microscopy, and 3D reconstruction.

Improper formation or remodeling of the pharyngeal arch arteries (PAAs) 3, 4, and 6 contribute to some of the most severe forms of congenital heart ...

A Drosophila Model to Study Wound-induced Polyploidization

Polyploidy is a frequent phenomenon whose impact on organismal health and disease is still poorly understood. A cell is defined as polyploid if it contains more than the diploid copy of its chromosomes, which is a result of endoreplication or cell fusion. In tissue repair, wound-induced polyploidization (WIP) has been found to be a conserved healing strategy from fruit flies to vertebrates. WIP has several advantages over cell proliferation, including resistance to oncogenic growth and genotoxic stress. The challenge has been to identify why polyploid cells arise and how these unique cells function. Provided is a detailed protocol to study WIP in the adult fruit fly epithelium where polyploid cells are generated within 2 days after a puncture wound. Taking advantage of D. melanogaster&#39;s extensive genetic tool kit, the genes required to initiate and regulate WIP, including Myc, have begun to be identified. Continued studies using this method can reveal how other genetic and physiological variables including sex, diet, and age regulate and influence WIP&#39;s function.

A Drosophila Model to Study Wound-induced Polyploidization

Wound-induced polyploidization is a conserved tissue repair strategy where cells grow in size instead of dividing to compensate for cell loss. Here is a detailed protocol on how to use the fruit fly as a model to measure ploidy and its genetic regulation in epithelial wound repair.