Z.C. acknowledges the support from Dartmouth startup fund and the Branco Weiss- Society for Science fellowship, administered by ETH Zurich. The authors thank Drs. Larry A. Taber, Benjamen A. Filas, Qiaohang Guo, and Yunfei Shi for helpful discussions, as well as the anonymous reviewers for comments.&#160;This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1313911. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors(s) and do not necessarily reflect the views of the National Science Foundation.&#160;

1. Preparation of Tissue Culture Media
<ol>
	<li>Use a 0.5 L bottle of Dulbecco&#39;s Modified Eagle&#39;s Medium (DMEM) with 4.5 g/L glucose, sodium bicarbonate, and L-glutamine as the base for the culture media.</li>
	<li>In a sterile laminar flow hood, add 10 mL of antibiotics to the 0.5 L of DMEM.</li>
	<li>Using a sterile pipette, transfer 50 mL of the DMEM antibiotics solution to a sterile 50 mL conical tube.</li>
	<li>Add 50 mL of chick serum to the remaining DMEM antibiotics solution in the 0.5 L bottle in the sterile hood.</li>
	<li>Store the final solution (referred to hereafter as chick culture media [CCM]) in 50 mL conical tube aliquots at -20 &#176;C.</li>
</ol>
2. Egg Incubation
<ol>
	<li>Use delicate wipes with 70% ethanol to clean fertilized specific pathogen-free White Leghorn chicken eggs. Arrange eggs in a longitudinal orientation on holders.</li>
	<li>Turn on an egg incubator to set a target temperature of 37.5 &#176;C and maintain the humidity at 48 - 55%.&#160;The humidity is controlled by adding an appropriate amount of water to the incubator.</li>
	<li>Incubate the eggs to HH11-13, approximately 40 - 44 h.</li>
	<li>Let the eggs cool down at room temperature for approximately 15 - 30 min prior to spraying/cleaning with 70% ethanol.</li>
</ol>
3. Pull Glass Capillaries
<ol>
	<li>Mount a 10 cm-long glass capillary tubes with an outer diameter of 1.0 mm and an inner diameter of 0.5 mm on a micropipette puller.</li>
	<li>Set the heat and pull parameters to 750 and 400, respectively. Press the pull button to pull the capillary tube into thin needles.</li>
</ol>
4. Filter Paper Carrier Method
<ol>
	<li>Cut circles of approximately 3 cm in diameter from filter paper.</li>
	<li>Cut a rectangle roughly 1 cm by 2 cm from the circle using a hole puncher. Make sure to remove any protruding or sharp corners.</li>
</ol>
5. Embryo Harvesting and Preparation
<ol>
	<li>Crack eggs from the bottom, pull apart the shell gently and carefully deposit contents into a 150 mm x 15 mm&#160;petri dish. To ensure the embryo side is up, keep the eggs in the same orientation they were incubated while cracking them.</li>
	<li>Remove the thin albumin using a disposable Pasteur pipette.</li>
	<li>Separate the thick albumin from the yolk using blunt ended forceps.&#160;Ensure that the thick albumin has been removed by lightly scraping the top of the yolk with the blunt ended forceps.</li>
	<li>Use fine-tipped forceps to center and&#160;place a filter paper ring over the embryo, matching the long axis of the ring with the long axis of the embryo.</li>
	<li>Cut the yolk surrounding the filter paper ring with scissors.</li>
	<li>Pull the ring and embryo off the yolk in an oblique direction towards the site where the yolk was first cut.</li>
	<li>Rinse the embryos in two sequential 100-mm dishes with room temperature 1x phosphate buffered saline (PBS).</li>
	<li>Place a filter paper ring into a 35-mm petri dish first. Then place the embryo dorsal side up onto the filter paper already in 35-mm petri dish.</li>
	<li>Place a stainless-steel ring on top of the filter paper sandwich. Make sure not to damage the embryo.</li>
	<li>Add 3&#160;mL&#160;of the previously prepared CCM to each petri dish.</li>
	<li>Remove the VM of each embryo by lightly skimming the pulled capillary needle across the top of the embryo and peeling the VM away, starting from the anterior end (right above the forebrain) and proceeding to the&#160;notochord (Figure 1A).</li>
	<li>Place eight 35-mm Petri dishes into one 150 mm dish that was lined with water saturated delicate task wipes (to maintain humidity).</li>
	<li>Place the 150-mm petri dish into a sealable plastic bag then fill the bag with a gas mixture comprised of 95% O2 and 5% CO2.</li>
	<li>Seal the bag and place it in a 37.5 &#176;C incubator.</li>
	<li>Incubate the embryos for an additional 27 h until HH15-HH16 (Figure 1B).</li>
</ol>
6. Inducing Surface Tension
<ol>
	<li>Remove the embryos from the incubator and use an optical coherence tomography (OCT) system to image them. Use OCT to determine the torsional angle of the neural tube (NT) (Figure 2).</li>
	<li>Transfer the embryos to a light microscope and visualize at 10X magnification. Use a 200 microliter pipette to incrementally remove 0.2 mL of media from the petri dish.</li>
	<li>Take brightfield images at each interval to observe the effects of the media-air interface on the embryo.</li>
	<li>Remove media until the surface tension across the embryo induces torsion (Figure 1C).</li>
	<li>Image the embryo using the OCT system once again to establish a final torsional angle for comparison to control embryos.&#160; NOTE: The Bright-field images were acquired by using a dissecting microscope. An optical coherence tomography system with an attached microscope was used to acquire cross-sectional image stacks of live embryos. Images were obtained in a 3 x 10 mm x 3 mm3 scanning domain, then processed in an imaging software. Lastly, the physical model images were taken with a digital single-lens reflex camera.</li>
</ol>
7. Physical Modeling of Surface Tension/VM Forces
<ol>
	<li>Develop a simplified 3D geometry that resembles an embryo between HH14-17 in commercial modeling software (Figure 3A).</li>
	<li>Design the negative mold of the 3D geometry in commercial 3D computer graphics software.</li>
	<li>Use a 3D printer loaded with 1.75 mm acrylonitrile butadiene styrene filament to 3D print the designed mold, in stereolithographic (.stl) format.</li>
	<li>To cast the mold, mix silicone rubber elastomer components A and B in equal parts and pour the mix into the mold promptly; set the casting mold to cure at room temperature for 12 h (Figure 3B).</li>
	<li>Mark the physical model of the embryo along the NT on the dorsal side to visualize torsion.</li>
	<li>Use a coverslip to replicate the force applied to the 3D physical model which mimics&#160;that of the VM or surface tension (Figure 3D).</li>
	<li>Insert a series of rigid wires of equal length to the side of the physical model. After the coverslip exerts an external force on the brain model, the wires become tilted at an angle that depends on the location. Determine the rotational angle by arctan of the projected length over the original length of each wire (Figure 3E).</li>
</ol>
8. Altering the Direction of the Heart Loop
<ol>
	<li>Follow the steps in 3.1 and 3.2 to obtain a pulled capillary tube.</li>
	<li>Follow the steps in 5.1 through 5.10 to prepare the embryo.</li>
	<li>Use a pair of forceps to flip the filter paper so that the embryo becomes ventral-side-up.</li>
	<li>Use the pulled capillary tube to cut&#160;open a slit in the splanchnopleure (SPL) membrane.</li>
	<li>Use the capillary tube to exert a mechanical force to push the heart from the right-hand side to the left-hand side.</li>
	<li>Follow the steps in 5.12 through 5.15 to observe the change in torsion.</li>
</ol>

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The authors declare no conflicts of interest.

While physical phenomena play an integral role in morphogenesis26,27,28,29,30, the specific mechanical mechanisms, along with the coordination of mechanical and molecular mechanisms, remain largely unexplored. It is known that the ventral flexure and rightward torsion of the primitive brain are two central processes that contribute to early embryonic morphogen...

Modern developmental biology research largely focuses on understanding development from the perspective of molecular genetics1,2,3,4,5,6,7,8,9,10,11,12,13. It is known that physical phenomena play a central role in morphogenesis, or the generation of biological form14,15,16,17; however, specific mechanical mechanisms of development remain largely unstudied. Ventral flexure and rightward torsion of the primitive brain tube after Hamburger-Hamilton stage 11 (HH 11)18 are the two main processes that contribute to embryonic shape change19,20. In particular, the physical mechanism underlying the torsional development in the embryonic brain remains incompletely understood.
The embryonic torsion in chick embryo is among the earliest morphogenetic events of left-right (L-R) asymmetry in development. When the process of L-R asymmetry is perturbed, birth defects such as situs inversus, isomerism, or heterotaxia will occur21. 
Here we present a protocol which combines ex-ovo experiments22,23 with physical modeling to characterize mechanical forces during early embryonic brain development. The goal of the method presented is to identify the mechanical forces responsible for brain torsion and the factors that affect the degree of torsion during early development12. Based on the experimental observation that the vitelline membrane (VM) constrains the dorsal side of the embryo, we hypothesized that the VM provides the force necessary to induce torsion of the developing brain. Therefore, in this method, we removed the part of the VM that covers the brain area to find out the effects on brain torsion. Furthermore, the method of applying fluid surface tension was used to confirm the mechanical role of the VM and provide an estimate of the force needed for brain torsion, which had not been done previously. Measuring the forces during embryonic morphogenesis is a challenging task. Notably, in a pioneering study, Camp&#224;s and co-workers24 developed a novel method to quantify the cellular stresses using injected microdroplets. Nevertheless, this method was limited to measure forces at the cellular level, hence not applicable to probe forces at tissue- or organism-level. The protocol presented in this paper was developed to partially fill this gap.

<table><tbody><tr><td>Fertilized Specific pathogen-free White Leghorn chicken eggs</td><td>Charles River</td><td></td><td></td></tr><tr><td>Optical Coherent Tomography Microscope</td><td>Thorlabs</td><td>GAN220C1</td><td></td></tr><tr><td>Silicone elastomer</td><td>Smooth-On, Inc.</td><td>EcoFlex 00-50</td><td></td></tr><tr><td>Dissecting microscope</td><td>Leica</td><td>MZ8</td><td></td></tr><tr><td>Dulbecco&amp;rsquo;s Modified Eagle&amp;rsquo;s Medium (DMEM)</td><td>Lonza</td><td>12-604F</td><td></td></tr><tr><td>Antibiotics</td><td>Sigma</td><td>P4083</td><td></td></tr><tr><td>Chick serum</td><td>Sigma</td><td>C5405</td><td></td></tr><tr><td>Micropipette puller</td><td>Sutter Instrument</td><td>Model P-30</td><td></td></tr><tr><td>Filter paper</td><td>Whatman</td><td>5202-110</td><td></td></tr><tr><td>Phosphate buffered saline (PBS)</td><td>Corning</td><td>21-040-CV</td><td></td></tr><tr><td>Comsol MultiPhysics</td><td>Comsol</td><td></td><td></td></tr><tr><td>3D computer graphics software</td><td>Rhino 5</td><td></td><td></td></tr><tr><td>Microscope attached with OCT</td><td>Nikon&amp;nbsp;</td><td>FN1</td><td></td></tr><tr><td>Digital single-lens reflex camera</td><td>EOS&amp;nbsp;</td><td>Rebel T3i</td><td></td></tr></tbody></table>

probing the roles of physical forces in early chick embryonic morphogenesis

Embryonic development is traditionally studied from the perspective of biomolecular genetics, but the fundamental importance of mechanics in morphogenesis is becoming increasingly recognized. In particular, the embryonic chick heart and brain tube, which undergo drastic morphological changes as they develop, are among the prime candidates to study the role of physical forces in morphogenesis. Progressive ventral bending&#160;and rightward torsion of the tubular embryonic chick brain happen at the earliest stage of organ-level left-right asymmetry in chick embryonic development. The vitelline membrane (VM) constrains the dorsal side of the embryo and has been implicated in providing the force necessary to induce torsion of the developing brain. Here we present a combination of new ex-ovo experiments and physical modeling to identify the mechanics of brain torsion. At Hamburger-Hamilton stage 11, embryos are harvested and cultured ex ovo (in media). The VM is subsequently removed using a pulled capillary tube. By controlling the level of the fluid and subjecting the embryo to a fluid-air interface, the fluid surface tension of the media can be used to replace the mechanical role of the VM. Microsurgery experiments were also performed to alter the position of the heart to find the resultant change in the chirality of brain torsion. Results from this protocol illustrate the fundamental roles of mechanics in driving morphogenesis.

In this study, the VM of the embryo at HH11 was removed from the anterior end to the thoracic flexure. The embryos were imaged by an OCT system. At this stage, the torsion of brain tube has not started (Figure 1A). After being incubated to HH15-16, embryos with their VM removed exhibited reduced brain tube torsion, approximately 35 degrees (Figure 1B) compared to control embryos, which exhibit torsion of around 90 degrees. When t...

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Probing the Roles of Physical Forces in Early Chick Embryonic Morphogenesis

Here, we present a protocol introducing a set of new ex-ovo experiments and physical modeling approaches for studying the mechanics of morphogenesis during early chick embryonic brain torsion.

Embryonic development is traditionally studied from the perspective of biomolecular genetics, but the fundamental importance of mechanics in morphogenesis ...

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Research

JoVE Journal

Bioengineering

7.2K Views.  Dartmouth College. Hier presenteren we een protocol voor de invoering van een reeks nieuwe ex-ovo experimenten en fysieke modellering benaderingen voor het bestuderen van de mechanica van de morfogenese tijdens de vroege embryonale hersenen torsie van het kuiken.

Video: Probing the Roles of Physical Forces in Early Chick Embryonic Morphogenesis

Grafting of Beads into Developing Chicken Embryo Limbs to Identify Signal Transduction Pathways Affecting Gene Expression

Using chicken embryos it is possible to test directly the effects of either growth factors or specific inhibitors of signaling pathways on gene expression and activation of signal transduction pathways. This technique allows the delivery of signaling molecules at precisely defined developmental stages for specific times. After this embryos can be harvested and gene expression examined, for example by in situ hybridization, or activation of signal transduction pathways observed with immunostaining.
In this video heparin beads soaked in FGF18 or AG 1-X2 beads soaked in U0126, a MEK inhibitor, are grafted into the limb bud in ovo. This shows that FGF18 induces expression of MyoD and ERK phosphorylation and both endogenous and FGF18 induced MyoD expression is inhibited by U0126. Beads soaked in a retinoic acid antagonist can potentiate premature MyoD induction by FGF18.
This approach can be used with a wide range of different growth factors and inhibitors and is easily adapted to other tissues in the developing embryo.

By grafting beads soaked in growth factors or specific inhibitors of signaling pathways into developing embryos it is possible to directly test their effects in vivo. In this protocol beads are grafted into the limb bud to determine the effects of these molecules on gene expression and signal transduction.

Using chicken embryos it is possible to test directly the effects of either growth factors or specific inhibitors of signaling pathways on gene expression ...

Developmental Biology

Application of Impermeable Barriers Combined with Candidate Factor Soaked Beads to Study Inductive Signals in the Chick

The chick embryo provides a superb vertebrate model that can be used to dissect developmental questions in a direct way. Its accessibility and robustness following surgical intervention are key experimental strengths. Mica plates were the first barriers used to prevent chick limb bud initiation1. Protocols that use aluminum foil as an impermeable barrier to wing bud or leg bud induction and or initiation are described. We combine this technique with bead placement lateral to the barrier to exogenously supply candidate endogenous factors that have been blocked by the barrier. The results are analyzed using in situ hybridization of subsequent gene expression. Our main focus is on the role of retinoic acid signaling in the induction and later initiation of the chick embryo fore and hindlimb. We use BMS 493 (an inverse agonist of retinoic acid receptors (RAR)) soaked beads implanted in the lateral plate mesoderm (LPM) to mimic the effect of a barrier placed between the somites (a source of retinoic acid (RA)) and the LPM from which limb buds grow. Modified versions of these protocols could also be used to address other questions on the origin and timing of inductive cues. Provided the region of the chick embryo is accessible at the relevant developmental stage, a barrier could be placed between the two tissues and consequent changes in development studied. Examples may be found in the developing brain, axis extension and in organ development, such as liver or kidney induction.

Protocols using impermeable barriers to block induction events between tissues of the main body axis and flank in the chick embryo required for limb formation are described. Beads soaked in candidate inductive signals are used to overcome the effect of barrier placement and analysis of gene expression confirms this.

The chick embryo provides a superb vertebrate model that can be used to dissect developmental questions in a direct way. Its accessibility and robustness ...

Double Whole Mount in situ Hybridization of Early Chick Embryos

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying  gene expression in brain, neural tube, somite and heart primordia formation. This video demonstrates the different steps in 2-color whole mount in situ hybridization; First, the embryo is dissected from the egg and fixed in paraformaldehyde. Second, the embryo is processed for prehybridization. The embryo is then hybridized with two different probes, one coupled to DIG, and one coupled to FITC.  Following overnight hybridization, the embryo is incubated with DIG coupled antibody. Color reaction for DIG substrate is performed, and the region of interest appears blue. The embryo is then incubated with FITC coupled antibody. The embryo is processed for color reaction with FITC, and the region of interest appears red. Finally, the embryo is fixed and processed for phtograph and sectioning. A troubleshooting guide is also presented.

This video demonstrates 2-color whole mount in situ hybridization, a method by which the spatial and temporal expression pattern of 2 different genes can be visualized in young chick embryos. This method was originally introduced by David Wilkinson, Domingos Henrique, Phil Ingham and David Ish -Horowicz.

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ...

Biology

Assay for Neural Induction in the Chick Embryo

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying the formation and initial patterning of the nervous system. This video demonstrates how to graft organizer tissue into a host, a method by which Hensen s node (the organizer in the chick embryo) is grafted to a host competent ectoderm. The organizer graft instructs overlying na ve tissue to adopt a neural fate via neural inducing signals. This mechanism is referred to as neural induction, and constitutes the initial step in the formation of brain and spinal cord in amniotes. This method is essentially used for the characterization of putative neural inducing molecules in chick. This video demonstrates the different steps in the assay for neural induction; First, the donnor embryo is explanted and pinned on a dish. Then, the host embryo is prepared for New culture. The graft is excised and transplanted to the host area pellucida margin. The host is cultured for 18-22 hrs. The assembly is fixed and processed for further applications (e.g. in situ hybridization). This method was originally devised by Waddington 1,2 and Gallera 3,4.

Neural induction is the first step in the formation of the brain. It is a mechanism by which Hensen's node (organizer), instructs adjacent tissue to adopt a neural fate, i.e. to give rise to the nervous system. This video demonstrates an assay for neural induction in chick embryo.

Organotypic Culture Method to Study the Development Of Embryonic Chicken Tissues

The embryonic chicken is commonly used as a reliable model organism for vertebrate development. Its accessibility and short incubation period makes it ideal for experimentation. Currently, the study of these developmental pathways in the chicken embryo is conducted by applying inhibitors and drugs at localized sites and at low concentrations using a variety of methods. In vitro tissue&#160;culturing is a technique that enables the study of tissues separated from the host organism, while simultaneously bypassing many of the physical limitations present when working with whole embryos, such as the susceptibility of embryos to high doses of potentially lethal chemicals. Here, we present an organotypic culturing protocol for culturing the embryonic chicken half head in vitro, which presents new opportunities for the examination of developmental processes beyond the currently established methods.

Here, we present an organotypic culturing protocol to grow embryonic chicken organs in vitro. Using this method, the development of embryonic chicken tissue can be studied, while maintaining a high degree of control over the culture environment.

The embryonic chicken is commonly used as a reliable model organism for vertebrate development. Its accessibility and short incubation period makes it ...

Chicken Recombinant Limbs Assay to Understand Morphogenesis, Patterning, and Early Steps in Cell Differentiation

Cell differentiation is the fine-tuned process of cell commitment leading to the formation of different specialized cell types during the establishment of developing tissues and organs. This process is actively maintained in adulthood. Cell differentiation is an ongoing process during the development and homeostasis of organs. Understanding the early steps of cell differentiation is essential to know other complex processes such as morphogenesis. Thus, recombinant chicken limbs are an experimental model that allows the study of cell differentiation and pattern generation under embryonic patterning signals. This experimental model imitates an in vivo environment; it assembles reaggregated cells into an ectodermal cover obtained from an early limb bud. Later, ectoderms are transferred and implanted in a chick embryo receptor to allow its development. This assay was mainly used to evaluate mesodermal limb bud cells; however, it can be applied to other stem or progenitor cells from other organisms.

Recombinant limbs are a powerful experimental model that allows for studying the process of cell differentiation and the generation of patterns under the influence of embryonic signals. This protocol presents a detailed method for generating recombinant limbs with chicken limb-mesodermal cells, adaptable to other cell types obtained from different organisms.

Cell differentiation is the fine-tuned process of cell commitment leading to the formation of different specialized cell types during the establishment of ...

Analysis of Cell Differentiation, Morphogenesis, and Patterning During Chicken Embryogenesis Using the Soaked-Bead Assay

A multitude of genetic programs is activated during embryonic development that orchestrates cell differentiation to generate an astounding diversity of somatic cells, tissues, and organs. The precise activation of these genetic programs is regulated by morphogens, diffusible molecules that direct cell fate at different thresholds. Understanding how genetic activation coordinates morphogenesis requires the study of local interactions triggered by morphogens during development. The use of beads soaked in proteins or drugs implanted into distinct regions of the embryo enables studying the role of specific molecules in the establishment of digits and other developmental processes. This experimental technique provides information on the control of cell induction, cell fate, and pattern formation. Thus, this soaked bead assay is an extremely powerful and valuable experimental tool applicable to other embryonic models.

The soaked bead assay involves targeted delivery of test reagent at any developmental time point to study the regulation of cell differentiation and morphogenesis. A detailed protocol, applicable to any experimental animal model, for preparing three different types of soaked beads and implanting these in the interdigit of a chicken embryo is presented.

A multitude of genetic programs is activated during embryonic development that orchestrates cell differentiation to generate an astounding diversity of ...

A Comprehensive Review of Avian Embryonic Skin Explant Culture Protocols

Using Avian Skin Explants to Study Tissue Patterning and Organogenesis

The developing avian skin during embryogenesis is a unique model that can provide valuable insights into tissue patterning. Here three variations on skin explant cultures to examine different aspects of skin development are described. First, ex vivo organ cultures and manipulations offer researchers opportunities to observe and study the development of feather buds directly. Skin explant culture can grow for 7 days enabling direct analysis of cellular behavior and 4D imaging at intervals during this growth period. This also allows for physical and molecular manipulations of culture conditions to visualize tissue response. For example, growth factor-coated beads can be applied locally to induce changes in feather patterning in a limited area. Alternatively, viral transduction can be delivered globally in the culture media to up or downregulate gene expression. Second, the skin recombination protocol allows researchers to investigate tissue interactions between the epidermis and mesenchyme that are derived from different skin regions, different life stages, or different species. This affords an opportunity to test the time window in which the epithelium is competent to respond to signals and its ability to form different skin appendages in response to signals from different mesenchymal sources. Third, skin reconstitution using dissociated dermal cells overlaid with intact epithelium resets skin development and enables the study of the initial processes of periodic patterning. This approach also enhances our ability to manipulate gene expression among the dissociated cells before creating the reconstituted skin explant. This paper provides the three culture protocols and exemplary experiments to demonstrate their utility.

Author Spotlight: Insight into the Current Experimental Avian Skin Explant Methodologies

Here we describe protocols for three types of avian embryonic skin explant cultures that can be used to examine tissue interactions, 4D imaging timelapse movie (3D plus time), global or local perturbation of molecular function, and systems biology characterization.

The developing avian skin during embryogenesis is a unique model that can provide valuable insights into tissue patterning. Here three variations on skin ...

Tracking Morphogenetic Tissue Deformations in the Early Chick Embryo 

Embryonic epithelia undergo complex deformations (e.g. bending, twisting, folding, and stretching) to form the primitive organs of the early embryo. Tracking fiducial markers on the surfaces of these cellular sheets is a well-established method for estimating morphogenetic quantities such as growth, contraction, and shear. However, not all surface labeling techniques are readily adaptable to conventional imaging modalities and possess different advantages and limitations. Here, we describe two labeling methods and illustrate the utility of each technique. In the first method, hundreds of fluorescent labels are applied simultaneously to the embryo using magnetic iron particles. These labels are then used to quantity 2-D tissue deformations during morphogenesis. In the second method, polystyrene microspheres are used as contrast agents in non-invasive optical coherence tomography (OCT) imaging to track 3-D tissue deformations. These techniques have been successfully implemented in our lab to studythe physical mechanisms of early head fold, heart, and brain development, and should be adaptable to a wide range morphogenetic processes.

Tracking Morphogenetic Tissue Deformations in the Early Chick Embryo

This article describes surface labeling and ex ovo tissue culture in the early chick embryo. Techniques amenable to time-lapse bright field, fluorescence, and optical coherence tomography imaging are presented. Tracking surface labels with high spatiotemporal resolution enables kinematic quantities such as morphogenetic strains (deformations) to be calculated in both two and three dimensions.

Embryonic epithelia undergo complex deformations (e.g. bending, twisting, folding, and stretching) to form the primitive organs of the early embryo. ...

Assessing Species-specific Contributions To Craniofacial Development Using Quail-duck Chimeras

The generation of chimeric embryos is a widespread and powerful approach to study cell fates, tissue interactions, and species-specific contributions to the histological and morphological development of vertebrate embryos. In particular, the use of chimeric embryos has established the importance of neural crest in directing the species-specific morphology of the craniofacial complex. The method described herein utilizes two avian species, duck and quail, with remarkably different craniofacial morphology. This method greatly facilitates the investigation of molecular and cellular regulation of species-specific pattern in the craniofacial complex.&#160;Experiments in quail and duck chimeric embryos have already revealed neural crest-mediated tissue interactions and cell-autonomous behaviors that regulate species-specific pattern in the craniofacial skeleton, musculature, and integument. The great diversity of neural crest derivatives suggests significant potential for future applications of the quail-duck chimeric system to understanding vertebrate development, disease, and evolution.

This article describes a method to generate chimeric embryos that are&#160;designed to test the species-specific contributions of neural crest and/or other tissues to craniofacial development.

The generation of chimeric embryos is a widespread and powerful approach to study cell fates, tissue interactions, and species-specific contributions to ...

Probing the Roles of Physical Forces in Early Chick Embryonic Morphogenesis

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