This work was supported by the National Natural Science Foundation of China (31972547). We appreciate the copyediting by Jing Wang and the voiceover by Malik Donlic at Washington State University, USA.

All procedures involving the care and use of animals conformed to U.S. National Institute of Health guidelines (NIH Pub. No. 85-23, revised 1996) and the chicken embryo protocols were approved by the Laboratory Animal Management and Experimental Animal Ethics Committee of Yangzhou University, China (No.201803124).
1. Fertilized egg collection and preparation
NOTE: Unlike mammals, the chicken has millions of follicles in a single ovary, but only a few of these follicles are mature enough to ovulate. Each follicle contains one oocyte or germ cell. As soon as the follicle matures and releases its yolk, it is incorporated into the funnel of the fallopian tube.As the follicle enters the jugular abdomen of the oviduct, semen binds to the egg in the hen&#39;s body, and the calcium in the hen&#39;s body forms a shell that envelops the fertilized egg, forming a soft-shelled egg in the body. The calcium shell gradually thickens until the egg is produced.
<ol>
	<li>Collect fertilized eggs from a local vendor or institution, which can be stored at 16&#176;C for 1 week. 
	NOTE: The high storage temperature will help the embryo to develop, while the low temperature will decrease the embryo viability. The embryos will fail to develop if the storage time is too long.</li>
	<li>Scrub the eggshell softly and slowly with 75% ethanol before transferring the eggs to the incubator.</li>
	<li>Place the eggs sideways, neatly on a rack in an incubator at 37.8 &#176;C and 60% humidity. After 60 h of incubation (HH stage 17), embryos will develop visible blood vessels and the heart begins to beat15. 
	&#8203;NOTE: After 2 days of incubation, small primordial dots, the early stage of the heart, appear. This process is called cherrybeading. At ~2.5 days, heart and other body segments are formed with visible vessels.</li>
</ol>
2. Preparation before injection
<ol>
	<li>Prepare glass capillaries that will be used as needles. Before the injection, pull 90 mm glass capillaries with an outer diameter of 1 mm and an inner diameter of 0.6 mm using the puller. Break tips using forceps (the angle of glass capillary usually is 45&#176;) and sterilize the capillaries under UV light for 2 h.</li>
	<li>Prepare exogenous materials such as plasmids, packaged lentiviruses, and PGCs.
	<ol>
		<li>Gently mix the plasmid pEGFP-N1 (an enhanced GFP expressing plasmid, 1&#181;g/&#181;L) with liposome at a 1:3 ratio (m/v). Add water to obtain a final DNA concentration of 10 ng/&#181;L. Let the DNA mixture sit at 37 &#176;C for 20 min before injection.</li>
		<li>Thaw viruses on ice before injection. The titer of lentivirus used for injection should be over 5 x 106 Tu/mL.</li>
		<li>Dilute parental or modified gonad PGCs (E4.5, HH stage 24) to 2,000-5,000 cells/&#181;L. 
		&#8203;NOTE: Here we have shown the injection procedure using trypan blue.</li>
	</ol>
	</li>
</ol>
3. Windowing
<ol>
	<li>Before exposing the embryos, sterilize them by gently and softly wiping the surface of the eggshells with 75% alcohol using a cotton ball, ensuring to sterilize the blunt edge of the eggs thoroughly.</li>
	<li>After the sterilization, gently tap the blunt end with forceps to create a small window (0.5 cm x 0.5 cm) on the eggshell surface to expose the embryo. Remove the embryo membrane and then place the egg on the holder under the dissection microscope.</li>
</ol>
4. Injection
<ol>
	<li>Look for blood vessels under the microscope and adjust the focus of the dissection microscope to locate the embryo, and then find the blood vessel ready for injection.</li>
	<li>Fill the glass needle with the exogenous solution (plasmid, lentivirus, or PGCs) using a pipette slowly, avoiding air bubblesin the needle.</li>
	<li>Aim the needle with exogenous solution at the blood vessel, with the needle parallel to the blood vessel being injected.</li>
	<li>Gently insert the filled needle into the vessel and turn on the pump to eject the solution (usually the injected volume is ~1-5 &#181;L) under the microscope. The air pump pressure should be low enough to prevent the destruction of vessels, as the excessively high air pressure would damage blood vessels leading to highspeed flow.
	<ol>
		<li>Once the exogenous solution is injected into the vessel, ensure that the color of the vessel turns into the solution color and recovers to red in 2-5 s, indicating the exogenous solution is successfully delivered to the vessel. At this point the solution enters the artery, and with the beating of the heart is circulated back to the embryo through the artery, and then to the vein. 
		NOTE: There are two injection sites for vascular injection (Figure 1B): one is the head, where the exogenous solution is injected from the vein in the head of the embryo and into the heart through the blood flow, then circulates to the whole embryo with the heart beating (Figure 1B, Arrow 1). Another is through the dorsal aorta of embryo blood; the exogenous solution is injected and spreads to the whole embryo (Figure 1B. Arrow 2) with the beating of the embryonic heart.</li>
	</ol>
	</li>
	<li>After injection, remove the egg from the stereo microscope and drop 200 &#181;L of Penicillin solution inside the eggshell. Cut a 3 cm long piece of medical tape and seal the window. Gently scrape the tape with scissors to squeeze out any air bubbles and then cut another piece to seal the opening across.</li>
	<li>Label and place the injected egg back into the incubator and incubate until the required developmental stage or hatching.</li>
</ol>

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No conflicts of interest were declared.

The method of in ovo intravascular injection of chicken embryos is optimized for exogenous materials (vector, viral, or PGCs) to be transferred into the embryo. Based on this method, we constructed chicken embryo models with stable gene overexpression or interference (SpinZ, JUN, UBE2I, etc.)17,18,19. These well-established models prove the feasibility of this approach. Additionally, we not only transferred isolated PGC...

Chicken embryos have been widely used for centuries in developmental, immunological, pathological, and other biological applications1,2,3. They have many inherent advantages over other animal models in the study of toxicology and cell biology4. Chicken embryos are easily accessible and can be manipulated in vitro and directly observed at any developmental stage, which provides a handy embryo research model system.
In general, current chicken embryo delivery methods such as electrotransfection and subgerminal-cavity injection have limitations such as the requirement of specialist equipment and a designed program, and inefficiency due to the presence of yolk and albumen5,6,7. Here we show a simple and efficient handling method for delivering exogenous materials into chicken embryos. This can be a powerful tool used in the study of developmental biology. The injected materials spread to the whole embryo via blood circulation. During the early development of chicken embryos, the PGCs could migrate through blood, colonize the genital ridge, and then develop into gametes, which provide a valuable possible path to deliver exogenous materials8. Now, this method has been widely used in the study of gene function, embryo and developmental biology, and chimeric and transgenic chicken production9,10,11.
In ovo intravascular injection in chicken embryos is a well-established and commonly used method12,13,14. In this paper, we show a comprehensive description of this protocol including injection materials, sites, dosage, and representative results.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Fluorescence macro-microscope</td>
			<td>OLYMPUS</td>
			<td>MVX10</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass Capillaries</td>
			<td>Narishige</td>
			<td>G1</td>
			<td></td>
		</tr>
		<tr>
			<td>Lipofectamine 2000</td>
			<td>Invitrogen</td>
			<td>12566014</td>
			<td>liposome</td>
		</tr>
		<tr>
			<td>pEGFP-N1 vector</td>
			<td>Clontech</td>
			<td>#6085-1</td>
			<td></td>
		</tr>
		<tr>
			<td>PKH26 Red Fluorescent Cell Linker Kit&#160;</td>
			<td>Sigma</td>
			<td>PKH26GL</td>
			<td></td>
		</tr>
		<tr>
			<td>pLVX-EGFP lentivirus vector</td>
			<td>Addgene</td>
			<td>128652</td>
			<td></td>
		</tr>
		<tr>
			<td>Pneumatic Microinjector</td>
			<td>Narishige</td>
			<td>IM-11-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Puller</td>
			<td>Narishige</td>
			<td>PC-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan Blue Stain</td>
			<td>Gibco</td>
			<td>15250061</td>
			<td></td>
		</tr>
	</tbody>
</table>

in ovo intravascular injection in chicken embryos

As a classical model system of embryo biology, the chicken embryo has been used to investigate embryonic development and differentiation. Delivering exogenous materials into chicken embryos has a great advantage for studying gene function, transgenic breeding, and chimera preparation during embryonic development. Here we show the method of in ovo intravascular injection whereby exogenous materials such as plasmid vectors or modified primordial germ cells (PGCs) can be transferred into donor chicken embryos at early developmental stages. The results show that the intravascular injection through the dorsal aorta and head allows injected materials to diffuse into the whole embryo through the blood circulatory system. In the presented protocol, the efficacy of exogenous plasmid and lentiviral vector introduction, and the colonization of injected exogenous PGCs in the recipient gonad, were determined by observing fluorescence in the embryos. This article describes detailed procedures of this method, thereby providing an excellent approach to studying gene function, embryo and developmental biology, and gonad-chimeric chicken production. In conclusion, this article will allow researchers to perform in ovo intravascular injection of exogenous materials into chicken embryos with great success and reproducibility.

We show here the in ovo intravascular injection of chicken embryos. A schematic process of the intravascular injection is shown in Figure 1; in our study, we used various exogenous solutions to test and verify injection.
To better visualize the injected materials, Trypan Blue (0.4%) was injected as a tracer into the embryo. The tracer (blue) was observed to diffuse to the whole embryo via blood circulation by either dorsal aorta or head injection...

Watch this Scientific Journal Video about In Ovo Intravascular Injection in Chicken Embryos at JoVE.com

In Ovo Intravascular Injection in Chicken Embryos

The overall goal of this paper is to describe how to perform in ovo intracellular injection of exogenous materials into chicken embryos. This approach is very useful to study the developmental biology of chicken embryos.

In Ovo Intravascular Injection in Chicken Embryos

As a classical model system of embryo biology, the chicken embryo has been used to investigate embryonic development and differentiation. Delivering ...

in-ovo-intravascular-injection-in-chicken-embryos

Research

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Developmental Biology

5.5K Views.  Yangzhou University. The overall goal of this paper is to describe how to perform in ovo intracellular injection of exogenous materials into chicken embryos. This approach is very useful to study the developmental biology of chicken embryos.

Video: In Ovo Intravascular Injection in Chicken Embryos

Optimized Ex-ovo Culturing of Chick Embryos to Advanced Stages of Development

Research in anatomy, embryology, and developmental biology has largely relied on the use of model organisms. In order to study development in live embryos model organisms, such as the chicken, are often used. The chicken is an excellent model organism due to its low cost and minimal maintenance, however they present observational challenges because they are enclosed in an opaque eggshell. In order to properly view the embryo as it develops, the shell must be windowed or removed. Both windowing and ex ovo techniques have been developed to assist researchers in the study of embryonic development. However, each of the methods has limitations and challenges. Here, we present a simple, optimized ex ovo culture technique for chicken embryos that enables the observation of embryonic development from stage HH 19 into late stages of development (HH 40), when many organs have developed. This technique is easy to adopt in both undergraduate classes and more advanced research laboratories where embryo manipulations are conducted.

Optimized Ex-ovo Culturing of Chick Embryos to Advanced Stages of Development

Viewing and accessing the chicken embryo during development can be challenging. We have developed an ex ovo method that is simple, cost effective, and can easily be used in a classroom or research setting. This method provides access to the embryo into late stages of embryonic development (HH 40).

Research in anatomy, embryology, and developmental biology has largely relied on the use of model organisms. In order to study development in live embryos ...

Dual Labeling of Neural Crest Cells and Blood Vessels Within Chicken Embryos Using ChickGFP Neural Tube Grafting and Carbocyanine Dye DiI Injection

All developing organs need to be connected to both the nervous system (for sensory and motor control) as well as the vascular system (for gas exchange, fluid and nutrient supply). Consequently both the nervous and vascular systems develop alongside each other and share striking similarities in their branching architecture. Here we report embryonic manipulations that allow us to study the simultaneous development of neural crest-derived nervous tissue (in this case the enteric nervous system), and the vascular system. This is achieved by generating chicken chimeras via transplantation of discrete segments of the neural tube, and associated neural crest, combined with vascular DiI injection in the same embryo. Our method uses transgenic chickGFP embryos for intraspecies grafting, making the transplant technique more powerful than the classical quail-chick interspecies grafting protocol used with great effect since the 1970s. ChickGFP-chick intraspecies grafting facilitates imaging of transplanted cells and their projections in intact tissues, and eliminates any potential bias in cell development linked to species differences. This method takes full advantage of the ease of access of the avian embryo (compared with other vertebrate embryos) to study the co-development of the enteric nervous system and the vascular system.

Dual Labeling of Neural Crest Cells and Blood Vessels Within Chicken Embryos Using ChickGFP Neural Tube Grafting and Carbocyanine Dye DiI Injection

Here we report dual labeling of neural crest cells and blood vessels using chickGFP neural tube intraspecies grafting combined with intra-vascular DiI injection. This experimental technique allows us to simultaneously visualize and study development of the NCC-derived (enteric) nervous system and the vascular system, during organogenesis.

All developing organs need to be connected to both the nervous system (for sensory and motor control) as well as the vascular system (for gas exchange, ...

Whole Retinal Explants from Chicken Embryos for Electroporation and Chemical Reagent Treatments

The retina is a good model for the developing central nervous system. The large size of the eye and most importantly the accessibility for experimental manipulations in ovo/in vivo makes the chicken embryonic retina a versatile and very efficient experimental model. Although the chicken retina is easy to target in ovo by intraocular injections or electroporation, the effective and exact concentration of the reagents within the retina may be difficult to fully control. This may be due to variations of the exact injection site, leakage from the eye or uneven diffusion of the substances. Furthermore, the frequency of malformations and mortality after invasive manipulations such as electroporation is rather high.
This protocol describes an ex ovo technique for culturing whole retinal explants from chicken embryos and provides a method for controlled exposure of the retina to reagents. The protocol describes how to dissect, experimentally manipulate, and culture whole retinal explants from chicken embryos. The explants can be cultured for approximately 24 hr and be subjected to different manipulations such as electroporation. The major advantages are that the experiment is not dependent on the survival of the embryo and that the concentration of the introduced reagent can be varied and controlled in order to determine and optimize the effective concentration. Furthermore, the technique is rapid, cheap and together with its high experimental success rate, it ensures reproducible results. It should be emphasized that it serves as an excellent complement to experiments performed in ovo.

This protocol describes a method to dissect, experimentally manipulate and culture whole retinal explants from chicken embryos. The explant cultures are useful when high success rate, efficacy and reproducibility are needed to test the effects of plasmids for electroporation and/or reagent substances, i.e., enzymatic inhibitors.

The retina is a good model for the developing central nervous system. The large size of the eye and most importantly the accessibility for experimental ...

Gene Transfer into the Chicken Auditory Organ by In Ovo Micro-electroporation

Chicken embryos are ideal model systems for studying embryonic development as manipulations of gene function can be conducted with relative ease in ovo. The inner ear auditory sensory organ is critical for our ability to hear. It houses a highly specialized sensory epithelium that consists of mechano-transducing hair cells (HCs) and surrounding glial-like supporting cells (SCs). Despite structural differences in the auditory organs, molecular mechanisms regulating the development of the auditory organ are evolutionarily conserved between mammals and aves. In ovo electroporation is largely limited to early stages at E1 - E3. Due to the relative late development of the auditory organ at E5, manipulations of the auditory organ by in ovo electroporation past E3 are difficult due to the advanced development of the chicken embryo at later stages. The method presented here is a transient gene transfer method for targeting genes of interest at stage E4 - E4.5 in the developing chicken auditory sensory organ via in ovo micro-electroporation. This method is applicable for gain- and loss-of-functions with conventional plasmid DNA-based expression vectors and can be combined with in ovo cell proliferation assay by adding EdU (5-ethynyl-2&#180;-deoxyuridine) to the whole embryo at the time of electroporation. The use of green or red fluorescent protein (GFP or RFP) expression plasmids allows the experimenter to quickly determine whether the electroporation successfully targeted the auditory portion of the developing inner ear. In this method paper, representative examples of GFP electroporated specimens are illustrated; embryos were harvested 18 - 96 hr&#160;after electroporation and targeting of GFP to the pro-sensory area of the auditory organ was confirmed by RNA in situ hybridization. The method paper also provides an optimized protocol for the use of the thymidine analog EdU to analyze cell proliferation; an example of an EdU based cell proliferation assay that combines immuno-labeling and click EdU chemistry is provided.

Gene Transfer into the Chicken Auditory Organ by In Ovo Micro-electroporation

The auditory organ mediates hearing. Here we present a modified in ovo micro-electroporation method optimized for studying auditory progenitor cell proliferation and differentiation in the developing chicken auditory organ.

Chicken embryos are ideal model systems for studying embryonic development as manipulations of gene function can be conducted with relative ease in ovo. ...

A Novel Ex Ovo Banding Technique to Alter Intracardiac Hemodynamics in an Embryonic Chicken System

The new model presented here can be used to understand the influence of hemodynamics on specific cardiac developmental processes, at the cellular and molecular level. To alter intracardiac hemodynamics, fertilized chicken eggs are incubated in a humidified chamber to obtain embryos of the desired stage (HH17). Once this developmental stage is achieved, the embryo is maintained ex ovo and hemodynamics in the embryonic heart are altered by partially constricting the outflow tract (OFT) with a surgical suture at the junction of the OFT and ventricle (OVJ). Control embryos are also cultured ex ovo but are not subjected to the surgical intervention. Banded and control embryos are then incubated in a humidified incubator for the desired period of time, after which 2D ultrasound is employed to analyze the change in blood flow velocity at the OVJ as a result of OFT banding. Once embryos are maintained ex ovo, it is important to ensure adequate hydration in the incubation chamber so as to prevent drying and eventually embryo death. Using this new banded model, it is now possible to perform analyses of changes in the expression of key players involved in valve development and to understand the role of hemodynamics on cellular responses in vivo, which could not be achieved previously.

A Novel Ex Ovo Banding Technique to Alter Intracardiac Hemodynamics in an Embryonic Chicken System

For the first time we present here a reproducible banding procedure to alter hemodynamics in the developing heart ex ovo. This is achieved by partially constricting the outflow tract (OFT).

The new model presented here can be used to understand the influence of hemodynamics on specific cardiac developmental processes, at the cellular and ...

A Submerged Filter Paper Sandwich for Long-term Ex Ovo Time-lapse Imaging of Early Chick Embryos

Due to its availability, low cost, flat geometry, and transparency, the ex ovo chick embryo has become a major vertebrate animal model for the study of morphogenetic events, such as gastrulation2, neurulation3-5, somitogenesis6, heart bending7,8, and brain formation9-13, during early embryogenesis. Key to understanding morphogenetic processes is to follow them dynamically by time-lapse imaging. The acquisition of time-lapse movies of chick embryogenesis ex ovo has been limited either to short time windows or to the need for an incubator to control temperature and humidity around the embryo14. Here, we present a new technique to culture chick embryos ex ovo for high-resolution time-lapse imaging using transmitted light microscopy. The submerged filter paper sandwich is a variant of the well-established filter paper carrier technique (EC-culture)1 and allows for the culturing of chick embryos without the need for a climate chamber. The embryo is sandwiched between two identical filter paper carriers and is kept fully submerged in a simple, temperature-controlled medium covered by a layer of light mineral oil. Starting from the primitive streak stage (Hamburger-Hamilton stage 5, HH5)15 up to at least the 28-somite stage (HH16)15, embryos can be cultured with either their ventral or dorsal side up. This allows the acquisition of time-lapse movies covering about 30 hr of embryonic development. Representative time-lapse frames and movies are shown. Embryos are compared morphologically to an embryo cultured in the standard EC-culture.
The submerged filter paper sandwich provides a stable environment to study early dorsal and ventral morphogenetic processes. It also allows for live fluorescence imaging and micromanipulations, such as microsurgery, bead implantation, microinjection, gene silencing, and electroporation, and has a strong potential to be combined with immersion objectives for laser-based imaging (including light-sheet microscopy).

A Submerged Filter Paper Sandwich for Long-term Ex Ovo Time-lapse Imaging of Early Chick Embryos

Here, we present a new technique to culture chick embryos ex ovo for time-lapse imaging using transmitted light and fluorescence microscopy. The submerged filter paper sandwich is a variant of the well-established filter paper carrier technique1 that allows for the culturing of chick embryos fully-submerged in a liquid culture medium.

Due to its availability, low cost, flat geometry, and transparency, the ex ovo chick embryo has become a major vertebrate animal model for the study of ...

Biosensing Motor Neuron Membrane Potential in Live Zebrafish Embryos

The protocols described here are designed to allow researchers to study cell communication without altering the integrity of the environment in which the cells are located. Specifically, they have been developed to analyze the electrical activity of excitable cells, such as spinal neurons. In such a scenario, it is crucial to preserve the integrity of the spinal cell, but it is also important to preserve the anatomy and physiological shape of the systems involved. Indeed, the comprehension of the manner in which the nervous system-and other complex systems-works must be based on a systemic approach. For this reason, the live zebrafish embryo was chosen as a model system, and the spinal neuron membrane voltage changes were evaluated without interfering with the physiological conditions of the embryos. 
Here, an approach combining the employment of zebrafish embryos with a FRET-based biosensor is described. Zebrafish embryos are characterized by a very simplified nervous system and are particularly suited for imaging applications thanks to their transparency, allowing for the employment of fluorescence-based voltage indicators at the plasma membrane during zebrafish development. The synergy between these two components makes it possible to analyze the electrical activity of the cells in intact living organisms, without perturbing the physiological state. Finally, this non-invasive approach can co-exist with other analyses (e.g., spontaneous movement recordings, as shown here).

Protocols described here allow for the study of the electrical properties of excitable cells in the most non-invasive physiological conditions by employing zebrafish embryos in an in vivo system together with a fluorescence resonance energy transfer (FRET)-based genetically encoded voltage indicator (GEVI) selectively expressed in the cell type of interest.

The protocols described here are designed to allow researchers to study cell communication without altering the integrity of the environment in which the ...

In Ovo Electroporation in the Chicken Auditory Brainstem

Electroporation is a method that introduces genes of interest into biologically relevant organisms like the chicken embryo. It is long established that the chicken embryo is an effective research model for studying basic biological functions of auditory system development. More recently, the chicken embryo has become particularly valuable in studying gene expression, regulation and function associated with hearing. In ovo electroporation can be used to target auditory brainstem regions responsible for highly specialized auditory functions. These regions include the chicken nucleus magnocellularis (NM) and nucleus laminaris (NL). NM and NL neurons arise from distinct precursors of rhombomeres 5 and 6 (R5/R6). Here, we present in ovo electroporation of plasmid-encoded genes to study gene-related properties in these regions. We show a method for spatial and temporal control of gene expression that promote either gain or loss of functional phenotypes. By targeting auditory neural progenitor regions associated with R5/R6, we show plasmid transfection in NM and NL. Temporal regulation of gene expression can be achieved by adopting a tet-on vector system. This is a drug inducible procedure that expresses the genes of interest in the presence of doxycycline (Dox). The in ovo electroporation technique &#8211; together with either biochemical, pharmacological, and or in vivo functional assays &#8211; provides an innovative approach to study auditory neuron development and associated pathophysiological phenomena.

In Ovo Electroporation in the Chicken Auditory Brainstem

Auditory brainstem neurons of avians and mammals are specialized for fast neural encoding, a fundamental process for normal hearing functions. These neurons arise from distinct precursors of embryonic hindbrain. We present techniques utilizing electroporation to express genes in the hindbrain of chicken embryos to study gene function during auditory development.

Electroporation is a method that introduces genes of interest into biologically relevant organisms like the chicken embryo. It is long established that ...

Visualizing the Node and Notochordal Plate In Gastrulating Mouse Embryos Using Scanning Electron Microscopy and Whole Mount Immunofluorescence

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is the formation of the transient organizers, the node and notochordal plate, from cells that have passed through the primitive streak. The proper formation of these signaling centers is essential for the development of the body plan and techniques to visualize them are of high interest to mouse developmental biologists. The node and notochordal plate lie on the ventral surface of gastrulating mouse embryos around embryonic day (E) 7.5 of development. The node is a cup-shaped structure whose cells possess a single slender cilium each. The proper subcellular localization and rotation of the cilia in the node pit determines left-right asymmetry. The notochordal plate cells also possess single cilia albeit shorter than those of the node cells. The notochordal plate forms the notochord which acts as an important signaling organizer for somitogenesis and neural patterning. Because the cells of the node and notochordal plate are transiently present on the surface and possess cilia, they can be visualized using scanning electron microscopy (SEM). Among other techniques used to visualize these structures at the cellular level is whole mount immunofluorescence (WMIF) using the antibodies against the proteins that are highly expressed in the node and notochordal plate. In this report, we describe our optimized protocols to perform SEM and WMIF of the node and notochordal plate in developing mouse embryos to help in the assessment of tissue shape and cellular organization in wild-type and gastrulation mutant embryos.

The node and notochordal plate are transient signaling organizers in developing mouse embryos that can be visualized using several techniques. Here, we describe in detail how to perform two of the techniques to study their structure and morphogenesis: 1) scanning electron microscopy (SEM); and 2) whole mount immunofluorescence (WMIF).

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is ...

In Ovo and Ex Ovo Methods to Study Avian Inner Ear Development

The inner ear perceives sound and maintains balance using the cochlea and vestibule. It does this by using a dedicated mechanosensory cell type known as the hair cell. Basic research in the inner ear has led to a deep understanding of how the hair cell functions, and how dysregulation can lead to hearing loss and vertigo. For this research, the mouse has been the pre-eminent model system. However, mice, like all mammals, have lost the ability to replace hair cells. Thus, when trying to understand cellular therapies for restoring inner ear function, complementary studies in other vertebrate species could provide further insights. The auditory epithelium of birds, the basilar papilla (BP), is a sheet of epithelium composed of mechanosensory hair cells (HCs) intercalated by supporting cells (SCs). Although the anatomical architecture of the basilar papilla and the mammalian cochlea differ, the molecular mechanisms of inner ear development and hearing are similar. This makes the basilar papilla a useful system for not only comparative studies but also to understand regeneration. Here, we describe dissection and manipulation techniques for the chicken inner ear. The technique shows genetic and small molecule inhibition methods, which offer a potent tool for studying the molecular mechanisms of inner ear development. In this paper, we discuss in ovo electroporation techniques to genetically perturb the basilar papilla using CRIPSR-Cas9 deletions, followed by dissection of the basilar papilla. We also demonstrate the BP organ culture and optimal use of culture matrices, to observe the development of the epithelium and the hair cells.

In Ovo and Ex Ovo Methods to Study Avian Inner Ear Development

The chick is a cost-effective, accessible, and widely available model organism for a variety of studies. Here, a series of protocols is detailed to understand the molecular mechanisms underlying avian inner ear development and regeneration.

The inner ear perceives sound and maintains balance using the cochlea and vestibule. It does this by using a dedicated mechanosensory cell type known as ...