Name: in ovo and ex ovo methods to study avian inner ear development
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Description: Watch this Scientific Journal Video about In Ovo and Ex Ovo Methods to Study Avian Inner Ear Development at JoVE.com

We gratefully acknowledge support from NCBS, TIFR, Infosys-TIFR Leading Edge Research Grant, DST-SERB, and the Royal National Institute for the Deaf. We would like to thank Central Poultry Development Organization and Training Institute, Hesaraghatta, Bengaluru. We are grateful to CIFF and EM facility and lab support at NCBS. We thank Yoshiko Takahashi and Koichi Kawakami for the Tol2-eGFP and T2TP constructs, and Guy Richardson for HCA and G19 Pcdh15 antibody. We are grateful to Earlab members for their constant support and valuable feedback on the protocol.

Protocols involving the procurement, culture, and use of fertilized chicken eggs and unhatched embryos were approved by the Institutional Animal Ethics Committee of the National Centre for Biological Sciences, Bengaluru, Karnataka.
1. In ovo electroporation of chick auditory precursors
<ol>
	<li>sgRNA design and cloning for CRISPR/Cas9 gene knockout
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		<li>For creating gene knockouts, design guide RNAs to disrupt the exon regions of the gene, preferably closer ...

<ol>
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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Asymmetric+distribution+of+cadherin+23+and+protocadherin+15+in+the+kinocilial+links+of+avian+sensory+hair+cells.">Asymmetric distribution of cadherin 23 and protocadherin 15 in the kinocilial links of avian sensory hair cells.</a> The Journal of Comparative Neurology. 518 (21), 4288-4297 (2010).</li><li>Bartolami, S., Goodyear, R., Richardson, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Appearance+and+distribution+of+the+275+kD+hair-cell+antigen+during+development+of+the+avian+inner+ear.">Appearance and distribution of the 275 kD hair-cell antigen during development of the avian inner ear.</a> The Journal of Comparative Neurology. 314 (4), 777-788 (1991).</li><li>Funahashi, J., Nakamura, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroporation+in+avian+embryos.">Electroporation in avian embryos.</a> Methods in Molecular Biology. 461, 377-382 (2008).</li><li>Nakamura, H., Funahashi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroporation:+past,+present+and+future.">Electroporation: past, present and future.</a> Development, Growth &amp; Differentiation. 55 (1), 15-19 (2013).</li><li>Olaya-Sanchez, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fgf3+and+Fgf16+expression+patterns+define+spatial+and+temporal+domains+in+the+developing+chick+inner+ear.">Fgf3 and Fgf16 expression patterns define spatial and temporal domains in the developing chick inner ear.</a> Brain Structure &amp; Function. 222 (1), 131-149 (2017).</li><li>Jones, J. 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The chick is a cost-effective and convenient addition to the model organisms that a lab may use to research the inner ear. The methods described here are routinely used in our lab and complement ongoing research in the mammalian inner ear. In ovo electroporation is used to introduce genetic manipulations into the chick genome. Electroporation can also be used to introduce constructs that encode fluorescent proteins targeted to particular organelles or subcellular structures35,<...

The inner ear of all vertebrates is derived from a simple epithelium known as the otic placode1,2. This will give rise to all the structural elements and the cell types necessary to transduce the mechanosensory information associated with hearing and balance perception. Hair cells (HCs), the ciliated sensor of the inner ear, are surrounded by supporting cells (SCs). HCs relay information to the auditory hindbrain through the neurons of the eighth cranial nerve. These are also generated from the otic placode3. The primary transduction of sound is achieved at the apical surface of the auditory HC, through a mechanically sensitive hair bundle4. This is mediated through modified actin-based protrusions called stereocilia, which are arranged in a graded, staircase pattern5. In addition, a modified primary cilium, called the kinocilium, organizes hair bundle formation and is adjacent to the tallest row of stereocilia6,7,8. The architecture of stereocilia is critical for this role in converting mechanical stimuli derived from acoustic energy to electrical neural signals9. Damage to the auditory HC through ageing, infection, otoacoustic trauma, or ototoxic shock can result in partial or complete hearing loss that, in mammals, is irreversible10.
Cellular replacement therapies have been proposed that might repair such damage11,12. The approach of this research has been to understand the normal development of the mammalian hair cell and ask if development programs can be reinitiated in progenitor-like cells that may exist within the inner ear13. A second approach has been to look outside of mammals, to non-mammalian vertebrates in which robust regeneration of auditory hair cells takes place, such as birds14,15. In birds, hair cell regeneration occurs predominantly through the de-differentiation of a supporting cell to a progenitor-like state, followed by asymmetric&#160;mitotic division to generate a hair cell and supporting cell16. In addition, direct differentiation of a supporting cell to generate a hair cell has also been observed17.
While the mechanisms of avian auditory development do show significant similarities with that of mammals, there are differences18. HC and SC differentiation in the chick BP is apparent from embryonic day (E) 7, becoming more distinct over time. By E12, a well-patterned and well-polarized basilar papilla (BP) can be visualized, and by E17 well-developed hair cells can be seen19. These time points provide windows into the mechanisms of differentiation, patterning, and polarity, as well as hair cell maturation. Understanding whether such mechanisms are conserved or divergent is important, as they provide insights into the deep homology of the origins of mechanosensory hair cells.
Here, we demonstrate an array of techniques performed at early and late embryonic stages to study cellular processes such as proliferation, fate specification, differentiation, patterning, and maintenance throughout the development of the inner ear organ. This complements other protocols on understanding inner ear development in explant culture20,21,22. We first discuss the introduction of exogenous DNA or RNA into BP precursors within the E3.5 otocyst using in ovo electroporation. Although genetic manipulations can provide valuable insights, the phenotypes thus generated can be pleiotropic and consequently confounding. This is particularly true during later inner ear development, where fundamental processes such as cytoskeletal remodeling play multiple roles in cell division, tissue morphogenesis, and cellular specialization. We present protocols for pharmacological inhibition in cultured explants, which offer advantages in controlling dosage and treatment timing and duration, offering precise spatiotemporal manipulation of developmental mechanisms.
Different organ culture methods can be utilized depending on the treatment duration of small inhibitors. Here we demonstrate two methods of organ culture that allow insights into epithelial morphogenesis and cellular specialization. A method for 3D culture using collagen as a matrix to culture the cochlear duct enables robust culturing and live visualization of the developing BP. For understanding the formation of stereocilia, we present a membrane culture method such that epithelial tissue is cultured on a stiff matrix enabling actin protrusions to grow freely. Both methods allow downstream processing such as live-cell imaging, immunohistochemistry, scanning electron microscopy (SEM), cell recording, etc. These techniques provide a roadmap for the effective use of the chick as a model system to understand and manipulate the development, maturation, and regeneration of the avian auditory epithelium.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Alexa Fluor 488 Phalloidin</td>
			<td>Thermo Fisher Scientific</td>
			<td>A12379</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 647 Phalloidin</td>
			<td>Thermo Fisher Scientific</td>
			<td>A22287</td>
			<td></td>
		</tr>
		<tr>
			<td>Alt-R S.p. HiFi Cas9 Nuclease V3</td>
			<td>Integrated DNA Technologies</td>
			<td>1081061</td>
			<td>High fidelity Cas9 protein</td>
		</tr>
		<tr>
			<td>Anti-GFP antibody</td>
			<td>Abcam</td>
			<td>ab290</td>
			<td>Rabbit polyclonal to GFP</td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>Sigma-Aldrich</td>
			<td>A9647</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium Chloride Dihydrate</td>
			<td>Thermo Fisher Scientific</td>
			<td>Q12135</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagen I, rat tail</td>
			<td>Thermo Fisher Scientific</td>
			<td>A1048301</td>
			<td></td>
		</tr>
		<tr>
			<td>Critical Point Dryer Leica EM CPD300</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CUY-21 Electroporator</td>
			<td>Nepagene</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide (DMSO)</td>
			<td>Sigma-Aldrich</td>
			<td>D8418</td>
			<td></td>
		</tr>
		<tr>
			<td>DM5000B Widefield Microscope</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM, high glucose, GlutaMAX Supplement, pyruvate</td>
			<td>Thermo Fisher Scientific</td>
			<td>10569010</td>
			<td></td>
		</tr>
		<tr>
			<td>Dumont #5 Forceps</td>
			<td>Fine Science Tools</td>
			<td>11251-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Dumont #55 Forceps</td>
			<td>Fine Science Tools</td>
			<td>11255-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Fast Green FCF</td>
			<td>Sigma-Aldrich</td>
			<td>F7252</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluoroshield</td>
			<td>Sigma-Aldrich</td>
			<td>F6182</td>
			<td></td>
		</tr>
		<tr>
			<td>FLUOVIEW 3000 Laser Scanning Microscope</td>
			<td>Olympus</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glutaraldehyde (25 %)</td>
			<td>Sigma-Aldrich</td>
			<td>340855</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Mouse IgG Secondary Antibody, Alexa Fluor 488</td>
			<td>Thermo Fisher Scientific</td>
			<td>A-11001</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Mouse IgG Secondary Antibody, Alexa Fluor 594</td>
			<td>Thermo Fisher Scientific</td>
			<td>A-11032</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG Secondary Antibody, Alexa Fluor 488</td>
			<td>Thermo Fisher Scientific</td>
			<td>A-11008</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat Serum Sterile filtered</td>
			<td>HiMedia</td>
			<td>RM10701</td>
			<td>Heat inactivated</td>
		</tr>
		<tr>
			<td>Hanks&#39; Balanced Salt Solution (HBSS)</td>
			<td>Thermo Fisher Scientific</td>
			<td>14025092</td>
			<td></td>
		</tr>
		<tr>
			<td>LSM980 Airyscan Microscope</td>
			<td>Zeiss</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Millicell Cell Culture Insert, 30 mm, hydrophilic PTFE, 0.4 &#181;m</td>
			<td>Sigma-Aldrich</td>
			<td>PICM03050</td>
			<td></td>
		</tr>
		<tr>
			<td>MVX10 Stereo Microscope</td>
			<td>Olympus</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MYO7A antibody</td>
			<td>DSHB</td>
			<td>138-1</td>
			<td>Mouse monoclonal to Unconventional myosin-VIIa</td>
		</tr>
		<tr>
			<td>MZ16 Dissecting microscope</td>
			<td>Leica</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>N-2 Supplement (100X)</td>
			<td>Thermo Fisher Scientific</td>
			<td>17502048</td>
			<td></td>
		</tr>
		<tr>
			<td>Noyes Scissors, 14cm (5.5&#39;&#39;)</td>
			<td>World Precision Instruments</td>
			<td>501237</td>
			<td></td>
		</tr>
		<tr>
			<td>Osmium tetroxide (4%)</td>
			<td>Sigma-Aldrich</td>
			<td>75632</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>158127</td>
			<td></td>
		</tr>
		<tr>
			<td>PC-10 Puller</td>
			<td>Narishige</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pcU6_1sgRNA</td>
			<td>Addgene</td>
			<td>92395</td>
			<td>Mini vector with modified chicken U6 promoter</td>
		</tr>
		<tr>
			<td>Penicillin G sodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>P3032</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline (PBS)</td>
			<td>Thermo Fisher Scientific</td>
			<td>10010023</td>
			<td></td>
		</tr>
		<tr>
			<td>ProLong Gold Antifade Mountant</td>
			<td>Thermo Fisher Scientific</td>
			<td>P36934</td>
			<td></td>
		</tr>
		<tr>
			<td>SMZ1500 Dissecting microscope</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Cacodylate Buffer, 0.2M</td>
			<td>Electron Microscopy Sciences</td>
			<td>11652</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>HiMedia</td>
			<td>GRM853</td>
			<td></td>
		</tr>
		<tr>
			<td>Sputtre Coater K550X</td>
			<td>Emitech</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Standard Glass Capillaries 3 in, OD 1.0 mm, No Filament</td>
			<td>World Precision Instruments</td>
			<td>1B100-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma-Aldrich</td>
			<td>84097</td>
			<td></td>
		</tr>
		<tr>
			<td>The MERLIN Compact VP</td>
			<td>Zeiss</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Thiocarbohydrazide</td>
			<td>Alfa Aesar</td>
			<td>L01205</td>
			<td></td>
		</tr>
		<tr>
			<td>TWEEN 20</td>
			<td>Sigma-Aldrich</td>
			<td>P1379</td>
			<td></td>
		</tr>
	</tbody>
</table>

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 the electroporation setup, electrode positioning can play a role in the domain of transfection. The positive electrode is placed under the yolk, and the negative above the embryo (Figure 1A). This results in higher GFP expression in much of the inner ear and both vestibular organs (Figure 1B), and auditory basilar papilla (Figure 1C,D), confirming transfection.
In assessing the phenoty...

Watch this Scientific Journal Video about In Ovo and Ex Ovo Methods to Study Avian Inner Ear Development at JoVE.com

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.

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 ...

Research

JoVE Journal

Developmental Biology

Efficient Gene Transfer in Chick Retinas for Primary Cell Culture Studies: An Ex-ovo Electroporation Approach

Efficient Gene Transfer in Chick Retinas for Primary Cell Culture Studies: An Ex-ovo Electroporation Approach

The cone photoreceptor-enriched cultures derived from embryonic chick retinas have become an indispensable tool for researchers around the world studying ...

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

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 ...

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

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. ...

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

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 ...

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

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 ...

In Ovo Electroporation in the Chicken Auditory Brainstem

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 ...

Methods for the Study of Regeneration in Stentor

Methods for the Study of Regeneration in Stentor

Cells need to be able to regenerate their parts to recover from external perturbations. The unicellular ciliate Stentor coeruleus is an excellent model ...

Whole-Mount In Situ Hybridization in Zebrafish Embryos and Tube Formation Assay in iPSC-ECs to Study the Role of Endoglin in Vascular Development

Vascular development is determined by the sequential expression of specific genes, which can be studied by performing in situ hybridization assays in ...

Creating Avian Forebrain Chimeras to Assess Facial Development

The avian embryo has been used as a model system for more than a century and has led to fundamental understanding of vertebrate development. One of the ...

In Ovo Feeding of Commercial Broiler Eggs: An Accurate and Reproducible Method to Affect Muscle Development and Growth

In Ovo Feeding of Commercial Broiler Eggs: An Accurate and Reproducible Method to Affect Muscle Development and Growth

Within the past three decades, red meat and poultry scientists focused on developing strategies and technologies to manipulate muscle development during ...