This work was supported by the National Institutes of Health (NIH) Grants: RO1 EY012085 (to J.X.J) and F32DK134051 (to F.M.A), and Welch Foundation grant: AQ-1507 (to J.X.J.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The figures were partially created with Biorender.com.

This study was conducted in compliance with the Animal Welfare Act and the Implementing Animal Welfare Regulations in accordance with the principles of the Guide for the Care and Use of Laboratory Animals. All animal procedures were approved by the Institutional Animal Care and Use Committee at the University of Texas Health Science Center at San Antonio. For an overview of the protocol, see Figure 1; see the Table of Materials for details on all materials, reagents, and ins...

Studying Protein Expression During Chicken Lens Development

<ol>
	<li>Li, Z., Gu, S., Quan, Y., Varadaraj, K., Jiang, J. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+potent+embryonic+chick+lens+model+for+studying+congenital+cataracts+in+vivo.">Development of a potent embryonic chick lens model for studying congenital cataracts in vivo.</a> Communications Biology. 4 (1), 325 (2021).</li><li>Chen, Y., 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=&#947;-Crystallins+of+the+chicken+lens:+remnants+of+an+ancient+vertebrate+gene+family+in+birds.">&#947;-Crystallins of the chicken lens: remnants of an ancient vertebrate gene family in birds.</a> The FEBS Journal. 283 (8), 1516-1530 (2016).</li><li>Coulombre, A. J., Coulombre, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lens+development.+I.+Role+of+the+lens+in+eye+growth.">Lens development. I. Role of the lens in eye growth.</a> Journal of Experimental Zoology. 156 (1), 39-47 (1964).</li><li>McKeehan, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+portions+of+the+chick+lens+without+contact+with+the+optic+cup.">Induction of portions of the chick lens without contact with the optic cup.</a> The Anatomical Record. 132 (3), 297-305 (1958).</li><li>Kothlow, S., Schenk-Weibhauser, K., Ratcliffe, M. J., Kaspers, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prolonged+effect+of+BAFF+on+chicken+B+cell+development+revealed+by+RCAS+retroviral+gene+transfer+in+vivo.">Prolonged effect of BAFF on chicken B cell development revealed by RCAS retroviral gene transfer in vivo.</a> Molecular immunology. 47 (7-8), 1619-1628 (2010).</li><li>Fekete, D. M., Cepko, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Replication-competent+retroviral+vectors+encoding+alkaline+phosphatase+reveal+spatial+restriction+of+viral+gene+expression/transduction+in+the+chick+embryo.">Replication-competent retroviral vectors encoding alkaline phosphatase reveal spatial restriction of viral gene expression/transduction in the chick embryo.</a> Molecular and Cellular Biology. 13 (4), 2604-2613 (1993).</li><li>Jiang, J. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+retroviruses+to+express+connexins.">Use of retroviruses to express connexins.</a> Methods in Molecular Biology. , 159-174 (2001).</li><li>Jiang, J. X., Goodenough, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retroviral+expression+of+connexins+in+embryonic+chick+lens.">Retroviral expression of connexins in embryonic chick lens.</a> Investigative Ophthalmology &amp; Visual Science. 39 (3), 537-543 (1998).</li><li>Shestopalov, V. I., Bassnett, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+autofluorescent+proteins+reveals+a+novel+protein+permeable+pathway+between+cells+in+the+lens+core.">Expression of autofluorescent proteins reveals a novel protein permeable pathway between cells in the lens core.</a> Journal of Cell Science. 113 (11), 1913-1921 (2000).</li><li>Liu, J., Xu, J., Gu, S., Nicholson, B. J., Jiang, J. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aquaporin+0+enhances+gap+junction+coupling+via+its+cell+adhesion+function+and+interaction+with+connexin+50.">Aquaporin 0 enhances gap junction coupling via its cell adhesion function and interaction with connexin 50.</a> Journal of Cell Science. 124 (2), 198-206 (2011).</li><li>Li, Z., 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=The+second+extracellular+domain+of+connexin+50+is+important+for+in+cell+adhesion,+lens+differentiation,+and+adhesion+molecule+expression.">The second extracellular domain of connexin 50 is important for in cell adhesion, lens differentiation, and adhesion molecule expression.</a> Journal of Biological Chemistry. 299 (3), 102965 (2023).</li><li>Shestopalov, V. I., Bassnett, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exogenous+gene+expression+and+protein+targeting+in+lens+fiber+cells.">Exogenous gene expression and protein targeting in lens fiber cells.</a> Investigative Ophthalmology &amp; Visual Science. 40 (7), 1435-1443 (1999).</li><li>Shestopalov, V. I., Bassnett, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+organization+of+primary+lens+fiber+cells.">Three-dimensional organization of primary lens fiber cells.</a> Investigative Ophthalmology &amp; Visual Science. 41 (3), 859-863 (2000).</li><li>Hughes, S. H., Greenhouse, J. J., Petropoulos, C. J., Sutrave, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptor+plasmids+simplify+the+insertion+of+foreign+DNA+into+helper-independent+retroviral+vectors.">Adaptor plasmids simplify the insertion of foreign DNA into helper-independent retroviral vectors.</a> Journal of Virology. 61 (10), 3004-3012 (1987).</li><li>Yan, R. T., Wang, S. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+of+high-titer+RCAS+retrovirus.">Production of high-titer RCAS retrovirus.</a> Methods in Molecular Biology. 884, 193-199 (2012).</li><li>Kingston, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Introduction+of+DNA+into+mammalian+cells.">Introduction of DNA into mammalian cells.</a> Current Protocols in Molecular Biology. 64 (1), 1-95 (2003).</li><li>Li, Y., 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=Studying+macrophage+activation+in+immune-privileged+lens+through+CSF-1+protein+intravitreal+injection+in+mouse+model.">Studying macrophage activation in immune-privileged lens through CSF-1 protein intravitreal injection in mouse model.</a> STAR Protocols. 3 (1), 101060 (2022).</li><li>Hamburger, V., Hamilton, H. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+series+of+normal+stages+in+the+development+of+the+chick+embryo.">A series of normal stages in the development of the chick embryo.</a> Developmental Dynamics. 195 (4), 231-272 (1992).</li><li>Hallagan, J. B., Allen, D. C., Borzelleca, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+safety+and+regulatory+status+of+food,+drug+and+cosmetics+colour+additives+exempt+from+certification.">The safety and regulatory status of food, drug and cosmetics colour additives exempt from certification.</a> Food and Chemical Toxicology. 33 (6), 515-528 (1995).</li><li>Okada, T. S., Eguchi, G., Takeichi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+expression+of+differentiation+by+chicken+lens+epithelium+in+in+vitro+cell+culture.">The expression of differentiation by chicken lens epithelium in in vitro cell culture.</a> Development, Growth &amp; Differentiation. 13 (4), 323-336 (1971).</li><li>Menko, A. S., Klukas, K. A., Johnson, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chicken+embryo+lens+cultures+mimic+differentiation+in+the+lens.">Chicken embryo lens cultures mimic differentiation in the lens.</a> Developmental Biology. 103 (1), 129-141 (1984).</li><li>Parreno, J., 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=Methodologies+to+unlock+the+molecular+expression+and+cellular+structure+of+ocular+lens+epithelial+cells.">Methodologies to unlock the molecular expression and cellular structure of ocular lens epithelial cells.</a> Frontiers in Cell and Developmental Biology. 10, 983178 (2022).</li><li>Edwards, A., Gupta, J. D., Harley, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photomicrographic+evaluation+of+drug-induced+cataracts+in+cultured+embryonic+chick+lens.">Photomicrographic evaluation of drug-induced cataracts in cultured embryonic chick lens.</a> Experimental Eye Research. 15 (4), 495-498 (1973).</li><li>Musil, L. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Primary+cultures+of+embryonic+chick+lens+cells+as+a+model+system+to+study+lens+gap+junctions+and+fiber+cell+differentiation.">Primary cultures of embryonic chick lens cells as a model system to study lens gap junctions and fiber cell differentiation.</a> Journal of Membrane Biology. 245 (7), 357-368 (2012).</li><li>West-Mays, J. A., Pino, G., Lovicu, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+use+of+the+lens+epithelial+explant+system+to+study+lens+differentiation+and+cataractogenesis.">Development and use of the lens epithelial explant system to study lens differentiation and cataractogenesis.</a> Progress in Retinal and Eye Research. 29 (2), 135-143 (2010).</li><li>Upreti, A., 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=Lens+epithelial+explants+treated+with+vitreous+humor+undergo+alterations+in+chromatin+landscape+with+concurrent+activation+of+genes+associated+with+fiber+cell+differentiation+and+innate+immune+response.">Lens epithelial explants treated with vitreous humor undergo alterations in chromatin landscape with concurrent activation of genes associated with fiber cell differentiation and innate immune response.</a> Cells. 12 (3), 501 (2023).</li><li>Walker, J. L., Wolff, I. M., Zhang, L., Menko, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+SRC+kinases+signals+induction+of+posterior+capsule+opacification.">Activation of SRC kinases signals induction of posterior capsule opacification.</a> Investigative Ophthalmology &amp; Visual Science. 48 (5), 2214-2223 (2007).</li><li>Briskin, M. J., 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=Heritable+retroviral+transgenes+are+highly+expressed+in+chickens.">Heritable retroviral transgenes are highly expressed in chickens.</a> Proceedings of the National Academy of Sciences of the United States of America. 88 (5), 1736-1740 (1991).</li><li>Hughes, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+RCAS+vector+system.">The RCAS vector system.</a> Folia Biologica. 50 (3-4), 107-119 (2004).</li></ol>

This experimental model offers the opportunity to express the protein(s) of interest in the intact lens leading to the study of the functional relevance of these proteins in lens structure and function. The embryonic chick microinjection model is based partially on the work of Fekete et. al.6 and was further developed by Jiang et. al.8 and has been utilized as a means of inserting both viral plasmids and agents such as agonists, small interfering RNA (siRNA), and peptides i...

The goal of this protocol is to describe the methodology of embryonic chicken lens microinjection of an RCAS(A) (replication-competent avian sarcoma/leukosis retrovirus A). Effective retroviral delivery in an embryonic chicken lens has been demonstrated to be a promising tool for the in vivo study of the molecular mechanism and structure-function of lens proteins in normal lens physiology, pathological conditions, and development. Moreover, this experimental model could be used for the identification of therapeutic targets and drug screening for conditions such as human congenital cataracts. In all, this protocol aims to lay out the necessary steps for the development of a customizable platform for the study of lens proteins.
Embryonic chicks (Gallus domesticus), owing to their similarity in lens structure and function with the human lens, are a well-established animal model for the study of lens development and physiology1,2,3,4. The use of an RCAS(A) replication-competent avian retrovirus has been regarded as a highly effective, rapid, and customizable system to express exogenous proteins in chick embryos. Notably, it has a unique ability to confine the target gene transfer to proliferative lens fiber cells without the need for tissue-specific promoters, using the unique embryonic development time frame in which the presence of empty lens lumen permits in situ RCAS(A) microinjection into the restricted site for the expression of exogenous proteins within proliferative lens fiber cells5,6,7,8.
The chick embryo microinjection procedure, described in-depth here, is based originally partially on the work of Fekete et. al.6 and further developed by Jiang et. al.8 and has been utilized as a means of introducing both viral and nonviral plasmids into the lens of embryonic chicks1,9,10,11,12,13. Overall, the previous work demonstrates the potential of utilizing this methodology to study lens development, differentiation, cellular communication, and disease progression, and for the discovery and testing of therapeutic targets for lens pathological conditions such as cataracts.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.22 &#181;m Filter</td>
			<td>Corning</td>
			<td>431118</td>
			<td>For removing cellular debris from media</td>
		</tr>
		<tr>
			<td>35 mm x 10 mm Culture Dish</td>
			<td>FisherScientific</td>
			<td>50-202-030</td>
			<td>For using during microinjection</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Fisherbrand</td>
			<td>13-100-676</td>
			<td>Spinning down solution</td>
		</tr>
		<tr>
			<td>Constructs</td>
			<td>GENEWIZ</td>
			<td>-</td>
			<td>For generation of constructs</td>
		</tr>
		<tr>
			<td>Dissecting microscope</td>
			<td>AmScope</td>
			<td>SM-4TZ-144A</td>
			<td>Visualization of lens for microinjection</td>
		</tr>
		<tr>
			<td>DNA PCR primers</td>
			<td>Integrated DNA Technologies</td>
			<td>-</td>
			<td>Generation of primers: 
			 
			Intracellular loop (IL)-deleted Cx50 (residues 1&#8211;97 and 149&#8211;400) as well as the Cla12NCO vector were obtained with the following pair of primers: sense, CTCCTGAGAACCTACATCCT; antisense, CACCGCATGCCCAAAGTACAC 
			 
			ILs of Cx43 (residues 98&#8211;150) and Cx46 (residues 98&#8211;166) were&#160; obtained with the following pairs of primers: sense, TACGTGATGAGGAAAGAAGAG; antisense, TCCTCCACGCATCTTTACCTTG; sense, CACATTGTACGCATGGAAGAG; antisense, AGCACCTCCC AT ACGGATTC, respectively 
			 
			Cla12NCO-Cx43 construct template was obtained with the following pair of primers: sense, CTGCTTCGTACTTACATCATC; antisense, GAACAC GTGCGCCAGGTAC 
			 
			ILs of Cx50 (residues 98&#8211;148) or Cx46 (residues 98&#8211;166) were cloned by using Cla12NCO-Cx50 and Cla12NCO-Cx46 constructs as the templates with the following pair of primers: sense, CACCATGTCCGCATGGAGGAGA; antisense, GGTCCCC TC CAGGCGAAAC; sense, CACATTGTACGCATGGAAGAG; antisense, AGCACCTCCCATACGGATTC, respectively</td>
		</tr>
		<tr>
			<td>Drummond Nanoject II Automatic Nanoliter Injector</td>
			<td>Drummond Scientific</td>
			<td>3-000-204</td>
			<td>Microinjection Pipet</td>
		</tr>
		<tr>
			<td>Dual Gooseneck Lights Microscope Illuminator</td>
			<td>AmScope</td>
			<td>LED-50WY</td>
			<td>Lighting for visualization</td>
		</tr>
		<tr>
			<td>Dulbecco&#8217;s Modified Eagle Medium (DMEM)</td>
			<td>Invitrogen</td>
			<td></td>
			<td>For cell culture</td>
		</tr>
		<tr>
			<td>Egg Holder</td>
			<td>-</td>
			<td>-</td>
			<td>Homemade styrofoam rings with 2-inch diameter and one-half inch height</td>
		</tr>
		<tr>
			<td>Egg Incubator</td>
			<td>GQF Manufacturing Company Inc.</td>
			<td>1502</td>
			<td>For incubation of fertilized eggs</td>
		</tr>
		<tr>
			<td>Fast Green</td>
			<td>Fisher scientific</td>
			<td>F99-10</td>
			<td>For visualization of viral stock injection</td>
		</tr>
		<tr>
			<td>Fertilized white leghorn chicken eggs</td>
			<td>Texas A&#38;M University</td>
			<td>N/A</td>
			<td>Animal model of choice for microinjection (https://posc.tamu.edu/fertile-egg-orders/)</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Hyclone Laboratories</td>
			<td></td>
			<td>For cell culture</td>
		</tr>
		<tr>
			<td>Fluorescein-conjugated anti-mouse IgG</td>
			<td>Jackson ImmunoResearch</td>
			<td>115-095-003</td>
			<td>For anti-FLAG&#160; 1:500</td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>FisherScientific</td>
			<td>22-327379</td>
			<td>For moving things around and isolation</td>
		</tr>
		<tr>
			<td>Glass capillaries</td>
			<td>Sutter Instruments</td>
			<td>B100-75-10</td>
			<td>Glass micropipette for microinjection (O.D. 1.0 mm, I.D. 0.75 mm, 10 cm length)</td>
		</tr>
		<tr>
			<td>Lipofectamine</td>
			<td>Invitrogen</td>
			<td>L3000001</td>
			<td>For transfection</td>
		</tr>
		<tr>
			<td>Manual vertical micropipette puller</td>
			<td>Sutter Instruments</td>
			<td>P-30</td>
			<td>To obtain glass micropipette of the correct size</td>
		</tr>
		<tr>
			<td>Microcentrifuge Tubes</td>
			<td>FisherScientific</td>
			<td>02-682-004</td>
			<td>Dissolving solution</td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Keyence</td>
			<td>BZ-X710</td>
			<td>For imaging staining</td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>FisherScientific</td>
			<td>03-448-254</td>
			<td>Placing solution</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Invitrogen</td>
			<td></td>
			<td>For cell culture</td>
		</tr>
		<tr>
			<td>Pico-Injector</td>
			<td>Harvard Apparatus</td>
			<td>PLI-100</td>
			<td>For delivering small liquid volumes precisely through micropipettes by applying a regulated pressure for a digitally set period of time</td>
		</tr>
		<tr>
			<td>rabbit anti-chick AQP0</td>
			<td>Self generated</td>
			<td>-</td>
			<td>Jiang JX, White TW, Goodenough DA, Paul DL. Molecular cloning and functional characterization of chick lens fiber connexin 45.6. Mol Biol Cell. 1994 Mar;5(3):363-73. doi: 10.1091/mbc.5.3.363.</td>
		</tr>
		<tr>
			<td>rabbit anti-FLAG antibody</td>
			<td>Rockland Immunichemicals</td>
			<td>600-401-383</td>
			<td>For staining FLAG</td>
		</tr>
		<tr>
			<td>Rhodamine-conjugated anti-rabbit IgG&#160;</td>
			<td>Jackson ImmunoResearch</td>
			<td>111-295-003</td>
			<td>For anti-AQP0&#160; 1:500</td>
		</tr>
		<tr>
			<td>Sponge clamping pad</td>
			<td>Sutter Instruments</td>
			<td>BX10</td>
			<td>For storage of glass micropipette</td>
		</tr>
	</tbody>
</table>

microinjection of recombinant rcas(a) retrovirus into embryonic chicken lens

Embryonic chicken (Gallus domesticus) is a well-established animal model for the study of lens development and physiology, given its high degree of similarity with the human lens. RCAS(A) is a replication-competent chicken retrovirus that infects dividing cells, which serves as a powerful tool to study the in situ expression and function of wild-type and mutant proteins during lens development by microinjection into the empty lumen of lens vesicle at early developmental stages, restricting its action to surrounding proliferating lens cells. Compared to other approaches, such as transgenic models and ex vivo cultures, the use of an RCAS(A) replication-competent avian retrovirus provides a highly effective, rapid, and customizable system to express exogenous proteins in chick embryos. Specifically, targeted gene transfer can be confined to proliferative lens fiber cells without the need for tissue-specific promoters. In this article, we will briefly overview the steps needed for recombinant retrovirus RCAS(A) preparation, provide a detailed, comprehensive overview of the microinjection procedure, and provide sample results of the technique.

Author Spotlight: Investigating Lens Development and Function Through Microinjection of RCAS(A) Retrovirus in Embryonic Chicken Lens 

Microinjection of Recombinant RCAS(A) Retrovirus into Embryonic Chicken Lens

The presented methodology of embryonic chicken lens microinjection of a RCAS retrovirus is meant as a tool for studying in situ function and expression of proteins during lens development. Compared to other approaches, such as transgenic models and ex vivo cultures, the RCAS replication-competent avian retrovirus provides a highly-effective, rapid, and customizable system for expressing exogenous proteins in chick embryos. Targeted gene transfer can be confined to proliferative lens fiber cells without the need for promoters.There is prominent potential for utilizing this methodology to study lens development, differentiation, cellular communication, and disease progression, and for the discovery and testing of therapeutic targets for lens pathological conditions such as cataracts.

After the determination of a specific target protein(s) and the identification of the associated gene sequence(s), the overall experimental approach involves the cloning of the gene sequence(s) into a retroviral RCAS(A) vector by the initial cloning into an adaptor vector, followed by a viral vector. Second, high-titer viral particles are prepared using packaging cells to harvest and concentrate the virions. These first two major steps have been largely described and representative results presented elsewhere<sup class="...

Watch this Scientific Journal Video about Investigating Lens Development and Function Through Microinjection of RCASA Retrovirus in Embryonic Chicken Lens at JoVE.com

This protocol paper describes the methodology of embryonic chicken lens microinjection of an RCAS(A) retrovirus as a tool for studying in situ function and expression of proteins during lens development.

Embryonic chicken (Gallus domesticus) is a well-established animal model for the study of lens development and physiology, given its high degree of ...

microinjection-recombinant-rcasa-retrovirus-into-embryonic-chicken

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Biology

Preparation of Chicken Lens for Microinjection of an RCAS(A) Retrovirus

To begin, attach the borosilicate glass capillary to the rubber cushioned clips in the manual vertical micropipette puller. Set the heat temperature of the micropipette puller to 950 degrees Celsius and perform pre-pulling to obtain a thinner and softer glass capillary. Then set the heat temperature to 790 degrees Celsius and perform a secondary pulling to produce final micropipettes.Using a micropipette grinder, carefully sharpen the tip opening to an outer diameter of 11 micrometers. Then place the micropipettes in a sponge clamping pad inside of a glass jar. Incubate the fertilized chicken eggs until development stage 18 in a 37 degree Celsius humidified rocking incubator.Wipe down the working area thoroughly with 70%ethanol. After development, remove the eggs from the incubator. Spray the eggs with 70%ethanol and allow them to air dry.Then place the egg on an egg holder with the larger end facing upwards. Using a pair of sharp toothed forceps, carefully tap on the larger end of the eggshell to create a two centimeter diameter hole. Then remove the fragments of the egg shell.Place the egg on a dissecting microscope stage and locate the embryo. Next, use the fine dissecting forceps and scissors to cut off the amniotic membrane covering the top of the embryo. Then place a 60 millimeter Petri dish over the opening of the egg.

Microinjection of an RCAS(A) Retrovirus into Embryonic Chicken Lens for Expressing Exogenous Proteins 

To begin, thaw the RCAS(A)retrovirus stock on ice. To avoid clogging the micropipette, centrifuge the solution at 10, 000 G for 10 seconds at four degrees Celsius and transfer the supernatant into a new tube while keeping the solutions on ice. Place a stretched laboratory parafilm on a 35 by 10 millimeter cell culture dish and add one microliter of sterile PBS to the parafilm.Connect a prepared glass micropipette to an automatic Pico injector. Press the fill mode to fill the PBS into a micropipette and then press the inject mode to test the allocated one microliter of liquid. Place a second piece of stretched laboratory parafilm on a new cell culture dish and add one microliter of fast green stained viral stock to the film.Lower the tip of the micropipette into the viral stock, and press the fill mode to fill the micropipette with one microliter of viral stock. Under a dissecting microscope, lower the filled micropipette connected to an automatic injector into the target region of the chicken embryo lens. Then adjust the light source to provide a clear view of the lens vesicle.After ensuring the micropipette is within the correct location inside the lens lumen, inject five to 40 nanoliters of the viral stock. After injection, wait 45 seconds before gently removing the micropipette. Next, check the successful microinjection by examining the fast green dye in the empty lumen of the lens without an leakage.Following examination, seal the eggshell opening with scotch tape and place the eggs in a 37 degree Celsius humidified static incubator. This study demonstrates the histological evaluation of the chimeric connexon 50 and 43 loops through immunofluorescence. Using Anti-Flag labeling, exogenous connexons were distinguished from endogenous ones.The study also evaluates the interaction between the intracellular loop domain of connexon 50 and Aquaporin zero.

665 Views.  University of Texas Health Science Center, San Antonio.  This protocol paper describes the methodology of embryonic chicken lens microinjection of an RCAS(A) retrovirus as a tool for studying in situ function and expression of proteins during lens development.

Studying Protein Expression During Chicken Lens Development

Summary