Name: analysis of protein-protein interactions and co-localization between components of gap, tight, and adherens junctions in murine mammary glands
Uploaded: 2017-05-30T14:00:00
Description: Watch this Scientific Journal Video about Analysis of Protein-protein Interactions and Co-localization Between Components of Gap, Tight, and Adherens Junctions in Murine Mammary Glands at JoVE.com

I.P. is funded by a Natural Sciences and Engineering Research Council of Canada grant (NSERC #418233-2012); a Fonds de Recherche du Qu&#233;bec-Sant&#233; (FRQS), a Quebec Breast Cancer Foundation career award, and a Leader Founds grant from the Canadian Foundation for Innovation grant. E.D. received a scholarship from the Fondation universitaire Armand-Frappier.

All animal protocols used in this study were approved by the University Animal Care Committee (INRS-Institut Armand-Frappier, Laval, Canada).
1. Identifying Protein Co-localization
<ol>
	<li>From tissue to microscopic slides 
	NOTE: Tissues and sections should be handled on dry ice.
	<ol>
		<li>Excise the mammary glands from an animal (for a complete description of this procedure, refer to Plante et al.)14.</li>
		<li>Embed the excised t...

<ol>
	<li>Sternlicht, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Key+stages+in+mammary+gland+development:+the+cues+that+regulate+ductal+branching+morphogenesis.">Key stages in mammary gland development: the cues that regulate ductal branching morphogenesis.</a> Breast Cancer Res. 8 (1), 201 (2006).</li><li>Oakes, S. R., Hilton, H. N., Ormandy, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+alveolar+switch:+coordinating+the+proliferative+cues+and+cell+fate+decisions+that+drive+the+formation+of+lobuloalveoli+from+ductal+epithelium.">The alveolar switch: coordinating the proliferative cues and cell fate decisions that drive the formation of lobuloalveoli from ductal epithelium.</a> Breast Cancer Res. 8 (2), 207 (2006).</li><li>Stein, T., Hilton, H. N., Ormandy, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+alveolar+switch:+coordinating+the+proliferative+cues+and+cell+fate+decisions+that+drive+the+formation+of+lobuloalveoli+from+ductal+epithelium.">The alveolar switch: coordinating the proliferative cues and cell fate decisions that drive the formation of lobuloalveoli from ductal epithelium.</a> Breast Cancer Res. 8 (2), 207 (2006).</li><li>El-Sabban, M. E., Abi-Mosleh, L. F., Talhouk, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developmental+regulation+of+gap+junctions+and+their+role+in+mammary+epithelial+cell+differentiation.">Developmental regulation of gap junctions and their role in mammary epithelial cell differentiation.</a> J Mammary Gland Biol Neoplasia. 8 (4), 463-473 (2003).</li><li>Hennighausen, L., Robinson, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Information+networks+in+the+mammary+gland.">Information networks in the mammary gland.</a> Nat Rev Mol Cell Biol. 6 (9), 715-725 (2005).</li><li>Gudjonsson, T., Adriance, M. C., Sternlicht, M. D., Petersen, O. W., Bissell, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myoepithelial+cells:+their+origin+and+function+in+breast+morphogenesis+and+neoplasia.">Myoepithelial cells: their origin and function in breast morphogenesis and neoplasia.</a> J Mammary Gland Biol Neoplasia. 10 (3), 261-272 (2005).</li><li>Nguyen, D. A., Neville, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tight+junction+regulation+in+the+mammary+gland.">Tight junction regulation in the mammary gland.</a> J Mammary Gland Biol Neoplasia. 3 (3), 233-246 (1998).</li><li>Stewart, M. K., Simek, J., Laird, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insights+into+the+role+of+connexins+in+mammary+gland+morphogenesis+and+function.">Insights into the role of connexins in mammary gland morphogenesis and function.</a> Reproduction. 149 (6), R279-R290 (2015).</li><li>Dianati, E., Poiraud, J., Weber-Ouellette, A., Connexins Plante, I., E-cadherin, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Claudin-7+and+beta-catenin+transiently+form+junctional+nexuses+during+the+post-natal+mammary+gland+development.">Claudin-7 and beta-catenin transiently form junctional nexuses during the post-natal mammary gland development.</a> Dev Biol. 416 (1), 52-68 (2016).</li><li>Derangeon, M., Spray, D. C., Bourmeyster, N., Sarrouilhe, D., Herve, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reciprocal+influence+of+connexins+and+apical+junction+proteins+on+their+expressions+and+functions.">Reciprocal influence of connexins and apical junction proteins on their expressions and functions.</a> Biochim Biophys Acta. 1788 (4), 768-778 (2009).</li><li>Hernandez-Blazquez, F. J., Joazeiro, P. P., Omori, Y., Yamasaki, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+intracellular+movement+of+connexins+by+E-cadherin+in+murine+skin+papilloma+cells.">Control of intracellular movement of connexins by E-cadherin in murine skin papilloma cells.</a> Exp Cell Res. 270 (2), 235-247 (2001).</li><li>Kiyokawa, E., Hara, S., Nakamura, T., Matsuda, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence+(Forster)+resonance+energy+transfer+imaging+of+oncogene+activity+in+living+cells.">Fluorescence (Forster) resonance energy transfer imaging of oncogene activity in living cells.</a> Cancer Sci. 97 (1), 8-15 (2006).</li><li>Gustafsdottir, S. M., 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=Proximity+ligation+assays+for+sensitive+and+specific+protein+analyses.">Proximity ligation assays for sensitive and specific protein analyses.</a> Anal Biochem. 345 (1), 2-9 (2005).</li><li>Plante, I., Stewart, M. K., Laird, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+mammary+gland+development+and+function+in+mouse+models.">Evaluation of mammary gland development and function in mouse models.</a> J Vis Exp. (53), (2011).</li><li>Green, M. R., Sambrook, J., Sambrook, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular cloning: a laboratory manual. , (2012).</li><li>Taylor, S. C., Berkelman, T., Yadav, G., Hammond, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+defined+methodology+for+reliable+quantification+of+Western+blot+data.">A defined methodology for reliable quantification of Western blot data.</a> Mol Biotechnol. 55 (3), 217-226 (2013).</li><li>Oxford, E. M., 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=Molecular+composition+of+the+intercalated+disc+in+a+spontaneous+canine+animal+model+of+arrhythmogenic+right+ventricular+dysplasia/cardiomyopathy.">Molecular composition of the intercalated disc in a spontaneous canine animal model of arrhythmogenic right ventricular dysplasia/cardiomyopathy.</a> Heart Rhythm. 4 (9), 1196-1205 (2007).</li><li>Wang, X., Li, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+mislocalization:+mechanisms,+functions+and+clinical+applications+in+cancer.">Protein mislocalization: mechanisms, functions and clinical applications in cancer.</a> Biochim Biophys Acta. 1846 (1), 13-25 (2014).</li><li>Bertocchi, C., 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=Nanoscale+architecture+of+cadherin-based+cell+adhesions.">Nanoscale architecture of cadherin-based cell adhesions.</a> Nat Cell Biol. 19 (1), 28-37 (2017).</li><li>Bajar, B. T., Wang, E. S., Zhang, S., Lin, M. Z., Chu, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Guide+to+Fluorescent+Protein+FRET+Pairs.">A Guide to Fluorescent Protein FRET Pairs.</a> Sensors (Basel). 16 (9), (2016).</li><li>Fredriksson, K., 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=Proteomic+analysis+of+proteins+surrounding+occludin+and+claudin-4+reveals+their+proximity+to+signaling+and+trafficking+networks.">Proteomic analysis of proteins surrounding occludin and claudin-4 reveals their proximity to signaling and trafficking networks.</a> PLoS One. 10 (3), e0117074 (2015).</li><li>Weibrecht, I., 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=Proximity+ligation+assays:+a+recent+addition+to+the+proteomics+toolbox.">Proximity ligation assays: a recent addition to the proteomics toolbox.</a> Expert Rev Proteomics. 7 (3), 401-409 (2010).</li><li>Malovannaya, 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=Streamlined+analysis+schema+for+high-throughput+identification+of+endogenous+protein+complexes.">Streamlined analysis schema for high-throughput identification of endogenous protein complexes.</a> Proc Natl Acad Sci U S A. 107 (6), 2431-2436 (2010).</li></ol>

Cell-cell interactions via junctions are required for the proper function and development of many organs, such as the mammary gland. Studies have shown that junctional proteins can regulate the function and stability of one another and activate signal transduction by tethering each other at the cell membrane10. The protocols presented in the current manuscript have provided interesting findings about junctional protein differential expression, localization, and interaction during normal murine gla...

Mammary gland growth and development occurs mainly after birth. This organ constantly remodels itself throughout the reproductive life of a mammal1. The adult mammary gland epithelium is comprised of an inner layer of luminal epithelial cells and an outer layer of basal cells, mainly composed of myoepithelial cells, surrounded by a basement membrane2. For a good review on mammary gland structure and development, the reader can refer to Sternlicht1. Cell-cell interactions via gap (GJ), tight (TJ), and adherens (AJ) junctions are necessary for the normal development and function of the gland1,3,4,5,6. The main components of these junctions in the murine mammary gland are Cx26, Cx30, Cx32, and Cx43 (GJ); Claudin-1, -3, -4, and -7 and ZO-1 (TJ); and E-cadherin, P-cadherin, and &#946;-catenin (AJ)7,8. The levels of expression of these different junctional proteins vary in a stage-dependent manner during mammary gland development, suggesting differential cell-cell interaction requirements9. GJ, TJ, and AJ are linked structurally and functionally and tether other structural or regulatory proteins to the neighboring sites of adjacent cells, thus creating a junctional nexus10. The composition of the junctional nexus can impact bridging with the underlying cytoskeleton, as well as nexus permeability and stability, and can consequently influence the function of the gland8,9,10,11. The components of intercellular junctions residing in junctional nexuses or interacting with one another at different developmental stages of mammary gland development were analyzed recently using co-immunofluorescence (co-IF) and co-immunoprecipitation (co-IP)9. While other techniques allow for the evaluation of the functional association between proteins, these methods are not presented in this manuscript.
As proteins merely act alone to function, studying protein-protein interactions (PPIs), such as signal transductions and biochemical cascades, is essential to many researchers and can provide significant information about the function of proteins. Co-IF and microscopic analysis help to evaluate a few proteins that share the same subcellular space. However, the number of targets is limited by the antibodies, which must be raised in different animals, and by the access to a confocal microscope equipped with different wavelength lasers and a spectral detector for multiplexing. Co-IP confirms or reveals high-affinity physical interactions between two or more proteins residing within a protein complex. Despite the development of novel techniques, such as fluorescence resonance energy transfer (FRET)12 and proximity ligation assay (PLA)13, which can simultaneously detect the localization and interactions of proteins, co-IP remains an appropriate and affordable technique to study interactions between endogenous proteins.
The step-by-step method described in this manuscript will facilitate the study of protein localization and PPIs and point out pitfalls to avoid when studying endogenous PPIs in the mammary glands. The methodology starts with the presentation of the different preservation procedures for the tissues required for each technique. Part 1 presents how to study protein co-localization in three steps: i) the sectioning of mammary glands, ii) the double- or triple-labeling of different proteins using the co-IF technique, and iii) the imaging of protein localization. Part 2 shows how to precipitate an endogenous protein and identify its interacting proteins in three steps: i) lysate preparation, ii) indirect protein immunoprecipitation, and iii) binding partner identification by SDS-PAGE and Western blot. Each step of this protocol is optimized for rodent mammary gland tissues and generates high-quality, specific, and reproducible results. This protocol can also be used as a starting point for PPI studies in other tissues or cell lines.

<table>
	<tbody>
		<tr>
			<td>Mice strain and stage&#160;</td>
			<td>St. Constant, Quebec, Canada</td>
			<td></td>
			<td>C57BL/6 Femals; pregnancy day 18 (P18) and lactation day 14 (L14), Charles River Canada&#160;</td>
		</tr>
		<tr>
			<td>PBS 10X (stock)</td>
			<td></td>
			<td></td>
			<td>1)&#160;&#160;&#160;&#160;&#160; Dissolve 80g NaCl (F.W.: 58.44), 2g KCl (F.W. 74.55), 26.8g Na2HPO4&#8226;7H2O (F.W. 268.07) and 2.4g KH2PO4 (F.W.:136.09) in 800ml distilled water.&#160; 
			2)&#160;&#160;&#160;&#160;&#160; Adjust the PH to 7.4&#160; 
			3)&#160;&#160;&#160;&#160;&#160; Add water to reach to the 1 litre final volume.&#160;</td>
		</tr>
		<tr>
			<td>TBS 10X (stock)</td>
			<td></td>
			<td></td>
			<td>1)&#160;&#160;&#160;&#160;&#160; Dissolve 60.5g TRIS, 87.6g NaCl in 800ml distilled water.&#160; 
			2)&#160;&#160;&#160;&#160;&#160; Adjust the PH to 7.5&#160; 
			3)&#160;&#160;&#160;&#160;&#160; Add water to reach to the 1 litre final volume.&#160;</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td colspan="4">Part 1-Immunofluorescence</td>
		</tr>
		<tr>
			<td>Freezing media</td>
			<td>VWR International, Ville Mont-Royal, QC, Canada</td>
			<td>95067-840</td>
			<td>VMR frozen sections compound&#160;</td>
		</tr>
		<tr>
			<td>Microtome</td>
			<td>Mississauga, ON, Canada</td>
			<td>956640</td>
			<td>Microm HM525, Thermo fisher scientific HM525 NX Cryostat 115V 60Hz</td>
		</tr>
		<tr>
			<td>Blades</td>
			<td>C.L. Sturkey, Inc. Les Produits&#160;Scientifiques&#160;ESBE&#160;St-Laurent, QC, Canada</td>
			<td>&#160;BLM1001C</td>
			<td>High profile gold coated blades</td>
		</tr>
		<tr>
			<td>Pap pen</td>
			<td>Cedarlane, Burlington, ON, Canada</td>
			<td>8899</td>
			<td>Super PAP Pen, Thermo fisher scientific</td>
		</tr>
		<tr>
			<td>Microscopic slides</td>
			<td>Fisher Scientific, Burlington, ON, Canada</td>
			<td>12-550-15</td>
			<td>Fisherbrand&#160;Superfrost Plus Microscope Slides</td>
		</tr>
		<tr>
			<td>Formaldehyde</td>
			<td>BioShop Canada Inc, Burlington, ON, Canada</td>
			<td>FOR201.1</td>
			<td>Forlmadehyde</td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin (BSA)</td>
			<td></td>
			<td></td>
			<td>Santa Cruz Biotechnology, Inc, California, USA</td>
		</tr>
		<tr>
			<td>Blocking solution</td>
			<td></td>
			<td></td>
			<td>3% BSA in TBS</td>
		</tr>
		<tr>
			<td>Wash solution</td>
			<td></td>
			<td></td>
			<td>TBS-Tween 20 0.1%</td>
		</tr>
		<tr>
			<td>Polysorbate 20</td>
			<td>Oakville, ON, Canada</td>
			<td>P 9416</td>
			<td>Tween 20, Sigma-Aldrich</td>
		</tr>
		<tr>
			<td>Mounting media</td>
			<td>Cedarlane, Burlington, ON</td>
			<td>17984-25(EM)</td>
			<td>Fluoromount-G</td>
		</tr>
		<tr>
			<td>First &#38; secondary antibodies&#160;</td>
			<td>Cell Signaling, Beverly, MA, USA</td>
			<td>Mentioned in Column D</td>
			<td>E-Cadherin (4A2) Mouse mAb (#14472s) 1/50 (Cell Signaling) with anti-mouse IgG Fab2 Alexa Fluor 555 (#4409s), Cell Signaling&#160;</td>
		</tr>
		<tr>
			<td>First &#38; secondary antibodies&#160;</td>
			<td>Life technologies, Waltham, MA, USA &#38; Cell Signaling, Beverly, MA, USA</td>
			<td>Mentioned in Column D</td>
			<td>Claudin-7 (#34-9100) 1/100 (Life Technologies) with anti-rabbit IgG Fab2 Alexa Fluor 488 (#4412s) (Cell Signaling)&#160;</td>
		</tr>
		<tr>
			<td>First &#38; secondary antibodies&#160;</td>
			<td>Santa Cruz Biotechnology, Inc, California, USA; Fischer Scientific, Burlington, ON, Canada&#160;</td>
			<td>Mentioned in Column D</td>
			<td>&#946;-Catenin Antibody (C-18): sc-1496 (SANTA CRUZ) with anti-Goat IgG (H+L) Alexa Fluor 568 (#A11057), Molecular Probe (Fisher Scientific)</td>
		</tr>
		<tr>
			<td>First &#38; secondary antibodies&#160;</td>
			<td>Life technologies, Waltham, MA, USA &#38; Cell Signaling, Beverly, MA, USA</td>
			<td>Mentioned in Column D</td>
			<td>Connexin26&#160; (#33-5800) 1/75 (Life Technologies) with anti-mouse IgG Fab2 Alexa Fluor 647 (#4410s)&#160;</td>
		</tr>
		<tr>
			<td>Nuclei stain</td>
			<td>Fisher Scientific, Burlington, ON, Canada</td>
			<td>D1306</td>
			<td>DAPI (4&#39;,6-Diamidino-2-Phenylindole, Dihydrochloride) 1/1000 in PBS</td>
		</tr>
		<tr>
			<td>Fluorescent microscope</td>
			<td>Nikon Canada, Mississauga, On, Canada</td>
			<td></td>
			<td>Nikon A1R+ confocal microscopic laser equipped with a spectral detector&#160;</td>
		</tr>
		<tr>
			<td>Software of IF images analysis</td>
			<td>Nikon Canada, Mississauga, On, Canada</td>
			<td></td>
			<td>NIS-elements software (version 4)</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td colspan="4">Part 2-Immunoprecipitation</td>
		</tr>
		<tr>
			<td>Triple-detergent Lysis buffer (100ml) pH=8.0&#160;</td>
			<td></td>
			<td></td>
			<td>1) Mix 50mM TRIS (F.W.&#160;:121.14), 150mM NaCl (F.W.&#160;:58.44), 0.02% Sodium Azide, 0.1% SDS, 1% NONIdET P40, 0.5% Sodium Deoxycholate in 80ml distilled H2O.&#160; 
			2) Adjust the PH to 8.0 with HCl 6N (~0.5ml). 
			3) Adjust the volume to 100ml. Keep it in fridge.&#160; 
			At the day of protein extraction, use 1/100 NaVo3, 1/100 protease/phosphatase inhibitor and 1/25 NAF in calculated amount of Triple detergent lysis buffer: 
			Sodium Fluorid (stock) solution 1.25M (F.W. 41.98), Sodium Orthovanadate (stock) Solution 1M (F.W.: 183.9)</td>
		</tr>
		<tr>
			<td>Protease/phosphatase inhibitor</td>
			<td>Fisher Scientific, Burlington, ON</td>
			<td>78441</td>
			<td>Halt Protease and Phosphatase Inhibitor Cocktail, EDTA-free (100X)</td>
		</tr>
		<tr>
			<td>Protein dosage</td>
			<td>Thermo Scientific, Rockford, Illinois, USA</td>
			<td>23225</td>
			<td>Pierce BCA protein assay kit&#160;</td>
		</tr>
		<tr>
			<td>Tissue grinder</td>
			<td>Fisher Scientific, Burlington, ON</td>
			<td>FTH-115</td>
			<td>Power 125, Model FTH-115</td>
		</tr>
		<tr>
			<td>Magnetic beads and stand</td>
			<td>Millipore, Etobicoke, ON, Canada</td>
			<td></td>
			<td>PureProteome Protein G Magnetic Bead System (LSKMAGG02)</td>
		</tr>
		<tr>
			<td>Wash solution for IP</td>
			<td></td>
			<td></td>
			<td>PBS or PBS-Tween20 0.1% depending to the step</td>
		</tr>
		<tr>
			<td>Primary antibodies for immunoprecipitation</td>
			<td>Cell Signaling, Beverly, MA, USA</td>
			<td>Mentioned in coulmn D</td>
			<td>IgG Rabbit (rabbit (DA1E) mAb IgG Isotype control (#3900s) (Cell Signaling) 0.5 &#181;l/200 &#181;l</td>
		</tr>
		<tr>
			<td>Primary antibodies for immunoprecipitation</td>
			<td>Cell Signaling, Beverly, MA, USA</td>
			<td>Mentioned in coulmn D</td>
			<td>IgG Mouse mouse (G3A1) mAb IgG Isotype control (#5415s) (Cell Signaling) 0.5 &#181;l/200 &#181;l&#160;</td>
		</tr>
		<tr>
			<td>Primary antibodies for immunoprecipitation</td>
			<td>Sigma-Aldrich, Oakville, ON, Canada</td>
			<td>Mentioned in coulmn D</td>
			<td>Connexin43 (#C6219) (Sigma-Aldrich) 4 &#181;l/200 &#181;l&#160;</td>
		</tr>
		<tr>
			<td>Primary antibodies for immunoprecipitation</td>
			<td>Cell Signaling, Beverly, MA, USA</td>
			<td>Mentioned in coulmn D</td>
			<td>E-cadherin (4A2) Mouse mAb (#14472s) (Cell Signaling) 1 &#181;l/200 &#181;l&#160;</td>
		</tr>
		<tr>
			<td>Laemmli buffer&#160;</td>
			<td>BIO-RAD, Mississauga, Ontario, Canada</td>
			<td>1610747</td>
			<td>4x Laemmli Sample Buffer (Add &#946;-mercaptoethanol following manufacturer recommendation)</td>
		</tr>
		<tr>
			<td>Acidic glycine&#160;</td>
			<td>Fisher Scientific, Burlington, ON</td>
			<td>PB381-5</td>
			<td>0.2 M glycine; adjust pH=2.5 with HCl&#160;</td>
		</tr>
		<tr>
			<td>Tris&#160;</td>
			<td>Fisher Scientific, Burlington, ON</td>
			<td>BP152-1</td>
			<td>1 M (pH=8)&#160;</td>
		</tr>
		<tr>
			<td>SDS-PAGE acrylamide gels&#160;</td>
			<td>BIO-RAD, Mississauga, ON, Canada</td>
			<td>1610180 -5</td>
			<td>TGX Stain-Free FastCast Acrylamide Solutionss (7.8%, 10%, 12%)</td>
		</tr>
		<tr>
			<td>Running buffer 10x&#160;</td>
			<td>BIO-RAD, Mississauga, ON, Canada</td>
			<td>1704272</td>
			<td>Tris 30.3g/glycine 144.1g /SDS 10g in 1 litre distilled water</td>
		</tr>
		<tr>
			<td>Membranes</td>
			<td>BIO-RAD, Mississauga, ON, Canada</td>
			<td>1704272</td>
			<td>PVDF membranes, Trans-Blot Turbo RTA Mini PVDF Transfer Kit</td>
		</tr>
		<tr>
			<td>Transfer method</td>
			<td>BIO-RAD, Mississauga, ON, Canada</td>
			<td>1704155</td>
			<td>Trans-Blot Turbo Transfer System</td>
		</tr>
		<tr>
			<td>Dry Milk</td>
			<td>Smucker Food of Canada Co, Markham, ON, Canada</td>
			<td></td>
			<td>Fat Free Instant Skim Milk Powder, Carnation</td>
		</tr>
		<tr>
			<td>Blocking solution for blots</td>
			<td></td>
			<td></td>
			<td>5% dry milk in TBS-Tween 20 0.1%</td>
		</tr>
		<tr>
			<td>Washing solutions for blots</td>
			<td></td>
			<td></td>
			<td>TBS-Tween 20 0.1%</td>
		</tr>
		<tr>
			<td>Primary and secondary antibodies for blots (10ml)</td>
			<td>Sigma-Aldrich, Oakville, Ontario &#38; Abcam, Toronto, ON, Canada</td>
			<td>Mentioned in column D</td>
			<td>Connexin43 (#C6219) (Sigma-Aldrich) 1/2500 with HRP-conjugated Veriblot for IP secondary antibody (ab131366) 1/5000 (Abcam, Toronto, ON, Canada)</td>
		</tr>
		<tr>
			<td>Primary and secondary antibodies for blots (10ml)</td>
			<td>Cell Signaling, Beverly, MA, USA &#38; Abcam, Toronto, ON, Canada</td>
			<td>Mentioned in column D</td>
			<td>E-cadherin (24E10) rabbit mAb 1/1000 (#3195s) (Cell Signaling) 1/1000 with HRP-conjugated Veriblot for IP secondary antibody&#160; (ab131366) 1/5000 (Abcam, Toronto, ON, Canada)</td>
		</tr>
		<tr>
			<td>Primary and secondary antibodies for blots (10ml)</td>
			<td>Life technologies, Waltham, MA, USA &#38; Abcam, Toronto, ON, Canada</td>
			<td>Mentioned in column D</td>
			<td>Claudin-7 (#34-9100) (Life technologies) 1/1000 with HRP-conjugated Veriblot for IP secondary antibody (ab131366)&#160; 1/5000 (Abcam, Toronto, ON, Canada)</td>
		</tr>
		<tr>
			<td>Primary and secondary antibodies for blots (10ml)</td>
			<td>Life technologies, Waltham, MA, USA &#38; Abcam, Toronto, ON, Canada</td>
			<td>Mentioned in column D</td>
			<td>Claudin3&#160; (#34-1700) (Life technologies) 1/1000 with HRP-conjugated Veriblot for IP secondary antibody&#160; (ab131366) 1/5000 (Abcam, Toronto, ON, Canada)</td>
		</tr>
		<tr>
			<td>Luminol solution for signal detection on blots</td>
			<td>BIO-RAD, Mississauga, ON, Canada</td>
			<td>1705061&#160;</td>
			<td>Clarity Western ECL Blotting Substrate&#160;</td>
		</tr>
		<tr>
			<td>Imaging blots</td>
			<td>BIO-RAD, Mississauga, ON, Canada</td>
			<td>1708280</td>
			<td>ChemiDoc MP imaging system</td>
		</tr>
		<tr>
			<td>Analayzing blots</td>
			<td>BIO-RAD, Mississauga, ON, Canada</td>
			<td></td>
			<td>ImageLab 5.2 software&#160;</td>
		</tr>
	</tbody>
</table>

analysis of protein-protein interactions and co-localization between components of gap, tight, and adherens junctions in murine mammary glands

Cell-cell interactions play a pivotal role in preserving tissue integrity and the barrier between the different compartments of the mammary gland. These interactions are provided by junctional proteins that form nexuses between adjacent cells. Junctional protein mislocalization and reduced physical associations with their binding partners can result in the loss of function and, consequently, to organ dysfunction. Thus, identifying protein localization and protein-protein interactions (PPIs) in normal and disease-related tissues is essential to finding new evidences and mechanisms leading to the progression of diseases or alterations in developmental status. This manuscript presents a two-step method to evaluate PPIs in murine mammary glands. In protocol section 1, a method to perform co-immunofluorescence (co-IF) using antibodies raised against the proteins of interest, followed by secondary antibodies labeled with fluorochromes, is described. Although co-IF allows for the demonstration of the proximity of the proteins, it does make it possible to study their physical interactions. Therefore, a detailed protocol for co-immunoprecipitation (co-IP) is provided in protocol section 2. This method is used to determine the physical interactions between proteins, without confirming whether these interactions are direct or indirect. In the last few years, co-IF and co-IP techniques have demonstrated that certain components of intercellular junctions co-localize and interact together, creating stage-dependent junctional nexuses that vary during mammary gland development.

To determine whether GJ, AJ, and TJ components can interact together in the mammary gland, co-IF assays were first performed. Cx26, a GJ protein, and &#946;-Catenin, an AJ protein, were probed with specific antibodies and revealed using fluorophore-conjugated mouse-647 (green, pseudocolor) and goat-568 (red) antibodies, respectively (Figure 1B and C). Data showed that they co-localize at the cell membrane of epithelial cells in the mice mammary gland on l...

Watch this Scientific Journal Video about Analysis of Protein-protein Interactions and Co-localization Between Components of Gap, Tight, and Adherens Junctions in Murine Mammary Glands at JoVE.com

Analysis of Protein-protein Interactions and Co-localization Between Components of Gap, Tight, and Adherens Junctions in Murine Mammary Glands

Intercellular junctions are requisites for mammary gland stage-specific functions and development. This manuscript provides a detailed protocol for the study of protein-protein interactions (PPIs) and co-localization using murine mammary glands. These techniques allow for the investigation of the dynamics of the physical association between intercellular junctions at different developmental stages.

Cell-cell interactions play a pivotal role in preserving tissue integrity and the barrier between the different compartments of the mammary gland. These ...

The overall goal of this method is to determine whether two or more intercellular junction proteins co-localize within cells and to further assess their physical interaction via co-immunoprecipitation. This method can help to answer key questions in the biology of the mammary gland field including the roles played by junctions in normal development and diseases such as breast cancer. The main advantage of this technique is that it can provide significant information about protein-protein interaction in vivo at a relatively low cost.To perform co-immuno fluorescent staining, retrieve the appropriate microscopic slides from the freezer. Immediately fix the sections by immersing them in four percent formaldehyde for 15 minutes at room temperature. Then, immerse the slides in phosphate-buffered saline at room temperature.Leave the slides there until proceeding to the next step. Circle each section of the slide using a commercially-available hydrophobic barrier or a water-repellent lab pen. Immediately add drops of PBS to the tissue, and place the slide in a human histology chamber for the remainder of the procedure.Block each tissue section with 100 to 200 microliters of three percent Bovine Serum Albumin-Tris-Buffered Saline, 0.1%polysorbate-20, for 30 minutes at room temperature. While the samples are blocking, prepare the primary and secondary antibody solutions by diluting the antibodies in TBS 0.1%polysorbate-20. After removing the blocking solution by aspiration, incubate the sections in 100 to 200 microliters of the diluted primary antibody for 60 minutes at room temperature.Then remove the primary antibody solution by aspiration and wash the sections with 250 to 500 microliters of TBS 0.1%polysorbate-20 for five minutes. Remove the wash solution by aspiration before repeating the wash twice. Aspirate the wash solution and incubate the sections with 100 to 200 microliters of the appropriate Fluoro-4 conjugated secondary antibody for 60 minutes at room temperature.After removing the secondary antibody solution by aspiration, wash the sections with 250 to 500 microliters of TBS 0.1%polysorbate-20 for five minutes. Remove the wash solution and repeat twice. Repeat these steps using the appropriate combination of primary and secondary bodies for any subsequent proteins of interest.Following removal of the final wash, perform the nuclei staining by incubating the section with 100 to 200 microliters of one milligram per millileter DAPI and TBS 0.1%polysorbate-20 for five minutes at room temperature. Aspirate the DAPI solution and mount the slides using a water-soluble, non-fluorescing mounting medium and cover slips. Place the slides flat in a four-degree Celsius refrigerator for at least eight hours.Proceed to the fluorescence microscopic imaging as described in the text protocol. Collect 500 to 1000 micrograms of the lysate and dilute it in PBS to each a final volume of 200 microliters in each 1.5-milliliter tube. Add the antibody against the antigen of interest to the first tube of lysate, and keep it on ice.Incubate the tubes overnight at four degrees Celsius on a tube-roller mixer at low speed. The following day, add 50 microliters of magnetic beads to new 1.5-milliliter tubes for pre-washing. Place the tubes containing the beads on the magnetic stand and allow the beads to migrate towards the magnet.Remove the storage buffer from the beads using a 200-microliter pipette. Wash the beads by adding 500 microliters of PBS 0.1%polysorbate-20, and vortex the tubes vigorously for 10 seconds. Then, put the tubes back onto the magnetic stand and allow the beads to migrate towards the magnet.Remove the excess wash buffer by pipetting with a 200-microliter pipette. Add the lysate antibody reaction complex to the beads and incubate for 90 minutes at room temperature on the roller mixer. Following the incubation, place the tubes on the magnetic stand and allow the beads to migrate toward the magnet.Using a 200-microliter pipette, aspirate and discard the lysate and place the tubes on ice. Wash the beads twice by adding 500 microliters of PBS, placing the tubes on the magnetic stand, and removing the liquid as before. During the wash steps, avoid vortexing, and keep the samples on ice.Wash the beads once with PBS 0.1%polysorbate-20 without vortexing and discard the last wash buffer using a 200-microliter pipette tip. To elute, add 20 microliters of 0.2 molar acidic glycine to the tubes and shake them for seven minutes on the roller mixer. After centrifuging at high speed for a few seconds, collect the supernatant in a fresh, ice-cold tube.Repeat the wash and elution steps for each tube. Then, add 10 microliters of 4x buffer to the 40-microliter eluted sample. Immediately add one molar Tris to the eluted samples, one drop at a time, until its color turns blue, and then proceed to the next tubes.Boil the eluted samples at 70 to 90 degrees Celsius for 10 minutes. Load the prepared lysates and the precipitated samples side-by-side in an SDS-PAGE acrylamide gel. Run the gel in running buffer at 100 volts for approximately 95 minutes, or until the edge of the migrating proteins reaches the bottom of the gel.Subsequently, transfer the gels to a nitrocellulose or PVDF membrane using a standard protocol. Then, block the membrane for one hour on a rocker on low speed in five-percent dry milk TTBS. To identify whether the precipitation was successful, probe the membrane using the first antibody against the precipitated protein.Dilute it in five percent dry milk TTBS at the concentration recommended by the manufacturer. Incubate the membrane overnight at four degrees Celsius on a rocking platform with slow agitation. The following day, wash the membrane three times for five minutes each with TTBS on a rocking platform with high agitation.Then, incubate the membrane in the appropriate secondary antibody conjugated with horseradish peroxidase, diluted in TTBS, for one hour at room temperature on a rocking platform with slow agitation. Perform three to six washes, each for five minutes, with TTBS on a rocking platform with high agitation. Analyze the signal of the secondary antibody by incubating the membrane with a commercially-available luminol solution and follow the manufacturer's instructions.Detect the signal using a chemiluminescence imaging system. To identify interacting proteins, repeat these steps using the appropriate antibodies on the same blot. To determine whether gap junction, adherence junction, and tight junction components can interact together in the mammary gland, co-immunofluorescence assays were performed.The co-immunofluorescence assay shows that beta-catenin, an integral protein of adherens junction, and Connexin 26, a gap junction protein, co-localize at the cell membrane in mice mammary glands on lactation day seven, as reflected by the yellow color. Cell nuclei are visualized with blue DAPI staining. Cryosections from mammary glands on pregnancy day 18 were cut and immunofluorescently stained for Claudin 7, a tight junction protein shown in green, E-Cadherin, an adherens junction protein shown in red, and Connexin 26, a gap junction protein shown in coral blue.Nuclei were stained with blue DAPI. E-Cadherin and Claudin 7 colocalization is displayed as a yellow to light orange color, while Connexin 26 colocalization with E-Cadherin and Claudin 7 resulted in white-punctuated staining. To find out which junctional proteins intermingle and physically tether together at the cell membrane, co-immunoprecipitation was performed using mammary gland tissues from lactating mice.Results showed that Connexin 43, a component of the gap junction, interacts with E-Cadherin and Claudin 7, but not with Claudin 3. These results were confirmed by the reciprocal immunoprecipitation. When E-Cadherin was immunoprecipitated, it interacted with Connexin 43 and Claudin 7.Once mastered, this technique can be done in two days for co-immunofluorescence for four to eight slides, and slides can be imaged the following day if it is performed properly. While attempting the co-immunofluorescence procedure, it is important to remember to choose different Fluoro 4 conjugated antibodies raised in different spaces with non-overlapping wavelengths and to select the proper protein A or G magnetic beads compatible with the antibodies used for co-immunoprecipitation. After its development, this technique paved the way for researchers in the field of cell biology to explore intercellular junctions'interplay in murine mammary glands.Don't forget that working is extremely hazardous and precautions should be always taken while performing this procedure.

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Research

JoVE Journal

Developmental Biology

Analysis of Zebrafish Larvae Skeletal Muscle Integrity with Evans Blue Dye

The zebrafish model is an emerging system for the study of neuromuscular disorders. In the study of neuromuscular diseases, the integrity of the muscle membrane is a critical disease determinant. To date, numerous neuromuscular conditions display degenerating muscle fibers with abnormal membrane integrity; this is most commonly observed in muscular dystrophies. Evans Blue Dye (EBD) is a vital, cell permeable dye that is rapidly taken into degenerating, damaged, or apoptotic cells; in contrast, it is not taken up by cells with an intact membrane. EBD injection is commonly employed to ascertain muscle integrity in mouse models of neuromuscular diseases. However, such EBD experiments require muscle dissection and/or sectioning prior to analysis. In contrast, EBD uptake in zebrafish is visualized in live, intact preparations. Here, we demonstrate a simple and straightforward methodology for performing EBD injections and analysis in live zebrafish. In addition, we demonstrate a co-injection strategy to increase efficacy of EBD analysis. Overall, this video article provides an outline to perform EBD injection and characterization in zebrafish models of neuromuscular disease.

In this study, we describe a straightforward method to perform Evans Blue Dye (EBD) analysis on zebrafish larvae. This technique is a powerful tool for the characterization of skeletal muscle integrity and delineation of zebrafish models of muscular dystrophy, and is a valuable method for the development of novel therapeutics.

The zebrafish model is an emerging system for the study of neuromuscular disorders.  In the study of neuromuscular diseases, the integrity of the muscle ...

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

The evolutionarily conserved&#160;extracellular signal transducing RTK-RAS-ERK pathway is an important kinase-signaling cascade that controls multiple cellular and developmental processes principally via activation of ERK, the terminal kinase of the pathway. Tight regulation of ERK activity is essential for normal development and homeostasis; overly active ERK results in excessive cellular proliferation, while underactive ERK causes cell death. C. elegans is a powerful model system that has helped characterize the function and regulation of RTK-RAS-ERK signaling pathway during development. In particular, the RTK-RAS-ERK pathway is essential for C. elegans germline development, which is the focus of this method. Using antibodies specific to the active, diphosphorylated form of ERK (dpERK), the stereotypical localization pattern can be visualized within the germline. Because this pattern is both spatially and temporally controlled, the ability to reproducibly assay dpERK is useful to identify regulators of the pathway that affect dpERK signal duration and amplitude and thus germline development. Here we demonstrate how to successfully dissect, stain, and image dpERK within the C. elegans gonad. This method can be adapted for spatial localization of any signaling or structural protein in the C. elegans gonad, provided an antibody compatible with immunofluorescence is available.

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

We present an immunofluorescence&#160;imaging-based method for spatial and temporal localization of active ERK in the dissected C. elegans gonad. The protocol described here can be adapted for visualization of any signaling or structural protein in the C. elegans gonad, provided a suitable antibody reagent is available.

The evolutionarily conserved&#160;extracellular signal transducing RTK-RAS-ERK pathway is an important kinase-signaling cascade that controls multiple ...

Co-localization of Cell Lineage Markers and the Tomato Signal

The cell lineage tracing system has been used predominantly in developmental biology studies. The use of Cre recombinase allows for the activation of the reporter in a specific cell line and all progeny. Here, we used the cell lineage tracing technique to demonstrate that chondrocytes directly transform into osteoblasts and osteocytes during long bone and mandibular condyle development using two kinds of Cre, Col10a1-Cre and Aggrecan-CreERT2 (Agg-CreERT2), crossed with Rosa26tdTomato. Both Col10 and aggrecan are well-recognized markers for chondrocytes.
On this basis, we developed a new method-cell lineage tracing in conjunction with fluorescent immunohistochemistry-to define cell fate by analyzing the expression of specific cell markers. Runx2 (a marker for early-stage osteogenic cells) and Dentin matrix protein1 (DMP1; a marker for late-stage osteogenic cells) were used to identify chondrocyte-derived bone cells and their differentiation status. This combination not only broadens the application of cell lineage tracing, but also simplifies the generation of compound mice. More importantly, the number, location, and differentiation statuses of parent cell progeny are displayed simultaneously, providing more information than cell lineage tracing alone. In conclusion, the co-application of cell lineage tracing techniques and immunofluorescence is a powerful tool for investigating cell biology in vivo.

We developed two sets of tracing combinations in Rosa26tdtomato (ubiquitously expressed in all cells)/Cre (specifically expressed in chondrocytes) mice: one with 2.3Col1a1-GFP (specific to osteoblasts) and one with immunofluorescence (specific to bone cells). The data demonstrate the direct transformation of chondrocytes into bone cells.

The cell lineage tracing system has been used predominantly in developmental biology studies. The use of Cre recombinase allows for the activation of the ...

Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model

Bone-forming osteoblasts interact with bone-resorbing osteoclasts to coordinate the turnover of bone matrix and to control skeletal homeostasis. Medaka and zebrafish larvae are widely used to analyze the behavior of bone cells during bone formation, degeneration, and repair. Their optical clarity allows the visualization of fluorescently labeled bone cells and fluorescent dyes bound to the mineralized skeletal matrix. Our lab has generated transgenic medaka fish that express the osteoclast-inducing factor Receptor Activator of Nuclear-factor &#954;B Ligand (RANKL) under the control of a heat&#160;shock-inducible promoter. Ectopic expression of RANKL results in the excess formation of activated osteoclasts, which can be visualized in reporter lines with nlGFP expression under the control of the cathepsin K (ctsk) promoter. RANKL induction and ectopic osteoclast formation leads to severe osteoporosis-like phenotypes. Compound transgenic medaka lines that express ctsk:nlGFP in osteoclasts, as well as mCherry under the control of the osterix (osx) promoter in premature osteoblasts, can be used to study the interaction of both cell types. This facilitates the in vivo observation of cellular behavior under conditions of bone degeneration and repair. Here, we describe the use of this system to test a drug commonly used in human osteoporosis therapy and describe a protocol for live imaging. The medaka model complements studies in cell culture and mice, and offers a novel system for the in vivo analysis of drug action in the skeletal system.

Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model

Small laboratory fish have become popular models for bone research on the mechanisms underlying human bone disorders and for the screening of bone-modulating drugs. In this report, we describe a protocol to assess the effect of alendronate on bone cells in medaka larvae with osteoporotic lesions.

Bone-forming osteoblasts interact with bone-resorbing osteoclasts to coordinate the turnover of bone matrix and to control skeletal homeostasis. Medaka ...

Transfer of Mammary Gland-forming Ability Between Mammary Basal Epithelial Cells and Mammary Luminal Cells via Extracellular Vesicles/Exosomes

Cells can communicate via exosomes, ~100-nm extracellular vesicles (EVs) that contain proteins, lipids, and nucleic acids. Non-adherent/mesenchymal mammary epithelial cell (NAMEC)-derived extracellular vesicles can be isolated from NAMEC medium via differential ultracentrifugation. Based on their density, EVs can be purified via ultracentrifugation at 110,000 x g. The EV preparation from ultracentrifugation can be further separated using a continuous density gradient to prevent contamination with soluble proteins. The purified EVs can then be further evaluated using nanoparticle-tracking analysis, which measures the size and number of vesicles in the preparation. The extracellular vesicles with a size ranging from 50 to 150 nm are exosomes. The NAMEC-derived EVs/exosomes can be ingested by mammary epithelial cells, which can be measured by flow cytometry and confocal microscopy. Some mammary stem cell properties (e.g., mammary gland-forming ability) can be transferred from the stem-like NAMECs to mammary epithelial cells via the NAMEC-derived EVs/exosomes. Isolated primary EpCAMhi/CD49flo luminal mammary epithelial cells cannot form mammary glands after being transplanted into mouse fat pads, while EpCAMlo/CD49fhi basal mammary epithelial cells form mammary glands after transplantation. Uptake of NAMEC-derived EVs/exosomes by EpCAMhi/CD49flo luminal mammary epithelial cells allows them to generate mammary glands after being transplanted into fat pads. The EVs/exosomes derived from stem-like mammary epithelial cells transfer mammary gland-forming ability to EpCAMhi/CD49flo luminal mammary epithelial cells.

This protocol describes methods for purifying, quantitating, and characterizing extracellular vesicles (EVs)/exosomes from non-adherent/mesenchymal mammary epithelial cells and for using them to transfer mammary gland-forming ability to luminal mammary epithelial cells. EVs/exosomes derived from stem-like mammary epithelial cells can transfer this cell property to cells that ingest the EVs/exosomes.

Cells can communicate via exosomes, ~100-nm extracellular vesicles (EVs) that contain proteins, lipids, and nucleic acids. Non-adherent/mesenchymal ...

Quantifying Branching Density in Rat Mammary Gland Whole-mounts Using the Sholl Analysis Method

An increasing number of studies are utilizing the rodent mammary gland as an endpoint for assessing the developmental toxicity of a chemical exposure. The effects these exposures have on mammary gland development are typically evaluated using either basic dimensional measurements or by scoring morphological characteristics. However, the broad range of methods for interpreting developmental changes could lead to inconsistent translations across laboratories. A common method of assessment is needed so that proper interpretations can be formed from data being compared across studies. The present study describes the application of the Sholl analysis method to quantify mammary gland branching characteristics. The Sholl method was originally developed for use in quantifying neuronal dendritic patterns. By using ImageJ, an open-source image analysis software package, and a plugin developed for this analysis, the mammary gland branching density and the complexity of a mammary gland from a peripubertal female rat were determined. The methods described here will enable the use of the Sholl analysis as an effective tool for quantifying an important characteristic of mammary gland development.

Mammary gland development in the rodent has typically been evaluated using descriptive assessments or by measuring basic physical attributes. Branching density is an indicator of mammary development that is difficult to quantify objectively. This protocol describes a reliable method for the quantitative assessment of mammary gland branching characteristics.

An increasing number of studies are utilizing the rodent mammary gland as an endpoint for assessing the developmental toxicity of a chemical exposure. The ...

A Novel Mammary Fat Pad Transplantation Technique to Visualize the Vessel Generation of Vascular Endothelial Stem Cells

Endothelial cells (ECs) are the fundamental building blocks of the vascular architecture and mediate vascular growth and remodeling to ensure proper vessel development and homeostasis. However, studies on endothelial lineage hierarchy remain elusive due to the lack of tools to gain access as well as to directly evaluate their behavior in vivo. To address this shortcoming, a new tissue model to study angiogenesis using the mammary fat pad has been developed. The mammary gland develops mostly in the postnatal stages, including puberty and pregnancy, during which robust epithelium proliferation is accompanied by extensive vascular remodeling. Mammary fat pads provide space, matrix, and rich angiogenic stimuli from the growing mammary epithelium. Furthermore, mammary fat pads are located outside the peritoneal cavity, making them an easily accessible grafting site for assessing the angiogenic potential of exogenous cells. This work also describes an efficient tracing approach using fluorescent reporter mice to specifically label the targeted population of vascular endothelial stem cells (VESCs) in vivo. This lineage tracing method, coupled with subsequent tissue whole-mount microscopy, enable the direct visualization of targeted cells and their descendants, through which the proliferation capability can be quantified and the differentiation commitment can be fate-mapped. Using these methods, a population of bipotent protein C receptor (Procr) expressing VESCs has recently been identified in multiple vascular systems. Procr+ VESCs, giving rise to both new ECs and pericytes, actively contribute to angiogenesis during development, homeostasis, and injury repair. Overall, this manuscript describes a new mammary fat pad transplantation and in vivo lineage tracing techniques that can be used to evaluate the stem cell properties of VESCs.

This work demonstrates a novel approach to assess the proliferation, differentiation, and vessel-forming potential of vascular endothelial stem cells (VESCs) through mammary fat pad transplantation followed by whole-mount tissue preparation for microscopic observation. A lineage tracing strategy to investigate the behavior of VESCs in vivo is also presented.

Endothelial cells (ECs) are the fundamental building blocks of the vascular architecture and mediate vascular growth and remodeling to ensure proper ...

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

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

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

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

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the proteins involved in these pathways are evolutionarily conserved between mammals and other eukaryotes, such as the fruit fly Drosophila melanogaster, suggesting that similar organizing principles exist during the development of these organisms. Importantly, Drosophila has been used extensively to identify cellular and molecular mechanisms regulating processes that are required in mammals including neurogenesis, differentiation, axonal guidance, and synaptogenesis. Flies have also been used successfully to model a variety of human neurodevelopmental diseases. Here we describe a protocol for the step-by-step microdissection, fixation, and immunofluorescent localization of proteins within the adult Drosophila brain. This protocol focuses on two example neuronal populations, mushroom body neurons and retinal photoreceptors, and includes optional steps to trace individual mushroom body neurons using Mosaic Analysis with a Repressible Cell Marker (MARCM) technique. Example data from both wild-type and mutant brains are shown along with a brief description of a scoring criteria for axonal guidance defects. While this protocol highlights two well-established antibodies for investigating the morphology of mushroom body and photoreceptor neurons, other Drosophila brain regions and the localization of proteins within other brain regions can also be investigated using this protocol.

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

This protocol describes the dissection and immunostaining of adult Drosophila melanogaster brain tissues. Specifically, this protocol highlights the use of Drosophila mushroom body and photoreceptor neurons as example neuronal subsets that can be accurately used to uncover general principles underlying many aspects of neuronal development.

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the ...

Two-step Approach to Explore Early- and Late-stages of Organ Formation in the Avian Model: The Thymus and Parathyroid Glands Organogenesis Paradigm

The avian embryo, as an experimental model, has been of utmost importance for seminal discoveries in developmental biology. Among several approaches, the formation of quail-chicken chimeras and the use of the chorioallantoic membrane (CAM) to sustain the development of ectopic tissues date back to the last century. Nowadays, the combination of these classical techniques with recent in vitro methodologies offers novel prospects to further explore organ formation.
Here we describe a two-step approach to study early- and late-stages of organogenesis. Briefly, the embryonic region containing the presumptive territory of the organ is isolated from quail embryos and grown in vitro in an organotypic system (up to 48 h). Cultured tissues are subsequently grafted onto the CAM of a chicken embryo. After 10 days of in ovo development, fully formed organs are obtained from grafted tissues. This method also allows the modulation of signaling pathways by the regular administration of pharmacological agents and tissue genetic manipulation throughout in vitro and in ovo developmental steps. Additionally, developing tissues can be collected at any time-window to analyze their gene-expression profile (using quantitative PCR (qPCR), microarrays, etc.) and morphology (assessed with conventional histology and immunochemistry).
The described experimental procedure can be used as a tool to follow organ formation outside the avian embryo, from the early stages of organogenesis to fully formed and functional organs.

This article provides an updated approach to the classical quail-chicken chimera system to study organ formation, by combining novel in vitro and in ovo experimental procedures.

The avian embryo, as an experimental model, has been of utmost importance for seminal discoveries in developmental biology. Among several approaches, the ...