We would like to acknowledge our funding source: NIH R01 EY05661 to J.E.H, Ines Gehring for assisting with generating the aqp0a/b double mutants and zebrafish husbandry, Dr Daniel Dranow for discussions leading to generation of the transgenics, Dr Bruce Blumberg and Dr Ken Cho&#8217;s labs for use of their dissecting microscopes, and Dr Megan Smith for help with statistical analysis.

The animal protocols used in this study adhere to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research and have been approved by the Institutional Animal Care and Use Committee (IACUC) of University of California, Irvine.

1. Zebrafish Husbandry and Euthanasia
<ol>
	<li>Raise and maintain zebrafish (AB strain) under standard laboratory conditions12. Raise embryos in embryo medium (EM)12. Add 0.003% PTU to EM from 20-24 h postfertilization (before the prim-5 stage) to prevent pigment formation in embryos12 used for imaging at embryonic stages9. Raise larvae from 6-30 days postfertilization (dpf) on a diet of live rotifers until 14 dpf, and live artemia after 14 dpf12. 
	CAUTION: PTU is very toxic</li>
	<li>Anesthetize fish using tricaine until non-responsive to touch.
	<ol>
		<li>Prepare tricaine stock by combining 400 mg of 3-amino benzoic acidethylester, with 2.1 mL of 1 M Tris (pH 9), in 100 mL of ddH2O. Adjust to pH 7.0 and store at -20 &#176;C. 
		CAUTION: Tricaine is toxic.</li>
		<li>Dilute 4.2 mL of tricaine stock in 100 mL of tank water to anesthetize larvae/adults or in EM to anesthetize embryos (final concentration of tricaine at 0.0165% w/v).</li>
	</ol>
	</li>
</ol>
2. Fixation of Embryos and Larvae
NOTE: Immunohistochemical protocols were adapted from previously published materials7.
<ol>
	<li>Fix dechorionated embryos or larvae up to 2 weeks postfertilization in 4% (v/v) paraformaldehyde (PFA) in phosphate buffered saline (PBS) overnight at 4 &#176;C on a rocker. 
	CAUTION: PFA is combustible and is carcinogenic.</li>
	<li>Wash embryos three times for 10 min in PBS, and permeabilize in PBS with 10% Triton and 1% DMSO (PBS-T) overnight at 4 &#176;C. 
	CAUTION: DMSO is toxic, is harmful by ingestion or skin absorption, carries hazardous materials through skin, and is combustible. Triton is toxic, corrosive and is hazardous to aquatic environments.</li>
</ol>
3. Dissection of Larval and Adult Zebrafish Lenses
<ol>
	<li>Anesthetize fish from 6 dpf larvae to adulthood with tricaine until non-responsive to touch but still showing a strong heartbeat. Measure fish standard length as per Schilling (2002) for staging13.</li>
	<li>Immediately excise eyes using micro-dissection scissors and place into a dissection dish in PBS (Figure 2 shown for adult eyes).
	<ol>
		<li>Make a custom 35 mm dish filled with silicone for lens dissections. Once silicone has set, excise a divot around 2-3 mm in diameter and 0.5 mm deep for immobilizing adult eyes/lenses during dissection.</li>
	</ol>
	</li>
	<li>Dissection of adult zebrafish lenses
	<ol>
		<li>Place an adult eye into the dish divot posterior side up filled with PBS. Immobilize the eye by inserting forceps at &#60;45&#176; angle through the optic disc. Be careful not to nick or compress the lens. Make two or three radial incisions through retina and sclera from the optic disc to the ciliary zone with dissection scissors.</li>
		<li>Peel back the retina and sclera like flower petals and invert the eye, cornea side up. Immobilize the lens indirectly via manipulation of the sclera and cornea with the flat side of the scissors, while pulling away the retina and attached tissues with forceps. Carefully trim excess tissue from the lens. 
		NOTE: It is vital to dissect carefully to obtain consistently healthy lenses.</li>
	</ol>
	</li>
	<li>Dissection of larval zebrafish lenses
	<ol>
		<li>Place a larval eye posterior side up onto the flat part of the silicone dish filled with PBS and use a sharpened tungsten needle to make radial cuts through the retina and sclera while immobilizing the eye with another tungsten needle or forceps. 
		NOTE: Be careful not to damage the lens.
		<ol>
			<li>Sharpen the tip of a 2 cm length of 0.1 mm tungsten wire electrolytically by suspending the wire tip into 10% (w/v) NaOH and applying a low voltage alternating-current14. Secure the needle into a Pasteur pipette by melting the glass end using a Bunsen burner. 
			NOTE: Alternative fine dissection tools can also be used. 
			CAUTION: NaOH is corrosive.</li>
		</ol>
		</li>
		<li>Gently scoop out the lens from the dissociated eye with a blunt side of the needle, and carefully pull away attached tissue.</li>
	</ol>
	</li>
</ol>
4. Fixation of Dissected Lenses
<ol>
	<li>Immediately fix dissected lenses in 1.5% (v/v) PFA in PBS for 24 h at room temperature (RT). Wash lenses three times in PBS for 10 min each.</li>
	<li>Permeabilize lenses for whole mount analysis or cryoprotect for cryosectioning (see section 8).
	<ol>
		<li>Permeabilize lenses in PBS-T overnight at 4 &#176;C.</li>
	</ol>
	</li>
</ol>
5. Lens Immunohistochemistry
<ol>
	<li>Label membranes of fixed embryo/larval or adult lenses by incubation in Phalloidin- Alexa Fluor 546 (1:200) and cell nuclei with DAPI (1:1,000 of 5 mg/mL stock) in PBS-T overnight at 4 &#176;C. 
	CAUTION: DAPI is a skin and eye irritant.</li>
	<li>Wash three times with PBS-T for 10 min each. Clear tissue by incubation in 30%, 50% and 70% glycerol in PBS-T (v/v) for at least 1 h at RT each, or overnight at 4 &#176;C.</li>
	<li>Mount fish in 70% glycerol in PBS-T (v/v) onto glass bottom 35 mm microwell dishes with eyes as flat and straight against the cover slip as possible. For younger fish, a slight anterior-lateral tilt may help to orient the lens suture to be parallel to the coverslip.</li>
</ol>
6. Analysis of Zebrafish Anterior Lens Sutures Using a Transgenic Line In Vivo
<ol>
	<li>Generate Tg(&#946;B1cry:mAppleCAAX) lines using the Tol2 kit15. The Tol2 transposable element system15 enables stable integration of the construct where mApple is driven by 300 bp of the human &#946;B1-crystallin promoter16 tethered to the membrane by the CAAX sequence resulting in expression specifically in lens fiber cell membranes. 
	NOTE: This construct (ID:122451) is available for purchase.
	<ol>
		<li>On the morning of injection, prepare the injection mixture and keep on ice. To reach a final volume of 10 &#181;L of containing RNase- and DNase-free H2O, add: 1.5 &#181;L of hu&#946;B1cry:mAppleCAAX DNA construct at 50 ng/&#181;L - [0.375-0.75 pg/final injection], 1.5 &#181;L of Tol2 transposase mRNA at 300 ng/&#181;L (Tol2 kit)15 [15-30 pg/final injection], and 1 &#181;L of phenol red indicator at 1% w/v [1 x10-5% (w/v)/final injection].</li>
		<li>Inject 50-100 pL of injection mixture into 1-cell stage embryos12.</li>
	</ol>
	</li>
	<li>Measure transgenesis efficiency in F0 injected embryos by measuring frequency of embryos with mApple positive lenses at 3 dpf. 
	NOTE: Expect to have &#62;80% transgenesis efficiency using this method. F0 mosaics allow detailed analysis of membrane morphologies of individual cells. Varying levels of mosaicism allows one to image the morphologies of single or small groups of cells, while more global lens expression allows analysis of multicellular structures like lens sutures in vivo.</li>
	<li>Outcross F0 mosaic fish to generate stable lines, which label all fiber cell membranes. F0 founders with the transgene integrated into the germline will generate offspring with stable integrations that can be maintained as transgenic lines.</li>
</ol>
7. Analysis of Zebrafish Anterior Lens Sutures Using a Transgenic Line In Vivo
<ol>
	<li>Anesthetize 3 dpf or adult mosaic or stable transgenic fish and mount in 1% low melt agarose (LMA) with tricaine with the eye flat against the cover slip of glass bottom microwell dishes.
	<ol>
		<li>Dissolve 1 g of LMA in 100 mL of EM (without methylene blue) to make 1% LMA. Store long term as 15 mL stocks at 4 &#176;C. Microwave to dissolve stock and store at 42 &#176;C until each tube is used.</li>
	</ol>
	</li>
	<li>Cover fish up to 6 dpf with EM with tricaine, or with tank water with tricaine for adults when LMA is set.
	<ol>
		<li>Mix 5 mL of EM without methylene blue or tank water with 250 &#181;L of tricaine stock and 7 &#181;L of PTU if imaging PTU treated fish.</li>
	</ol>
	</li>
</ol>
8. Lens Cryosectioning and Immunohistochemistry
<ol>
	<li>Cryoprotect fixed embryos or adult lenses by placing into 10% sucrose in PBS (w/v), 20% sucrose for 1 h at RT each (or overnight at 4 &#176;C) and overnight in 30% sucrose at 4 &#176;C.</li>
	<li>Embed tissue in OCT in base molds, and then freeze onto chucks with OCT. Cryosection at 12-14 &#181;m and collect onto a Superfrost/Plus microscope slides. Warm sections onto slide for 10 min on a slide warmer prewarmed to ~35 &#176;C.</li>
	<li>Wash sections three times with PBS for 10 min each. Label sections with Phalloidin-Alexa Flour 546 (1:200) with DAPI (1:1,000) or WGA-Alexa Flour 594 (1:200), followed by three PBS washes. Mount with anti-fade mounting medium, and seal coverslip with nail polish.</li>
</ol>
9. Imaging
<ol>
	<li>Acquire images with a confocal microscope. Acquire z-stacks or optical slices using a 60x N/A 1.2 water-immersion objective, or similar, at specific regions from the anterior to posterior lens pole. Use the following acquisition settings: 1.2 airy disc using the 561 nm laser, Texas red filter for phalloidin-Alexa Flour 546 or mApple, or the 405 laser with the UV filter for DAPI.</li>
	<li>Correct z-intensity laser power to counteract signal loss with depth into the lens. This allows for a strong signal at the posterior pole of fixed and live 3 dpf embryos, and strong signal in equatorial optical slices in adult fish lenses.</li>
	<li>Compile and view images using image processing software.</li>
</ol>
10. Measurement of Lens Nucleus Localization in the Anterior-posterior Axis
<ol>
	<li>Orient freshly excised lenses axially in PBS in a 35 mm dish with a coverglass bottom, with poles and sutures oriented parallel to the plane of focus. Look for a difference in the refractive index, which usually occurs at the interface of the lens cortex and lens nucleus to identify the lens nucleus. 
	NOTE: Healthy wild type adult lenses are extremely transparent making it difficult to see the lens sutures and nucleus, or to determine lens orientation. In this case, a slight nick with forceps to the lens capsule causes minor damage, which makes the sutures and lens nucleus apparent in about 10 min helping to orient the lens for this measurement. However, the lenses become unusable for downstream applications as they are now damaged.</li>
	<li>Take images of lenses with the lens nucleus in focus under bright field illumination with or without DIC optics using a dissection microscope with a camera attached. Image a micrometer under the same magnification for calibration.
	<ol>
		<li>Click on the live view button, adjust the exposure settings to visualize the lens nucleus and lens periphery, and take an image by clicking the snap shot button. Save as a tif file.</li>
		<li>Use image processing software to calibrate the acquired lens images. Select the straight-line tool and draw a line of known length on the micrometer image, click analyze | set scale. Enter known distance, units and select &#39;global&#39; calibration, and click ok.</li>
	</ol>
	</li>
	<li>Measure the distance of the center of the lens nucleus to the anterior pole (a - r).
	<ol>
		<li>Use the straight-line tool in image processing software to draw a line across the imaged center of the lens nucleus in an axial orientation. Take the center of this line as the center of the lens nucleus.</li>
		<li>Draw another line from this point to the anterior pole of the lens and select &#39;measure&#39; in the &#39;analyze&#39; menu to measure the distance (a - r), where a is the radius of the lens and r is the distance from the center of the lens to the center of the nucleus.</li>
		<li>Draw another line from the anterior to the posterior poles and measure this distance as the lens diameter (2a). Copy these lengths from the &#39;results&#39; window and transfer to a spreadsheet or statistics program. 
		NOTE: It is easier to precisely measure from the center of the nucleus to the anterior pole, than measuring from the center of the lens nucleus to the center of the lens. This measurement is converted by the formula in step 10.3.5&#160;to report the distance of the center of the lens nucleus to the center of the lens. Always use the adult nucleus for measurements, even if the embryonic nucleus is evident.</li>
		<li>Divide the diameter by 2, to calculate the lens radius, a.</li>
		<li>Calculate r/a, as <img alt="Equation 1" src="/files/ftp_upload/59528/59528eq1.jpg" style="opacity: 0.9;" />, which is the normalized localization of the lens nucleus with respect to the lens radius. 
		NOTE: For a nucleus placed closer to the anterior pole, r/a&#160;will be &#62;0.0, while a centrally localized nucleus will have an&#160;r/a of 0.0.</li>
	</ol>
	</li>
	<li>Graph the log of the normalized axial nucleus measurement as a function of the standard length to determine changes in lens nucleus localization during zebrafish development.</li>
</ol>

<ol>
	<li>Vorontsova, I., Gehring, I., Hall, J. E., Schilling, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aqp0a+Regulates+Suture+Stability+in+the+Zebrafish+Lens.">Aqp0a Regulates Suture Stability in the Zebrafish Lens.</a> Investigative Ophthalmology &#38; Visual Science. 59 (7), 2869-2879 (2018).</li><li>Hall, J. E., Mathias, R. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Aquaporin+Zero+Puzzle.">The Aquaporin Zero Puzzle.</a> Biophysical Journal. 107 (1), 10-15 (2014).</li><li>Nakazawa, Y., Oka, M., Funakoshi-Tago, M., Tamura, H., Takehana, 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+Extracellular+C-loop+Domain+Plays+an+Important+Role+in+the+Cell+Adhesion+Function+of+Aquaporin+0.">The Extracellular C-loop Domain Plays an Important Role in the Cell Adhesion Function of Aquaporin 0.</a> Current Eye Research. 42 (4), 617-624 (2017).</li><li>Kumari, S. S., Varadaraj, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intact+AQP0+performs+cell-to-cell+adhesion.">Intact AQP0 performs cell-to-cell adhesion.</a> Biochemical and Biophysical Research Communications. 390 (3), 1034-1039 (2009).</li><li>Lindsey Rose, K. 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=The+C+Terminus+of+Lens+Aquaporin+0+Interacts+with+the+Cytoskeletal+Proteins+Filensin+and+CP49.">The C Terminus of Lens Aquaporin 0 Interacts with the Cytoskeletal Proteins Filensin and CP49.</a> Investigative Ophthalmology &#38; Visual Science. 47 (4), 1562-1570 (2006).</li><li>Kumari, S. S., Varadaraj, K. <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+plays+a+pivotal+role+in+refractive+index+gradient+development+in+mammalian+eye+lens+to+prevent+spherical+aberration.">Aquaporin 0 plays a pivotal role in refractive index gradient development in mammalian eye lens to prevent spherical aberration.</a> Biochemical and Biophysical Research Communications. 452 (4), 986-991 (2014).</li><li>Uribe, R. A., Gross, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunohistochemistry+on+Cryosections+from+Embryonic+and+Adult+Zebrafish+Eyes.">Immunohistochemistry on Cryosections from Embryonic and Adult Zebrafish Eyes.</a> Cold Spring Harbor Protocols. 2007 (7), (2007).</li><li>Dahm, R., Schonthaler, H. B., Soehn, A. S., van Marle, J., Vrensen, G. F. J. M. <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+adult+morphology+of+the+eye+lens+in+the+zebrafish.">Development and adult morphology of the eye lens in the zebrafish.</a> Experimental Eye Research. 85 (1), 74-89 (2007).</li><li>Kimmel, C. B., Ballard, W. W., Kimmel, S. R., Ullmann, B., Schilling, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stages+of+embryonic+development+of+the+zebrafish.">Stages of embryonic development of the zebrafish.</a> Developmental Dynamics. 203 (3), 253-310 (1995).</li><li>Greiling, T. M. S., Clark, J. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+lens+development+in+the+zebrafish:+A+three-dimensional+time-lapse+analysis.">Early lens development in the zebrafish: A three-dimensional time-lapse analysis.</a> Developmental Dynamics. 238 (9), 2254-2265 (2009).</li><li>Godinho, L., 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=Targeting+of+amacrine+cell+neurites+to+appropriate+synaptic+laminae+in+the+developing+zebrafish+retina.">Targeting of amacrine cell neurites to appropriate synaptic laminae in the developing zebrafish retina.</a> Development. 132 (22), 5069-5079 (2005).</li><li>Westerfield, 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> The Zebrafish Book: A Guide for the Laboratory Use of Zebrafish (Danio rerio). , (2002).</li><li>Schilling, T. F., Nusslein-Volhard, C., Dahm, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Zebrafish. 261, 59-94 (2002).</li><li>Brady, 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+simple+technique+for+making+very+fine,+durable+dissecting+needles+by+sharpening+tungsten+wire+electrolytically.">A simple technique for making very fine, durable dissecting needles by sharpening tungsten wire electrolytically.</a> Bulletin of the World Health Organization. 32 (1), 143-144 (1965).</li><li>Kwan, K. 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=The+Tol2kit:+A+multisite+gateway-based+construction+kit+for+Tol2+transposon+transgenesis+constructs.">The Tol2kit: A multisite gateway-based construction kit for Tol2 transposon transgenesis constructs.</a> Developmental Dynamics. 236 (11), 3088-3099 (2007).</li><li>Hou, H. H., Kuo, M. Y. P., Luo, Y. W., Chang, B. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recapitulation+of+human+&#946;B1-crystallin+promoter+activity+in+transgenic+zebrafish.">Recapitulation of human &#946;B1-crystallin promoter activity in transgenic zebrafish.</a> Developmental Dynamics. 235 (2), 435-443 (2006).</li><li>Soules, K., Link, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphogenesis+of+the+anterior+segment+in+the+zebrafish+eye.">Morphogenesis of the anterior segment in the zebrafish eye.</a> BMC Developmental Biology. 5 (1), 12 (2005).</li><li>Greiling, T. M. S., Clark, J. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+transparent+lens+and+cornea+in+the+mouse+and+zebra+fish+eye.">The transparent lens and cornea in the mouse and zebra fish eye.</a> Seminars in Cell &#38; Developmental Biology. 19 (2), 94-99 (2008).</li><li>Greiling, T. M. S., Aose, M., Clark, J. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+Fate+and+Differentiation+of+the+Developing+Ocular+Lens.">Cell Fate and Differentiation of the Developing Ocular Lens.</a> Investigative Ophthalmology &#38; Visual Science. 51 (3), 1540-1546 (2010).</li><li>Richardson, R., Tracey-White, D., Webster, A., Moosajee, 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+zebrafish+eye-a+paradigm+for+investigating+human+ocular+genetics.">The zebrafish eye-a paradigm for investigating human ocular genetics.</a> Eye. 31, 68 (2016).</li><li>Gestri, G., Link, B. A., Neuhauss, S. C. 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+Visual+System+of+Zebrafish+and+its+Use+to+Model+Human+Ocular+Diseases.">The Visual System of Zebrafish and its Use to Model Human Ocular Diseases.</a> Developmental Neurobiology. 72 (3), 302-327 (2012).</li><li>Chhetri, J., Jacobson, G., Gueven, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish+on+the+move+towards+ophthalmological+research.">Zebrafish on the move towards ophthalmological research.</a> Eye. 28 (4), 367-380 (2014).</li><li>Lim, J. C., Walker, K. L., Sherwin, T., Schey, K. L., Donaldson, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Confocal+Microscopy+Reveals+Zones+of+Membrane+Remodeling+in+the+Outer+Cortex+of+the+Human+Lens.">Confocal Microscopy Reveals Zones of Membrane Remodeling in the Outer Cortex of the Human Lens.</a> Investigative Ophthalmology &#38; Visual Science. 50 (9), 4304-4310 (2009).</li><li>Lim, J. C., Vaghefi, E., Li, B., Nye-Wood, M. G., Donaldson, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+the+Effects+of+Hyperbaric+Oxygen+on+the+Biochemical+and+Optical+Properties+of+the+Bovine+LensEffects+of+HBO+on+the+Bovine+Lens.">Characterization of the Effects of Hyperbaric Oxygen on the Biochemical and Optical Properties of the Bovine LensEffects of HBO on the Bovine Lens.</a> Investigative Ophthalmology &#38; Visual Science. 57 (4), 1961-1973 (2016).</li><li>Gold, M. G., 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=AKAP2+anchors+PKA+with+aquaporin-0+to+support+ocular+lens+transparency.">AKAP2 anchors PKA with aquaporin-0 to support ocular lens transparency.</a> EMBO Molecular Medicine. 4 (1), 15-26 (2012).</li><li>Petrova, R. S., Schey, K. L., Donaldson, P. J., Grey, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+distributions+of+AQP5+and+AQP0+in+embryonic+and+postnatal+mouse+lens+development.">Spatial distributions of AQP5 and AQP0 in embryonic and postnatal mouse lens development.</a> Experimental Eye Research. 132, 124-135 (2015).</li><li>Chee, K. N., Vorontsova, I., Lim, J. C., Kistler, J., Donaldson, P. J. <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+the+sodium+potassium+chloride+cotransporter+(NKCC1)+and+sodium+chloride+cotransporter+(NCC)+and+their+effects+on+rat+lens+transparency.">Expression of the sodium potassium chloride cotransporter (NKCC1) and sodium chloride cotransporter (NCC) and their effects on rat lens transparency.</a> Molecular Vision. 16, 800-812 (2010).</li><li>Hayes, J. 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=Integrin+&#945;5/fibronectin1+and+focal+adhesion+kinase+are+required+for+lens+fiber+morphogenesis+in+zebrafish.">Integrin &#945;5/fibronectin1 and focal adhesion kinase are required for lens fiber morphogenesis in zebrafish.</a> Molecular Biology of the Cell. 23 (24), 4725-4738 (2012).</li><li>Imai, F., Yoshizawa, A., Fujimori-Tonou, N., Kawakami, K., Masai, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+ubiquitin+proteasome+system+is+required+for+cell+proliferation+of+the+lens+epithelium+and+for+differentiation+of+lens+fiber+cells+in+zebrafish.">The ubiquitin proteasome system is required for cell proliferation of the lens epithelium and for differentiation of lens fiber cells in zebrafish.</a> Development. 137 (19), 3257-3268 (2010).</li><li>Biswas, S. K., Lee, J. E., Brako, L., Jiang, J. X., Lo, W. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gap+junctions+are+selectively+associated+with+interlocking+ball-and-sockets+but+not+protrusions+in+the+lens.">Gap junctions are selectively associated with interlocking ball-and-sockets but not protrusions in the lens.</a> Molecular Vision. 16, 2328-2341 (2010).</li></ol>

We have no disclosures.

Analysis of zebrafish lens morphology is the initial step in understanding phenotypes in mutants, or the effects of pharmacological interventions aimed at studying biology of the ocular lens. We outline methods to analyze lens sutures, cortical fiber cell morphology and aspects of the lens nucleus. These approaches are a combination of in vitro and in vivo (compared in Table 1). The in vitro methods allow for greater detail of the outer cortical cell morphology, as well as acce...

The zebrafish is an excellent model for studying lens development and physiology due to the anatomical similarities to mammalian lenses, relative ease of genetic and pharmacological manipulation, speed of embryonic eye development, small size and transparency at early stages allowing for in vivo imaging. The methods described here were developed to analyze zebrafish lens morphology at embryonic and adult stages with a focus on sutural integrity, cortical membrane morphology in vitro and in vivo, and location of lens nuclear position along the anterior-posterior axis ex vivo. These methods serve as a starting point for functional studies of lens development and physiology, as well as reverse genetic screens for lens phenotypes in zebrafish.
Imaging zebrafish lens morphology
Aquaporin 0 (AQP0) is the most abundant lens membrane protein and is critical for both, lens development and clarity, due to multiple essential functions in mammals. Zebrafish have two Aqp0s (Aqp0a and Aqp0b) and we have developed methods to analyze loss of their functions in both embryonic and adult lenses. Our studies reveal that aqp0a-/- mutants develop anterior polar opacity due to instability of the anterior suture, and aqp0a/b double mutants develop nuclear opacity1. AQP0 has been shown to play roles in water transport2, adhesion3,4, cytoskeletal anchoring5 and generation of the refractive index gradient6, but these studies have largely been performed in vitro. The zebrafish provides a unique opportunity to study how loss of function, or perturbed function of Aqp0a or Aqp0b would affect morphology and function in a living lens. To assess lens cell morphology and sutural integrity during development, we modified existing in vitro immunohistochemical methods7 for use in embryonic and adult lenses, and generated transgenics to monitor this process in vivo.
Immunohistochemical analysis of plasma membrane structure and sutural integrity was performed in whole fixed embryos and adult lenses. Zebrafish lenses are extremely small (lens diameter is ~100 &#181;m in embryos and up to 1 mm in adults) compared with their mammalian counterparts and have point sutures8, which are infrequently captured in cryosections. Thus, whole lenses are essential for analyzing sutural integrity. For in vivo analysis of anterior suture formation, and imaging of precise lens cell architecture, we generated transgenics expressing mApple specifically labeling lens membranes.
Advantages of live imaging of lens membrane transgenics include: 1) avoiding fixation artifacts, 2) studying dynamic morphological changes in time-lapse movies, and 3) enabling longitudinal studies in which earlier events can be correlated with later phenotypes. Pigmentation of the iris normally prevents clear imaging of the lens periphery. Addition of 1-phenyl 2-thiourea (PTU) before the primordia-5 (prim-5) stage9 prevents melanogenesis and eye pigmentation up to around 4 days postfertilization (dpf). However, after 4 dpf, the lens periphery is obscured in vivo, particularly at older stages. Furthermore, the density of the lens itself obscures imaging of its posterior pole. Therefore, to study morphology of the lens periphery, or the posterior suture, after 4 dpf, lenses need to be excised and fixed.
Transgenic zebrafish lines have been used to analyze embryonic lens membrane structure in vivo10. The Q01 transgenic expresses a cyan fluorescent protein fused to a membrane targeting sequence, Gap43, driven by the EF1&#945; promoter and a hexamer of the DF4 pax6 enhancer element ubiquitously in lens fiber cells11. Q01 does have extra-lenticular expression, including amacrine cells in the retina, which adds background signal if the primary interest is the lens. We developed a novel transgenic line that expresses a membrane-tethered mApple specifically in the lens, with the aim of avoiding any extra-lenticular signal.
Lens nucleus localization
We discovered that the lens nucleus moves from an initial anterior location in larval zebrafish to a central location in the anterior-posterior axis in adult lenses. This shift in the position of the high refractive index lens nucleus is thought to be a requirement for normal development of zebrafish lens optics1. Our methods allow quantification of lens nuclear centralization in relation to the lens radius. Using this method, we showed that Aqp0a is required for lens nuclear centralization1, and this simple method can be applied to other studies of the development and physiology of the lens and its optical properties in the zebrafish model.

<table border="0" cellpadding="0" cellspacing="0" style="width:880px;" width="881">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">1-phenyl-2-thiourea (PTU)</td>
			<td style="width:196px;">Sigma</td>
			<td style="width:118px;">P7629</td>
			<td style="width:258px;">CAUTION &#8211; very toxic</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:310px;">4% Paraformaldehyde aqueous solution</td>
			<td style="width:196px;">Electron Microscopy Sciences</td>
			<td style="width:118px;">RT 157-4</td>
			<td>CAUTION &#8211; health hazard, combustible</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Confocal microscope</td>
			<td style="width:196px;">Nikon</td>
			<td style="width:118px;">Eclipse Ti-E</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:310px;">Cryostat</td>
			<td style="width:196px;">Leica</td>
			<td style="width:118px;">CM3050S</td>
			<td style="width:258px;">Objective and chamber temperature set to -21&#730;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">DAPI</td>
			<td style="width:196px;">Invitrogen</td>
			<td style="width:118px;">D1306</td>
			<td>CAUTION &#8211; irritating to eyes and skin</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:310px;">Dimethyl Sulfoxide (DMSO)</td>
			<td style="width:196px;">Fisher Scientific</td>
			<td style="width:118px;">D128</td>
			<td style="width:258px;">CAUTION &#8211; combustible, penetrates skin&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Disposable base mold</td>
			<td style="width:196px;">VWR Scientific</td>
			<td style="width:118px;">15154-631</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Disposable Pasteur glass pipets</td>
			<td style="width:196px;">Fisherbrand</td>
			<td style="width:118px;">13-678-20A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Dumont # 5 forceps</td>
			<td style="width:196px;">Dumont &#38; Fils</td>
			<td style="width:118px;"></td>
			<td>Keep forceps sharpened</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:310px;">Ethyl 3-aminobenzoate methanesulfonate salt (Tricaine)</td>
			<td style="width:196px;">Sigma-Aldrich</td>
			<td style="width:118px;">A5040</td>
			<td>CAUTION - toxic</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:310px;">Glass bottom microwell dish (35mm petri dish, 14mm microwell, #1.5 coverglass)</td>
			<td style="width:196px;">MatTek Corporation</td>
			<td style="width:118px;">P35G-1.5-14-C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Glycerol</td>
			<td style="width:196px;">Sigma</td>
			<td style="width:118px;">G2025</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">hu&#946;B1cry:mAppleCAAX DNA construct</td>
			<td style="width:196px;">Addgene</td>
			<td style="width:118px;">ID:122451</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">ImageJ</td>
			<td style="width:196px;">Wayne Rasband, NIH</td>
			<td style="width:118px;">v1.51n</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Low Melt Agarose (LMA)</td>
			<td style="width:196px;">Apex</td>
			<td style="width:118px;">902-36-6</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">NIS-Elements</td>
			<td style="width:196px;">Nikon</td>
			<td style="width:118px;">V 4.5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">NIS-Elements AR software</td>
			<td style="width:196px;">Nikon</td>
			<td style="width:118px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Olympus&#160; with a model 2.1.1.183 controller</td>
			<td style="width:196px;">Olympus Corp</td>
			<td style="width:118px;">DP70</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Olympus microscope&#160;</td>
			<td style="width:196px;">Olympus Corp</td>
			<td style="width:118px;">SZX12</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Phalloidin-Alexa Flour 546</td>
			<td style="width:196px;">Thermo Fisher</td>
			<td style="width:118px;">A22283</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Phenol Red indicator (1% w/v)</td>
			<td style="width:196px;">Ricca Chemical Company</td>
			<td style="width:118px;">5725-16</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Phosphate buffered saline (PBS)</td>
			<td style="width:196px;">Fisher Scientific</td>
			<td style="width:118px;">BP399</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:310px;">Photoshop</td>
			<td style="width:196px;">Adobe</td>
			<td style="width:118px;">CS5 v12.0</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Photoshop software</td>
			<td style="width:196px;">Adobe</td>
			<td style="width:118px;">CS5 v12.0</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plan Apo 60x/1.2 WD objective</td>
			<td style="width:196px;">Nikon</td>
			<td style="width:118px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Power source</td>
			<td style="width:196px;">Wild Heerbrugg</td>
			<td style="width:118px;">MTr 22</td>
			<td>Or equivalent power source&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Slide warmer model No. 26020FS</td>
			<td style="width:196px;">Fisher Scientific</td>
			<td style="width:118px;">12-594</td>
			<td></td>
		</tr>
		<tr height="83">
			<td height="83" style="height:83px;width:310px;">Sodium Hydroxide beads</td>
			<td style="width:196px;">Fisher Scientific</td>
			<td style="width:118px;">S612-3</td>
			<td style="width:258px;">CAUTION - corrosive/irritating to eyes and skin, target organ - respiratory system, corrosive to metals</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Superfrost/Plus microscope slide</td>
			<td style="width:196px;">Fisher Scientific</td>
			<td style="width:118px;">12-550-15</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:310px;">Sylgard 184 silicone Dow Corning</td>
			<td style="width:196px;">World Prevision Instruments</td>
			<td style="width:118px;">SYLG184</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Tissue-Tek O.C.T. Compound</td>
			<td style="width:196px;">Sakura Finetek</td>
			<td style="width:118px;">4583</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:310px;">Triton X-100 BioXtra</td>
			<td style="width:196px;">Sigma</td>
			<td style="width:118px;">T9284</td>
			<td style="width:258px;">CAUTION &#8211; Toxic, hazardous to aquatic environment, corrosive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Vannas micro-dissection scissors</td>
			<td style="width:196px;">Ted Pella Inc</td>
			<td style="width:118px;">1346</td>
			<td>Sharp/sharp straight tips</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:310px;">Vectashield antifade mouting medium</td>
			<td style="width:196px;">Vector laboratories</td>
			<td style="width:118px;">H-1000</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:310px;">Wheat Germ Agglutinin (WGA)-Alexa Flour-594</td>
			<td style="width:196px;">Life Technologies</td>
			<td style="width:118px;">W11262</td>
			<td></td>
		</tr>
	</tbody>
</table>

assessment of zebrafish lens nucleus localization and sutural integrity

The zebrafish is uniquely suited to genetic manipulation and in vivo imaging, making it an increasingly popular model for reverse genetic studies and for generation of transgenics for in vivo imaging. These unique capabilities make the zebrafish an ideal platform to study ocular lens development and physiology. Our recent findings that an Aquaporin-0, Aqp0a, is required for stability of the anterior lens suture, as well as for the shift of the lens nucleus to the lens center with age led us to develop tools especially suited to analyzing the properties of zebrafish lenses. Here we outline detailed methods for lens dissection that can be applied to both larval and adult lenses, to prepare them for histological analysis, immunohistochemistry and imaging. We focus on analysis of lens suture integrity and cortical cell morphology and compare data generated from dissected lenses with data obtained from in vivo imaging of lens morphology made possible by a novel transgenic zebrafish line with a genetically encoded fluorescent marker. Analysis of dissected lenses perpendicular to their optical axis allows quantification of the relative position of the lens nucleus along the anterior-posterior axis. Movement of the lens nucleus from an initial anterior position to the center is required for normal lens optics in adult zebrafish. Thus, a quantitative measure of lens nuclear position directly correlates with its optical properties.

Adult zebrafish eye anatomy closely resembles that of mammals (Figure 1A). Despite some differences between zebrafish and mammalian eyes, such as having a ciliary zone instead of a ciliary body17, differences in optical properties18, and differences in morphogenesis during embryonic development19, the zebrafish eye is an excellent model for studying eye development and understanding ophth...

Watch this Scientific Journal Video about Assessment of Zebrafish Lens Nucleus Localization and Sutural Integrity at JoVE.com

Assessment of Zebrafish Lens Nucleus Localization and Sutural Integrity

These protocols were developed to analyze cortical lens morphology, structural integrity of the zebrafish lens sutures in fixed and live lenses and to measure the position of the zebrafish lens nucleus along the anterior-posterior axis.

The zebrafish is uniquely suited to genetic manipulation and in vivo imaging, making it an increasingly popular model for reverse genetic studies and for ...

assessment-zebrafish-lens-nucleus-localization-sutural

Universidad de Cartagena UDEC

Research

JoVE Journal

Biology

8.5K Views.  University of California, Irvine. These protocols were developed to analyze cortical lens morphology, structural integrity of the zebrafish lens sutures in fixed and live lenses and to measure the position of the zebrafish lens nucleus along the anterior-posterior axis.

Video: Assessment of Zebrafish Lens Nucleus Localization and Sutural Integrity

Lens Transplantation in Zebrafish and its Application in the Analysis of Eye Mutants

The lens plays an important role in the development of the optic cup[1,2]. Using the zebrafish as a model organism, questions regarding lens development can be addressed. The zebrafish is useful for genetic studies due to several advantageous characteristics, including small size, high fecundity, short lifecycle, and ease of care. Lens development occurs rapidly in zebrafish. By 72 hpf, the zebrafish lens is functionally mature [3]. Abundant genetic and molecular resources are available to support research in zebrafish. In addition, the similarity of the zebrafish eye to those of other vertebrates provides basis for its use as an excellent animal model of human defects[4-7]. Several zebrafish mutants exhibit lens abnormalities, including high levels of cell death, which in some cases leads to a complete degeneration of lens tissues [8]. To determine whether lens abnormalities are due to intrinsic causes or to defective interactions with the surrounding tissues, transplantation of a mutant lens into a wild-type eye is performed. Using fire-polished metal needles, mutant or wild-type lenses are carefully dissected from the donor animal, and transferred into the host. To distinguish wild-type and mutant tissues, a transgenic line is used as the donor. This line expresses membrane-bound GFP in all tissues, including the lens. This transplantation technique is an essential tool in the studies of zebrafish lens mutants.

Lens development involves interactions with other tissues. Several zebrafish eye mutants are characterized by an abnormally small lens size. Here we demonstrate a lens transplantation experiment to determine whether this phenotype is due to intrinsic causes or defective interactions with tissues that surround the lens.

The lens plays an important role in the development of the optic cup[1,2]. Using the zebrafish as a model organism, questions regarding lens development ...

Preparation and Culture of Rat Lens Epithelial Explants for Studying Terminal Differentiation

The anterior surface of the ocular lens is covered by a monolayer of epithelial cells, which proliferate in an annular zone underlying the ciliary body.  Following division, these cells migrate posteriorly, where FGF diffusing from the retina induces them to differentiate into a posterior array of elongated lens fiber cells, which compose the bulk of the lens.  Differentiation of lens epithelial cells into lens fibers can be induced in vitro by culturing explants of the central region of the anterior epithelium in the presence of FGF-2.  Explants are prepared from lenses of neonatal rats by removing the lens from the eye and grasping the lens capsule on the posterior side with dissecting tweezers.  The posterior capsule is then gently torn open and pressed down into the plastic bottom of a tissue culture dish. The peripheral regions of the explant are removed with a scalpel and the central area is then cultured in the presence of 100ng/ml FGF-2 for as long as 2-3 weeks, depending on the parameters to be studied.  Since epithelial cells in cultured explants differentiate in approximate synchrony over a period of days to weeks, the time course of signaling and gene expression can be determined using molecular, biochemical, and pharmacological techniques.  Immunofluorescence microscopy is a powerful adjunct to these methods as it demonstrates the subcellular localization of proteins of interest and can reveal the physiological consequences of experimental manipulations of signaling pathways.

Explants of the central region of rat lens epithelia differentiate synchronously when cultured in the presence of FGF-2. Immunofluorescence microscopy of such cultures can provides novel information about gene expression and signaling events associated with terminal differentiation.

The anterior surface of the ocular lens is covered by a monolayer of epithelial cells, which proliferate in an annular zone underlying the ciliary body.  ...

Heterokaryon Technique for Analysis of Cell Type-specific Localization

A significant number of proteins are regulated by subcellular trafficking or nucleocytolasmic shuttling. These proteins display a diverse array of cellular functions including nuclear import/export of RNA and protein, transcriptional regulation, and apoptosis. Interestingly, major cellular reorganizations including cell division, differentiation and transformation, often involve such activities3,4,8,10. The detailed study of these proteins and their respective regulatory mechanisms can be challenging as the stimulation for these localization changes can be elusive, and the movements themselves can be quite dynamic and difficult to track. Studies involving cellular oncogenesis, for example, continue to benefit from understanding pathways and protein activities that differ between normal primary cells and transformed cells6,7,11,12. As many proteins show altered localization during transformation or as a result of transformation, methods to efficiently characterize these proteins and the pathways in which they participate stand to improve the understanding of oncogenesis and open new areas for drug targeting.
Here we present a method for the analysis of protein trafficking and shuttling activity between primary and transformed mammalian cells. This method combines the generation of heterokaryon fusions with fluorescence microscopy to provide a flexible protocol that can be used to detect steady-state or dynamic protein localizations. As shown in Figure 1, two separate cell types are transiently transfected with plasmid constructs bearing a fluoroprotein gene attached to the gene of interest. After expression, the cells are fused using polyethylene glycol, and protein localizations may then be imaged using a variety of methods. The protocol presented here is a fundamental approach to which specialized techniques may be added.

A flexible and efficient method for the characterization of cell type-specific protein localization and nucleocytoplasmic shuttling is described. This heterokaryon approach uses fluorescently-labeled fusion proteins to image protein localizations after cell fusion. The protocol is amenable to steady-state localizations or more dynamic determinations based on live cell imaging.

A significant number of proteins are regulated by subcellular trafficking or nucleocytolasmic shuttling.  These proteins display a diverse array of ...

In vivo Electroporation of Morpholinos into the Adult Zebrafish Retina

Many devastating inherited eye diseases result in progressive and irreversible blindness because humans cannot regenerate dying or diseased retinal neurons. In contrast, the adult zebrafish retina possesses the robust ability to spontaneously regenerate any neuronal class that is lost in a variety of different retinal damage models, including retinal puncture, chemical ablation, concentrated high temperature, and intense light treatment 1-8. Our lab extensively characterized regeneration of photoreceptors following constant intense light treatment and inner retinal neurons after intravitreal ouabain injection 2, 5, 9. In all cases, resident M&uuml;ller glia re-enter the cell cycle to produce neuronal progenitors, which continue to proliferate and migrate to the proper retinal layer, where they differentiate into the deficient neurons. 
	We characterized five different stages during regeneration of the light-damaged retina that were highlighted by specific cellular responses. We identified several differentially expressed genes at each stage of retinal regeneration by mRNA microarray analysis 10. Many of these genes are also critical for ocular development. To test the role of each candidate gene/protein during retinal regeneration, we needed to develop a method to conditionally limit the expression of a candidate protein only at times during regeneration of the adult retina. 
	Morpholino oligos are widely used to study loss of function of specific proteins during the development of zebrafish, Xenopus, chick, mouse, and tumors in human xenografts 11-14. These modified oligos basepair with complementary RNA sequence to either block the splicing or translation of the target RNA. Morpholinos are stable in the cell and can eliminate or "knockdown" protein expression for three to five days 12. 
	Here, we describe a method to efficiently knockdown target protein expression in the adult zebrafish retina. This method employs lissamine-tagged antisense morpholinos that are injected into the vitreous of the adult zebrafish eye. Using electrode forceps, the morpholino is then electroporated into all the cell types of the dorsal and central retina. Lissamine provides the charge on the morpholino for electroporation and can be visualized to assess the presence of the morpholino in the retinal cells. 
	Conditional knockdown in the retina can be used to examine the role of specific proteins at different times during regeneration. Additionally, this approach can be used to study the role of specific proteins in the undamaged retina, in such processes as visual transduction and visual processing in second order neurons.

In vivo Electroporation of Morpholinos into the Adult Zebrafish Retina

A method to conditionally knockdown a target protein&#x2019;s expression in the adult zebrafish retina is described, which involves intravitreally injecting antisense morpholinos and electroporating them into the retina. The resulting protein is knocked down for several days, which allows testing the protein&#x2019;s role in the regenerating or intact retina.

Many devastating inherited eye diseases result in progressive and irreversible blindness because humans cannot regenerate dying or diseased retinal ...

In vivo Electroporation of Morpholinos into the Regenerating Adult Zebrafish Tail Fin

Certain species of urodeles and teleost fish can regenerate their tissues. Zebrafish have become a widely used model to study the spontaneous regeneration of adult tissues, such as the heart1, retina2, spinal cord3, optic nerve4, sensory hair cells5, and fins6.
The zebrafish fin is a relatively simple appendage that is easily manipulated to study multiple stages in epimorphic regeneration. Classically, fin regeneration was characterized by three distinct stages: wound healing, blastema formation, and fin outgrowth. After amputating part of the fin, the surrounding epithelium proliferates and migrates over the wound. At 33 &deg;C, this process occurs within six hours post-amputation (hpa, Figure 1B)6,7. Next, underlying cells from different lineages (ex. bone, blood, glia, fibroblast) re-enter the cell cycle to form a proliferative blastema, while the overlying epidermis continues to proliferate (Figure 1D)8. Outgrowth occurs as cells proximal to the blastema re-differentiate into their respective lineages to form new tissue (Figure 1E)8. Depending on the level of the amputation, full regeneration is completed in a week to a month.
The expression of a large number of gene families, including wnt, hox, fgf, msx, retinoic acid, shh, notch, bmp, and activin-betaA genes, is up-regulated during specific stages of fin regeneration9-16. However, the roles of these genes and their encoded proteins during regeneration have been difficult to assess, unless a specific inhibitor for the protein exists13, a temperature-sensitive mutant exists or a transgenic animal (either overexpressing the wild-type protein or a dominant-negative protein) was generated7,12. We developed a reverse genetic technique to quickly and easily test the function of any gene during fin regeneration.
Morpholino oligonucleotides are widely used to study loss of specific proteins during zebrafish, Xenopus, chick, and mouse development17-19. Morpholinos basepair with a complementary RNA sequence to either block pre-mRNA splicing or mRNA translation. We describe a method to efficiently introduce fluorescein-tagged antisense morpholinos into regenerating zebrafish fins to knockdown expression of the target protein. The morpholino is micro-injected into each blastema of the regenerating zebrafish tail fin and electroporated into the surrounding cells. Fluorescein provides the charge to electroporate the morpholino and to visualize the morpholino in the fin tissue.
This protocol permits conditional protein knockdown to examine the role of specific proteins during regenerative fin outgrowth. In the Discussion, we describe how this approach can be adapted to study the role of specific proteins during wound healing or blastema formation, as well as a potential marker of cell migration during blastema formation.

In vivo Electroporation of Morpholinos into the Regenerating Adult Zebrafish Tail Fin

We describe a method to conditionally knockdown the expression of a target protein during adult zebrafish fin regeneration. This technique involves micro-injecting and electroporating antisense oligonucleotide morpholinos into fin tissue, which allows testing the protein&#x2019;s role in various stages of fin regeneration, including wound healing, blastema formation, and regenerative outgrowth.

Certain species of urodeles and teleost fish can regenerate their tissues. Zebrafish have become a widely used model to study the spontaneous regeneration ...

Nano-fEM: Protein Localization Using Photo-activated Localization Microscopy and Electron Microscopy

Mapping the distribution of proteins is essential for understanding the function of proteins in a cell. Fluorescence microscopy is extensively used for protein localization, but subcellular context is often absent in fluorescence images. Immuno-electron microscopy, on the other hand, can localize proteins, but the technique is limited by a lack of compatible antibodies, poor preservation of morphology and because most antigens are not exposed to the specimen surface. Correlative approaches can acquire the fluorescence image from a whole cell first, either from immuno-fluorescence or genetically tagged proteins. The sample is then fixed and embedded for electron microscopy, and the images are correlated 1-3. However, the low-resolution fluorescence image and the lack of fiducial markers preclude the precise localization of proteins. 
Alternatively, fluorescence imaging can be done after preserving the specimen in plastic. In this approach, the block is sectioned, and fluorescence images and electron micrographs of the same section are correlated 4-7. However, the diffraction limit of light in the correlated image obscures the locations of individual molecules, and the fluorescence often extends beyond the boundary of the cell. 
Nano-resolution fluorescence electron microscopy (nano-fEM) is designed to localize proteins at nano-scale by imaging the same sections using photo-activated localization microscopy (PALM) and electron microscopy. PALM overcomes the diffraction limit by imaging individual fluorescent proteins and subsequently mapping the centroid of each fluorescent spot 8-10. 
We outline the nano-fEM technique in five steps. First, the sample is fixed and embedded using conditions that preserve the fluorescence of tagged proteins. Second, the resin blocks are sectioned into ultrathin segments (70-80 nm) that are mounted on a cover glass. Third, fluorescence is imaged in these sections using the Zeiss PALM microscope. Fourth, electron dense structures are imaged in these same sections using a scanning electron microscope. Fifth, the fluorescence and electron micrographs are aligned using gold particles as fiducial markers. In summary, the subcellular localization of fluorescently tagged proteins can be determined at nanometer resolution in approximately one week.

We describe a method to localize fluorescently tagged proteins in electron micrographs. Fluorescence is first localized using photo-activated localization microscopy on ultrathin sections. These images are then aligned to electron micrographs of the same section.

Mapping the distribution of proteins is essential for understanding the function of proteins in a cell. Fluorescence microscopy is extensively used for ...

Analysis of LINE-1 Retrotransposition at the Single Nucleus Level

Long interspersed nuclear element-1 (Line-1 or L1) accounts for approximately 17% of the DNA present in the human genome. While the majority of L1s are inactive due to 5' truncations, ~80-100 of these elements remain retrotransposition competent and propagate to different locations throughout the genome via RNA intermediates. While older L1s are believed to target AT rich regions of the genome, the chromosomal targets of newer, more active L1s remain poorly defined. Here we describe fluorescence in situ hybridization (FISH) methodology that can be used to track patterns of L1 insertion and rates of ectopic L1 incorporation at the single nucleus level. In these experiments, fluorescein isothiocyanate/cyanine-3 (FITC/CY3) labeled neomycin probes were employed to track L1 retrotransposition in vitro in HepG2 cells stably expressing ectopic L1. This methodology prevents errors in the estimation of rates of retrotransposition posed by toxicity and account for the occurrence of multiple insertions into a single nucleus.

Here we employ FISH methodology to track LINE-1 retrotransposition at the single nuclei level in chromosome spreads of HepG2 cell lines stably expressing synthetic LINE-1.

Long interspersed nuclear element-1 (Line-1 or L1) accounts for approximately 17% of the DNA present in the human genome. While the majority of L1s are ...

Nephrotoxin Microinjection in Zebrafish to Model Acute Kidney Injury

The kidneys are susceptible to harm from exposure to chemicals they filter from the bloodstream. This can lead to organ injury associated with a rapid decline in renal function and development of the clinical syndrome known as acute kidney injury (AKI). Pharmacological agents used to treat medical circumstances ranging from bacterial infection to cancer, when administered individually or in combination with other drugs, can initiate AKI. Zebrafish are a useful animal model to study the chemical effects on renal function in vivo, as they form an embryonic kidney comprised of nephron functional units that are conserved with higher vertebrates, including humans. Further, zebrafish can be utilized to perform genetic and chemical screens, which provide opportunities to elucidate the cellular and molecular facets of AKI and develop therapeutic strategies such as the identification of nephroprotective molecules. Here, we demonstrate how microinjection into the zebrafish embryo can be utilized as a paradigm for nephrotoxin studies.

Renal injuries incurred from nephrotoxins, which include drugs ranging from antibiotics to chemotherapeutics, can result in complex disorders whose pathogenesis remains incompletely understood. This protocol demonstrates how zebrafish can be used for disease modeling of these conditions, which can be applied to the identification of renoprotective measures.

The kidneys are susceptible to harm from exposure to chemicals they filter from the bloodstream. This can lead to organ injury associated with a rapid ...

Lens-free Video Microscopy for the Dynamic and Quantitative Analysis of Adherent Cell Culture

Here, we demonstrate that lens-free video microscopy enables us to simultaneously capture the kinetics of thousands of cells directly inside the incubator and that it is possible to monitor and quantify single cells along several cell cycles. We describe the full protocol used to monitor and quantify a HeLa cell culture for 2.7 days. First, cell culture acquisition is performed with a lens-free video microscope, and then the data is analyzed following a four-step process: multi-wavelength holographic reconstruction, cell-tracking, cell segmentation and cell division detection algorithms. As a result, we show that it is possible to gather a dataset featuring more than 10,000 cell cycle tracks and more than 2 x 106 cell morphological measurements.

Lens-free video microscopy enables us to monitor cell cultures directly inside the incubator. Here we describe the full protocol used to acquire and analyze a 2.7 day long acquisition of cultured HeLa cells, leading to a dataset of 2.2 x 106 measurements of individual cell morphology and 10584 cell cycle tracks.

Here, we demonstrate that lens-free video microscopy enables us to simultaneously capture the kinetics of thousands of cells directly inside the incubator ...

Studying Ribonucleotide Incorporation: Strand-specific Detection of Ribonucleotides in the Yeast Genome and Measuring Ribonucleotide-induced Mutagenesis

The presence of ribonucleotides in nuclear DNA has been shown to be a source of genomic instability. The extent of ribonucleotide incorporation can be assessed by alkaline hydrolysis and gel electrophoresis as RNA is highly susceptible to hydrolysis in alkaline conditions. This, in combination with Southern blot analysis can be used to determine the location and strand into which the ribonucleotides have been incorporated. However, this procedure is only semi-quantitative and may not be sensitive enough to detect small changes in ribonucleotide content, although strand-specific Southern blot probing improves the sensitivity. As a measure of one of the most striking biological consequences of ribonucleotides in DNA, spontaneous mutagenesis can be analyzed using a forward mutation assay. Using appropriate reporter genes, rare mutations that results in the loss of function can be selected and overall and specific mutation rates can be measured by combining data from fluctuation experiments with DNA sequencing of the reporter gene. The fluctuation assay is applicable to examine a wide variety of mutagenic processes in specific genetic background or growth conditions.

Ribonucleotides are among the most abundant non-canonical nucleotides incorporated into the genome during eukaryotic nuclear DNA replication. If not properly removed, ribonucleotides can cause DNA damage and mutagenesis. Here, we present two experimental approaches that are used to assess the abundance of ribonucleotide incorporation into DNA and its mutagenic effects.

The presence of ribonucleotides in nuclear DNA has been shown to be a source of genomic instability. The extent of ribonucleotide incorporation can be ...

Assessment of Zebrafish Lens Nucleus Localization and Sutural Integrity

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Chapters in this video

Lens Transplantation in Zebrafish and its Application in the Analysis of Eye Mutants

Preparation and Culture of Rat Lens Epithelial Explants for Studying Terminal Differentiation

Heterokaryon Technique for Analysis of Cell Type-specific Localization

In vivo Electroporation of Morpholinos into the Adult Zebrafish Retina

In vivo Electroporation of Morpholinos into the Regenerating Adult Zebrafish Tail Fin

Nano-fEM: Protein Localization Using Photo-activated Localization Microscopy and Electron Microscopy

Analysis of LINE-1 Retrotransposition at the Single Nucleus Level

Nephrotoxin Microinjection in Zebrafish to Model Acute Kidney Injury

Lens-free Video Microscopy for the Dynamic and Quantitative Analysis of Adherent Cell Culture

Studying Ribonucleotide Incorporation: Strand-specific Detection of Ribonucleotides in the Yeast Genome and Measuring Ribonucleotide-induced Mutagenesis