Name: using fluorescence in situ hybridization (fish) to monitor the state of arm cohesion in prometaphase and metaphase i drosophila oocytes
Uploaded: 2017-12-06T15:00:00
Description: Watch this Scientific Journal Video about Using Fluorescence In Situ Hybridization FISH to Monitor the State of Arm Cohesion in Prometaphase and Metaphase I Drosophila Oocytes at JoVE.com

This work was supported by NIH Grant GM59354 awarded to Sharon E. Bickel. We thank Huy Q. Nguyen for assistance in developing the protocol for generating fluorescent arm probes, Ann Lavanway for help with confocal microscopy, and J. Emiliano Reed for technical assistance. We also thank numerous colleagues in the Drosophila community for helpful discussions and advice.

1. Preparations
<ol>
	<li>Prepare solutions for fluorescence in situ hybridization (FISH). Prepare all solutions using ultrapure water.
	<ol>
		<li>Prepare 5x&#160;Modified Robb&#39;s buffer: 275 mM potassium acetate, 200 mM sodium acetate, 500 mM sucrose, 50 mM glucose, 6 mM magnesium chloride, 5 mM calcium chloride, 500 mM HEPES pH = 7.4. Bring the pH to 7.4 using 10 N NaOH. Filter sterilize and store at -20 &#176;C. Thaw and dilute to 1x&#160;as needed and store 1x&#160;aliquots at -20 &#17...

<ol>
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B., 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=Disjunction+of+homologous+chromosomes+in+meiosis+I+depends+on+proteolytic+cleavage+of+the+meiotic+cohesin+Rec8+by+separin.">Disjunction of homologous chromosomes in meiosis I depends on proteolytic cleavage of the meiotic cohesin Rec8 by separin.</a> Cell. 103 (3), 387-398 (2000).</li><li>Bickel, S. E., Orr-Weaver, T., Balicky, E. 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+sister-chromatid+cohesion+protein+ORD+is+required+for+chiasma+maintenance+in+Drosophila+oocytes.">The sister-chromatid cohesion protein ORD is required for chiasma maintenance in Drosophila oocytes.</a> Curr. Biol. 12 (11), 925-929 (2002).</li><li>Hodges, C. A., Revenkova, E., Jessberger, R., Hassold, T. J., Hunt, P. 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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defective+cohesin+is+associated+with+age-dependent+misaligned+chromosomes+in+oocytes.">Defective cohesin is associated with age-dependent misaligned chromosomes in oocytes.</a> Reprod Biomed Online. 16 (1), 103-112 (2008).</li><li>Subramanian, V. V., Bickel, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aging+predisposes+oocytes+to+meiotic+nondisjunction+when+the+cohesin+subunit+SMC1+is+reduced.">Aging predisposes oocytes to meiotic nondisjunction when the cohesin subunit SMC1 is reduced.</a> PLoS Genet. 4 (11), e1000263 (2008).</li><li>Chiang, T., Duncan, F. E., Schindler, K., Schultz, R. M., Lampson, M. 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The use of FISH probes to assess the state of arm cohesion in prometaphase I and metaphase I Drosophila oocytes is a significant advancement in the field of Drosophila meiosis. Historically, Drosophila researchers have been limited to genetic tests to infer premature loss of arm cohesion in mature oocytes11,18,19. Now, with the methods presented here, the state of arm cohesion can be assayed directly u...

Proper segregation of chromosomes during mitosis and meiosis requires that sister chromatid cohesion be established, maintained, and released in a coordinated fashion1,2. Cohesion is established during S phase and is mediated by the cohesin complex, which forms physical linkages that hold the sister chromatids together. In meiosis, cohesion distal to a crossover also functions to hold recombinant homologs together and this physical association helps ensure proper orientation of the bivalent on the metaphase I spindle (Figure 1)3,4,5. Release of arm cohesion at anaphase I allows the homologs to segregate to opposite spindle poles. However, if arm cohesion is lost prematurely, recombinant homologs will lose their physical connection and segregate randomly, which can result in aneuploid gametes (Figure 1).
In human oocytes, errors in chromosome segregation are the leading cause of miscarriages and birth defects, such as Down Syndrome6, and their incidence increases exponentially with maternal age7. Sister chromatid cohesion is established in fetal oocytes and meiotic recombination is completed before birth. Oocytes then arrest in mid-prophase I until ovulation and during this arrest, the continued physical association of recombinant homologs relies on sister chromatid cohesion. Therefore, accurate segregation during meiosis and normal pregnancy outcomes require that cohesion remain intact for up to five decades.
Premature loss of cohesion during the prolonged meiotic arrest of human oocytes has been proposed to contribute to the maternal age effect and multiple lines of evidence support this hypothesis8,9. However, given the challenges of studying meiotic cohesion in human oocytes, much of our understanding of this phenomenon relies on the use of model organisms5,10,11,12,13,14,15.
Drosophila melanogaster oocytes offer numerous advantages for the study of meiotic cohesion and chromosome segregation. A simple genetic assay allows one to recover progeny from aneuploid gametes and measure the fidelity of X-chromosome segregation on a large scale11,16,17. Moreover, one may also determine whether chromosome segregation errors arise because recombinant homologs missegregate during meiosis I, a phenotype that is consistent with premature loss of arm cohesion11,18,19. Direct observation of the state of meiotic cohesion in Drosophila oocytes is also possible using fluorescence in situ hybridization (FISH). Although fluorescent oligonucleotides that hybridize to repetitive satellite sequences have been used for over a decade to monitor pericentromeric cohesion in mature Drosophila oocytes4,20, analysis of arm cohesion has been much more challenging. Visualization of the state of arm cohesion requires a probe that spans a large region of single copy sequences and is bright enough to result in visible signals for individual sister chromatids when arm cohesion is absent. In addition, the oocyte fixation conditions and size of the labeled DNAs must facilitate penetration21 into the large mature Drosophila oocyte (200 &#181;m wide by 500 &#181;m long). Recently, an arm probe was successfully utilized to visualize Drosophila oocyte chromatids during anaphase I, but the authors stated that they could not detect a signal in prometaphase or metaphase I arrested oocytes22. Here we provide a detailed protocol for the generation of X-chromosome arm FISH probes and oocyte preparation conditions that have allowed us to assay for premature loss of sister chromatid cohesion in prometaphase I and metaphase I oocytes. These techniques, which have enabled us to identify gene products that are required for the maintenance of meiotic cohesion, will allow others to assay for sister chromatid cohesion defects in mature Drosophila oocytes of different genotypes.

<table>
	<tbody>
		<tr>
			<td>Kits</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Midi Prep kit</td>
			<td>Qiagen</td>
			<td>12143</td>
			<td>Prep BAC clone DNA</td>
		</tr>
		<tr>
			<td>GenomePlex Complete Whole Genome Amplification (WGA) Kit</td>
			<td>Sigma</td>
			<td>WGA2</td>
			<td>Amplify BAC clone DNA</td>
		</tr>
		<tr>
			<td>ARES Alexa Fluor 647 DNA labeling kit</td>
			<td>Invitrogen</td>
			<td>A21676</td>
			<td>Label BAC clone DNA</td>
		</tr>
		<tr>
			<td>PCR purification kit</td>
			<td>Qiagen</td>
			<td>28104</td>
			<td>Remove non-conjugated dye following labeling of BAC clone DNA</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Chemicals &#38; Solutions</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Note: All solutions are prepared using sterile ultrapure water and should be sterilized either by autoclave or filter sterilization.</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin (BSA)</td>
			<td>Fisher Scientific</td>
			<td>BP1600-100</td>
			<td>Prepare 10% stock 
			Freeze aliquots</td>
		</tr>
		<tr>
			<td>Calcium chloride</td>
			<td>Fisher Scientific</td>
			<td>C75-500</td>
			<td></td>
		</tr>
		<tr>
			<td>DAPI (4&#8217;, 6-Diamidino-2-Phenylindole, Dihydrochloride)</td>
			<td>Invitrogen</td>
			<td>D1306</td>
			<td>Toxic: wear appropriate protection. Prepare 100&#181;g/ml stock in 100% ethanol, store in aliquots at -20 &#176;C. Prepare 1 &#181;g/ml solution in 2X SSCT before use.</td>
		</tr>
		<tr>
			<td>Dextran sulfate</td>
			<td>Sigma</td>
			<td>D-8906</td>
			<td></td>
		</tr>
		<tr>
			<td>Drierite</td>
			<td>Drierite Company</td>
			<td>23001</td>
			<td></td>
		</tr>
		<tr>
			<td>Dithiothreitol (DTT)</td>
			<td>Invitrogen</td>
			<td>15508-013</td>
			<td>Prepare 10 mM stock</td>
		</tr>
		<tr>
			<td>dTTP (10 &#181;mol, 100 &#181;l)</td>
			<td>Boehringer Mannheim</td>
			<td>1277049</td>
			<td>Prepare 1 mM stock</td>
		</tr>
		<tr>
			<td>EDTA (Disodium ethylenediamine tetraacetic acid)</td>
			<td>Fisher Scientific</td>
			<td>S311-500</td>
			<td>Prepare 250 mM stock</td>
		</tr>
		<tr>
			<td>100% ethanol (molecular grade, 200 proof)</td>
			<td>Decon Laboratories</td>
			<td>2716</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris (Ultra Pure)</td>
			<td>Invitrogen</td>
			<td>15504-020</td>
			<td></td>
		</tr>
		<tr>
			<td>EGTA (Ethylenebis(oxyethylenenitrilo)tetraacetic acid)</td>
			<td>Sigma</td>
			<td>E-3889</td>
			<td></td>
		</tr>
		<tr>
			<td>16% formaldehyde</td>
			<td>Ted Pella, Inc.</td>
			<td>18505</td>
			<td>Toxic: wear appropriate protection</td>
		</tr>
		<tr>
			<td>Formamide</td>
			<td>Invitrogen</td>
			<td>AM9342</td>
			<td>Toxic: wear appropriate protection</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Fisher Scientific</td>
			<td>D16-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycogen</td>
			<td>Roche</td>
			<td>901393</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Boehringer Mannheim</td>
			<td>737-151</td>
			<td></td>
		</tr>
		<tr>
			<td>Heptane</td>
			<td>Fisher Scientific</td>
			<td>H350-4</td>
			<td>Toxic: wear appropriate protection.</td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>Millipore</td>
			<td>HX0603-4</td>
			<td>Toxic: wear appropriate protection.</td>
		</tr>
		<tr>
			<td>Hydroxylamine</td>
			<td>Sigma</td>
			<td>438227</td>
			<td>Prepare 3 M stock</td>
		</tr>
		<tr>
			<td>4.9 M Magnesium chloride</td>
			<td>Sigma</td>
			<td>104-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Na2HPO4 &#376; 7H2O</td>
			<td>Fisher Scientific</td>
			<td>S373-500</td>
			<td></td>
		</tr>
		<tr>
			<td>NaH2PO4 &#376; 2H2O</td>
			<td>Fisher Scientific</td>
			<td>S369-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-L-lysine (0.1mg/ml)</td>
			<td>Sigma</td>
			<td>P8920-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium acetate</td>
			<td>Fisher Scientific</td>
			<td>BP364-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium acetate</td>
			<td>Fisher Scientific</td>
			<td>S209-500</td>
			<td>Prepare 3M stock</td>
		</tr>
		<tr>
			<td>Sodium cacodylate</td>
			<td>Polysciences, Inc.</td>
			<td>1131</td>
			<td>Toxic: wear appropriate protection. Prepare 400mM stock</td>
		</tr>
		<tr>
			<td>Sodium citrate</td>
			<td>Fisher Scientific</td>
			<td>BP327-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Fisher Scientific</td>
			<td>S271-3</td>
			<td>Sodium chloride</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Fisher Scientific</td>
			<td>S5-500</td>
			<td></td>
		</tr>
		<tr>
			<td>10% Tween 20</td>
			<td>Thermo Scientific</td>
			<td>28320</td>
			<td>Surfact-Amps</td>
		</tr>
		<tr>
			<td>10% Triton X-100</td>
			<td>Thermo Scientific</td>
			<td>28314</td>
			<td>Surfact-Amps</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Solutions</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Note: All solutions are prepared using sterile ultrapure water and should be sterilized either by autoclave or filter sterilization.</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>TE buffer</td>
			<td></td>
			<td></td>
			<td>10 mM Tris, 1 mM EDTA, pH = 8.0</td>
		</tr>
		<tr>
			<td>20X SSC (Saline Sodium Citrate)</td>
			<td></td>
			<td></td>
			<td>3 M NaCl, 300 mM sodium citrate</td>
		</tr>
		<tr>
			<td>2X cacodylate fix solution</td>
			<td></td>
			<td></td>
			<td>Toxic: wear appropriate protection. 200 mM sodium cacodylate, 200 mM sucrose, 80 mM sodium acetate, 20 mM EGTA</td>
		</tr>
		<tr>
			<td>1.1X Hybridization buffer</td>
			<td></td>
			<td></td>
			<td>3.3X SSC, 55% formamide, 11% dextran sulfate</td>
		</tr>
		<tr>
			<td>Fix solution</td>
			<td></td>
			<td></td>
			<td>Toxic: wear appropriate protection. 4% formaldehyde, 1X cacodylate fix solution</td>
		</tr>
		<tr>
			<td>PBSBTx</td>
			<td></td>
			<td></td>
			<td>1X PBS, 0.5% BSA, 0.1% Trition X-100</td>
		</tr>
		<tr>
			<td>PBSTx</td>
			<td></td>
			<td></td>
			<td>1X PBS, 1% Trition X-100</td>
		</tr>
		<tr>
			<td>Extraction buffer (PBSTx + Rnase)</td>
			<td></td>
			<td></td>
			<td>1X PBS, 1% Trition X-100, 100 &#181;g/mL RNase</td>
		</tr>
		<tr>
			<td>2X SSCT</td>
			<td></td>
			<td></td>
			<td>2X SSC, 0.1% Tween 20</td>
		</tr>
		<tr>
			<td>2X SSCT + 20% formamide</td>
			<td></td>
			<td></td>
			<td>Toxic: wear appropriate protection. 2X SSC, 0.1% Tween 20, 20% formamide</td>
		</tr>
		<tr>
			<td>2X SSCT + 40% formamide</td>
			<td></td>
			<td></td>
			<td>Toxic: wear appropriate protection. 2X SSC, 0.1% Tween 20, 40% formamide</td>
		</tr>
		<tr>
			<td>2X SSCT + 50% formamide</td>
			<td></td>
			<td></td>
			<td>Toxic: wear appropriate protection. 2X SSC, 0.1% Tween 20, 50% formamide</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Enzymes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>AluI</td>
			<td>New England Biolabs</td>
			<td>R0137S</td>
			<td></td>
		</tr>
		<tr>
			<td>HaeIII</td>
			<td>New England Biolabs</td>
			<td>R0108S</td>
			<td></td>
		</tr>
		<tr>
			<td>MseI</td>
			<td>New England Biolabs</td>
			<td>R0525S</td>
			<td></td>
		</tr>
		<tr>
			<td>MspI</td>
			<td>New England Biolabs</td>
			<td>R0106S</td>
			<td></td>
		</tr>
		<tr>
			<td>RsaI</td>
			<td>New England Biolabs</td>
			<td>R0167S</td>
			<td></td>
		</tr>
		<tr>
			<td>BfuCI</td>
			<td>New England Biolabs</td>
			<td>R0636S</td>
			<td></td>
		</tr>
		<tr>
			<td>100X BSA</td>
			<td>New England Biolabs</td>
			<td></td>
			<td>Comes with NEB enzymes</td>
		</tr>
		<tr>
			<td>10X NEB buffer #2</td>
			<td>New England Biolabs</td>
			<td></td>
			<td>Restriction enzyme digestion buffer. Comes with NEB enzymes</td>
		</tr>
		<tr>
			<td>Terminal deoxynucleotidyl transferase (TdT) 400 U/&#181;l</td>
			<td>Roche/Sigma</td>
			<td>3333566001</td>
			<td></td>
		</tr>
		<tr>
			<td>TdT buffer</td>
			<td>Roche/Sigma</td>
			<td></td>
			<td>Comes with TdT enzyme</td>
		</tr>
		<tr>
			<td>Cobalt chloride</td>
			<td>Roche/Sigma</td>
			<td></td>
			<td>Toxic: wear appropriate protection. Comes with TdT enzyme</td>
		</tr>
		<tr>
			<td>RNase A (10 mg/mL)</td>
			<td>Thermo-Scientific</td>
			<td>EN0531</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Cytology Tools etc.</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Dumont</td>
			<td></td>
			<td>#5 INOX, Biologie</td>
		</tr>
		<tr>
			<td>9&#8221; Disposable glass Pasteur pipettes</td>
			<td>Fisher</td>
			<td>13-678-20C</td>
			<td>Autoclave to sterilize</td>
		</tr>
		<tr>
			<td>Shallow glass dissecting dish</td>
			<td></td>
			<td></td>
			<td>Custom made</td>
		</tr>
		<tr>
			<td>Deep well dish (3 wells)</td>
			<td>Pyrex</td>
			<td>7223-34</td>
			<td></td>
		</tr>
		<tr>
			<td>Fisherfinest Premium microscope slides</td>
			<td>Fisher Scientific</td>
			<td>22-038-104</td>
			<td>Used to cover deep well dishes</td>
		</tr>
		<tr>
			<td>Frosted glass slides, 25 x 75 mm</td>
			<td>VWR Scientific</td>
			<td>48312-002</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass slides, 3 x 1 in, 1 mm thick</td>
			<td>Thermo-Scientific</td>
			<td>3051</td>
			<td></td>
		</tr>
		<tr>
			<td>Coverslips, 10 x 10 mm, No. 1.5</td>
			<td>Thermo-Scientific</td>
			<td>3405</td>
			<td></td>
		</tr>
		<tr>
			<td>Tungsten needle</td>
			<td></td>
			<td></td>
			<td>homemade</td>
		</tr>
		<tr>
			<td>Prolong GOLD mounting media</td>
			<td>Molecular Probes</td>
			<td>P36930</td>
			<td></td>
		</tr>
		<tr>
			<td>Compressed-air in can</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PCR machine</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nanodrop 2000, spectrophotometer</td>
			<td>Thermo-Scientific</td>
			<td></td>
			<td>microvolume spectrophotometer</td>
		</tr>
		<tr>
			<td>Vortexer</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Table top microfuge at room temperature</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Table top microfuge at 4 &#176;C</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Heat block</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hybridization oven or incubator with rotator</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nutator</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>A1RSi laser scanning confoal</td>
			<td>Nikon</td>
			<td></td>
			<td>40X oil Plan Fluor DIC (NA 1.3)</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Consumables etc.</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL conical tubes</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL conical tubes</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 mL microfuge tubes</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>500 &#181;l microfuge tubes</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>200 &#181;l PCR tubes</td>
			<td>Various</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic container with tight fitting lid</td>
			<td>Various</td>
			<td></td>
			<td>To hold Drierite</td>
		</tr>
		<tr>
			<td>Kimwipes</td>
			<td>Various</td>
			<td></td>
			<td>disposable wipes</td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>Various</td>
			<td></td>
			<td>paraffin film</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Other</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>HPLC purified 5&#39;-labeled oligonucleotides</td>
			<td>Integrated DNA Technologies</td>
			<td></td>
			<td>Cy3-labeled probes that recognize the 359 bp satellite repeat of the X chromosome</td>
		</tr>
		<tr>
			<td>Volocity 3D Image Analysis Software</td>
			<td>PerkinElmer</td>
			<td></td>
			<td>Version 6.3</td>
		</tr>
	</tbody>
</table>

using fluorescence in situ hybridization (fish) to monitor the state of arm cohesion in prometaphase and metaphase i drosophila oocytes

In humans, chromosome segregation errors in oocytes are responsible for the majority of miscarriages and birth defects. Moreover, as women age, their risk of conceiving an aneuploid fetus increases dramatically and this phenomenon is known as the maternal age effect. One requirement for accurate chromosome segregation during the meiotic divisions is maintenance of sister chromatid cohesion during the extended prophase period that oocytes experience. Cytological evidence in both humans and model organisms suggests that meiotic cohesion deteriorates during the aging process. In addition, segregation errors in human oocytes are most prevalent during meiosis I, consistent with premature loss of arm cohesion. The use of model organisms is critical for unraveling the mechanisms that underlie age-dependent loss of cohesion. Drosophila melanogaster offers several advantages for studying the regulation of meiotic cohesion in oocytes. However, until recently, only genetic tests were available to assay for loss of arm cohesion in oocytes of different genotypes or under different experimental conditions. Here, a detailed protocol is provided for using fluorescence in situ hybridization (FISH) to directly visualize defects in arm cohesion in prometaphase I and metaphase I arrested Drosophila oocytes. By generating a FISH probe that hybridizes to the distal arm of the X chromosome and collecting confocal Z stacks, a researcher can visualize the number of individual FISH signals in three dimensions and determine whether sister chromatid arms are separated. The procedure outlined makes it possible to quantify arm cohesion defects in hundreds of Drosophila oocytes. As such, this method provides an important tool for investigating the mechanisms that contribute to cohesion maintenance as well as the factors that lead to its demise during the aging process.

Figure 5 presents images obtained with an arm probe that hybridizes to cytological region 6E-7B on the X chromosome. This probe results in a signal that co-localizes with that of DAPI, is easily distinguishable from the background, and has been used successfully to quantify arm cohesion defects in different genotypes19. Quantification of cohesion defects was restricted to prometaphase I and metaphase I stages; oocytes prior to...

Watch this Scientific Journal Video about Using Fluorescence In Situ Hybridization FISH to Monitor the State of Arm Cohesion in Prometaphase and Metaphase I Drosophila Oocytes at JoVE.com

Using Fluorescence In Situ Hybridization FISH to Monitor the State of Arm Cohesion in Prometaphase and Metaphase I Drosophila Oocytes

This manuscript presents a detailed method for generating X-chromosome arm probes and performing fluorescence in situ hybridization (FISH) to examine the state of sister chromatid cohesion in prometaphase and metaphase I arrested Drosophila oocytes. This protocol is suitable for determining whether meiotic arm cohesion is intact or disrupted in different genotypes.

Using Fluorescence In Situ Hybridization (FISH) to Monitor the State of Arm Cohesion in Prometaphase and Metaphase I Drosophila Oocytes

In humans, chromosome segregation errors in oocytes are responsible for the majority of miscarriages and birth defects. Moreover, as women age, their risk ...

The overall goal of this procedure is to generate FISH probes and visualize the state of meiotic arm cohesion in drosophila oocytes during prometaphase one and metaphase one. The main advantage of this technique is that it allows one to assay the state of arm cohesion in prometaphase and metaphase one arrested drosophila oocytes. This method can help answer key questions in the field of drosophila meiosis such as what conditions lead to premature loss of arm cohesion?This technique has the potential to expand our understanding of the maternal age effect in humans which occurs, at least in part, because meiotic cohesion deteriorates as oocytes age. Begin this protocol with the generation of the arm probe for FISH, as well as the dissection and fixation of oocytes as detailed in the text protocol. To separate the late-stage oocytes, first add one milliliter of PBSBTX to a shallow dissecting dish.Then, use a P-200 with a BSA-coated tip to transfer fixed ovaries into the shallow dish. Pipette the ovaries up and down with the BSA-coated pipette tip to dislodge the mature oocytes from the less mature oocytes. When late-stage oocytes are sufficiently separated, transfer all the tissue to a 500-milliliter microfuge tube.Remove excess liquid with a pulled Pasteur pipette leaving about 150 to 200 microliters in the tube. To prepare for oocyte rolling, pre-wet a deep-well dish with 200 microliters of PBSBTX. Cover the dish and set it aside.Obtain three frosted glass slides, and set slide three aside. Next, gently rub the frosted glass regions of slides one and two together. Rinse them in deionized water to remove any glass shards and dry with a disposable wipe.Coat the frosted regions of slides one and two with PBSBTX by adding 50 microliters of PBSBTX to one slide and rubbing this region with the other slide. Remove the liquid a disposable wipe, and place the slides under a dissecting microscope. Keep the frosted regions of slides one and two in contact, with slide three supporting slide two.To roll the oocytes, first pre-wet a P-200 pipette tip in PBSBTX and disperse the oocytes in the microfuge tube by pipetting up and down. Transfer 50 microliters of liquid containing the oocytes to the center of the frosted glass part of slide one. Lift slide two to do this.Slowly lower slide two until the surface tension of the liquid creates a seal between the two frosted glass regions. There should be enough liquid to cover the frosted area, but none should be seeping out. Then, hold the bottom slide one in place with one hand, and use the other hand to move the top slide two back and forth in a horizontal direction keeping slide two level and supported on slide three.Perform under a microscope for easy visualization of oocyte movements and progress. After a few movements in the horizontal direction, slightly change the angle of movement. In multiple increments, gradually increase this angle to 90 degrees until movement of the top slide two is perpendicular to the starting direction.Note that empty chorions will be visible in the liquid and oocytes lacking chorions will appear longer and thinner. When rolling the oocytes, ensure that the direction of rolling is always in a straight line and never a circular motion. Repeat the rolling about seven to 10 times until the solution becomes slightly cloudy.Stop rolling when the majority of oocytes appear to have lost their vitelline membranes. Gently lift the top slide two dragging one of its corners to the center of the frosted region of the bottom slide one so that the rolled oocytes accumulate in the center of the frosted region. Rinse the oocytes from both slides with PBSBTX into the deep-well dish containing PBSBTX.Clean slides one and two with ultrapure water. Dry with a disposable wipe and reset. Repeat these steps until all the oocytes of the same genotype have been rolled.This usually requires three to four rounds of rolling per genotype. To remove debris after rolling, add one milliliter of PBSBTX to a 15-milliliter conical tube. Swirl the liquid to coat the sides of the tube.Using a PBSBTX-coated P-1, 000 pipette tip, transfer the rolled oocytes from the deep-well dish to the conical tube containing one milliliter of PBSBTX. Add an additional two milliliters of PBSBTX to the conical tube containing the oocytes. Hold the conical tube against a dark background to see the opaque oocytes as they sink.After letting the oocytes settle to the bottom, use a P-1, 000 to remove the top two milliliters of solution containing debris and discard. After repeating the step for a total of three rounds of debris removal, use a PBSBTX-coated P-1, 000 pipette tip to transfer the oocytes back to the original 500-microliter microfuge tube. 20 to 25 females should yield approximately 50 microliters of rolled mature oocytes.Repeat this process for the remaining genotypes using fresh frosted slides, a clean deep-well dish and a new conical tube for each genotype. Rinse the oocytes with 500 microliters of PBS containing 1%Triton X-100. Remove the liquid and add 500 microliters of extraction buffer.Incubate the sample on the nutator at room temperature for two hours. After performing pre-hybridization washes as described in the text protocol, perform the denaturation and hybridization. First, use a BSA-coated P-200 pipette tip to transfer the oocytes to a 200-microliter PCR tube.Keep samples at 37 degrees Celsius and let the oocytes settle to the bottom. It is important to be patient when changing solutions so that the oocytes are not lost in the process. Once the oocytes have settled, use a pulled Pasteur pipette to remove as much liquid as possible.Then, add 40 microliters of probe-containing hybridization solution to the oocytes. Place the PCR tube containing the oocytes in the PCR machine and incubate as listed in the text protocol. After the probe is added to the oocytes, keep them in the dark as much as possible.For post-hybridization washes, preheat the 2X SSCT plus 50%formamide to 37 degrees Celsius and keep it in the hybridization incubator. With a BSA-coated P-200 pipette tip, add 100 microliters of 37-degrees Celsius 2X SSCT plus 50%formamide to the PCR tube with the oocytes, and transfer the oocytes to a new 500-microliter microfuge tube. After adding an additional 400 microliters of 37-degrees Celsius 2X SSCT plus 50%formamide to the same tube, let the oocytes settle at 37 degrees Celsius in the incubator.Settling often takes longer at this step. It is not unusual to take 15 minutes or more. A lack of patience will result in a significant loss of oocytes.After allowing the oocytes to settle, remove liquid with a pulled Pasteur pipette. Add 500 microliters of 37-degrees Celsius 2X SSCT plus 50%formamide at 37 degrees Celsius and wash the oocytes with rotation. Following each wash slash rotation step, keep the oocytes at 37 degrees Celsius while they settle.After additional washes at room temperature, stain with DAPI by washing oocytes for 20 minutes in 500 microliters of one-microgram-per-milliliter DAPI solution in 2X SSCT on the nutator. After rinsing the oocytes three times in 500 microliters of 2X SSCT, wash the oocytes two times for 10 minutes each in 500 microliters of 2X SSCT on the nutator. Samples can be stored for up to four hours at room temperature in the dark until they are ready to mount on the cover slips.With a BSA-coated P-200 pipette tip, pipette up and down to disperse oocytes throughout the solution. Then, transfer 40 microliters of the oocyte solution to a poly-L-lysine-coated cover slip. Remove some of the liquid from the cover slip using a pulled Pasteur pipette until the oocytes stick to the cover slip but are still surrounded by liquid.With forceps, hold down the cover slip on one side, and use a Tungsten needle to gently dissociate clumps of oocytes moving them to achieve a single layer of non-overlapping oocytes. Remove the remainder of the liquid around the oocytes with a pulled Pasteur pipette. Then, slowly lower the slide towards the cover slip with the mounting media facing the sample until the media touches the sample.After letting the slides dry for three to five days in the dark, acquire laser scanning confocal images using a high-numerical aperture 40 times oil objective with six times digital zoom as detailed in the text protocol. A software package that allows one to view images and score for cohesion defects in three dimensions is imperative. This allows one to scroll through the Z series to view the FISH spots and to accurately count the number of individual arm signals.Maximum intensity projections of confocal Z series are shown for oocytes with intact and disrupted arm cohesion. In these figures, the arm probe signal is yellow and the pericentric probe signal is red. Two arm probe spots indicate that sister chromatids are together and arm cohesion is intact.Three arm probe spots indicate that one pair of sister chromatids have prematurely lost arm cohesion while the other pair of sisters has not. If two arm probe spots are connected by a thread, the sister chromatids are not scored as separated. Therefore, a meiotic figure like this is considered to have only three arm probe spots with one pair of sisters exhibiting premature loss of arm cohesion.Premature loss of arm cohesion for both sets of sister chromatids results in four arm probe spots. In all four examples shown, centromeric cohesion is intact. Once mastered, rolling the oocytes for one genotype can be done in approximately 25 minutes if it is performed properly.After watching this video, you should have a good understanding of how to roll oocytes, perform FISH using arm probes and score images to determine the state of meiotic arm cohesion in drosophila oocytes. While performing the hybridization and washes, it is important to remember to be patient. Not waiting long enough for oocytes to settle after each wash step will reduce the yield of oocytes for imaging at the end.It may be possible to optimize this protocol to combine FISH with amino staining in order to answer additional questions about protein localization or the structure of the meiotic spindle while also monitoring the state of arm cohesion. The development of this technique will pave the way for researchers in the field of drosophila meiosis to explore the mechanisms that ensure and disrupt meiotic arm cohesion and impact chromosome segregation.

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Understanding Early Organogenesis Using a Simplified In Situ Hybridization Protocol in Xenopus

Organogenesis is the study of how organs are specified and then acquire their specific shape and functions during development. The Xenopuslaevis embryo is very useful for studying organogenesis because their large size makes them very suitable for identifying organs at the earliest steps in organogenesis. At this time, the primary method used for identifying a specific organ or primordium is whole mount in situ hybridization with labeled antisense RNA probes specific to a gene that is expressed in the organ of interest. In addition, it is relatively easy to manipulate genes or signaling pathways in Xenopus and in situ hybridization allows one to then assay for changes in the presence or morphology of a target organ. Whole mount in situ hybridization is a multi-day protocol with many steps involved. Here we provide a simplified protocol with reduced numbers of steps and reagents used that works well for routine assays. In situ hybridization robots have greatly facilitated the process and we detail how and when we utilize that technology in the process. Once an in situ hybridization is complete, capturing the best image of the result can be frustrating. We provide advice on how to optimize imaging of in situ hybridization results. Although the protocol describes assessing organogenesis in Xenopus laevis, the same basic protocol can almost certainly be adapted to Xenopus tropicalis and other model systems.

Understanding Early Organogenesis Using a Simplified In Situ Hybridization Protocol in Xenopus

The Xenopus laevis embryo continues to be exceptionally useful in the study of early development due to its large size and ease of manipulation. A simplified protocol for whole mount in situ hybridization protocol is provided that can be used in the identification of specific organs in this model system.

Organogenesis is the study of how organs are specified and then acquire their specific shape and functions during development.  The Xenopuslaevis embryo ...

Multi-target Chromogenic Whole-mount In Situ Hybridization for Comparing Gene Expression Domains in Drosophila Embryos

To analyze gene regulatory networks active during embryonic development and organogenesis it is essential to precisely define how the different genes are expressed in spatial relation to each other in situ. Multi-target chromogenic whole-mount in situ hybridization (MC-WISH) greatly facilitates the instant comparison of gene expression patterns, as it allows distinctive visualization of different mRNA species in contrasting colors in the same sample specimen. This provides the possibility to relate gene expression domains topographically to each other with high accuracy and to define unique and overlapping expression sites. In the presented protocol, we describe a MC-WISH procedure for comparing mRNA expression patterns of different genes in Drosophila embryos. Up to three RNA probes, each specific for another gene and labeled by a different hapten, are simultaneously hybridized to the embryo samples and subsequently detected by alkaline phosphatase-based colorimetric immunohistochemistry. The described procedure is detailed here for Drosophila, but works equally well with zebrafish embryos.

Multi-target Chromogenic Whole-mount In Situ Hybridization for Comparing Gene Expression Domains in Drosophila Embryos

We describe a multi-target chromogenic whole-mount in situ hybridization (MC-WISH) procedure in intact Drosophila embryos allowing simultaneous and specific detection of three different mRNA distribution patterns by contrasting color precipitates.

To analyze gene regulatory networks active during embryonic development and organogenesis it is essential to precisely define how the different genes are ...

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 ...

Cell Aggregation Assays to Evaluate the Binding of the Drosophila Notch with Trans-Ligands and its Inhibition by Cis-Ligands

Notch signaling is an evolutionarily conserved cell-cell communication system used broadly in animal development and adult maintenance. Interaction of the Notch receptor with ligands from neighboring cells induces activation of the signaling pathway (trans-activation), while interaction with ligands from the same cell inhibits signaling (cis-inhibition). Proper balance between trans-activation and cis-inhibition helps establish optimal levels of Notch signaling in some contexts during animal development. Because of the overlapping expression domains of Notch and its ligands in many cell types and the existence of feedback mechanisms, studying the effects of a given post-translational modification on trans- versus cis-interactions of Notch and its ligands in vivo is difficult. Here, we describe a protocol for using Drosophila S2 cells in cell-aggregation assays to assess the effects of knocking down a Notch pathway modifier on the binding of Notch to each ligand in trans and in cis. S2 cells stably or transiently transfected with a Notch-expressing vector are mixed with cells expressing each Notch ligand (S2-Delta or S2-Serrate). Trans-binding between the receptor and ligands results in the formation of heterotypic cell aggregates and is measured in terms of the number of aggregates per mL composed of &#62;6 cells. To examine the inhibitory effect of cis-ligands, S2 cells co-expressing Notch and each ligand are mixed with S2-Delta or S2-Serrate cells and the number of aggregates is quantified as described above. The relative decrease in the number of aggregates due to the presence of cis-ligands provides a measure of cis-ligand-mediated inhibition of trans-binding. These straightforward assays can provide semi-quantitative data on the effects of genetic or pharmacological manipulations on the binding of Notch to its ligands, and can help deciphering the molecular mechanisms underlying the in vivo effects of such manipulations on Notch signaling.

Cell Aggregation Assays to Evaluate the Binding of the Drosophila Notch with Trans-Ligands and its Inhibition by Cis-Ligands

Complexity of in vivo systems makes it difficult to distinguish between the activation and inhibition of Notch receptor by trans- and cis-ligands, respectively. Here, we present a protocol based on in vitro cell-aggregation assays for qualitative and semi-quantitative evaluation of the binding of Drosophila Notch to trans-ligands vs cis-ligands.

Notch signaling is an evolutionarily conserved cell-cell communication system used broadly in animal development and adult maintenance. Interaction of the ...

Wholemount In Situ Hybridization for Astyanax Embryos

In recent years, a draft genome for the blind Mexican cavefish (Astyanax mexicanus) has been released, revealing the sequence identities for thousands of genes. Prior research into this emerging model system capitalized on comprehensive genome-wide investigations that have identified numerous quantitative trait loci (QTL) associated with various cave-associated phenotypes. However, the ability to connect genes of interest to the heritable basis for phenotypic change remains a significant challenge. One technique that can facilitate deeper understanding of the role of development in troglomorphic evolution is whole-mount in situ hybridization. This technique can be implemented to directly compare gene expression between cave- and surface-dwelling forms, nominate candidate genes underlying established QTL, identify genes of interest from next-generation sequencing studies, or develop other discovery-based approaches. In this report, we present a simple protocol, supported by a flexible checklist, that can be widely adapted for use well beyond the presented study system. It is hoped that this protocol can serve as a broad resource for the Astyanax community and beyond.

Wholemount In Situ Hybridization for Astyanax Embryos

This protocol enables visualization of gene expression in embryonic Astyanax cavefish. This approach has been developed with the goal of maximizing gene expression signal, while minimizing non-specific background staining.

In recent years, a draft genome for the blind Mexican cavefish (Astyanax mexicanus) has been released, revealing the sequence identities for thousands of ...

Genotyping and Quantification of In Situ Hybridization Staining in Zebrafish

In situ hybridization (ISH) is an important technique that enables researchers to study mRNA distribution in situ and has been a critical technique in developmental biology for decades. Traditionally, most gene expression studies relied on visual evaluation of the ISH signal, a method that is prone to bias, particularly in cases where sample identities are known a priori. We have previously reported on a method to circumvent this bias and provide a more accurate quantification of ISH signals. Here, we present a simple guide to apply this method to quantify the expression levels of genes of interest in ISH-stained embryos and correlate that with their corresponding genotypes. The method is particularly useful to quantify spatially restricted gene expression signals in samples of mixed genotypes and it provides an unbiased and accurate alternative to the traditional visual scoring methods.

Gene editing technologies have enabled researchers to generate zebrafish mutants to investigate gene function with relative ease. Here, we provide a guide to perform parallel embryo genotyping and quantification of in situ hybridization signals in zebrafish. This unbiased approach provides greater accuracy in phenotypical analyses based on in situ hybridization.

In situ hybridization (ISH) is an important technique that enables researchers to study mRNA distribution in situ and has been a critical technique in ...

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

Vascular development is determined by the sequential expression of specific genes, which can be studied by performing in situ hybridization assays in zebrafish during different developmental stages. To investigate the role of endoglin(eng) in vessel formation during the development of hereditary hemorrhagic telangiectasia&#160;(HHT), morpholino-mediated targeted knockdown of eng in zebrafish are used to study its temporal expression and associated functions. Here, whole-mount in situ RNA hybridization (WISH) is employed for the analysis of eng and its downstream genes in zebrafish embryos. Also, tube formation assays are performed in HHT patient-derived induced pluripotent stem cell-differentiated&#160;endothelial cells (iPSC-ECs; with eng mutations). A specific signal amplifying system using the whole amount In Situ Hybridization &#8211; WISH provides higher resolution and lower background results compared to traditional methods. To obtain a better signal, the post-fixation time is adjusted to 30 min after probe hybridization. Because fluorescence staining is not sensitive in zebrafish embryos, it is replaced with diaminobezidine (DAB) staining here. In this protocol, HHT&#160;patient-derived iPSC lines containing an eng mutation are differentiated into endothelial cells. After coating a plate with basement membrane matrix for 30 min at 37 &#176;C, iPSC-ECs are seeded as a monolayer into wells and kept at 37 &#176;C for 3 h. Then, the tube length and number of branches are calculated using microscopic images. Thus, with this improved WISH protocol, it is shown that reduced eng expression affects endothelial progenitor formation in zebrafish embryos. This is further confirmed by tube formation assays using iPSC-ECs derived from a patient with HHT. These assays confirm the role for eng in early vascular development.

Presented here is a protocol for whole-mount in situ RNA hybridization analysis in zebrafish and tube formation assay in patient-derived induced pluripotent stem cell-derived endothelial cells to study the role of endoglin in vascular formation.

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

A Protocol for Immunohistochemistry and RNA In-situ Distribution within Early Drosophila Embryo

Calcium induced calcium release signaling (CICR) plays a critical role in many biological processes. Every cellular activity from cell proliferation and apoptosis, development and ageing, to neuronal synaptic plasticity and regeneration have been associated with Ryanodine receptors (RyRs). Despite the importance of calcium signaling, the exact mechanism of its function in early development is unclear. As an organism with a short gestational period, the embryos of Drosophila melanogaster are prime study subjects for investigating the distribution and localization of CICR associated proteins and their regulators during development. However, because of their lipid-rich embryos and chitin-rich chorion, their utility is limited by the difficulty of mounting embryos on glass surfaces. In this work, we introduce a practical protocol that significantly enhances the attachment of Drosophila embryo onto slides and detail methods for successful histochemistry, immunohistochemistry, and in-situ hybridization. The chrome alum gelatin slide-coating method and embryo pre-embedding method dramatically increases the yield in studying Drosophila embryo protein and RNA expression. To demonstrate this approach, we studied DmFKBP12/Calstabin, a well-known regulator of RyR during early embryonic development of Drosophila melanogaster. We identified DmFKBP12 in as early as the syncytial blastoderm stage and report the dynamic expression pattern of DmFKBP12 during development: initially as an evenly distributed protein in the syncytial blastoderm, then preliminarily localizing to the basement layer of the cortex during cellular blastoderm, before distributing in the primitive neuronal and digestion architecture during the three-gem layer phase in early gastrulation. This distribution may explain the critical role RyR plays in the vital organ systems that originate in from these layers: the suboesophageal and supraesophageal ganglion, ventral nervous system, and musculoskeletal system.

A Protocol for Immunohistochemistry and RNA In-situ Distribution within Early Drosophila Embryo

Here, we describe a protocol for detection and localization of Drosophila embryo protein and RNA from collection to pre-embedding and embedding, immunostaining, and mRNA in situ hybridization.

Calcium induced calcium release signaling (CICR) plays a critical role in many biological processes. Every cellular activity from cell proliferation and ...

In Situ Hybridization in Zebrafish Larvae and Juveniles during Mesonephros Development

The zebrafish forms two kidney structures in its lifetime. The pronephros (embryonic kidney) forms during embryonic development and begins to function at 2 days post fertilization. Consisting of only two nephrons, the pronephros serves as the sole kidney during larval life until more renal function is required due to the increasing body mass. To cope with this higher demand, the mesonephros (adult kidney) begins to form during metamorphosis. The new primary nephrons fuse to the pronephros and form connected lumens. Then, secondary nephrons fuse to primary ones (and so on) to create a branching network in the mesonephros. The vast majority of research is focused on the pronephros due to the ease of using embryos. Thus, there is a need to develop techniques to study older and larger larvae and juvenile fish to better understand mesonephros development. Here, an in situ hybridization protocol for gene expression analysis is optimized for probe penetration, washing of probes and antibodies, and bleaching of pigments to better visualize the mesonephros. The Tg(lhx1a-EGFP) transgenic line is used to label progenitor cells and the distal tubules of nascent nephrons. This protocol fills a gap in mesonephros research. It is a crucial model for understanding how new kidney tissues form and integrate with existing nephrons and provide insights into regenerative therapies.

In Situ Hybridization in Zebrafish Larvae and Juveniles during Mesonephros Development

The zebrafish is an important model for understanding kidney development. Here, an in situ hybridization protocol is optimized to detect gene expression in zebrafish larvae and juveniles during mesonephros development.

The zebrafish forms two kidney structures in its lifetime. The pronephros (embryonic kidney) forms during embryonic development and begins to function at ...

Isolation of Rat Adipose Tissue Mesenchymal Stem Cells for Differentiation into Insulin-producing Cells

Mesenchymal stem cells (MSCs)-especially those isolated from adipose tissue (Ad-MSCs)-have gained special attention as a renewable, abundant source of stem cells that does not pose any ethical concerns. However, current methods to isolate Ad-MSCs are not standardized and employ complicated protocols that require special equipment. We isolated Ad-MSCs from the epididymal fat of Sprague-Dawley rats using a simple, reproducible method. The isolated Ad-MSCs usually appear within 3 days post isolation, as adherent cells display fibroblastic morphology. Those cells reach 80% confluency within 1 week of isolation. Afterward, at passage 3-5 (P3-5), a full characterization was carried out for the isolated Ad-MSCs by immunophenotyping for characteristic MSC cluster of differentiation (CD) surface markers such as CD90, CD73, and CD105, as well as inducing differentiation of these cells down the osteogenic, adipogenic, and chondrogenic lineages. This, in turn, implies the multipotency of the isolated cells. Furthermore, we induced the differentiation of the isolated Ad-MSCs toward the insulin-producing cells (IPCs) lineage via a simple, relatively short protocol by incorporating high glucose Dulbecco&#39;s modified Eagle medium (HG-DMEM), &#946;-mercaptoethanol, nicotinamide, and exendin-4. IPCs differentiation was genetically assessed, firstly, via measuring the expression levels of specific &#946;-cell markers such as MafA, NKX6.1, Pdx-1, and Ins1, as well as dithizone staining for the generated IPCs. Secondly, the assessment was also carried out functionally by a glucose-stimulated insulin secretion (GSIS) assay. In conclusion, Ad-MSCs can be easily isolated, exhibiting all MSC characterization criteria, and they can indeed provide an abundant, renewable source of IPCs in the lab for diabetes research.

Adipose tissue-derived mesenchymal stem cells (Ad-MSCs) can be a potential source of MSCs that differentiate into insulin-producing cells (IPCs). In this protocol, we provide detailed steps for the isolation and characterization of rat epididymal Ad-MSCs, followed by a simple, short protocol for the generation of IPCs from the same rat Ad-MSCs.

Mesenchymal stem cells (MSCs)-especially those isolated from adipose tissue (Ad-MSCs)-have gained special attention as a renewable, abundant source of ...