Name: Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes (Video) | JoVE Journal
Uploaded: 2017-05-11T14:00:00.000+00:00
Duration: 12 min 11 s
Description: Learn ultrasound-guided ovum pick-up (OPU) to characterize horse oocytes through chromosome segregation, spindle morphology, and histone acetylation analysis. This method advances fertility research in monovulatory species.

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5 minutes

The authors would like to thank Fabrice Vincent for the support with laser scanning confocal microscopy (LSCM), and Philippe Barri&#232;re and Thierry Blard for performing daily ultrasound ovarian scanning and hCG injection. This work was supported in part by the &#34;Regione Sardegna and Regione Lombardia&#34; project &#34;Ex Ovo Omnia&#34; (Grant no. 26096200 to A. M. L.); the &#34;L&#39;Oreal Italia per le Donne e la Scienza 2012&#34; fellowship (Contract 2012 to F. F.), FP7-PEOPLE-2011- CIG, Research Executive Agency (REA) &#34;Pro-Ovum&#34; (Grant no. 303640 to V. L.); and by the Postdoctoral School of Agriculture and Veterinary Medicine, co-financed by the European Social Fund, Sectorial Operational Program for Human Resource Development 2007-2013 (Contract no. POSDRU/89/1.5/S/62371 to I. M.). The in vivo oocyte collection was financed by the Institut Fran&#231;ais du Cheval et de l&#39;Equitation.

All the procedures were approved by the Animal Care and Use Committee CEEA Val de Loire Number 19 and were performed in accordance with the Guiding Principles for the Care and Use of Laboratory Animals.
1. Oocyte Collection and In Vitro Maturation
<ol>
	<li>Ovum pick-up
	<ol>
		<li>Daily assess by ultrasound the diameter of ovarian follicles in a cohort of adult mares. At the emergence of a follicle &#8805;33 mm (dominant follicle), inject the mare with 1,500 IU of human chorionic gonadotrophin (hCG) in the upper part of the jugular vein (i.v.).
		<ol>
			<li>Before performing the injection, swab the area with alcohol, locate the jugular furrow, and place the thumb 2-3 cm under the site of injection to induce the vein to rise. Insert the needle almost parallel to the neck and aspirate to make sure that the needle is in the vein (the blood will enter the syringe). At this point, inject; hCG will induce the maturation of the oocyte in the dominant follicle.</li>
		</ol>
		</li>
		<li>35 h after the hCG injection, sedate the mare with detomidine (15 &#181;g/kg, i.v.), butorphanol tartrate (10 &#181;g/kg, i.v.) and butylscopolamine bromure (0.2-0.3 mg/kg, 15 mL/mare, i.v.).</li>
		<li>Connect the needle to the ultrasound probe. Insert the ultrasound probe vaginally and hold the ovary transrectally to face the ultrasound probe. Instruct one operator to maneuver the needle and the other to hold the ovary in place, with the follicle facing the ultrasound probe. Start from the ovary with the dominant follicle.</li>
		<li>Puncture the vaginal wall and the wall of the dominant follicle with the needle (ultrasound probes for OPU are equipped with a channel for the needle connected to a suction system); theneedle will be visible in the echographic image.</li>
		<li>Aspirate the follicular fluid in a 50-mL conical tube connected to the suction system. Pour the content of the conical tube into a large petri dish and search for the cumulus-oocyte complex (COC) using a stereomicroscope.</li>
		<li>Since the COC is not always retrieved with the follicular fluid, flush the follicle with Dulbecco&#39;s modified phosphate-buffered saline (DPBS) containing 5 IU/mL heparinat 37 &#176;C. Examine DPBS for COC presence, as previously described for the follicular fluid in step 1.1.5. Flush several times until the COC is retrieved.</li>
		<li>Once the COC from the dominant follicle is retrieved, puncture and flush the follicles &#8805;5 and &#8804;25 mm, as described for the dominant follicle in steps 1.1.3-1.1.4; follicles &#8805;5 and &#8804;25 do not express luteinizing hormone/choriogonadotropin receptor (LHCGR), and therefore, their oocytes will not mature in response to hCG and will be collected at GV stage (immature). Only keep COCs with several complete layers of cumulus cells and brown, finely-granulated ooplasm. Discard the others.</li>
		<li>At the end of the OPU, inject the mare with benzyl-penicillin 15,000 IU/animal to prevent infection.</li>
		<li>House the mare in a quiet, clean stable for at least 2 h. Check signs of awareness by determining the position of the ears, reaction to stimuli (e.g., noise), and gait before returning the mare to the company of other animals.</li>
	</ol>
	</li>
	<li>In vitro maturation
	<ol>
		<li>Warm HEPES-buffered TCM199 (20 mM Hepes) supplemented with 1,790 IU/L heparin, 0.4% bovine serum albumin (BSA), penicillin, and streptomycin to 37 &#176;C. Prepare this medium in advance. Filter-sterilize and keep it at 4 &#176;C for up to 6 months.</li>
		<li>Prepare the IVM medium by supplementing NaHCO3-buffered TCM199 (25 mM NaHCO3) with 50 ng/mL epidermal growth factor (EGF) and 20% calf serum7. Use NaHCO3-buffered TCM199 within 3 weeks of opening a new bottle. Prepare the EGF in advance as 100x stocks, freeze it at -20 &#176;C, and use it within 6 months. Dispense 500 &#181;L in the wells of a 4-well dish and incubate in humidified air with 5% CO2 at 38.5 &#176;C for at least 2 h.</li>
		<li>After the retrieval of the COCs from the &#8805;5 and &#8804;25 mm follicles, put them in a petri dish (3.5-cm diameter) filled with 2 mL of HEPES-TCM199. Move the COCs to different areas of the dish in order to wash away the cellular debris.</li>
		<li>Transfer the COCs to the IVM medium and incubate for 28 h in humidified air with 5% CO2 at 38.5 &#176;C.</li>
	</ol>
	</li>
</ol>
2. Immunofluorescence and Image Analysis
<ol>
	<li>Chromosome count
	<ol>
		<li>After collection from the dominant follicle or at the end of IVM, incubate the COCs with 100 &#181;M monastrol for 1 h in humidified air with 5% CO2 at 38.5 &#176;C. Prepare monastrol in advance as 100x stocks and store it at -20 &#176;C for up to 1 year.</li>
		<li>Remove the cumulus cells by treating them with 0.5% hyaluronidase or by gently pipetting; remove the zona pellucida by treating it in 0.2% pronase. Prepare hyaluronidase and pronase in advance as 10x stocks and store them at -20 &#176;C for up to 1 year.</li>
		<li>Fix the oocytes in 4% paraformaldehyde in DPBS for 15 min at 38.5 &#176;C followed by a further 45 min at 4 &#176;C. 
		CAUTION! Wear personal protective equipment when handling paraformaldehyde, and dispose of contaminated materials in accordance with hazardous waste disposal guidelines.</li>
		<li>Wash the oocytes by sequentially transferring in 3 wells filled with 500 &#181;L of DPBS supplemented with 0.1% polyvinyl alcohol (PVA). Permeabilize in 0.3% Triton X-100 for 10 min at room temperature (RT).</li>
		<li>Block non-specific bindingby incubation in DPBS supplemented with 1% bovine serum albumin (DPBS-1%BSA) and 10% normal donkey serum for at least 30 min at RT. Samples can be kept in blocking solution at 4 &#176;C for 3-4 days.</li>
		<li>For primary staining, incubate the oocytes in rabbit anti-Aurora B phospho-Thr232 in DPBS supplemented with 1% BSA (dilution 1:50) at 4 &#176;C overnight.</li>
		<li>Wash the oocytes as described in step 2.1.4. Incubate the oocytes in a solution of tetra-methylrhodamine isothiocyanate (TRITC)-conjugated donkey anti-rabbit IgG (1:100 in DPBS-1% BSA) for 1 h at RT in the dark.</li>
		<li>Wash the oocytes as described in step 2.1.4, and then place 3-4 oocytes in a drop of non-hardening, anti-fade mounting medium supplemented with 20 &#181;M YOPRO1 on a glass slide. Repeat the procedure until all the oocytes are mounted (3-4 oocytes per slide).</li>
		<li>Allow the oocytes to settle for about 10 min in the mounting medium, and then cover them with a coverslip. To avoid crushing the oocytes, apply two strips of double-sided tape before laying the coverslip on the glass slide. 
		NOTE: This precaution will also ensure that all the samples are equally compressed between the glass slide and the coverslip. Glass slides can be frozen at -20 &#176;C and imaged during the following 2-3 days.</li>
		<li>Image the samples on a confocal laser scanning microscope with a 60X objective using the red (centromeres) and green (chromosomes) channels7,13,14,20,21. Scan the samples spanning the whole metaphasic plate on the z-axis, with steps every 0.35 &#181;m. Save the digitalized images of every single plan.</li>
		<li>Count the centromeres in serial confocal sections using the cell count function of the NIH ImageJ software (available at: https://imagej.nih.gov/ij/plugins/cell-counter.html). 
		NOTE: Avoid a repeated count of centromeres that appear on adjacent sections by identifying the centromeres that appear, stay, and disappear in sequential sections with a numeric code.</li>
		<li>Repeat the chromosomal counting in step 2.1.11 with an independent operator. 
		NOTE: Classify the oocytes as euploid (32 chromosomes), hyperploid (&#62;32), or hypoploid (&#60;32).</li>
	</ol>
	</li>
	<li>Spindle morphology and histone acetylation
	<ol>
		<li>After collection from the dominant follicle or at the end of the IVM, remove the cumulus cells by treatment in 0.5% hyaluronidase or by gentle pipetting, as described in step 2.1.2.</li>
		<li>Wash the oocytes in DPBS-PVA, as in step 2.1.4, and fix them in 2.5% paraformaldehyde for 20 min at 38 &#176;C. Extensively wash, as described in step 2.1.4, and permeabilize in 0.1% Triton X-100 for 5 min at RT. 
		NOTE: Wear personal protective equipment when handling paraformaldehyde and dispose of contaminated materials in accordance with hazardous waste disposal guidelines.</li>
		<li>Block non-specific bindingby incubation in DPBS supplemented with 2% bovine serum albumin (DPBS - 2%BSA), 0.05% saponin, and 10% normal donkey serum for 2 h at RT. 
		NOTE: Samples can be kept in blocking solution at 4 &#176;C for 3 - 4 days.</li>
		<li>For primary staining, incubate the oocytes in mouse anti-alpha-tubulin (1:150) and rabbit anti-acH4K16 (1:250) in DPBS-2% BSA with 0.05% saponin at 4 &#176;C overnight.</li>
		<li>Wash the oocytes as in step 2.1.4. Incubate the oocytes in a solution of green fluorescent dye-conjugated donkey anti-mouse IgG (1:500) and TRITC-conjugated donkey anti-rabbit IgG (1:100) in DPBS-2% BSA with 0.05% saponin for 1 h at RT in the dark.</li>
		<li>Wash the oocytes as in step 2.1.4, and then place 3-4 oocytes in a drop of the non-hardening, anti-fade mounting medium supplemented with 1 &#181;g/mL 4&#39;,6-diamidino-2-phenylindole (DAPI) on a glass slide.</li>
		<li>Mount the oocytes on glass slides as described in step 2.1.8.</li>
		<li>Image the samples on a confocal laser scanning microscope with a 60x objective using the red (acH4K16), green (alpha-tubulin), and blue (DNA) channels. 
		NOTE: Keep the laser settings for the red and blue channels constant throughout the acquisition of all the samples. Scan the samples spanning the whole meiotic spindle and metaphasic plate on the z-axis, with steps every 0.35 &#181;m. Save the digitalized images (single plans and projected 3D image).</li>
		<li>Measure the pole-to-pole spindle length and the spindle diameter at the maximum width on the projected image using the measurement function of the NIH ImageJ software (https://imagej.nih.gov/ij/docs/guide/146-30.html). Repeat each 3 times and calculate the mean.</li>
		<li>Quantify the relative fluorescence of acH4K16 using the integrated density function of the NIH ImageJ software (https://imagej.nih.gov/ij/docs/guide/146-30.html). Normalize it for the integrated density of the DAPI staining.</li>
	</ol>
	</li>
</ol>
3. Analysis of mRNA Expression
<ol>
	<li>After the COCs have been retrieved from the 5 to 25 mm follicles, collect the granulosa cell suspension that remained in the Petri dish and wash it twice in cold DPBS by centrifuging at 10,600 x g for 2 min. Snap freeze in liquid nitrogen. Store the samples at -80 &#176;C for up to 6 months; the cells will serve for the standard curve.</li>
	<li>Carefully remove all the cumulus cells, as described in step 2.1.2, from immature (GV), in vitro matured, and in vivo matured oocytes.</li>
	<li>Wash the oocytes, as described in 2.1.4, in DPBS-PVA, collect them singly in 1 &#181;L volumes, and lay 2 &#181;L RNALater on top. Snap-freeze in liquid nitrogen. Store the samples at -80 &#176;C for up to 6 months.</li>
	<li>Add 2 pg of Luciferase RNA to each sample as a spike-in. Pool the oocytes 2 x 2 and extract the total RNA using a silica membrane filter-based kit suitable to recover RNA from small samples.</li>
	<li>Reverse-transcribe the RNA in 10 &#181;L with 0.25 &#181;g random hexamers and mouse Moloney leukaemia virus reverse transcriptase for 1 h at 37 &#176;C. Store the samples at -20 &#176;C for up to 6 months.</li>
	<li>Dilute the cDNA from the granulosa cells in RNAse-free water to 50 ng/&#181;L. Serially dilute this solution 1:10 to obtain 5 ng/&#181;L, 0.5 ng/&#181;L, 0.05 ng/&#181;L, and 0.005 ng/&#181;L solutions.</li>
	<li>Assemble reactions in triplicate in a total volume of 20 &#181;L per reaction using cDNA equivalent to 0.05 oocytes as the substrate, or 5 &#181;L of the serial dilutions of granulosa cell cDNA, 10 &#181;L of SYBR green supermix, and 0.3 &#181;M of each specific primer (Table 1).</li>
	<li>Run the reaction in a thermal cycler using a 3-step protocol: 95 &#176;C for 30 s, 60 &#176;C for 30 s, and 72 &#176;C for 20 s, repeated 40 times. Finally, acquire the melting curve, starting from 60 &#176;C, and increase the temperature by 0.5 &#176;C every 20 s up to 95 &#176;C.</li>
	<li>Assess the starting quantity (SQ) of the specific mRNA in the oocyte samples using the standard curve15 calculated based on the granulosa cell sample. Express the data as the ratio between the SQ of the gene of interest and the SQ of the housekeeping genes.</li>
</ol>

<ol><li>Dellenbach, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transvaginal%2C+sonographically+controlled+ovarian+follicle+puncture+for+egg+retrieval%5BTitle%5D)+AND+%22Lancet%22%5BJournal%5D)">Transvaginal, sonographically controlled ovarian follicle puncture for egg retrieval.</a> Lancet. 1 (8392), 1467(1984).</li>
<li>Humaidan, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ovarian+hyperstimulation+syndrome%3A+review+and+new+classification+criteria+for+reporting+in+clinical+trials%5BTitle%5D)+AND+%22Hum+Reprod%22%5BJournal%5D)">Ovarian hyperstimulation syndrome: review and new classification criteria for reporting in clinical trials.</a> Hum Reprod. , (2016).</li>
<li>Pincus, G., Enzmann, E. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Comparative+Behavior+of+Mammalian+Eggs+in+Vivo+and+in+Vitro+%3A+I.+The+Activation+of+Ovarian+Eggs%5BTitle%5D)+AND+%22J+Exp+Med%22%5BJournal%5D)">The Comparative Behavior of Mammalian Eggs in Vivo and in Vitro : I. The Activation of Ovarian Eggs.</a> J Exp Med. 62 (5), 665-675 (1935).</li>
<li>Emery, B. R., Wilcox, A. L., Aoki, V. W., Peterson, C. M., Carrell, D. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In+vitro+oocyte+maturation+and+subsequent+delayed+fertilization+is+associated+with+increased+embryo+aneuploidy%5BTitle%5D)+AND+%22Fertil+Steril%22%5BJournal%5D)">In vitro oocyte maturation and subsequent delayed fertilization is associated with increased embryo aneuploidy.</a> Fertil Steril. 84 (4), 1027-1029 (2005).</li>
<li>Nichols, S. M., Gierbolini, L., Gonzalez-Martinez, J. A., Bavister, B. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+in+vitro+maturation+and+age+on+oocyte+quality+in+the+rhesus+macaque+Macaca+mulatta%5BTitle%5D)+AND+%22Fertil+Steril%22%5BJournal%5D)">Effects of in vitro maturation and age on oocyte quality in the rhesus macaque Macaca mulatta.</a> Fertil Steril. 93 (5), 1591-1600 (2010).</li>
<li>Requena, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+impact+of+in-vitro+maturation+of+oocytes+on+aneuploidy+rate%5BTitle%5D)+AND+%22Reprod+Biomed+Online%22%5BJournal%5D)">The impact of in-vitro maturation of oocytes on aneuploidy rate.</a> Reprod Biomed Online. 18 (6), 777-783 (2009).</li>
<li>Franciosi, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In+vitro+maturation+affects+chromosome+segregation%2C+spindle+morphology+and+acetylation+of+lysine+16+on+histone+H4+in+horse+oocytes%5BTitle%5D)+AND+%22Reprod+Fertil+Dev%22%5BJournal%5D)">In vitro maturation affects chromosome segregation, spindle morphology and acetylation of lysine 16 on histone H4 in horse oocytes.</a> Reprod Fertil Dev. , (2015).</li>
<li>Franciosi, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Changes+in+histone+H4+acetylation+during+in+vivo+versus+in+vitro+maturation+of+equine+oocytes%5BTitle%5D)+AND+%22Mol+Hum+Reprod%22%5BJournal%5D)">Changes in histone H4 acetylation during in vivo versus in vitro maturation of equine oocytes.</a> Mol Hum Reprod. 18 (5), 243-252 (2012).</li>
<li>Choi, Y. H., Gibbons, J. R., Canesin, H. S., Hinrichs, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effect+of+medium+variations+%28zinc+supplementation+during+oocyte+maturation%2C+perifertilization+pH%2C+and+embryo+culture+protein+source%29+on+equine+embryo+development+after+intracytoplasmic+sperm+injection%5BTitle%5D)+AND+%22Theriogenology%22%5BJournal%5D)">Effect of medium variations (zinc supplementation during oocyte maturation, perifertilization pH, and embryo culture protein source) on equine embryo development after intracytoplasmic sperm injection.</a> Theriogenology. , (2016).</li>
<li>Hendriks, W. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Maternal+age+and+in+vitro+culture+affect+mitochondrial+number+and+function+in+equine+oocytes+and+embryos%5BTitle%5D)+AND+%22Reprod+Fertil+Dev%22%5BJournal%5D)">Maternal age and in vitro culture affect mitochondrial number and function in equine oocytes and embryos.</a> Reprod Fertil Dev. 27 (6), 957-968 (2015).</li>
<li>Carnevale, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+mare+model+for+follicular+maturation+and+reproductive+aging+in+the+woman%5BTitle%5D)+AND+%22Theriogenology%22%5BJournal%5D)">The mare model for follicular maturation and reproductive aging in the woman.</a> Theriogenology. 69 (1), 23-30 (2008).</li>
<li>Ginther, O. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+mare%3A+a+1000-pound+guinea+pig+for+study+of+the+ovulatory+follicular+wave+in+women%5BTitle%5D)+AND+%22Theriogenology%22%5BJournal%5D)">The mare: a 1000-pound guinea pig for study of the ovulatory follicular wave in women.</a> Theriogenology. 77 (5), 818-828 (2012).</li>
<li>Chiang, T., Duncan, F. E., Schindler, K., Schultz, R. M., Lampson, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Evidence+that+weakened+centromere+cohesion+is+a+leading+cause+of+age-related+aneuploidy+in+oocytes%5BTitle%5D)+AND+%22Curr+Biol%22%5BJournal%5D)">Evidence that weakened centromere cohesion is a leading cause of age-related aneuploidy in oocytes.</a> Curr Biol. 20 (17), 1522-1528 (2010).</li>
<li>Duncan, F. E., Chiang, T., Schultz, R. M., Lampson, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Evidence+that+a+defective+spindle+assembly+checkpoint+is+not+the+primary+cause+of+maternal+age-associated+aneuploidy+in+mouse+eggs%5BTitle%5D)+AND+%22Biol+Reprod%22%5BJournal%5D)">Evidence that a defective spindle assembly checkpoint is not the primary cause of maternal age-associated aneuploidy in mouse eggs.</a> Biol Reprod. 81 (4), 768-776 (2009).</li>
<li>Larionov, A., Krause, A., Miller, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+standard+curve+based+method+for+relative+real+time+PCR+data+processing%5BTitle%5D)+AND+%22BMC+Bioinformatics%22%5BJournal%5D)">A standard curve based method for relative real time PCR data processing.</a> BMC Bioinformatics. 6 (62), (2005).</li>
<li>Choi, Y. H., Hochi, S., Braun, J., Sato, K., Oguri, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In+vitro+maturation+of+equine+oocytes+collected+by+follicle+aspiration+and+by+the+slicing+of+ovaries%5BTitle%5D)+AND+%22Theriogenology%22%5BJournal%5D)">In vitro maturation of equine oocytes collected by follicle aspiration and by the slicing of ovaries.</a> Theriogenology. 40 (5), 959-966 (1993).</li>
<li>Hassold, T., Hunt, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((To+err+%28meiotically%29+is+human%3A+the+genesis+of+human+aneuploidy%5BTitle%5D)+AND+%22Nat+Rev+Genet%22%5BJournal%5D)">To err (meiotically) is human: the genesis of human aneuploidy.</a> Nat Rev Genet. 2 (4), 280-291 (2001).</li>
<li>Akiyama, T., Nagata, M., Aoki, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Inadequate+histone+deacetylation+during+oocyte+meiosis+causes+aneuploidy+and+embryo+death+in+mice%5BTitle%5D)+AND+%22Proc+Natl+Acad+Sci+U+S+A%22%5BJournal%5D)">Inadequate histone deacetylation during oocyte meiosis causes aneuploidy and embryo death in mice.</a> Proc Natl Acad Sci U S A. 103 (19), 7339-7344 (2006).</li>
<li>Homer, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mad2+prevents+aneuploidy+and+premature+proteolysis+of+cyclin+B+and+securin+during+meiosis+I+in+mouse+oocytes%5BTitle%5D)+AND+%22Genes+Dev%22%5BJournal%5D)">Mad2 prevents aneuploidy and premature proteolysis of cyclin B and securin during meiosis I in mouse oocytes.</a> Genes Dev. 19 (2), 202-207 (2005).</li>
<li>Rambags, B. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Numerical+chromosomal+abnormalities+in+equine+embryos+produced+in+vivo+and+in+vitro%5BTitle%5D)+AND+%22Mol+Reprod+Dev%22%5BJournal%5D)">Numerical chromosomal abnormalities in equine embryos produced in vivo and in vitro.</a> Mol Reprod Dev. 72 (1), 77-87 (2005).</li>
<li>Nabti, I., Marangos, P., Bormann, J., Kudo, N. R., Carroll, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Dual-mode+regulation+of+the+APC%2FC+by+CDK1+and+MAPK+controls+meiosis+I+progression+and+fidelity%5BTitle%5D)+AND+%22J+Cell+Biol%22%5BJournal%5D)">Dual-mode regulation of the APC/C by CDK1 and MAPK controls meiosis I progression and fidelity.</a> J Cell Biol. 204 (6), 891-900 (2014).</li>
<li>Shomper, M., Lappa, C., FitzHarris, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Kinetochore+microtubule+establishment+is+defective+in+oocytes+from+aged+mice%5BTitle%5D)+AND+%22Cell+Cycle%22%5BJournal%5D)">Kinetochore microtubule establishment is defective in oocytes from aged mice.</a> Cell Cycle. 13 (7), 1171-1179 (2014).</li>
<li>Luzzo, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((High+fat+diet+induced+developmental+defects+in+the+mouse%3A+oocyte+meiotic+aneuploidy+and+fetal+growth+retardation%2Fbrain+defects%5BTitle%5D)+AND+%22PLoS+One%22%5BJournal%5D)">High fat diet induced developmental defects in the mouse: oocyte meiotic aneuploidy and fetal growth retardation/brain defects.</a> PLoS One. 7 (11), e49217(2012).</li>
<li>Ma, P., Schultz, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Histone+deacetylase+2+%28HDAC2%29+regulates+chromosome+segregation+and+kinetochore+function+via+H4K16+deacetylation+during+oocyte+maturation+in+mouse%5BTitle%5D)+AND+%22PLoS+Genet%22%5BJournal%5D)">Histone deacetylase 2 (HDAC2) regulates chromosome segregation and kinetochore function via H4K16 deacetylation during oocyte maturation in mouse.</a> PLoS Genet. 9 (3), e1003377(2013).</li>
<li>Yang, F., Baumann, C., Viveiros, M. M., De La Fuente, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Histone+hyperacetylation+during+meiosis+interferes+with+large-scale+chromatin+remodeling%2C+axial+chromatid+condensation+and+sister+chromatid+separation+in+the+mammalian+oocyte%5BTitle%5D)+AND+%22Int+J+Dev+Biol%22%5BJournal%5D)">Histone hyperacetylation during meiosis interferes with large-scale chromatin remodeling, axial chromatid condensation and sister chromatid separation in the mammalian oocyte.</a> Int J Dev Biol. 56 (10-12), 889-899 (2012).</li>
<li>Luciano, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Oocytes+isolated+from+dairy+cows+with+reduced+ovarian+reserve+have+a+high+frequency+of+aneuploidy+and+alterations+in+the+localization+of+progesterone+receptor+membrane+component+1+and+aurora+kinase+B%5BTitle%5D)+AND+%22Biol+Reprod%22%5BJournal%5D)">Oocytes isolated from dairy cows with reduced ovarian reserve have a high frequency of aneuploidy and alterations in the localization of progesterone receptor membrane component 1 and aurora kinase B.</a> Biol Reprod. 88 (3), 58(2013).</li>
<li>Luciano, A. M., Lodde, V., Franciosi, F., Ceciliani, F., Peluso, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Progesterone+receptor+membrane+component+1+expression+and+putative+function+in+bovine+oocyte+maturation%2C+fertilization%2C+and+early+embryonic+development%5BTitle%5D)+AND+%22Reproduction%22%5BJournal%5D)">Progesterone receptor membrane component 1 expression and putative function in bovine oocyte maturation, fertilization, and early embryonic development.</a> Reproduction. 140 (5), 663-672 (2010).</li>
<li>Terzaghi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((PGRMC1+participates+in+late+events+of+bovine+granulosa+cells+mitosis+and+oocyte+meiosis%5BTitle%5D)+AND+%22Cell+Cycle%22%5BJournal%5D)">PGRMC1 participates in late events of bovine granulosa cells mitosis and oocyte meiosis.</a> Cell Cycle. , 1-14 (2016).</li>
<li>Susor, A., Jansova, D., Anger, M., Kubelka, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Translation+in+the+mammalian+oocyte+in+space+and+time%5BTitle%5D)+AND+%22Cell+Tissue+Res%22%5BJournal%5D)">Translation in the mammalian oocyte in space and time.</a> Cell Tissue Res. 363 (1), 69-84 (2016).</li>
<li>Chen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Genome-wide+analysis+of+translation+reveals+a+critical+role+for+deleted+in+azoospermia-like+%28Dazl%29+at+the+oocyte-to-zygote+transition%5BTitle%5D)+AND+%22Genes+Dev%22%5BJournal%5D)">Genome-wide analysis of translation reveals a critical role for deleted in azoospermia-like (Dazl) at the oocyte-to-zygote transition.</a> Genes Dev. 25 (7), 755-766 (2011).</li>
<li>Ma, J., Flemr, M., Strnad, H., Svoboda, P., Schultz, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Maternally+recruited+DCP1A+and+DCP2+contribute+to+messenger+RNA+degradation+during+oocyte+maturation+and+genome+activation+in+mouse%5BTitle%5D)+AND+%22Biol+Reprod%22%5BJournal%5D)">Maternally recruited DCP1A and DCP2 contribute to messenger RNA degradation during oocyte maturation and genome activation in mouse.</a> Biol Reprod. 88 (1), 11(2013).</li>
</ol>

The authors have nothing to disclose.

Even though IVM has been performed in horses for more than 20 years16, we do not yet know whether the oocyte can be the origin of embryonic aneuploidy, as has been proposed for humans17. The reason is probably that the preparation of oocyte spreads for chromosome counting results in considerable sample loss. With this in mind, a survey of the methods used for investigating errors in chromosome segregation was conducted to search for the most appropriate technique to apply t...

A vast array of assisted reproduction techniques has been developed to treat infertility in women, companion animals, and endangered species. One of the most common procedures in clinical settings is the retrieval of metaphase II (MII)-stage oocytes from the ovarian follicles by ultrasound-guided transvaginal aspiration, ovum pick-up (OPU)1. These oocytes are then fertilized in vitro (IVF), with the resulting embryo(s) implanted in a recipient uterus. The MII-stage (mature) oocytes are retrieved following the administration of exogenous gonadotropins. However, this treatment is associated, in some patients, with the development of ovarian hyperstimulation syndrome (OHSS)2.
Taking advantage of the intrinsic ability of fully-grown, immature oocytes (GV-stage) to spontaneously resume meiosis once isolated from their follicles, it is possible to obtain mature oocytes without administering gonadotropin3. This procedure is called oocyte in vitro maturation (IVM) and represents a less drug-oriented, less expensive, and more patient-friendly approach to assisted reproductive technology. However, the success of embryo development with in vitro-matured oocytes is generally lower than with in vivo matured oocytes4,5. A possible explanation is that in vitro matured oocytes are more affected by errors in chromosome segregation, and the resulting aneuploidy impairs normal embryonic development6.
Understanding the molecular basis of chromosomal mis-segregation during IVM would ultimately disclose the full potential of this technique. In this vein, the experimental approach used to investigate the morphological and biochemical features of in vitro-matured oocytes, compared to in vivo matured oocytes is here described7,8. Specifically, the procedures for the OPU of immature and mature oocytes and the IVM of immature oocytes are illustrated using adult and naturally-cycling horses as an experimental model. Then, immunofluorescence and image analysis are used to investigate chromosome segregation, spindle morphology, and the global pattern of histone acetylation on these gametes. Finally, a protocol of reverse-transcription and quantitative PCR is described for the analysis of mRNA expression.
Compared with rodent animal models, horses do not allow genetic manipulation, are less easy to manipulate, and require expensive maintenance. However, this model is gaining considerable interest for the study of oocyte maturation9,10 due to the similarity to human ovarian physiology11,12. Moreover, the development of reliable protocols of IVM-IVF in the horse has a substantial economic interest, as it would allow for an increase in the number of foals from mares of high genetic value.
One of the limitations of performing experiments on oocytes, especially in monovulatory species, is the restricted sample availability. This limit has been overcome here by adjusting an approach, previously developed in mice, to horse oocytes13,14 in order to conduct chromosome counting that minimizes the sample loss (see the discussion for a comparison with other available techniques). Moreover, a triple-fluorescence staining protocol has been optimized to conduct multiple analyses on the same sample, and q-PCR analyses were performed on pools of 2 oocytes only.
Overall, the present study describes an experimental approach aimed to morphologically and biochemically characterize the horse oocyte, a cell type that is extremely challenging to study due to the low sample availability. However, it can expand our knowledge of the reproductive biology and infertility of monovulatory species.

<table><tbody><tr><td>ultrasound probe</td><td>Aloka</td><td>UST-5820-7,5</td><td></td></tr><tr><td>human chorionic gonadotrophin</td><td>centravet</td><td>CHO004</td><td>1,500 unit/animal IV</td></tr><tr><td>detomidine</td><td>centravet</td><td>MED010</td><td>9 - 15 &amp;micro;g/kg IV</td></tr><tr><td>butylscopolamine bromure</td><td>centravet</td><td>EST001</td><td>0.2 mg/kg IV</td></tr><tr><td>stereomicroscope</td><td>NIKON</td><td>SMZ-2B</td><td></td></tr><tr><td>butorphanol</td><td>centravet</td><td>DOL003</td><td>10&amp;micro;g/kg IV</td></tr><tr><td>benzyl-penicillin</td><td>centravet</td><td>DEP203 IM</td><td>15,000 UI/animal</td></tr><tr><td>TCM199</td><td>Sigma-Aldrich</td><td>M3769 10X1L</td><td>powder for hepes-buffered TCM199</td></tr><tr><td>Hepes sodium salt</td><td>Sigma-Aldrich</td><td>H3784-100G</td><td></td></tr><tr><td>bovine serum albumin</td><td>Sigma-Aldrich</td><td>A8806</td><td></td></tr><tr><td>heparin&amp;nbsp;</td><td>Sigma-Aldrich</td><td>H3149-10KU</td><td></td></tr><tr><td>NaHCO&lt;sub&gt;3&lt;/sub&gt;-buffered TCM199</td><td>Sigma-Aldrich</td><td>M2154-500ML</td><td>liquid for IVM medium</td></tr><tr><td>epidermal growth factor</td><td>Sigma-Aldrich</td><td>E4127</td><td></td></tr><tr><td>newborn calf serum</td><td>Sigma-Aldrich</td><td>N4762-500ML</td><td></td></tr><tr><td>4-well dishes</td><td>NUNCLON</td><td>144444</td><td></td></tr><tr><td>incubator</td><td>Heraeus</td><td>BB6060</td><td></td></tr><tr><td>monastrol</td><td>Sigma-Aldrich</td><td>M8515</td><td></td></tr><tr><td>hyaluronidase</td><td>Sigma-Aldrich</td><td>H3506</td><td></td></tr><tr><td>pronase</td><td>Sigma-Aldrich</td><td>P5147</td><td></td></tr><tr><td>paraformaldehyde</td><td>Sigma-Aldrich</td><td>P6148</td><td></td></tr><tr><td>polyvinyl alcohol</td><td>Sigma-Aldrich</td><td>341584</td><td></td></tr><tr><td>triton-X 100</td><td>Sigma-Aldrich</td><td>T8787</td><td></td></tr><tr><td>normal donkey serum</td><td>Sigma-Aldrich</td><td>D9663</td><td></td></tr><tr><td>rabbit anti-Aurora B phospho-Thr232</td><td>BioLegend</td><td>636102</td><td></td></tr><tr><td>TRITC-conjugated donkey anti-rabbit IgG</td><td>Vector Laboratories</td><td>711-025-152</td><td></td></tr><tr><td>Vecta-Shield</td><td>Vector Laboratories</td><td>H-1000</td><td></td></tr><tr><td>YOPRO1</td><td>Thermofisher Scientific</td><td>Y3603</td><td></td></tr><tr><td>confocal laser scanning microscope</td><td>LSM 780</td><td>Zeiss</td><td></td></tr><tr><td>confocal laser scanning microscope</td><td>LSM 700</td><td>Zeiss</td><td></td></tr><tr><td>ImageJ software</td><td>rsb.info. nih.gov/ij/download.html</td><td>free resource</td><td></td></tr><tr><td>mouse anti-alpha-tubulin</td><td>Sigma-Aldrich</td><td>T8203</td><td></td></tr><tr><td>rabbit anti-acH4K16</td><td>Upstate Biotechnology</td><td>07-329</td><td></td></tr><tr><td>AlexaFluor 488-coniugated donkey anti-mouse IgG</td><td>Life Technologies</td><td>A21202</td><td></td></tr><tr><td>4&amp;rsquo;,6-diamidino-2-phenylindole</td><td>Sigma-Aldrich</td><td>D8417</td><td>DAPI</td></tr><tr><td>centrifuge</td><td>Eppendorf</td><td>5417R</td><td></td></tr><tr><td>RNALater</td><td>Invitrogen</td><td>AM7020</td><td></td></tr><tr><td>Luciferase RNA</td><td>Promega</td><td>L4561</td><td></td></tr><tr><td>PicoPure RNA Isolation Kit</td><td>Applied Biosystems</td><td>12204-01</td><td></td></tr><tr><td>random hexamers</td><td>Thermofisher Scientific</td><td>N8080127</td><td></td></tr><tr><td>mouse Moloney leukaemia virus reverse transcriptase</td><td>Thermofisher Scientific</td><td>28025013</td><td></td></tr><tr><td>SYBR green supermix</td><td>BioRad</td><td>1708880</td><td></td></tr><tr><td>specific primers</td><td>Sigma-Aldrich</td><td></td><td>specific primers were designed using Primer3Plus software (free resource)</td></tr><tr><td>thermal-cycler</td><td>BioRad</td><td>MyiQ</td><td></td></tr><tr><td>mouse monoclonal anti-CENPA</td><td>Abcam</td><td>ab13939</td><td></td></tr><tr><td>mouse monoclonal anti-Aurora B</td><td>Abcam</td><td>ab3609</td><td></td></tr></tbody></table>

analysis of chromosome segregation, histone acetylation, and spindle morphology in horse oocytes

Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes

The field of assisted reproduction has been developed to treat infertility in women, companion animals, and endangered species. In the horse, assisted reproduction also allows for the production of embryos from high performers without interrupting their sports career and contributes to an increase in the number of foals from mares of high genetic value. The present manuscript describes the procedures used for collecting immature and mature oocytes from horse ovaries using ovum pick-up (OPU). These oocytes were then used to investigate the incidence of aneuploidy by adapting a protocol previously developed in mice. Specifically, the chromosomes and the centromeres of metaphase II (MII) oocytes were fluorescently labeled and counted on sequential focal plans after confocal laser microscope scanning. This analysis revealed a higher incidence in the aneuploidy rate when immature oocytes were collected from the follicles and matured in vitro compared to in vivo. Immunostaining for tubulin and the acetylated form of histone four at specific lysine residues also revealed differences in the morphology of the meiotic spindle and in the global pattern of histone acetylation. Finally, the expression of mRNAs coding for histone deacetylases (HDACs) and acetyl-transferases (HATs) was investigated by reverse transcription and quantitative-PCR (q-PCR). No differences in the relative expression of transcripts were observed between in vitro and in vivo matured oocytes. In agreement with a general silencing of the transcriptional activity during oocyte maturation, the analysis of the total transcript amount can only reveal mRNA stability or degradation. Therefore, these findings indicate that other translational and post-translational regulations might be affected.
Overall, the present study describes an experimental approach to morphologically and biochemically characterize the horse oocyte, a cell type that is extremely challenging to study due to low sample availability. However, it can expand our knowledge on the reproductive biology and infertility in monovulatory species.

The original findings of these experiments were described in depth previously7 and are reported herein as an example of results that can be obtained using the described protocols.
Maturation rate
Of the 32 COCs retrieved by OPU from dominant follicles, 28 (88%) were at the MII stage. Fourteen of the 58 COCs collected from follicles 5-25 mm in size ...

This manuscript describes an experimental approach to morphologically and biochemically characterize horse oocytes. Specifically, the present work illustrates how to collect immature and mature horse oocytes by ultrasound-guided ovum pick-up (OPU) and how to investigate chromosome segregation, spindle morphology, global histone acetylation, and mRNA expression.

The field of assisted reproduction has been developed to treat infertility in women, companion animals, and endangered species. In the horse, assisted ...

The overall goals of this experimental approach are to, first, morphologically and biochemically characterize horse oocytes and, second, to compare gametes from the same animal that were processed in vitro or in vivo. This experimental approach can help answer key questions in oocyte biology and fertility in monovulatory species. It might also improve the safety of gamete manipulation procedures.This approach was developed to overcome the restricted sample availability of oocytes, especially from monovulatory species. Demonstrating the OPU procedures will be Professor Stefan Deleuze of the University of Liege, Cecile Douet, the lab manager of my lab, and Fabrice Reigner, the manager of the equine unit at the INRA Centre Val de Loire. On a daily basis, assess the diameter of the ovarian follicles in a cohort of adult mares using ultrasound.Search for a large follicle with a diameter greater than 33 millimeters. Once found, prepare to inject 1, 500 units of human chorionic gonadotropin to induce the maturation of the oocyte into a dominant follicle. Next, locate the jugular furrow, and swab the injection site with alcohol.Then, to make the vein rise, apply some force two or three centimeters below the site of injection. Insert the needle almost parallel to the neck, aspirate slightly to ensure that the needle is in the vein, and inject the hormone. Prepare an ultrasound probe for vaginal access.Then, connect the needle to a suction system. 35 hours after hCG injection, set up the instrumentation for OPU, and sedate the mare. Good analgesia is extremely important for the animal's and the operator's safety.An animal that does not feel pain or discomfort will allow manipulation of the ovary, making punctures and flushes easier to perform. Once the needle probe is inserted, one operator must manipulate the ovary to face the probe while the other operator manipulates the needle. Locate the dominant follicle in the echographic image.Then, use the needle to pierce the vaginal wall and the wall of the dominant follicle. Once the follicle space is accessed, aspirate the follicular fluid. Rotate the needle to scrape the follicular wall and attach the cumulus-oocyte complex.Then, pour the fluid into a large petri dish. And under a stereoscope, search for the COC. Meanwhile, flush out the follicle with warm Dulbecco's modified PBS containing heparin.It may take several flushes to collect the COC. After the COC is found, change the needle to a double-lumen needle and collect the immature COCs from all of the follicles that are between five and 25 millimeters in diameter. These will be used for in vitro maturation.Once all of the follicles from one ovary are aspirated, repeat the same procedures to collect the immature COCs from the other ovary. Now, choose between the COCs. Keep only COCs with several complete layers of cumulus cells and a brown, finely-granulated ooplasm.Discard the others. At the end of the procedure, inject the mare with 15, 000 units of benzyl-penicillin to prevent infection. Then, house the mare in a quiet, clean stable for at least two hours while she recovers.Before the OPU starts, warm a bottle of supplemented HEPES-buffered TCM-199 to 37 degrees Celsius. Next, prepare the IVM medium. Dispense 500 microliters of supplemented sodium bicarbonate-buffered TCM-199 into the wells of a four-well dish.Then, incubate the dish at 38.5 degrees Celsius for at least two hours. Transfer the recovered immature COCs to a 3.5-centimeter dish filled with two milliliters of the warmed HEPES TCM-199. Move the COCs through different regions of the dish to gently wash away surrounding debris.Now, transfer the COCs to the IVM medium, and incubate them for 28 hours at 38.5 degrees Celsius. To perform a chromosome count on mature COCs, incubate them in 100-micromolar monastrol for an hour at 38.5 degrees Celsius. Next, remove the cumulus cells by treating the COCs with 0.5%hyaluronidase in HEPES-buffered TCM-199.Monitor this reaction on a heated stage set to 38 degrees Celsius. Within about five minutes, remove all of the cells. Use gentle pipetting to remove the last few stubborn cells.Next, remove the zona pellucida using 0.2%pronase in HEPES-buffered TCM-199. Monitor this reaction on a heated stage as well. It should take about five minutes to complete.Then, fix the oocytes in 4%paraformaldehyde in DPBS for 15 minutes at 38.5 degrees Celsius, followed by 45 more minutes of fixation at four degrees Celsius. After the fixation, wash the oocytes by sequentially transferring them between three wells of 0.1%polyvinyl alcohol in DPBS. Use about half a milliliter of solution per well.Then, transfer the oocytes to a well filled with 0.3%Triton X-100 in PBS, and let them incubate for 10 minutes at room temperature. To block non-specific signals, bathe the cells in DPBS with 1%BSA and 10%normal donkey serum. Incubate the cells for at least 30 minutes at room temperature.After 30 minutes, apply the primary antibody, and then incubate the cells at four degrees Celsius overnight. The following day, wash the oocytes, and apply the secondary antibody for an hour at room temperature, shielded from light exposure. After applying the secondary, wash the oocytes again.Then, before mounting, attach double-sided tape strips to slides to serve as coverslip supports. Now, mount the oocytes three to four per slide in a drop of non-hardening, antifade mounting medium supplemented with 20 micromolar of YO-PRO-1. Allow the oocytes to settle for about 10 minutes, and then apply the coverslips.Out of 32 COCs retrieved by OPU from dominant follicles, 28 were in metaphase II.Using in vitro maturation, 37 of 44 COCs collected from non-dominant follicles were matured to metaphase II.The chromosomes of both groups were then compared. The in vitro-matured oocytes were often affected by aneuploidy, mostly hyperploidy. This was not observed in the in vivo-matured oocytes.Next, the pole-to-pole spindle length and the diameter of the spindle at its maximum were both measured. The in vitro-matured oocytes were significantly longer and wider than the in vivo-matured oocytes. In the same samples, the global acetylation level of H4K16 was measured.The results were as expected. Acetylation of H4K16 was significantly lower in in vitro-matured oocytes than in in vivo-matured oocytes. A well-trained team can process five mares in a morning of OPU with an 80%retrieval rate for the preovulatory oocyte and 50 to 60%retrieval of the immature oocytes.During the OPU, always monitor the ess and well-being of the animal, and be ready to provide adequate veterinary care if needed. The experimental approach can be applied to oocytes of other species as well and is especially applicable where samples availability is an issue, such as with humans. Based on our results, studies must be undertaken to better understand the culture conditions needed for proper chromosome segregation and epigenetic changes.The overarching goal is to improve in vitro maturation efficiency for both veterinary medicine and human fertility treatment.

analysis-chromosome-segregation-histone-acetylation-spindle

Research

JoVE Journal

Developmental Biology

Oocytes are prone to aneuploidy due to errors in chromosome segregation during meiotic maturation.  Aneuploid eggs can cause infertility, miscarriages or developmental disorders like Down syndrome.  Here, we describe methods to introduce materials of choice into oocytes and methods to study meiotic maturation and assess ploidy.

Mouse Oocyte Microinjection, Maturation and Ploidy Assessment

Here, we present a protocol for specific siRNA-mediated mRNA depletion followed by immunofluorescence analysis to evaluate meiotic spindle assembly and organization in mouse oocytes. This protocol is suitable for in vitro depletion of transcripts and functional assessment of different spindle and/or MTOC-associated factors in oocytes.

Meiotic Spindle Assessment in Mouse Oocytes by siRNA-mediated Silencing

Here we present a protocol for the characterization of mouse antral oocytes based on nucleolar organization.

Isolation and Characterization of Mouse Antral Oocytes Based on Nucleolar Chromatin Organization

Oogenesis in mammals is known to be error-prone, particularly due to chromosome missegregation. This manuscript describes chromatin spread preparation methods for mouse prophase, metaphase I and II-staged oocytes. These fundamental techniques allow for the study of chromatin-bound proteins and chromosome morphology throughout mammalian oogenesis.

Chromatin Spread Preparations for the Analysis of Mouse Oocyte Progression from Prophase to Metaphase II

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

As the genetic variants associated with human disease begin to become uncovered, it is becoming increasingly important to develop systems with which to rapidly evaluate the biological significance of those identified variants. This protocol describes methods for evaluating human gene function during female meiosis I using mouse oocytes.

Using Mouse Oocytes to Assess Human Gene Function During Meiosis I

We provide an outline of the clinical protocol for non-invasive assessment of human egg maturity using polarized light microscopy.

Human Egg Maturity Assessment and Its Clinical Application

An optimized protocol is presented that enables the depletion of cytoplasmic microtubule organizing centers in mouse oocytes during metaphase I using a near-infrared femtosecond laser.

Multi-Photon Laser Ablation of Cytoplasmic Microtubule Organizing Centers in Mouse Oocytes

Error in chromosome segregation is a common feature in oocytes. Therefore, studying the spindle assembly checkpoint gives important clues about the mechanisms needed to produce healthy eggs. The present protocol describes three complementary assays to evaluate spindle assembly checkpoint integrity in mouse oocytes.

Evaluation of the Spindle Assembly Checkpoint Integrity in Mouse Oocytes

Figure 1: End-to-end framework. The figure illustrates end-to-end framework for multimodal knowledge Graph VISHAM-KG. Please click here to view a larger version of this figure.

Preparation of Meiotic Chromosome Spreads from Mouse Oocytes for Assessment of Synapsis and Recombination

Learn ultrasound-guided ovum pick-up (OPU) to characterize horse oocytes through chromosome segregation, spindle morphology, and histone acetylation analysis. This method advances fertility research in monovulatory species.

Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes

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