Name: using mouse oocytes to assess human gene function during meiosis i
Uploaded: 2018-04-10T15:00:00.000+00:00
Duration: 11 min 13 s
Description: Watch this Scientific Journal Video about Using Mouse Oocytes to Assess Human Gene Function During Meiosis I at JoVE.com

This work was supported by a Research Grant from the American Society for Reproductive Medicine and from the Charles and Johanna Busch Memorial Fund at Rutgers, The State University of NJ to K.S. A.L.N. was supported by a grant from the N.I.H. (F31 HD0989597).

1. Molecular Cloning
<ol>
	<li>Obtain full-length coding sequence of the gene of interest and the plasmid in vitro transcription (pIVT) vector11. 
	NOTE: Full-length cDNA clones are commercially available from various vendors or can be generated via reverse transcription polymerase chain reaction (RT-PCR). The National Center for Biotechnology Information (NCBI) online resource provides transcript sequences for genes from the Nucleotide and Expressed sequence tagged (EST) databases. For ease of protein visualization and analysis of expression levels, fusion to green fluorescent protein (Gfp) or another suitable fluorescent tag may be desired in the cloning strategy.</li>
	<li>Using a validated cloning strategy, insert the coding sequence of the gene of interest into the multiple cloning region of pIVT. A detailed description of molecular cloning and the required steps have previously been described 12. 
	NOTE: If a gene-fusion product is to be generated, be sure that the cloning is in the proper reading frame.</li>
	<li>Sequence the construct using Globin primers to ensure correct gene insertion, proper in-frame fusion, and that no polymerase-induced point mutations were created. 
	NOTE: If Sanger DNA sequencing equipment is not available, many companies offer low cost DNA sequencing options.</li>
	<li>Mutagenize DNA if generating single nucleotide polymorphisms (SNPs) or insertions/deletions (INDELS). DNA mutagenesis is described in steps 1.5-1.7 below. For wild-type constructs, proceed with the linearization step 1.7.</li>
	<li>Design mutagenesis primers and complete the mutagenesis PCR reaction to generate mutant construct per manufacturer&#39;s protocol. PCR-mediated site-directed mutagenesis has been previously described 13. Additionally, many companies offer site-directed mutagenesis kits which include protocols.</li>
	<li>Transform mutagenized DNA into bacterial host. Isolate and purify plasmid. 
	NOTE: Many companies make kits that can be used to easily isolate and purify plasmid DNA. Follow manufacturers protocol accordingly. If using a gram-negative bacterial strain such as E. coli, it is recommended to use a kit that removes endotoxins.</li>
	<li>Sequence the isolated DNA from bacterial transformants using standard Sanger DNA sequencing to confirm introduction of the desired SNP or INDEL.</li>
	<li>Linearize final products using single restriction enzyme digestion of the purified DNA. 
	NOTE: The pIVT vector contains multiple single-enzyme cut sites listed in the plasmid map on Addgene 14.</li>
	<li>Ensure that the product is linear via agarose gel electrophoresis. The methodology for agarose gel electrophoresis has previously been defined 14. 
	NOTE: For all remaining steps, use barrier (filter) pipet tips and RNase-free materials to ensure production of stable, high quality RNA.</li>
	<li>Purify the digested product using a validated DNA clean-up protocol or kit, and elute in 30 &#181;L RNase/DNase-free water. 
	NOTE: Silica-matrix spin column-based kits are recommended for high quality, purified DNA. Follow manufacturers protocol accordingly.</li>
	<li>In vitro transcribe DNA using T7 polymerase following the manufacturer&#39;s protocol.</li>
	<li>Purify and elute RNA in 30 &#181;L of RNase/DNase free water using a silica-matrix spin column-based nucleic acid purification kit following the manufacturer&#39;s protocol.</li>
	<li>Perform denaturing agarose gel electrophoresis using formaldehyde to confirm the final RNA product size. See steps 1.13-1.22 below 14. (Figure 1).</li>
	<li>Prepare gel by heating 1 g agarose in 72 mL water until dissolved, then cool to 60 &#176;C.</li>
	<li>Prepare 10X MOPS running buffer by adding 0.4 M MOPS (pH 7.0), 0.1 M sodium acetate, and 0.01 M EDTA.</li>
	<li>Add 10 mL of 10X MOPS running buffer, and 18 mL of 37% formaldehyde (12.3 M) to the cooled agarose solution.</li>
	<li>Caste the gel by pouring the agarose solution into a gel-forming container. Use a comb large enough to accommodate 10 &#181;L. After gel has set and is firm to the touch, gently remove the comb.</li>
	<li>Assemble the gel in the electrophoresis tank, and add enough 1X MOPS running buffer, ensuring the gel is completely covered.</li>
	<li>Prepare RNA sample by adding 1 &#181;g of RNA to 0.5X volumes of formaldehyde-containing loading dye.</li>
	<li>Add ethidium bromide to RNA solution at a concentration of 10 &#181;g/mL.</li>
	<li>Denature RNA sample solution at 70 &#176;C for 5 min.</li>
	<li>Using sterile, 10 &#181;L filter tips, load 5 &#181;L of molecular weight marker and 5 &#181;L of RNA sample(s) into separate wells of the gel and electrophorese at 5 V/cm until the dye has migrated at least two-thirds of the length of the gel.</li>
	<li>Visualize the RNA in the gel on a UV trans illuminator. Ensure the RNA is the correct size by comparing to the molecular weight marker.</li>
	<li>To measure the concentration and purity of the RNA, transfer 1.2 &#181;L of purified RNA using sterile 10 &#181;L filter tips onto a UV-spectrophotometer. 
	Note that high quality RNA should have absorbance ratios of A260/280 (1.8-2.2) and 260/230 (&#62;1.7) respectively.</li>
	<li>Using 10 &#181;L filter tips, aliquot the remaining purified RNA into sterile 0.5 &#181;L centrifuge tubes (3-5 &#181;L/tube). Store tubes at -80 &#176;C until ready for microinjection. 
	NOTE: A final injection concentration of 500 ng/&#181;L is an optimal starting point. It is recommended to dilute RNA 1:2 in RNase free H20 prior to microinjection to reduce stickiness of RNA in microinjection pipette.</li>
</ol>
2. Kinetochore-Microtubule Attachment Assay
<ol>
	<li>Divide oocytes into equal groups for microinjection. 
	NOTE: Oocyte collection, transfer, microinjection, and meiotic maturation has been described in detail in JoVE previously 15.</li>
	<li>Microinject one group with experimental mRNA and the other group(s) with the WT control and PBS or Gfp mRNA. 
	NOTE: 500 ng/&#181;L is the recommended injection concentration to begin with 10. A picoinjector can be used to control injection amounts. An injection volume of 5-10 pL is recommended 15.</li>
	<li>Using a hand or mouth operated pipetting apparatus where the glass pipette opening is slightly larger than the diameter of an oocyte (100-150 &#181;m), transfer oocytes into a 100 &#181;L drop of milrinone-free culture medium in a Petri dish covered in embryo quality mineral oil and incubate oocytes for 7 h at 37 &#176;C in 5% C02 to allow sufficient maturation to metaphase of meiosis I (Met I) 15.</li>
	<li>After incubation, using the same pipette apparatus as above, transfer oocytes into a center-well organ culture dish containing 700 &#181;L of pre-chilled minimum essential media (MEM) collection medium in the center well and 500 &#181;L H20 in the outside ring and place dish on ice for 7 min. 
	NOTE: It is recommended to pre-chill MEM media and center well organ culture dishes at -20 &#176;C for at least 20 min prior to treatment of oocytes.</li>
	<li>Fix the oocytes by transferring them using the pipette apparatus into a well of a clear glass spot plate containing 400 &#181;L of 2% paraformaldehyde in 1X PBS for 20 min at room temperature.</li>
	<li>Using same pipette apparatus, transfer the oocytes into another well on a spot plate containing 400 &#181;L blocking solution (PBS + 0.3% BSA + 0.01% Tween-20 + 0.02% NaN3) and store at 4 &#176;C until ready to process for immunostaining. 
	NOTE: For storing oocytes at 4 &#176;C, cover glass spot plate with parafilm to prevent evaporation.</li>
	<li>Using same pipette apparatus, transfer oocytes to a new well on a spot plate containing 400 &#181;L permeabilization solution (PBS + 0.3% BSA + 0.1% TritonX-100 + 0.02% NaN3) and incubate at room temperature for 20 min. Transfer oocytes quickly through three drops of 400 &#181;L blocking solution to remove any residual detergent. 
	NOTE: A 9-well clear glass spot plate works well for moving groups through multiple treatments on a single dish (steps 2.4-2.5).</li>
	<li>Perform the remaining immunocytochemistry procedures in a humidified chamber, protected from light at room temperature. Use a medium-sized plastic container lined with damp paper towels and cover with aluminum foil.</li>
	<li>Using the pipette apparatus, transfer oocytes to 30 &#181;L blocking solution on the lid of a 96-well plate and place within the humidified chamber for 10 min. 
	NOTE: Drops are placed in the circular indentions on the plate.</li>
	<li>To label centromeres and spindle, using the pipette apparatus, transfer oocytes to 30 &#181;L blocking solution containing anti-centromeric antigen (ACA, Crest) (1:30) and anti-acetylated tubulin (1:1000) and incubate for at least 1 h.</li>
	<li>Rinse oocytes by transferring through three 30 &#181;L drops of blocking solution for 10 min each.</li>
	<li>Using the pipette apparatus, transfer oocytes to a 30 &#181;L drop of blocking solution containing secondary antibodies complimentary to the antibodies used above (anti-human IgG 1:200, anti-mouse IgG 1:200) and incubate for 1 h.</li>
	<li>Repeat the 3, 10-min rinsing steps in 30 &#181;L blocking solution as described in step 2.11.</li>
	<li>Transfer the oocytes, using the pipette apparatus, into 3-5 &#181;L mounting medium containing DAPI (5.9 &#181;g/&#181;L) on a glass microscope slide.</li>
	<li>Place 4 small drops (size of a pin head) of petroleum jelly on the corners of the cover slip to prevent crushing of the oocytes.</li>
	<li>Gently place the cover slip petroleum-jelly side down onto the slide.</li>
	<li>Seal coverslip edges with clear nail polish and allow to dry for 5 min.</li>
	<li>Store slides at 4 &#176;C, protected from light, until processing via confocal microscopy. 
	NOTE: Ensure the refractive index of mounting medium, and coverslip, matches the microscope objectives being utilized. Recommended mounting materials have previously been described 15.</li>
	<li>Image oocytes using a 40-63x objective on a confocal microscope, capturing small steps (&#8804; 1 &#181;m) in the z-plane, optimized for the working objective, and image the entire region of the metaphase spindle. 
	NOTE: Make sure to image all 3 channels based on specific secondary antibodies used in step 2.11. Image averaging &#8805; 4 and a zoom of 3 are ideal for adequate resolution. A 1 &#181;m step size provides clear visualization of microtubules and kinetochores in mouse oocytes. The procedure for image capture will vary from microscope to microscope. Please refer to the manufacturers confocal user guide for specific steps on how to configure microscope settings.</li>
	<li>Identify kinetochore-microtubule attachment status using imaging software following steps 2.21-2.23 below. 
	NOTE: The following steps describe this procedure using Image J (NIH) free downloadable software, however, alternate imaging software can be used. Attachment status types have previously been defined 16 .</li>
	<li>Open image by dragging file into Image J tool bar.</li>
	<li>In the opened z-series, make all channels visible (DNA, kinetochore, and spindle) by clicking &#34;merge channels&#34;, available in the &#34;Image&#34; drop-down menu, under the &#34;color&#34; sub tab.</li>
	<li>Using the toggle at the bottom of the image, move through each z-slice and determine kinetochore microtubule attachment. Detailed attachment descriptions have been previously described 16</li>
</ol>
3. Chromosome Alignment Challenge Assay
<ol>
	<li>Using the pipette apparatus as described in step 2.3, transfer oocytes into a 100 &#181;L drop of milrinone-free culture medium under oil and incubate oocytes for 7 h to allow sufficient maturation to metaphase of meiosis I (Met I) as previously described in step 2.3 17. 
	NOTE: Oocyte collection, microinjection, and maturation procedures were outlined previously 15. Refer to the attachment assay protocol in steps 2.1-2.2 for controls and for RNA microinjection concentrations.</li>
	<li>Using same pipette apparatus, transfer oocytes to a center-well organ culture dish containing 700 &#181;L culture medium containing monastrol [100 &#181;M] in the center well and 400 &#181;L H20 in the surrounding ring and incubate at 37 &#176;C for 2 h.</li>
	<li>Rinse out monastrol by transferring oocytes, using the pipette apparatus as above, through three drops of 100 &#181;L CZB culture medium, and then transfer the oocytes to a new center-well organ culture dish containing 700 &#181;L culture medium + MG132 [5 &#181;M] for 3 h in the center ring. Add 400 &#181;L H20 to the outside ring.</li>
	<li>Fix the oocytes by transferring them, using the pipette apparatus, into a well of a clear glass spot plate containing 400 &#181;L 2% paraformaldehyde in PBS for 20 min at room temperature.</li>
	<li>After fixation, transfer the oocytes, using the pipette apparatus, into a new well of a clear glass spot plate containing 400 &#181;L blocking solution and store at 4 &#176;C until processed for immunostaining. 
	NOTE: For storing oocytes at 4 &#176;C, cover glass spot plate with parafilm to prevent evaporation.</li>
	<li>Permeabilize and label oocytes via immunocytochemistry as described in steps 2.6-2.16.</li>
	<li>Image oocytes using a 40-63x objective on a confocal microscope, capturing &#60;1 &#181;m steps in the z-plane making sure to image the entire region of the metaphase spindle.</li>
	<li>To identify chromosome alignment status open image files using imaging software. 
	NOTE: The following steps describe this procedure using Image J (NIH) free downloadable software, however, alternate imaging software can be used.</li>
	<li>Drag image into image J control panel.</li>
	<li>In the opened z-series, use the point tool (available by clicking the point tool icon on the Image J control bar) to mark points at the end of each spindle pole in their respective z-slice by placing the tool over the spindle pole in the image and clicking on the image. Add these points to the Region of interest (ROI) manager by pressing Command+t on the keyboard.</li>
	<li>Determine the specific coordinates for each of the positions set in step 3.10 by highlighting the specific point in the ROI manager and clicking the measure button. This will provide a results table-containing x and y coordinates for each point. These will be the X1, Y1, and X1, Y2, points respectively.</li>
	<li>Next, determine the true Z coordinate. This is done by multiplying the slice number of the specific z-slice in the z-stack in which the spindle pole was identified (i.e. slice #2 of 6) that each individual point is in by the stack thickness (i.e. 1 &#181;m) (example: slice 2 x 1 &#181;m = 2). These will be the Z1 and Z2 points respectively.</li>
	<li>Determine spindle length using the Pythagorean theorem equation (a2 + b2 = c2) using the previously defined x, y, and z coordinates from steps 3.11-3.13. For each spindle the final length is equal to: 
	&#8730;((X1-X2)2+(Y1-Y2)2+(Z1-Z2)2)</li>
	<li>Determine the spindle midzone. This is calculated as one half the length of the spindle. Using the line tool in Image J, by clicking the line icon in the Image J tool bar, draw a line that is from one spindle pole to the spindle midzone. The length will be displayed on the Image J tool bar.</li>
	<li>Determine chromosome alignment status by assessing chromosome distance from the spindle midzone using the line measurement tool. Using the line tool available by clicking the line icon in the Image J tool bar, draw a line from the spindle midzone to the chromosome. The length will be displayed on the Image J tool bar. Chromosomes greater than 4 &#181;m from the spindle midzone are considered unaligned 18.</li>
</ol>

<ol>
	<li>Thoma, M. E., 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=Prevalence+of+infertility+in+the+United+States+as+estimated+by+the+current+duration+approach+and+a+traditional+constructed+approach.">Prevalence of infertility in the United States as estimated by the current duration approach and a traditional constructed approach.</a> Fertil Steril. 99 (5), 1324-1331 (2013).</li><li>Boivin, J., Bunting, L., Collins, J. A., Nygren, K. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=International+estimates+of+infertility+prevalence+and+treatment-seeking:+potential+need+and+demand+for+infertility+medical+care.">International estimates of infertility prevalence and treatment-seeking: potential need and demand for infertility medical care.</a> Human Reproduction. 22 (6), 1506-1512 (2007).</li><li>Treff, N. R., Zimmerman, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+Preimplantation+Genetic+Testing+for+Monogenic+Disease+and+Aneuploidy.">Advances in Preimplantation Genetic Testing for Monogenic Disease and Aneuploidy.</a> Annu Rev Genomics Hum Genet. , (2017).</li><li>Franasiak, J. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+nature+of+aneuploidy+with+increasing+age+of+the+female+partner:+a+review+of+15,169+consecutive+trophectoderm+biopsies+evaluated+with+comprehensive+chromosomal+screening.">The nature of aneuploidy with increasing age of the female partner: a review of 15,169 consecutive trophectoderm biopsies evaluated with comprehensive chromosomal screening.</a> Fertil Steril. 101 (3), 656-663 (2014).</li><li>Hassold, T., Hunt, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=To+err+(meiotically)+is+human:+the+genesis+of+human+aneuploidy.">To err (meiotically) is human: the genesis of human aneuploidy.</a> Nat Rev Genet. 2 (4), 280-291 (2001).</li><li>Scott, R. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blastocyst+biopsy+with+comprehensive+chromosome+screening+and+fresh+embryo+transfer+significantly+increases+in+vitro+fertilization+implantation+and+delivery+rates:+a+randomized+controlled+trial.">Blastocyst biopsy with comprehensive chromosome screening and fresh embryo transfer significantly increases in vitro fertilization implantation and delivery rates: a randomized controlled trial.</a> Fertil Steril. 100 (3), 697-703 (2013).</li><li>Scott, R. T., Upham, K. M., Forman, E. J., Zhao, T., Treff, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cleavage-stage+biopsy+significantly+impairs+human+embryonic+implantation+potential+while+blastocyst+biopsy+does+not:+a+randomized+and+paired+clinical+trial.">Cleavage-stage biopsy significantly impairs human embryonic implantation potential while blastocyst biopsy does not: a randomized and paired clinical trial.</a> Fertil Steril. 100 (3), 624-630 (2013).</li><li>Yang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selection+of+single+blastocysts+for+fresh+transfer+via+standard+morphology+assessment+alone+and+with+array+CGH+for+good+prognosis+IVF+patients:+results+from+a+randomized+pilot+study.">Selection of single blastocysts for fresh transfer via standard morphology assessment alone and with array CGH for good prognosis IVF patients: results from a randomized pilot study.</a> Mol Cytogenet. 5 (1), 24 (2012).</li><li>Rubio, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+fertilization+with+preimplantation+genetic+diagnosis+for+aneuploidies+in+advanced+maternal+age:+a+randomized,+controlled+study.">In vitro fertilization with preimplantation genetic diagnosis for aneuploidies in advanced maternal age: a randomized, controlled study.</a> Fertil Steril. 107 (5), 1122-1129 (2017).</li><li>Nguyen, A. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+characterization+of+Aurora+Kinase+B+and+C+variants+associated+with+maternal+aneuploidy.">Identification and characterization of Aurora Kinase B and C variants associated with maternal aneuploidy.</a> Mol Hum Reprod. , (2017).</li><li>Igarashi, H., Knott, J. G., Schultz, R. M., Williams, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alterations+of+PLCbeta1+in+mouse+eggs+change+calcium+oscillatory+behavior+following+fertilization.">Alterations of PLCbeta1 in mouse eggs change calcium oscillatory behavior following fertilization.</a> Dev Biol. 312 (1), 321-330 (2007).</li><li>Database, J. 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=Basic+Methods+in+Cellular+and+Molecular+Biology.+Molecular+Cloning.">Basic Methods in Cellular and Molecular Biology. Molecular Cloning.</a> JoVE. , (2017).</li><li>Carey, M. F., Peterson, C. L., Smale, S. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PCR-mediated+site-directed+mutagenesis.">PCR-mediated site-directed mutagenesis.</a> Cold Spring Harb Protoc. 2013 (8), 738-742 (2013).</li><li>Armstrong, J. A., Schulz, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Current Protocols Essential Laboratory Techniques. , (2008).</li><li>Stein, P., Schindler, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+oocyte+microinjection,+maturation+and+ploidy+assessment.">Mouse oocyte microinjection, maturation and ploidy assessment.</a> J Vis Exp. (53), (2011).</li><li>Watanabe, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Geometry+and+force+behind+kinetochore+orientation:+lessons+from+meiosis.">Geometry and force behind kinetochore orientation: lessons from meiosis.</a> Nat Rev Mol Cell Biol. 13 (6), 370-382 (2012).</li><li>Shuda, K., Schindler, K., Ma, J., Schultz, R. M., Donovan, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aurora+kinase+B+modulates+chromosome+alignment+in+mouse+oocytes.">Aurora kinase B modulates chromosome alignment in mouse oocytes.</a> Mol Reprod Dev. 76 (11), 1094-1105 (2009).</li><li>Lane, S. I., Yun, Y., Jones, K. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Timing+of+anaphase-promoting+complex+activation+in+mouse+oocytes+is+predicted+by+microtubule-kinetochore+attachment+but+not+by+bivalent+alignment+or+tension.">Timing of anaphase-promoting complex activation in mouse oocytes is predicted by microtubule-kinetochore attachment but not by bivalent alignment or tension.</a> Development. 139 (11), 1947-1955 (2012).</li><li>Nguyen, A. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorylation+of+threonine+3+on+histone+H3+by+haspin+kinase+is+required+for+meiosis+I+in+mouse+oocytes.">Phosphorylation of threonine 3 on histone H3 by haspin kinase is required for meiosis I in mouse oocytes.</a> J Cell Sci. 127 (Pt 23), 5066-5078 (2014).</li><li>Tsafriri, A., Chun, S. Y., Zhang, R., Hsueh, A. J., Conti, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oocyte+maturation+involves+compartmentalization+and+opposing+changes+of+cAMP+levels+in+follicular+somatic+and+germ+cells:+studies+using+selective+phosphodiesterase+inhibitors.">Oocyte maturation involves compartmentalization and opposing changes of cAMP levels in follicular somatic and germ cells: studies using selective phosphodiesterase inhibitors.</a> Dev Biol. 178 (2), 393-402 (1996).</li><li>Kapoor, T. M., Mayer, T. U., Coughlin, M. L., Mitchison, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+spindle+assembly+mechanisms+with+monastrol,+a+small+molecule+inhibitor+of+the+mitotic+kinesin,+Eg5.">Probing spindle assembly mechanisms with monastrol, a small molecule inhibitor of the mitotic kinesin, Eg5.</a> Eg5. J Cell Biol. 150 (5), 975-988 (2000).</li><li>Jones, K. T., Lane, S. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+causes+of+aneuploidy+in+mammalian+eggs.">Molecular causes of aneuploidy in mammalian eggs.</a> Development. 140 (18), 3719-3730 (2013).</li><li>Fellmeth, J. E., 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=Expression+and+characterization+of+three+Aurora+kinase+C+splice+variants+found+in+human+oocytes.">Expression and characterization of three Aurora kinase C splice variants found in human oocytes.</a> Mol Hum Reprod. 21 (8), 633-644 (2015).</li><li>Rieder, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+structure+of+the+cold-stable+kinetochore+fiber+in+metaphase+PtK1+cells.">The structure of the cold-stable kinetochore fiber in metaphase PtK1 cells.</a> Chromosoma. 84 (1), 145-158 (1981).</li><li>Brunet, S., 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=Kinetochore+fibers+are+not+involved+in+the+formation+of+the+first+meiotic+spindle+in+mouse+oocytes,+but+control+the+exit+from+the+first+meiotic+M+phase.">Kinetochore fibers are not involved in the formation of the first meiotic spindle in mouse oocytes, but control the exit from the first meiotic M phase.</a> J Cell Biol. 146 (1), 1-12 (1999).</li><li>Joung, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome-scale+CRISPR-Cas9+knockout+and+transcriptional+activation+screening.">Genome-scale CRISPR-Cas9 knockout and transcriptional activation screening.</a> Nat Protoc. 12 (4), 828-863 (2017).</li><li>Cong, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiplex+genome+engineering+using+CRISPR/Cas+systems.">Multiplex genome engineering using CRISPR/Cas systems.</a> Science. 339 (6121), 819-823 (2013).</li></ol>

The authors have nothing to disclose.

Because of the rapid and increasing identification of human genetic variants associated with disease, it is essential that systems are established to evaluate their biological significance. Understanding protein function in human meiosis poses particular challenges because human oocytes are precious and rare and human sperm are not amenable to genetic manipulation. Mouse oocytes are a mammalian model system valuable for evaluating human meiotic gene function 10,23</sup...

Infertility is a condition that affects 10-15% of the human population of reproductive age 1, from which nearly one-half seek medical treatment 2. Although the etiology of infertility is diverse and in many cases multifactorial, the most common genetic abnormality in humans is embryonic aneuploidy 3. Aneuploidy is defined as the deviation (either gain or loss) of the correct number of chromosomes in a cell. The phenomenon of aneuploidy in human embryos is common and increases with advanced maternal age 4,5. Four randomized controlled trials have highlighted the benefit of selecting only chromosomally normal (euploid) embryos for uterine transfer because this strategy resulted in increased implantation rates, lower miscarriage rates and a shorter time for achieving pregnancy 6,7,8,9. Therefore, understanding the etiology of human aneuploidy can have important implications in assisted reproduction.
Although pre-implantation genetic testing for aneuploidies is beneficial in infertility treatments, a thorough understanding of how aneuploidies originate is still lacking. It is widely accepted that there is a positive correlation of meiotic aneuploidies (originated during gamete production) and maternal age, however, some women present embryonic aneuploidy rates that deviate from the mean rate for their given age 4. These cases suggest that age alone is not always predictive of the risk of generating an aneuploid embryo. Other factors may play a role in increasing the risk of embryonic aneuploidy, such as gene variants.
A key aspect of investigating the potential contribution of a gene variant to aneuploidy during oocyte meiosis is to design a system to rapidly evaluate meiotic gene function. Due to ethical constraints and limited access, it is impractical to perform these experiments using human eggs. These issues can be circumvented by using mouse oocytes, and here a series of assays to assess human gene function during meiosis I are described. By microinjecting the messenger RNA (mRNA) coding for the gene variant of interest, the localization of the human protein in the mouse egg can be visualized and used to determine if the ectopic expression of the wild-type and mutated human protein results in any phenotypic alterations that could lead to aneuploidy. These phenotypes include an increase in microtubules that attach to the improper to sister kinetochore and the inability to support chromosome alignment at metaphase of meiosis I. Importantly, this protocol can be used to investigate both gain and loss of function genetic variants by establishing specific experimental conditions to challenge key events in oocyte meiosis such as spindle building and chromosome alignment 10.

<table><tbody><tr><td>0.2 mL Seal-Rite PCR tube</td><td>USA Scientific</td><td>1602-4300</td><td></td></tr><tr><td>1 kb DNA Ladder</td><td>Thermo Scientific</td><td>SM0313</td><td></td></tr><tr><td>100 bp DNA Ladder</td><td>Thermo Scientific</td><td>SM0243</td><td></td></tr><tr><td>6X DNA loading Dye</td><td>Thermo Scientific</td><td>R0611</td><td></td></tr><tr><td>9-well glass spot plate</td><td>Thomas Scientific</td><td>7812G17</td><td></td></tr><tr><td>Agarose</td><td>Sigma Aldrich</td><td>A9539</td><td></td></tr><tr><td>Albumin from bovine serum&amp;nbsp;</td><td>Sigma-Aldrich</td><td>A3294&amp;nbsp;</td><td></td></tr><tr><td>Alexa-fluor-568 conjugated anti-mouse IgG</td><td>Thermo Scientific</td><td>A21050</td><td>1:200 dilution</td></tr><tr><td>Alexa-fluor-633 conjugated anti-human IgG</td><td>Thermo Scientific</td><td>A21091</td><td>1:200 dilution</td></tr><tr><td>Ampicillin</td><td>VWR</td><td>AA0356</td><td></td></tr><tr><td>Anti-vibration table</td><td>Technical Manufacturing Corp</td><td></td><td>any standard model</td></tr><tr><td>Anti-Acetylated Tubulin antibody</td><td>Sigma Aldrich</td><td>T7451</td><td>1:100 diution</td></tr><tr><td>Anti-centromeric (CREST) antibody</td><td>Antibodies Incorportated</td><td>15-234</td><td>1:30 dilution&amp;nbsp;</td></tr><tr><td>Barrier (Filter) Pipette tips</td><td>Thermo Scientific</td><td>AM12635</td><td>Make sure compatable with your brand of pipettors. These are compatible with Eppendorf brand pipettors.&amp;nbsp;</td></tr><tr><td>BD Difco Dehydrated Culture Media: LB Agar, Miller (Luria Bertani)</td><td>Fisher Scientific</td><td>DF0445-07-6</td><td></td></tr><tr><td>BD Difco Dehydrated Culture Media: LB Broth, Miller (Luria Bertani)</td><td>Fisher Scientific</td><td>DF0446-07-5</td><td></td></tr><tr><td>Capillary tubing</td><td>Sutter</td><td>B100-75-10</td><td></td></tr><tr><td>Center Well organ culture dish</td><td>VWR</td><td>25381-141</td><td></td></tr><tr><td>CO2 tank</td><td></td><td></td><td>For incubator</td></tr><tr><td>Confocal microscope</td><td>Zeiss</td><td></td><td>any standard model</td></tr><tr><td>Centrifuge (With cooling ability)</td><td>Thomas Scientific</td><td></td><td>any standard model&amp;nbsp;</td></tr><tr><td>Cover Glass 11 x 22 mm</td><td>Thomas Scientific</td><td>6663F10</td><td></td></tr><tr><td>Coverslips</td><td>Thomas Scientific</td><td>6663-F10</td><td>thickness will vary for particular microscopes</td></tr><tr><td>DAPI</td><td>Sigma Aldrich</td><td>D9542</td><td></td></tr><tr><td>DEPC H20</td><td>Life Technologies</td><td>AM9922</td><td></td></tr><tr><td>Digital Dry Bath</td><td>Thermo Scientific</td><td>888700001</td><td></td></tr><tr><td>Easy A high fidelity cloning enzyme</td><td>Agilent</td><td>600400</td><td>For DNA cloning&amp;nbsp;</td></tr><tr><td>Enzymes for linearizing pIVT</td><td>New England Biolabs</td><td></td><td>NdeI or KasI can be used</td></tr><tr><td>Ethidium Bromide</td><td>Thermo Scientific</td><td>155585011</td><td></td></tr><tr><td>Fluorescent Microscope&amp;nbsp;</td><td></td><td></td><td>Any Fluorescent microscope may be used</td></tr><tr><td>Formaldehyde (37%)</td><td>Thermo Fisher Scientifc</td><td>9311</td><td></td></tr><tr><td>Formaldehyde RNA loading dye</td><td>Ambion</td><td>8552</td><td></td></tr><tr><td>Frosted Microscope Slides (Uncharged) 25X75 mm</td><td>Fisher Scientific</td><td>12-544-3</td><td></td></tr><tr><td>Full Length cDNA Clones</td><td></td><td></td><td>Can be obtained from any vendor that supplies open reading frame clones</td></tr><tr><td>Gel electrophoresis apparatus</td><td>Bio-Rad</td><td></td><td>any standard model</td></tr><tr><td>Glass Pasteur Pipets</td><td>Fisher Scientific</td><td>13-678-200</td><td></td></tr><tr><td>Globin Forward Primer for pIVT Construct</td><td></td><td></td><td>5&#039;- GAA GCT CAG AAT AAA CGC -3&#039;.&amp;nbsp; Can be purchased from any company that generates custom oligonucelotides</td></tr><tr><td>Globin Reverse Primer for pIVT Construct</td><td></td><td></td><td>5&#039;- ATT CGG GTG TTC TTG AGG CTG G -3&#039; Can be purchased from any company that generates custom oligonucelotides</td></tr><tr><td>Holding pipettes</td><td>Eppendorf</td><td>930001015</td><td>Vacutip</td></tr><tr><td>Humidified Chamber</td><td></td><td></td><td>Tupperware can be used</td></tr><tr><td>Illustra Ready-To-Go RT-PCR beads</td><td>GE Life Sciences</td><td>27925901</td><td></td></tr><tr><td>Incubator</td><td></td><td></td><td>any standard model with CO2 and water jacketed technology</td></tr><tr><td>Inverted Microscope</td><td>Nikon instruments</td><td></td><td>Any Standard model</td></tr><tr><td>Image J (NIH) Software</td><td>NIH</td><td></td><td>Image Analysis software</td></tr><tr><td>Lid of 96 well plate</td><td>Nalgene Nunc International</td><td>263339</td><td></td></tr><tr><td>Low Adhesion 0.5 mL microcentrifgue tube</td><td>USA Scientific</td><td>1405-2600</td><td></td></tr><tr><td>MacVector&amp;nbsp;</td><td>MacVector</td><td></td><td>Sequence analysis software</td></tr><tr><td>MG132</td><td>Selleckchem</td><td>S2619</td><td></td></tr><tr><td>Microscope slides</td><td>Fisher Scientific</td><td>12-544-3&amp;nbsp;</td><td></td></tr><tr><td>Millenium RNA Markers-Formaldehyde&amp;nbsp;</td><td>Ambion</td><td>AM7151</td><td></td></tr><tr><td>Milrinone</td><td>Sigma-Aldrich</td><td>M4659</td><td>Resuspend in DMSO at 2.5mM</td></tr><tr><td>Mineral Oil</td><td>Sigma-Aldrich</td><td>M5310</td><td>Only used embryo-tested, sterile-filtered</td></tr><tr><td>Monastrol</td><td>Sigma-Aldrich</td><td>M8515</td><td>Resuspend in DMSO at 100 mM</td></tr><tr><td>Mouthpiece</td><td>Biodiseno</td><td>MP-001-Y</td><td></td></tr><tr><td>N2 tank</td><td></td><td></td><td>for antivibration table</td></tr><tr><td>Nail Polish; Clear</td><td></td><td></td><td>Any clear nailpolish can be used</td></tr><tr><td>NanoDrop Microvolume UV-Vis Spectrophotometer</td><td>Thermo Scientific</td><td></td><td>any standard model</td></tr><tr><td>NorthernMax 10X Denaturing Gel Buffer</td><td>Life Technologies</td><td>AM8676</td><td></td></tr><tr><td>NorthernMax 10X Running buffer</td><td>Life Technologies</td><td>AM8671</td><td></td></tr><tr><td>NuPAGE MOPS SDS Running buffer</td><td>Thermo Scnentific</td><td>NP0001</td><td></td></tr><tr><td>Organ Culture Dish 60x15mm</td><td>Life Technologies</td><td>08-772-12</td><td></td></tr><tr><td>Paraformaldehyde</td><td>Polysciences, Inc.&amp;nbsp;</td><td>577773</td><td></td></tr><tr><td>PCR Thermal Cycler</td><td>Thermo Fisher Scientific</td><td>4484075</td><td></td></tr><tr><td>Petri Dish 139 mm</td><td>Thermo Fisher Scientifc</td><td>501V</td><td></td></tr><tr><td>Petri dish 35 mm</td><td>Thermo Fisher Scientifc</td><td>121V</td><td></td></tr><tr><td>Petri Dish 60 mm</td><td>Falcon BD</td><td>351007</td><td></td></tr><tr><td>Picoinjector</td><td>XenoWorks Digital Microinjector</td><td></td><td>any standard model</td></tr><tr><td>Pipette puller</td><td>Flaming-Brown Micropipette puller</td><td>Model P-1000</td><td></td></tr><tr><td>pIVT plasmid</td><td>AddGene</td><td>32374</td><td>Empty vector suitable for oocyte expression.</td></tr><tr><td>Pregnant Mare Serum Gonadotropin</td><td>Lee BioSolutions</td><td>493-10</td><td></td></tr><tr><td>QIAprep Spin Miniprep Kit</td><td>Qiagen</td><td>27104</td><td>purification of up to 20 uL of plasmid DNA</td></tr><tr><td>QIAquick PCR purification kit</td><td>Qiagen</td><td>28104</td><td></td></tr><tr><td>Quikchange II site directed mutagenesis kit</td><td>Agilent&amp;nbsp;</td><td>200523</td><td>mutagenesis kit for insertions and deletions</td></tr><tr><td>Quikchange lightning multi-site directed mutagenesis kit</td><td>Agilent&amp;nbsp;</td><td>210512</td><td>mutagenesis kit for single site changes</td></tr><tr><td>Scissors (Fine point)</td><td>Fine science tools</td><td>14393</td><td></td></tr><tr><td>Scissors (Medium point)</td><td>Fine science tools</td><td>WP114225</td><td></td></tr><tr><td>Seal-Rite 1.5 mL microcentrifuge tube</td><td>USA Scientific</td><td>1615-5500</td><td></td></tr><tr><td>Slide Warmer</td><td></td><td></td><td>any standard model</td></tr><tr><td>Spectrophotometer (Nanodrop)</td><td>Thermo Fisher Scientific</td><td>ND-ONE-W</td><td></td></tr><tr><td>Stereomicroscope</td><td></td><td></td><td>any standard model</td></tr><tr><td>Subcloning Efficiency DH5a Competent Cells</td><td>Thermo Fisher Scientifc</td><td>18265017</td><td></td></tr><tr><td>Syringe</td><td>BD Bioscienes</td><td>309623</td><td>1 ml, 27G(1/2)</td></tr><tr><td>T4 DNA Ligase</td><td>New England Biolabs</td><td>M0202L</td><td></td></tr><tr><td>T7 mMessage Machine high-yield capped RNA transcription kit</td><td>Life Technologies</td><td>AM1340</td><td></td></tr><tr><td>TritonX-100</td><td>Sigma-Aldrich</td><td>x-100</td><td></td></tr><tr><td>Tween-20</td><td>Sigma-Aldrich</td><td>274348</td><td></td></tr><tr><td>Tweezer (Fine point- Size 5)</td><td>Fine science tools</td><td>SN.743.12.1</td><td></td></tr><tr><td>UltraPure Dnase/Rnase-Free Distilled Water</td><td>Thermo Fisher Scientifc</td><td>10977015</td><td></td></tr><tr><td>UltraPure Ethidium Bromide 10mg/mL</td><td>Thermo Fisher Scientifc</td><td>15585011</td><td></td></tr><tr><td>UVP UV/White lite transilluminator</td><td>Fisher Scientific</td><td>UV95041501</td><td></td></tr><tr><td>Vectashield Mounting Medium</td><td>Vector Laboratories</td><td>H-1000</td><td></td></tr></tbody></table>

using mouse oocytes to assess human gene function during meiosis i

Embryonic aneuploidy is the major genetic cause of infertility in humans. Most of these events originate during female meiosis, and albeit positively correlated with maternal age, age alone is not always predictive of the risk of generating an aneuploid embryo. Therefore, gene variants might account for incorrect chromosome segregation during oogenesis. Given that access to human oocytes is limited for research purposes, a series of assays were developed to study human gene function during meiosis I using mouse oocytes. First, messenger RNA (mRNA) of the gene and gene variant of interest are microinjected into prophase I-arrested mouse oocytes. After allowing time for expression, oocytes are synchronously released into meiotic maturation to complete meiosis I. By tagging the mRNA with a sequence of a fluorescent reporter, such as green fluorescent protein (Gfp), the localization of the human protein can be assessed in addition to the phenotypic alterations. For example, gain or loss of function can be investigated by establishing experimental conditions that challenge the gene product to fix meiotic errors. Although this system is advantageous in investigating human protein function during oogenesis, adequate interpretation of results should be undertaken given that protein expression is not at endogenous levels and, unless controlled for (i.e. knocked out or down), murine homologs are also present in the system.

After in vitro transcription high quality RNA will have an A260/A280 ratio of (1.8-2.2) and an A260/A230 ratio &#8805;1.7 when measured using a spectrophotometer. The picture in Figure 1 shows the migration of in vitro-produced RNA on a denaturing agarose gel after electrophoresis. A band that is smeared in pattern or a sample that has multiple sized bands can indicate contamination or degradation of the sample. Alternatively, multiple bands...

Watch this Scientific Journal Video about Using Mouse Oocytes to Assess Human Gene Function During Meiosis I at JoVE.com

Using Mouse Oocytes to Assess Human Gene Function During Meiosis I

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.

Embryonic aneuploidy is the major genetic cause of infertility in humans. Most of these events originate during female meiosis, and albeit positively ...

using-mouse-oocytes-to-assess-human-gene-function-during-meiosis-i

Education

Research

JoVE Core

JoVE Journal

Cell Biology

Molecular Biology

Genetics

Unit 2

Unit 1

Meiosis

SCIENTISTS IN ACTION

8.8K Views.  IVI-RMA New Jersey. Als de genetische varianten die zijn gekoppeld aan ziekten bij de mens begint te worden blootgelegd, wordt het steeds belangrijker systemen waarmee snel evalueren de biologische betekenis van deze geïdentificeerde varianten te ontwikkelen. Dit protocol wordt beschreven methoden voor de evaluatie van menselijke genfunctie tijdens vrouwelijke meiose ik met behulp van de muis eicellen.

Video: Using Mouse Oocytes to Assess Human Gene Function During Meiosis I

RNA Interference-based Investigation of the Function of Heat Shock Protein 27 during Corneal Epithelial Wound Healing

Small interfering RNA (siRNA) is among the most widely used RNA interference methods for the short-term silencing of protein-coding genes. siRNA is a synthetic RNA duplex created to specifically target a mRNA transcript to induce its degradation and it has been used to identify novel pathways in various cellular processes. Few reports exist regarding the role of phosphorylated heat shock protein 27 (HSP27) in corneal epithelial wound healing. Herein, cultured human corneal epithelial cells were divided into a scrambled control-siRNA transfected group and a HSP27-specific siRNA-transfected group. Scratch-induced directional wounding assays, and western blotting, and flow cytometry were then performed. We conclude that HSP27 has roles in corneal epithelial wound healing that may involve epithelial cell apoptosis and migration. Here, step-by-step descriptions of sample preparation and the study protocol are provided.

Herein, we present a protocol to use heat shock protein 27 (HSP27)-specific small interfering RNA to assess the function of HSP27 during corneal epithelial wound healing. RNA interference is the best method for effectively knocking-down gene expression to investigate protein function in various cell types.

Small interfering RNA (siRNA) is among the most widely used RNA interference methods for the short-term silencing of protein-coding genes. siRNA is a ...

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

Chromatin spread techniques have been widely used to assess the dynamic localization of various proteins during gametogenesis, particularly for spermatogenesis. These techniques allow for visualization of protein and DNA localization patterns during meiotic events such as homologous chromosome pairing, synapsis and DNA repair. While a few protocols have been described in the literature, general chromatin spread techniques using mammalian prophase oocytes are limited and difficult due to the timing of meiosis initiation in fetal ovaries. In comparison, prophase spermatocytes can be collected from juvenile male mice with higher yields without the need for microdissection. However, it is difficult to obtain a pure synchronized population of cells at specific stages due to the heterogeneity of meiotic and post-meiotic germ cell populations in the juvenile and adult testis. For later stages of meiosis, it is advantageous to assess oocytes undergoing meiosis I (MI) or meiosis II (MII), because groups of mature oocytes can be collected from adult female mice and stimulated to resume meiosis in culture. Here, methods for meiotic chromatin spread preparations using oocytes dissected from fetal, neonatal and adult ovaries are described with accompanying video demonstrations. Chromosome missegregation events in mammalian oocytes are frequent, particularly during MI. These techniques can be used to assess and characterize the effects of different mutations or environmental exposures during various stages of oogenesis. As there are distinct differences between oogenesis and spermatogenesis, the techniques described within are invaluable to increase our understanding of mammalian oogenesis and the sexually dimorphic features of chromosome and protein dynamics during meiosis.

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 techniques have been widely used to assess the dynamic localization of various proteins during gametogenesis, particularly for ...

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

This protocol describes a simple and quick method to isolate and characterize mouse antral GV (Germinal Vesicle) oocytes as able (SN, Surrounded Nucleolus) or unable (NSN, Not Surrounded Nucleolus) to develop to the blastocyst stage after in vitro maturation (IVM) and in vitro fertilization (IVF). It makes use of Hoeschst33342 (or any other DNA intercalating dye) able to bind to the heterochromatin of the nucleolus showing a ring in the SN oocytes or not, like in the NSN oocytes. This represents the easiest and quickest way to sort both antral oocytes that can be eventually used for IVM or IVF procedures. 
Briefly, the protocol consists of the following steps: hormone injection to stimulate follicular growth; isolation of the oocytes at the GV stage from the antral compartment by puncturing the ovary with a sterile needle; preparation of thin glass pipettes for mouth pipetting of the oocytes; sorting of the oocytes with Hoechst33342 prepared at a supravital concentration; IVM, IVF or any other molecular/cellular analysis.
Unfortunately there are still few evidences to sort SN and NSN oocytes using less invasive techniques. If and once they will be identified, they could be potentially applied to human assisted reproductive technologies, although with several aspects that should be modified. To date, this technique has potential implications to dramatically increase IVM and IVF successful procedures in both endangered and species with economic interest.

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

This protocol describes a simple and quick method to isolate and characterize mouse antral GV (Germinal Vesicle) oocytes as able (SN, Surrounded ...

Developmental Biology

Evaluation of the Spindle Assembly Checkpoint Integrity in Mouse Oocytes

Aneuploidy is the leading genetic abnormality causing early miscarriage and pregnancy failure in humans. Most errors in chromosome segregation that give rise to aneuploidy occur during meiosis in oocytes, but why oocyte meiosis is error-prone is still not fully understood. During cell division, cells prevent errors in chromosome segregation by activating the spindle assembly checkpoint (SAC). This control mechanism relies on detecting kinetochore (KT)-microtubule (MT) attachments and sensing tension generated by spindle fibers. When KTs are unattached, the SAC is activated and prevents cell-cycle progression. The SAC is activated first by MPS1 kinase, which triggers the recruitment and formation of the mitotic checkpoint complex (MCC), composed of MAD1, MAD2, BUB3, and BUBR1. Then, the MCC diffuses into the cytoplasm and sequesters CDC20, an anaphase-promoting complex/cyclosome (APC/C) activator. Once KTs become attached to microtubules and chromosomes are aligned at the metaphase plate, the SAC is silenced, CDC20 is released, and the APC/C is activated, triggering the degradation of Cyclin B and Securin, thereby allowing anaphase onset. Compared to somatic cells, the SAC in oocytes is not as effective because cells can undergo anaphase despite having unattached KTs. Understanding why the SAC is more permissive and if this permissiveness is one of the causes of chromosome segregation errors in oocytes still needs further investigation. The present protocol describes the three techniques to comprehensively evaluate SAC integrity in mouse oocytes. These techniques include using nocodazole to depolymerize MTs to evaluate the SAC response, tracking SAC silencing by following the kinetics of Securin destruction, and evaluating the recruitment of MAD2 to KTs by immunofluorescence. Together these techniques probe mechanisms needed to produce healthy eggs by providing a complete evaluation of SAC integrity.

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.

Aneuploidy is the leading genetic abnormality causing early miscarriage and pregnancy failure in humans. Most errors in chromosome segregation that give ...

Identifying DNA Damage in Prophase-Arrested Oocytes of Mice

Detection of DNA Double-Stranded Breaks in Mouse Oocytes

Oocytes are amongst the biggest and most long-lived cells in the female body. They are formed in the ovaries during embryonic development and remain arrested at the prophase of meiosis I. The quiescent state may last for years until the oocytes receive a stimulus to grow and obtain the competency to resume meiosis. This protracted state of arrest makes them extremely susceptible to accumulating DNA-damaging insults, which affect the genetic integrity of the female gametes and, therefore, the genetic integrity of the future embryo. 
Consequently, the development of an accurate method to detect DNA damage, which is the first step for the establishment of DNA damage response mechanisms, is of vital importance. This paper describes a common protocol to test the presence and progress of DNA damage in prophase-arrested oocytes during a period of 20 h. Specifically, we dissect mouse ovaries, retrieve the cumulus-oocyte complexes (COCs), remove the cumulus cells from the COCs, and culture the oocytes in &#924;2 medium containing 3-isobutyl-1-methylxanthine to maintain the state of arrest. Thereafter, the oocytes are treated with the cytotoxic, antineoplasmic drug, etoposide, to engender double-strand breaks (DSBs). 
By using immunofluorescence and confocal microscopy, we detect and quantify the levels of the core protein &#947;H2AX, which is the phosphorylated form of the histone H2AX. H2AX becomes phosphorylated at the sites of DSBs after DNA damage. The inability to restore DNA integrity following DNA damage in oocytes can lead to infertility, birth defects, and increased rates of spontaneous abortions. Therefore, the understanding of DNA damage response mechanisms and, at the same time, the establishment of an intact method for studying these mechanisms are essential for reproductive biology research.

Author Spotlight: Understanding DNA Damage Response in Mammalian Oocytes and Preimplantation Embryos 

Maintaining oocyte genome integrity is necessary to ensure the genetic fidelity in the resulting embryo. Here, we present an accurate protocol for detecting DNA double-strand breaks in mammalian female germ cells.

Oocytes are amongst the biggest and most long-lived cells in the female body. They are formed in the ovaries during embryonic development and remain ...

Mouse Oocyte Microinjection, Maturation and Ploidy Assessment

Mistakes in chromosome segregation lead to aneuploid cells. In somatic cells, aneuploidy is associated with cancer but in gametes, aneuploidy leads to infertility, miscarriages or developmental disorders like Down syndrome. Haploid gametes form through species-specific developmental programs that are coupled to meiosis. The first meiotic division (MI) is unique to meiosis because sister chromatids remain attached while homologous chromosomes are segregated. For reasons not fully understood, this reductional division is prone to errors and is more commonly the source of aneuploidy than errors in meiosis II (MII) or than errors in male meiosis 1,2. 
In mammals, oocytes arrest at prophase of MI with a large, intact germinal vesicle (GV; nucleus) and only resume meiosis when they receive ovulatory cues. Once meiosis resumes, oocytes complete MI and undergo an asymmetric cell division, arresting again at metaphase of MII. Eggs will not complete MII until they are fertilized by sperm. Oocytes also can undergo meiotic maturation using established in vitro culture conditions 3. Because generation of transgenic and gene-targeted mouse mutants is costly and can take long periods of time, manipulation of female gametes in vitro is a more economical and time-saving strategy. 
Here, we describe methods to isolate prophase-arrested oocytes from mice and for microinjection. Any material of choice may be introduced into the oocyte, but because meiotically-competent oocytes are transcriptionally silent 4,5 cRNA, and not DNA, must be injected for ectopic expression studies. To assess ploidy, we describe our conditions for in vitro maturation of oocytes to MII eggs. Historically, chromosome-spreading techniques are used for counting chromosome number 6. This method is technically challenging and is limited to only identifying hyperploidies. Here, we describe a method to determine hypo-and hyperploidies using intact eggs 7-8. This method uses monastrol, a kinesin-5 inhibitor, that collapses the bipolar spindle into a monopolar spindle 9 thus separating chromosomes such that individual kinetochores can readily be detected and counted by using an anti-CREST autoimmune serum. Because this method is performed in intact eggs, chromosomes are not lost due to operator error.

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.

Mistakes in chromosome segregation lead to aneuploid cells.  In somatic cells, aneuploidy is associated with cancer but in gametes, aneuploidy leads to ...

Biology

Meiotic Spindle Assessment in Mouse Oocytes by siRNA-mediated Silencing

Errors in chromosome segregation during meiotic division in gametes can lead to aneuploidy that is subsequently transmitted to the embryo upon fertilization. The resulting aneuploidy in developing embryos is recognized as a major cause of pregnancy loss and congenital birth defects such as Down&#8217;s syndrome. Accurate chromosome segregation is critically dependent on the formation of the microtubule spindle apparatus, yet this process remains poorly understood in mammalian oocytes. Intriguingly, meiotic spindle assembly differs from mitosis and is regulated, at least in part, by unique microtubule organizing centers (MTOCs). Assessment of MTOC-associated proteins can provide valuable insight into the regulatory mechanisms that govern meiotic spindle formation and organization. Here, we describe methods to isolate mouse oocytes and deplete MTOC-associated proteins using a siRNA-mediated approach to test function. In addition, we describe oocyte fixation and immunofluorescence analysis conditions to evaluate meiotic spindle formation and organization.

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.

Errors in chromosome segregation during meiotic division in gametes can lead to aneuploidy that is subsequently transmitted to the embryo upon ...

Techniques for Imaging Prometaphase and Metaphase of Meiosis I in Fixed Drosophila Oocytes

Chromosome segregation in human oocytes is error prone, resulting in aneuploidy, which is the leading genetic cause of miscarriage and birth defects. The study of chromosome behavior in oocytes from model organisms holds much promise to uncover the molecular basis of the susceptibility of human oocytes to aneuploidy. Drosophila melanogaster is amenable to genetic manipulation, with over 100 years of research, community, and technique development. Visualizing chromosome behavior and spindle assembly in Drosophila oocytes has particular challenges, however, due primarily to the presence of membranes surrounding the oocyte that are impenetrable to antibodies. We describe here protocols for the collection, preparation, and imaging of meiosis I spindle assembly and chromosome behavior in Drosophila oocytes, which allow the molecular dissection of chromosome segregation in this important model organism.

Techniques for Imaging Prometaphase and Metaphase of Meiosis I in Fixed Drosophila Oocytes

We present protocols for the collection, preparation, and imaging of mature Drosophila oocytes. These methods allow the visualization of chromosome behavior and spindle assembly and function during meiosis.

Chromosome segregation in human oocytes is error prone, resulting in aneuploidy, which is the leading genetic cause of miscarriage and birth defects. The ...

Preparation of Meiotic Chromosome Spreads from Mouse Spermatocytes

Mammalian meiosis is a dynamic developmental process that occurs in germ cells and can be studied and characterized. Using a method to spread nuclei on the surface of slides (rather than dropping them from a height), we demonstrate an optimized technique on mouse spermatocytes that was first described in 1997. This method is widely used in laboratories to study mammalian meiosis because it yields a plethora of high quality nuclei undergoing substages of prophase I. Seminiferous tubules are first placed in a hypotonic solution to swell spermatocytes. Then spermatocytes are released into a sucrose solution to create a cell suspension, and nuclei are spread onto fixative-soaked glass slides. Following immunostaining, a diversity of proteins germane to meiotic processes can be examined. For example, proteins of the synaptonemal complex, a tripartite structure that connects the chromosome axes/cores of homologs together can be easily visualized. Meiotic recombination proteins, which are involved in repair of DNA double-strand breaks by homologous recombination, can also be immunostained to evaluate progression of prophase I. Here we describe and demonstrate in detail a technique widely used to study mammalian meiosis in spermatocytes from juvenile or adult male mice.

Meiosis is the developmental process by which gametes are formed through a single round of DNA replication and two successive rounds of chromosome segregation. Mammalian meiosis can be examined by utilizing a technique to prepare meiotic chromosome spreads. Here, we demonstrate a method of preparing surface-spread nuclei from mouse spermatocytes.

Mammalian meiosis is a dynamic developmental process that occurs in germ cells and can be studied and characterized. Using a method to spread nuclei on ...

Functional Assessment of Kinesin-7 CENP-E in Spermatocytes Using In Vivo Inhibition, Immunofluorescence and Flow Cytometry

In eukaryotes, meiosis is essential for genome stability and genetic diversity in sexual reproduction. Experimental analyses of spermatocytes in testes are critical for the investigations of spindle assembly and chromosome segregation in male meiotic division. The mouse spermatocyte is an ideal model for mechanistic studies of meiosis, however, the effective methods for the analyses of spermatocytes are lacking. In this article, a practical and efficient method for the in vivo inhibition of kinesin-7 CENP-E in mouse spermatocytes is reported. A detailed procedure for testicular injection of a specific inhibitor GSK923295 through abdominal surgery in 3-week-old mice is presented. Furthermore, described here is a series of protocols for tissue collection and fixation, hematoxylin-eosin staining, immunofluorescence, flow cytometry and transmission electron microscopy. Here we present an in vivo inhibition model via abdominal surgery and testicular injection, that could be a powerful technique to study male meiosis. We also demonstrate that CENP-E inhibition results in chromosome misalignment and metaphase arrest in primary spermatocytes during meiosis I. Our in vivo inhibition method will facilitate mechanistic studies of meiosis, serve as a useful method for genetic modifications of male germ lines, and shed a light on future clinical applications.

Functional Assessment of Kinesin-7 CENP-E in Spermatocytes Using In Vivo Inhibition, Immunofluorescence and Flow Cytometry

This article reports an in vivo inhibition of CENP-E through abdominal surgery and testicular injection of GSK923295, a valuable model for male meiotic division. Using the immunofluorescence, flow cytometry and transmission electron microscopy assays, we show that CENP-E inhibition results in chromosome misalignment and genome instability in mouse spermatocytes.

In eukaryotes, meiosis is essential for genome stability and genetic diversity in sexual reproduction. Experimental analyses of spermatocytes in testes ...

Using Mouse Oocytes to Assess Human Gene Function During Meiosis I

Samenvatting

Meer video's verkennen

Hoofdstukken in deze video