We thank Jessica Hall for her valuable discussion.

1. Preparation of Primary Insect Spermatocyte Cell Culture for Micromanipulation
<ol>
	<li>Slide preparation
	<ol>
		<li>Obtain a 75 mm x 25 mm glass slide with a 20 mm diameter circular hole cut out in the center of the slide. 
		NOTE: These were cut from a single sheet of window glass to be the size of a glass slide with a hole in the center.</li>
		<li>Run a 25 mm x 25 mm #1.5 coverslip through a Bunsen-burner flame for 2 s.</li>
		<li>Apply vacuum grease around the edge of the hole in the glass slide</li>
		<li>Place the coverslip on the hole as in Figure 1. Press it and make sure to form a tight seal.</li>
		<li>Flip the glass slide and fill the dissection well with halocarbon oil.</li>
	</ol>
	</li>
	<li>Spermatocyte culture preparation for viewing on microscope 
	NOTE: Here, we describe the culture preparation method using grasshopper or cricket cells. Testes contents of other arthropods can be cultured using a similar method.
	<ol>
		<li>Obtain subadult male crickets (or grasshoppers). Place a living insect in a refrigerator for approximately 2 min to cold-anesthetize it. Using dissecting scissors, quickly cut through the dorsal surface parallel to the long axis of the abdomen directly behind the wing buds. Manually squeeze the abdomen gently to push the testes through the cut in the exoskeleton (Figure 2).</li>
		<li>Using forceps, place the isolated testes in a dissection well containing halocarbon oil.</li>
		<li>If needed, view the testes under a dissecting microscope. Divide them into smaller pieces using fine-pointed forceps, removing any fat covering the testes, and use fine-pointed forceps to break up the testes (Figure 3A and 3B). Spread the testes contents under the oil, on the surface of the coverslip (Figure 3C).</li>
		<li>Spread the testes contents until the spread portion of the testis is barely noticeable to the eyes (Figure 3C). Use additional oil-loaded dissociation wells if needed.</li>
	</ol>
	</li>
</ol>
2. Micromanipulation
<ol>
	<li>Production of the microneedle
	<ol>
		<li>Place one end of a (0.85 mm in outer diameter, 0.65 mm in inner diameter) glass tube in the flame of a Bunsen burner. Pull the end of the glass tubing in such a way that a 150&#176; angle is formed, and an extended area of narrow glass tubing is created. Break the tubing in the thin region so that the thin region extending from the angle is approximately 10 mm long (Figure 4A).</li>
		<li>Using a microforge (either custom-made according to Powell27 or commercially available-see Table of Materials), touch the tip of the glass needle to the hot platinum wire to melt the glass at the tip. Form an approximately 45&#176; angle between the needle and the platinum wire of the microforge (Figure 4B). Pull the glass away from the hot wire, while shutting off the heat to the wire, forming a thin tip of &#8804;1.5 mm at the end of the glass needle. 
		NOTE: The tip diameter will be difficult to measure, but a tip of this length is likely to produce a firm but flexible needle that will be appropriate for micromanipulation. Alternatively, a micropipette puller could be used to create glass tubing with an appropriate tip diameter (the experimenter will have to test different pulling recipes to produce an appropriately firm but flexible microneedle for the job). The needle could be placed in a holder that is shaped similarly to the manipulation needle created according to the method described above.</li>
	</ol>
	</li>
	<li>Positioning the micromanipulator
	<ol>
		<li>Place the prepared slide on the stage of an inverted, phase-contrast microscope. Find the dividing cells and center them in the field of view. Focus on the cells using the lowest magnification possible. 
		NOTE: We used a 16X phase-contrast objective.</li>
		<li>Place the microneedle in the needle holder on the micromanipulator.</li>
		<li>Manually position the microneedle in the light path of the microscope so that the tip of the needle is illuminated by the light (Figure 5B).</li>
		<li>Focus the microscope several focal planes above the plane in which the cells lie.</li>
		<li>Reposition the microneedle using the joystick controller at a low sensitivity several times to find the shadow of the needle in the X- and Y-axes. Continue to readjust the position until the position of the tip is visible. Adjust the position of the needle along the Z-axis until the needle tip is in focus.</li>
		<li>Refocus on the cells, then focus the microscope above the cell plane so that cells are just out of focus and invisible. Readjust the position of the needle so that its tip is in focus in this focal plane.</li>
		<li>Adjust the magnification of the microscope as needed. 
		NOTE: We used a 100X 1.4 numerical aperture (NA) phase-contrast objective for the micromanipulation.</li>
		<li>After focusing on the cells using the higher-magnification objective, again focus the microscope above the cell plane so that the cells are just out of focus and invisible. Using a higher sensitivity setting, readjust the position of the needle so that its tip is in focus and centered in the focal plane above the plane in which the cells lie.</li>
		<li>Refocus on the cells, adjusting their position so they remain in the center of the field of view. The needle is now ready for the micromanipulation.</li>
	</ol>
	</li>
	<li>Micromanipulation of chromosomes
	<ol>
		<li>Using the same sensitivity setting as for the fine positioning at a high magnification, use the joystick to control the microneedle and push the chromosomes around inside the cell. Keep the needle tip above the plane of the cells.</li>
		<li>To pull on or move a chromosome, focus on a chromosome near the top of the cell. 
		NOTE: These chromosomes are easier to manipulate-manipulating chromosomes close to the coverslip makes it likely that the needle will grind into the coverslip, bursting the cell and ending the experiment.</li>
		<li>Adjust the Z-axis on the joystick to bring the needle tip into focus, and then move the needle tip with the joystick in X and Y. Place the tip of the needle directly on the chromosome to be manipulated and push it in the desired direction to allow the manipulator to reposition the chromosome.</li>
		<li>Depending on how far the chromosome is pushed, either apply tension to the chromosome or apply sufficient tension to detach a chromosome from the spindle. Once a chromosome is removed from a spindle, place it anywhere within the cell.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Chambers, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microdissection+studies+II.+The+cell+aster:+a+reversible+gelation+phenomenon.">Microdissection studies II. The cell aster: a reversible gelation phenomenon.</a> Journal of Experimental Zoology. 23 (3), 483-505 (1917).</li><li>Carlson, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microdissection+studies+of+the+dividing+neuroblast+of+the+grasshopper,+Chortophaga+viridifasciata.">Microdissection studies of the dividing neuroblast of the grasshopper, Chortophaga viridifasciata.</a> Chromosoma. 5 (3), 199-220 (1952).</li><li>Nicklas, R. B., Staehly, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosome+micromanipulation.+I.+The+mechanics+of+chromosome+attachment+to+the+spindle.">Chromosome micromanipulation. I. The mechanics of chromosome attachment to the spindle.</a> Chromosoma. 21 (1), 1-16 (1967).</li><li>Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosome+micromanipulation.+II.+Induced+reorientation+and+the+experimental+control+of+segregation+in+meiosis.">Chromosome micromanipulation. II. Induced reorientation and the experimental control of segregation in meiosis.</a> Chromosoma. 21 (1), 17-50 (1967).</li><li>Nicklas, R. B., Koch, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosome+micromanipulation.+3.+Spindle+fiber+tension+and+the+reorientation+of+mal-oriented+chromosomes.">Chromosome micromanipulation. 3. Spindle fiber tension and the reorientation of mal-oriented chromosomes.</a> Journal of Cell Biology. 43 (1), 40-50 (1969).</li><li>Nicklas, R. B., Ward, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elements+of+error+correction+in+mitosis:+microtubule+capture,+release,+and+tension.">Elements of error correction in mitosis: microtubule capture, release, and tension.</a> Journal of Cell Biology. 126 (5), 1241-1253 (1994).</li><li>Li, X., Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitotic+forces+control+a+cell-cycle+checkpoint.">Mitotic forces control a cell-cycle checkpoint.</a> Nature. 373 (6515), 630-632 (1995).</li><li>Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurements+of+the+force+produced+by+the+mitotic+spindle+in+anaphase.">Measurements of the force produced by the mitotic spindle in anaphase.</a> Journal of Cell Biology. 97 (2), 542-548 (1983).</li><li>Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+forces+that+move+chromosomes+in+mitosis.">The forces that move chromosomes in mitosis.</a> Annual Review of Biophysics and Biophysical Chemistry. 17, 431-449 (1988).</li><li>Nicklas, R. B., Koch, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosome+micromanipulation.+IV.+Polarized+motions+within+the+spindle+and+models+for+mitosis.">Chromosome micromanipulation. IV. Polarized motions within the spindle and models for mitosis.</a> Chromosoma. 39 (1), 1026 (1972).</li><li>Zhang, D., Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+impact+of+chromosomes+and+centrosomes+on+spindle+assembly+as+observed+in+living+cells.">The impact of chromosomes and centrosomes on spindle assembly as observed in living cells.</a> Journal of Cell Biology. 129 (5), 1287-1300 (1995).</li><li>Nicklas, R. B., Lee, G. M., Rieder, C. L., Rupp, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanically+cut+mitotic+spindles:+clean+cuts+and+stable+microtubules.">Mechanically cut mitotic spindles: clean cuts and stable microtubules.</a> Journal of Cell Science. 94 (Pt 3), 415-423 (1989).</li><li>Zhang, D., Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosomes+initiate+spindle+assembly+upon+experimental+dissolution+of+the+nuclear+envelope+in+grasshopper+spermatocytes.">Chromosomes initiate spindle assembly upon experimental dissolution of the nuclear envelope in grasshopper spermatocytes.</a> Journal of Cell Biology. 131 (5), 1125-1131 (1995).</li><li>Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosome+distribution:+experiments+on+cell+hybrids+and+in+vitro.">Chromosome distribution: experiments on cell hybrids and in vitro.</a> Philosophical Transactions of the Royal Society of London B. 227 (955), 267-276 (1977).</li><li>Paliulis, L. V., Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+reduction+of+chromosome+number+in+meiosis+is+determined+by+properties+built+into+the+chromosomes.">The reduction of chromosome number in meiosis is determined by properties built into the chromosomes.</a> Journal of Cell Biology. 150 (6), 1223-1232 (2000).</li><li>Church, K., Nicklas, R. B., Lin, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micromanipulated+bivalents+can+trigger+mini-spindle+formation+in+Drosophilamelanogaster+spermatocyte+cytoplasm.">Micromanipulated bivalents can trigger mini-spindle formation in Drosophilamelanogaster spermatocyte cytoplasm.</a> Journal of Cell Biology. 103 (6), 2765-2773 (1986).</li><li>Forer, A., Koch, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+autosome+movements+and+of+sex-chromosome+movements+on+sex-chromosome+segregation+in+crane+fly+spermatocytes.">Influence of autosome movements and of sex-chromosome movements on sex-chromosome segregation in crane fly spermatocytes.</a> Chromosoma. 40 (4), 417-442 (1973).</li><li>Camenzind, R., Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+non-random+chromosome+segregation+in+spermatocytes+of+Gryllotalpa+hexadactyla.+A+micromanipulation+analysis.">The non-random chromosome segregation in spermatocytes of Gryllotalpa hexadactyla. A micromanipulation analysis.</a> Chromosoma. 24 (3), 324-335 (1968).</li><li>Ault, J. G., Felt, K. D., Doan, R. N., Nedo, A. O., Ellison, C. A., Paliulis, L. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Co-segregation+of+sex+chromosomes+in+the+male+black+widow+spider+Latrodectus+mactans+(Araneae,+Theridiidae).">Co-segregation of sex chromosomes in the male black widow spider Latrodectus mactans (Araneae, Theridiidae).</a> Chromosoma. 126 (5), 645-654 (2017).</li><li>Felt, K. D., Lagerman, M. B., Ravida, N. A., Qian, L., Powers, S. R., Paliulis, L. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Segregation+of+the+amphitelically+attached+univalent+X+chromosome+in+the+spittlebug+Philaenus+spumarius.">Segregation of the amphitelically attached univalent X chromosome in the spittlebug Philaenus spumarius.</a> Protoplasma. 254 (6), 2263-2271 (2017).</li><li>Golding, A. E., Paliulis, L. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Karyotype,+sex+determination,+and+meiotic+chromosome+behavior+in+two+pholcid+(Araneomorphae,+Pholcidae)+spiders:+implications+for+karyotype+evolution.">Karyotype, sex determination, and meiotic chromosome behavior in two pholcid (Araneomorphae, Pholcidae) spiders: implications for karyotype evolution.</a> PLoS One. 6, e24748 (2011).</li><li>Doan, R. N., Paliulis, L. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micromanipulation+reveals+an+XO-XX+sex+determining+system+in+the+orb-weaving+spider+Neoscona+arabesca+(Walckenaer).">Micromanipulation reveals an XO-XX sex determining system in the orb-weaving spider Neoscona arabesca (Walckenaer).</a> Hereditas. 146 (4), 180-182 (2009).</li><li>Paliulis, L. V., Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micromanipulation+of+chromosomes+reveals+that+cohesion+release+during+cell+division+is+gradual+and+does+not+require+tension.">Micromanipulation of chromosomes reveals that cohesion release during cell division is gradual and does not require tension.</a> Current Biology. 14 (23), 2124-2129 (2004).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Biology Micromanipulator. DIY High Precision Micromanipulator. , (2018).</li><li>Ellis, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Piezoelectric+micromanipulators.">Piezoelectric micromanipulators.</a> Science. 138 (3537), 84-91 (1962).</li><li>Ellis, G. W., Begg, D. A., Zimmerman , . A. M., Forer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromosome+micromanipulation+studies.">Chromosome micromanipulation studies.</a> Mitosis/Cytokinesis. , 155-179 (1981).</li><li>Powell, E. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+microforge+attachment+for+the+biological+microscope.">A microforge attachment for the biological microscope.</a> Journal. Royal Microscopical Society. 72 (4), 214-217 (1953).</li><li>Alsop, G. B., Zhang, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microtubules+continuously+dictate+distribution+of+actin+filaments+and+positioning+of+cell+cleavage+in+grasshopper+spermatocytes.">Microtubules continuously dictate distribution of actin filaments and positioning of cell cleavage in grasshopper spermatocytes.</a> Journal of Cell Science. 117 (Pt 8), 1591-1602 (2004).</li><li>Zhang, D., Nicklas, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anaphase'+and+cytokinesis+in+the+absence+of+chromosomes.">Anaphase' and cytokinesis in the absence of chromosomes.</a> Nature. 382, 466-468 (1996).</li></ol>

The authors have nothing to disclose.

With practice, moving chromosomes around in the cell can become second nature. Needles that are both sufficiently stiff and sufficiently thin-tipped are difficult to &#34;get the knack of&#34; fabricating, but this ability also comes with practice. Needles that are so fine that they deform when moved in the halocarbon oil will not be useful for pushing chromosomes in the cell. Needles that are so blunt that their tips are visible and as large as 1/3 of the width of a chromosome (or larger) are very likely to kill the cel...

Micromanipulation has revealed parts of the mechanism for a chromosome congression, the spindle checkpoint, and anaphase chromosome movements. The earliest publication describing the results of micromanipulation experiments was by Robert Chambers1. Chambers used a mechanical micromanipulator with an attached glass needle to probe the cytoplasm of a number of different cell types. Unfortunately, contrast methods that allowed the visualization of chromosomes and many other cellular components in living cells were not available at the time, so Chambers&#39; experiments could not show the effects of repositioning such cellular components. Early micromanipulations that altered the chromosome position used the Chambers apparatus to sweep the spindle midzone in anaphase cells, showing that such manipulations could alter the position of chromosome arms in anaphase grasshopper neuroblasts2. Nicklas and his collaborators were the first to perform fine micromanipulations of chromosomes, stretching the chromosomes3, detaching them from the spindle and inducing a reorientation3,4, stabilizing a malorientation by applying tension to the chromosomes5,6,7, and measuring the forces produced by spindles in anaphase8,9. Other work by the Nicklas lab showed that cytoplasmic granules could also be manipulated10 and that centrosomes could be repositioned by micromanipulation11. Micromanipulation is not just useful for moving chromosomes and other cellular components. A micromanipulation needle can cleanly cut through a mitotic spindle in demembranated cells12 or can be used to dissolve the nuclear envelope13. In addition, adjacent cells can be fused by micromanipulation14,15.
With such a wide variety of interesting experiments that can be done using micromanipulation, it is at first glance surprising that micromanipulation experiments have been done by very few chromosome biologists. One reason for this deficiency is that the mitotically-dividing cultured cells that are derived from vertebrate tissues and are commonly used for studying chromosome movements are extremely difficult to micromanipulate. These tissue culture cells generally have a cortical cytoskeleton that &#34;gets in the way&#34; of the micromanipulation needle, and chromosomes either cannot be reached by the needle or the needle grinds through the cell, leading to a cell rupture and death. We, and other experimenters who use micromanipulation, have found arthropod cells to be amenable to micromanipulation. Arthropod spermatocytes are easily spread under a layer of halocarbon oil and appear to have a much less robust cortical cytoskeleton underlying the cell membrane during a cell division. Thus, arthropod testes provide a good source of meiotically-dividing cells (spermatocytes) and mitotically-dividing cells (spermatogonia) with easily accessible chromosomes for micromanipulation. A serial sectioning of a grasshopper spermatocyte fixed during a manipulation revealed that the needle never penetrates the cell membrane; the cell membrane deforms around the needle (Nicklas R.B., personal communication). Spermatocytes from a number of insect and spider taxa have been micromanipulated successfully, including grasshoppers, praying mantids, fruit flies, crane flies, crickets, spittlebugs, moths, black widow spiders, cellar spiders, and orb-weaving spiders3,7,17,18,19,20,21,22. Cultured, mitotically-dividing cells from insects can be micromanipulated. For example, the chromosomes in grasshopper neuroblasts in a primary culture have chromosomes that can be readily micromanipulated2,23. We suspect that the available cultured lines derived from Drosophila and other insects will also be micromanipulatable, though we have not tested the technique with these cells. We will show how dividing cells from grasshoppers and crickets can be prepared for a micromanipulation. Crickets are easy to obtain from most pet stores at any time of the year. Grasshoppers are only easily obtainable in the summer unless the researcher has access to a laboratory colony, but the species used (Melanoplus sanguinipes) has easily flattened cells, and long, easy-to-manipulate chromosomes.
Another reason why micromanipulation experiments have been done by a small handful of biologists is that micromanipulators that move chromosomes well are rarely available in the marketplace. We have found that a joystick-controlled piezoelectric micromanipulator controls the needle movement with no vibration, drift, or lag between the joystick movement and the needle movement, but other types of manipulators can also successfully push chromosomes around in the cell. The micromanipulators designed by Ellis and Begg25,26 are ideal for the micromanipulation of chromosomes, though they use older technology. Piezoelectric micromanipulators are currently available and commonly used in electrophysiology; however, these micromanipulators are not typically joystick-controlled. Joystick control is key to the smooth movements required for a successful micromanipulation, and so a custom joystick should be constructed to make the currently-available piezoelectric micromanipulators work for a chromosome micromanipulation. The joystick-controlled piezoelectric micromanipulators that work best have direct position control, in which the movement of the joystick translates directly to a needle movement.
A newly-designed piezoelectric micromanipulator can be constructed from commercially-available parts that can be easily replaced and from some small 3-D printed components, and it works well for chromosome micromanipulation24. The micromanipulator has adjustable sensitivity, manual coarse positioning, and no vibration, drift, or lag in the needle movement, and direct position control of the needle. Scientists can construct the micromanipulator using instructions available online24. Below are the methods for preparing a primary spermatocyte cell culture and for micromanipulating the chromosomes within the cells in that culture.

<table><tbody><tr><td>VWR micro cover glass</td><td>VWR</td><td>48366 249</td><td>25 mm x 25 mm, no 1.5</td></tr><tr><td>Dow Corning High Vacuum Grease</td><td>VWR</td><td>AA44224-KT</td><td></td></tr><tr><td>KEL-F Oil #10</td><td>Ohio Valley Specialty Chemical</td><td>10189</td><td></td></tr><tr><td>Microdissecting Scissors, Stainless Steel</td><td>Sigma-Aldrich</td><td>S3271-1EA</td><td></td></tr><tr><td>Dumont #5 fine foreceps</td><td>Fine Science Tools</td><td>11254-20</td><td></td></tr><tr><td>0.85 mm outer diameter, 0.65 mm inner diameter Pyrex glass tube&amp;nbsp;</td><td>Drummond Scientific</td><td>Custom order--call to request</td><td></td></tr><tr><td>Inverted, Phase contrast microscope with 10X or 16X low magnification objective and 60X or 100X high magnification objective</td><td>Any brand</td><td></td><td></td></tr><tr><td>microforge</td><td>either custom built or Narashige</td><td>MF-900</td><td></td></tr><tr><td>micromanipulator</td><td>either custom built or Burleigh PCS-6000 with custom piezo-controlling joystick</td><td>PCS-6300</td><td></td></tr></tbody></table>

micromanipulation of chromosomes in insect spermatocytes

The micromanipulation of chromosomes has been an essential method for illuminating the mechanism for chromosome congression, the spindle checkpoint, and anaphase chromosome movements, and has been key to understanding what controls chromosome movements during a cell division. A skilled biologist can use a micromanipulator to detach chromosomes from the spindle, to reposition chromosomes within the cell, and to apply forces to chromosomes using a small glass needle with a very fine tip. While perturbations can be made to chromosomes using other methods such as optical trapping and other uses of a laser, to date, no other method allows the repositioning of cellular components on the scale of tens to hundreds of microns with little to no damage to the cell.
The selection and preparation of appropriate cells for the micromanipulation of chromosomes, specifically describing the preparation of grasshopper and cricket spermatocyte primary cultures for the use in live-cell imaging and micromanipulation, are described here. In addition, we show the construction of a needle to be used for moving chromosomes within the cell, and the use of a joystick-controlled piezoelectric micromanipulator with a glass needle attached to it to reposition chromosomes within dividing cells. A sample result shows the use of a micromanipulator to detach a chromosome from a spindle in a primary spermatocyte and to reposition that chromosome within the cell.

Figure 6 shows a sample micromanipulation of 2 adjacent grasshopper primary spermatocytes in several examples of the possible uses of micromanipulation. This experiment was done using an inverted, phase-contrast microscope. The 0:00 (times shown are in min:s) image shows both cells prior to the manipulation. One chromosome in the bottom cell is shown under tension applied by the micromanipulation needle (0:05; black arrow) and then completely detached from th...

Watch this Scientific Journal Video about Micromanipulation of Chromosomes in Insect Spermatocytes at JoVE.com

Micromanipulation of Chromosomes in Insect Spermatocytes

In this protocol, we describe the selection and preparation of appropriate cells for micromanipulation and the use of a piezoelectric micromanipulator to reposition chromosomes within those cells.

The micromanipulation of chromosomes has been an essential method for illuminating the mechanism for chromosome congression, the spindle checkpoint, and ...

micromanipulation-of-chromosomes-in-insect-spermatocytes

Research

JoVE Journal

Developmental Biology

8.5K Views.  Bucknell University. In this protocol, we describe the selection and preparation of appropriate cells for micromanipulation and the use of a piezoelectric micromanipulator to reposition chromosomes within those cells.

Video: Micromanipulation of Chromosomes in Insect Spermatocytes

Preparation of Meiotic Chromosome Spreads from Zebrafish Spermatocytes

Meiosis is the key cellular process required to create haploid gametes for sexual reproduction. Model organisms have been instrumental in understanding the chromosome events that take place during meiotic prophase, including the pairing, synapsis, and recombination events that ensure proper chromosome segregation. While the mouse has been an important model for understanding the molecular mechanisms underlying these processes, not all meiotic events in this system are analogous to human meiosis. We recently demonstrated the exciting potential of the zebrafish as a model of human spermatogenesis. Here we describe, in detail, our methods to visualize meiotic chromosomes and associated proteins in chromosome spread preparations. These preparations have the advantage of allowing high resolution analysis of chromosome structures. First, we describe the procedure for dissecting testes from adult zebrafish, followed by cell dissociation, lysis, and spreading of the chromosomes. Next, we describe the procedure for detecting the localization of meiotic chromosome proteins, by immunofluorescence detection, and nucleic acid sequences, by fluorescence in situ hybridization (FISH). These techniques comprise a useful set of tools for the cytological analysis of meiotic chromatin architecture in the zebrafish system. Researchers in the zebrafish community should be able to quickly master these techniques and incorporate them into their standard analyses of reproductive function.

Nuclear surface spreads are an indispensable tool for studying chromosome events during meiosis. Here we demonstrate a method to prepare and visualize meiotic chromosomes during prophase I from zebrafish spermatocytes.

Meiosis is the key cellular process required to create haploid gametes for sexual reproduction. Model organisms have been instrumental in understanding ...

Genetics

A Seminiferous Tubule Squash Technique for the Cytological Analysis of Spermatogenesis Using the Mouse Model

Meiotic progression in males is a process that requires the concerted action of a number of highly regulated cellular events. Errors occurring during meiosis can lead to infertility, pregnancy loss or genetic defects. Commencing at the onset of puberty and continuing throughout adulthood, continuous semi-synchronous waves of spermatocytes undergo spermatogenesis and ultimately form haploid sperm. The first wave of mouse spermatocytes undergoing meiotic initiation appear at day 10 post-partum (10 dpp) and are released into the lumen of seminiferous tubules as mature sperm at 35 dpp. Therefore, it is advantageous to utilize mice within this developmental time-window in order to obtain highly enriched populations of interest. Analysis of rare cell stages is more difficult in older mice due to the contribution of successive spermatogenic waves, which increase the diversity of the cellular populations within the tubules. The method described here is an easily implemented technique for the cytological evaluation of the cells found within the seminiferous tubules of mice, including spermatogonia, spermatocytes, and spermatids. The tubule squash technique maintains the integrity of isolated male germ cells and allows examination of cellular structures that are not easily visualized with other techniques. To demonstrate the possible applications of this tubule squash technique, spindle assembly was monitored in spermatocytes progressing through the prophase to metaphase I transition (G2/MI transition). In addition, centrosome duplication, meiotic sex chromosome inactivation (MSCI), and chromosome bouquet formation were assessed as examples of the cytological structures that can be observed using this tubule squash method. This technique can be used to pinpoint specific defects during spermatogenesis that are caused by mutation or exogenous perturbation, and thus, contributes to our molecular understanding of spermatogenesis.

The goal of this tubule squash technique is to rapidly assess cytological features of developing mouse spermatocytes while preserving cellular integrity. This method allows for the study of all stages of spermatogenesis, and can be easily implemented alongside other biochemical and molecular biological approaches for the study of mouse meiosis.

Meiotic progression in males is a process that requires the concerted action of a number of highly regulated cellular events. Errors occurring during ...

2D and 3D Chromosome Painting in Malaria Mosquitoes

Fluorescent in situ hybridization (FISH) of whole arm chromosome probes is a robust technique for mapping genomic regions of interest, detecting chromosomal rearrangements, and studying three-dimensional (3D) organization of chromosomes in the cell nucleus. The advent of laser capture microdissection (LCM) and whole genome amplification (WGA) allows obtaining large quantities of DNA from single cells. The increased sensitivity of WGA kits prompted us to develop chromosome paints and to use them for exploring chromosome organization and evolution in non-model organisms. Here, we present a simple method for isolating and amplifying the euchromatic segments of single polytene chromosome arms from ovarian nurse cells of the African malaria mosquito Anopheles gambiae. This procedure provides an efficient platform for obtaining chromosome paints, while reducing the overall risk of introducing foreign DNA to the sample. The use of WGA allows for several rounds of re-amplification, resulting in high quantities of DNA that can be utilized for multiple experiments, including 2D and 3D FISH. We demonstrated that the developed chromosome paints can be successfully used to establish the correspondence between euchromatic portions of polytene and mitotic chromosome arms in An. gambiae. Overall, the union of LCM and single-chromosome WGA provides an efficient tool for creating significant amounts of target DNA for future cytogenetic and genomic studies.

Chromosome painting is a useful method for studying organization of the cell nucleus and evolution of the karyotype. Here, we demonstrate an approach to isolate and amplify specific regions of interest from single polytene chromosomes that are subsequently used for two- and three-dimensional fluorescent in situ hybridization (FISH).

Fluorescent in situ hybridization (FISH) of whole arm chromosome probes is a robust technique for mapping genomic regions of interest, detecting ...

Immunology and Infection

Microinjection Techniques for Studying Mitosis in the Drosophila melanogaster Syncytial Embryo

This protocol describes the use of the Drosophila melanogaster syncytial embryo for studying mitosis1. Drosophila has useful genetics with a sequenced genome, and it can be easily maintained and manipulated. Many mitotic mutants exist, and transgenic flies expressing functional fluorescently (e.g. GFP) - tagged mitotic proteins have been and are being generated. Targeted gene expression is possible using the GAL4/UAS system2. 

The Drosophila early embryo carries out multiple mitoses very rapidly (cell cycle duration, &asymp;10 min). It is well suited for imaging mitosis, because during cycles 10-13, nuclei divide rapidly and synchronously without intervening cytokinesis at the surface of the embryo in a single monolayer just underneath the cortex. These rapidly dividing nuclei probably use the same mitotic machinery as other cells, but they are optimized for speed; the checkpoint is generally believed to not be stringent, allowing the study of mitotic proteins whose absence would cause cell cycle arrest in cells with a strong checkpoint. Embryos expressing GFP labeled proteins or microinjected with fluorescently labeled proteins can be easily imaged to follow live dynamics (Fig. 1). In addition, embryos can be microinjected with function-blocking antibodies or inhibitors of specific proteins to study the effect of the loss or perturbation of their function3. These reagents can diffuse throughout the embryo, reaching many spindles to produce a gradient of concentration of inhibitor, which in turn results in a gradient of defects comparable to an allelic series of mutants. Ideally, if the target protein is fluorescently labeled, the gradient of inhibition can be directly visualized4. It is assumed that the strongest phenotype is comparable to the null phenotype, although it is hard to formally exclude the possibility that the antibodies may have dominant effects in rare instances, so rigorous controls and cautious interpretation must be applied. Further away from the injection site, protein function is only partially lost allowing other functions of the target protein to become evident.

Microinjection Techniques for Studying Mitosis in the Drosophila melanogaster Syncytial Embryo

This protocol describes the use of microinjection and high resolution imaging in the Drosophila melanogaster syncytial embryo to study mitosis.

This protocol describes the use of the Drosophila melanogaster syncytial embryo  for studying mitosis1.  Drosophila has useful genetics with a sequenced ...

Biology

Isolation of Murine Spermatogenic Cells using a Violet-Excited Cell-Permeable DNA Binding Dye

Isolation of meiotic spermatocytes is essential to investigate molecular mechanisms underlying meiosis and spermatogenesis. Although there are established cell isolation protocols using Hoechst 33342 staining in combination with fluorescence-activated cell sorting, it requires cell sorters equipped with an ultraviolet laser. Here we describe a cell isolation protocol using the DyeCycle Violet (DCV) stain, a low cytotoxicity DNA binding dye structurally similar to Hoechst 33342. DCV can be excited by both ultraviolet and violet lasers, which improves the flexibility of equipment choice, including a cell sorter not equipped with an ultraviolet laser. Using this protocol, one can isolate three live-cell subpopulations in meiotic prophase I, including leptotene/zygotene, pachytene, and diplotene spermatocytes, as well as post-meiotic round spermatids. We also describe a protocol to prepare single-cell suspension from mouse testes. Overall, the procedure requires a short time to complete (4-5 hours depending on the number of needed cells), which facilitates many downstream applications.

Here we present a simple and efficient method to isolate live meiotic and post-meiotic germ cells from adult mouse testes. Using a low-cytotoxicity, violet-excited DNA binding dye and fluorescence-activated cell sorting, one can isolate highly enriched spermatogenic cell populations for many downstream applications.

Isolation of meiotic spermatocytes is essential to investigate molecular mechanisms underlying meiosis and spermatogenesis. Although there are established ...

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 ...

Microinjection of Corn Planthopper, Peregrinus maidis, Embryos for CRISPR/Cas9 Genome Editing

The corn planthopper, Peregrinus maidis, is&#160;a pest of maize and a vector of several maize viruses. Previously published methods describe the triggering of RNA interference (RNAi) in P. maidis through microinjection of double-stranded RNAs (dsRNAs) into nymphs and adults. Despite the power of RNAi, phenotypes generated via this technique are transient and lack long-term Mendelian inheritance. Therefore, the P. maidis toolbox needs to be expanded to include functional genomic tools that would enable the production of stable mutant strains, opening the door for researchers to bring new control methods to bear on this economically important pest. However, unlike the dsRNAs used for RNAi, the components used in CRISPR/Cas9-based genome editing and germline transformation do not easily cross cell membranes. As a result, plasmid DNAs, RNAs, and/or proteins must be microinjected into embryos before the embryo cellularizes, making the timing of injection a critical factor for success. To that end, an agarose-based egg-lay method was developed to allow embryos to be harvested from P. maidis females at relatively short intervals. Herein are provided detailed protocols for collecting and microinjecting precellular P. maidis embryos with CRISPR components (Cas9 nuclease that has been complexed with guide RNAs), and results of Cas9-based gene knockout of a P. maidis eye-color gene, white, are presented. Although these protocols describe CRISPR/Cas9-genome editing in P. maidis, they can also be used for producing transgenic P. maidis via germline transformation by simply changing the composition of the injection solution.

Microinjection of Corn Planthopper, Peregrinus maidis, Embryos for CRISPR/Cas9 Genome Editing

Herein are protocols for collecting and microinjecting precellular corn planthopper embryos for the purpose of modifying their genome via CRISPR/Cas9-based genome editing or for the addition of marked transposable elements through germline transformation.

The corn planthopper, Peregrinus maidis, is&#160;a pest of maize and a vector of several maize viruses. Previously published methods describe the ...

Bioengineering

Cytological Analysis of Spermatogenesis: Live and Fixed Preparations of Drosophila Testes

Drosophila melanogaster is a powerful model system that has been widely used to elucidate a variety of biological processes. For example, studies of both the female and male germ lines of Drosophila have contributed greatly to the current understanding of meiosis as well as stem cell biology. Excellent protocols are available in the literature for the isolation and imaging of Drosophila ovaries&#160;and testes3-12. Herein, methods for the dissection and preparation of Drosophila testes for microscopic analysis are described with an accompanying video demonstration. A protocol for isolating testes from the abdomen of adult males and preparing slides of live tissue for analysis by phase-contrast microscopy as well as a protocol for fixing and immunostaining testes for analysis by fluorescence microscopy are presented. These techniques can be applied in the characterization of Drosophila mutants that exhibit defects in spermatogenesis as well as in the visualization of subcellular localizations of proteins.

Cytological Analysis of Spermatogenesis: Live and Fixed Preparations of Drosophila Testes

Methods for isolating and preparing Drosophila testes samples (live and fixed) for imaging by phase-contrast and fluorescence microscopy are described herein.&#160;

Drosophila melanogaster is a powerful model system that has been widely used to elucidate a variety of biological processes. For example, studies of both ...

Fluorescence In Situ Hybridization to Study Mosquito Spermatogenesis

Whole-Mount Fluorescence In Situ Hybridization to Study Spermatogenesis in the Anopheles Mosquito

Spermatogenesis is a complex biological process during which diploid cells undergo successive mitotic and meiotic division followed by large structural changes to form haploid spermatozoa. Besides the biological aspect, studying spermatogenesis is of paramount importance for understanding and developing genetic technologies such as gene drive and synthetic sex ratio distorters, which, by altering Mendelian inheritance and the sperm sex ratio, respectively, could be used to control pest insect populations. These technologies have proven to be very promising in lab settings and could potentially be used to control wild populations of Anopheles mosquitoes, which are vectors of malaria. Due to the simplicity of the testis anatomy and their medical importance, Anopheles gambiae, a major malaria vector in sub-Saharan Africa, represents a good cytological model for studying spermatogenesis. This protocol describes how whole-mount fluorescence in situ hybridization (WFISH) can be used to study the dramatic changes in cell nuclear structure through spermatogenesis using fluorescent probes that specifically stain the X and Y chromosomes. FISH usually requires the disruption of the reproductive organs to expose mitotic or meiotic chromosomes and allow the staining of specific genomic regions with fluorescent probes. WFISH enables the preservation of the native cytological structure of the testis, coupled with a good level of signal detection from fluorescent probes targeting repetitive DNA sequences. This allows researchers to follow changes in the chromosomal behavior of cells undergoing meiosis along the structure of the organ, where each phase of the process can clearly be distinguished. This technique could be particularly useful for studying chromosome meiotic pairing and investigating the cytological phenotypes associated with, for example, synthetic sex ratio distorters, hybrid male sterility, and the knock-out of genes involved in spermatogenesis.

Author Spotlight: Whole-Mount Fluorescence In Situ Hybridization to Study Spermatogenesis in the Anopheles Mosquito  

Given their simple anatomy, Anopheles testes offer a good cytological model for studying spermatogenesis. This protocol describes whole-mount fluorescence in situ hybridization, a technique used to investigate this biological process, as well as the phenotype of transgenic strains harboring mutations in the genes involved in sperm production.

Spermatogenesis is a complex biological process during which diploid cells undergo successive mitotic and meiotic division followed by large structural ...

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 ...

Micromanipulation of Chromosomes in Insect Spermatocytes

Summary

Explore More Videos

Chapters in this video

Preparation of Meiotic Chromosome Spreads from Zebrafish Spermatocytes

A Seminiferous Tubule Squash Technique for the Cytological Analysis of Spermatogenesis Using the Mouse Model

2D and 3D Chromosome Painting in Malaria Mosquitoes

Microinjection Techniques for Studying Mitosis in the Drosophila melanogaster Syncytial Embryo

Isolation of Murine Spermatogenic Cells using a Violet-Excited Cell-Permeable DNA Binding Dye

Mouse Oocyte Microinjection, Maturation and Ploidy Assessment

Microinjection of Corn Planthopper, Peregrinus maidis, Embryos for CRISPR/Cas9 Genome Editing

Cytological Analysis of Spermatogenesis: Live and Fixed Preparations of Drosophila Testes

Whole-Mount Fluorescence In Situ Hybridization to Study Spermatogenesis in the Anopheles Mosquito

Preparation of Meiotic Chromosome Spreads from Mouse Spermatocytes