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 border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">VWR micro cover glass</td>
			<td style="width:71px;">VWR</td>
			<td style="width:119px;">48366 249</td>
			<td style="width:167px;">25x25 mm, no 1.5</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Dow Corning High Vacuum Grease</td>
			<td style="width:71px;">VWR</td>
			<td>AA44224-KT</td>
			<td></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">KEL-F Oil #10</td>
			<td style="width:71px;">Ohio Valley Specialty Chemical</td>
			<td align="right" style="width:119px;">10189</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Microdissecting Scissors, Stainless Steel</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td>S3271-1EA</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Dumont #5 fine foreceps</td>
			<td style="width:71px;">Fine Science Tools</td>
			<td>11254-20</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;">0.85 mm outer diameter, 0.65 mm inner diameter Pyrex glass tube&#160;</td>
			<td style="width:71px;">Drummond Scientific</td>
			<td style="width:119px;">Custom order--call to request</td>
			<td></td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:216px;">Inverted, Phase contrast microscope with 10X or 16X low magnification objective and 60X or 100X high magnification objective</td>
			<td style="width:71px;">Any brand</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:216px;">microforge</td>
			<td style="width:71px;">either custom built or Narashige</td>
			<td style="width:119px;">MF-900</td>
			<td></td>
		</tr>
		<tr height="210">
			<td height="210" style="height:210px;width:216px;">micromanipulator</td>
			<td style="width:71px;">either custom built or Burleigh PCS-6000 with custom piezo-controlling joystick</td>
			<td style="width:119px;">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

An Optogenetic Approach for Assessing Formation of Neuronal Connections in a Co-culture System

Here we describe a protocol to generate a co-culture consisting of 2 different neuronal populations. Induced pluripotent stem cells (iPSCs) are reprogrammed from human fibroblasts using episomal vectors. Colonies of iPSCs can be observed 30 days after initiation of fibroblast reprogramming. Pluripotent colonies are manually picked and grown in neural induction medium to permit differentiation into neural progenitor cells (NPCs). iPSCs rapidly convert into neuroepithelial cells within 1 week and retain the capability to self-renew when maintained at a high culture density. Primary mouse NPCs are differentiated into astrocytes by exposure to a serum-containing medium for 7 days and form a monolayer upon which embryonic day 18 (E18) rat cortical neurons (transfected with channelrhodopsin-2 (ChR2)) are added. Human NPCs tagged with the fluorescent protein, tandem dimer Tomato (tdTomato), are then seeded onto the astrocyte/cortical neuron culture the following day and allowed to differentiate for 28 to 35 days. We demonstrate that this system forms synaptic connections between iPSC-derived neurons and cortical neurons, evident from an increase in the frequency of synaptic currents upon photostimulation of the cortical neurons. This co-culture system provides a novel platform for evaluating the ability of iPSC-derived neurons to create synaptic connections with other neuronal populations.

A protocol to generate a co-culture system consisting of neurons derived from induced pluripotent stem cells (iPSCs), primary cortical neurons and astrocytes is described. This co-culture system allows detection of the formation of synaptic contacts and circuits between new, iPSC-derived neurons and pre-existing cortical neurons expressing channelrhodopsin-2.

Here we describe a protocol to generate a co-culture consisting of 2 different neuronal populations. Induced pluripotent stem cells (iPSCs) are ...

Analysis of Zebrafish Larvae Skeletal Muscle Integrity with Evans Blue Dye

The zebrafish model is an emerging system for the study of neuromuscular disorders. In the study of neuromuscular diseases, the integrity of the muscle membrane is a critical disease determinant. To date, numerous neuromuscular conditions display degenerating muscle fibers with abnormal membrane integrity; this is most commonly observed in muscular dystrophies. Evans Blue Dye (EBD) is a vital, cell permeable dye that is rapidly taken into degenerating, damaged, or apoptotic cells; in contrast, it is not taken up by cells with an intact membrane. EBD injection is commonly employed to ascertain muscle integrity in mouse models of neuromuscular diseases. However, such EBD experiments require muscle dissection and/or sectioning prior to analysis. In contrast, EBD uptake in zebrafish is visualized in live, intact preparations. Here, we demonstrate a simple and straightforward methodology for performing EBD injections and analysis in live zebrafish. In addition, we demonstrate a co-injection strategy to increase efficacy of EBD analysis. Overall, this video article provides an outline to perform EBD injection and characterization in zebrafish models of neuromuscular disease.

In this study, we describe a straightforward method to perform Evans Blue Dye (EBD) analysis on zebrafish larvae. This technique is a powerful tool for the characterization of skeletal muscle integrity and delineation of zebrafish models of muscular dystrophy, and is a valuable method for the development of novel therapeutics.

The zebrafish model is an emerging system for the study of neuromuscular disorders.  In the study of neuromuscular diseases, the integrity of the muscle ...

Technique to Target Microinjection to the Developing Xenopus Kidney

The embryonic kidney of Xenopus&#160;laevis (frog), the pronephros, consists of a single nephron, and can be used as a model for kidney disease. Xenopus embryos are large, develop externally, and can be easily manipulated by microinjection or surgical procedures. In addition, fate maps have been established for early Xenopus embryos. Targeted microinjection into the individual blastomere that will eventually give rise to an organ or tissue of interest can be used to selectively overexpress or knock down gene expression within this restricted region, decreasing secondary effects in the rest of the developing embryo. In this protocol, we describe how to utilize established Xenopus fate maps to target the developing Xenopus kidney (the pronephros), through microinjection into specific blastomere of 4- and 8-cell embryos. Injection of lineage tracers allows verification of the specific targeting of the injection. After embryos have developed to stage 38 - 40, whole-mount immunostaining is used to visualize pronephric development, and the contribution by targeted cells to the pronephros can be assessed. The same technique can be adapted to target other tissue types in addition to the pronephros.

Technique to Target Microinjection to the Developing Xenopus Kidney

Here, we present a protocol to use fate maps and lineage tracers to target injections into individual blastomeres that give rise to the kidney of Xenopus laevis embryos.

The embryonic kidney of Xenopus&#160;laevis (frog), the pronephros, consists of a single nephron, and can be used as a model for kidney disease. Xenopus ...

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

The evolutionarily conserved&#160;extracellular signal transducing RTK-RAS-ERK pathway is an important kinase-signaling cascade that controls multiple cellular and developmental processes principally via activation of ERK, the terminal kinase of the pathway. Tight regulation of ERK activity is essential for normal development and homeostasis; overly active ERK results in excessive cellular proliferation, while underactive ERK causes cell death. C. elegans is a powerful model system that has helped characterize the function and regulation of RTK-RAS-ERK signaling pathway during development. In particular, the RTK-RAS-ERK pathway is essential for C. elegans germline development, which is the focus of this method. Using antibodies specific to the active, diphosphorylated form of ERK (dpERK), the stereotypical localization pattern can be visualized within the germline. Because this pattern is both spatially and temporally controlled, the ability to reproducibly assay dpERK is useful to identify regulators of the pathway that affect dpERK signal duration and amplitude and thus germline development. Here we demonstrate how to successfully dissect, stain, and image dpERK within the C. elegans gonad. This method can be adapted for spatial localization of any signaling or structural protein in the C. elegans gonad, provided an antibody compatible with immunofluorescence is available.

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

We present an immunofluorescence&#160;imaging-based method for spatial and temporal localization of active ERK in the dissected C. elegans gonad. The protocol described here can be adapted for visualization of any signaling or structural protein in the C. elegans gonad, provided a suitable antibody reagent is available.

The evolutionarily conserved&#160;extracellular signal transducing RTK-RAS-ERK pathway is an important kinase-signaling cascade that controls multiple ...

Directed Differentiation of Primitive and Definitive Hematopoietic Progenitors from Human Pluripotent Stem Cells

One of the major goals for regenerative medicine is the generation and maintenance of hematopoietic stem cells (HSCs) derived from human pluripotent stem cells (hPSCs). Until recently, efforts to differentiate hPSCs into HSCs have predominantly generated hematopoietic progenitors that lack HSC potential, and instead resemble yolk sac hematopoiesis.&#160;These resulting hematopoietic progenitors may have limited utility for in vitro disease modeling of various adult hematopoietic disorders, particularly those of the lymphoid lineages. However, we have recently described methods to generate erythro-myelo-lymphoid multilineage definitive hematopoietic progenitors from hPSCs using a stage-specific directed differentiation protocol, which we outline here. Through enzymatic dissociation of hPSCs on basement membrane matrix-coated plasticware, embryoid bodies (EBs) are formed. EBs are differentiated to mesoderm by recombinant BMP4, which is subsequently specified to the definitive hematopoietic program by the GSK3&#946; inhibitor, CHIR99021. Alternatively, primitive hematopoiesis is specified by the PORCN inhibitor, IWP2. Hematopoiesis is further driven through the addition of recombinant VEGF and supportive hematopoietic cytokines. The resulting hematopoietic progenitors generated using this method have the potential to be used for disease and developmental modeling, in vitro.

Here, we present human pluripotent stem cell (hPSC) culture protocols, used to differentiate hPSCs into CD34+ hematopoietic progenitors. This method uses stage-specific manipulation of canonical WNT signaling to specify cells exclusively to either the definitive or primitive hematopoietic program.

One of the major goals for regenerative medicine is the generation and maintenance of hematopoietic stem cells (HSCs) derived from human pluripotent stem ...

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the proteins involved in these pathways are evolutionarily conserved between mammals and other eukaryotes, such as the fruit fly Drosophila melanogaster, suggesting that similar organizing principles exist during the development of these organisms. Importantly, Drosophila has been used extensively to identify cellular and molecular mechanisms regulating processes that are required in mammals including neurogenesis, differentiation, axonal guidance, and synaptogenesis. Flies have also been used successfully to model a variety of human neurodevelopmental diseases. Here we describe a protocol for the step-by-step microdissection, fixation, and immunofluorescent localization of proteins within the adult Drosophila brain. This protocol focuses on two example neuronal populations, mushroom body neurons and retinal photoreceptors, and includes optional steps to trace individual mushroom body neurons using Mosaic Analysis with a Repressible Cell Marker (MARCM) technique. Example data from both wild-type and mutant brains are shown along with a brief description of a scoring criteria for axonal guidance defects. While this protocol highlights two well-established antibodies for investigating the morphology of mushroom body and photoreceptor neurons, other Drosophila brain regions and the localization of proteins within other brain regions can also be investigated using this protocol.

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

This protocol describes the dissection and immunostaining of adult Drosophila melanogaster brain tissues. Specifically, this protocol highlights the use of Drosophila mushroom body and photoreceptor neurons as example neuronal subsets that can be accurately used to uncover general principles underlying many aspects of neuronal development.

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the ...

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

Studying the cell biological processes during converting the identities of specific cell types provides important insights into mechanism that maintain and protect cellular identities. The conversion of germ cells into specific neurons in the nematode Caenorhabditis elegans (C. elegans) is a powerful tool for performing genetic screens in order to dissect regulatory pathways that safeguard established cell identities. Reprogramming of germ cells to a specific type of neurons termed ASE requires transgenic animals that allow broad over-expression of the Zn-finger transcription factor (TF) CHE-1. Endogenous CHE-1 is expressed exclusively in two head neurons and is required to specify the glutamatergic ASE neurons fate, which can easily be visualized by the gcy-5prom::gfp reporter. A trans gene containing the heat-shock promoter-driven che-1 gene expression construct allows broad mis-expression of CHE-1 in the entire animal upon heat-shock treatment. The combination of RNAi against the chromatin-regulating factor LIN-53 and heat-shock-induced che-1 over-expression leads to reprogramming of germ cell into ASE neuron-like cells. We describe here the specific RNAi procedure and appropriate conditions for heat-shock treatment of transgenic animals in order to successfully induce germ cell to neuron conversion.

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

This protocol describes how to study cellular processes during cell fate conversion in Caenorhabditis elegans in vivo. Using transgenic animals, allowing heat-shock promoter-driven overexpression of the neuron fate-inducing transcription factor CHE-1 and RNAi-mediated depletion of the chromatin-regulating factor LIN-53 germ cell to neuron reprogramming can be observed in vivo.

Studying the cell biological processes during converting the identities of specific cell types provides important insights into mechanism that maintain ...

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

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

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

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

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

Visualizing the Node and Notochordal Plate In Gastrulating Mouse Embryos Using Scanning Electron Microscopy and Whole Mount Immunofluorescence

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is the formation of the transient organizers, the node and notochordal plate, from cells that have passed through the primitive streak. The proper formation of these signaling centers is essential for the development of the body plan and techniques to visualize them are of high interest to mouse developmental biologists. The node and notochordal plate lie on the ventral surface of gastrulating mouse embryos around embryonic day (E) 7.5 of development. The node is a cup-shaped structure whose cells possess a single slender cilium each. The proper subcellular localization and rotation of the cilia in the node pit determines left-right asymmetry. The notochordal plate cells also possess single cilia albeit shorter than those of the node cells. The notochordal plate forms the notochord which acts as an important signaling organizer for somitogenesis and neural patterning. Because the cells of the node and notochordal plate are transiently present on the surface and possess cilia, they can be visualized using scanning electron microscopy (SEM). Among other techniques used to visualize these structures at the cellular level is whole mount immunofluorescence (WMIF) using the antibodies against the proteins that are highly expressed in the node and notochordal plate. In this report, we describe our optimized protocols to perform SEM and WMIF of the node and notochordal plate in developing mouse embryos to help in the assessment of tissue shape and cellular organization in wild-type and gastrulation mutant embryos.

The node and notochordal plate are transient signaling organizers in developing mouse embryos that can be visualized using several techniques. Here, we describe in detail how to perform two of the techniques to study their structure and morphogenesis: 1) scanning electron microscopy (SEM); and 2) whole mount immunofluorescence (WMIF).

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is ...

Controlled Cortical Impact Model of Mouse Brain Injury with Therapeutic Transplantation of Human Induced Pluripotent Stem Cell-Derived Neural Cells

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality worldwide. Disease pathology due to TBI progresses from the primary mechanical insult to secondary injury processes, including apoptosis and inflammation. Animal modeling has been valuable in the search to unravel injury mechanisms and evaluate potential neuroprotective therapies. This protocol describes the controlled cortical impact (CCI) model of focal, open-head TBI. Specifically, parameters for producing a mild unilateral cortical injury are described. Behavioral consequences of CCI are analyzed using the adhesive tape removal test of bilateral sensorimotor integration. Regarding experimental therapy for TBI pathology, this protocol also illustrates a process for transplanting cultured cells into the brain. Neural cell cultures derived from human induced pluripotent stem cells (hiPSCs) were chosen for their potential to show superior functional restoration in human TBI patients. Chronic survival of hiPSCs in the host mouse brain tissue is detected using a modified DAB immunohistochemical process.

This protocol demonstrates methodologies for a mouse model of open-skull traumatic brain injury and transplantation of cultured human induced pluripotent stem cell-derived cells into the injury site. Behavioral and histologic tests of outcomes from these procedures are also described in brief.

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality worldwide. Disease pathology due to TBI progresses from the primary mechanical ...