The authors wish to thank Dr. Leonid Volkov and &#201;ric Bouchard for their technical advice regarding epifluorescence microscopy.
Financial support 
Funded by the Canadian Institutes of Health Research (grant #MOP-93781) to G.B.

Animal care was in accordance with the Universit&#233; de Sherbrooke animal care and use committee.

1. Tube Preparation
<ol>
	<li>The day before cell sorting, add 1-2 ml of heat-inactivated fetal bovine serum (FBS) to 5 ml polypropylene round bottom tubes, and to 15 ml and 50 ml polypropylene conical tubes. 
	Critical step: Ensure that every tube used in the protocol is coated. 
	Note: FBS coating prevents germ cells from sticking to tube walls.</li>
	<li>Slowly mix O/N by ...

<ol>
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X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+actin+and+myosin+during+spermatogenesis.">The role of actin and myosin during spermatogenesis.</a> Mol. Biol. Rep. 38 (6), 3993-4001 (2011).</li><li>Cheng, C. Y., Mruk, D. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+junction+dynamics+in+the+testis:+Sertoli-germ+cell+interactions+and+male+contraceptive+development.">Cell junction dynamics in the testis: Sertoli-germ cell interactions and male contraceptive development.</a> Physiol. Rev. 82, 825-874 (2002).</li><li>Laiho, A., Kotaja, N., Gyenesei, A., Sironen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptome+profiling+of+the+murine+testis+during+the+first+wave+of+spermatogenesis.">Transcriptome profiling of the murine testis during the first wave of spermatogenesis.</a> PLoS ONE. 8 (4), (2013).</li><li>Leduc, F., Maquennehan, V., Nkoma, G. B., Boissonneault, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+damage+response+during+chromatin+remodeling+in+elongating+spermatids+of+mice.">DNA damage response during chromatin remodeling in elongating spermatids of mice.</a> Biol. Reprod. 78 (2), 324-332 (2008).</li><li>Meistrich, M. L., Mohapatra, B., Shirley, C. R., Zhao, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Roles+of+transition+nuclear+proteins+in+spermiogenesis.">Roles of transition nuclear proteins in spermiogenesis.</a> Chromosoma. 111 (8), 483-488 (2003).</li><li>Gr&#233;goire, M. -. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Male-driven+de+novo+mutations+in+haploid+germ+cells.">Male-driven de novo mutations in haploid germ cells.</a> Mol. Hum. Reprod. 19 (8), 495-499 (2013).</li><li>Simard, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Instability+of+trinucleotidic+repeats+during+chromatin+remodeling+in+spermatids.">Instability of trinucleotidic repeats during chromatin remodeling in spermatids.</a> Hum. Mutat. , (2014).</li><li>Wykes, S. M., Krawetz, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+spermatogenic+cells+from+adult+transgenic+mouse+testes+using+unit-gravity+sedimentation.">Separation of spermatogenic cells from adult transgenic mouse testes using unit-gravity sedimentation.</a> Mol. Biotechnol. 25 (2), 131-138 (2003).</li><li>Yoshida, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+first+round+of+mouse+spermatogenesis+is+a+distinctive+program+that+lacks+the+self-renewing+spermatogonia+stage.">The first round of mouse spermatogenesis is a distinctive program that lacks the self-renewing spermatogonia stage.</a> Development (Cambridge, England). 133 (8), 1495-1505 (2006).</li><li>Moreno, R. D., Lizama, C., Urz&#250;a, N., Vergara, S. P., Reyes, 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=Caspase+activation+throughout+the+first+wave+of+spermatogenesis+in+the+rat.">Caspase activation throughout the first wave of spermatogenesis in the rat.</a> Cell Tissue Res. 325 (3), 533-540 (2006).</li><li>Meistrich, M. L., Trostle-Weige, P. K., Van Beek, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+specific+stages+of+spermatids+from+vitamin+A-synchronized+rat+testes+for+assessment+of+nucleoprotein+changes+during+spermiogenesis.">Separation of specific stages of spermatids from vitamin A-synchronized rat testes for assessment of nucleoprotein changes during spermiogenesis.</a> Biol. Reprod. 51 (2), 334-344 (1994).</li><li>van Pelt, A. M., de Rooij, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synchronization+of+the+seminiferous+epithelium+after+vitamin+A+replacement+in+vitamin+A-deficient+mice.">Synchronization of the seminiferous epithelium after vitamin A replacement in vitamin A-deficient mice.</a> Biol. Reprod. 43, 363-367 (1990).</li><li>Getun, I. V., Torres, B., Bois, P. R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+cytometry+purification+of+mouse+meiotic+cells.">Flow cytometry purification of mouse meiotic cells.</a> J. Vis. Exp. , (2011).</li><li>Kovtun, I. V., McMurray, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trinucleotide+expansion+in+haploid+germ+cells+by+gap+repair.">Trinucleotide expansion in haploid germ cells by gap repair.</a> Nature Genet. 27 (4), 407-411 (2001).</li><li>Bastos, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+cytometric+characterization+of+viable+meiotic+and+postmeiotic+cells+by+Hoechst+33342+in+mouse+spermatogenesis.">Flow cytometric characterization of viable meiotic and postmeiotic cells by Hoechst 33342 in mouse spermatogenesis.</a> Cytometry A. 65 (1), 40-49 (2005).</li><li>Lassalle, B., Ziyyat, A., Testart, J., Finaz, C., Lef&#232;vre, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+cytometric+method+to+isolate+round+spermatids+from+mouse+testis.">Flow cytometric method to isolate round spermatids from mouse testis.</a> Hum. Reprod. 14 (2), 388-394 (1999).</li></ol>

The authors declare no competing financial interests.

Spermatogenic cells have always been challenging to study given the complexity of the seminiferous epithelium, as well as the limited success of in vitro culture. Over the years, many approaches to purify germ cells from various species were developed. Sedimentation techniques using gravity purification with Percoll or bovine serum albumin gradients usually provide a good yield of intact germinal cells, but lack proper definition between some cell types such as meiotic tetraploid cells and spermatids10</sup...

Haploid round spermatids differentiate into spermatozoa by a process called spermiogenesis. This involves many different steps including the acquisition of a flagellum, chromatin and cytoskeleton remodeling, condensation of the nucleus as well as the loss of most of the cytoplasm. These unique cellular events must be finely regulated in order to produce a mature functional gamete with an intact genome suitable for fertilization. Spermiogenesis can hardly be studied in vitro since no reliable cell culture system has so far been able to support progression through the different steps of the process. Moreover, actual in vitro techniques lead to a poor yield1,2. In vivo, proper transitions through the different steps of spermiogenesis are crucial for the natural functional integrity of the male gamete. Successful purification of spermatids according to their differentiation steps has never been accomplished with a level of enrichment sufficient to allow molecular characterization of spermiogenesis. For instance, purification of key steps of the spermatidal differentiation would be especially useful to study the developing acrosome, formation of the midpiece3, cell junction dynamics4, RNA dynamics5, chromatin remodeling process6,7 or genomic stability8. Purification of spermatids has been hampered by their progressive morphological transformation, the lack of known stage-specific external biomarkers, and their peculiar shape and size. 
Although most male germ cells display a direct relationship between DNA staining and ploidy (DNA content), we noticed that such positive correlation is no longer applicable to spermatids. This stems from our early observation that seminiferous tubule sections show variable intensity of DNA staining throughout the different spermiogenesis steps. Although DNA staining is consistent with their haploid set of chromosomes from spermiogenesis steps 1 to 7 (round spermatids), we observed a sharp increase in fluorescence intensity with DAPI or SYTO 16 around the onset of nuclear reorganization and chromatin remodeling (spermiogenesis step 8) reaching a peak at the onset of nuclear condensation (spermiogenesis steps 11-12). Following condensation of the nucleus, DNA staining intensity decreases until spermiation (spermiogenesis step 16). We surmised that this was likely associated with the formation of their peculiar chromatin structure transition where histones are replaced by protamines. We therefore developed a reliable flow cytometry method that allows the separation of spermatids using the variation of DNA intensity of spermatids as a main selection parameter.
A simple flow cytometry approach is described to separate mouse spermatids with high purity (95-100%) based on their apparent DNA content (SYTO16 staining), size and granulosity. Spermatids are separated into four populations; spermiogenesis steps 1-9, 10-12, 13-14 and 15-16. Purified spermatids are suitable for genetic/genomic analysis, as well as proteomic applications as described in a recent publication from our group9.

<table border="0" cellpadding="0" cellspacing="0" width="565">
	<tbody>
		<tr height="41">
			<td height="41" style="height:41px;width:135px;">Isoflurane</td>
			<td style="width:119px;">ABBOT</td>
			<td style="width:129px;">05260-05</td>
			<td style="width:184px;">For mouse anesthesia before euthanasia</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:135px;">Fetal bovine serum</td>
			<td style="width:119px;">Wisent</td>
			<td style="width:129px;">90150</td>
			<td style="width:184px;">For tube coating</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:135px;">1X PBS</td>
			<td style="width:119px;"></td>
			<td style="width:129px;"></td>
			<td style="width:184px;"></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:135px;">EDTA</td>
			<td style="width:119px;">BioShop</td>
			<td style="width:129px;">EDT</td>
			<td style="width:184px;">For sorting buffer preparation</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:135px;">HEPES</td>
			<td style="width:119px;">Sigma</td>
			<td style="width:129px;">H</td>
			<td style="width:184px;">For sorting buffer preparation</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:135px;">100 % Ethanol</td>
			<td style="width:119px;">Les alcools de commerce</td>
			<td style="width:129px;">092-09-11N</td>
			<td style="width:184px;">For cell fixation</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:135px;">SYTO 16</td>
			<td style="width:119px;">Life Technologies</td>
			<td style="width:129px;">S7578</td>
			<td style="width:184px;">DNA staining</td>
		</tr>
		<tr height="81">
			<td height="81" style="height:81px;width:135px;">5 ml polypropylene round bottom tubes</td>
			<td style="width:119px;">BD Falcon</td>
			<td style="width:129px;">352063</td>
			<td style="width:184px;">Sorted cells collection</td>
		</tr>
		<tr height="81">
			<td height="81" style="height:81px;width:135px;">15 ml polypropylene conical bottom tubes</td>
			<td style="width:119px;">PROgene</td>
			<td style="width:129px;">1500</td>
			<td style="width:184px;"></td>
		</tr>
		<tr height="81">
			<td height="81" style="height:81px;width:135px;">50 ml polypropylene conical bottom tubes</td>
			<td style="width:119px;">PROgene</td>
			<td style="width:129px;">5000</td>
			<td style="width:184px;"></td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:135px;">TEC4 anaesthetic vaporizer</td>
			<td style="width:119px;">Ohmeda</td>
			<td style="width:129px;">1160526</td>
			<td style="width:184px;">For mouse euthanasia</td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:135px;">CO2 gas tank</td>
			<td style="width:119px;">Praxair</td>
			<td style="width:129px;">C799117902</td>
			<td style="width:184px;">For mouse euthanasia</td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:135px;">O2 gas tank</td>
			<td style="width:119px;">Praxair</td>
			<td style="width:129px;">O254130501</td>
			<td style="width:184px;">For mouse euthanasia</td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:135px;">Homemade mouse gas chamber</td>
			<td style="width:119px;"></td>
			<td style="width:129px;"></td>
			<td style="width:184px;">For mouse euthanasia</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:135px;">40 &#181;m Falcon cell strainer</td>
			<td style="width:119px;">Corning Incorporated</td>
			<td style="width:129px;">352340</td>
			<td style="width:184px;"></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:135px;">50-micron sample line filters</td>
			<td style="width:119px;">BD Biosciences</td>
			<td style="width:129px;">649049</td>
			<td style="width:184px;"></td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:135px;">Vortex mixer</td>
			<td style="width:119px;">Labnet international, inc.</td>
			<td style="width:129px;">S0200</td>
			<td style="width:184px;">For cell fixation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:135px;">Dynac centrifuge</td>
			<td style="width:119px;">Clay Adams</td>
			<td style="width:129px;">101</td>
			<td style="width:184px;"></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:135px;">Celltrics 50 &#181;m filters</td>
			<td style="width:119px;">Partec</td>
			<td style="width:129px;">04-004-2327</td>
			<td style="width:184px;"></td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:135px;">488 nm laser-euipped cell sorter</td>
			<td style="width:119px;">BD Biosciences</td>
			<td style="width:129px;">FACSAria III</td>
			<td style="width:184px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:135px;">Accudop Fluorescent Beads</td>
			<td style="width:119px;">BD Biosciences</td>
			<td style="width:129px;">345249</td>
			<td style="width:184px;"></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:135px;">Sorting Buffer: 1X PBS, 1mM EDTA pH 8.0, 25mM HEPES pH 7.0, 1%FBS</td>
			<td></td>
			<td></td>
			<td style="width:184px;">FBS is heat-inactivated. Make fresh solution, 0.22 &#956;m filtered and keep at 4&#176;C.</td>
		</tr>
	</tbody>
</table>

step-specific sorting of mouse spermatids by flow cytometry

The differentiation of mouse spermatids is one critical process for the production of a functional male gamete with an intact genome to be transmitted to the next generation. So far, molecular studies of this morphological transition have been hampered by the lack of a method allowing adequate separation of these important steps of spermatid differentiation for subsequent analyses. Earlier attempts at proper gating of these cells using flow cytometry may have been difficult because of a peculiar increase in DNA fluorescence in spermatids undergoing chromatin remodeling. Based on this observation, we provide details of a simple flow cytometry scheme, allowing reproducible purification of four populations of mouse spermatids fixed with ethanol, each representing a different state in the nuclear remodeling process. Population enrichment is confirmed using step-specific markers and morphological criterions. The purified spermatids can be used for genomic and proteomic analyses.

Gating strategy used with flow cytometry
Figure 1 represents the gating strategy used in flow cytometry to sort four highly pure spermatid populations. Briefly, cells with positive DNA staining (Alexa Fluor 488-A) are first selected with Gate 1. Spermatids from spermiogenesis steps 1-12 are selected (Gate 2) on a dot plot showing the granulosity (SSC-A) vs size (FSC-A) from Gate 1. Then, spermatids from spermiog...

Watch this Scientific Journal Video about Step-specific Sorting of Mouse Spermatids by Flow Cytometry at JoVE.com

Step-specific Sorting of Mouse Spermatids by Flow Cytometry

We describe a sorting strategy for mouse spermatids using flow cytometry. Spermatids are sorted into four highly pure populations, including round (spermiogenesis steps 1-9), early elongating (spermiogenesis steps 10-12), late elongating (spermiogenesis steps 13-14) and elongated spermatids (spermiogenesis steps 15-16). DNA staining, size and granulosity are used as selection parameters.

The differentiation of mouse spermatids is one critical process for the production of a functional male gamete with an intact genome to be transmitted to ...

step-specific-sorting-of-mouse-spermatids-by-flow-cytometry

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Developmental Biology

10.4K Görüntüleme.  Université de Sherbrooke. We describe a sorting strategy for mouse spermatids using flow cytometry. Spermatids are sorted into four highly pure populations, including round (spermiogenesis steps 1-9), early elongating (spermiogenesis steps 10-12), late elongating (spermiogenesis steps 13-14) and elongated spermatids (spermiogenesis steps 15-16). DNA staining, size and granulosity are used as selection parameters.