שלב מסוים מיון של Spermatids העכבר על ידי cytometry הזרימה
Summary
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.
Abstract
הבידול של spermatids העכבר הוא תהליך קריטי אחד לייצור תא מין זכרי פונקציונלי עם הגנום שלם כדי להיות מועבר לדור הבא. עד כה, מחקרים מולקולריים של מעבר מורפולוגיים זה כבר הקשו על ידי חוסר שיטה המאפשרת הפרדה נאותה של צעדים החשובים אלה של בידול spermatid לניתוחים שלאחר מכן. הניסיונות קודמים בgating התקין של תאים אלה באמצעות cytometry זרימה ייתכן שהיו קשים בגלל עלייה מוזרה בקרינת ה- DNA בspermatids עובר שיפוץ הכרומטין. המבוססים על התבוננות זו, אנו מספקים פרטים של זרימה פשוטה cytometry תכנית, המאפשרים טיהור שחזור של ארבע אוכלוסיות של spermatids עכבר קבוע עם אתנול, המייצג כל מדינה אחרת בתהליך שיפוץ הגרעיני. העשרת אוכלוסייה אישרה באמצעות סמני צעד ספציפי וקריטריונים מורפולוגיים. Spermatids המטוהר יכול לשמש להגנומי וproteomIC ניתוחים.
Introduction
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.
Protocol
Representative Results
Discussion
תאי זרע ראשוניים תמיד היו מאתגרים ללמוד בהתחשב במורכבות של אפיתל seminiferous, כמו גם ההצלחה המוגבלת של תרבות במבחנה. במהלך השנים, גישות רבות כדי לטהר תאי נבט ממינים שונים פותחו. טכניקות שקיעה באמצעות טיהור הכבידה עם Percoll או הדרגתיים אלבומין בסרום שור בדרך כלל מספקות ת…
Disclosures
The authors have nothing to disclose.
Acknowledgements
המחברים מבקשים להודות לד"ר לאוניד וולקוב ואריק Bouchard לייעוץ הטכני שלהם בנוגע למיקרוסקופיה epifluorescence.
תמיכה כלכלית
ממומן על ידי המכון הקנדי לבריאות מחקר (מענק # MOP-93,781) לGB
Materials
| Isoflurane | ABBOT | 05260-05 | For mouse anesthesia before euthanasia |
| Fetal bovine serum | Wisent | 90150 | For tube coating |
| 1X PBS | |||
| EDTA | BioShop | EDT | For sorting buffer preparation |
| HEPES | Sigma | H | For sorting buffer preparation |
| 100 % Ethanol | Les alcools de commerce | 092-09-11N | For cell fixation |
| SYTO 16 | Life Technologies | S7578 | DNA staining |
| 5 ml polypropylene round bottom tubes | BD Falcon | 352063 | Sorted cells collection |
| 15 ml polypropylene conical bottom tubes | PROgene | 1500 | |
| 50 ml polypropylene conical bottom tubes | PROgene | 5000 | |
| TEC4 anaesthetic vaporizer | Ohmeda | 1160526 | For mouse euthanasia |
| CO2 gas tank | Praxair | C799117902 | For mouse euthanasia |
| O2 gas tank | Praxair | O254130501 | For mouse euthanasia |
| Homemade mouse gas chamber | For mouse euthanasia | ||
| 40 µm Falcon cell strainer | Corning Incorporated | 352340 | |
| 50-micron sample line filters | BD Biosciences | 649049 | |
| Vortex mixer | Labnet international, inc. | S0200 | For cell fixation |
| Dynac centrifuge | Clay Adams | 101 | |
| Celltrics 50 µm filters | Partec | 04-004-2327 | |
| 488 nm laser-euipped cell sorter | BD Biosciences | FACSAria III | |
| Accudop Fluorescent Beads | BD Biosciences | 345249 | |
| Sorting Buffer: 1X PBS, 1mM EDTA pH 8.0, 25mM HEPES pH 7.0, 1%FBS | FBS is heat-inactivated. Make fresh solution, 0.22 μm filtered and keep at 4°C. |
References
- Sato, T., et al. In vitro production of functional sperm in cultured neonatal mouse testes. Nature. 471 (7339), 504-507 (2011).
- Sato, T., et al. In vitro production of fertile sperm from murine spermatogonial stem cell lines. Nat. Commun. 2, 472 (2011).
- Sun, X., Kovacs, T., Hu, Y. -. J., Yang, W. -. X. The role of actin and myosin during spermatogenesis. Mol. Biol. Rep. 38 (6), 3993-4001 (2011).
- Cheng, C. Y., Mruk, D. D. Cell junction dynamics in the testis: Sertoli-germ cell interactions and male contraceptive development. Physiol. Rev. 82, 825-874 (2002).
- Laiho, A., Kotaja, N., Gyenesei, A., Sironen, A. Transcriptome profiling of the murine testis during the first wave of spermatogenesis. PLoS ONE. 8 (4), (2013).
- Leduc, F., Maquennehan, V., Nkoma, G. B., Boissonneault, G. DNA damage response during chromatin remodeling in elongating spermatids of mice. Biol. Reprod. 78 (2), 324-332 (2008).
- Meistrich, M. L., Mohapatra, B., Shirley, C. R., Zhao, M. Roles of transition nuclear proteins in spermiogenesis. Chromosoma. 111 (8), 483-488 (2003).
- Grégoire, M. -. C., et al. Male-driven de novo mutations in haploid germ cells. Mol. Hum. Reprod. 19 (8), 495-499 (2013).
- Simard, O., et al. Instability of trinucleotidic repeats during chromatin remodeling in spermatids. Hum. Mutat. , (2014).
- Wykes, S. M., Krawetz, S. Separation of spermatogenic cells from adult transgenic mouse testes using unit-gravity sedimentation. Mol. Biotechnol. 25 (2), 131-138 (2003).
- Yoshida, S., et al. The first round of mouse spermatogenesis is a distinctive program that lacks the self-renewing spermatogonia stage. Development (Cambridge, England). 133 (8), 1495-1505 (2006).
- Moreno, R. D., Lizama, C., Urzúa, N., Vergara, S. P., Reyes, J. G. Caspase activation throughout the first wave of spermatogenesis in the rat. Cell Tissue Res. 325 (3), 533-540 (2006).
- Meistrich, M. L., Trostle-Weige, P. K., Van Beek, M. E. Separation of specific stages of spermatids from vitamin A-synchronized rat testes for assessment of nucleoprotein changes during spermiogenesis. Biol. Reprod. 51 (2), 334-344 (1994).
- van Pelt, A. M., de Rooij, D. G. Synchronization of the seminiferous epithelium after vitamin A replacement in vitamin A-deficient mice. Biol. Reprod. 43, 363-367 (1990).
- Getun, I. V., Torres, B., Bois, P. R. J. Flow cytometry purification of mouse meiotic cells. J. Vis. Exp. , (2011).
- Kovtun, I. V., McMurray, C. T. Trinucleotide expansion in haploid germ cells by gap repair. Nature Genet. 27 (4), 407-411 (2001).
- Bastos, H., et al. Flow cytometric characterization of viable meiotic and postmeiotic cells by Hoechst 33342 in mouse spermatogenesis. Cytometry A. 65 (1), 40-49 (2005).
- Lassalle, B., Ziyyat, A., Testart, J., Finaz, C., Lefèvre, A. Flow cytometric method to isolate round spermatids from mouse testis. Hum. Reprod. 14 (2), 388-394 (1999).
