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Transcriptome analysis of highly purified mouse spermatogenic cell populations: gene expression signatures switch from meiotic-to postmeiotic-related processes at pachytene stage.

da Cruz I, Rodríguez-Casuriaga R, Santiñaque FF, Farías J, Curti G, Capoano CA, Folle GA, Benavente R, Sotelo-Silveira JR, Geisinger A - BMC Genomics (2016)

Bottom Line: Interestingly, we found that a considerable number of genes involved in early as well as late meiotic processes are already on at early meiotic prophase, with a high proportion of them being expressed only for the short time lapse of lepto-zygotene stages.Moreover, we found that a good proportion of the differential gene expression in spermiogenesis corresponds to up-regulation of genes whose expression starts earlier, at pachytene stage; this includes transition protein-and protamine-coding genes, which have long been claimed to switch on during spermiogenesis.In addition, our results afford new insights concerning X chromosome meiotic inactivation and reactivation.

View Article: PubMed Central - PubMed

Affiliation: Department of Genomics, Instituto de Investigaciones Biológicas Clemente Estable (IIBCE), Av. Italia 3318, 11,600, Montevideo, Uruguay.

ABSTRACT

Background: Spermatogenesis is a complex differentiation process that involves the successive and simultaneous execution of three different gene expression programs: mitotic proliferation of spermatogonia, meiosis, and spermiogenesis. Testicular cell heterogeneity has hindered its molecular analyses. Moreover, the characterization of short, poorly represented cell stages such as initial meiotic prophase ones (leptotene and zygotene) has remained elusive, despite their crucial importance for understanding the fundamentals of meiosis.

Results: We have developed a flow cytometry-based approach for obtaining highly pure stage-specific spermatogenic cell populations, including early meiotic prophase. Here we combined this methodology with next generation sequencing, which enabled the analysis of meiotic and postmeiotic gene expression signatures in mouse with unprecedented reliability. Interestingly, we found that a considerable number of genes involved in early as well as late meiotic processes are already on at early meiotic prophase, with a high proportion of them being expressed only for the short time lapse of lepto-zygotene stages. Besides, we observed a massive change in gene expression patterns during medium meiotic prophase (pachytene) when mostly genes related to spermiogenesis and sperm function are already turned on. This indicates that the transcriptional switch from meiosis to post-meiosis takes place very early, during meiotic prophase, thus disclosing a higher incidence of post-transcriptional regulation in spermatogenesis than previously reported. Moreover, we found that a good proportion of the differential gene expression in spermiogenesis corresponds to up-regulation of genes whose expression starts earlier, at pachytene stage; this includes transition protein-and protamine-coding genes, which have long been claimed to switch on during spermiogenesis. In addition, our results afford new insights concerning X chromosome meiotic inactivation and reactivation.

Conclusions: This work provides for the first time an overview of the time course for the massive onset and turning off of the meiotic and spermiogenic genetic programs. Importantly, our data represent a highly reliable information set about gene expression in pure testicular cell populations including early meiotic prophase, for further data mining towards the elucidation of the molecular bases of male reproduction in mammals.

No MeSH data available.


Related in: MedlinePlus

Representation of the transcription and execution times of four selected GO categories. The diagram represents the time when the biological processes shown in the heat maps in Figs. 4c and 5c are transcriptionally activated, and when these processes are executed along the first spermatogenic wave in mouse. The onset (in dpp) for the different stages along the first spermatogenic wave is denoted on top. The time of histone substitution - first by TNP and then by PRM - is also represented. PGC: primordial germ cells; Spg: spermatogonia; PL: preleptotene; L: leptotene; Z: zygotene; P: pachytene; D: diplotene; M: meiotic divisions
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Fig8: Representation of the transcription and execution times of four selected GO categories. The diagram represents the time when the biological processes shown in the heat maps in Figs. 4c and 5c are transcriptionally activated, and when these processes are executed along the first spermatogenic wave in mouse. The onset (in dpp) for the different stages along the first spermatogenic wave is denoted on top. The time of histone substitution - first by TNP and then by PRM - is also represented. PGC: primordial germ cells; Spg: spermatogonia; PL: preleptotene; L: leptotene; Z: zygotene; P: pachytene; D: diplotene; M: meiotic divisions

Mentions: The two GO categories we chose for exemplifying the early transcription of meiotic genes, which represent meiotic prophase (“reciprocal meiotic recombination”) and late meiotic events (“meiotic chromosome segregation”) respectively, are illustrated in Fig. 8. Noteworthy, there is a gap between the time when these programs are transcriptionally activated, and the time when they are executed. Moreover, as stated above, many of the implicated genes are down-regulated before P. A logical conclusion of the aforementioned is that these transcripts must be mostly translated in LZ (i.e. before their degradation) and, for those proteins whose product remains present/active beyond LZ, the protein should be kept for longer. In this regard, a recent proteomic study described different regulation mechanisms for the dynamic gene expression changes that take place during spermatogenesis [69]. Interestingly, one of those mechanisms, which the authors termed “transcript degradation”, refers to genes whose mRNA levels drop from spermatogonia to PS while their protein levels remain relatively constant until marked for degradation at a later stage. Despite the facts that only a limited number of proteins were identified in that study, and that it did not include the LZ stages, “transcript degradation” would probably describe the regulatory mechanism for many genes within the LZ peak.Fig. 8


Transcriptome analysis of highly purified mouse spermatogenic cell populations: gene expression signatures switch from meiotic-to postmeiotic-related processes at pachytene stage.

da Cruz I, Rodríguez-Casuriaga R, Santiñaque FF, Farías J, Curti G, Capoano CA, Folle GA, Benavente R, Sotelo-Silveira JR, Geisinger A - BMC Genomics (2016)

Representation of the transcription and execution times of four selected GO categories. The diagram represents the time when the biological processes shown in the heat maps in Figs. 4c and 5c are transcriptionally activated, and when these processes are executed along the first spermatogenic wave in mouse. The onset (in dpp) for the different stages along the first spermatogenic wave is denoted on top. The time of histone substitution - first by TNP and then by PRM - is also represented. PGC: primordial germ cells; Spg: spermatogonia; PL: preleptotene; L: leptotene; Z: zygotene; P: pachytene; D: diplotene; M: meiotic divisions
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4837615&req=5

Fig8: Representation of the transcription and execution times of four selected GO categories. The diagram represents the time when the biological processes shown in the heat maps in Figs. 4c and 5c are transcriptionally activated, and when these processes are executed along the first spermatogenic wave in mouse. The onset (in dpp) for the different stages along the first spermatogenic wave is denoted on top. The time of histone substitution - first by TNP and then by PRM - is also represented. PGC: primordial germ cells; Spg: spermatogonia; PL: preleptotene; L: leptotene; Z: zygotene; P: pachytene; D: diplotene; M: meiotic divisions
Mentions: The two GO categories we chose for exemplifying the early transcription of meiotic genes, which represent meiotic prophase (“reciprocal meiotic recombination”) and late meiotic events (“meiotic chromosome segregation”) respectively, are illustrated in Fig. 8. Noteworthy, there is a gap between the time when these programs are transcriptionally activated, and the time when they are executed. Moreover, as stated above, many of the implicated genes are down-regulated before P. A logical conclusion of the aforementioned is that these transcripts must be mostly translated in LZ (i.e. before their degradation) and, for those proteins whose product remains present/active beyond LZ, the protein should be kept for longer. In this regard, a recent proteomic study described different regulation mechanisms for the dynamic gene expression changes that take place during spermatogenesis [69]. Interestingly, one of those mechanisms, which the authors termed “transcript degradation”, refers to genes whose mRNA levels drop from spermatogonia to PS while their protein levels remain relatively constant until marked for degradation at a later stage. Despite the facts that only a limited number of proteins were identified in that study, and that it did not include the LZ stages, “transcript degradation” would probably describe the regulatory mechanism for many genes within the LZ peak.Fig. 8

Bottom Line: Interestingly, we found that a considerable number of genes involved in early as well as late meiotic processes are already on at early meiotic prophase, with a high proportion of them being expressed only for the short time lapse of lepto-zygotene stages.Moreover, we found that a good proportion of the differential gene expression in spermiogenesis corresponds to up-regulation of genes whose expression starts earlier, at pachytene stage; this includes transition protein-and protamine-coding genes, which have long been claimed to switch on during spermiogenesis.In addition, our results afford new insights concerning X chromosome meiotic inactivation and reactivation.

View Article: PubMed Central - PubMed

Affiliation: Department of Genomics, Instituto de Investigaciones Biológicas Clemente Estable (IIBCE), Av. Italia 3318, 11,600, Montevideo, Uruguay.

ABSTRACT

Background: Spermatogenesis is a complex differentiation process that involves the successive and simultaneous execution of three different gene expression programs: mitotic proliferation of spermatogonia, meiosis, and spermiogenesis. Testicular cell heterogeneity has hindered its molecular analyses. Moreover, the characterization of short, poorly represented cell stages such as initial meiotic prophase ones (leptotene and zygotene) has remained elusive, despite their crucial importance for understanding the fundamentals of meiosis.

Results: We have developed a flow cytometry-based approach for obtaining highly pure stage-specific spermatogenic cell populations, including early meiotic prophase. Here we combined this methodology with next generation sequencing, which enabled the analysis of meiotic and postmeiotic gene expression signatures in mouse with unprecedented reliability. Interestingly, we found that a considerable number of genes involved in early as well as late meiotic processes are already on at early meiotic prophase, with a high proportion of them being expressed only for the short time lapse of lepto-zygotene stages. Besides, we observed a massive change in gene expression patterns during medium meiotic prophase (pachytene) when mostly genes related to spermiogenesis and sperm function are already turned on. This indicates that the transcriptional switch from meiosis to post-meiosis takes place very early, during meiotic prophase, thus disclosing a higher incidence of post-transcriptional regulation in spermatogenesis than previously reported. Moreover, we found that a good proportion of the differential gene expression in spermiogenesis corresponds to up-regulation of genes whose expression starts earlier, at pachytene stage; this includes transition protein-and protamine-coding genes, which have long been claimed to switch on during spermiogenesis. In addition, our results afford new insights concerning X chromosome meiotic inactivation and reactivation.

Conclusions: This work provides for the first time an overview of the time course for the massive onset and turning off of the meiotic and spermiogenic genetic programs. Importantly, our data represent a highly reliable information set about gene expression in pure testicular cell populations including early meiotic prophase, for further data mining towards the elucidation of the molecular bases of male reproduction in mammals.

No MeSH data available.


Related in: MedlinePlus