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Retinoic Acid Receptors Control Spermatogonia Cell-Fate and Induce Expression of the SALL4A Transcription Factor.

Gely-Pernot A, Raverdeau M, Teletin M, Vernet N, Féret B, Klopfenstein M, Dennefeld C, Davidson I, Benoit G, Mark M, Ghyselinck NB - PLoS Genet. (2015)

Bottom Line: We also show that ATRA activates RAR and RXR bound to a conserved regulatory region to increase expression of the SALL4A transcription factor in spermatogonia.Our results reveal that this major pluripotency gene is a target of ATRA signaling and that RAR/RXR heterodimers are the functional units driving its expression in spermatogonia.They add to the mechanisms through which ATRA promote expression of the KIT tyrosine kinase receptor to trigger a critical step in spermatogonia differentiation.

View Article: PubMed Central - PubMed

Affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Département de Génétique Fonctionnelle et Cancer, Illkirch, France; Centre National de la Recherche Scientifique (CNRS), UMR7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (INSERM), U964, Illkirch, France; Université de Strasbourg (UNISTRA), Illkirch Cedex, France.

ABSTRACT
All-trans retinoic acid (ATRA) is instrumental to male germ cell differentiation, but its mechanism of action remains elusive. To address this question, we have analyzed the phenotypes of mice lacking, in spermatogonia, all rexinoid receptors (RXRA, RXRB and RXRG) or all ATRA receptors (RARA, RARB and RARG). We demonstrate that the combined ablation of RXRA and RXRB in spermatogonia recapitulates the set of defects observed both upon ablation of RAR in spermatogonia. We also show that ATRA activates RAR and RXR bound to a conserved regulatory region to increase expression of the SALL4A transcription factor in spermatogonia. Our results reveal that this major pluripotency gene is a target of ATRA signaling and that RAR/RXR heterodimers are the functional units driving its expression in spermatogonia. They add to the mechanisms through which ATRA promote expression of the KIT tyrosine kinase receptor to trigger a critical step in spermatogonia differentiation. Importantly, they indicate also that meiosis eventually occurs in the absence of a RAR/RXR pathway within germ cells and suggest that instructing this process is either ATRA-independent or requires an ATRA signal originating from Sertoli cells.

No MeSH data available.


Related in: MedlinePlus

RXRA and RXRB are both instrumental to spermatogonia differentiation.Mean percentages of tubule sections showing normal cellular associations (white bars), abnormal associations resembling the VAD situation with either one or two generations of germ cells lacking (grey bars), and degenerated epithelium containing only spermatogonia and Sertoli cells (black bars) in testes of 12 month-old mice (n = 5) with the indicated genotype. Mice lacking Rxrg and either Rxra (Rxra;gSgp–/– mutants) or Rxrb (Rxrb;gSgp–/– mutants) are marginally affected. In contrast, mice simultaneously lacking Rxra and Rxrb (Rxra;bSgp–/– mutant) displayed a high proportion of affected tubule sections. Additional ablation of Rxrg does not worsen the pathological phenotype (Rxra;bSgp–/– mutant). This indicates that RXRG is dispensable, whereas RXRA and RXRB are both required and exert redundant functions in spermatogonia.
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pgen.1005501.g002: RXRA and RXRB are both instrumental to spermatogonia differentiation.Mean percentages of tubule sections showing normal cellular associations (white bars), abnormal associations resembling the VAD situation with either one or two generations of germ cells lacking (grey bars), and degenerated epithelium containing only spermatogonia and Sertoli cells (black bars) in testes of 12 month-old mice (n = 5) with the indicated genotype. Mice lacking Rxrg and either Rxra (Rxra;gSgp–/– mutants) or Rxrb (Rxrb;gSgp–/– mutants) are marginally affected. In contrast, mice simultaneously lacking Rxra and Rxrb (Rxra;bSgp–/– mutant) displayed a high proportion of affected tubule sections. Additional ablation of Rxrg does not worsen the pathological phenotype (Rxra;bSgp–/– mutant). This indicates that RXRG is dispensable, whereas RXRA and RXRB are both required and exert redundant functions in spermatogonia.

Mentions: The different generations of germ cells form cellular associations of fixed composition called epithelial stages. In control testes only the twelve normal epithelial stages (I–XII) [17] were identified (Fig 1A). In contrast, analysis of 12-week-old Rxra;b;gSpg–/– mutant testes (n = 5), revealed that, aside from normal epithelial stages (Fig 1C), 36.3 ± 9.6% of the tubule sections exhibited a degenerated seminiferous epithelium (Fig 1B) either lacking a large proportion of germ cells (T3) or containing only spermatogonia and Sertoli cells (T4). In addition, 17.8 ± 3.4% of the tubule sections lacked, around their entire circumference, either one or two generations of germ cells, yielding abnormal variants of the epithelial stages (T2). The missing germ cell layers included: preleptotene spermatocytes (Fig 1E and 1G), pachytene spermatocytes (Fig 1D and 1H), and/or round spermatids (Fig 1F and 1H). Thus, germ cell differentiation appeared altered in Rxra;b;gSpg–/– mutants. Analysis of other combinations of compound mutants at the age of 12 weeks revealed that the pathological phenotype was generated solely upon the simultaneous ablation of Rxra and Rxrb (Fig 2). This indicates that both RXRA and RXRB exert redundant functions in spermatogonia, while RXRG is dispensable. One year-old controls (n = 4) displayed only normal germ cell associations, whereas mutants (n = 4) displayed tubule sections containing only Sertoli cells and spermatogonia (Fig 1I and 1J). The latter expressed molecular markers of undifferentiated spermatogonia such as Gfra1 and Zbtb16 [3,18], but not of differentiating spermatogonia such as Kit and Stra8 [2,19] (Fig 3A–3H).


Retinoic Acid Receptors Control Spermatogonia Cell-Fate and Induce Expression of the SALL4A Transcription Factor.

Gely-Pernot A, Raverdeau M, Teletin M, Vernet N, Féret B, Klopfenstein M, Dennefeld C, Davidson I, Benoit G, Mark M, Ghyselinck NB - PLoS Genet. (2015)

RXRA and RXRB are both instrumental to spermatogonia differentiation.Mean percentages of tubule sections showing normal cellular associations (white bars), abnormal associations resembling the VAD situation with either one or two generations of germ cells lacking (grey bars), and degenerated epithelium containing only spermatogonia and Sertoli cells (black bars) in testes of 12 month-old mice (n = 5) with the indicated genotype. Mice lacking Rxrg and either Rxra (Rxra;gSgp–/– mutants) or Rxrb (Rxrb;gSgp–/– mutants) are marginally affected. In contrast, mice simultaneously lacking Rxra and Rxrb (Rxra;bSgp–/– mutant) displayed a high proportion of affected tubule sections. Additional ablation of Rxrg does not worsen the pathological phenotype (Rxra;bSgp–/– mutant). This indicates that RXRG is dispensable, whereas RXRA and RXRB are both required and exert redundant functions in spermatogonia.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4591280&req=5

pgen.1005501.g002: RXRA and RXRB are both instrumental to spermatogonia differentiation.Mean percentages of tubule sections showing normal cellular associations (white bars), abnormal associations resembling the VAD situation with either one or two generations of germ cells lacking (grey bars), and degenerated epithelium containing only spermatogonia and Sertoli cells (black bars) in testes of 12 month-old mice (n = 5) with the indicated genotype. Mice lacking Rxrg and either Rxra (Rxra;gSgp–/– mutants) or Rxrb (Rxrb;gSgp–/– mutants) are marginally affected. In contrast, mice simultaneously lacking Rxra and Rxrb (Rxra;bSgp–/– mutant) displayed a high proportion of affected tubule sections. Additional ablation of Rxrg does not worsen the pathological phenotype (Rxra;bSgp–/– mutant). This indicates that RXRG is dispensable, whereas RXRA and RXRB are both required and exert redundant functions in spermatogonia.
Mentions: The different generations of germ cells form cellular associations of fixed composition called epithelial stages. In control testes only the twelve normal epithelial stages (I–XII) [17] were identified (Fig 1A). In contrast, analysis of 12-week-old Rxra;b;gSpg–/– mutant testes (n = 5), revealed that, aside from normal epithelial stages (Fig 1C), 36.3 ± 9.6% of the tubule sections exhibited a degenerated seminiferous epithelium (Fig 1B) either lacking a large proportion of germ cells (T3) or containing only spermatogonia and Sertoli cells (T4). In addition, 17.8 ± 3.4% of the tubule sections lacked, around their entire circumference, either one or two generations of germ cells, yielding abnormal variants of the epithelial stages (T2). The missing germ cell layers included: preleptotene spermatocytes (Fig 1E and 1G), pachytene spermatocytes (Fig 1D and 1H), and/or round spermatids (Fig 1F and 1H). Thus, germ cell differentiation appeared altered in Rxra;b;gSpg–/– mutants. Analysis of other combinations of compound mutants at the age of 12 weeks revealed that the pathological phenotype was generated solely upon the simultaneous ablation of Rxra and Rxrb (Fig 2). This indicates that both RXRA and RXRB exert redundant functions in spermatogonia, while RXRG is dispensable. One year-old controls (n = 4) displayed only normal germ cell associations, whereas mutants (n = 4) displayed tubule sections containing only Sertoli cells and spermatogonia (Fig 1I and 1J). The latter expressed molecular markers of undifferentiated spermatogonia such as Gfra1 and Zbtb16 [3,18], but not of differentiating spermatogonia such as Kit and Stra8 [2,19] (Fig 3A–3H).

Bottom Line: We also show that ATRA activates RAR and RXR bound to a conserved regulatory region to increase expression of the SALL4A transcription factor in spermatogonia.Our results reveal that this major pluripotency gene is a target of ATRA signaling and that RAR/RXR heterodimers are the functional units driving its expression in spermatogonia.They add to the mechanisms through which ATRA promote expression of the KIT tyrosine kinase receptor to trigger a critical step in spermatogonia differentiation.

View Article: PubMed Central - PubMed

Affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Département de Génétique Fonctionnelle et Cancer, Illkirch, France; Centre National de la Recherche Scientifique (CNRS), UMR7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (INSERM), U964, Illkirch, France; Université de Strasbourg (UNISTRA), Illkirch Cedex, France.

ABSTRACT
All-trans retinoic acid (ATRA) is instrumental to male germ cell differentiation, but its mechanism of action remains elusive. To address this question, we have analyzed the phenotypes of mice lacking, in spermatogonia, all rexinoid receptors (RXRA, RXRB and RXRG) or all ATRA receptors (RARA, RARB and RARG). We demonstrate that the combined ablation of RXRA and RXRB in spermatogonia recapitulates the set of defects observed both upon ablation of RAR in spermatogonia. We also show that ATRA activates RAR and RXR bound to a conserved regulatory region to increase expression of the SALL4A transcription factor in spermatogonia. Our results reveal that this major pluripotency gene is a target of ATRA signaling and that RAR/RXR heterodimers are the functional units driving its expression in spermatogonia. They add to the mechanisms through which ATRA promote expression of the KIT tyrosine kinase receptor to trigger a critical step in spermatogonia differentiation. Importantly, they indicate also that meiosis eventually occurs in the absence of a RAR/RXR pathway within germ cells and suggest that instructing this process is either ATRA-independent or requires an ATRA signal originating from Sertoli cells.

No MeSH data available.


Related in: MedlinePlus