Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP/Collège de France, BP163, 67404 Illkirch-cedex, France
* Present address: Brain Research Institute, University and ETH Zurich, Winterthurerstrasse 190, CH 8057 Zurich, Switzerland
These authors contributed equally to this work
Authors for correspondence (e-mail: losson{at}titus.u-strasbg.fr and marek{at}titus.u-strasbg.fr)
Accepted 22 February 2002
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SUMMARY |
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Key words: Heterochromatin protein 1, Transcriptional silencing, KRAB zinc-finger proteins, Testis-specific conditional knockout, Cellular interactions, Mouse
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INTRODUCTION |
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Mammalian transcriptional intermediary factor 1ß (TIF1ß; Trim28 Mouse Genome Informatics) (also called KAP-1 or KRIP-1), which was originally identified as a co-repressor for the large family of KRAB domain-containing zinc-finger proteins (Friedman et al., 1996; Kim et al., 1996
; Moosmann et al., 1996
), has also been defined as a member of an emerging family of transcriptional regulators that includes TIF1
and TIF1
in mammals (Le Douarin et al., 1995
; Le Douarin et al., 1996
; Venturini et al., 1999
), and Bonus in Drosophila (Beckstead et al., 2001
). The domain structure that characterizes these proteins consists of an N-terminal RBCC (RING finger, B boxes, coiled coil) motif and a C-terminal bromodomain preceded by a PHD finger (Le Douarin et al., 1996
). All TIF1 family members have been reported to repress basal and activated transcription when tethered to DNA through fusion to an heterologous DNA-binding domain. In the case of TIF1ß, an epigenetic mechanism of control has been suggested by the finding of an association with members of the heterochromatin protein 1 (HP1) family (Nielsen et al., 1999
; Ryan et al., 1999
), a class of non-histone chromosomal proteins with a well-established function in heterochromatin-mediated silencing (reviewed by Eissenberg and Elgin, 2000
). TIF1ß has been shown to colocalize with members of the HP1 family in interphase nuclei of several mammalian cell lines (Nielsen et al., 1999
; Ryan et al., 1999
). In vitro, TIF1ß interacts with and phosphorylates the HP1 proteins (Nielsen et al., 1999
). This interaction is required for the TIF1ß-mediated repression of transcription (Nielsen et al., 1999
; Ryan et al., 1999
) and for its association with pericentromeric heterochromatin in cultured cells (Matsuda et al., 2001
) (F. C., M. Oulad-Abdelghani, J. L. Vonesch, P. C. and R. L., unpublished). A mechanistic link between TIF1ß repression and histone modification has also been established, with the demonstration that deacetylase inhibitors such as Trichostatin A can interfere with TIF1ß-mediated repression in transient transfection assays (Nielsen et al., 1999
; Schultz et al., 2001
). In agreement with this result, TIF1ß has recently been reported to be an intrinsic component of a novel histone deacetylase complex, called N-CoR-1 (Underhill et al., 2000
), and to interact both physically and functionally with the subunit Mi-2
of the nucleosome remodeling and deacetylation (NuRD) complex (Schultz et al., 2001
). Thus, TIF1ß may exert its co-repressor function via the assembly and/or maintenance of transcriptionally inactive, higher order chromatin structures through histone deacetylation and heterochromatinization.
We have recently shown that mice devoid of Tif1ß expression die at the egg cylinder stage, prior to the onset of gastrulation (Cammas et al., 2000). Analysis of the Tif1ß-null embryos has revealed a reduced cell number in the ectoderm, morphological alterations of the visceral endoderm and absence of mesoderm formation (Cammas et al., 2000
). This phenotype indicates that TIF1ß exerts essential functions in early embryogenesis. However, the lethal outcome of this null mutation precludes the analysis of the roles of TIF1ß in later developmental and cell differentiation processes. Spermatogenesis is a cyclic cell differentiation process that includes spermatogonia self-renewal and their differentiation towards spermatozoa. We now show that during spermatogenesis, TIF1ß is expressed in a finely regulated pattern and is preferentially associated with heterochromatin. To investigate whether TIF1ß has a role in spermatogenesis, we have generated a conditional germline-specific Tif1ß mutation in mice by using the tamoxifen-inducible Cre-ERT/loxP recombination system (Metzger and Chambon, 2001
). Mice homozygous for a conditional allele of Tif1ß (TIFßL2/L2), an allele in which essential coding exons are flanked by loxP sites (Cammas et al., 2000
), were crossed with a transgenic PrP-Cre-ERT(tg/0) hemizygous line, in which tamoxifen selectively induces DNA excision in spermatogonia and spermatocytes (P. W., C. G., M. M., D. M. and P. C., unpublished). Analysis of the testes of tamoxifen-treated TIF1ßL2/L2:PrP-Cre-ERT(tg/0) mice reveals that TIF1ß plays a key role in the maintenance of spermatogenesis.
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MATERIALS AND METHODS |
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Transgenic mice harboring a testis-restricted expression of the ligand-inducible Cre-ERT (Feil et al., 1996) under control of the murine Prion (PrP)-promoter (PrP-Cre-ERT line 28.8) are described elsewhere (P. W., C. G., M. M., D. M. and P. C., unpublished). Tif1ßL2/L2 males with (PrP-Cre-ERT(tg/0)) or without (PrP-Cre-ERT(0/0)) the testis-specific transgene were generated and injected intra-peritoneally (IP) at 4 weeks of age for 5 consecutive days with tamoxifen (1 mg/day) (Metzger and Chambon, 2001
). Experimental (TIF1ßL2/L2:PrP-Cre-ERT(tg/0)) and control (TIF1ßL2/L2:PrP-Cre-ERT(0/0)) males were sacrificed 1 day, and 2, 4, 6, 7 and 8 weeks after tamoxifen treatment (i.e. after the last tamoxifen injection).
Immunohistochemical detection of TIF1ß in mouse testes
Rabbit antisera were raised against two peptides (PF64 and PF65) corresponding to the N-terminal sequence (amino acids 140-154 and 66-80, respectively) of the TIF1ß protein and purified on a sulfolink coupling gel (Oulad-Abdelghani et al., 1996). Cellular localization of TIF1ß in testis of TIF1ßL2/L2:PrP-Cre-ERT(0/0) mice was performed on 10 µm thick cryosections hydrated in phosphate-buffered saline (PBS) and fixed in 4% paraformaldehyde (PFA) in PBS (for 10 minutes at 4°C). Sections were rinsed in PBS containing 0.1% Triton X-100 (PBST; 3x5 minutes at room temperature), then saturated with 5% normal goat serum (NGS) in PBST (30 minutes at room temperature), and incubated with the antibody against the PF64 and PF65 peptides (4 µg/ml; 2 hours at room temperature). Sections were washed in PBST (3x5 minutes), then PBS (5 minutes), incubated with the secondary antibody (Cy3-coupled donkey anti-rabbit diluted at 1/400 in PBS, Jackson Laboratories) (1 hour at room temperature), washed in PBST and mounted in Vectashield (Vector) containing DAPI at 10 µg/µl. In another set of immunohistochemical experiments, testis of TIF1ßL2/L2:PrP-Cre-ERT(tg/0) (experimental) and TIF1ßL2/L2:PrP-Cre-ERT(0/0) (control) mice were fixed in 4% PFA in PBS (16 hours at 4°C) and embedded in paraplast. Sections (7 µm) were dewaxed, hydrated, rinsed in PBS, then placed into 5 mM sodium citrate buffer pH 6.0 and exposed to a microwave treatment (power output 800 W; 2x2.5 minutes) (Balaton et al., 1993
). After cooling down to room temperature, sections were rinsed in PBST, treated with 5% NGS in PBST (30 minutes) to block nonspecific antibody binding to the tissue sections and incubated for 16 hours at 4°C with the anti-PF64 and PF65 antibodies. Sections were then washed, incubated with the secondary antibody (1 hour at room temperature) and mounted as described for cryosections.
Preliminary experiments indicated that the antibodies against PF64 and PF65 labeled the same cells in the seminiferous epithelium. However, the signal was more intense with the later antibody, which was therefore used in subsequent immunostaining experiments. In immunohistochemical experiments, some differences were observed in the nuclear localization of TIF1ß and intensities of the signals in germ cell and Sertoli cell between frozen and microwave-treated paraffin wax-embedded sections. These differences were reproduced with both anti-PF64 and anti-PF65 antibodies. They could not be accounted by prolonged fixation in paraformaldehyde before paraffin wax embedding (i.e. 16 hours versus 10 minutes after cryosectioning) nor by the microwave treatment. Indeed, prolonged post-fixation of cryosections for 16 hours resulted in a global decrease of the anti-TIF1ß immunoreactivity in all cell types within the seminiferous epithelium. Likewise, microwave treatment globally restored the immunostaining that was decreased in all cell types upon a 16 hours stay of the tissue in paraformaldehyde. These differences in immunostaining may result from diffusion of the TIF1ß protein within the chromatin during the paraffin wax embedding process. As negative controls of the immunostaining procedure, histological sections were incubated either with non-immune rabbit IgGs (5 µg/ml) or with a mixture of the primary antibody and 12-fold excess of the immunizing peptide (10 µg/ml).
Histological analysis and detection of proliferating and apoptotic cells
For histological analysis, testes of tamoxifen-treated TIF1ßL2/L2:PrP-Cre-ERT(tg/0) and TIF1ßL2/L2:PrP-Cre-ERT(0/0) mice were fixed in Bouins fluid. Paraffin wax embedded sections (7 µm) were stained with Hematoxylin and Mallorys trichrome (Mark et al., 1993). Detection of apoptotic cells on sections from PFA-fixed and paraffin wax-embedded testes was performed by TdT-mediated dUTP nick end labeling (TUNEL), according to the manufacturers instructions (In Situ Cell Death Detection Kit, Fluorescein, Roche); sections were counterstained with DAPI. To identify proliferating cells, adult TIF1ßL2/L2:PrP-Cre-ERT(0/0) mice were injected intra-peritoneally four times at intervals of 2 hours with 50 mg/kg of BrdU. Testis were collected 2 hours after the last BrdU injection, fixed in 4% PFA in PBS (16 hours; 4°C). Paraffin wax-embedded sections were incubated with an antibody against BrdU (Boehringer Mannheim) diluted 1/100 in 0.1% NGS/PBS (16 hours; 4°C), revealed with Cy3-conjugated donkey anti-rabbit IgG, and mounted in Vectashield medium containing DAPI.
Statistical analysis
The number of seminiferous tubules showing abnormal expression of TIF1ß (i.e. partial staining along the circumference of spermatocyte and/or spermatid layers in a given tubular cross section, instead of staining along the whole circumference of these layers) was scored on testes from TIF1ßL2/L2:PrP-Cre-ERT(tg/0) and TIF1ßL2/L2:PrP-Cre-ERT(0/0) animals 2 weeks after tamoxifen treatment. The number of degenerating tubules (i.e. tubules showing signs of vacuolation) was scored on histological sections from testes of TIF1ßL2/L2:PrP-Cre-ERT(tg/0) and TIF1ßL2/L2:PrP-Cre-ERT(0/0) 8 weeks after tamoxifen treatment. Testicular sections of three individuals were analyzed for each genotype and experimental group. Statistical analysis of data was performed using ANOVA and the Fischers protected least significant difference test (Fischers PLSD).
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RESULTS |
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Immunostaining with the anti-TIF1ß antibody of microwave-treated paraffin wax-embedded sections from control testes revealed an intense fluorescent signal in many spermatocytes (P in Fig. 2A-C) and round spermatids (RS). The signal detected in Sertoli cells (S) was in general weaker than that observed on frozen sections. Moreover, in both germ cells and Sertoli cells, this immunostaining was exclusively nuclear, but was evenly distributed in the nucleus, instead of being associated with heterochromatin, as in the case of frozen sections (see Materials and Methods). Detection of TIF1ß in germ cells was dependent on their state of maturation and, therefore, on the stage of the seminiferous epithelium cycle (Russell et al., 1990) (see legend of Fig. 1). Immunostaining was undetectable in spermatogonia (SG) and young (preleptotene, leptotene, zygotene and early pachytene) spermatocytes (PR and L) (Fig. 2A-C and data not shown). It was intense in growing pachytene and in diplotene spermatocytes populating stage VI-XI tubules (P, Fig. 2A-C), at all steps of round spermatid maturation (e.g. RS in Fig. 2A,C) and in early elongating spermatids (i.e. step 9 spermatids, data not shown). Step 10 spermatids were only faintly immunostained (ES-10, Fig. 2B and data not shown), and spermatids at later stages of elongation (i.e. steps 11-16) were negative (ES-16 in Fig. 2A,C and data not shown). Unmasking of the epitope after microwave-induced disruption of heterochromatin structures in germ cells is likely to account for the discrepancies in patterns and intensities of immunostaining between sections from frozen and paraffin wax-embedded testes. These discrepancies were reproduced with antibodies raised against two distinct peptides derived from TIF1ß, indicating that they were not caused by auto-antibodies that might contaminate rabbit antisera. Note also that no immunostaining could be found when the primary antibody was replaced by non-immune IgG or a mixture of the primary antibody and immunizing peptide (data not shown).
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PrP-Cre-ERT mediates inactivation of the floxed TIF1ß gene in spermatogonia and spermatocytes
PrP-Cre-ERT transgenic mice (line 28.8), which enable a tamoxifen-induced time-controlled and tissue-specific DNA excision in germ cells are described elsewhere (P. W., C. G., M. M., D. M. and P. C., unpublished). Before tamoxifen treatment, TIF1ßL2/L2:PrP-Cre-ERT(tg/0) mice harboring both Tif1ß floxed alleles and the PrP-Cre-ERT transgene (referred hereafter as experimental animals) were normal with respect to fertility and testicular morphology (data not shown). The feasibility of spatiotemporal inactivation of TIF1ß in the testis was assessed by following up the disappearance of the TIF1ß protein on histological sections of experimental animals at different time points after tamoxifen treatment. For the sake of simplicity, only observations of tubular cross-sections in stage VII (and beginning of stage VIII) will be reported, unless otherwise mentioned. Stage VII (and the beginning of stage VIII) are characterized by the alignment of elongated spermatid nuclei at the luminal side of the seminiferous epithelium, immediately before their release, as spermatozoa, into the lumen of the seminiferous tubules. Histological sections of TIF1ß control (TIF1ßL2/L2:PrP-Cre-ERT(0/0)) testes displayed a normal TIF1ß signal in all seminiferous tubules one day and 2, 4, 6 and 8 weeks after tamoxifen treatment (Fig. 3A and data not shown). By contrast, experimental (TIF1ßL2/L2:PrP-Cre-ERT(tg/0)) testes displayed an abnormal pattern of TIF1ß distribution as early as 1 day after the end of the tamoxifen treatment: all pachytene spermatocytes were negative for TIF1ß (Fig. 3B). This finding indicates that the induced Cre can rapidly and efficiently mediate disruption of the floxed Tif1ß gene in most (possibly all) spermatocytes. Experimental testes analyzed 2, 4 and 6 weeks after tamoxifen treatment contained only histologically normal seminiferous tubules, which were classified into three categories based on TIF1ß expression patterns: (1) tubules expressing TIF1ß specifically in pachytene spermatocytes and round spermatids, which were undistinguishable from their counterparts in controls (Fig. 3C); (2) tubules devoid of TIF1ß positive germ cells (Fig. 3D); (3) tubules showing an abnormal, mosaic, expression of TIF1ß in pachytene spermatocytes and/or round spermatids (Fig. 3E,F).
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DISCUSSION |
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We have shown here that the TIF1ß protein is expressed in germ cells during a restricted window of time corresponding to the maturation of mid-pachytene spermatocytes into elongating (i.e. step 10) spermatids, and is associated with heterochromatin structures in these cells. TIF1ß is localized preferentially with the chromocenter of round (i.e. step 1 to step 9) spermatids indicating that it might repress expression of specific genes by sequestering them in this subnuclear compartment (Francastel et al., 2000). However, as TIF1ß expression is turned off prior to the onset of spermatid condensation, it is unlikely to be necessary for the protamine-dependent DNA compaction process which is characteristic of spermiogenesis (Kistler et al., 1996
; Sassone-Corsi, 1997
; Baarends et al., 1999
). Moreover, although it is expressed in pachytene spermatocytes, TIF1ß may also be dispensable for chromatin remodeling processes during meiosis, as TIF1ß-deficient spermatocytes can generate morphologically normal TIF1ß-deficient round spermatids, which in turn yield terminally differentiated condensed spermatids. Whether this reflects a possible functional redundancy with other members of the TIF1 family remains to be determined. Indeed, based on biochemical data, both TIF1
and TIF1ß have previously been shown to interact directly with HP1 proteins (Le Douarin et al., 1996
). However, in the case of TIF1
, the biological significance of the HP1 interaction is unclear, as TIF1
does not require HP1 binding for repression in a transfection assay (Nielsen et al., 1999
), and no significant subnuclear colocalization of TIF1
and HP1
has been observed in cultured cells (Remboutsika et al., 1999
). Moreover, TIF1ß, but neither TIF1
nor TIF1
, has been reported to interact with and act as a co-repressor for KRAB domains (Abrink et al., 2001
), supporting the view that members of the TIF1 family may be functionally distinct.
TIF1ß has nevertheless important physiological functions in the maintenance of the structural integrity of the seminiferous epithelium, as its loss in spermatocytes and round spermatids results in testicular degeneration with complete disappearance of germ cells. Spermatogenesis is crucially dependent on intimate contacts and paracrine interactions between Sertoli cells and germ cells. Sertoli cells support and nurture the germ cells (Russell et al., 1990; Sharpe, 1993
; Griswold, 1998
). Spermatocytes and spermatids can, in turn, influence Sertoli cell functions and gene expression, as demonstrated in models of germ cell depletion in vivo and in co-cultures of Sertoli and germ cells (Jegou, 1993
; Boujrad et al., 1995
; Syed and Hecht, 1997
; Wright et al., 1995
; Griswold, 1995
; Yomogida et al., 1994
). The disappearance of TIF1ß in TIF1ßL2/L2:PrP-Cre-ERT(tg/0) spermatocytes after tamoxifen treatment and the subsequent generation, within the next 10 days (Oakberg, 1956a
), of TIF1ß-deficient round spermatids from these TIF1ß-less spermatocytes, indicates that TIF1ß is not cell-autonomously required for their survival and differentiation. Thus, the timing of degeneration of the TIF1ß-less seminiferous epithelium rather suggests that Tif1ß expression is required for short-range cellular interactions in this epithelium. For example, TIF1ß present in round spermatids could, indirectly, regulate the expression of a Sertoli cell-derived factor(s) that mediate cell adhesion; the generation of TIF1ß-deficient round spermatids, as a consequence of Tif1ß disruption, may progressively result in depletion of this Sertoli cell factor, leading to immature germ cells detachment. However, neither shedding of immature germ cells, nor germ cell apoptosis can account for the observed selective depletion in spermatogonia and spermatocytes in TIF1ß-deficient degenerating seminiferous tubules still containing spermatids. Rather, this window of missing germ cells may reflect an absence of spermatogonial proliferation or a failure of self-renewing stem spermatogonia to maintain their normal, undifferentiated, state. In any event, as TIF1ß is not detectable in wild-type spermatogonia at any stage of the cycle of the seminiferous epithelium, the deleterious effects of its ablation on this cell type must be mediated through paracrine mechanisms possibly involving Sertoli cells. Accordingly, it is interesting to note that BMP8B secreted by spermatocytes and round spermatids is thought to play an important role in the paracrine regulation of spermatogonial self-renewal and/or differentiation (Zhao et al., 1996
). Similar functions in the regulation of spermatogonial cell fate decision have been ascribed to Sertoli cell-derived GDNF (Meng et al., 2000
), but it is not known whether secretion of GDNF is under germ cell control.
In conclusion, we have demonstrated that TIF1ß is localized preferentially in heterochromatin of round spermatids, indicating that it might repress expression of specific genes in these cells. Moreover, the observation that seminiferous tubules in which Tif1ß is specifically disrupted in spermatogonia are initially normal, while they subsequently degenerate, indicates that TIF1ß has important functions in the homeostasis of the seminiferous epithelium, and probably plays a crucial role in the network of paracrine interactions between germ cell subpopulations and/or Sertoli cells.
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ACKNOWLEDGMENTS |
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REFERENCES |
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---|
Abrink, M., Ortiz, J. A., Mark, C., Sanchez, C., Looman, C., Hellman, L., Chambon, P. and Losson, R. (2001). Conserved interaction between distinct Krüppel-associated box domains and the transcriptional intermediary factor 1 ß. Proc. Natl. Acad. Sci. USA 98, 1422-1426.
Baarends, W. M., Hoogerbrugge, J. W., Roest, H. P., Ooms, M., Vreeburg, J., Hoeijmakers, J. H. and Grootegoed, J. A. (1999). Histone ubiquitination and chromatin remodeling in mouse spermatogenesis. Dev. Biol. 207, 322-333.[Medline]
Balaton, A. J., Ochando, F. and Painchaud, M. H. (1993). Use of microwaves for enhancing or restoring antigens before immunohistochemical staining. Ann. Pathol. 13, 188-189.[Medline]
Barcellona, M. L. and Gratton, E. (1990). The fluorescence properties of a DNA probe. 4-6-Diamidino-2-phenylindole (DAPI). Eur. Biophys. J. 17, 315-323.[Medline]
Beckstead, R., Ortiz, J. A., Sanchez, C., Prokopenko, S. N., Chambon, P., Losson, R. and Bellen, H. (2001). Bonus, a Drosophila homolog of TIF1 proteins, interacts with nuclear receptors and can inhibit ßFTZ-F1-dependent transcription. Mol. Cell 7, 753-765.[Medline]
Boujrad, N., Hochereau-de Reviers, M. T. and Carreau, S. (1995). Evidence for germ cell control of Sertoli cell function in three models of germ cell depletion in adult rat. Biol. Reprod. 53, 1345-1352.[Abstract]
Brinster, R. L. and Avarbock, M. R. (1994). Germline transmission of donor haplotype following spermatogonial transplantation. Proc. Natl. Acad. Sci. USA 91, 11303-11307.
Brinster, R. L. and Zimmermann, J. W. (1994). Spermatogenesis following male germ-cell transplantation. Proc. Natl. Acad. Sci. USA 91, 11293-11302.
Cammas, F., Mark, M., Dollé, P., Dierich, A., Chambon, P. and Losson, R. (2000). Mice lacking the transcriptional corepressor TIF1ß are defective in early postimplantation development. Development 127, 2955-2963.
Cockell, M. and Gasser, S. (1999). Nuclear compartments and gene regulation. Curr. Opin. Genet. Dev. 9, 199-205.[Medline]
Dupé, V., Davenne, M., Brocard, J., Dollé, P., Mark, M., Dierich, A., Chambon, P. and Rijli, F. M. (1997). In vivo functional analysis of the Hoxa-1 3' retinoic acid response element (3'RARE). Development 124, 399-410.
Eissenberg, J. C. and Elgin, S. C. R. (2000). The HP1 protein family: getting a grip on chromatin. Curr. Opin. Genet. Dev. 10, 204-210.[Medline]
Feil, R., Brocard, J., Mascrez, B., LeMeur, M., Metzger, D. and Chambon, P. (1996). Ligand-activated site-specific recombination in mice. Proc. Natl. Acad. Sci. USA 93, 10887-10890.
Francastel, C., Schubeler, D., Martin, D. I. and Groudine, M. (2000). Nuclear compartmentalization and gene activity. Nat. Rev. Mol. Cell Biol. 1, 137-143.[Medline]
Friedman, J. R., Fredericks, W. J., Jensen, D. E., Speicher, D. W., Huang, X.-P., Neilson, E. G. and Rauscher, F. J., III (1996). KAP-1, a novel corepressor for the highly conserved KRAB repression domain. Genes Dev. 10, 2067-2078.[Abstract]
Griswold, M. D. (1995). Interactions between germ cells and Sertoli cells in the testis. Biol. Reprod. 52, 211-216.[Abstract]
Griswold, M. D. (1998). The central role of Sertoli cells in spermatogenesis. Semin. Cell Dev. Biol. 9, 411-416.[Medline]
Grootegoed, J. A., Siep, M. and Baarends, W. M. (2000). Molecular and cellular mechanisms in spermatogenesis. Baillieres Clin. Endocrinol. Metab. 14, 331-343.
Hampsey, M. and Reinberg, D. (1999). RNA polymerase II as a control panel for multiple coactivator complexes. Curr. Opin. Genet. Dev. 2, 132-139.
Hassan, A. H., Neely, K. E., Vignali, M., Reese, J. C. and Workman, J. L. (2001). Promoter targeting of chromatin-modifying complexes. Front. Biosci. 6, 1054-1064.
Hoyer-Fender, S., Singh, P. B. and Motzkus, D. (2000). The murine heterochromatin protein M31 is associated with the chromocenter in round spermatids and is a component of mature spermatozoa. Exp. Cell Res. 254, 72-79.[Medline]
Jégou, B. (1993). The Sertoli-germ cell communication network in mammals. Int. Rev. Cytol. 147, 25-96.[Medline]
Kastner, P., Mark, M., Leid, M., Gansmuller, A., Chin, W., Grondona, J. M., Decimo, D., Krezel, W., Dierich, A. and Chambon, P. (1996). Abnormal spermatogenesis in RXR beta mutant mice. Genes Dev. 10, 80-92.[Abstract]
Kim, S.-S., Chen, Y.-M., OLeary, E., Witzgall, R., Vidal, M. and Bonventre, J. V. (1996). A novel member of the RING finger family, KRIP-1, associates with the KRAB-A transcriptional repressor domain of zinc finger proteins. Proc. Natl. Acad. Sci. USA 93, 15299-15304.
Kistler, W. S., Henriksen, K., Mali, P. and Parvinen, M. (1996). Sequential expression of nucleoproteins during rat spermiogenesis. Exp. Cell Res. 225, 374-381.[Medline]
Le Douarin, B., Zechel, C., Garnier, J.-M., Lutz, Y., Tora, L., Pierrat, B., Heery, D., Gronemeyer, H., Chambon, P. and Losson, R. (1995). The N-terminal part of TIF1, a putative mediator of the ligand-dependent activation function (AF-2) of nuclear receptors, is fused to B-raf in the oncogenic protein T18. EMBO J. 14, 2020-2033.[Abstract]
Le Douarin, B., Nielsen, A. L., Garnier, J.-M., Ichinose, H., Jeanmougin, F., Losson, R. and Chambon, P. (1996). A possible involvement of TIF1 and TIF1ß in the epigenetic control of transcription by nuclear receptors. EMBO J. 15, 6701-6715.[Abstract]
Mark, M., Lufkin, T., Vonesch, J. L., Ruberte, E., Olivo, J. C., Dollé, P., Gorry, P., Lumsden, A. and Chambon, P. (1993). Two rhombomeres are altered in Hoxa-1 mutant mice. Development 119, 319-338.
Matsuda, E., Agata, Y., Sugai, M., Katakai, T., Gonda, H. and Shimizu, A. (2001). Targeting of Krüppel-associated box-containing zinc finger proteins to centromeric heterochromatin. Implication for the gene silencing mechanisms. J. Biol. Chem. 276, 14222-14229.
Meng, X., Lindahl, M., Hyvönen, M. E., Parvinen, M., de Rooij, D. G., Hess, M. W., Raatikainen-Ahokas, A., Sainio, K., Rauvala, H., Lakso, M. et al. (2000). Regulation of cell fate decision of undifferentiated spermatogonia by GDNF. Science 287, 1489-1493.
Metzger, D. and Chambon, P. (2001). Site- and time-specific gene targeting in the mouse. Methods 24, 71-80.[Medline]
Moosmann, P., Georgiev, O., Le Douarin, B., Bourquin, J.-P. and Schaffner, W. (1996). Transcriptional repression by RING finger protein TIF1ß that interacts with the KRAB repression domain of KOX1. Nucleic Acids Res. 24, 4859-4867.
Muller, C. and Leutz, A. (2001). Chromatin remodeling in development and differentiation. Curr. Opin. Genet. Dev. 11, 167-174.[Medline]
Nielsen, A. L., Ortiz, J. A., You, J., Oula-Abdelghani, M., Khechumian, R., Gansmuller, A., Chambon, P. and Losson, R. (1999). Interaction with members of the heterochromatin protein 1 (HP1) family and histone deacetylation are differentially involved in transcriptional silencing by members of the TIF1 family. EMBO J. 18, 6385-6395.
Oakberg, E. F. (1956a). Duration of spermatogenesis in the mouse and timing of stages of the cycle of the seminiferous epithelium. Am. J. Anat. 99, 507-516.
Oakberg, E. F. (1956b). A description of spermiogenesis in the mouse and its use in analysis of the cycle of the seminiferous epithelium and germ cell renewal. Am. J. Anat. 99, 391-414.
Oulad-Abdelghani, M., Bouillet, P., Chazaud, C., Dollé, P. and Chambon, P. (1996). AP-2.2: a novel AP-2-related transcription factor induced by retinoic acid during differentiation of P19 embryonal carcinoma cells. Exp. Cell Res. 225, 338-347.[Medline]
Pardue, M. L. and Gall, J. G. (1970). Chromosomal localization of mouse satellite DNA. Science 168, 1356-1358.[Medline]
Rachez, C. and Freedman, L. P. (2001). Mediator complexes and transcription. Curr. Opin. Cell Biol. 13, 274-280.[Medline]
Remboutsika, E., Lutz, Y., Gansmuller, A., Vonesch, J. L., Losson, R. and Chambon, P. (1999). The putative nuclear receptor mediator TIF1 is tightly associated with euchromatin. J. Cell Sci. 112, 1671-1683.
Russell, L. D., Hikim, A. P. S., Ettlin, R. A. and Clegg, E. D. (1990). Histological and Histopathological Evaluation of the Testis. Clearwater: Cache River Press.
Ryan, R. F., Schultz, D. C., Ayyanathan, K., Singh, P. B., Friedman, J. R., Fredericks, W. J. and Rauscher III, F. J. (1999). KAP-1 corepressor protein interacts and colocalizes with heterochromatic and euchromatic HP1 proteins: a potential role for Krüppel-associated box-zinc finger proteins in heterochromatin-mediated gene silencing. Mol. Cell. Biol. 19, 4366-4378.
Sassone-Corsi, P. (1997). Transcriptional checkpoints determining the fate of male germ cells. Cell 88, 163-166.[Medline]
Schultz, D. C., Friedman, J. R. and Rauscher, F. J., III (2001). Targeting histone deacetylase complexes via KRAB-zinc finger proteins: the PHD and bromodomains of KAP-1 form a cooperative unit that recruits a novel isoform of the Mi-2 subunit of NuRD. Genes Dev. 15, 428-443.
Sharpe R. (1993). Experimental evidence for Sertoli-germ cell and Sertoli-Leydig cell interactions. In The Sertoli Cell (ed. Russell and Griswold), pp. 391-418. Clearwater: Cache River Press.
Syed, V. and Hecht, N. B. (1997). Up-regulation and down-regulation of genes expressed in cocultures of rat Sertoli cells and germ cells. Mol. Reprod. Dev. 47, 380-389.[Medline]
Underhill, C., Qutob, M. S., Yee, S.-P. and Torchia, J. (2000). A novel nuclear receptor corepressor complex, N-CoR, contains components of the mammalian SWI/SNF complex and the corepressor KAP-1. J. Biol. Chem. 275, 40463-40470.
Venturini, L., You, J., Stadler, M., Galien, R., Lallemand, V., Koken, M. H. M., Mattei, M. G., Ganser, A., Chambon, P., Losson, R. and de Thé, H. (1999). TIF1, a novel member of the transcriptional intermediary factor 1 family. Oncogene 18, 1209-1217.[Medline]
Wright, W. W., Zabludoff, S. D., Penttilä, T. L and Parvinen, M. (1995). Germ cell-Sertoli cell interactions: regulation by germ cells of the stage-specific expression of CP-2/cathepsin L mRNA by Sertoli cells. Dev. Genet. 16, 104-113.[Medline]
Yomogida, K., Ohtani, H., Harigae, H., Ito, E., Nishimune, Y., Engel, J. D. and Yamamoto, M. (1994). Developmental stage- and spermatogenic cycle-specific expression of transcription factor GATA-1 in mouse Sertoli cells. Development 120, 1759-1766.
Zhao, G. Q., Deng, K., Labosky, P. A., Liaw, L. and Hogan, B. L. M. (1996). The gene encoding bone morphogenetic protein 8B is required for the initiation and maintenance of spermatogenesis in the mouse. Genes Dev. 10, 1657-1669.[Abstract]