Uterine defects and estradiol-dependent development of oviductal diverticula in mice lacking the SMAD4 C-terminal Mad homology 2 domain.

In female mammals, the oviduct and uterus are essential sites for female and male gamete transport, fertilization, implantation, and maintenance of a successful pregnancy. To delineate the reproductive function of Mothers against decapentaplegic homolog 4 (Smad4), we specifically inactivated Smad4 in ovarian granulosa cells and, oviduct and uterine mesenchymal cells using the Amhr2-cre mouse line. Deletion of exon 8 of Smad4 results in the production of an MH2-truncated SMAD4 protein. These mutant mice are infertile due to the development of oviductal diverticula and defects during the implantation process. The ovaries are fully functional as demonstrated in an ovary transfer experiment. The development of oviductal diverticula occurs shortly after puberty and is dependent on estradiol. The diverticula interfere with sperm migration and embryo transit to the uterus, reducing the number of implantation sites. Analysis of the uterus shows that, even if implantation occurs, decidualization and vascularization are defective resulting in embryo resorption as early as the seventh day of pregnancy. Thus, Smad4 plays an important function in female reproduction by controlling the structural and functional integrity of the oviduct and uterus.

Inactivation of Exosc10 in the oocyte impairs oocyte development and maturation, leading to a depletion of the ovarian reserve in mice.

EXOSC10 is a catalytic subunit of the nuclear RNA exosome, and possesses a 3'-5' exoribonuclease activity. The enzyme processes and degrades different classes of RNAs. To delineate the role of EXOSC10 during oocyte growth, specific Exosc10 inactivation was performed in oocytes from the primordial follicle stage onward using the Gdf9-iCre; Exosc10 f/- mouse model (Exosc10 cKO(Gdf9)). Exosc10 cKO(Gdf9) female mice are infertile. The onset of puberty and the estrus cycle in mutants are initially normal and ovaries contain all follicle classes. By the age of eight weeks, vaginal smears reveal irregular estrus cycles and mutant ovaries are completely depleted of follicles. Mutant oocytes retrieved from the oviduct are degenerated, and occasionally show an enlarged polar body, which may reflect a defective first meiotic division. Under fertilization conditions, the mutant oocytes do not enter into an embryonic development process. Furthermore, we conducted a comparative proteome analysis of wild type and Exosc10 knockout mouse ovaries, and identified EXOSC10-dependent proteins involved in many biological processes, such as meiotic cell cycle progression and oocyte maturation. Our results unambiguously demonstrate an essential role for EXOSC10 in oogenesis and may serve as a model for primary ovarian insufficiency in humans. Data are available via ProteomeXchange with identifier PXD039417.

A transgenic bacterial artificial chromosome approach to identify regulatory regions that direct Amhr2 and Osterix expression in Müllerian duct mesenchyme.

A transgenic mouse approach using bacterial artificial chromosomes (BAC) was used to identify regulatory regions that direct Müllerian duct expression for Amhr2 and Osterix (Osx, also known as Sp7). Amhr2 encodes the receptor that mediates anti-Müllerian hormone (AMH) signaling for Müllerian duct regression in male embryos. Amhr2 is expressed in the Müllerian duct mesenchyme of both male and female embryos. A ∼147-kb BAC clone containing the Amhr2 locus was used to generate transgenic mice. The transgene was able to rescue the block in Müllerian duct regression of Amhr2-null males, suggesting that the BAC clone contains regulatory sequences active in male embryos. Osx is expressed in the developing skeleton of male and female embryos but is also an AMH-induced gene that is expressed in the Müllerian duct mesenchyme exclusively in male embryos. Osx-Cre transgenic mice were previously generated using a ∼204-kb BAC clone. Crosses of Osx-Cre mice to Cre-dependent lacZ reporter mice resulted in reporter expression in the developing skeleton and in the Müllerian duct mesenchyme of male but not female embryos. Osx-Cherry transgenic mice were previously generated using a 39-kb genomic region surrounding the Osx locus. Osx-Cherry embryos expressed red fluorescence in the developing skeleton and Müllerian duct mesenchyme of male but not female embryos. In addition, female Osx-Cherry embryos ectopically expressing human AMH from an Mt1-AMH transgene activated red fluorescence in the Müllerian duct mesenchyme. These results suggest that the 39-kb region used to generate Osx-Cherry contains male-specific Müllerian duct mesenchyme regulatory sequences that are responsive to AMH signaling. These BAC transgenic mouse approaches identify two distinct regions that direct Müllerian duct mesenchyme expression and contribute fundamental knowledge to define a gene regulatory network for sex differentiation.

EXOSC10/Rrp6 is essential for the eight-cell embryo/morula transition.

The conserved 3'-5' exoribonuclease EXOSC10/Rrp6 is required for gametogenesis, brain development, erythropoiesis and blood cell enhancer function. The human ortholog is essential for mitosis in cultured cancer cells. Little is known, however, about the role of Exosc10 during embryo development and organogenesis. We generated an Exosc10 knockout model and find that Exosc10-/- mice show an embryonic lethal phenotype. We demonstrate that Exosc10 maternal wild type mRNA is present in mutant oocytes and that the gene is expressed during all stages of early embryogenesis. Furthermore, we observe that EXOSC10 early on localizes to the periphery of nucleolus precursor bodies in blastomeres, which is in keeping with the protein's role in rRNA processing and may indicate a function in the establishment of chromatin domains during initial stages of embryogenesis. Finally, we infer from genotyping data for embryonic days e7.5, e6.5 and e4.5 and embryos cultured in vitro that Exosc10-/- mutants arrest at the eight-cell embryo/morula transition. Our results demonstrate a novel essential role for Exosc10 during early embryogenesis, and they are consistent with earlier work showing that impaired ribosome biogenesis causes a developmental arrest at the morula stage.

Combined RNA/tissue profiling identifies novel Cancer/testis genes.

Cancer/Testis (CT) genes are induced in germ cells, repressed in somatic cells, and derepressed in somatic tumors, where these genes can contribute to cancer progression. CT gene identification requires data obtained using standardized protocols and technologies. This is a challenge because data for germ cells, gonads, normal somatic tissues, and a wide range of cancer samples stem from multiple sources and were generated over substantial periods of time. We carried out a GeneChip-based RNA profiling analysis using our own data for testis and enriched germ cells, data for somatic cancers from the Expression Project for Oncology, and data for normal somatic tissues from the Gene Omnibus Repository. We identified 478 candidate loci that include known CT genes, numerous genes associated with oncogenic processes, and novel candidates that are not referenced in the Cancer/Testis Database (www.cta.lncc.br). We complemented RNA expression data at the protein level for SPESP1, GALNTL5, PDCL2, and C11orf42 using cancer tissue microarrays covering malignant tumors of breast, uterus, thyroid, and kidney, as well as published RNA profiling and immunohistochemical data provided by the Human Protein Atlas (www.proteinatlas.org). We report that combined RNA/tissue profiling identifies novel CT genes that may be of clinical interest as therapeutical targets or biomarkers. Our findings also highlight the challenges of detecting truly germ cell-specific mRNAs and the proteins they encode in highly heterogenous testicular, somatic, and tumor tissues.

EXOSC10/Rrp6 is post-translationally regulated in male germ cells and controls the onset of spermatogenesis.

EXOSC10 is a catalytic subunit of the exosome that processes biologically active transcripts, degrades aberrant mRNAs and targets certain long non-coding RNAs (lncRNAs). The yeast orthologue Rrp6 is required for efficient growth and gametogenesis, and becomes unstable during meiosis. However, nothing is known about the localization, stability and function of EXOSC10 in the rodent male germline. We detect the protein in nucleoli and the cytoplasm of mitotic and meiotic germ cells, and find that it transiently associates with the XY body, a structure targeted by meiotic sex chromosome inactivation (MSCI). Finally, EXOSC10 becomes unstable at later stages of gamete development. To determine Exosc10's meiotic function, we inactivated the gene specifically in male germ cells using cre recombinase controlled by Stra8 or Ddx4/Vasa promoters. Mutant mice have small testes, show impaired germ cell differentiation and are subfertile. Our results demonstrate that EXOSC10 is post-translationally regulated in germ cells, associate the protein with epigenetic chromosome silencing, and reveal its essential role in germ cell growth and development.

Partial Müllerian Duct Retention in Smad4 Conditional Mutant Male Mice.

Müllerian duct regression is a complex process which involves the AMH signalling pathway. We have previously demonstrated that besides AMH and its specific type II receptor (AMHRII), BMPR-IA and Smad5 are two essential factors implicated in this mechanism. Mothers against decapentaplegic homolog 4 (Smad4) is a transcription factor and the common Smad (co-Smad) involved in transforming growth factor beta (TGF-ß) signalling pathway superfamily. Since Smad4 null mutants die early during gastrulation, we have inactivated Smad4 in the Müllerian duct mesenchyme. Specific inactivation of Smad4 in the urogenital ridge leads to the partial persistence of the Müllerian duct in adult male mice. Careful examination of the urogenital tract reveals that the Müllerian duct retention is randomly distributed either on one side or both sides. Histological analysis shows a uterus-like structure, which is confirmed by the expression of estrogen receptor α. As previously described in a ß-catenin conditional mutant mouse model, ß-catenin contributes to Müllerian duct regression. In our mutant male embryos, it appears that ß-catenin expression is locally reduced along the urogenital ridge as compared to control mice. Moreover, the expression pattern is similar to those observed in control female mice. This study shows that reduced Smad4 expression disrupts the Wnt/ß-catenin signalling leading to the partial persistence of Müllerian duct.

Novel role for anti-Müllerian hormone in the regulation of GnRH neuron excitability and hormone secretion.

Anti-Müllerian hormone (AMH) plays crucial roles in sexual differentiation and gonadal functions. However, the possible extragonadal effects of AMH on the hypothalamic-pituitary-gonadal axis remain unexplored. Here we demonstrate that a significant subset of GnRH neurons both in mice and humans express the AMH receptor, and that AMH potently activates the GnRH neuron firing in mice. Combining in vivo and in vitro experiments, we show that AMH increases GnRH-dependent LH pulsatility and secretion, supporting a central action of AMH on GnRH neurons. Increased LH pulsatility is an important pathophysiological feature in many cases of polycystic ovary syndrome (PCOS), the most common cause of female infertility, in which circulating AMH levels are also often elevated. However, the origin of this dysregulation remains unknown. Our findings raise the intriguing hypothesis that AMH-dependent regulation of GnRH release could be involved in the pathophysiology of fertility and could hold therapeutic potential for treating PCOS.

The BOC ELISA, a ruminant-specific AMH immunoassay, improves the determination of plasma AMH concentration and its correlation with embryo production in cattle.

Plasma anti-Müllerian hormone (AMH) concentrations have been recently found to be predictive of the number of embryos recovered after FSH superovulatory treatment in the cow. However, the sensitivity of the Active Müllerian-inhibiting substance/AMH ELISA (ref. 10-14400; DSL-Beckman-Coulter) used to make these measurements in bovine plasma samples is low because it was developed to measure human AMH levels. To overcome this limitation, we developed an immunoassay specific for the bovine (B), ovine (O), and caprine (C) species, the bovine-ovine-caprine (BOC) ELISA. For this purpose, we produced recombinant bovine AMH for standardization, and we used monoclonal antibodies raised against bovine AMH, previously prepared by our laboratory. We evaluated the precision, accuracy, specificity, limit of detection, and functional sensitivity of the assay. The intra-assay coefficient of variation ranged between 3.4% and 11.3% for AMH concentrations between 23.68 and 1.74 ng/mL, and the interassay coefficient of variation ranged between 4.8% and 20.5% for concentrations between 25.53 and 1.42 ng/mL, respectively. The assay displayed a good linearity, had a detection limit of 0.4 ng/mL and a functional sensitivity of 1.4 ng/mL. It also cross-reacted with ovine and caprine AMHs. Both the mean and median AMH levels measured in 40 cow plasma samples using the BOC ELISA were approximately 44 fold higher than the mean and median AMH levels measured with the Active Müllerian-inhibiting substance/AMH ELISA. Moreover, a higher correlation was observed between the average number of embryos recovered from each cow after superovulatory treatment and AMH concentrations measured with the BOC ELISA. This BOC ELISA provides a very efficient tool for evaluating the ovarian follicular reserve of cows and predicting their embryo production capacity.

Combining RNA and protein profiling data with network interactions identifies genes associated with spermatogenesis in mouse and human.

Genome-wide RNA profiling studies have identified hundreds of transcripts that are highly expressed in mammalian male germ cells, including many that are undetectable in somatic control tissues. Among them, genes important for spermatogenesis are significantly enriched. Information about mRNAs and their cognate proteins facilitates the identification of novel conserved target genes for functional studies in the mouse. By inspecting genome-wide RNA profiling data, we manually selected 81 genes for which RNA is detected almost exclusively in the human male germline and, in most cases, in rodent testicular germ cells. We observed corresponding mRNA/protein patterns in 43 cases using immunohistochemical data from the Human Protein Atlas and large-scale human protein profiling data obtained via mass spectroscopy. Protein network information enabled us to establish an interaction map of 38 proteins that points to potentially important testicular roles for some of them. We further characterized six candidate genes at the protein level in the mouse. We conclude that conserved genes induced in testis tend to show similar mRNA/protein expression patterns across species. Specifically, our results suggest roles during embryogenesis and adult spermatogenesis for Foxr1 and Sox30 and during spermiogenesis and fertility for Fam71b, 1700019N19Rik, Hmgb4, and Zfp597.

Anti-Müllerian hormone recruits BMPR-IA in immature granulosa cells.

Anti-Müllerian hormone (AMH) is a member of the TGF-ß superfamily secreted by the gonads of both sexes. This hormone is primarily known for its role in the regression of the Müllerian ducts in male fetuses. In females, AMH is expressed in granulosa cells of developing follicles. Like other members of the TGF-ß superfamily, AMH transduces its signal through two transmembrane serine/threonine kinase receptors including a well characterized type II receptor, AMHR-II. The complete signalling pathway of AMH involving Smads proteins and the type I receptor is well known in the Müllerian duct and in Sertoli and Leydig cells but not in granulosa cells. In addition, few AMH target genes have been identified in these cells. Finally, while several co-receptors have been reported for members of the TGF-ß superfamily, none have been described for AMH. Here, we have shown that none of the Bone Morphogenetic Proteins (BMPs) co-receptors, Repulsive guidance molecules (RGMs), were essential for AMH signalling. We also demonstrated that the main Smad proteins used by AMH in granulosa cells were Smad 1 and Smad 5. Like for the other AMH target cells, the most important type I receptor for AMH in these cells was BMPR-IA. Finally, we have identified a new AMH target gene, Id3, which could be involved in the effects of AMH on the differentiation of granulosa cells and its other target cells.

ß-Catenin is essential for Müllerian duct regression during male sexual differentiation.

During male sexual differentiation, the transforming growth factor-ß (TGF-ß) signaling molecule anti-Müllerian hormone (AMH; also known as Müllerian inhibiting substance, MIS) is secreted by the fetal testes and induces regression of the Müllerian ducts, the primordia of the female reproductive tract organs. Currently, the molecular identity of downstream events regulated by the AMH signaling pathway remains unclear. We found that male-specific Wnt4 expression in mouse Müllerian duct mesenchyme depends upon AMH signaling, implicating the WNT pathway as a downstream mediator of Müllerian duct regression. Inactivation of ß-catenin, a mediator of the canonical WNT pathway, did not affect AMH signaling activation in the Müllerian duct mesenchyme, but did block Müllerian duct regression. These data suggest that ß-catenin mediates AMH signaling for Müllerian duct regression during male sexual differentiation.

Processing of anti-mullerian hormone regulates receptor activation by a mechanism distinct from TGF-beta.

TGF-ß family ligands are translated as prepropeptide precursors and are processed into mature C-terminal dimers that signal by assembling a serine/threonine kinase receptor complex containing type I and II components. Many TGF-ß ligands are secreted in a latent form that cannot bind their receptor, due to the pro-region remaining associated with the mature ligand in a noncovalent complex after proteolytic cleavage. Here we show that anti-Müllerian hormone (AMH), a TGF-ß family ligand involved in reproductive development, must be cleaved to bind its type II receptor (AMHRII), but dissociation of the pro-region from the mature C-terminal dimer is not required for this initial interaction. We provide direct evidence for this interaction by showing that the noncovalent complex binds to a soluble form of AMHRII in an ELISA format and to AMHRII immobilized on Sepharose. Binding of the noncovalent complex to Sepharose-coupled AMHRII induces dissociation of the pro-region from the mature C-terminal dimer, whereas no dissociation occurs after binding to immobilized AMH antibodies. The pro-region cannot be detected after binding of the AMH noncovalent complex to AMHRII expressed on COS cells, indicating that pro-region dissociation may occur as a natural consequence of receptor engagement on cells. Moreover, the mature C-terminal dimer is more active than the noncovalent complex in stimulating Sma- and Mad-related protein activation, suggesting that pro-region dissociation contributes to the assembly of the active receptor complex. AMH thus exemplifies a new mechanism for receptor engagement in which interaction with the type II receptor promotes pro-region dissociation to generate mature ligand.

Anti-Mullerian-hormone-dependent regulation of the brain serine-protease inhibitor neuroserpin.

The balance between tissue-type plasminogen activator (tPA) and one of its inhibitors, neuroserpin, has crucial roles in the central nervous system, including the control of neuronal migration, neuronal plasticity and neuronal death. In the present study, we demonstrate that the activation of the transforming growth factor-beta (TGFbeta)-related BMPR-IB (also known as BMPR1B and Alk6)- and Smad5-dependent signalling pathways controls neuroserpin transcription. Accordingly, we demonstrate for the first time that anti-Mullerian hormone (AMH), a member of the TGFbeta family, promotes the expression of neuroserpin in cultured neurons but not in astrocytes. The relevance of these findings is confirmed by the presence of both AMH and AMH type-II receptor (AMHR-II) in brain tissues, and is supported by the observation of reduced levels of neuroserpin in the brain of AMHR-II-deficient mice. Interestingly, as previously demonstrated for neuroserpin, AMH protects neurons against N-methyl-D-aspartate (NMDA)-mediated excitotoxicity both in vitro and in vivo. This study demonstrates the existence of an AMH-dependent signalling pathway in the brain leading to an overexpression of the serine-protease inhibitor, neuroserpin, and neuronal survival.

Anti-Mullerian hormone, its receptor, FSH receptor, and androgen receptor genes are overexpressed by granulosa cells from stimulated follicles in women with polycystic ovary syndrome.

CONTEXT: In the polycystic ovary syndrome (PCOS), in addition to intrinsic thecal dysregulation leading to hyperandrogenism, a granulosa cell (GC) dysregulation may occur. Expression of anti-Müllerian hormone (AMH), FSH receptor (FSHR) and androgen receptor (AR) are suspected to be altered in PCOS GCs. DESIGN: The aim of this prospective study was to analyze the expression of these genes at the last stages of follicular maturation in GCs from 17 patients with PCOS and 15 controls undergoing controlled ovarian hyperstimulation during a cycle with in vitro fertilization. MATERIALS AND METHODS: On the day of oocyte retrieval, follicular fluids were collected from small follicles (SF; 8-13 mm) and large follicles (17-22 mm) in separate tubes. Total RNAs and proteins were extracted from GCs. Reverse transcription was performed and quantification of gene expression levels was achieved by real-time quantitative PCR. RESULTS: AMH and FSHR mRNA levels were significantly higher in PCOS than in controls in GCs from both SF and large follicles. Likewise, AR and AMH receptor II mRNA levels in GCs from SF were significantly higher in PCOS compared with controls. In both PCOS patients and controls, AMH and AR mRNA levels correlated strongly, positively, and independently to FSHR mRNA levels. CONCLUSION: Using quantitative RT-PCR, AMH, AMH receptor II, FSHR, and AR genes were shown to be overexpressed by GCs from stimulated follicles of women with PCOS undergoing controlled ovarian hyperstimulation. This could be the sign of a maturation defect or may reflect hyperandrogenism.

Synergistic effects of Pten loss and WNT/CTNNB1 signaling pathway activation in ovarian granulosa cell tumor development and progression.

The mechanisms of granulosa cell tumor (GCT) development may involve the dysregulation of signaling pathways downstream of follicle-stimulating hormone, including the phosphoinosite-3 kinase (PI3K)/AKT pathway. To test this hypothesis, a genetically engineered mouse model was created to derepress the PI3K/AKT pathway in granulosa cells by conditional targeting of the PI3K antagonist gene Pten (Pten(flox/flox);Amhr2(cre/+)). The majority of Pten(flox/flox);Amhr2(cre/+) mice featured no ovarian anomalies, but occasionally ( approximately 7%) developed aggressive, anaplastic GCT with pulmonary metastases. The expression of the PI3K/AKT downstream effector FOXO1 was abrogated in Pten(flox/flox);Amhr2(cre/+) GCT, indicating a mechanism by which GCT cells may increase proliferation and evade apoptosis. To relate these findings to spontaneously occurring GCT, analyses of PTEN and phospho-AKT expression were performed on human and equine tumors. Although PTEN loss was not detected, many GCT (2/5 human, 7/17 equine) featured abnormal nuclear or perinuclear localization of phospho-AKT, suggestive of altered PI3K/AKT activity. As inappropriate activation of WNT/CTNNB1 signaling causes late-onset GCT development and cross talk between the PI3K/AKT and WNT/CTNNB1 pathways has been reported, we tested whether these pathways could synergize in GCT. Activation of both the PI3K/AKT and WNT/CTNNB1 pathways in the granulosa cells of a mouse model (Pten(flox/flox);Ctnnb1(flox(ex3)/+);Amhr2(cre/+)) resulted in the development of GCT similar to those observed in Pten(flox/flox);Amhr2(cre/+) mice, but with 100% penetrance, perinatal onset, extremely rapid growth and the ability to spread by seeding into the abdominal cavity. These data indicate a synergistic effect of dysregulated PI3K/AKT and WNT/CTNNB1 signaling in the development and progression of GCT and provide the first animal models for metastatic GCT.

A mesenchymal perspective of Müllerian duct differentiation and regression in Amhr2-lacZ mice.

The Müllerian ducts give rise to the female reproductive tract, including the Fallopian tubes, uterus, cervix, and anterior vagina. In male embryos, the Müllerian ducts regress, preventing the formation of female organs. We introduced the bacterial lacZ gene, encoding beta-galactosidase (beta-gal), into the AMHR-II locus (Amhr2) by gene targeting in mouse embryonic stem (ES) cells to mark Müllerian duct differentiation and regression. We show that Amhr2-lacZ heterozygotes express beta-gal activity in an Amhr2-specific pattern. In the gonads, beta-gal activity was detected in Sertoli cells of the testes from 2 weeks after birth, and fetal ovaries and granulosa cells of the adult ovary. beta-gal activity was first detected in the rostral mesenchyme of the Müllerian ducts at 12.5 days post coitus (dpc) in both sexes but soon thereafter expression was found along the entire length of the Müllerian ducts with higher levels initially found in males. In females, beta-gal activity was restricted to one side of the ductal mesoepithelium, whereas in males beta-gal expression encircled the duct. beta-gal activity was also detected in the coelomic epithelium at 13.5 and 14.5 dpc. In male embryos, mesenchymal beta-gal activity permitted the visualization of the temporal and spatial pattern of Müllerian duct regression. This pattern was similar to that observed using a Müllerian duct mesoepithelium lacZ reporter, indicating a coordinated loss of Müllerian duct mesoepithelium and Amhr2-expressing mesenchyme.

Conditional deletion of Smad1 and Smad5 in somatic cells of male and female gonads leads to metastatic tumor development in mice.

The transforming growth factor beta (TGFbeta) family has critical roles in the regulation of fertility. In addition, the pathogenesis of some human cancers is attributed to misregulation of TGFbeta function and SMAD2 or SMAD4 mutations. There are limited mouse models for the BMP signaling SMADs (BR-SMADs) 1, 5, and 8 because of embryonic lethality and suspected genetic redundancy. Using tissue-specific ablation in mice, we deleted the BR-SMADs from somatic cells of ovaries and testes. Single conditional knockouts for Smad1 or Smad5 or mice homozygous null for Smad8 are viable and fertile. Female double Smad1 Smad5 and triple Smad1 Smad5 Smad8 conditional knockout mice become infertile and develop metastatic granulosa cell tumors. Male double Smad1 Smad5 conditional knockout mice are fertile but demonstrate metastatic testicular tumor development. Microarray analysis indicated significant alterations in expression of genes related to the TGFbeta pathway, as well as genes involved in infertility and extracellular matrix production. These data strongly implicate the BR-SMADs as part of a critical developmental pathway in ovaries and testis that, when disrupted, leads to malignant transformation.

Deletion of the orphan nuclear receptor COUP-TFII in uterus leads to placental deficiency.

COUP-TFII (NR2F2), chicken ovalbumin upstream promoter-transcription factor II, is an orphan nuclear receptor of the steroid/thyroid hormone receptor superfamily. The Coup-tfII-null mutant mice die during the early embryonic development because of angiogenesis and heart defects. To analyze the physiological function of COUP-TFII during organogenesis, we used the cre/loxP system to conditionally inactivate COUP-TFII in the ovary and uterus. Homozygous adult female mutants with specific inactivation of the Coup-tfII gene in uterine stromal and smooth muscle cells have severely impaired placental formation, leading to miscarriage at days 10-12 of pregnancy. Deletion of the Coup-tfII gene resulted in an increase in trophoblast giant cell differentiation, a reduction of the spongiotrophoblast layer, and an absence of labyrinth formation causing an improper vascularization of the placenta. This study describes an important maternal role of COUP-TFII in regulating the placentation. The endometrial COUP-TFII might modulate the signaling between the uterus and the extraembryonic tissue for the proper formation of the placenta.