Lats1 and Lats2 regulate YAP and TAZ activity to control the development of mouse Sertoli cells

Recent reports suggest that the Hippo signaling pathway regulates testis development, though its exact roles in Sertoli cell differentiation remain unknown. Here, we examined the functions of the main Hippo pathway kinases, large tumor suppressor homolog kinases 1 and 2 (Lats1 and Lats2) in developing mouse Sertoli cells. Conditional inactivation of Lats1/2 in Sertoli cells resulted in the disorganization and overgrowth of the testis cords, the induction of a testicular inflammatory response and germ cell apoptosis. Stimulated by retinoic acid 8 (STRA8) expression in germ cells additionally suggested that germ cells may have been preparing to enter meiosis prior to their loss. Gene expression analyses of the developing testes of conditional knockout animals further suggested impaired Sertoli cell differentiation, epithelial-to-mesenchymal transition, and the induction of a specific set of genes associated with Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ)-mediated integrin signaling. Finally, the involvement of YAP/TAZ in Sertoli cell differentiation was confirmed by concomitantly inactivating Yap/Taz in Lats1/2 conditional knockout model, which resulted in a partial rescue of the testicular phenotypic changes. Taken together, these results identify Hippo signaling as a crucial pathway for Sertoli cell development and provide novel insight into Sertoli cell fate maintenance.

Therapeutic trial of fluvastatin in a cell line xenograft model of canine mammary gland cancer

The Hippo signalling pathway is involved in breast cancer and canine mammary tumour (CMT). This study sought to evaluate the efficacy of fluvastatin on the Hippo pathway and its main effectors, YAP and TAZ, in vivo in a murine CMT cell line xenograft model. On treatment day 1, mice were divided into four groups: vehicle, fluvastatin, doxorubicin or a combination therapy. Tumour volumes were monitored with callipers and tissues harvested on day 28th of treatment. Histopathological examination of tumour tissues and major organs was performed as well as tumour evaluation of necrosis, apoptosis, cellular proliferation, expression of YAP, TAZ and the mRNA levels of four of their target genes (CTGF, CYR61, ANKRD1 and RHAMM2). Results showed a statistically significant variation in tumour volumes only for the combination therapy and final tumour weight only for the doxorubicin group compared to control. There was no significant difference in tumour necrosis, expression of CC3, ki-67, YAP and TAZ measured by immunohistochemistry and in the mRNA levels of the target genes. Unexpectedly, lung metastases were found in the control group (9) and not in the fluvastatin treated group (7). In addition, mass spectrometry-based quantification of fluvastatin reveals concentrations comparable to levels reported to exert therapeutic effects. This study shows that fluvastatin tumours concentration reached therapeutic levels without having an effect on the hippo pathway or various tumour parameters. Interestingly, only the control group had lung metastases. This study is the first to explore the repurposing of statins for cancer treatment in veterinary medicine.

Redundant roles of AKT1 and AKT2 in fertility, estrous cyclicity and endometrial gland development

Apoptosis and cell survival regulation are crucial processes during the estrous cycle to prepare a receptive uterus during implantation for successful recognition of pregnancy. PI3K/AKT signaling has a crucial role during gestation and AKT isoforms (1, 2 or 3) are regulated differently in the endometrium during the estrous cycle and embryo implantation. However, the specific roles of these isoforms are still unclear. We have previously shown that AKT isoforms expression during the rat estrous cycle and gestation are differently regulated. The present study aimed to establish the specific role of AKT isoforms in the mouse uterus. The hypothesis is that a dysregulation of AKT isoforms expression could cause fertility-related issues in an isoform-specific manner. With four different mouse models and in-house crossbreeding, all isoforms KO combinations (single, double and triple) were obtained in PGR expressing tissues. The results demonstrated that in absence of one or more AKT isoforms, female fertility was decreased. Mainly, we have observed smaller litter size, specifically in Akt1-2 KO mice. Additionally, we have found Akt1-2-3 KO mice to be fully infertile. Estrous cyclicity was also disrupted in Akt1-2 KO mice with longer diestrus stage. Moreover, the number of endometrial glands was decreased throughout the estrous cycle suggesting an important role in gland development for AKT1 and AKT2. Our results suggest specific roles between each isoform, but also a partially redundant function of AKT1 and AKT2 in litter size, estrous cyclicity and endometrial gland development. This highlights the importance of AKT in the physiological regulation of mouse fertility.

Effect of inactivation of Mst1 and Mst2 in the mouse adrenal cortex

Recent conditional knockout of core components of the Hippo signaling pathway in the adrenal gland of mice has demonstrated that this pathway must be tightly regulated to ensure proper development and maintenance of the adrenal cortex. We report herein that the most upstream kinases of the pathway, the mammalian STE20-like protein kinases 1 and 2 (MST1and MST2, respectively), are expressed in the mouse adrenal cortex with MST2 expression being restricted to the zona glomerulosa (zG). To further explore the role of Hippo signaling in adrenocortical cells, we conditionally deleted Mst1/2 in steroidogenic cells using an Nr5a1-cre strain (Mst1flox/flox; Mst2flox/flox; Nr5a1-cre). Our results show that the loss of MST1/2 leads to the premature and progressive accumulation of subcapsular GATA4+, WT1 + adrenal gonadal primordium (AGP)-like progenitor cells starting at 2 months of age without affecting aldosterone and corticosterone secretion. To help us understand this phenotype, microarray analyses were performed on adrenal glands from 2-month-old mutant and control mice. Gene expression analyses revealed that loss of Mst1/2 leads to the overexpression of known downstream target genes (Ajuba, Aqp1, Fn1, Ibsp, Igf1, Igfbp2, Mmp2, Thbs1) of the main effector of Hippo signaling, YAP; and underexpression of genes (Agtr1b, Ecgr4, Hsd3b6, Nr0b1, Tesc, Vsnl1) that are normally specifically expressed in the zG or overexpressed in the zG compared to the zona fasciculata (zF). Together, these results suggest that MST1/2 regulates Hippo signaling activity in the adrenal cortex and that these two kinases are also involved in the fine tuning of zG cell function or differentiation.

The granulosa cell response to luteinizing hormone is partly mediated by YAP1-dependent induction of amphiregulin

Background

The LH surge is a pivotal event that triggers multiple key ovarian processes including oocyte maturation, cumulus expansion, follicular wall rupture and luteinization of mural granulosa and theca cells. Recently, LH-dependent activation of the Hippo signaling pathway has been shown to be required for the differentiation of granulosa cells into luteal cells. Still, the precise interactions between Hippo and LH signaling in murine granulosa cells remain to be elucidated.

Methods

To detect the expression of effectors of the Hippo pathway, western blot, immunohistochemical and RT-qPCR analyses were performed on granulosa cells treated with LH in vitro or isolated from immature mice treated with eCG and hCG. Cultured granulosa cells were pretreated with pharmacologic inhibitors to identify the signaling pathways involved in Hippo regulation by LH. To study the roles of Yap1 and Taz in the regulation of the LH signaling cascade, RT-qPCR and microarray analyses were done on granulosa cells from Yap1^f/f;Taz^f/f mice treated with an adenovirus to drive cre expression. RT-qPCR was performed to evaluate YAP1 binding to the Areg promoter following chromatin immunoprecipitation of granulosa cells collected from mice prior to or 60 min following hCG treatment.

Results

Granulosa cells showed a transient increase in LATS1, YAP1 and TAZ phosphorylation levels in response to the ovulatory signal. This Hippo activation by LH was mediated by protein kinase A. Furthermore, Yap1 and Taz are required for the induction of several LH target genes such as Areg, Pgr and Ptgs2, and for the activation of the ERK1/2 pathway. Consistent with these results, there was a substantial overlap between genes that are upregulated by LH and those that are downregulated following loss of Yap1/Taz, highlighting a major role for Hippo in mediating LH actions in the ovulation process. Finally, we showed that there is a marked recruitment of YAP1 to the Areg promoter of granulosa cells in response to hCG stimulation.

Conclusions

Overall, these results indicate that Hippo collaborates with the cAMP/PKA and ERK1/2 pathways to participate in the precise regulation of the LH cascade, and that Areg, as a direct transcriptional target of YAP1, is involved in mediating its actions in the ovary.

The Hippo Pathway Effectors YAP and TAZ Regulate LH Release by Pituitary Gonadotrope Cells in Mice

The Hippo transcriptional coactivators YAP and TAZ exert critical roles in morphogenesis, organ size determination and tumorigenesis in many tissues. Although Hippo kinase cascade activity was recently reported in the anterior pituitary gland in mice, the role of the Hippo effectors in regulating gonadotropin production remains unknown. The objective of this study was therefore to characterize the roles of YAP and TAZ in gonadotropin synthesis and secretion. Using a conditional gene targeting approach (cKO), we found that gonadotrope-specific inactivation of Yap and Taz resulted in increased circulating levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in adult male mice, along with increased testosterone levels and testis weight. Female cKO mice had increased circulating LH (but not FSH) levels, which were associated with a hyperfertility phenotype characterized by higher ovulation rates and larger litter sizes. Unexpectedly, the loss of YAP/TAZ did not appear to affect the expression of gonadotropin subunit genes, yet both basal and GnRH-induced LH secretion were increased in cultured pituitary cells from cKO mice. Likewise, pharmacologic inhibition of YAP binding to the TEAD family of transcription factors increased both basal and GnRH-induced LH secretion in LβT2 gonadotrope-like cells in vitro without affecting Lhb expression. Conversely, mRNA levels of ChgA and SgII, which encode key secretory granule cargo proteins, were decreased following pharmacologic inhibition of YAP/TAZ, suggesting a mechanism whereby YAP/TAZ regulate the LH secretion machinery in gonadotrope cells. Together, these findings represent the first evidence that Hippo signaling may play a role in regulating pituitary LH secretion.

Addition of a carboxy terminal tail to the normally tailless gonadotropin-releasing hormone receptor impairs fertility in female mice

Gonadotropin-releasing hormone (GnRH) is the primary neuropeptide controlling reproduction in vertebrates. GnRH stimulates follicle-stimulating hormone (FSH) and luteinizing hormone (LH) synthesis via a G-protein-coupled receptor, GnRHR, in the pituitary gland. In mammals, GnRHR lacks a C-terminal cytosolic tail (Ctail) and does not exhibit homologous desensitization. This might be an evolutionary adaptation that enables LH surge generation and ovulation. To test this idea, we fused the chicken GnRHR Ctail to the endogenous murine GnRHR in a transgenic model. The LH surge was blunted, but not blocked in these mice. In contrast, they showed reductions in FSH production, ovarian follicle development, and fertility. Addition of the Ctail altered the nature of agonist-induced calcium signaling required for normal FSH production. The loss of the GnRHR Ctail during mammalian evolution is unlikely to have conferred a selective advantage by enabling the LH surge. The adaptive significance of this specialization remains to be determined.

Statins downregulate YAP and TAZ and exert anti-cancer effects in canine mammary tumour cells

Canine mammary tumours (CMTs) are the most common neoplasms in intact bitches, and few chemotherapeutic options are available for highly invasive and metastatic tumours. Recent studies have shown the potential involvement of dysregulated Hippo signalling in CMT development and progression. Statins can activate the Hippo pathway by blocking protein geranylgeranylation (GGylation), resulting in decreased expression and activity of the transcriptional co-activators YAP and TAZ. In this study, we therefore sought to determine if statins could exert anti-cancer effects in CMT cells. Our results demonstrate that Atorvastatin and Fluvastatin are cytotoxic to two CMT cell lines (CMT9 and CMT47), with ED50 values ranging from 0.95 to 23.5 μM. Both statins acted to increase apoptosis and promote cell cycle arrest. Both statins also decreased YAP and TAZ expression and reduced the mRNA levels of key Hippo transcriptional target genes known to be involved in breast cancer progression and chemoresistance (CYR61, CTGF and RHAMM). Moreover, both statins effectively inhibited cell migration and anchorage independent growth, but did not influence matrix invasion. Taken together, our results demonstrate for the first time that statins act upon the Hippo pathway in CMT cells to counteract several molecular and cellular hallmarks of cancer. These findings suggest that targeting the Hippo pathway with statins represents a novel and promising approach for the treatment canine mammary gland cancers.

YAP and TAZ are required for the postnatal development and the maintenance of the structural integrity of the oviduct

The development of the Müllerian ducts into the female reproductive tract requires the coordination of multiple signaling pathways that regulate proliferation, apoptosis and differentiation. The Hippo pathway has been reported to interact with several pathways with established roles in Müllerian duct development; yet, its potential roles in reproductive tract development and function remain mostly uncharacterized. The objective of this study was therefore to characterize the roles of the Hippo transcriptional coactivators YAP and TAZ in the female reproductive tract using transgenic mouse models. This report shows that the concomitant conditional inactivation of Yap and Taz in the mouse Müllerian duct mesenchyme results in postnatal developmental defects of the oviduct. Most notably, discontinuities in the myosalpinx layer lead to the progressive formation of cystic dilations of the isthmus. These defects prevented embryo transport and subsequent implantation in older animals, causing infertility. The loss of YAP/TAZ did not appear to affect other biological processes known to be required for the maintenance of oviductal wall integrity, such as TGF-β/SMAD and Notch signaling and the biogenesis of miRNA, suggesting that the Hippo pathway acts independently of these processes to direct oviduct development. Taken together, these results suggest redundant and essential roles for YAP and TAZ in the postnatal development of the oviduct and the maintenance of its structural integrity.

Constitutive activation of CTNNB1 results in a loss of spermatogonial stem cell activity in mice

Spermatogenesis requires that a careful balance be maintained between the self-renewal of spermatogonial stem cells (SSCs) and their commitment to the developmental pathway through which they will differentiate into spermatozoa. Recently, a series of studies employing various in vivo and in vitro models have suggested a role of the wingless-related MMTV integration site gene family/beta-catenin (WNT/CTNNB1) pathway in determining the fate of SSCs. However, conflicting data have suggested that CTNNB1 signaling may either promote SSC self-renewal or differentiation. Here, we studied the effects of sustained CTNNB1 signaling in SSCs using the Ctnnb1^tm1Mmt/+; Ddx4-Cre^Tr/+ (ΔCtnnb1) mouse model, in which a stabilized form of CTNNB1 is expressed in all germ cells. ΔCtnnb1 mice were found to have reduced testis weights and partial germ cell loss by 4 months of age. Germ cell transplantation assays showed a 49% reduction in total functional SSC numbers in 8 month-old transgenic mice. In vitro, Thy1-positive undifferentiated spermatogonia from ΔCtnnb1 mice formed 57% fewer clusters, which was associated with decreased cell proliferation. A reduction in mRNA levels of genes associated with SSC maintenance (Bcl6b, Gfra1, Plzf) and increased levels for markers associated with progenitor and differentiating spermatogonia (Kit, Rarg, Sohlh1) were detected in these cluster cells. Furthermore, RNAseq performed on these clusters revealed a network of more than 900 genes regulated by CTNNB1, indicating that CTNNB1 is an important regulator of spermatogonial fate. Together, our data support the notion that CTNNB1 signaling promotes the transition of SSCs to undifferentiated progenitor spermatogonia at the expense of their self-renewal.

Slit/Robo signaling regulates Leydig cell steroidogenesis

BACKGROUND

First identified as a regulator of neuronal axon guidance, Slit/Robo signaling has since been implicated in additional physiologic and pathologic processes, such as angiogenesis, organogenesis and cancer progression. However, its roles in the regulation of testis function have been little explored.

METHODS

Immunohistochemistry and RT-qPCR analyses were performed to detect the expression of Slit/Robo signaling effectors in the adult mouse testis. To identify the roles and mechanisms of Slit/Robo signaling in the regulation of steroidogenesis, RT-qPCR, immunoblotting and hormone measurements were carried out using Leydig cells (primary cultures and the MA10 cell line) treated with exogenous SLIT ligands, and testes from Robo1-null mice.

RESULTS

Slit1, -2 and -3 and Robo1 and -2 expression was detected in the adult mouse testis, particularly in Leydig cells. In vitro treatment of Leydig cells with exogenous SLIT ligands led to a decrease in the expression of the steroidogenic genes Star, Cyp11a1, and Cyp17a1. SLIT2 treatment decreased the phosphorylation of the key steroidogenic gene regulator CREB, possibly in part by suppressing AKT activity. Furthermore, SLIT2 treatment reduced the responsiveness of MA10 cells to luteinizing hormone by decreasing the expression of Lhcgr. Consistent with these in vitro results, an increase in testicular Star mRNA levels and intra-testicular testosterone concentrations were found in Robo1-null mice. Finally, we showed that the expression of the Slit and Robo genes in Leydig cells is enhanced by testosterone treatment in vitro, by an AR-independent mechanism.

CONCLUSION

Taken together, these results suggest that Slit/Robo signaling represents a novel mechanism that regulates Leydig cell steroidogenesis. It may act in an autocrine/paracrine manner to mediate negative feedback by testosterone on its own synthesis. Video Abstract.

Non-canonical WNT5a regulates Epithelial-to-Mesenchymal Transition in the mouse ovarian surface epithelium

The ovarian surface epithelium (OSE) is a monolayer that covers the ovarian surface and is involved in ovulation by rupturing and enabling release of a mature oocyte and by repairing the wound after ovulation. Epithelial-to-mesenchymal transition (EMT) is a mechanism that may promote wound healing after ovulation. While this process is poorly understood in the OSE, in other tissues wound repair is known to be under the control of the local microenvironment and different growth factors such as the WNT signaling pathway. Among WNT family members, WNT4 and WNT5a are expressed in the OSE and are critical for the ovulatory process. The objective of this study was to determine the potential roles of WNT4 and WNT5a in regulating the OSE layer. Using primary cultures of mouse OSE cells, we found WNT5a, but not WNT4, promotes EMT through a non-canonical Ca2+-dependent pathway, up-regulating the expression of Vimentin and CD44, enhancing cell migration, and inhibiting the CTNNB1 pathway and proliferation. We conclude that WNT5a is a stimulator of the EMT in OSE cells, and acts by suppressing canonical WNT signaling activity and inducing the non-canonical Ca2+ pathway.

Targeted Disruption of Lats1 and Lats2 in Mice Impairs Adrenal Cortex Development and Alters Adrenocortical Cell Fate

It has recently been shown that the loss of the Hippo signaling effectors Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) in adrenocortical steroidogenic cells impairs the postnatal maintenance of the adrenal gland. To further explore the role of Hippo signaling in mouse adrenocortical cells, we conditionally deleted the key Hippo kinases large tumor suppressor homolog kinases 1 and -2 (Lats1 and Lats2, two kinases that antagonize YAP and TAZ transcriptional co-regulatory activity) in steroidogenic cells using an Nr5a1-cre strain (Lats1flox/flox;Lats2flox/flox;Nr5a1-cre). We report here that developing adrenocortical cells adopt characteristics of myofibroblasts in both male and female Lats1flox/flox;Lats2flox/flox;Nr5a1-cre mice, resulting in a loss of steroidogenic gene expression, adrenal failure and death by 2 to 3 weeks of age. A marked accumulation of YAP and TAZ in the nuclei of the myofibroblast-like cell population with an accompanying increase in the expression of their transcriptional target genes in the adrenal glands of Lats1flox/flox;Lats2flox/flox;Nr5a1-cre animals suggested that the myofibroblastic differentiation could be attributed in part to YAP and TAZ. Taken together, our results suggest that Hippo signaling is required to maintain proper adrenocortical cell differentiation and suppresses their differentiation into myofibroblast-like cells.

Targeted ablation of Wnt4 and Wnt5a in Müllerian duct mesenchyme impedes endometrial gland development and causes partial Müllerian agenesis

Wnt4 and Wnt5a have well-established roles in the embryonic development of the female reproductive tract, as well as in implantation, decidualization, and ovarian function in adult mice. Although these roles appear to overlap, whether Wnt5a and Wnt4 are functionally redundant in these tissues has not been determined. We addressed this by concomitantly inactivating Wnt4 and Wnt5a in the Müllerian mesenchyme and in ovarian granulosa cells by crossing mice bearing floxed alleles to the Amhr2cre strain. Whereas fertility was reduced by ∼50% in Wnt4flox/flox; Amhr2cre/+ and Wnt5aflox/flox; Amhr2cre/+ females, Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ mice were either nearly or completely sterile. Loss of fertility was not due to an ovarian defect, as serum ovarian hormone levels, follicle counts, and ovulation rates were comparable to controls. Conversely, the uterus was abnormal in Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ mice, with thin myometrial and stromal layers, frequent fibrosis and a >90% reduction in numbers of uterine glands, suggesting redundant or additive roles of Wnt4 and Wnt5a in uterine adenogenesis. Loss of fertility in Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ mice was attributed to defects in decidualization, implantation, and placental development, the severity of which were proportional to the extent of gland loss. Furthermore, a third of Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ females had a partial agenesis of Müllerian duct-derived structures, but with normal oviducts and ovaries. Together, our results suggest that Wnt4 and Wnt5a play redundant roles in the development of the female reproductive tract, and may provide insight into the etiology of certain cases of Müllerian agenesis in women.

Lats1 and Lats2 are required for the maintenance of multipotency in the Müllerian duct mesenchyme

WNT signaling plays essential roles in the development and function of the female reproductive tract. Although crosstalk with the Hippo pathway is a key regulator of WNT signaling, whether Hippo itself plays a role in female reproductive biology remains largely unknown. Here, we show that conditional deletion of the key Hippo kinases Lats1 and Lats2 in mouse Müllerian duct mesenchyme cells caused them to adopt the myofibroblast cell fate, resulting in profound reproductive tract developmental defects and sterility. Myofibroblast differentiation was attributed to increased YAP and TAZ expression (but not to altered WNT signaling), leading to the direct transcriptional upregulation of Ctgf and the activation of the myofibroblast genetic program. Müllerian duct mesenchyme cells also became myofibroblasts in male mutant embryos, which impeded the development of the male reproductive tract and resulted in cryptorchidism. The inactivation of Lats1/2 in differentiated uterine stromal cells in vitro did not compromise their ability to decidualize, suggesting that Hippo is dispensable during implantation. We conclude that Hippo signaling is required to suppress the myofibroblast genetic program and maintain multipotency in Müllerian mesenchyme cells.

Lats1 and Lats2 are required for ovarian granulosa cell fate maintenance

Recent reports suggest that the Hippo signaling pathway influences ovarian follicle development; however, its exact roles remain unknown. Here, we examined the ovarian functions of the Hippo kinases large tumor suppressors (LATS)1 and 2, which serve to inactivate the transcriptional coactivators Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ). Inactivation of Lats1/2 in murine granulosa cells either in vitro or in vivo resulted in a loss of granulosa cell morphology, function, and gene expression. Mutant cells further underwent changes in structure and gene expression suggestive of epithelial-to-mesenchymal transition and transdifferentiation into multiple lineages. In vivo, granulosa cell-specific loss of Lats1/2 caused the ovarian parenchyma to be mostly replaced by bone tissue and seminiferous tubule-like structures. Transdifferentiation into Sertoli-like cells and osteoblasts was attributed in part to the increased recruitment of YAP and TAZ to the promoters of sex-determining region Y box 9 and bone γ-carboxyglutamate protein, key mediators of male sex determination and osteogenesis, respectively. Together, these results demonstrate for the first time a critical role for Lats1/2 in the maintenance of the granulosa cell genetic program and further highlight the remarkable plasticity of granulosa cells.-Tsoi, M., Morin, M., Rico, C., Johnson, R. L., Paquet, M., Gévry, N., Boerboom, D. Lats1 and Lats2 are required for ovarian granulosa cell fate maintenance.

Yes-associated protein expression in germ cells is dispensable for spermatogenesis in mice

Yes-associated protein (YAP), a key effector of the Hippo signaling pathway, is expressed in the nucleus of spermatogonia in mice, suggesting a potential role in spermatogenesis. Here, we report the generation of a conditional knockout mouse model (Yap^flox/flox ; Ddx4^cre/+ ) that specifically inactivates Yap in the germ cells. The inactivation of Yap in spermatogonia was found to be highly efficient in this model. The loss of Yap in the germ cells had no observable effect on spermatogenesis in vivo. Histological examination of the testes showed no structural differences between mutant animals and age-matched Yap^flox/flox controls, nor was any differences detected in gonadosomatic index, expression of germ cell markers or sperm counts. Cluster-forming assay using undifferentiated spermatogonia, including spermatogonial stem cells (SSCs), also showed that YAP is dispensable for SSC cluster formation in vitro. However, an increase in the expression of spermatogenesis and oogenesis basic helix-loop-helix 1 (Sohlh1) and neurogenin 3 (Ngn3) was observed in clusters derived from Yap^flox/flox ; Ddx4^cre/+ animals. Taken together, these results suggest that YAP fine-tunes the expression of genes associated with spermatogonial fate commitment, but that its loss is not sufficient to alter spermatogenesis in vivo.

The endogenous hydrogen sulfide generating system regulates ovulation

The generation of free-radicals such as nitric oxide has been implicated in the regulation of ovarian function, including ovulation. Tissues that generate nitric oxide typically generate another free-radical gas, hydrogen sulfide (H₂S), although little is known about the role of H₂S in ovarian function. The hypothesis of this study was that H₂S regulates ovulation. Treatment with luteinizing hormone (LH) increased the levels of mRNA and protein of the H₂S generating enzyme cystathionine γ-lyase (CTH) in granulosa cells of mice and humans in vivo and in vitro. Pharmacological inhibition of H₂S generating enzymes reduced the number of follicles ovulating in mice in vivo and in vitro, and this inhibitory action was reversed by cotreatment with a H₂S donor. Addition of a H₂S donor to cultured mouse granulosa cells increased basal and LH-dependent abundance of mRNA encoding amphiregulin, betacellulin and tumor necrosis alpha induced protein 6, proteins important for cumulus expansion and follicle rupture. Inhibition of CTH activity reduced abundance of mRNA encoding matrix metalloproteinase-2 and -9 and tissue-type plasminogen activator, and cotreatment with the H₂S donor increased the levels of these mRNA above those stimulated by LH alone. We conclude that the H₂S generating system plays an important role in the propagation of the preovulatory cascade and rupture of the follicle at ovulation.

SFRP4 Is a Negative Regulator of Ovarian Follicle Development and Female Fertility

WNT signaling regulates a variety of ovarian processes, including follicle development, granulosa cell (GC) proliferation and differentiation, steroidogenesis, and ovulation. The secreted frizzled-related proteins (SFRPs) comprise a family of WNT signaling antagonists. Sfrp4 expression was previously reported to be induced in ovarian GCs and cumulus cells in vivo following human chorionic gonadotropin treatment, suggesting that it may play key roles in cumulus expansion, ovulation/luteinization, and corpus luteum (CL) function. In this study, we aimed to define the physiological roles of Sfrp4 in the ovary by gene targeting. Sfrp4-null female mice were found to produce larger litters than did their wild-type littermates. Although previous studies had suggested roles of Sfrp4 in luteal cell survival, no differences in CL formation, morphology, steroidogenesis, involution, or luteal cell apoptosis were found in Sfrp4-null mice. Likewise, cumulus expansion occurred normally in Sfrp4-null mice, with minimal changes in cumulus cell gene expression. Hyperfertility in the Sfrp4-null model was ultimately attributed to decreased antral follicle atresia, leading to an enhanced ovulatory rate. Increased expression of FSH- and LH-responsive genes was found in GCs from Sfrp4-null mice, and GCs isolated from Sfrp4-null mice were found to be hyperresponsive to FSH and LH in vitro. Although Sfrp2 was found to be overexpressed in the GCs of Sfrp4-null mice (suggesting a compensatory mechanism), Sfrp2-null mice had normal fertility and ovulatory rates, and Sfrp2/4 double knockout mice did not differ from Sfrp4-null mice. Taken together, our results suggest that SFRP4 acts to attenuate GC responsiveness to gonadotropins, thereby decreasing follicle survival, ovulatory rate, and fertility.

Expression of the Hippo signalling effectors YAP and TAZ in canine mammary gland hyperplasia and malignant transformation of mammary tumours

Canine mammary tumours (CMTs) are common neoplasms in dogs that feature many of the clinical, genetic and molecular characteristics of human breast cancer. Despite their high metastatic potential, few adjuvant chemotherapeutic treatment options exist for malignant CMTs, and the development of novel, targeted pharmacological approaches will require a better understanding of their pathogenesis. As recent evidence suggests that dysregulated Hippo signalling is involved in the development and progression of breast cancer, we sought to determine if this pathway could also play a role in CMT. The expression of the Hippo signalling effectors YAP and TAZ was analysed by immunoblotting and immunohistochemistry in samples including normal mammary gland, lobular hyperplasia, benign tumours and malignant tumours of all grades. We found a significant increase in TAZ (but not YAP) expression occurred in lobular hyperplasia relative to normal mammary gland, suggesting a role for TAZ in non-neoplastic epithelial proliferation. Nuclear expression of both TAZ and YAP were significantly higher in malignant tumours than in benign ones, suggesting that Hippo dysregulation could play a role in CMT malignant transformation. No differences in YAP or TAZ expression were detected between grades of malignant tumours. Together, our results indicate that alterations in Hippo signalling may play a role in the pathogenesis of CMT, in a manner similar to breast cancer. Hippo pathway components may therefore represent targets for the development of novel chemotherapeutic agents that could be useful for the treatment of both the human and canine diseases.

Conditional Deletion of FOXL2 and SMAD4 in Gonadotropes of Adult Mice Causes Isolated FSH Deficiency

The glycoprotein FSH, a product of pituitary gonadotrope cells, regulates ovarian follicle development in females and spermatogenesis in males. FSH is a heterodimer of the common α gonadotropin subunit and the hormone-specific FSHβ subunit (a product of the Fshb gene). Using a conditional knockout approach (Cre-lox), we previously demonstrated that Fshb expression in mice depends on the transcription factors forkhead box L2 (FOXL2) and SMAD4. Deletion of Foxl2 or Smad4 alone led to FSH deficiency, female subfertility, and oligozoospermia in males. Simultaneous deletion of the two genes yielded a greater suppression of FSH and female sterility. The Cre-driver used previously was first active during embryonic development. Therefore, it is unclear whether FOXL2 and SMAD4 play important roles in the development or adult function of gonadotropes, or both. To address this question, we developed a tamoxifen-inducible Cre-driver line, which enabled Foxl2 and Smad4 gene deletions in gonadotropes of adult mice. After tamoxifen treatment, females with previously demonstrated fertility exhibited profound reductions in FSH levels, arrested ovarian follicle development, and sterility. FSH levels were comparably reduced in males 1 or 2 months after treatment; however, spermatogenesis was unaffected. These data indicate that (1) FOXL2 and SMAD4 are necessary to maintain FSH synthesis in gonadotrope cells of adult mice, (2) FSH is essential for female reproduction but appears to be unnecessary for the maintenance of spermatogenesis in adult male mice, and (3) the inducible Cre-driver line developed here provides a powerful tool to interrogate gene function in gonadotrope cells of adult mice.

Yes-associated protein and WW-containing transcription regulator 1 regulate the expression of sex-determining genes in Sertoli cells, but their inactivation does not cause sex reversal

Yes-associated protein (YAP) and WW-containing transcription regulator 1 (WWTR1) are two functionally redundant transcriptional regulators that are downstream effectors of the Hippo signaling pathway, and that act as major regulators of cell growth and differentiation. To elucidate their role in Sertoli cells, primary Sertoli cell culture from Yapflox/flox; Wwtr1flox/flox animals were infected with a Cre recombinase-expressing adenovirus. Concomitant inactivation of Yap and Wwtr1 resulted in a decrease in the mRNA levels of the male sex differentiation genes Dhh, Dmrt1, Sox9, and Wt1, whereas those of genes involved in female differentiation (Wnt4, Rspo1, and Foxl2) were induced. SOX9, FOXL2, and WNT4 proteins were regulated in the same manner as their mRNAs in response to loss of YAP and WWTR1. To further characterize the role of YAP and WWTR1 in Sertoli cells, we generated a mouse model (Yapflox/flox; Wwtr1flox/flox; Amhcre/+) in which Yap and Wwtr1 were conditionally deleted in Sertoli cells. An increase in the number of apoptotic cells was observed in the seminiferous tubules of 4 dpp mutant mice, leading to a reduction in testis weights and a decrease in the number of Sertoli cells in adult animals. Gene expression analyses of testes from 4 dpp Yapflox/flox; Wwtr1flox/flox; Amhcre/+ mice showed that Sertoli cell differentiation is initially altered, as Dhh, Dmrt1, and Sox9 mRNA levels were downregulated, whereas Wnt4 mRNA levels were increased. However, expression of these genes was not changed in older animals. Together, these results suggest a novel role of the Hippo signaling pathway in the mechanisms of sex differentiation.

In vitro efficacy of a first-generation valosin-containing protein inhibitor (CB-5083) against canine lymphoma

Valosin-containing protein (VCP), through its critical role in the maintenance of protein homeostasis, is a promising target for the treatment of several malignancies, including canine lymphoma. CB-5083, a first-in-class VCP inhibitor, exerts cytotoxicity through the induction of irreversible proteotoxic stress and possesses a broad spectrum of anticancer activity. Here, we determined the cytotoxicity CB-5083 in canine lymphoma cells and its mechanism of action in vitro. Canine lymphoma cell lines were treated with varying concentrations of CB-5083 and assessed for viability by trypan blue exclusion and apoptosis by caspase activity assays. The mechanism of CB-5083 action was determined by immunoblotting and RT-qPCR analyses of Lys48 ubiquitination and markers of ER stress (DDIT3), autophagy (SQSTM1, MAP1LC3A) and DNA damage (γH2AX). Unfolded protein response markers were also evaluated by immunoblotting (eIF2α, P-eIF2α) and RT-qPCR (ATF4). CB-5083 treatment resulted in preferential cytotoxicity in canine lymphoma cell lines over control peripheral blood mononuclear cells. CB-5083 rapidly disrupted the ubiquitin-dependent protein degradation system, inducing sustained ER stress as indicated by a dramatic increase in DDIT3. Activation of the unfolded protein response occurred through the increase eIF2α phosphorylation and increased transcription of ATF4, but did not re-establish protein homeostasis. Cells rapidly underwent apoptosis through activation of the caspase cascade. These results further validate VCP as an attractive target for the treatment of canine lymphoma and identify CB-5083 as a novel therapy with clinical potential for this malignancy.

Targeted Disruption of YAP and TAZ Impairs the Maintenance of the Adrenal Cortex

Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are functionally redundant transcriptional regulators that are downstream effectors of the Hippo signaling pathway. They act as major regulators of stem cell maintenance, cell growth, and differentiation. To characterize their roles in the adrenal cortex, we generated a mouse model in which Yap and Taz were conditionally deleted in steroidogenic cells (Yapflox/flox;Tazflox/flox;Nr5a1cre/+). Male Yapflox/flox;Tazflox/flox;Nr5a1cre/+ mice were characterized by an age-dependent degeneration of the adrenal cortex associated with an increase in apoptosis and a progressive reduction in the expression levels of steroidogenic genes. Evaluation of the expression levels of stem and progenitor cell population markers in the adrenal glands of Yapflox/flox;Tazflox/flox;Nr5a1cre/+ mice also showed the downregulation of sonic hedgehog (Shh), a marker of the subcapsular progenitor cell population. Gross degenerative changes were not observed in the adrenal glands of Yapflox/flox;Tazflox/flox;Nr5a1cre/+ females, although steroidogenic capacity and Shh expression were reduced, suggesting that mechanisms of adrenocortical maintenance are sex specific. These results define a crucial role for YAP and TAZ in the maintenance of the postnatal adrenal cortex.

In Vitro Validation of the Hippo Pathway as a Pharmacological Target for Canine Mammary Gland Tumors

Canine mammary tumors (CMTs) are the most common neoplasms in intact female dogs. Some clinical and molecular similarities between certain CMT subtypes and breast cancer make them a potential model for the study of the human disease. As misregulated Hippo signaling is thought to play an important role in breast cancer development and also occurs in CMTs, we sought to determine if Hippo represents a valid pharmacological target for the treatment of CMTs. Six CMT cell lines were assessed for their expression of the Hippo pathway effectors YAP and TAZ and for their sensitivity to verteporfin, an inhibitor of YAP-mediated transcriptional coactivation. Four cell lines that expressed YAP (CMT-9, -12, -28, -47) were found to be very sensitive to verteporfin treatment, which killed the cells through induction of apoptosis with ED50 values of 14-79 nM. Conversely, two YAP-negative cell lines (CF-35, CMT-25) were an order of magnitude more resistant to verteporfin. Verteporfin suppressed the expression of YAP/TAZ target genes, particularly CYR61 and CTGF, which play important roles in breast cancer development. Verteporfin was also able to inhibit cell migration and anchorage-independent growth. Likewise, verteporfin efficiently suppressed tumor cell invasiveness in the CMT-28 and -47 lines, but not in CF-35 cells. Together, our findings provide proof of principle that pharmacological targeting of the Hippo pathway compromises the viability and attenuates the malignant behavior of CMT cells. These results will serve as the basis for the development of novel chemotherapeutic approaches for CMTs that could translate to human medicine.

A hypoxia response element in the Vegfa promoter is required for basal Vegfa expression in skin and for optimal granulation tissue formation during wound healing in mice

Hypoxia in skin wounds is thought to contribute to healing through the induction of hypoxia inducible factor-1 (HIF-1). Although HIF-1 can regulate the expression of vascular endothelial growth factor A (Vegfa), whether hypoxia and HIF-1 are required to induce Vegfa expression in the context of wound healing is unknown. To test this hypothesis, we evaluated Vegfa expression and wound healing in mutant mice that lack a functional HIF-1 binding site in the Vegfa promoter. Full-thickness excisional wounds were made using a biopsy punch, left to heal by second intention, and granulation tissue isolated on a time course during healing. mRNA levels of Vegfa and its target genes platelet-derived growth factors B (Pdgfb) and stromal cell-derived factor-1 (Sdf1) were measured by RT-qPCR, and HIF-1alpha and VEGFA protein levels measured by immunoblotting. Lower levels of Vegfa, Pdgf1 and Sdf1 mRNA were found in intact skin of mutant mice relative to wild-type controls (n = 6 mice/genotype), whereas levels in granulation tissue during wound healing were unaltered. VEGFA protein levels were also lower in intact skin of the mutant versus the wild-type mice. Decreased Vegfa mRNA levels in skin of mutant mice could not be attributed to decreased HIF-1alpha protein expression, and were therefore a consequence of the loss of HIF-1 responsiveness of the Vegfa promoter. Comparative histologic analyses of healing wounds in mutant and wild-type mice (n = 8 mice/genotype) revealed significant defects in granulation tissue in the mutant mice, both in terms of quantity and capillary density, although epithelialization and healing rates were unaltered. We conclude that HIF-1 is not a major regulator of Vegfa expression during wound healing; rather, it serves to maintain basal levels of expression of Vegfa and its target genes in intact skin, which are required for optimal granulation tissue formation in response to wounding.

mTOR Regulates Gap Junction Alpha-1 Protein Trafficking in Sertoli Cells and Is Required for the Maintenance of Spermatogenesis in Mice

The mammalian target of rapamycin (Mtor) gene encodes a serine/threonine kinase that acts as a master regulator of processes as diverse as cell growth, protein synthesis, cytoskeleton reorganization, and cell survival. In the testis, physiological roles for Mtor have been proposed in perinatal Sertoli cell proliferation and blood-testis barrier (BTB) remodeling during spermatogenesis, but no in vivo studies of Mtor function have been reported. Here, we used a conditional knockout approach to target Mtor in Sertoli cells. The resulting Mtor(flox/flox); Amhr2(cre/+) mice were characterized by progressive, adult-onset testicular atrophy associated with disorganization of the seminiferous epithelium, loss of Sertoli cell polarity, increased germ cell apoptosis, premature release of germ cells, decreased epididymal sperm counts, increased sperm abnormalities, and infertility. Histopathologic analysis and quantification of the expression of stage-specific markers showed a specific loss of pachytene spermatocytes and spermatids. Although the BTB and the ectoplasmic specializations did not appear to be altered in Mtor(flox/flox);Amhr2(cre/+) mice, a dramatic redistribution of gap junction alpha-1 (GJA1) was detected in their Sertoli cells. Phosphorylation of GJA1 at Ser373, which is associated with its internalization, was increased in the testes of Mtor(flox/flox); Amhr2(cre/+) mice, as was the expression and phosphorylation of AKT, which phosphorylates GJA1 at this site. Together, these results indicate that Mtor expression in Sertoli cells is required for the maintenance of spermatogenesis and the progression of germ cell development through the pachytene spermatocyte stage. One mechanism of mTOR action may be to regulate gap junction dynamics by inhibiting AKT, thereby decreasing GJA1 phosphorylation and internalization. mTOR regulates gap junction alpha-1 protein distribution in Sertoli cells and is necessary for progression through the pachytene spermatocyte stage.

WNT5a is required for normal ovarian follicle development and antagonizes gonadotropin responsiveness in granulosa cells by suppressing canonical WNT signaling

Whereas the roles of the canonical wingless-type MMTV (mouse mammary tumor virus) integration site family (WNT) signaling pathway in the regulation of ovarian follicle growth and steroidogenesis are now established, noncanonical WNT signaling in the ovary has been largely overlooked. Noncanonical WNTs, including WNT5a and WNT11, are expressed in granulosa cells (GCs) and are differentially regulated throughout follicle development, but their physiologic roles remain unknown. Using conditional gene targeting, we found that GC-specific inactivation ofWnt5a(but notWnt11) results in the female subfertility associated with increased follicular atresia and decreased rates of ovulation. Microarray analyses have revealed that WNT5a acts to down-regulate the expression of FSH-responsive genesin vitro, and corresponding increases in the expression of these genes have been found in the GCs of conditional knockout mice. Unexpectedly, we found that WNT5a regulates its target genes not by signalingviathe WNT/Ca(2+)or planar cell polarity pathways, but rather by inhibiting the canonical pathway, causing both β-catenin (CTNNB1) and cAMP responsive element binding (CREB) protein levels to decreaseviaa glycogen synthase kinase-3β-dependent mechanism. We further found that WNT5a prevents follicle-stimulating hormone and luteinizing protein from up-regulating the CTNNB1 and CREB proteins and their target genes, indicating that WNT5a functions as a physiologic inhibitor of gonadotropin signaling. Together, these findings identify WNT5a as a key regulator of follicle development and gonadotropin responsiveness.-Abedini, A., Zamberlam, G., Lapointe, E., Tourigny, C., Boyer, A., Paquet, M., Hayashi, K., Honda, H., Kikuchi, A., Price, C., Boerboom, D. WNT5a is required for normal ovarian follicle development and antagonizes gonadotropin responsiveness in granulosa cells by suppressing canonical WNT signaling.

Motif mimetic of epsin perturbs tumor growth and metastasis

Tumor angiogenesis is critical for cancer progression. In multiple murine models, endothelium-specific epsin deficiency abrogates tumor progression by shifting the balance of VEGFR2 signaling toward uncontrolled tumor angiogenesis, resulting in dysfunctional tumor vasculature. Here, we designed a tumor endothelium-targeting chimeric peptide (UPI) for the purpose of inhibiting endogenous tumor endothelial epsins by competitively binding activated VEGFR2. We determined that the UPI peptide specifically targets tumor endothelial VEGFR2 through an unconventional binding mechanism that is driven by unique residues present only in the epsin ubiquitin-interacting motif (UIM) and the VEGFR2 kinase domain. In murine models of neoangiogenesis, UPI peptide increased VEGF-driven angiogenesis and neovascularization but spared quiescent vascular beds. Further, in tumor-bearing mice, UPI peptide markedly impaired functional tumor angiogenesis, tumor growth, and metastasis, resulting in a notable increase in survival. Coadministration of UPI peptide with cytotoxic chemotherapeutics further sustained tumor inhibition. Equipped with localized tumor endothelium-specific targeting, our UPI peptide provides potential for an effective and alternative cancer therapy.

Pharmacological targeting of valosin containing protein (VCP) induces DNA damage and selectively kills canine lymphoma cells

Background

Valosin containing protein (VCP) is a critical mediator of protein homeostasis and may represent a valuable therapeutic target for several forms of cancer. Overexpression of VCP occurs in many cancers, and often in a manner correlating with malignancy and poor outcome. Here, we analyzed VCP expression in canine lymphoma and assessed its potential as a therapeutic target for this disease.

Methods

VCP expression in canine lymphomas was evaluated by immunoblotting and immunohistochemistry. The canine lymphoma cell lines CLBL-1, 17–71 and CL-1 were treated with the VCP inhibitor Eeyarestatin 1 (EER-1) at varying concentrations and times and were assessed for viability by trypan blue exclusion, apoptosis by TUNEL and caspase activity assays, and proliferation by propidium iodide incorporation and FACS. The mechanism of EER-1 action was determined by immunoblotting and immunofluorescence analyses of Lys48 ubiquitin and markers of ER stress (DDIT3), autophagy (SQSTM1, MAP1LC3A) and DNA damage (γH2AFX). TRP53/ATM-dependent signaling pathway activity was assessed by immunoblotting for TRP53 and phospho-TRP53 and real-time RT-PCR measurement of Cdkn1a mRNA.

Results

VCP expression levels in canine B cell lymphomas were found to increase with grade. EER-1 treatment killed canine lymphoma cells preferentially over control peripheral blood mononuclear cells. EER-1 treatment of CLBL-1 cells was found to both induce apoptosis and cell cycle arrest in G1. Unexpectedly, EER-1 did not appear to act either by inducing ER stress or inhibiting the aggresome-autophagy pathway. Rather, a rapid and dramatic increase in γH2AFX expression was noted, indicating that EER-1 may act by promoting DNA damage accumulation. Increased TRP53 phosphorylation and Cdkn1a mRNA levels indicated an activation of the TRP53/ATM DNA damage response pathway in response to EER-1, likely contributing to the induction of apoptosis and cell cycle arrest.

Conclusions

These results correlate VCP expression with malignancy in canine B cell lymphoma. The selective activity of EER-1 against lymphoma cells suggests that VCP will represent a clinically useful therapeutic target for the treatment of lymphoma. We further suggest a mechanism of EER-1 action centered on the DNA repair response that may be of central importance for the design and characterization of VCP inhibitory compounds for therapeutic use.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1489-1) contains supplementary material, which is available to authorized users.

Non-canonical WNT5A is a potential regulator of granulosa cell function in cattle

The WNT family has been implicated in follicular development in rodents, however, the role of WNTs in the follicle of monovulatory species is poorly understood. The objective of this study was to determine the potential roles of WNTs in bovine granulosa cell function. Cells cultured in serum-free medium expressed mRNA encoding WNT2B, WNT5B and WNT5A. Levels of WNT5A, but not of WNT2B or WNT5B mRNA, were down-regulated by FSH. Addition of WNT5A to cultured cells suppressed FSH-stimulated estradiol and progesterone secretion, and levels of mRNA encoding the steroidogenic enzymes CYP19A1, CYP11A1 and the FSH receptor, but had no effect on cell proliferation or apoptosis. Immunoblot experiments showed that WNT5A reduced activation of CTNNB1 and stimulated phosphorylation of MAPK8 and JUN proteins. We conclude that WNT5A is a negative regulator of FSH-stimulated granulosa cell steroidogenesis, and that it acts by suppressing canonical WNT signaling activity and inducing the non-canonical MAPK8/JUN pathway.

β-catenin stabilization in gonadotropes impairs FSH synthesis in male mice in vivo

Although classically considered a WNT signaling intermediary, β-catenin (CTNNB1) can also mediate GnRH induction of gonadotropin β-subunit (Fshb and Lhb) transcription in the murine gonadotrope-like cell line LβT2. Here, we assessed CTNNB1's role in gonadotropin synthesis in vivo. We used a Cre/lox approach to introduce both gain- and loss-of-function mutations in the murine Ctnnb1 gene in gonadotrope cells. Gonadotropin production and fertility were normal in Ctnnb1 knockout mice. Similarly, females harboring a deletion of exon 3 of Ctnnb1, which stabilizes the resulting CTNNB1 protein, showed normal fertility and gonadotropin synthesis. Interestingly, males with the activating CTNNB1-Δexon 3 mutation exhibited 50% reductions in FSH synthesis and secretion, without a corresponding change in LH. This selective regulation of FSH suggested an alteration in the activin/inhibin/follistatin system. Indeed, CTNNB1-Δexon 3 males showed a 60% increase in serum inhibin B levels, and in culture, their pituitaries exhibited a greater sensitivity to exogenous inhibin than controls. At the same time, pituitary, but not testicular, follistatin (Fst) expression was increased significantly in these mice. Castration normalized FSH levels in CTNNB1-Δexon 3 males to those seen in castrated controls. Paradoxically, pituitaries from CTNNB1-Δexon 3 males exhibited greater basal and activin-stimulated FSH synthesis in vitro. Similarly, CTNNB1-Δexon 3 overexpression potentiated activin A-induced murine Fshb promoter activity in LβT2 cells. Together, these results indicate that CTNNB1 is dispensable for gonadotropin synthesis in vivo. However, sustained CTNNB1 signaling potentiates activin-induced Fshb expression in gonadotropes, but this effect is overcome in vivo by enhanced inhibin feedback sensitivity and Fst expression.

HIF1 activity in granulosa cells is required for FSH-regulated Vegfa expression and follicle survival in mice

Recent evidence has suggested that vascular endothelial growth factor A (VEGFA) is an important regulator of ovarian follicle development and survival. Both LH and FSH regulate Vegfa expression in granulosa cells and signal via the transcription factor hypoxia inducible factor 1 (HIF1). To further study the mechanism of action of HIF1 in the regulation of Vegfa, we studied Vegfa(delta/delta) mice, which lack a hypoxia response element in the Vegfa promoter. Granulosa cells from Vegfa(delta/delta) mice failed to respond to FSH or LH with an increase in Vegfa mRNA expression in vitro, and granulosa cells isolated from eCG-treated immature Vegfa(delta/delta) mice had significantly lower Vegfa mRNA levels compared to controls. However, normal Vegfa mRNA levels were detected in the granulosa cells from immature Vegfa(delta/delta) mice following hCG treatment. Vegfa(delta/delta) females produced infrequent litters, and their pups died shortly after birth. Ovaries from Vegfa(delta/delta) mice were much smaller than controls and contained few antral follicles and corpora lutea. Antral follicles numbers were decreased by nearly 50% in ovaries from Vegfa(delta/delta) mice relative to controls, and 74% of antral follicles in Vegfa(delta/delta) ovaries were atretic. Serum progesterone levels in adult Vegfa(delta/delta) females were significantly lower, apparently reflecting reduced numbers of corpora lutea. This study demonstrates for the first time the requirement of HIF1 for FSH-regulated Vegfa expression in vivo and that HIF1 acts via a single hypoxia response element in the Vegfa promoter to exert its regulatory functions. Our findings also further define the physiological role of VEGFA in follicle development.

NR5A2 regulates Lhb and Fshb transcription in gonadotrope-like cells in vitro, but is dispensable for gonadotropin synthesis and fertility in vivo

Successful mammalian reproduction depends on proper synthesis of the pituitary-derived glycoprotein hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Several transcription factors cooperate to activate cell-specific and hormone-regulated expression of the gonadotropin beta subunits (Lhb and Fshb). Among these, NR5A1 (steroidogenic factor 1; SF1) has been shown to directly bind to the Lhb promoter, mediate basal and gonadotropin-releasing hormone (GnRH)-stimulated Lhb transcription, and possibly directly regulate Fshb expression. Recently, the closely-related NR5A2 was shown to activate the rat Lhb promoter in vitro. Here, we further characterized the role of NR5A2 in regulating gonadotropin synthesis. Ectopically expressed NR5A2 directly activated the murine Lhb promoter in a manner identical to that of NR5A1, whereas neither factor activated the murine Fshb promoter. In LβT2 gonadotrope-like cells, depletion of endogenous NR5A1 or NR5A2 impaired basal and GnRH-stimulated Lhb and Fshb transcription. To analyze the physiological role of NR5A2 in gonadotropes in vivo, we generated mice with a gonadotrope-specific deletion of Nr5a2. In contrast with our in vitro data, these mice had normal pituitary Lhb and Fshb expression and intact fertility. Together, our data establish that NR5A2 can act in a non-redundant manner to regulate Lhb and Fshb transcription in vitro, but is dispensable in vivo.

Impaired fertility and FSH synthesis in gonadotrope-specific Foxl2 knockout mice

Impairments in pituitary FSH synthesis or action cause infertility. However, causes of FSH dysregulation are poorly described, in part because of our incomplete understanding of mechanisms controlling FSH synthesis. Previously, we discovered a critical role for forkhead protein L2 (FOXL2) in activin-stimulated FSH β-subunit (Fshb) transcription in immortalized cells in vitro. Here, we tested the hypothesis that FOXL2 is required for FSH synthesis in vivo. Using a Cre/lox approach, we selectively ablated Foxl2 in murine anterior pituitary gonadotrope cells. Conditional knockout (cKO) mice developed overtly normally but were subfertile in adulthood. Testis size and spermatogenesis were significantly impaired in cKO males. cKO females exhibited reduced ovarian weight and ovulated fewer oocytes in natural estrous cycles compared with controls. In contrast, ovaries of juvenile cKO females showed normal responses to exogenous gonadotropin stimulation. Both male and female cKO mice were FSH deficient, secondary to diminished pituitary Fshb mRNA production. Basal and activin-stimulated Fshb expression was similarly impaired in Foxl2 depleted primary pituitary cultures. Collectively, these data definitively establish FOXL2 as the first identified gonadotrope-restricted transcription factor required for selective FSH synthesis in vivo.

FZD1 regulates cumulus expansion genes and is required for normal female fertility in mice

WNT4 is required for normal ovarian follicle development and female fertility in mice, but how its signal is transduced remains unknown. Fzd1 encodes a WNT receptor whose expression is markedly induced in both mural granulosa cells and cumulus cells during the preovulatory period, in a manner similar to Wnt4. To study the physiological roles of FZD1 in ovarian physiology and to determine whether it serves as receptor for WNT4, Fzd1-null mice were created by gene targeting. Whereas rare Fzd1(-/-) females were sterile because of uterine fibrosis and ovarian tubulostromal hyperplasia, most were subfertile, producing ≈1 fewer pup per litter on average relative to controls. Unlike WNT4-deficient mice, ovaries from Fzd1(-/-) mice had normal weights, numbers of follicles, steroid hormone production, and WNT4 target gene expression levels. Microarray analyses of granulosa cells from periovulatory follicles revealed few genes whose expression was altered in Fzd1(-/-) mice. However, gene expression analyses of cumulus-oocyte complexes (COCs) revealed a blunted response of both oocyte (Zp3, Dppa3, Nlrp5, and Bmp15) and cumulus (Btc, Ptgs2, Sema3a, Ptx3, Il6, Nts, Alcam, and Cspg2) genes to the ovulatory signal, whereas the expression of these genes was not altered in WNT4-deficient COCs from Wnt4(tm1.1Boer/tm1.1Boer);Tg (CYP19A1-cre)1Jri mice. Despite altered gene expression, cumulus expansion appeared normal in Fzd1(-/-) COCs both in vitro and in vivo. Together, these results indicate that Fzd1 is required for normal female fertility and may act in part to regulate oocyte maturation and cumulus cell function, but it is unlikely to function as the sole ovarian WNT4 receptor.

Pharmacological targeting of mammalian target of rapamycin inhibits ovarian granulosa cell tumor growth

Few targeted therapies have been developed for ovarian granulosa cell tumor (GCT), even though it represents 5% of all malignant ovarian tumors in women. As misregulation of PI3K/AKT signaling has been implicated in GCT development, we hypothesized that the AKT signaling effector mammalian target of rapamycin (mTOR) may play a role in the pathogenesis of GCT and could represent a therapeutic target. Analyses of human GCT samples showed an increase in protein levels of mTOR and its downstream effectors RPS6KB1, RPS6, eIF4B and PPARG relative to normal granulosa cells, suggestive of an increase in mTOR pathway activity and increased translational activity and/or protein stability. We next sought to evaluate mTOR as a GCT therapeutic target using the Pten (tm1Hwu/tmiHwu);Ctnnb1 (tm1Mmt/+);Amhr2 (tm3(cre)Bhr/+) (PCA) mouse model, in which mTOR, RPS6KB1, eIF4B and PPARG are upregulated in tumor cells in a manner similar to human GCT. Treatment of PCA mice with the mTOR-specific inhibitor everolimus reduced tumor growth rate (1.5-fold; P < 0.05) and also reduced total tumor burden (4.7-fold; P < 0.05) and increased survival rate (78 versus 44% in the vehicle group) in a PCA surgical model of GCT peritoneal carcinomatosis. Everolimus decreased tumor cell proliferation and tumor cell volume relative to controls (P < 0.05), whereas apoptosis was unaffected. Phosphorylation of RPS6KB1 and RPS6 were decreased (P < 0.05) by everolimus, but RPS6KB1, RPS6, eIF4B and PPARG expressions were not affected. These results suggest that mTOR is a valid and clinically useful pharmacological target for the treatment of GCT, although its inhibition does not reverse all consequences of aberrant PI3K/AKT signaling in the PCA model.

Proteomic profiling of a mouse model for ovarian granulosa cell tumor identifies VCP as a highly sensitive serum tumor marker in several human cancers

The initial aim of this study was to identify novel serum diagnostic markers for the human ovarian granulosa cell tumor (GCT), a tumor that represents up to 5% of all ovarian cancers. To circumvent the paucity of human tissues available for analyses, we used the Ctnnb1^tm1Mmt/+;Pten^{tm1Hwu/tmiHwu};Amhr2^{tm3(cre)Bhr/+} transgenic mouse model, which features the constitutive activation of CTNNB1 signaling combined with the loss of Pten in granulosa cells and develops GCTs that mimic aggressive forms of the human disease. Proteomic profiling by mass spectrometry showed that vinculin, enolase 1, several heat shock proteins, and valosin containing protein (VCP) were more abundantly secreted by cultured mouse GCT cells compared to primary cultured GC. Among these proteins, only VCP was present in significantly increased levels in the preoperative serum of GCT cancer patients compared to normal subjects. To determine the specificity of VCP, serum levels were also measured in ovarian carcinoma, non-Hodgkin's lymphoma and breast, colon, pancreatic, lung, and prostate cancer patients. Increased serum VCP levels were observed in the majority of cancer cases, with the exception of patients with lung or prostate cancer. Moreover, serum VCP levels were increased in some GCT, ovarian carcinoma, breast cancer, and colon cancer patients who did not otherwise display increased levels of widely used serum tumor markers for their cancer type (e.g. inhibin A, inhibin B, CA125, CEA, or CA15.3). These results demonstrate the potential use of VCP as highly sensitive serum marker for GCT as well as several other human cancers.

Either Kras activation or Pten loss similarly enhance the dominant-stable CTNNB1-induced genetic program to promote granulosa cell tumor development in the ovary and testis

WNT, RAS or phosphoinositide 3-kinase signaling pathways control specific stages of ovarian follicular development. To analyze the functional interactions of these pathways in granulosa cells during follicular development in vivo, we generated specific mutant mouse models. Stable activation of the WNT signaling effector β-catenin (CTNNB1) in granulosa cells results in the formation of premalignant lesions that develop into granulosa cell tumors (GCTs) spontaneously later in life or following targeted deletion of the tumor suppressor gene Pten. Conversely, expression of oncogenic KRAS(G12D) dramatically arrests proliferation, differentiation and apoptosis in granulosa cells, and consequently, small abnormal follicle-like structures devoid of oocytes accumulate in the ovary. Because of the potent anti-proliferative effects of KRAS(G12D) in granulosa cells, we sought to determine whether KRAS(G12D) would block precancerous lesion and tumor formation in follicles of the CTNNB1-mutant mice. Unexpectedly, transgenic Ctnnb1;Kras-mutant mice exhibited increased GC proliferation, decreased apoptosis and impaired differentiation and developed early-onset GCTs leading to premature death in a manner similar to the Ctnnb1;Pten-mutant mice. Microarray and reverse transcription-PCR analyses revealed that gene regulatory processes induced by CTNNB1 were mostly enhanced by either KRAS activation or Pten loss in remarkably similar patterns and degree. The concomitant activation of CTNNB1 and KRAS in Sertoli cells also caused testicular granulosa cell tumors that showed gene expression patterns that partially overlapped those observed in GCTs of the ovary. Although the mutations analyzed herein have not yet been linked to adult GCTs in humans, they may be related to juvenile GCTs or to tumors in other tissues where CTNNB1 is mutated. Importantly, the results provide strong evidence that CTNNB1 is the driver in these contexts and that KRAS(G12D) and Pten loss promote the program set in motion by the CTNNB1.

CTNNB1 signaling in sertoli cells downregulates spermatogonial stem cell activity via WNT4

Constitutive activation of the WNT signaling effector CTNNB1 (β-catenin) in the Sertoli cells of the Ctnnb1^tm1Mmt/+;Amhr2^{tm3(cre)Bhr/+} mouse model results in progressive germ cell loss and sterility. In this study, we sought to determine if this phenotype could be due to a loss of spermatogonial stem cell (SSC) activity. Reciprocal SSC transplants between Ctnnb1^tm1Mmt/+;Amhr2^{tm3(cre)Bhr/+} and wild-type mice showed that SSC activity is lost in Ctnnb1^tm1Mmt/+;Amhr2^{tm3(cre)Bhr/+} testes over time, whereas the mutant testes could not support colonization by wild-type SSCs. Microarray analyses performed on cultured Sertoli cells showed that CTNNB1 induces the expression of genes associated with the female sex determination pathway, which was also found to occur in Ctnnb1^tm1Mmt/+;Amhr2^{tm3(cre)Bhr/+} testes. One CTNNB1 target gene encoded the secreted signaling molecule WNT4. We therefore tested the effects of WNT4 on SSC-enriched germ cell cultures, and found that WNT4 induced cell death and reduced SSC activity without affecting cell cycle. Conversely, conditional inactivation of Wnt4 in the Ctnnb1^tm1Mmt/+;Amhr2^{tm3(cre)Bhr/+} model rescued spermatogenesis and male fertility, indicating that WNT4 is the major effector downstream of CTNNB1 responsible for germ cell loss. Furthermore, WNT4 was found to signal via the CTNNB1 pathway in Sertoli cells, suggesting a self-reinforcing positive feedback loop. Collectively, these data indicate for the first time that ectopic activation of a signaling cascade in the stem cell niche depletes SSC activity through a paracrine factor. These findings may provide insight into the pathogenesis of male infertility, as well as embryonic gonadal development.

Hypoxia regulates the expression of extracellular matrix associated proteins in equine dermal fibroblasts via HIF1

BACKGROUND

Exuberant granulation tissue (EGT), a fibrotic healing disorder resembling the human keloid, occurs almost exclusively in limb wounds of horses and may be caused in part by a relative state of hypoxia within the wound.

OBJECTIVE

The objectives of this study were therefore to (1) assess the effects of hypoxia on equine dermal fibroblast (EDF) proliferation and apoptosis, (2) study the effects of hypoxia on the expression of key extracellular matrix (ECM) associated proteins and determine if such effects are dependent on hypoxia-inducible factor (HIF), and (3) determine if EDFs from the body or limb respond differently to hypoxia.

METHODS

EDFs were isolated and cultured from skin from body or limb under normoxic or hypoxic conditions for up to 7days.

RESULTS

Hypoxia significantly stimulated EDF proliferation, but had no effect on cell survival. The hypoxia-mimetic agent CoCl(2) up-regulated COL1A1 expression and down-regulated MMP2 expression, suggesting an increase in ECM synthesis and a decrease in turnover. Both regulatory effects were inhibited by the addition of echinomycin, indicating that they are mediated by the transcriptional regulatory activity of HIF. No differences were observed between EDFs originating from body or limb for any effect of hypoxia or CoCl(2), suggesting that EGT development does not depend on intrinsic properties of limb fibroblasts.

CONCLUSIONS

We conclude that hypoxia regulates ECM remodeling via HIF1 in EDFs, and that this may be an important determinant in the pathogenesis of equine EGT.

Atypical caudal duplication with phenotypic sex reversal in a dog

A male German Shepherd Dog mix was presented for chronic non-weight-bearing lameness of the left hind limb. At clinical examination, the dog's left hind limb had severe joint contractures, with the presence of what appeared to be a second paw. The dog also had 2 sets of external genitalia of opposite phenotypic sex; a complete male reproductive tract with a left retained testicle and a right descended testicle, as well as rudimentary female external genitalia including a hypoplastic vulva with a blind-end vagina and a hypertrophied clitoris. The female genitalia were located on the proximal posterior third of the deformed limb. Following amputation of the hind limb, gross pathologic analysis revealed a duplication of the fibula, tarsal, and metatarsal bones, digits, and appendices. The supernumerary structures and female genitalia were concluded to represent a parasitic twin. As conjoined or parasitic twinning of non-identical twins is thought to be impossible, the presence of genitalia of opposite phenotypic sex appeared paradoxical. Polymerase chain reaction analyses were therefore performed to determine the genotypic sex of both animals, which revealed the presence of the Y chromosome in all tissues, including the female genitalia. The non-masculinization of the external genitalia in the parasitic twin was presumed to be the result of an embryonic developmental defect. On this basis, a diagnosis of atypical caudal duplication (parasitic twinning) with phenotypic sex reversal was made.

Partially redundant functions of Adamts1 and Adamts4 in the perinatal development of the renal medulla

Adamts4 encodes a widely-expressed proteinase thought to be involved in processes ranging from cartilage metabolism to ovarian follicle development. To study its physiological roles, Adamts4-null mice were created by gene targeting. Unexpectedly, these were found to be phenotypically normal, suggesting that other gene(s) may compensate for its loss. Adamts4(-/-) mice were, therefore, crossed with a strain lacking Adamts1, whose pattern of expression and substrate specificity overlap that of Adamts4. Most (>95%) Adamts1(-/-) ;Adamts4(-/-) mice died within 72 hr after birth with a marked thinning of the renal medulla. The renal defect was not observed in embryonic Adamts1(-/-) ;Adamts4(-/-) kidneys, but became apparent around birth. The few (<5%) Adamts1(-/-) ;Adamts4(-/-) animals to reach adulthood had the same renal phenotype seen in newborns. This study is thus the first to report Adamts4 expression and function in the mammalian kidney, and to demonstrate that Adamts1 and Adamts4 play redundant and essential roles in perinatal kidney development.

Abstract 3193: Valosin containing protein (VCP) is a potential novel serum marker for ovarian cancer

The measurement of various serum markers (estradiol, inhibin, MIS) is often performed as an ancillary diagnostic technique for ovarian granulosa cell tumor (GCT), and is widely used for postoperative surveillance for disease recurrence. However, both the sensitivity and specificity of these markers has been repeatedly questioned, and a truly reliable serum marker for GCT has yet to be identified. We have recently developed the Ctnnb1tm1Mmt/+;Ptentm1Hwu/tm1Hwu;Amhr2tm3(cre)Bhr/+ (CPA) transgenic mouse model, which features genetic modifications that mimic pathologically relevant genetic lesions and signaling processes that occur in GCT in women. CPA mice develop anaplastic, highly aggressive GCTs that can spread both by forming distant metastases and by seeding into the peritoneal cavity, which are the main modes of GCT dissemination in women. Due to the biological similarities between GCT in women and in CPA mice, we hypothesized that the CPA model could be used in a translational approach to identify novel serum markers for GCT. To test this, granulosa cells from control mice and GCT cells from CPA mice were placed in culture, and differential secretion or shedding of proteins into the culture supernatant was analyzed by SDSPAGE and silver staining. Proteins bands present in the experimental samples but absent (or present at much lower levels) in control media were isolated from the gels and identified by tryptic digestion followed by LC/MS/MS analyses. By this method, VCL, VCP, HSPA4, HSP90A, HSP70, SPARC, WIF1, CTSB, FAM3C, TIMP2, CFL2 and B2M were found to be selectively secreted/shed by CPA GCT cells. An in vivo validation step was then performed to determined if these proteins were overexpressed in the serum of CPA mice relative to controls. Western blotting showed that CPA mice had elevated (P&lt;0.05) serum levels of VCP, HSP4, CTSB, TIMP2 and B2M. The latter proteins were therefore tested as potential serum diagnostic markers for GCT in a small cohort of women with GCT (n=10) and healthy women (n=7), as well as in patients with ovarian epithelial carcinomas (n=8) to provide an initial assessment of marker specificity. Of the proteins tested, mean serum levels of Valosin Containing Protein (VCP) were found to be over 9-fold higher in women with GCT or ovarian carcinoma relative to healthy women (P&lt;0.01) by western blotting. Furthermore, 90% of women with GCT and 100% of women with ovarian carcinomas had serum VCP levels above the highest level measured in the reference group. While these results indicate that VCP is unlikely to serve as a GCT-specific serum marker, it may nonetheless provide a valuable tool for the diagnosis of ovarian cancer. Analyses of larger cohorts will be required to determine the sensitivity, specificity and predictive values of VCP measurement for various forms and stages of ovarian cancer, as well as to determine if non-ovarian cancers also affect serum VCP levels.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3193. doi:10.1158/1538-7445.AM2011-3193