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.

Cancer Spheroids Embedded in Tissue-Engineered Skin Substitutes: A New Method to Study Tumorigenicity In Vivo.

Tumorigenic assays are used during a clinical translation to detect the transformation potential of cell-based therapies. One of these in vivo assays is based on the separate injection of each cell type to be used in the clinical trial. However, the injection method requires many animals and several months to obtain useful results. In previous studies, we showed the potential of tissue-engineered skin substitutes (TESs) as a model for normal skin in which cancer cells can be included in vitro. Herein, we showed a new method to study tumorigenicity, using cancer spheroids that were embedded in TESs (cTES) and grafted onto athymic mice, and compared it with the commonly used cell injection assay. Tumors developed in both models, cancer cell injection and cTES grafting, but metastases were not detected at the time of sacrifice. Interestingly, the rate of tumor development was faster in cTESs than with the injection method. In conclusion, grafting TESs is a sensitive method to detect tumor cell growth with and could be developed as an alternative test for tumorigenicity.

A retrospective study of equine perinatal loss in Canada (2007 to 2020).

Objective: This study aims to identify the most common causes of equine perinatal loss up to 7 d of age in Canada. Animal: Equine. Procedure: Necropsy reports from 360 equine perinatal loss cases were acquired from provincial veterinary diagnostic labs across Canada. Each case was classified into a basic cause (noninfectious, infectious, or unidentified) of perinatal loss, then further classified into primary and secondary categories for analysis. Results: Of the basic causes of perinatal loss, noninfectious causes were the most common. Bacterial causes, such as septicemia, were the most common primary diagnosis overall. Actinobacillus was the most commonly identified bacterial species. Conclusion: This study showed similar results to those of studies conducted in other countries, including having similar etiologic agents identified. The high prevalence of thyroid hyperplasia identified in this study is notable and was not reported in other, similar retrospective studies, despite being reported in locations other than Canada. Clinical relevance: Perinatal loss can have important economic consequences for horse breeders; thus, identification of the most common causes is of interest to both veterinarians and breeders.

Étude rétrospective des décès périnataux équins au Canada (2007 à 2020). Objectif: Cette étude vise à identifier les causes les plus courantes de décès périnatal équin jusqu'à l'âge de 7 jours au Canada. Animal: Cheval. Procédure: Les rapports d'autopsie de 360 cas de décès périnatal équin ont été acquis auprès de laboratoires provinciaux de diagnostic vétérinaire à travers le Canada. Chaque cas a été classé selon une cause fondamentale (non infectieuse, infectieuse ou non identifiée) de décès périnatal, puis classé en catégories primaires et secondaires pour analyse. Résultats: Parmi les causes fondamentales de décès périnatal, les causes non infectieuses étaient les plus fréquentes. Les causes bactériennes, telles que la septicémie, étaient le diagnostic principal le plus courant dans l'ensemble. Actinobacillus était le genre bactérien le plus fréquemment identifié. Conclusion: Cette étude a montré des résultats similaires à ceux d'études menées dans d'autres pays, y compris l'identification d'agents étiologiques similaires. La forte prévalence de l'hyperplasie thyroïdienne identifiée dans cette étude est remarquable et n'a pas été signalée dans d'autres études rétrospectives similaires, bien qu'elle ait été signalée dans des endroits autres que le Canada. Pertinence clinique: Le décès périnatal peut entraîner des conséquences économiques importantes pour les éleveurs de chevaux; ainsi, l'identification des causes les plus courantes intéresse à la fois les vétérinaires et les éleveurs.(Traduit par Dr Serge Messier).

Is the Hippo Pathway Effector Yes-Associated Protein a Potential Key Player of Dairy Cattle Cystic Ovarian Disease Pathogenesis?

Cystic ovarian disease (COD) in dairy cattle is characterized by preovulatory follicles that become cysts, fail to ovulate and persist in the ovary; consequently, interfering with normal ovarian cyclicity. The intraovarian key players that orchestrate the alterations occurring in the preovulatory follicle and that culminate with cyst formation and persistence, however, remain uncertain. Interestingly, the Hippo pathway effector yes-associated protein (YAP) has been described in humans and mice as a key player of anovulatory cystic disorders. To start elucidating if YAP deregulation in ovarian follicle cells can be also involved in the pathogenesis of COD, we have generated a series of novel results using spontaneously occurring cystic follicles in cattle. We found that mRNA and protein levels of YAP are significantly higher in granulosa (GCs) and theca cells (TCs) isolated from cystic follicles (follicular structures of at least 20 mm in diameter) in comparison to respective cell types isolated from non-cystic large follicles (≥12 mm). In addition, immunohistochemistry and Western blot analyses used to determine YAP phosphorylation pattern suggest that YAP transcriptional activity is augmented is cystic GCs. These results were confirmed by a significant increase in the mRNA levels encoding for the classic YAP-TEAD transcriptional target genes CTGF, BIRC5 and ANKRD1 in GCs from follicle cysts in comparison to non-cystic large follicles. Taken together, these results provide considerable insight of a completely novel signaling pathway that seems to play an important role in ovarian cystic disease pathogenesis in dairy cattle.

T cell-loaded injectable chitosan scaffold shows short-term efficacy in localised cancer immunotherapy in mice.

Adoptive cell therapy (ACT) shows success against treatment-resistant cancers, but is limited by the large number of intravenously delivered T cells required and toxicity related to systemic administration. In this work, we hypothesized that localized T cell delivery in an in situ gelling chitosan hydrogel will allow similar treatment efficacy despite delivering fewer cells than systemic intravenous delivery. A rapidly gelling chitosan gel with good mechanical properties was used for this study. Gel biocompatibility and biodegradability were tested over 8 weeks in mice. No adverse effects were observed. The gel elicited a local granulomatous reaction (foreign body reaction), degrading by about 75% volume at 8 weeks. The survival, escape and bioactivity against the tumour cells of encapsulated murine lymphocytes (OT-I) and human Jurkat cells were confirmed in vitro by live/dead assay and flow cytometry. Efficacy was studied using a mouse tumour model where the injected OT-I can specifically recognize and attack ovalbumin (OVA) protein-expressing tumours. The OT-I cell delivery scaffold was compared to untreated controls, OT-I in saline and intravenous systemic treatment with 3-fold more OT-I, observing tumour growth and localization by intravital microscopy and histology. Gel-encapsulated OT-I limited tumour growth significantly up to 11 days after treatment compared to that of untreated mice and mice with longer PBS-suspended OT-I treatment (9 days), but slightly less than that of mice with IV-delivered OT-I treatment (14 days). No significant difference was observed when directly comparing the gel and IV treatments. Although further optimization of the treatment is required, this work shows the feasibility and potential of the chitosan gel for localised OT-I delivery in cancer immunotherapy.

Cannabinoid receptors are expressed in equine synovium and upregulated with synovitis.

BACKGROUND: Osteoarthritis (OA) is a major cause of equine lameness. Cannabinoid (CB) receptors are now considered to be promising therapeutic targets in human rheumatology for pain and inflammation, however, little is known about the equine endocannabinoid system. OBJECTIVES: The primary goal was to assess the presence and expression pattern of CB1 and CB2 in the synovium of healthy joints. A secondary goal was to explore the relationship between the CB expression, degree of synovitis and OA pathology. STUDY DESIGN: Ex vivo experimental study. METHODS: Metacarpophalangeal joints (n = 25) from a tissue bank were studied. The joints were dissected, and the articular cartilage lesions were scored. Synovial membrane specimens (n = 45) were harvested, fixed and the degree of synovitis was graded on histological sections. Colocalised synovial sections were also immunostained with antibodies to CB1 and CB2. Five regions of interest were randomly selected from digital images of manually segmented synovial intima and scored blindly for positive cellular immunoreactive staining by two independent observers. Interobserver agreement was calculated with an intraclass correlation coefficient (ICC). Relationships between CB1 and CB2 immunoreactive scores and synovitis or joint OA grade were explored with mixed linear models. RESULTS: CB1 was expressed in synovial intimal cells in all specimens studied whereas CB2 expression was identified in 94%. Both receptors were also expressed in the subintimal blood vessel walls. ICCs were 84.6% (CB1) and 92.9% (CB2) for the immunoreactivity scores. Both CB1 and CB2 expression were significantly upregulated (p = 0.04 and p = 0.03, respectively) with increasing degree of synovitis. Conversely, CB1 expression significantly decreased (p = 0.03) with increasing severity of OA. MAIN LIMITATIONS: The type of synovial cell expressing CB1 or CB2 was not investigated. CONCLUSION: Equine synovial intimal cells constitutively express both CB1 and CB2 receptors that are upregulated with synovitis and may have a role in joint pain. They are potential targets for therapy with cannabinoid molecules or their derivatives.

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 (Mst1 flox/flox ; Mst2 flox/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.

Targeted Disruption of Lats1 and Lats2 in Mice Impairs Testis Development and Alters Somatic Cell Fate.

Hippo signaling plays an essential role in the development of numerous tissues. Although it was previously shown that the transcriptional effectors of Hippo signaling Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) can fine-tune the regulation of sex differentiation genes in the testes, the role of Hippo signaling in testis development remains largely unknown. To further explore the role of Hippo signaling in the testes, 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 the somatic cells of the testes using an Nr5a1-cre strain (Lats1flox/flox;Lats2flox/flox;Nr5a1-cre). We report here that early stages of testis somatic cell differentiation were not affected in this model but progressive testis cord dysgenesis was observed starting at gestational day e14.5. Testis cord dysgenesis was further associated with the loss of polarity of the Sertoli cells and the loss of SOX9 expression but not WT1. In parallel with testis cord dysgenesis, a loss of steroidogenic gene expression associated with the appearance of myofibroblast-like cells in the interstitial space was also observed in mutant animals. Furthermore, the loss of YAP phosphorylation, the accumulation of nuclear TAZ (and YAP) in both the Sertoli and interstitial cell populations, and an increase in their transcriptional co-regulatory activity in the testes suggest that the observed phenotype could be attributed at least in part to YAP and TAZ. Taken together, our results suggest that Hippo signaling is required to maintain proper differentiation of testis somatic cells.

Energy balance and hippo effector activity in endometrium and corpus luteum of early pregnant ewes.

CONTEXT: The establishment of pregnancy in cows requires uterine activity regulation of the main Hippo signalling effector yes-associated protein 1 (YAP). It remains unknown (1) how YAP activity at the corpus luteum (CL) correlates with early pregnancy-related events in ruminants; and (2) if YAP activity in the uterus and CL can be affected by metabolic disorders that may lead to pregnancy failure in ruminants. AIMS AND METHODS: To determine the effect of early pregnancy on total and phospho-YAP expression and its transcriptional activity in the CL, we compared non-pregnant vs pregnant ewes. To understand the YAP activity dysregulation with disorders that may result in pregnancy loss, we induced negative energy balance in pregnant ewes. KEY RESULTS AND CONCLUSIONS: Our main results indicate that early pregnancy alters the expression and activity patterns of YAP in the ovine CL but not in the endometrium. In addition, while our NEB-induced model fails to alter YAP activity at the endometrium level, we found that fasting during the first but not second week of pregnancy affects YAP activity in the CL of pregnant ewes. IMPLICATIONS: The data presented herein provide considerable insight into the activity of a signalling pathway that may be a key player in pregnancy recognition and establishment in ewes.

A 13-year retrospective study of equine abortions in Canada.

Objective: The purpose of this study was to identify the most common causes of equine abortion in Canada, and to compare findings to similar reports from other countries. Animal: Equine. Procedure: Necropsy reports from 901 equine abortion cases were acquired from provincial veterinary diagnostic laboratories across Canada. The final diagnosis was classified into basic abortion causes (infectious, non-infectious, unknown) and into primary and secondary categories for analysis. Results: Non-infectious causes of abortion were the most frequently identified in Canada, with fetoplacental causes, including umbilical cord torsion or placental insufficiency, being the most common primary diagnosis category. Streptococcus and Escherichia were the bacterial species most often identified as causing infectious abortions, whereas equine herpesvirus-1 was implicated in all viral abortions identified. Conclusion: The high rate of non-infectious causes of abortion was similar to previous studies conducted in the United Kingdom. This finding was somewhat dissimilar to the USA, which had higher rates of infectious abortions, despite Canada's geographic proximity to the USA. The reason for variations among countries in equine abortion causes is unknown. Clinical relevance: The large number of fetoplacental-related abortions identified in this study emphasized the need for submission of both the fetus and placenta, if possible, to increase the probability of a diagnosis. In addition, the high rate of unidentified diagnoses suggests a need for further study into both non-infectious and infectious causes of equine abortion, including potential development of new diagnostic tests or markers.

Objectif: Le but de cette étude était d'identifier les causes les plus courantes d'avortement chez les équidés au Canada et de comparer les résultats à des rapports similaires provenant d'autres pays. Animal: Chevaux. Procédure: Les rapports de nécropsie de 901 cas d'avortements équins ont été obtenus auprès de laboratoires provinciaux de diagnostic vétérinaire à travers le Canada. Le diagnostic final a été classé en causes d'avortement de base (infectieuses, non infectieuses, inconnues) et en catégories primaires et secondaires pour analyse. Résultats: Les causes non-infectieuses d'avortement étaient les plus fréquemment identifiées au Canada, les causes foetoplacentaires, y compris la torsion du cordon ombilical ou l'insuffisance placentaire, étant la catégorie de diagnostic principal la plus courante. Les espèces bactériennes des genres Streptococcus et Escherichia étaient les plus souvent identifiées comme étant à l'origine d'avortements infectieux, alors que l'herpèsvirus équin-1 était impliqué dans tous les avortements viraux identifiés. Conclusion: Le taux élevé de causes non-infectieuses d'avortement était similaire aux études précédentes menées au Royaume-Uni. Cette observation était quelque peu différente de celles des États-Unis, qui avaient des taux plus élevés d'avortements infectieux, malgré la proximité géographique du Canada avec les États-Unis. La raison des variations entre les pays dans les causes d'avortement équin est inconnue. Pertinence clinique: Le grand nombre d'avortements liés aux causes foetoplacentaires identifiés dans cette étude a souligné la nécessité de soumettre à la fois le foetus et le placenta, si possible, pour augmenter la probabilité d'un diagnostic. En outre, le taux élevé de diagnostics non identifiés suggère la nécessité d'une étude plus approfondie des causes non-infectieuses et infectieuses de l'avortement équin, y compris le développement potentiel de nouveaux tests de diagnostic ou marqueurs.(Traduit par Dr Serge Messier).

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 Ctnnb1tm1Mmt/+; Ddx4-CreTr/+ (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.

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.

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.

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.

Mycobacterium xenopi systemic infection in a domestic fiery-shouldered conure bird (Pyrrhura egregia).

INTRODUCTION: Mycobacterium xenopi is a rare opportunistic pathogen mainly causing infections in immunocompromised human patients or those with underlying chronic structural lung disease. Cases of disease in veterinary medicine remain scarce. Few animal species, including birds, are suspected of being vectors of the disease and there has not yet been a report of clinical disease in birds. We report the first case, to our knowledge, of systemic infection in a domestic bird. CASE PRESENTATION: A female fiery-shouldered conure was submitted after death for necropsy following episodes of heavy breathing. The necropsy revealed multiple granulomatous lesions within the liver, air sacs and kidneys. Ziehl-Neelsen stains demonstrated the presence of numerous intralesional acid-fast bacilli. PCR assays and culture confirmed the presence of M. xenopi. CONCLUSION: Through this case we hope to describe the characteristics of M. xenopi disease in birds and the possible close relationship between animal and human infections.

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.