Immunohistochemistry for YAP1 N-terminus and C-terminus highlights metaplastic thymoma and high-grade thymic epithelial tumors by different staining patterns.

Metaplastic thymoma (MT), a rare subtype of thymic epithelial tumors (TETs), harbors YAP1::MAML2 fusions. Poroma, a skin tumor, also carries these fusions and exhibits a unique staining pattern for YAP1 immunohistochemistry (IHC), namely, a YAP1 N-terminus (YAP1[N])-positive but YAP1 C-terminus (YAP1[C])-negative pattern. In this context, MT was recently reported to lack YAP1(C) expression exclusively among TET subtypes. However, a lack of information about YAP1(N) expression in that study and another report that wild-type YAP1 expression was diminished in type B3 thymoma and thymic carcinoma warrants further studies for YAP1 expression in TETs. Thus, we immunohistochemically examined YAP1(N) and YAP1(C) staining patterns in our TET samples, including 14 cases of MT. In addition, 11 of the 14 MT cases were genetically analyzed with the formalin-fixed paraffin-embedded tissues if they harbored YAP1::MAML2 fusions. MT consistently exhibited YAP1(N)-positive and YAP(C)-negative staining, whereas type B3 thymoma and thymic carcinoma showed relatively heterogeneous staining patterns for YAP1(N) and YAP1(C) and were sometimes negative for both antibodies. Furthermore, a lower expression of YAP1 was found in type B3 compared to B2 thymomas. Among genetically analyzed 11 MT cases, 6 cases showed YAP1::MAML2 fusions, whereas the analysis failed in 5 very old cases due to poor RNA quality. These results indicate that IHC of both YAP1(N) and YAP1(C) is recommended to obtain staining patterns almost unique to MT. The biological significance of YAP1 in high-grade TETs warrants further investigation.

Urolithin A attenuates hexavalent chromium-induced small intestinal injury by modulating PP2A/Hippo/YAP1 pathway.

Hexavalent chromium (Cr(VI)) exposure has been linked with gastrointestinal toxicity, whereas the molecular pathways and key targets remain elusive. Computational toxicology analysis predicted the correlation between protein phosphatase 2A (PP2A) and genes regarding Cr(VI)-induced intestinal injury. Here, we generated a mouse model with intestinal epithelium-specific knock-out of Ppp2r1a (encoding PP2A Aα subunit) to investigate the mechanisms underlying Cr(VI)-induced small intestinal toxicity. Heterozygous mice (HE) and matched wild-type (WT) littermates were administrated with Cr(VI) at 0, 5, 20, 80 mg/L for 28 successive days. Cr(VI) treatment led to crypt hyperplasia, epithelial cell apoptosis, and intestinal barrier dysfunction, accompanied by the decline of goblet cell counts and Occludin expression in WT mice. Notably, these effects were aggravated in HE mice, indicating that PP2A Aα deficiency conferred mice with susceptibility to Cr(VI)-induced intestinal injury. Integrated data analysis and biological experiments revealed Cr(VI) exposure could decrease YAP1 phosphorylation at Ser127 but increase protein expression and activity, together with elevated TAZ protein driving epithelial crypt cells proliferation following damage, suggesting the involvement of Hippo/YAP1 signaling pathway in Cr(VI)-induced intestinal toxicity. Nevertheless, the enhanced phosphorylation of YAP1 in HE mice resulted in proliferation/repair defects in intestinal epithelium, thereby exacerbating Cr(VI)-induced gut barrier dysfunction. Notably, by molecular docking and further studies, we identified Urolithin A, a microbial metabolite, attenuated Cr(VI)-induced disruption of intestinal barrier function, partly by modulating YAP1 expression and activity. Our findings reveal the novel molecular pathways participated in Cr(VI)-caused small intestinal injury and urolithin A could potentially protect against environmental hazards-induced intestinal diseases.

A novel mechanism of ferroptosis inhibition-enhanced atherosclerotic plaque stability: YAP1 suppresses vascular smooth muscle cell ferroptosis through GLS1.

Atherosclerosis is a leading cause of cardiovascular diseases (CVDs), often resulting in major adverse cardiovascular events (MACEs), such as myocardial infarction and stroke due to the rupture or erosion of vulnerable plaques. Ferroptosis, an iron-dependent form of cell death, has been implicated in the development of atherosclerosis. Despite its involvement in CVDs, the specific role of ferroptosis in atherosclerotic plaque stability remains unclear. In this study, we confirmed the presence of ferroptosis in unstable atherosclerotic plaques and demonstrated that the ferroptosis inhibitor ferrostatin-1 (Fer-1) stabilizes atherosclerotic plaques in apolipoprotein E knockout (Apoe-/-) mice. Using bioinformatic analysis combining RNA sequencing (RNA-seq) with single-cell RNA sequencing (scRNA-seq), we identified Yes-associated protein 1 (YAP1) as a potential key regulator of ferroptosis in vascular smooth muscle cells (VSMCs) of unstable plaques. In vitro, we found that YAP1 protects against oxidized low-density lipoprotein (oxLDL)-induced ferroptosis in VSMCs. Mechanistically, YAP1 exerts its anti-ferroptosis effects by regulating the expression of glutaminase 1 (GLS1) to promote the synthesis of glutamate (Glu) and glutathione (GSH). These findings establish a novel mechanism where the inhibition of ferroptosis promotes the stabilization of atherosclerotic plaques through the YAP1/GLS1 axis, attenuating VSMC ferroptosis. Thus, targeting the YAP1/GLS1 axis to suppress VSMC ferroptosis may represent a novel strategy for preventing and treating unstable atherosclerotic plaques.

Disrupting YAP1-mediated glutamine metabolism induces synthetic lethality alongside ODC1 inhibition in osteosarcoma.

PURPOSE: Osteosarcoma, a highly malignant primary bone tumor primarily affecting adolescents, frequently develops resistance to initial chemotherapy, leading to metastasis and limited treatment options. Our study aims to uncover novel therapeutic targets for metastatic and recurrent osteosarcoma. METHODS: In this study, we proved the potential of modulating the YAP1-regulated glutamine metabolic pathway to augment the response of OS to DFMO. We initially employed single-cell transcriptomic data to gauge the activation level of polyamine metabolism in MTAP-deleted OS patients. This was further substantiated by transcriptome sequencing data from recurrent and non-recurrent patient tissues, confirming the activation of polyamine metabolism in progressive OS. Through high-throughput drug screening, we pinpointed CIL56, a YAP1 inhibitor, as a promising candidate for a combined therapeutic strategy with DFMO. In vivo, we utilized PDX and CDX models to validate the therapeutic efficacy of this drug combination. In vitro, we conducted western blot analysis, qPCR analysis, immunofluorescence staining, and PuMA experiments to monitor alterations in molecular expression, distribution, and tumor metastasis capability. We employed CCK-8 and colony formation assays to assess the proliferative capacity of cells in the experimental group. We used flow cytometry and reactive oxygen probes to observe changes in ROS and glutamine metabolism within the cells. Finally, we applied RNA-seq in tandem with metabolomics to identify metabolic alterations in OS cells treated with a DFMO and CIL56 combination. This enabled us to intervene and validate the role of the YAP1-mediated glutamine metabolic pathway in DFMO resistance. RESULTS: Through single-cell RNA-seq data analysis, we pinpointed a subset of late-stage OS cells with significantly upregulated polyamine metabolism. This upregulation was further substantiated by transcriptomic profiling of recurrent and non-recurrent OS tissues. High-throughput drug screening revealed a promising combination strategy involving DFMO and CIL56. DFMO treatment curbs the phosphorylation of YAP1 protein in OS cells, promoting nuclear entry and initiating the YAP1-mediated glutamine metabolic pathway. This reduces intracellular ROS levels, countering DFMO's anticancer effect. The therapeutic efficacy of DFMO can be amplified both in vivo and in vitro by combining it with the YAP1 inhibitor CIL56 or the glutaminase inhibitor CB-839. This underscores the significant potential of targeting the YAP1-mediated glutamine metabolic pathway to enhance efficacy of DFMO. CONCLUSION: Our findings elucidate YAP1-mediated glutamine metabolism as a crucial bypass mechanism against DFMO, following the inhibition of polyamine metabolism. Our study provides valuable insights into the potential role of DFMO in an "One-two Punch" therapy of metastatic and recurrent osteosarcoma.

Interference with ENO2 promotes ferroptosis and inhibits glycolysis in clear cell renal cell carcinoma by regulating Hippo­YAP1 signaling.

Glycolytic enzyme enolase 2 (ENO2) is dysregulated in various cancer types. Nevertheless, the role and underlying mechanism of ENO2 in clear cell renal cell carcinoma (ccRCC) remain unclear. Therefore, the current study investigated the effect and mechanism of ENO2 in ccRCC. ENO2 expression in a ccRCC cell line was assessed using reverse transcription-quantitative PCR and western blotting. Analysis of glycolysis was performed by estimating the extracellular acidification rate, lactic acid concentration, glucose uptake and the expression of glucose transporter 1, pyruvate kinase muscle isozyme M2 and hexokinase 2. Moreover, ferroptosis was assessed by detecting the level of total iron, lipid peroxide, reactive oxygen species and the expression of ferroptosis-related protein. In addition, mitochondrial function was assessed using JC-1 staining and detection kits. The results indicated that ENO2 is expressed at high levels in ccRCC cell lines, and interference with ENO2 expression inhibits glycolysis, promotes ferroptosis and affects mitochondrial function in ccRCC cells. Further investigation demonstrated that interference with ENO2 expression affected ferroptosis levels in ccRCC cells by inhibiting the glycolysis process. Mechanistically, the present results indicated that ENO2 may affect ferroptosis, glycolysis and mitochondrial functions by regulating Hippo-yes-associated protein 1 (YAP1) signaling in ccRCC cells. In conclusion, the present study showed that ENO2 affects ferroptosis, glycolysis and mitochondrial functions in ccRCC cells by regulating Hippo-YAP1 signaling, hence demonstrating its potential as a therapeutic target in ccRCC.

Targeting the Hippo/YAP1 signaling pathway in hepatocellular carcinoma: From mechanisms to therapeutic drugs (Review).

The Hippo signaling pathway plays a pivotal role in regulating cell growth and organ size. Its regulatory effects on hepatocellular carcinoma (HCC) encompass diverse aspects, including cell proliferation, invasion and metastasis, tumor drug resistance, metabolic reprogramming, immunomodulatory effects and autophagy. Yes­associated protein 1 (YAP1), a potent transcriptional coactivator and a major downstream target tightly controlled by the Hippo pathway, is influenced by various molecules and pathways. The expression of YAP1 in different cell types within the liver tumor microenvironment exerts varying effects on tumor outcomes, warranting careful consideration. Therefore, research on YAP1­targeted therapies merits attention. This review discusses the composition and regulation mechanism of the Hippo/YAP1 signaling pathway and its relationship with HCC, offering insights for future research and cancer prevention strategies.

Knockdown of YAP1 Reduces YTHDF3 to Stabilize SMAD7 and thus Inhibit Bladder Cancer Stem Cell Stemness.

BACKGROUND: The previous study has proved the oncogenic role of Yes-associated protein 1 (YAP1) in bladder cancer (BLCA), thus this study focused on its impact on bladder cancer stem cells (BCSCs) and underlying mechanism. METHOD: BCSCs were obtained by treating human BLCA cells UMUC3 with cisplatin and identified by measuring CD133+ in UMUC3/BCSCs via flow cytometry. YAP1 interaction proteins and mothers against decapentaplegic homolog 7 (SMAD7) N6-methyladenosine (m6A) site were analyzed by bioinformatics. BCSCs were transfected. SMAD7 m6A level, YTH domain-containing family proteins 3 (YTHDF3)-SMAD7 interaction, YAP1/YTHDF3 expression in BCSCs were assessed by methylated RNA immunoprecipitation (MeRIP), RNA immunoprecipitation (RIP) or quantitative reverse transcription PCR (qRT-PCR), respectively. BCSC proliferation was detected by 5-Bromo-2-deoxyuridine (BrdU) staining. UMUC3/BCSC migration/invasion and tumour sphere formation were determined by Transwell or tumour sphere formation assays. YAP1/YTHDF3/SMAD7/transforming growth factor (TGF)-ß1/stemness marker expressions in UMUC3/BCSCs were measured by Western blot assay. RESULT: BCSCs showed higher CD133+ ratio, expressions of stemness marker/YAP1/YTHDF3/TGF-ß1, lower SMAD7 expression and greater invasion/migration/tumour sphere formation capabilities than UMUC3 cells. YAP1 knockdown decreased SMAD7 m6A level and impaired YTHDF3-SMAD7 interaction in BCSCs. YAP1 silencing inhibited cell growth/invasiveness/migration/tumour sphere formation and stemness-associated protein/YTHDF3/TGF-ß1 expressions while upregulating SMAD7 expression in BCSCs, which was offset by YTHDF3 overexpression. CONCLUSION: The silencing of YAP1 in BCSCs impedes the YTHDF3-mediated degradation of m6A-modified SMAD7, culminating in diminished cell stemness.

Hypoxia-enhanced YAP1-EIF4A3 interaction drives circ_0007386 circularization by competing with CRIM1 pre-mRNA linear splicing and promotes non-small cell lung cancer progression.

BACKGROUND: The progression of non-small cell lung cancer (NSCLC) is significantly influenced by circular RNAs (circRNAs), especially in tumor hypoxia microenvironment. However, the precise functions and underlying mechanisms of dysregulated circRNAs in NSCLC remain largely unexplored. METHODS: Differentially expressed circRNAs in NSCLC tissues were identified through high-throughput RNA sequencing. The characteristics of circ_0007386 were rigorously confirmed via Sanger sequencing, RNase R treatment and actinomycin D treatment. The effects of circ_0007386 on proliferation and apoptosis were investigated using CCK8, cloning formation assays, TUNEL staining, and flow cytometry assays in vitro. In vivo, xenograft tumor models were used to evaluate its impact on proliferation. Mechanistically, the regulatory relationships of circ_0007386, miR-383-5p and CIRBP were examined through dual luciferase reporter assays and rescue experiments. Additionally, we detected the binding of EIF4A3 to CRIM1 pre-mRNA by RNA immunoprecipitation and the interaction between YAP1 and EIF4A3 under hypoxic conditions by co-immunoprecipitation. RESULTS: Our investigation revealed a novel circRNA, designated as circ_0007386, that was upregulated in NSCLC tissues and cell lines. Circ_0007386 modulated proliferation and apoptosis in NSCLC both in vitro and in vivo. Functionally, circ_0007386 acted as a sponge for miR-383-5p, targeting CIRBP, which influenced NSCLC cell proliferation and apoptosis via the PI3K/AKT signaling pathway. Furthermore, under hypoxic conditions, the interaction between YAP1 and EIF4A3 was enhanced, leading to the displacement of EIF4A4 from binding to CRIM1 pre-mRNA. This facilitated the back-splicing of CRIM1 pre-mRNA, increasing the formation of circ_0007386. The circ_0007386/miR-383-5p/CIRBP axis was significantly associated with the clinical features and prognosis of NSCLC patients. CONCLUSIONS: Circ_0007386, regulated by YAP1-EIF4A3 interaction under hypoxia conditions, plays an oncogenic role in NSCLC progression via the miR-383-5p/CIRBP axis.

Implications of the Hippo Pathway Dysregulation in Uterine Leiomyosarcoma.

BACKGROUND/AIM: Uterine leiomyosarcomas (uLMS) are the most common mesenchymal tumors of the female genital tract. uLMS genetics encompass complex karyotypes with no specific molecular alterations. The Hippo pathway has been implicated in the pathogenesis of epithelioid hemangio-endotheliomas and endometrial sarcomas. Hippo pathway effectors are YAP1 and TAZ co-transcriptional factors. PATIENTS AND METHODS: We studied Hippo pathway in a series of 32 uLMS patients and its association with clinicopathological parameters. MATERIALS AND METHODS: Immunohistochemical analysis of YAP1 and TAZ proteins accompanied with fluorescent in situ hybridization study of YAP1 gene was performed in patient samples. Age, sex, tumor size, stage at the time of diagnosis and treatment have been analyzed. Overall survival (OS) was calculated from the time of diagnosis until death, loss of follow up or data cut-off. RESULTS: Hippo signaling was found to be dysregulated in 20 (62.5%) patients with uLMS. Regarding OS we detected a trend of Hippo deregulation, designating it as a positive prognostic factor. CONCLUSION: The Hippo pathway is implicated in uLMS oncogenesis, since nuclear expression of YAP1 was detected in 17 (53.1%) of the 32 patients with immunohistochemistry and YAP1 amplification was found in 8 (25%) patients.

CL429 enhances the renewal of intestinal stem cells by upregulating TLR2-YAP1.

Intestinal stem cells (ISCs) play a crucial role in maintaining the equilibrium and regenerative potential of intestinal tissue, thereby ensuring tissue homeostasis and promoting effective tissue regeneration following injury. It has been proven that targeting Toll-like receptors (TLRs) can help prevent radiation-induced damage to the intestine. In this study, we established an intestinal injury model using IR and evaluated the effects of CL429 on ISC regeneration both in vivo and in vitro. Following radiation exposure, mice treated with CL429 showed a significant increase in survival rates (100% survival in the treated group compared to 54.54% in the control group). CL429 also showed remarkable efficacy in inhibiting radiation-induced intestinal damage and promoting ISC proliferation and regeneration. In addition, CL429 protected intestinal organoids against IR-induced injury. Mechanistically, RNA sequencing and Western blot analysis revealed the activation of the Wnt and Hippo signaling pathways by CL429. Specifically, we observed a significant upregulation of YAP1, a key transcription factor in the Hippo pathway, upon CL429 stimulation. Furthermore, knockdown of YAP1 significantly attenuated the radioprotective effect of CL429 on intestinal organoids, indicating that CL429-mediated intestinal radioprotection is dependent on YAP1. In addition, we investigated the relationship between TLR2 and YAP1 using TLR2 knockout mice, and our results showed that TLR2 knockout abolished the activation of CL429 on YAP1. Taken together, our study provides evidence supporting the role of CL429 in promoting ISC regeneration through activation of TLR2-YAP1. And further investigation of the interaction between TLRs and other signaling pathways may enhance our understanding of ISC regeneration after injury.

YAP1-mediated dysregulation of ACE-ACE2 activity augments cardiac fibrosis upon induction of hyperglycemic stress.

BACKGROUND: Diabetic stress acts on the cardiac tissue to induce cardiac hypertrophy and fibrosis. Diabetes induced activated renin angiotensin system (RAS) has been reported to play a critical role in mediating cardiac hypertrophy and fibrosis. Angiotensin converting enzyme (ACE) in producing Angiotensin-II, promotes cardiomyocyte hypertrophy and fibrotic damage. ACE2, a recently discovered molecule structurally homologous to ACE, has been reported to be beneficial in reducing the effect of RAS driven pathologies. METHODS: In vivo diabetic mouse model was used and co-labelling immunostaining assay have been performed to analyse the fibrotic remodeling and involvement of associated target signaling molecules in mouse heart tissue. For in vitro analyses, qPCR and western blot experiments were performed in different groups for RNA and protein expression analyses. RESULTS: Fibrosis markers were observed to be upregulated in the diabetic mouse heart tissue as well as in high glucose treated fibroblast and cardiomyocyte cells. Hyperglycemia induced overexpression of YAP1 leads to increased expression of ß-catenin (CTNNB1) and ACE with downregulated ACE2 expression. The differential expression of ACE/ACE2 promotes TGFB1-SMAD2/3 pathway in the hyperglycemic cardiomyocyte and fibroblast resulting in increased cardiac fibrotic remodeling. CONCLUSION: In the following study, we have reported YAP1 modulates the RAS signaling pathway by inducing ACE and inhibiting ACE2 activity to augment cardiomyocyte hypertrophy and fibrosis in hyperglycemic condition. Furthermore, we have shown that hyperglycemia induced dysregulation of ACE-ACE2 activity by YAP1 promotes cardiac fibrosis through ß-catenin/TGFB1 dependent pathway.

NEDD8 enhances Hippo signaling by mediating YAP1 neddylation.

The Hippo-YAP signaling pathway plays a central role in many biological processes such as regulating cell fate, organ size, and tissue growth, and its key components are spatiotemporally expressed and posttranslationally modified during these processes. Neddylation is a posttranslational modification that involves the covalent attachment of NEDD8 to target proteins by NEDD8-specific E1-E2-E3 enzymes. Whether neddylation is involved in Hippo-YAP signaling remains poorly understood. Here, we provide evidence supporting the critical role of NEDD8 in facilitating the Hippo-YAP signaling pathway by mediating neddylation of the transcriptional coactivator yes-associated protein 1 (YAP1). Overexpression of NEDD8 induces YAP1 neddylation and enhances YAP1 transactivity, but inhibition of neddylation suppresses YAP1 transactivity and attenuates YAP1 nuclear accumulation. Furthermore, inhibition of YAP1 signaling promotes MLN4924-induced ovarian granulosa cells apoptosis and disruption of nedd8 in zebrafish results in downregulation of yap1-activated genes and upregulation of yap1-repressed genes. Further assays show that the xiap ligase promotes nedd8 conjugates to yap1 and that yap1 neddylation. In addition, we identify lysine 159 as a major neddylation site on YAP1. These findings reveal a novel mechanism for neddylation in the regulation of Hippo-YAP signaling.

PTX3 promotes cementum formation and cementoblast differentiation via HA/ITGB1/FAK/YAP1 signaling pathway.

Cementum is a vital component of periodontium, yet its regeneration remains a challenge. Pentraxin 3 (PTX3) is a multifunctional glycoprotein involved in extracellular matrix remodeling and bone metabolism regulation. However, the role of PTX3 in cementum formation and cementoblast differentiation has not been elucidated. In this study, we initially observed an increase in PTX3 expression during cementum formation and cementoblast differentiation. Then, overexpression of PTX3 significantly enhanced the differentiation ability of cementoblasts. While conversely, PTX3 knockdown exerted an inhibitory effect. Moreover, in Ptx3-deficient mice, we found that cementum formation was hampered. Furthermore, we confirmed the presence of PTX3 within the hyaluronan (HA) matrix, thereby activating the ITGB1/FAK/YAP1 signaling pathway. Notably, inhibiting any component of this signaling pathway partially reduced the ability of PTX3 to promote cementoblast differentiation. In conclusion, our study indicated that PTX3 promotes cementum formation and cementoblast differentiation, which is partially dependent on the HA/ITGB1/FAK/YAP1 signaling pathway. This research will contribute to our understanding of cementum regeneration after destruction.

Dihydroartemisinin modulated arachidonic acid metabolism and mitigated liver inflammation by inhibiting the activation of 5-LOX and COX-2.

Background: Dihydroartemisinin (DHA), a derivative of Artemisia annua, has been shown to possess anti-inflammatory properties. Besides, Yes-associated protein 1 (YAP1) plays a crucial role in maintaining liver homeostasis. Methods: This study used Yap1 Flox/Flox, Albumin-Cre mice with hepatocyte-specific Yap1 knockout (referred to as Yap1 LKO) and their control mice (Yap1 Flox/Flox, referred to as Yap1 Flox). The effect of Yap1 on lipid metabolism homeostasis was investigated through non-targeted metabolomic analysis of mouse liver. Subsequently, DHA was administered to Yap1 LKO mice to assess its potential as a treatment. Liver pathology was evaluated via H&E staining, and the levels of AST, ALT, and TG were quantified using biochemical assays. The contents of arachidonic acid (AA), prostaglandin E1 (PGE1), and leukotrienes (LT) in the liver were measured using ELISA, while the protein expressions of PLIN2, 5-lipoxygenase (5-LOX), and cyclooxygenase-2 (COX-2) were analyzed through IHC staining. Results: Hepatocyte-specific Yap1 knockout activated the AA metabolic pathway, resulting in increased elevated levels of AA, PGE1, and LT levels, along with inflammatory cytokine infiltration. DHA mitigated the elevation of metabolites such as PGE1 and LT caused by the AA metabolic pathway activation by down-regulating the levels of COX-2 and 5-LOX in the liver of Yap1 LKO mice. Moreover, it alleviated the accumulation of lipid vacuoles and reduced triglyceride (TG) and perilipin-2 (PLIN2) levels in the liver of Yap1 LKO mice. Conclusions: Excessively low YAP1 expression induces liver inflammation and disturbances in lipid metabolism, whereas DHA modulated AA metabolism and mitigated liver inflammation by inhibiting the activation of 5-LOX and COX-2.

RHBDF1 modulates cisplatin sensitivity of small cell lung cancer through YAP1/Smad2 signaling pathway.

Small cell lung cancer (SCLC) is a fatal tumor type that is prone to drug resistance. In our previous study, we showed that human rhomboid-5 homolog-1 (RHBDF1) was differentially expressed in 5 intrinsic cisplatin-resistant SCLC tissues compared with 5 intrinsic cisplatin-sensitive SCLC tissues by RNA sequencing, which intrigued us. We performed gain- and loss-of-function experiments to investigate RHBDF1 function, bioinformatics analysis, qRT-PCR, western blotting, and immunoprecipitation to elucidate the molecular mechanisms as well as detect RHBDF1 expression in SCLC by immunohistochemistry. We found that RHBDF1 knockdown promoted cell proliferation and cisplatin chemoresistance and inhibited apoptosis in vitro and in vivo. These effects could be reversed by overexpressing RHBDF1 in vitro. Mechanistically, RHBDF1 interacted with YAP1, which increased the phosphorylation of Smad2 and transported Smad2 to the nucleus. Among clinical specimens, the RHBDF1 was a low expression in SCLC and was associated with clinicopathological features and prognosis. We are the first to reveal that RHBDF1 inhibited cell proliferation and promoted cisplatin sensitivity in SCLC and elucidate a novel mechanism through RHBDF1/YAP1/Smad2 signaling pathway which played a crucial role in cisplatin chemosensitivity. Targeting this pathway can be a promising therapeutic strategy for chemotherapy resistance in SCLC.

Blastocyst-like Structures in the Peripheral Retina of Young Adult Beagles.

In this immunohistological study on the peripheral retina of 3-year-old beagle dogs, excised retina specimens were immunostained with antibodies against nestin, Oct4, Nanog, Sox2, CDX2, cytokeratin 18 (CK 18), RPE65, and YAP1, as well as hematoxylin and DAPI, two nuclear stains. Our findings revealed solitary cysts of various sizes in the inner retina. Intriguingly, a mass of small round cells with scant cytoplasms was observed in the cavity of small cysts, while many disorganized cells partially occupied the cavity of the large cysts. The small cysts were strongly positive for nestin, Oct4, Nanog, Sox2, CDX2, CK18, and YAP1. RPE65-positive cells were exclusively observed in the tissue surrounding the cysts. Since RPE65 is a specific marker of retinal pigment epithelial (RPE) cells, the surrounding cells of the peripheral cysts were presumably derived from RPE cells that migrated intraretinally. In the small cysts, intense positive staining for nestin, a marker of retinal stem cells, seemed to indicate that they were derived from retinal stem cells. The morphology and positive staining for markers of blastocyst and RPE cells indicated that the small cysts may have formed structures resembling the blastocyst, possibly caused by the interaction between retinal stem cells and migrated RPE cells.

Single-cell RNA-seq reveals the role of YAP1 in prefrontal cortex microglia in depression.

BACKGROUND: Depression is a complex mood disorder whose pathogenesis involves multiple cell types and molecular pathways. The prefrontal cortex, as a key brain region for emotional regulation, plays a crucial role in depression. Microglia, as immune cells of the central nervous system, have been closely linked to the development and progression of depression through their dysfunctional states. This study aims to utilize single-cell RNA-seq technology to reveal the pathogenic mechanism of YAP1 in prefrontal cortex microglia in depression. METHODS: Firstly, we performed cell type identification and differential analysis on normal and depressed prefrontal cortex tissues by mining single-cell RNA-seq datasets from public databases. Focusing on microglia, we conducted sub-clustering, differential gene KEGG enrichment analysis, intercellular interaction analysis, and pseudotime analysis. Additionally, a cross-species analysis was performed to explore the similarities and differences between human and rhesus monkey prefrontal cortex microglia. To validate our findings, we combined bulk RNA-Seq and WGCNA analysis to reveal key genes associated with depression and verified the relationship between YAP1 and depression using clinical samples. RESULTS: Our study found significant changes in the proportion and transcriptional profiles of microglia in depressed prefrontal cortex tissues. Further analysis revealed multiple subpopulations of microglia and their associated differential genes and signaling pathways related to depression. YAP1 was identified as a key molecule contributing to the development of depression and was significantly elevated in depression patients. Moreover, the expression level of YAP1 was positively correlated with HAMD scores, suggesting its potential as a biomarker for predicting the onset of depression. CONCLUSION: This study utilized single-cell RNA-seq technology to reveal the pathogenic mechanism of YAP1 in prefrontal cortex microglia in depression, providing a new perspective for a deeper understanding of the pathophysiology of depression and identifying potential targets for developing novel treatment strategies.

Hide-and-Seek With Spindle-Cell-Component-Poor Metaplastic Thymoma.

Metaplastic thymoma is a rare biphasic thymic tumor with indolent behavior and recurrent YAP1::MAML2 gene rearrangement. Although the diagnosis of this tumor is usually straightforward based on hematoxylin and eosin (H&E) findings alone, cases with scant spindle-cell ("pseudosarcomatous stroma") components can be easily confused with more commonly occurring type A thymoma. We present a case of metaplastic thymoma with a sparse stroma-like spindle-cell component, discussing its histological and immunohistochemical hints and drawing attention to the visual similarity to type A thymoma. This is also the first published case of metaplastic thymoma with associated psoriasis.

RNF144A-AS1 stabilizes TAF15 and promotes malignant biological behaviors of skin cutaneous melanoma.

LncRNAs have been demonstrated to regulate biological processes in malignant tumors. In our previous study, we identified the immune-related LncRNA RNF144A-AS1 as a potential regulator in SKCM. However, its precise function and regulatory mechanism remain unclear. In this study, we observed upregulation of RNF144A-AS1 in SKCM and found that knockdown of RNF144A-AS1 suppressed proliferation, migration, invasion, and epithelial-mesenchymal transition abilities of melanoma cells. Mechanistically, as a high-risk prognostic factor, RNF144A-AS1 regulated biological processes of SKCM by interacting with TAF15 through an RNA-binding protein-dependent (RBP-dependent) manner. Furthermore, we confirmed that TAF15 activated downstream transcriptional regulation of YAP1 to modulate malignant behaviors in melanoma cells. In vivo experiments revealed that knockdown of RNF144A-AS1 inhibited tumorigenic capacity of melanoma cells and exhibited promising therapeutic effects. Collectively, these findings highlight the significance of the RNF144A-AS1/TAF15/YAP1 axis in promoting malignant behaviors in SKCM and provide novel insights into potential prognostic biomarkers and therapeutic targets for this disease.

Human trophoblast invasion and migration are mediated by the YAP1-CCN1 pathway: defective signaling in trophoblasts during early-onset severe preeclampsia.

The transcription coactivator YAP1 mediates the major effects of the Hippo signaling pathway. The CCN family is a small group of glycoproteins known to be downstream effectors of YAP1 in diverse tissues. However, whether CCN family members mediate the effects of YAP1 in human trophoblasts is unknown. In this study, placental expression of both YAP1 and CCN1 was found to be impaired in pregnancies complicated by early-onset severe preeclampsia (sPE). CCN1 was expressed not only in cytotrophoblasts, trophoblast columns and mesenchymal cells, similar to active YAP1, but also in syncytiotrophoblasts of normal first-trimester placental villi; moreover, decidual staining of active YAP1 and CCN1 was found in both interstitial and endovascular extravillous trophoblasts. In cultured immortalized human trophoblastic HTR-8/SVneo cells, knockdown of YAP1 decreased CCN1 mRNA and protein expression and led to impaired cell invasion and migration. Also, CCN1 knockdown negatively affected HTR-8/SVneo cell invasion and migration but not viability. YAP1 knockdown was further found to impair HTR-8/SVneo cell viability via G0/G1 cell cycle arrest and apoptosis, while CCN1 knockdown had minimal effect on cell cycle arrest and no effect on apoptosis. Accordingly, treatment with recombinant CCN1 partially reversed the YAP1 knockdown-induced impairment in trophoblast invasion and migration but not in viability. Thus, CCN1 mediates the effects of YAP1 on human trophoblast invasion and migration but not apoptosis, and decreased placental expression of YAP1 and CCN1 in pregnancies complicated by early-onset sPE might contribute to the pathogenesis of this disease.