Renal tubule cells can recover after they undergo AKI (acute kidney injury). An incomplete repair of renal tubules can result in progressive fibrotic CKD (chronic kidney disease). Studies have revealed the relationship between tubular epithelial cells and kidney fibrogenesis. However, the underlying mechanism remains unclear. Hippo pathway components were evaluated in complete/incomplete repair of I/R (ischaemia/reperfusion) AKI rat models, HK-2 cells and AKI human renal biopsy samples. We found that the expression levels of the Hippo pathway components changed dynamically during kidney regeneration and fibrogenesis in rat models of I/R-induced AKI and human renal biopsy samples. The transcription cofactor YAP (Yes-associated protein) might be a key effector of renal regeneration and fibrogenesis. Our results showed further that YAP might elicit both beneficial and detrimental effects on I/R AKI. After I/R injury occurred, YAP could promote the repair of the injured epithelia. The constant YAP increase and activation might be related to interstitial fibrosis and abnormal renal tubule differentiation. These results indicate that the proper modulation of the Hippo pathway, specifically the transcription cofactor YAP, during repair might be a potent therapeutic target in AKI–CKD transition after I/R injury.

Heart valve disease is a major clinical problem worldwide. Cardiac valve development and homeostasis need to be precisely controlled. Hippo signaling is essential for organ development and tissue homeostasis, while its role in valve formation and morphology maintenance remains unknown. VGLL4 is a transcription cofactor in vertebrates and we found it was mainly expressed in valve interstitial cells at the post-EMT stage and was maintained till the adult stage. Tissue specific knockout of VGLL4 in different cell lineages revealed that only loss of VGLL4 in endothelial cell lineage led to valve malformation with expanded expression of YAP targets. We further semi-knockout YAP in VGLL4 ablated hearts, and found hyper proliferation of arterial valve interstitial cells was significantly constrained. These findings suggest that VGLL4 is important for valve development and manipulation of Hippo components would be a potential therapy for preventing the progression of congenital valve disease. VGLL4, a new member of the Hippo pathway, is intensively investigated in inhibition of tumor progression via competing with YAP to bind TEADs, but its role in cardiovascular field remains unclear. Here we generated VGLL4 knockout mouse line and VGLL4-eGFP reporter mouse line. VGLL4-eGFP reporter mouse line showed VGLL4 was mainly expressed in valve interstitial cells from post-EMT stage to adult stage. Genetic loss of function and lineage tracing data demonstrated only endothelial loss of VGLL4 led to valve malformation with up-regulation of YAP targets. Of note, semi-knockout YAP could rescue this phenotype of VGLL4 knockouts. This is the first study to show the Hippo pathway plays a critical role in valve remodeling, maturation and homeostasis. Our findings suggest that mutations in VGLL4 may underlie human congenital heart valve dysplasia.

Background: Interleukin 1 beta (IL-1β) plays an important role in a number of chronic and acute inflammatory diseases. To understand the role of IL-1β in disease processes and develop anin vivoscreening system for anti-inflammatory drugs, a transgenic mouse line was generated which incorporated the transgene firefly luciferase gene driven by a 4.5-kb fragment of the human IL-1β gene promoter. Luciferase gene expression was monitored in live mice under anesthesia using bioluminescence imaging in a number of inflammatory disease models.Results: In a LPS-induced sepsis model, dramatic increase in luciferase activity was observed in the mice. This transgene induction was time dependent and correlated with an increase of endogenous IL-1β mRNA and pro-IL-1β protein levels in the mice. In a zymosan-induced arthritis model and an oxazolone-induced skin hypersensitivity reaction model, luciferase expression was locally induced in the zymosan injected knee joint and in the ear with oxazolone application, respectively. Dexamethasone suppressed the expression of luciferase gene both in the acute sepsis model and in the acute arthritis model.Conclusion: Our data suggest that the transgenic mice model could be used to study transcriptional regulation of the IL-1β gene expression in the inflammatory process and evaluation the effect of anti-inflammatory drugin vivo.

We previously reported that partial disruption of the Ankrd26 gene in mice leads to hyperphagia and leptin-resistant obesity. To determine whether the Ankrd26 mutation can affect the development of adipocytes, we studied mouse embryo fibroblasts (MEFs) from the mutant mice. We found that Ankrd26(-/-) MEFs have a higher rate of spontaneous adipogenesis than normal MEFs and that adipocyte formation is greatly increased when the cells are induced with troglitazone alone or with a mixture of troglitazone, insulin, dexamethasone, and methylisobutylxanthine. Increased adipogenesis was detected as an increase in lipid droplet formation and in the expression of several markers of adipogenesis. There was an increase in expression of early stage adipogenesis genes such as Krox20, KLF5, C/EBPβ, C/EBPδ, and late stage adipogenesis regulators KLF15, C/EBPα, PPARγ, and aP2. There was also an increase in adipocyte stem cell markers CD34 and Sca-1 and preadipocyte markers Gata2 and Pref-1, indicating an increase in both stem cells and progenitor cells in the mutant MEFs. Furthermore, ERK was found constitutively activated in Anrd26(-/-) MEFs, and the addition of MEK inhibitors to mutant cells blocked ERK activation, decreased adipogenesis induction, and significantly reduced expression of C/EBPδ, KLF15, PPARγ2, CD34, and Pref-1 genes. We conclude that Ankrd26 gene disruption promotes adipocyte differentiation at both the progenitor commitment and differentiation steps and that ERK activation plays a role in this process.

The Hippo signaling pathway is known to play an important role in multiple physiological processes, including adipogenesis. However, whether the downstream components of the Hippo pathway are involved in adipogenesis remains unknown. Here we demonstrate that the TEA domain family (TEAD) transcription factors are essential for adipogenesis in murine 3T3-L1 preadipocytes. Knockdown of TEAD1–4 stimulated adipogenesis and increased the expression of adipocyte markers in these cells. Interestingly, we found that the TEAD4 knockdown–mediated adipogenesis proceeded in a Yes-associated protein (YAP)/TAZ (Wwtr1)–independent manner and that adipogenesis suppression in WT cells involved formation of a ternary complex comprising TEAD4 and the transcriptional cofactors C-terminal binding protein 2 (CtBP2) and vestigial-like family member 4 (VGLL4). VGLL4 acted as an adaptor protein that enhanced the interaction between TEAD4 and CtBP2, and this TEAD4–VGLL4–CtBP2 ternary complex dynamically existed at the early stage of adipogenesis. Finally, we verified that TEAD4 directly targets the promoters of major adipogenesis transcription factors such as peroxisome proliferator–activated receptor γ (PPARγ) and adiponectin, C1Q, and collagen domain–containing (Adipoq) during adipogenesis. These findings reveal critical insights into the role of the TEAD4–VGLL4–CtBP2 transcriptional repressor complex in suppression of adipogenesis in murine preadipocytes.

Partial inactivation of the Ankyrin repeat domain 26 (Ankrd26) gene causes obesity and diabetes in mice and increases spontaneous and induced adipogenesis in mouse embryonic fibroblasts. However, it is not yet known how the Ankrd26 protein carries out its biological functions. We identified by yeast two-hybrid and immunoprecipitation assays the triple functional domain protein (TRIO), the G protein pathway suppressor 2 (GPS2), the delta-interacting protein A (DIPA) and the hyaluronan-mediated motility receptor (HMMR) as ANKRD26 interacting partners. Adipogenesis of 3T3-L1 cells was increased by selective down-regulation of Ankrd26, Trio, Gps2, Hmmr and Dipa. Furthermore, GPS2 and DIPA, which are normally located in the nucleus, were translocated to the cytoplasm, when the C-terminus of ANKRD26 was introduced into these cells. These findings provide biochemical evidence that ANKRD26, TRIO, GPS2 and HMMR are novel and important regulators of adipogenisis and identify new targets for the modulation of adipogenesis.