Lethal Phenotype-Based Database Screening Identifies Ceramide as a Negative Regulator of Primitive Streak Formation

In early embryogenesis, the primitive streak (PrS) generates the mesendoderm and is essential for organogenesis. However, because the PrS is a minute and transient tissue, elucidating the mechanism of its formation has been challenging. We performed comprehensive screening of 2 knockout mouse databases based on the fact that failure of PrS formation is lethal. We identified 812 genes involved in various cellular functions and responses that might be linked to PrS formation, with the category of greatest abundance being "Metabolism." In this study, we focused on genes of sphingolipid metabolism and investigated their roles in PrS formation using an in vitro mouse ES cell differentiation system. We show here that elevated intracellular ceramide negatively regulates gene expression essential for PrS formation and instead induces neurogenesis. In addition, sphingosine-1-phosphate (a ceramide derivative) positively regulates neural maturation. Our results indicate that ceramide regulates both PrS formation and the induction of neural differentiation.

Stem cell challenges and opportunities

Hepatocyte-like cells (HLCs) generated from human pluripotent stem cells (PSCs) exhibit hepatocytic properties in vitro; however, their engraftment and functionality in vivo remain unsatisfactory. Despite optimization of differentiation protocols, HLCs did not engraft in a mouse model of liver injury. In contrast, organ-derived hepatocytes reproducibly formed colonies in the liver injury mouse model. As an extension of the phenomenon observed in hematopoietic stem cells giving rise to colonies within the spleen, commonly referred to as "colony-forming units in spleen (CFU-s)", we hypothesize that "colony-forming units in liver (CFU-L)" serves as a reliable indicator of stemness, engraftment, and functionality of hepatocytes. The uniform expression of the randomly inactivated gene in a single colony, as reported by Sugahara et al. 2022, suggests that the colonies generated by isolated hepatocytes likely originate from a single cell. We, therefore, propose that CFU-L can be used to quantify the number of "hepatocytes that engraft and proliferate in vivo" as a quantitative assay for stem cells that utilize colony-forming ability, similar to that observed in hematopoietic stem cells.

Development of small fluorescent probes for the analysis of autophagy kinetics

Autophagy is a dynamic process that degrades subcellular constituents, and its activity is measured by autophagic flux. The tandem proteins RFP-GFP-LC3 and GFP-LC3-RFP-LC3ΔG, which enable the visualization of autophagic vacuoles of different stages by differences in their fluorescent color, are useful tools to monitor autophagic flux, but they require plasmid transfection. In this study, we hence aimed to develop a new method to monitor autophagic flux using small cell-permeable fluorescent probes. We previously developed two green-fluorescent probes, DALGreen and DAPGreen, which detect autolysosomes and multistep autophagic vacuoles, respectively. We here developed a red-fluorescent autophagic probe, named DAPRed, which recognizes various autophagic vacuoles. By the combinatorial use of these green- and red-fluorescent probes, we were able to readily detect autophagic flux. Furthermore, these probes were useful not only for the visualization of canonical autophagy but also for alternative autophagy. DAPRed was also applicable for the detection of autophagy in living organisms.

Integrator complex subunit 15 controls mRNA splicing and is critical for eye development

The eye and brain are composed of elaborately organized tissues, development of which is supported by spatiotemporally precise expression of a number of transcription factors and developmental regulators. Here we report the molecular and genetic characterization of Integrator complex subunit 15 (INTS15). INTS15 was identified in search for the causative gene(s) for an autosomal-dominant eye disease with variable individual manifestation found in a large pedigree. While homozygous Ints15 knockout mice are embryonic lethal, mutant mice lacking a small C-terminal region of Ints15 show ocular malformations similar to the human patients. INTS15 is highly expressed in the eye and brain during embryogenesis and stably interacts with the Integrator complex to support snRNA 3' end processing. Its knockdown resulted in missplicing of a large number of genes, probably as a secondary consequence, and substantially affected genes associated with eye and brain development. Moreover, studies using human iPS-derived neural progenitor cells showed that INTS15 is critical for axonal outgrowth in retinal ganglion cells. This study suggests a new link between general transcription machinery and a highly specific hereditary disease.

HBx and YAP expression could promote tumor development and progression in HBV-related hepatocellular carcinoma

Background

Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) accounts for 10%–20% of the total HCC numbers. Its clinical features include the occurrence in the younger generation, large tumors, and poor prognosis. The contribution of hepatitis B virus X (HBx) protein in hepatocytes during activation of various oncogenic pathways has been reported. We aimed to assess the possible association between HBx and Yes-associated protein (YAP) expression in the liver tissue and the clinical features of HBV-related HCC.

Methods

The relationship between HBx and YAP expression was examined in vivo using HCC tumor and peritumor tissues (n = 55). The clinical information including tumor size, marker, and the prognosis was assessed with protein expressions. The in vitro gene expression analyses were conducted using HBx- and YAP-overexpressing HCC cell lines.

Results

Among 19 cases of HBV-related, 17 cases of hepatitis C virus (HCV)-related, and 19 cases of nonviral-related HCC, the HBV-related tumor showed the largest size. The HBx-stained area in the tumor and peritumor tissue showed a significant correlation with tumor size and serum α-fetoprotein level. YAP expression was higher in HBV-related tumor tissue than in the peritumor tissue and HCV-related tumor. Additionally, HBx and YAP protein expressions are correlated and both expressions in the tumor contributed to the poor prognosis. An in vitro study demonstrated that HBx and YAP overexpression in the hepatocytes activate the various oncogenic signaling pathways.

Conclusions

Our study demonstrated that YAP expression in the liver of HBV-infected patients might be the key factor in HBV-related HCC development and control of tumor-related features.

•

HBx and YAP expression are related to the HCC size and tumor marker level.

•

HBx activates YAP expression and both protein expressions are correlated.

•

Co-expression of HBx and YAP contributes to the poor prognosis of HCC cases.

•

HBx and YAP expression in vitro activated various oncogenic pathways.

Collagen type I-mediated mechanotransduction controls epithelial cell fate conversion during intestinal inflammation

BACKGROUND

The emerging concepts of fetal-like reprogramming following tissue injury have been well recognized as an important cue for resolving regenerative mechanisms of intestinal epithelium during inflammation. We previously revealed that the remodeling of mesenchyme with collagen fibril induces YAP/TAZ-dependent fate conversion of intestinal/colonic epithelial cells covering the wound bed towards fetal-like progenitors. To fully elucidate the mechanisms underlying the link between extracellular matrix (ECM) remodeling of mesenchyme and fetal-like reprogramming of epithelial cells, it is critical to understand how collagen type I influence the phenotype of epithelial cells. In this study, we utilize collagen sphere, which is the epithelial organoids cultured in purified collagen type I, to understand the mechanisms of the inflammatory associated reprogramming. Resolving the entire landscape of regulatory networks of the collagen sphere is useful to dissect the reprogrammed signature of the intestinal epithelium.

METHODS

We performed microarray, RNA-seq, and ATAC-seq analyses of the murine collagen sphere in comparison with Matrigel organoid and fetal enterosphere (FEnS). We subsequently cultured human colon epithelium in collagen type I and performed RNA-seq analysis. The enriched genes were validated by gene expression comparison between published gene sets and immunofluorescence in pathological specimens of ulcerative colitis (UC).

RESULTS

The murine collagen sphere was confirmed to have inflammatory and regenerative signatures from RNA-seq analysis. ATAC-seq analysis confirmed that the YAP/TAZ-TEAD axis plays a central role in the induction of the distinctive signature. Among them, TAZ has implied its relevant role in the process of reprogramming and the ATAC-based motif analysis demonstrated not only Tead proteins, but also Fra1 and Runx2, which are highly enriched in the collagen sphere. Additionally, the human collagen sphere also showed a highly significant enrichment of both inflammatory and fetal-like signatures. Immunofluorescence staining confirmed that the representative genes in the human collagen sphere were highly expressed in the inflammatory region of ulcerative colitis.

CONCLUSIONS

Collagen type I showed a significant influence in the acquisition of the reprogrammed inflammatory signature in both mice and humans. Dissection of the cell fate conversion and its mechanisms shown in this study can enhance our understanding of how the epithelial signature of inflammation is influenced by the ECM niche.

Protein kinase Cα activation switches YAP1 from TEAD-mediated signaling to p73-mediated signaling

Yes-associated protein 1 (YAP1) interacts with TEAD transcription factor in the nucleus and upregulates TEAD-target genes. YAP1 is phosphorylated by large tumor suppressor (LATS) kinases, the core kinases of the Hippo pathway, at 5 serine residues and is sequestered and degraded in the cytoplasm. In human cancers with the dysfunction of the Hippo pathway, YAP1 becomes hyperactive and confers malignant properties to cancer cells. We have observed that cold shock induces protein kinase C (PKC)-mediated phosphorylation of YAP1. PKC phosphorylates YAP1 at 3 serine residues among LATS-mediate phosphorylation sites. Importantly, PKC activation recruits YAP1 to the cytoplasm even in LATS-depleted cancer cells and reduces the cooperation with TEAD. PKC activation induces promyelocytic leukemia protein-mediated SUMOylation of YAP1. SUMOylated YAP1 remains in the nucleus, binds to p73, and promotes p73-target gene transcription. Bryostatin, a natural anti-neoplastic reagent that activates PKC, induces YAP1/p73-mediated apoptosis in cancer cells. Bryostatin reverses malignant transformation caused by the depletion of LATS kinases. Therefore, bryostatin and other reagents that activate PKC are expected to control cancers with the dysfunction of the Hippo pathway.

Physiological and pathological roles of the Hippo-YAP/TAZ signaling pathway in liver formation, homeostasis and tumorigenesis

The liver plays central homeostatic roles in metabolism and detoxification, and has a remarkable capacity to fully recover from injuries caused by the various insults to which it is constantly exposed. To fulfill these functions, the liver must maintain a specific size and so must regulate its cell numbers. It must also remove senescent, transformed, and/or injured cells that impair liver function and can lead to diseases such as cirrhosis and liver cancer. Despite their importance, however, the mechanisms governing liver size control and homeostasis have resisted delineation. The discovery of the Hippo intracellular signaling pathway and its downstream effectors, the transcriptional coactivators Yes‐associated protein (YAP) and transcriptional coactivator with PDZ‐binding motif (TAZ), has provided partial elucidation of these mechanisms. The Hippo‐YAP/TAZ pathway is considered to be a cell’s sensor of its immediate microenvironment and the cells that surround it, in that this pathway responds to changes in elements such as the ECM, cell–cell tension, and cell adhesion. Once triggered, Hippo signaling negatively regulates the binding of YAP/TAZ to transcription factors such as TEAD and Smad, controlling their ability to drive gene expression needed for cellular responses such as proliferation, survival, and stemness. Numerous KO mouse strains lacking YAP/TAZ, as well as transgenic mice showing YAP/TAZ hyperactivation, have been generated, and the effects of these mutations on liver development, size, regeneration, homeostasis, and tumorigenesis have been reported. In this review, I summarize the components and regulation of Hippo‐YAP/TAZ signaling, and discuss this pathway in the context of liver physiology and pathology.

Puromycin-based purification of cells with high expression of the cytochrome P450 CYP3A4 gene from a patient with drug-induced liver injury (DILI)

BACKGROUND

Many drugs have the potential to induce the expression of drug-metabolizing enzymes, particularly cytochrome P450 3A4 (CYP3A4), in hepatocytes. Hepatocytes can be accurately evaluated for drug-mediated CYP3A4 induction; this is the gold standard for in vitro hepatic toxicology testing. However, the variation from lot to lot is an issue that needs to be addressed. Only a limited number of immortalized hepatocyte cell lines have been reported. In this study, immortalized cells expressing CYP3A4 were generated from a patient with drug-induced liver injury (DILI).

METHODS

To generate DILI-derived cells with high expression of CYP3A4, a three-step approach was employed: (1) Differentiation of DILI-induced pluripotent stem cells (DILI-iPSCs); (2) Immortalization of the differentiated cells; (3) Selection of the cells by puromycin. It was hypothesized that cells with high cytochrome P450 gene expression would be able to survive exposure to cytotoxic antibiotics because of their increased drug-metabolizing activity. Puromycin, a cytotoxic antibiotic, was used in this study because of its rapid cytocidal effect at low concentrations.

RESULTS

The hepatocyte-like cells differentiated from DILI-iPSCs were purified by exposure to puromycin. The puromycin-selected cells (HepaSM or SI cells) constitutively expressed the CYP3A4 gene at extremely high levels and exhibited hepatocytic features over time. However, unlike primary hepatocytes, the established cells did not produce bile or accumulate glycogen.

CONCLUSIONS

iPSC-derived hepatocyte-like cells with intrinsic drug-metabolizing enzymes can be purified from non-hepatocytes and undifferentiated iPSCs using the cytocidal antibiotic puromycin. The puromycin-selected hepatocyte-like cells exhibited characteristics of hepatocytes after immortalization and may serve as another useful source for in vitro hepatotoxicity testing of low molecular weight drugs.

Characterization of mouse embryonic fibroblasts derived from Rassf6 knockout mice shows the implication of Rassf6 in the regulation of NF-κB signaling

RASSF6 is a member of the tumor suppressor Ras association domain family (RASSF) proteins. We have reported using human cancer cell lines that RASSF6 induces apoptosis and cell cycle arrest via p53 and plays tumor suppressive roles. In this study, we generated Rassf6 knockout mice by CRISPR/Cas technology. Contrary to our expectation, Rassf6 knockout mice were apparently healthy. However, Rassf6-null mouse embryonic fibroblasts (MEF) were resistant against ultraviolet (UV)-induced apoptosis/cell cycle arrest and senescence. UV-induced p53-target gene expression was compromised, and DNA repair was delayed in Rassf6-null MEF. More importantly, KRAS active mutant promoted the colony formation of Rassf6-null MEF but not the wild-type MEF. RNA sequencing analysis showed that NF-κB signaling was enhanced in Rassf6-null MEF. Consistently, 7,12-dimethylbenz(a)anthracene (DMBA) induced skin inflammation in Rassf6 knockout mice more remarkably than in the wild-type mice. Hence, Rassf6 deficiency not only compromises p53 function but also enhances NF-κB signaling to lead to oncogenesis.

YAP drives cell competition by activating choline metabolism

Cell competition is a phenomenon that eliminates unfit cells from cell society, a function vital for maintaining cellular and organismal homeostasis. We previously showed that Madin-Darby canine kidney (MDCK) epithelial cells expressing the active form of the transcriptional coactivator Yes-associated protein (YAP) are apically extruded when surrounded by normal MDCK cells. Although we demonstrated that the arachidonic acid (AA) cascade is involved in YAP-dependent apical extrusion, the metabolic events leading to this outcome remained unclear. Here, we present the results of metabolomic analysis that identified phosphatidylcholine (PC) biosynthesis as the most significant player in this process. Removal of the PC biosynthetic components choline and methionine from culture medium inhibited YAP-dependent apical extrusion. Inhibition of either choline uptake or metabolic cycles involving choline or methionine also decreased YAP-dependent apical extrusion. At the molecular level, active YAP induced expression of the genes encoding glycerophosphocholine phosphodiesterase 1 (GPCPD1) and lecithin-cholesterol acyltransferase (LCAT), which are involved in choline metabolism. Our results indicate that YAP-dependent cell competition depends on YAP-mediated activation of the choline metabolic cycle.

The Light-Inducible Genes Per2, Cry1a, and Cry2a Regulate Oxidative Status in Zebrafish

The circadian clock is a highly conserved 24 h biological oscillation mechanism and is affected by environmental stimuli such as light, food and temperature. Disruption of the circadian clock results in disorders of diverse biological processes, including the sleep-wake cycle and metabolism. Although we previously identified several components of the circadian clock in zebrafish, our understanding of the relationship between light-inducible clock genes and metabolism remains incomplete. To investigate how light-inducible clock genes regulate metabolism, we performed transcriptomic and metabolomic analyses of the light-inducible clock genes zPer2, zCry1a, and zCry2a in zebrafish. Transcriptomic analysis of zPer2/zCry1a double knockout (DKO) and zPer2/zCry1a/zCry2a triple knockout (TKO) mutants showed that their gene expression profiles differed from that of wild type (WT) zebrafish. In particular, mRNA levels of zKeap1a, which encodes an oxidative stress sensor, were increased in DKO and TKO mutants. Metabolomic analysis showed genotype-dependent alteration of metabolomic profiles. Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) showed the alteration of cysteine/methionine metabolism and glutathione metabolism. Specifically, cysteine and glutathione were decreased but methionine sulfoxide was increased in TKO zebrafish. These results indicate that the light-inducible genes zPer2, zCry1a, and zCry2a are involved in regulating the oxidative status of zebrafish.

Alantolactone is a natural product that potently inhibits YAP1/TAZ through promotion of reactive oxygen species accumulation

Yes‐associated protein 1 (YAP1) and its paralogue PDZ‐binding motif (TAZ) play pivotal roles in cell proliferation, migration, and invasion, and abnormal activation of these TEAD transcriptional coactivators is found in diverse cancers in humans and mice. Targeting YAP1/TAZ signaling is thus a promising therapeutic avenue but, to date, few selective YAP1/TAZ inhibitors have been effective against cancer cells either in vitro or in vivo. We screened chemical libraries for potent YAP1/TAZ inhibitors using a highly sensitive luciferase reporter system to monitor YAP1/TAZ‐TEAD transcriptional activity in cells. Among 29 049 low‐molecular‐weight compounds screened, we obtained nine hits, and the four of these that were the most effective shared a core structure with the natural product alantolactone (ALT). We also tested 16 other structural derivatives of ALT and found that natural ALT was the most efficient at increasing ROS‐induced LATS kinase activities and thus YAP1/TAZ phosphorylation. Phosphorylated YAP1/TAZ proteins were subject to nuclear exclusion and proteosomic degradation such that the growth of ALT‐treated tumor cells was inhibited both in vitro and in vivo. Our data show for the first time that ALT can be used to target the ROS‐YAP pathway driving tumor cell growth and so could be a potent anticancer drug.

Hepatocyte Mitogen-Activated Protein Kinase Kinase 7 Contributes to Restoration of the Liver Parenchyma Following Injury in Mice

BACKGROUND AND AIMS

Mitogen-activated protein kinase kinase (MKK) 7 and MKK4 are upstream activators of c-Jun NH₂ -terminal kinases (JNKs) and have been shown to be required for the early development of the liver. Although it has been suggested that MKK7 might be involved in the regulation of hepatocyte proliferation, the functional role of MKK7 in the liver has remained unclear.

APPROACH AND RESULTS

Here, we examined phenotypic alterations in liver-specific or hepatocyte/hematopoietic cell-specific MKK7 knockout (KO) mice, which were generated by crossing MKK7^LoxP/LoxP with albumin-cyclization recombination (Alb-Cre) or myxovirus resistance protein 1-Cre mice, respectively. The livers of Alb-Cre^-/+ MKK7^LoxP/LoxP mice developed without discernible tissue disorganization. MKK7 KO mice responded normally to liver injuries incurred by partial hepatectomy or injection of CCl₄ . However, tissue repair following CCl₄ -induced injury was delayed in MKK7 KO mice compared with that of control mice. Furthermore, after repeated injections of CCl₄ for 8 weeks, the liver in MKK7 KO mice showed intense fibrosis with increased protractive hepatocyte proliferation, suggesting that MKK7 deficiency might affect regenerative responses of hepatocytes in the altered tissue microenvironment. MKK7 KO hepatocytes demonstrated normal proliferative activity when cultured in monolayers. However, MKK7 KO significantly suppressed branching morphogenesis of hepatocyte aggregates within a collagen gel matrix. Microarray analyses revealed that suppression of branching morphogenesis in MKK7 KO hepatocytes was associated with a reduction in mRNA expression of transgelin, glioma pathogenesis related 2, and plasminogen activator urokinase-type (Plau); and forced expression of these genes in MKK7 KO hepatocytes partially recovered the attenuated morphogenesis. Furthermore, hepatocyte-specific overexpression of Plau rescued the impaired tissue repair of MKK7 KO mice following CCl₄ -induced injury.

CONCLUSIONS

MKK7 is dispensable for the regenerative proliferation of hepatocytes but plays important roles in repair processes following parenchymal destruction, possibly through modulation of hepatocyte-extracellular matrix interactions.

Clinical outcomes of patients with diffuse coronary artery disease following physiology-guided treatment strategy: insights from AJIP registry

Background

Physiology-guided treatment strategy improves clinical outcomes of patients with coronary artery disease. However, it has not been fully evaluated whether such guideline-based strategy is useful for patients with diffuse coronary artery disease as well, which is known to be one of the major factors affecting morbidity and mortality.

Purpose

The aim of this study was to clarify clinical outcomes of patients with diffuse coronary artery disease whose treatment strategy was based on coronary physiology.

Methods

From an international multicentre registry of iFR-pullback, consecutive 1067 patients (1185 vessels) with stable angina were included in whom coronary lesions were deferred or revascularized according to the iFR cutoff: 0.89. The physiological pattern of disease was classified according to the iFR-pullback recording as predominantly physiologically diffuse (n=463) or predominantly physiologically focal (n=722). Major adverse cardiovascular events (MACEs), defined as a composite of cardiac death, non-fatal myocardial infarction, and ischemia-driven target lesion revascularization during follow-up period, were compared between diffuse and focal groups, in both deferred and revascularized groups, respectively.

Results

Mean age was 67.1±10.7 years and 75.8% of patients were men. Median iFR was 0.88 (interquartile range: 0.80 to 0.92). At a median follow-up period of 18 months, no significant differences in MACEs were found between diffuse and focal groups, in both iFR-based deferred and revascularized groups. In the deferred group (n=480), MACEs occurred in 6.9% patients (15/217) in the diffuse group and 8.0% patients (21/263) in the focal group (p=0.44). In the revascularized group (n=705), MACEs occurred in 8.9% patients (22/246) in the diffuse group and 7.2% patients (33/459) in the focal group (p=0.49).

Conclusions

Despite potentially higher risks in patients with diffuse coronary artery disease, clinical outcomes of those patients were comparable to those of patients without diffuse disease, as long as treatment strategy was based on the physiology guidance, which is globally recommended by international guidelines.

Funding Acknowledgement

Type of funding source: None

MKK7 deficiency in mature neurons impairs parental behavior in mice

c‐Jun N‐terminal kinases (JNKs) are constitutively activated in mammalian brains and are indispensable for their development and neural functions. MKK7 is an upstream activator of all JNKs. However, whether the common JNK signaling pathway regulates the brain's control of social behavior remains unclear. Here, we show that female mice in which Mkk7 is deleted specifically in mature neurons (Mkk7^flox/floxSyn‐Cre mice) give birth to a normal number of pups but fail to raise them due to a defect in pup retrieval. To explore the mechanism underlying this abnormality, we performed comprehensive behavioral tests. Mkk7^flox/floxSyn‐Cre mice showed normal locomotor functions and cognitive ability but exhibited depression‐like behavior. cDNA microarray analysis of mutant brain revealed an altered gene expression pattern. Quantitative RT‐PCR analysis demonstrated that mRNA expression levels of genes related to neural signaling pathways and a calcium channel were significantly different from controls. In addition, loss of neural MKK7 had unexpected regulatory effects on gene expression patterns in oligodendrocytes. These findings indicate that MKK7 has an important role in regulating the gene expression patterns responsible for promoting normal social behavior and staving off depression.

Endogenous YAP1 activation drives immediate onset of cervical carcinoma in situ in mice

Cervical cancer (CC) is usually initiated by infection with high‐risk types of human papillomavirus (HPV). The HPV E6 and E7 proteins target p53 and RB, respectively, but other cellular targets likely exist. We generated uterus‐specific MOB1A/B double KO (uMob1DKO) mice, which immediately developed cervical squamous cell carcinoma in situ. Mutant cervical epithelial cells showed YAP1‐dependent hyperproliferation, altered self‐renewal, impaired contact inhibition, and chromosomal instability. p53 activation was increased in uMob1DKO cells, and additional p53 loss in uMob1DKO mice accelerated tumor invasion. In human CC, strong YAP1 activation was observed from the precancerous stage. Human cells overexpressing HPV16 E6/E7 showed inactivation of not only p53 and RB but also PTPN14, boosting YAP1 activation. Estrogen, cigarette smoke condensate, and PI3K hyperactivation all increased YAP1 activity in human cervical epithelial cells, and PTPN14 depletion along with PI3K activation or estrogen treatment further enhanced YAP1. Thus, immediate CC onset may initiate when YAP1 activity exceeds an oncogenic threshold, making Hippo‐YAP1 signaling a major CC driver.

The RAS-interacting chaperone UNC119 drives the RASSF6-MDM2-p53 axis and antagonizes RAS-mediated malignant transformation

The gene encoding the proto-oncogene GTPase RAS is frequently mutated in human cancers. Mutated RAS proteins trigger antiapoptotic and cell-proliferative signals and lead to oncogenesis. However, RAS also induces apoptosis and senescence, which may contribute to the eradication of cells with RAS mutations. We previously reported that Ras association domain family member 6 (RASSF6) binds MDM2 and stabilizes the tumor suppressor p53 and that the active form of KRAS promotes the interaction between RASSF6 and MDM2. We also reported that Unc-119 lipid-binding chaperone (UNC119A), a chaperone of myristoylated proteins, interacts with RASSF6 and regulates RASSF6-mediated apoptosis. In this study, using several human cancer cell lines, quantitative RT-PCR, RNAi-based gene silencing, and immunoprecipitation/-fluorescence and cell biology assays, we report that UNC119A interacts with the active form of KRAS and that the C-terminal modification of KRAS is required for this interaction. We also noted that the hydrophobic pocket of UNC119A, which binds the myristoylated peptides, is not involved in the interaction. We observed that UNC119A promotes the binding of KRAS to RASSF6, enhances the interaction between RASSF6 and MDM2, and induces apoptosis. Conversely, UNC119A silencing promoted soft-agar colony formation, migration, and invasiveness in KRAS-mutated cancer cells. We conclude that UNC119A promotes KRAS-mediated p53-dependent apoptosis via RASSF6 and may play a tumor-suppressive role in cells with KRAS mutations.

YAP1 is a potent driver of the onset and progression of oral squamous cell carcinoma

Head-and-neck squamous cell carcinoma (HNSCC) is the sixth most common group of cancers in the world, and patients have a poor prognosis. Here, we present data indicating that YAP1 may be a strong driver of the onset and progression of oral SCC (OSCC), a major subtype of HNSCC. Mice with tongue-specific deletion of Mob1a/b and thus endogenous YAP1 hyperactivation underwent surprisingly rapid and highly reproducible tumorigenesis, developing tongue carcinoma in situ within 2 weeks and invasive SCC within 4 weeks. In humans, precancerous tongue dysplasia displays YAP1 activation correlating with reduced patient survival. Combinations of molecules mutated in OSCC may increase and sustain YAP1 activation to the point of oncogenicity. Strikingly, siRNA or pharmacological inhibition of YAP1 blocks murine OSCC onset in vitro and in vivo. Our work justifies targeting YAP1 as therapy for OSCC and perhaps HNSCC, and our mouse model represents a powerful tool for evaluating these agents.

Prostaglandin E2 and its receptor EP2 trigger signaling that contributes to YAP-mediated cell competition

Cell competition is a biological process by which unfit cells are eliminated from “cell society.” We previously showed that cultured mammalian epithelial Madin‐Darby canine kidney (MDCK) cells expressing constitutively active YAP were eliminated by apical extrusion when surrounded by “normal” MDCK cells. However, the molecular mechanism underlying the elimination of active YAP‐expressing cells was unknown. Here, we used high‐throughput chemical compound screening to identify cyclooxygenase‐2 (COX‐2) as a key molecule triggering cell competition. Our work shows that COX‐2‐mediated PGE₂ secretion engages its receptor EP2 on abnormal and nearby normal cells. This engagement of EP2 triggers downstream signaling via an adenylyl cyclase‐cyclic AMP‐PKA pathway that, in the presence of active YAP, induces E‐cadherin internalization leading to apical extrusion. Thus, COX‐2‐induced PGE₂ appears a warning signal to both abnormal and surrounding normal cells to drive cell competition.

Inhibition of sodium-glucose cotransporter 2 ameliorates renal injury in a novel medaka model of nonalcoholic steatohepatitis-related kidney disease

The effect of sodium‐glucose cotransporter 2 inhibitor (SGLT2I) on nonalcoholic steatohepatitis (NASH) has been reported, but there are few studies on its effect on NASH‐related renal injury. In this study, we examined the effect of SGLT2I using a novel medaka fish model of NASH‐related kidney disease, which was developed by feeding the d‐rR/Tokyo strain a high‐fat diet. SGLT2I was administered by dissolving it in water of the feeding tank. SGLT2I ameliorates macrophage accumulation and oxidative stress and maintained mitochondrial function in the kidney. The results demonstrate the effect of SGLT2I on NASH‐related renal injury and the usefulness of this novel animal model for research into NASH‐related complications.

Here, we demonstrate that the highly specific sodium‐glucose cotransporter 2 inhibitor (SGLT2I) prevented the progression of nonalcoholic steatohepatitis (NASH)‐related renal injury in a medaka fish model of NASH‐related kidney disease. SGLT2I ameliorates oxidative stress and macrophage accumulation and maintained mitochondrial function in renal tubules.

Inhibition of sodium glucose cotransporter 2 (SGLT2) delays liver fibrosis in a medaka model of nonalcoholic steatohepatitis (NASH)

The rise in the incidence of nonalcoholic steatohepatitis (NASH) has necessitated the development of an effective prevention methodology. An antidiabetic drug, belonging to the group of sodium glucose cotransporter 2 (SGLT2) inhibitors, has been tested for its therapeutic effect on NASH; however, no studies to date have demonstrated the preventive effect of an SGLT2 inhibitor on the histological progression of steatosis and fibrosis in a sequential manner in animal models. In the present study, we examined the effect of the SGLT2 inhibitor, tofogliflozin (Tofo), on NASH liver tissue using medaka as an animal model, maintaining a feeding amount and drug concentration in all animal bodies. We generated a medaka NASH model by feeding d‐rR/Tokyo medaka a high‐fat diet and administered Tofo by dissolving the drug directly in the water of the feeding tank. Thereafter, the effects of Tofo on body weight (BW), liver weight, hepatotoxicity, fatty infiltration, and fibrotic changes in the liver were examined. We report here that SGLT2 is expressed in medaka fish and that Tofo inhibits the accumulation of fatty tissue and delays the progression of liver fibrosis in the medaka NASH model by inhibiting increases in blood sugar, serum lipids, and transaminase, irrespective of changes in BW. These results suggest that Tofo is effective for treating NASH and that the medaka model may be useful for developing new therapeutic drugs for this disease.

The clock components Period2, Cryptochrome1a, and Cryptochrome2a function in establishing light-dependent behavioral rhythms and/or total activity levels in zebrafish

The circadian clock generates behavioral rhythms to maximize an organism’s physiological efficiency. Light induces the formation of these rhythms by synchronizing cellular clocks. In zebrafish, the circadian clock components Period2 (zPER2) and Cryptochrome1a (zCRY1a) are light-inducible, however their physiological functions are unclear. Here, we investigated the roles of zPER2 and zCRY1a in regulating locomotor activity and behavioral rhythms. zPer2/zCry1a double knockout (DKO) zebrafish displayed defects in total locomotor activity and in forming behavioral rhythms when briefly exposed to light for 3-h. Exposing DKO zebrafish to 12-h light improved behavioral rhythm formation, but not total activity. Our data suggest that the light-inducible circadian clock regulator zCRY2a supports rhythmicity in DKO animals exposed to 12-h light. Single cell imaging analysis revealed that zPER2, zCRY1a, and zCRY2a function in synchronizing cellular clocks. Furthermore, microarray analysis of DKO zebrafish showed aberrant expression of genes involved regulating cellular metabolism, including ATP production. Overall, our results suggest that zPER2, zCRY1a and zCRY2a help to synchronize cellular clocks in a light-dependent manner, thus contributing to behavioral rhythm formation in zebrafish. Further, zPER2 and zCRY1a regulate total physical activity, likely via regulating cellular energy metabolism. Therefore, these circadian clock components regulate the rhythmicity and amount of locomotor behavior.

Growth Cone Phosphoproteomics Reveals that GAP-43 Phosphorylated by JNK Is a Marker of Axon Growth and Regeneration

Neuronal growth cones are essential for nerve growth and regeneration, as well as for the formation and rearrangement of the neural network. To elucidate phosphorylation-dependent signaling pathways and establish useful molecular markers for axon growth and regeneration, we performed a phosphoproteomics study of mammalian growth cones, which identified >30,000 phosphopeptides of ∼1,200 proteins. The phosphorylation sites were highly proline directed and primarily MAPK dependent, owing to the activation of JNK, suggesting that proteins that undergo proline-directed phosphorylation mediate nerve growth in the mammalian brain. Bioinformatics analysis revealed that phosphoproteins were enriched in microtubules and the cortical cytoskeleton. The most frequently phosphorylated site was S96 of GAP-43 (growth-associated protein 43-kDa), a vertebrate-specific protein involved in axon growth. This previously uncharacterized phosphorylation site was JNK dependent. S96 phosphorylation was specifically detected in growing and regenerating axons as the most frequent target of JNK signaling; thus it represents a promising new molecular marker for mammalian axonal growth and regeneration.

•

Phosphoproteomics of mammalian growth cone membranes reveals activation of MAPK

•

JNK is the activated MAPK in growth cones and phosphorylates S96 of GAP-43

•

pS96 of GAP-43, the most frequent site, is observed in growing axons

•

pS96 is biochemically detected in the regenerating axons of the peripheral nerves

The Hippo-YAP Pathway Regulates 3D Organ Formation and Homeostasis

The vertebrate body shape is formed by the specific sizes and shapes of its resident tissues and organs, whose alignments are essential for proper functioning. To maintain tissue and organ shape, and thereby function, it is necessary to remove senescent, transformed, and/or damaged cells, which impair function and can lead to tumorigenesis. However, the molecular mechanisms underlying three-dimensional (3D) organ formation and homeostasis are not fully clear. Yes-associated protein (YAP) is a transcriptional co-activator that is involved in organ size control and tumorigenesis. Recently, we reported that YAP is essential for proper 3D body shape through regulation of cell tension by using a unique medaka fish mutant, hirame (hir). In Madin–Darby canine kidney (MDCK) epithelial cells, active YAP-transformed cells are eliminated apically when surrounded by normal cells. Furthermore, in a mosaic mouse model, active YAP-expressing damaged hepatocytes undergo apoptosis and are eliminated from the liver. Thus, YAP functions in quantitative and quality control in organogenesis. In this review, we describe the various roles of YAP in vertebrates, including in the initiation of liver cancer.

Loss of Mob1a/b in mice results in chondrodysplasia due to YAP1/TAZ-TEAD-dependent repression of SOX9

Hippo signaling is modulated in response to cell density, external mechanical forces, and rigidity of the extracellular matrix (ECM). The Mps one binder kinase activator (MOB) adaptor proteins are core components of Hippo signaling and influence Yes-associated protein 1 (YAP1) and transcriptional co-activator with PDZ-binding motif (TAZ), which are potent transcriptional regulators. YAP1/TAZ are key contributors to cartilage and bone development but the molecular mechanisms by which the Hippo pathway controls chondrogenesis are largely unknown. Cartilage is rich in ECM and also subject to strong external forces - two upstream factors regulating Hippo signaling. Chondrogenesis and endochondral ossification are tightly controlled by growth factors, morphogens, hormones, and transcriptional factors that engage in crosstalk with Hippo-YAP1/TAZ signaling. Here, we generated tamoxifen-inducible, chondrocyte-specific Mob1a/b-deficient mice and show that hyperactivation of endogenous YAP1/TAZ impairs chondrocyte proliferation and differentiation/maturation, leading to chondrodysplasia. These defects were linked to suppression of SOX9, a master regulator of chondrogenesis, the expression of which is mediated by TEAD transcription factors. Our data indicate that a MOB1-dependent YAP1/TAZ-TEAD complex functions as a transcriptional repressor of SOX9 and thereby negatively regulates chondrogenesis.

Effect of a neural relay on liver regeneration in mice: activation of serotonin release from the gastrointestinal tract

The development of therapeutic options to promote hepatic regeneration following severe liver injury is essential. While humoral factors have been reported as mechanisms of liver regeneration, the contributions of interorgan communication to liver regeneration have not been reported. In this study, we examined the effect of a neural relay on liver regeneration via activation of serotonin release from the gastrointestinal (GI) tract. Our results demonstrated that the afferent visceral nerve from the liver activates the efferent vagus nerve from the brain, leading to activation of serotonin release from the GI tract and contributing to liver regeneration. While it is difficult to apply these results directly to human health, we believe that this study may represent a step toward developing essential therapeutics to promote liver regeneration.

Endosomal phosphatidylserine is critical for the YAP signalling pathway in proliferating cells

Yes-associated protein (YAP) is a recently discovered growth-promoting transcription coactivator that has been shown to regulate the malignancy of various cancers. How YAP is regulated is not fully understood. Here, we show that one of the factors regulating YAP is phosphatidylserine (PS) in recycling endosomes (REs). We use proximity biotinylation to find proteins proximal to PS. Among these proteins are YAP and multiple proteins related to YAP signalling. Knockdown of ATP8A1 (an RE PS-flippase) or evectin-2 (an RE-resident protein) and masking of PS in the cytoplasmic leaflet of membranes, all suppress nuclear localization of YAP and YAP-dependent transcription. ATP8A1 knockdown increases the phosphorylated (activated) form of Lats1 that phosphorylates and inactivates YAP, whereas evectin-2 knockdown reduces the ubiquitination and increased the level of Lats1. The proliferation of YAP-dependent metastatic cancer cells is suppressed by knockdown of ATP8A1 or evectin-2. These results suggest a link between a membrane phospholipid and cell proliferation.

Age-dependent motor dysfunction due to neuron-specific disruption of stress-activated protein kinase MKK7

c-Jun N-terminal kinase (JNK) is a member of the mitogen-activated protein kinase family and controls various physiological processes including apoptosis. A specific upstream activator of JNKs is the mitogen-activated protein kinase kinase 7 (MKK7). It has been reported that MKK7-JNK signaling plays an important regulatory role in neural development, however, post-developmental functions in the nervous system have not been elucidated. In this study, we generated neuron-specific Mkk7 knockout mice (MKK7 cKO), which impaired constitutive activation of JNK in the nervous system. MKK7 cKO mice displayed impaired circadian behavioral rhythms and decreased locomotor activity. MKK7 cKO mice at 8 months showed motor dysfunctions such as weakness of hind-limb and gait abnormality in an age-dependent manner. Axonal degeneration in the spinal cord and muscle atrophy were also observed, along with accumulation of the axonal transport proteins JNK-interacting protein 1 and amyloid beta precursor protein in the brains and spinal cords of MKK7 cKO mice. Thus, the MKK7-JNK signaling pathway plays important roles in regulating circadian rhythms and neuronal maintenance in the adult nervous system.

MOB1-YAP1/TAZ-NKX2.1 axis controls bronchioalveolar cell differentiation, adhesion and tumour formation

Mps One Binder Kinase Activator (MOB)1A/1B are core components of the Hippo pathway. These proteins, which coactivate LArge Tumour Suppressor homologue kinases, are also tumour suppressors. To investigate MOB1A/B's roles in normal physiology and lung cancer, we generated doxycycline (Dox)-inducible, bronchioalveolar epithelium-specific, null mutations of MOB1A/B in mice (SPC-rtTA/(tetO)₇-Cre/Mob1a^flox/flox/Mob1b^-/-; termed luMob1DKO mice). Most mutants (70%) receiving Dox in utero (luMob1DKO (E6.5-18.5) mice) died of hypoxia within 1 h post-birth. Their alveolar epithelial cells showed increased proliferation, impaired YAP1/TAZ-dependent differentiation and decreased surfactant protein production, all features characteristic of human respiratory distress syndrome. Intriguingly, mutant mice that received Dox postnatally (luMob1DKO (P21-41) mice) did not develop spontaneous lung adenocarcinomas, and urethane treatment-induced lung tumour formation was decreased (rather than increased). Lungs of luMob1DKO (P21-41) mice exhibited increased detachment of bronchiolar epithelial cells and decreased numbers of the bronchioalveolar stem cells thought to initiate lung adenocarcinomas. YAP1/TAZ-NKX2.1-dependent expression of collagen XVII, a key hemidesmosome component, was also reduced. Thus, a MOB1-YAP1/TAZ-NKX2.1 axis is essential for normal lung homeostasis and expression of the collagen XVII protein necessary for alveolar stem cell maintenance in the lung niche.

Manganese and cobalt activate zebrafish ovarian cancer G-protein-coupled receptor 1 but not GPR4

Mammalian ovarian G-protein-coupled receptor 1 (OGR1) is activated by some metals in addition to extracellular protons and coupling to multiple intracellular signaling pathways. In the present study, we examined whether zebrafish OGR1, zebrafish GPR4, and human GPR4 (zOGR1, zGPR4, and hGPR4, respectively) could sense the metals and activate the intracellular signaling pathways. On one hand, we found that only manganese and cobalt of the tested metals stimulated SRE-promoter activities in zOGR1-overexpressed HEK293T cells. On the other hand, none of the metals tested stimulated the promoter activities in zGPR4- and hGPR4-overexpressed cells. The OGR1 mutant (H4F), which is lost to activation by extracellular protons, did not stimulate metal-induced SRE-promoter activities. These results suggest that zOGR1, but not GPR4, is also a metal-sensing G-protein-coupled receptor in addition to a proton-sensing G-protein-coupled receptor, although not all metals that activate hOGR1 activated zOGR1.

YAP is essential for 3D organogenesis withstanding gravity

Cells of our body are constantly exposed to physical forces such as tissue tension. In recent years, it has been shown that such mechanical signals greatly influence a number of cellular processes, including proliferation, differentiation, and migration. Conversely, cells maintain the mechanical properties of tissues by remodeling their own extracellular environment. To date, however, it is unclear about the molecular mechanisms to maintain the mechanical environment ("mechano-homeostasis") in which extracellular mechanical cues are integrated with cell proliferation and differentiation to ensure tissue, organ and body form. In this review, we outline the molecular basis of mechanotransduction, and overview some useful techniques for measuring cellular tension. In the latter part, we describe our recent finding that a transcriptional cofactor YAP plays a crucial role in three-dimensional organ formation and its maintenance by controlling tissue tension, and functions as a key molecule governing mechano-homeostasis.

The mevalonate pathway regulates primitive streak formation via protein farnesylation

The primitive streak in peri-implantation embryos forms the mesoderm and endoderm and controls cell differentiation. The metabolic cues regulating primitive streak formation remain largely unknown. Here we utilised a mouse embryonic stem (ES) cell differentiation system and a library of well-characterised drugs to identify these metabolic factors. We found that statins, which inhibit the mevalonate metabolic pathway, suppressed primitive streak formation in vitro and in vivo. Using metabolomics and pharmacologic approaches we identified the downstream signalling pathway of mevalonate and revealed that primitive streak formation requires protein farnesylation but not cholesterol synthesis. A tagging-via-substrate approach revealed that nuclear lamin B1 and small G proteins were farnesylated in embryoid bodies and important for primitive streak gene expression. In conclusion, protein farnesylation driven by the mevalonate pathway is a metabolic cue essential for primitive streak formation.

MDCK cells expressing constitutively active Yes-associated protein (YAP) undergo apical extrusion depending on neighboring cell status

Cell competition is a cell-cell interaction by which a cell compares its fitness to that of neighboring cells. The cell with the relatively lower fitness level is the "loser" and actively eliminated, while the cell with the relatively higher fitness level is the "winner" and survives. Recent studies have shown that cells with high Yes-associated protein (YAP) activity win cell competitions but the mechanism is unknown. Here, we report the unexpected finding that cells overexpressing constitutively active YAP undergo apical extrusion and are losers, rather than winners, in competitions with normal mammalian epithelial cells. Inhibitors of metabolism-related proteins such as phosphoinositide-3-kinase (PI3K), mammalian target of rapamycin (mTOR), or p70S6 kinase (p70S6K) suppressed this apical extrusion, as did knockdown of vimentin or filamin in neighboring cells. Interestingly, YAP-overexpressing cells switched from losers to winners when co-cultured with cells expressing K-Ras (G12V) or v-Src. Thus, the role of YAP in deciding cell competitions depends on metabolic factors and the status of neighboring cells.

Validation of chemical compound library screening for transcriptional co-activator with PDZ-binding motif inhibitors using GFP-fused transcriptional co-activator with PDZ-binding motif

Transcriptional co-activator with PDZ-binding motif (TAZ) plays versatile roles in cell proliferation and differentiation. It is phosphorylated by large tumor suppressor kinases, the core kinases of the tumor-suppressive Hippo pathway. Phosphorylation induces the cytoplasmic accumulation of TAZ and its degradation. In human cancers, the deregulation of the Hippo pathway and gene amplification enhance TAZ activity. TAZ interacts with TEA domain family members (TEAD), and upregulates genes implicated in epithelial-mesenchymal transition. It also confers stemness to cancer cells. Thus, TAZ activation provides cancer cells with malignant properties and worsens the clinical prognosis. Therefore, TAZ attracts attention as a therapeutic target in cancer therapy. We applied 18 606 small chemical compounds to human osteosarcoma U2OS cells expressing GFP-fused TAZ (GFP-TAZ), monitored the subcellular localization of GFP-TAZ, and selected 33 compounds that shifted GFP-TAZ to the cytoplasm. Unexpectedly, only a limited number of compounds suppressed TAZ-mediated enhancement of TEAD-responsive reporter activity. Moreover, the compounds that weakened TEAD reporter activity did not necessarily decrease the unphosphorylated TAZ. In this study, we focused on three compounds that decreased both TEAD reporter activity and unphosphorylated TAZ, and treated several human cancer cells with these compounds. One compound did not show a remarkable effect, whereas the other two compounds compromised the cell viability in certain cancer cells. In conclusion, the GFP-TAZ-based assay can be used as the first screening for compounds that inhibit TAZ and show anticancer properties. To develop anticancer drugs, we need additional assays to select the compounds.

Modulation of anti-cancer drug sensitivity through the regulation of mitochondrial activity by adenylate kinase 4

BACKGROUND

Adenylate kinase is a key enzyme in the high-energy phosphoryl transfer reaction in living cells. An isoform of this enzyme, adenylate kinase 4 (AK4), is localized in the mitochondrial matrix and is believed to be involved in stress, drug resistance, malignant transformation in cancer, and ATP regulation. However, the molecular basis for the AK4 functions remained to be determined.

METHODS

HeLa cells were transiently transfected with an AK4 small interfering RNA (siRNA), an AK4 short hairpin RNA (shRNA) plasmid, a control shRNA plasmid, an AK4 expression vector, and a control expression vector to examine the effect of the AK4 expression on cell proliferation, sensitivity to anti-cancer drug, metabolome, gene expression, and mitochondrial activity.

RESULTS

AK4 knockdown cells treated with short hairpin RNA increased ATP production and showed greater sensitivity to hypoxia and anti-cancer drug, cis-diamminedichloro-platinum (II) (CDDP). Subcutaneous grafting AK4 knockdown cells into nude mice revealed that the grafted cells exhibited both slower proliferation and reduced the tumor sizes in response to CDDP. AK4 knockdown cell showed a increased oxygen consumption rate with FCCP treatment, while AK4 overexpression lowered it. Metabolome analysis showed the increased levels of the tricarboxylic acid cycle intermediates, fumarate and malate in AK4 knockdown cells, while AK4 overexpression lowered them. Electron microscopy detected the increased mitochondrial numbers in AK4 knockdown cells. Microarray analysis detected the increased gene expression of two key enzymes in TCA cycle, succinate dehydrogenase A (SDHA) and oxoglutarate dehydrogenease L (OGDHL), which are components of SDH complex and OGDH complex, supporting the metabolomic results.

CONCLUSIONS

We found that AK4 was involved in hypoxia tolerance, resistance to anti-tumor drug, and the regulation of mitochondrial activity. These findings provide a new potential target for efficient anticancer therapies by controlling AK4 expression.

[Role of Hippo-YAP/TAZ signaling pathway in mechanotransduction.]

Transcriptional coactivators YAP(yes associated protein)and TAZ(transcriptional coactivator with PDZ-binding motif)regulate gene expression through binding to transcription factors. Recently, some studies showed that YAP/TAZ activity responded to mechanical inputs such as stiffness of the extracellular matrix and the mechanical regulation of YAP/TAZ controlled cell proliferation or differentiation. Additionally, we revealed important roles of YAP in tissue formation and homeostasis through cellular tension and pressure. These reports indicate that YAP/TAZ are major factors in mechanotransduction connecting between the mechanical environment and cell responses.

Genetically Encoded Fluorescent Probe for Imaging Apoptosis in Vivo with Spontaneous GFP Complementation

Apoptosis plays a pivotal role in development and tissue homeostasis in multicellular organisms. Dysfunction of apoptosis is involved in many fatal diseases such as cancer. Visualization of apoptosis in living animals is necessary to understand the mechanism of apoptosis-related diseases. Here, we describe a genetically encoded fluorescent probe for imaging apoptosis in living multicellular organisms, based on spontaneous complementation of two fragments of a green fluorescent protein (GFP) variant (GFP OPT). The probe is designed for detection of mitochondria-mediated apoptosis during which a mitochondrial protein of Smac is released into cytosol. The Smac is connected with a carboxy-terminal fragment of GFP OPT (GFP11), whereas the remainder of GFP OPT (GFP(1-10)) is located in the cytosol. Under an apoptotic condition, the Smac is released from mitochondria into cytosol, allowing complementation of the GFP-OPT fragments and the emission of fluorescence. Live-cell imaging demonstrates that the probe enables detection of apoptosis in living cells with a high signal-to-background ratio. We applied the probe to living zebrafish, in which apoptotic cells were visualized with fluorescence. The technique provides a useful tool for the study of apoptosis in living animals, facilitating elucidation of the mechanisms of apoptosis-related diseases.

Evidence for a Role of the Transcriptional Regulator Maid in Tumorigenesis and Aging

Maid is a helix-loop-helix protein that is involved in cell proliferation. In order to further elucidate its physiological functions, we studied Maid activity in two small fish model systems. We found that Maid expression was greatest in zebrafish liver and that it increased following partial hepatectomy. Maid levels were also high in hepatic preneoplastic foci induced by treatment of zebrafish with diethylnitrosamine (DEN), but low in hepatocellular carcinomas (HCC), mixed tumors, and cholangiocarcinomas developing in these animals. In DEN-treated transgenic medaka overexpressing Maid, hepatic BrdU uptake and proliferation were reduced. After successive breedings, Maid transgenic medaka exhibited decreased movement and a higher incidence of abnormal spine curvature, possibly due to the senescence of spinal cord cells. Taken together, our results suggest that Maid levels can influence the progression of liver cancer. In conclusion, we found that Maid is important regulator of hepatocarconogenesis and aging.

A cell-based screening for TAZ activators identifies ethacridine, a widely used antiseptic and abortifacient, as a compound that promotes dephosphorylation of TAZ and inhibits adipogenesis in C3H10T1/2 cells

Transcriptional co-activator with PSD-95/Dlg-A/ZO-1 (PDZ)-binding motif (TAZ) regulates in cell proliferation and differentiation. In mesenchymal stem cells it promotes osteogenesis and myogenesis, and suppresses adipogenesis. TAZ activators are expected to prevent osteoporosis, obesity and muscle atrophy. TAZ activation induces epithelial-mesenchymal transition, confers stemness to cancer cells and leads to poor clinical prognosis in cancer patients. In this point of view, TAZ inhibitors should contribute to cancer therapy. Thus, TAZ attracts attention as a two-faced drug target. We screened for TAZ modulators by using human lung cancer A549 cells expressing the fluorescent reporter. Through this assay, we obtained TAZ activator candidates. We unexpectedly found that ethacridine, a widely used antiseptic and abortifacient, enhances the interaction of TAZ and protein phosphatases and increases unphosphorylated and nuclear TAZ. Ethacridine inhibits adipogenesis in mesenchymal C3H10T1/2 cells through the activation of TAZ. This finding suggests that ethacridine is a bona fide TAZ activator and supports that our assay is useful to discover TAZ activators.

YAP is essential for tissue tension to ensure vertebrate 3D body shape

Vertebrates have a unique 3D body shape in which correct tissue and organ shape and alignment are essential for function. For example, vision requires the lens to be centred in the eye cup which must in turn be correctly positioned in the head. Tissue morphogenesis depends on force generation, force transmission through the tissue, and response of tissues and extracellular matrix to force. Although a century ago D'Arcy Thompson postulated that terrestrial animal body shapes are conditioned by gravity, there has been no animal model directly demonstrating how the aforementioned mechano-morphogenetic processes are coordinated to generate a body shape that withstands gravity. Here we report a unique medaka fish (Oryzias latipes) mutant, hirame (hir), which is sensitive to deformation by gravity. hir embryos display a markedly flattened body caused by mutation of YAP, a nuclear executor of Hippo signalling that regulates organ size. We show that actomyosin-mediated tissue tension is reduced in hir embryos, leading to tissue flattening and tissue misalignment, both of which contribute to body flattening. By analysing YAP function in 3D spheroids of human cells, we identify the Rho GTPase activating protein ARHGAP18 as an effector of YAP in controlling tissue tension. Together, these findings reveal a previously unrecognised function of YAP in regulating tissue shape and alignment required for proper 3D body shape. Understanding this morphogenetic function of YAP could facilitate the use of embryonic stem cells to generate complex organs requiring correct alignment of multiple tissues.