Foxa3 (hepatocyte nuclear factor 3gamma ) is required for the regulation of hepatic GLUT2 expression and the maintenance of glucose homeostasis during a prolonged fast

FOXA3 regulates cholesterol metabolism to compensate for low uptake during the progression of lung adenocarcinoma

Cholesterol metabolism is vital for multiple cancer progression, while how cholesterol affects lung, a low-cholesterol tissue, for cancer metastasis and the underlying mechanism remain unclear. In this study, we found that metastatic lung adenocarcinoma cells acquire cellular dehydrocholesterol and cholesterol by endogenous cholesterol biosynthesis, instead of uptake upon cholesterol treatment. Besides, we demonstrated that exogenous cholesterol functions as signaling molecule to induce FOXA3, a key transcription factor for lipid metabolism via GLI2. Subsequently, ChIP-seq analysis and molecular studies revealed that FOXA3 transcriptionally activated Hmgcs1, an essential enzyme of cholesterol biosynthesis, to induce endogenous dehydrocholesterol and cholesterol level for membrane composition change and cell migration. Conversely, FOXA3 knockdown or knockout blocked cholesterol biosynthesis and lung adenocarcinoma metastasis in mice. In addition, the potent FOXA3 inhibitor magnolol suppressed metastatic gene programs in lung adenocarcinoma patient-derived organoids (PDOs). Altogether, our findings shed light onto unique cholesterol metabolism and FOXA3 contribution to lung adenocarcinoma metastasis.

Hepatic FOXA3 overexpression prevents Western diet-induced obesity and MASH through TGR5

Forkhead transcription factor 3 (FOXA3) has been shown to regulate metabolism and development. Hepatic FOXA3 is reduced in obesity and fatty liver disease. However, the role of hepatic FOXA3 in regulating obesity or steatohepatitis remains to be investigated. In this work, C57BL/6 mice were i.v. injected with AAV8-ALB-FOXA3 or the control virus. The mice were then fed a chow or Western diet for 16 weeks. The role of hepatic FOXA3 in energy metabolism and steatohepatitis was investigated. Plasma bile acid composition and the role of Takeda G protein-coupled receptor 5 (TGR5) in mediating the metabolic effects of FOXA3 were determined. Overexpression of hepatic FOXA3 reduced hepatic steatosis in chow-fed mice and attenuated Western diet-induced obesity and steatohepatitis. FOXA3 induced lipolysis and inhibited hepatic genes involved in bile acid uptake, resulting in elevated plasma bile acids. The beneficial effects of hepatic FOXA3 overexpression on Western diet-induced obesity and steatohepatitis were abolished in Tgr5-/- mice. Our data demonstrate that overexpression of hepatic FOXA3 prevents Western diet-induced obesity and steatohepatitis via activation of TGR5.

Characterisation of forkhead box protein A3 as a key transcription factor for hepatocyte regeneration

Background & Aims

Liver regeneration is vital for the recovery of liver function after injury, yet the underlying mechanism remains to be elucidated. Forkhead box protein A3 (FOXA3), a member of the forkhead box family, plays important roles in endoplasmic reticulum stress sensing, and lipid and glucose homoeostasis, yet its functions in liver regeneration are unknown.

Methods

Here, we explored whether Foxa3 regulates liver regeneration via acute and chronic liver injury mice models. We further characterised the molecular mechanism by chromatin immunoprecipitation sequencing and rescue experiments in vivo and in vitro. Then, we assessed the impact of Foxa3 pharmacological activation on progression and termination of liver regeneration. Finally, we confirmed the Foxa3-Cebpb axis in human liver samples.

Results

Foxa3 is dominantly expressed in hepatocytes and cholangiocytes and is induced upon partial hepatectomy (PH) or carbon tetrachloride (CCl4) administration. Foxa3 deficiency in mice decreased cyclin gene levels and delayed liver regeneration after PH, or acute or chronic i.p. CCl4 injection. Conversely, hepatocyte-specific Foxa3 overexpression accelerated hepatocytes proliferation and attenuated liver damage in an CCl4-induced acute model. Mechanistically, Foxa3 directly regulates Cebpb transcription, which is involved in hepatocyte division and apoptosis both in vivo and in vitro. Of note, Cebpb overexpression in livers of Foxa3-deficient mice rescued their defects in cell proliferation and regeneration upon CCl4 treatment. In addition, pharmacological induction of Foxa3 via cardamonin speeded up hepatocyte proliferation after PH, without interfering with liver regeneration termination. Finally, Cebpb and Ki67 levels had a positive correlation with Foxa3 expression in human chronic disease livers.

Conclusions

These data characterise Foxa3 as a vital regulator of liver regeneration, which may represent an essential factor to maintain liver mass after liver injury by governing Cebpb transcription.

Impact and Implications

Liver regeneration is vital for the recovery of liver function after chemical insults or hepatectomy, yet the underlying mechanism remains to be elucidated. Herein, via in vitro and in vivo models and analysis, we demonstrated that Forkhead box protein A3 (FOXA3), a Forkhead box family member, maintained normal liver regeneration progression by governing Cebpb transcription and proposed cardamonin as a lead compound to induce Foxa3 and accelerate liver repair, which signified that FOXA3 may be a potential therapeutic target for further preclinical study on treating liver injury.

The role of FOXA family transcription factors in glucolipid metabolism and NAFLD

Abnormal glucose metabolism and lipid metabolism are common pathological processes in many metabolic diseases, such as nonalcoholic fatty liver disease (NAFLD). Many studies have shown that the forkhead box (FOX) protein subfamily FOXA has a role in regulating glucolipid metabolism and is closely related to hepatic steatosis and NAFLD. FOXA exhibits a wide range of functions ranging from the initiation steps of metabolism such as the development of the corresponding metabolic organs and the differentiation of cells, to multiple pathways of glucolipid metabolism, to end-of-life problems of metabolism such as age-related obesity. The purpose of this article is to review and discuss the currently known targets and signal transduction pathways of FOXA in glucolipid metabolism. To provide more experimental evidence and basis for further research and clinical application of FOXA in the regulation of glucolipid metabolism and the prevention and treatment of NAFLD.

Genetic diversity and thermotolerance in Holstein cows: Pathway analysis and marker development using whole-genome sequencing

Heat stress causes extensive losses in the dairy sector, due to negative effects on milk production and reproduction. Cows have evolved a series of protective mechanisms, (physiological, biochemical, behavioural) to cope with the thermostressing environments, which have allowed the preservation of productive and reproductive potential of specific animals during summer; these animals are considered thermotolerant and could be used to design programs of selective breeding. These programs, targeting the generations of a population of heat-resistant animals, would increase the frequency of the desired phenotypes, tackling the financial losses on one hand and reducing the carbon footprints of the dairy sector on the other. The development of genomics techniques has enabled genome wide variant calling, to detect SNPs associated with the desired phenotypes. In this study, we used a comparative genomics approach to detect genetic variation associated with thermotolerance and to design molecular markers for characterizing the animals as tolerant/sensitive. A total of 40 cows from each group were split in four sequencing pools and a whole-genome sequencing approach was used. Results and conclusion: Genome-wide genetic variation between groups was characterized and enrichment analysis revealed specific pathways which participate in the adaptive mechanisms of thermotolerance, implicated into systemic and cellular responses, including the immune system functionality, Heat Stress and Unfolded Protein Response. The markers made a promising set of results, as specific SNPs in five genes encoding for Heat Shock Proteins were significantly associated with thermotolerance.

PAR2 promotes impaired glucose uptake and insulin resistance in NAFLD through GLUT2 and Akt interference

BACKGROUND AND AIMS

Insulin resistance and poor glycemic control are key drivers of the development of NAFLD and have recently been shown to be associated with fibrosis progression in NASH. However, the underlying mechanisms involving dysfunctional glucose metabolism and relationship with NAFLD/NASH progression remain poorly understood. We set out to determine whether protease-activated receptor 2 (PAR2), a sensor of extracellular inflammatory and coagulation proteases, links NAFLD and NASH with liver glucose metabolism.

APPROACH AND RESULTS

Here, we demonstrate that hepatic expression of PAR2 increases in patients and mice with diabetes and NAFLD/NASH. Mechanistic studies using whole-body and liver-specific PAR2-knockout mice reveal that hepatic PAR2 plays an unexpected role in suppressing glucose internalization, glycogen storage, and insulin signaling through a bifurcating Gq -dependent mechanism. PAR2 activation downregulates the major glucose transporter of liver, GLUT2, through Gq -MAPK-FoxA3 and inhibits insulin-Akt signaling through Gq -calcium-CaMKK2 pathways. Therapeutic dosing with a liver-homing pepducin, PZ-235, blocked PAR2-Gq signaling and afforded significant improvements in glycemic indices and HbA1c levels in severely diabetic mice.

CONCLUSIONS

This work provides evidence that PAR2 is a major regulator of liver glucose homeostasis and a potential target for the treatment of diabetes and NASH.

FOXA2 suppresses endometrial carcinogenesis and epithelial-mesenchymal transition by regulating enhancer activity

FOXA2 encodes a transcription factor mutated in 10% of endometrial cancers (ECs), with a higher mutation rate in aggressive variants. FOXA2 has essential roles in embryonic and uterine development. However, FOXA2’s role in EC is incompletely understood. Functional investigations using human and mouse EC cell lines revealed that FOXA2 controls endometrial epithelial gene expression programs regulating cell proliferation, adhesion, and endometrial-epithelial transition. In live animals, conditional inactivation of Foxa2 or Pten alone in endometrial epithelium did not result in ECs, but simultaneous inactivation of both genes resulted in lethal ECs with complete penetrance, establishing potent synergism between Foxa2 and PI3K signaling. Studies in tumor-derived cell lines and organoids highlighted additional invasion and cell growth phenotypes associated with malignant transformation and identified key mediators, including Myc and Cdh1. Transcriptome and cistrome analyses revealed that FOXA2 broadly controls gene expression programs through modification of enhancer activity in addition to regulating specific target genes, rationalizing its tumor suppressor functions. By integrating results from our cell lines, organoids, animal models, and patient data, our findings demonstrated that FOXA2 is an endometrial tumor suppressor associated with aggressive disease and with shared commonalities among its roles in endometrial function and carcinogenesis.

Epigenetic reprogramming of cell identity: lessons from development for regenerative medicine

Epigenetic mechanisms are known to define cell-type identity and function. Hence, reprogramming of one cell type into another essentially requires a rewiring of the underlying epigenome. Cellular reprogramming can convert somatic cells to induced pluripotent stem cells (iPSCs) that can be directed to differentiate to specific cell types. Trans-differentiation or direct reprogramming, on the other hand, involves the direct conversion of one cell type into another. In this review, we highlight how gene regulatory mechanisms identified to be critical for developmental processes were successfully used for cellular reprogramming of various cell types. We also discuss how the therapeutic use of the reprogrammed cells is beginning to revolutionize the field of regenerative medicine particularly in the repair and regeneration of damaged tissue and organs arising from pathological conditions or accidents. Lastly, we highlight some key challenges hindering the application of cellular reprogramming for therapeutic purposes.

FOXA3 induction under endoplasmic reticulum stress contributes to non-alcoholic fatty liver disease

BACKGROUND & AIMS

Chronic endoplasmic reticulum (ER) stress in the liver has been shown to play a causative role in non-alcoholic fatty liver disease (NAFLD) progression, yet the underlying molecular mechanisms remain to be elucidated. Forkhead box A3 (FOXA3), a member of the FOX family, plays critical roles in metabolic homeostasis, although its possible functions in ER stress and fatty liver progression are unknown.

METHODS

Adenoviral delivery, siRNA delivery, and genetic knockout mice were used to crease FOXA3 gain- or loss-of-function models. Tunicamycin (TM) and a high-fat diet (HFD) were used to induce acute or chronic ER stress in mice. Chromatin immunoprecipiation (ChIP)-seq, luciferase assay, and adenoviral-mediated downstream gene manipulations were performed to reveal the transcriptional axis involved. Key axis protein levels in livers from healthy donors and patients with NAFLD were assessed via immunohistochemical staining.

RESULTS

FOXA3 transcription is specifically induced by XBP1s upon ER stress. FOXA3 exacerbates the excessive lipid accumulation caused by the acute ER-inducer TM, whereas FOXA3 deficiency in hepatocytes and mice alleviates it. Importantly, FOXA3 deficiency in mice reduced diet-induced chronic ER stress, fatty liver, and insulin resistance. In addition, FOXA3 suppression via siRNA or adeno-associated virus delivery ameliorated the fatty liver phenotype in HFD-fed and db/db mice. Mechanistically, ChIP-Seq analysis revealed that FOXA3 directly regulates Period1 (Per1) transcription, which in turn promotes the expression of lipogenic genes, including Srebp1c, thus enhancing lipid synthesis. Of pathophysiological significance, FOXA3, PER1, and SREBP1c levels were increased in livers of obese mice and patients with NAFLD.

CONCLUSION

The present study identified FOXA3 as the bridging molecule that links ER stress and NAFLD progression. Our results highlighted the role of the XBP1s-FOXA3-PER1/Srebp1c transcriptional axis in the development of NAFLD and identified FOXA3 as a potential therapeutic target for fatty liver disease.

LAY SUMMARY

The molecular mechanisms linking endoplasmic reticulum stress to non-alcoholic fatty liver disease (NAFLD) progression remain undefined. Herein, via in vitro and in vivo analysis, we identified Forkhead box A3 (FOXA3) as a key bridging molecule. Of pathophysiological significance, FOXA3 protein levels were increased in livers of obese mice and patients with NAFLD, indicating that FOXA3 could be a potential therapeutic target in fatty liver disease.

The Dynamics of Transcriptional Activation by Hepatic Reprogramming Factors

Specific combinations of two transcription factors (Hnf4α plus Foxa1, Foxa2, or Foxa3) can induce direct conversion of mouse fibroblasts into hepatocyte-like cells. However, the molecular mechanisms underlying hepatic reprogramming are largely unknown. Here, we show that the Foxa protein family members and Hnf4α sequentially and cooperatively bind to chromatin to activate liver-specific gene expression. Although all Foxa proteins bind to and open regions of closed chromatin as pioneer factors, Foxa3 has the unique potential of transferring from the distal to proximal regions of the transcription start site of target genes, binding RNA polymerase II, and co-traversing target genes. These distinctive characteristics of Foxa3 are essential for inducing the hepatic fate in fibroblasts. Similar functional coupling of transcription factors to RNA polymerase II may occur in other contexts whereby transcriptional activation can induce cell differentiation.

Transcriptional, epigenetic and microRNA regulation of growth plate

Endochondral ossification is a critical event in bone formation, particularly in long shaft bones. Many cellular differentiation processes work in concert to facilitate the generation of cartilage primordium to formation of trabecular structures, all of which occur within the growth plate. Previous studies have revealed that the growth plate is tightly regulated by various transcription factors, epigenetic systems, and microRNAs. Hence, understanding these mechanisms that regulate the growth plate is crucial to furthering the current understanding on skeletal diseases, and in formulating effective treatment strategies. In this review, we focus on describing the function and mechanisms of the transcription factors, epigenetic systems, and microRNAs known to regulate the growth plate.

Altered Transcription Factor Binding and Gene Bivalency in Islets of Intrauterine Growth Retarded Rats

Intrauterine growth retardation (IUGR), which induces epigenetic modifications and permanent changes in gene expression, has been associated with the development of type 2 diabetes. Using a rat model of IUGR, we performed ChIP-Seq to identify and map genome-wide histone modifications and gene dysregulation in islets from 2- and 10-week rats. IUGR induced significant changes in the enrichment of H3K4me3, H3K27me3, and H3K27Ac marks in both 2-wk and 10-wk islets, which were correlated with expression changes of multiple genes critical for islet function in IUGR islets. ChIP-Seq analysis showed that IUGR-induced histone mark changes were enriched at critical transcription factor binding motifs, such as C/EBPs, Ets1, Bcl6, Thrb, Ebf1, Sox9, and Mitf. These transcription factors were also identified as top upstream regulators in our previously published transcriptome study. In addition, our ChIP-seq data revealed more than 1000 potential bivalent genes as identified by enrichment of both H3K4me3 and H3K27me3. The poised state of many potential bivalent genes was altered by IUGR, particularly Acod1, Fgf21, Serpina11, Cdh16, Lrrc27, and Lrrc66, key islet genes. Collectively, our findings suggest alterations of histone modification in key transcription factors and genes that may contribute to long-term gene dysregulation and an abnormal islet phenotype in IUGR rats.

Functionally analyzing the important roles of hepatocyte nuclear factor 3 (FoxA) in tumorigenesis

Transcriptional factors (TFs) play a central role in governing gene expression under physiological conditions including the processes of embryonic development, metabolic homeostasis and response to extracellular stimuli. Conceivably, the aberrant dysregulations of TFs would dominantly result in various human disorders including tumorigenesis, diabetes and neurodegenerative diseases. Serving as the most evolutionarily reserved TFs, Fox family TFs have been explored to exert distinct biological functions in neoplastic development, by manipulating diverse gene expression. Recently, among the Fox family members, the pilot roles of FoxAs attract more attention due to their functions as both pioneer factor and transcriptional factor in human tumorigenesis, particularly in the sex-dimorphism tumors. Therefore, the pathological roles of FoxAs in tumorigenesis have been well-explored in modulating inflammation, immune response and metabolic homeostasis. In this review, we comprehensively summarize the impressive progression of FoxA functional annotation, clinical relevance, upstream regulators and downstream effectors, as well as valuable animal models, and highlight the potential strategies to target FoxAs for cancer therapies.

Hepatotoxicity of tricyclazole in zebrafish (Danio rerio)

Tricyclazole is widely used in agriculture as a pesticide, but its toxicity in vertebrates is currently poorly evaluated. In this study, we used zebrafish to assess the toxicity of tricyclazole. We found that tricyclazole induces liver damage, or hepatotoxicity, in zebrafish, during both development and adulthood. In embryos, we found that tricyclazole affected the liver development rather than other endodermal tissues such as gut and pancreas. In both embryos and adult zebrafish livers, tricyclazole disrupted the relationship between oxidant and antioxidant system and resulted in reactive oxygen species (ROS) overload. Meanwhile, it triggered hepatocyte apoptosis and disturbed carbohydrate/lipid metabolism and energy demand systems. These results suggested that tricyclazole could cause severe consequences for vertebrate hepatic development and function.

Hepatic Forkhead Box Protein A3 Regulates ApoA-I (Apolipoprotein A-I) Expression, Cholesterol Efflux, and Atherogenesis

OBJECTIVE

To determine the role of hepatic FOXA3 (forkhead box A3) in lipid metabolism and atherosclerosis. Approach and Results: Hepatic FOXA3 expression was reduced in diabetic or high fat diet-fed mice or patients with nonalcoholic steatohepatitis. We then used adenoviruses to overexpress or knock down hepatic FOXA3 expression. Overexpression of FOXA3 in the liver increased hepatic ApoA-I (apolipoprotein A-I) expression, plasma HDL-C (high-density lipoprotein cholesterol) level, macrophage cholesterol efflux, and macrophage reverse cholesterol transport. In contrast, knockdown of hepatic FOXA3 expression had opposite effects. We further showed that FOXA3 directly bound to the promoter of the Apoa1 gene to regulate its transcription. Finally, AAV8 (adeno-associated virus serotype 8)-mediated overexpression of human FOXA3 in the hepatocytes of Apoe^-/- (apolipoprotein E-deficient) mice raised plasma HDL-C levels and significantly reduced atherosclerotic lesions.

CONCLUSIONS

Hepatocyte FOXA3 protects against atherosclerosis by inducing ApoA-I and macrophage reverse cholesterol transport.

Chemical cocktails enable hepatic reprogramming of human urine-derived cells with a single transcription factor

Human liver or hepatocyte transplantation is limited by a severe shortage of donor organs. Direct reprogramming of other adult cells into hepatic cells may offer a solution to this problem. In a previous study, we have generated hepatocyte-like cells from mouse fibroblasts using only one transcription factor (TF) plus a chemical cocktail. Here, we show that human urine-derived epithelial-like cells (hUCs) can also be transdifferentiated into human hepatocyte-like cells (hiHeps) using one TF (Foxa3, Hnf1α, or Hnf4α) plus the same chemical cocktail CRVPTD (C, CHIR99021; R, RepSox; V, VPA; P, Parnate; T, TTNPB; and D, Dznep). These hiHeps express multiple hepatocyte-specific genes and display functions characteristic of mature hepatocytes. With the introduction of the large T antigen, these hiHeps can be expanded in vitro and can restore liver function in mice with concanavalin-A-induced acute liver failure. Our study provides a strategy to generate functional hepatocyte-like cells from hUCs by using a single TF plus a chemical cocktail.

Upregulated forkhead-box A3 elevates the expression of forkhead-box A1 and forkhead-box A2 to promote metastasis in esophageal cancer

Esophageal cancer (EC) is one of the most lethal cancers currently known. Members of the forkhead-box A (FOXA) family, including FOXA1 and FOXA2, have been reported to regulate EC progression. However, the role of FOXA3, which is another FOXA member, has not yet been investigated. In the present study, public dataset analyses and immunohistochemistry of 96 samples from patients with EC were performed to determine the potential roles of FOXA3 in EC. The results revealed that FOXA3 was significantly upregulated in EC tumor tissues and Barrett's esophagus tissues. In addition, FOXA3 upregulation was positively associated with tumor invasion, distant metastasis, tumor-node-metastasis stage and shorter overall survival in patients with EC, and multivariate analysis identified FOXA3 as an independent prognostic marker. In vitro experiments demonstrated that the migratory and invasive abilities of EC109 and EC9706 cell lines were inhibited following FOXA3 knockdown. Notably, FOXA3 expression levels were positively correlated with FOXA1 and FOXA2 expression levels according to The Cancer Genome Atlas dataset analysis. Furthermore, FOXA3 knockdown decreased the expression levels of FOXA1 and FOXA2 in EC109 and EC9706 cell lines. Conversely, FOXA1 or FOXA2 overexpression compensated for the effects of FOXA3 knockdown on the migratory and invasive capacities of EC cells. In conclusion, the present study demonstrated that FOXA3 upregulation in EC cells promoted metastasis through regulation of other FOXA members.

Developmental exposure to DEHP alters hepatic glucose uptake and transcriptional regulation of GLUT2 in rat male offspring

Type-2-diabetes (T2D) is a long term metabolic disorder characterized by high blood glucose and insulin resistance. It has become an alarming issue globally due to tremendous increase in number of new subjects every year. Apart from the classical factors, there are few non-classical factors such as environmental pollutants, endocrine disrupting chemicals (EDCs) which also play a major role in pathogenesis of T2D. Di-(2-ethylhexyl) phthalate (DEHP) is a commonly used plasticizer which is an endocrine disrupting chemical. It is used in the plastic industry to give flexibility and durability. Its widespread use resulted in constant presence in the environment and human are under high risk of exposure to this compound. There are literature available stating that DEHP has an impact on glucose homeostasis. Glucose transporter 2 (GLUT2) is a principal transporter of glucose in liver and it is a bi-directional transporter. We investigated whether DEHP exposure during gestation and lactation alters transcriptional regulation of GLUT2 and epigenetics changes in the rat F₁ male offspring at adulthood. Pregnant rats were divided into three groups and administered with DEHP (10 and 100 mg /kg /day) or olive oil from gestational day (GD) 9- to postnatal day (PND) 21 through oral gavage. DEHP treated rats showed decreased glucose uptake and oxidation, decreased mRNA levels of insulin receptor (IR), GLUT2 and reduced GLUT2 protein in cytosol but unaltered level in plasma membrane. There are three main transcription factors (SREBP1c, HNF3β and HNF1α) involved in the regulation of GLUT2 gene and all these proteins were reduced in DEHP exposed groups. A weak interaction of the transcription factors (SREBP1c & HNF1α) with GLUT2 gene promoter was observed in DEHP-treated groups. Hyper- methylation of IR and GLUT2 gene promoter was observed in both the DEHP-exposed groups compared to control. The present study reveals that DEHP exposure alters transcriptional regulation of GLUT2 and imposes epigenetic alteration in IR and GLUT2 gene promoters which plays a significant role in the development of metabolic abnormality in F₁ male offspring at adulthood.

The molecular functions of hepatocyte nuclear factors - In and beyond the liver

The hepatocyte nuclear factors (HNFs) namely HNF1α/β, FOXA1/2/3, HNF4α/γ and ONECUT1/2 are expressed in a variety of tissues and organs, including the liver, pancreas and kidney. The spatial and temporal manner of HNF expression regulates embryonic development and subsequently the development of multiple tissues during adulthood. Though the HNFs were initially identified individually based on their roles in the liver, numerous studies have now revealed that the HNFs cross-regulate one another and exhibit synergistic relationships in the regulation of tissue development and function. The complex HNF transcriptional regulatory networks have largely been elucidated in rodent models, but less so in human biological systems. Several heterozygous mutations in these HNFs were found to cause diseases in humans but not in rodents, suggesting clear species-specific differences in mutational mechanisms that remain to be uncovered. In this review, we compare and contrast the expression patterns of the HNFs, the HNF cross-regulatory networks and how these liver-enriched transcription factors serve multiple functions in the liver and beyond, extending our focus to the pancreas and kidney. We also summarise the insights gained from both human and rodent studies of mutations in several HNFs that are known to lead to different disease conditions.

3,5-diiodothyronine (3,5-T2) reduces blood glucose independently of insulin sensitization in obese mice

AIM

Thyroid hormones regulate metabolic response. While triiodothyronine (T3) is usually considered to be the active form of thyroid hormone, one form of diiodothyronine (3,5-T2) exerts T3-like effects on energy consumption and lipid metabolism. 3,5-T2 also improves glucose tolerance in rats and 3,5-T2 levels correlate with fasting glucose in humans. Presently, however, little is known about mechanisms of 3,5-T2 effects on glucose metabolism. Here, we set out to compare effects of T3, 3,5-T2 and another form of T2 (3,3-T2) in a mouse model of diet-induced obesity and determined effects of T3 and 3,5-T2 on markers of classical insulin sensitization to understand how diiodothyronines influence blood glucose.

METHODS

Cell- and protein-based assays of thyroid hormone action. Assays of metabolic parameters in mice. Analysis of transcript and protein levels in different tissues by qRT-PCR and Western blot.

RESULTS

T3 and 3,5-T2 both reduce body weight, adiposity and body temperature despite increased food intake. 3,3'-T2 lacks these effects. T3 and 3,5-T2 reduce blood glucose levels, whereas 3,3'-T2 worsens glucose tolerance. Neither T3 nor 3,5-T2 affects markers of insulin sensitization in skeletal muscle or white adipose tissue (WAT), but both reduce hepatic GLUT2 glucose transporter levels and glucose output. T3 and 3,5-T2 also induce expression of mitochondrial uncoupling proteins (UCPs) 3 and 1 in skeletal muscle and WAT respectively.

CONCLUSIONS

3,5-T2 influences glucose metabolism in a manner that is distinct from insulin sensitization and involves reductions in hepatic glucose output and changes in energy utilization.

Forkhead box A3 attenuated the progression of fibrosis in a rat model of biliary atresia

Biliary atresia is a rare, devastating disease of infants where a fibroinflammatory process destroys the bile ducts, leading to fibrosis and biliary cirrhosis, and death if untreated. The cause and pathogenesis remain largely unknown. We tried to investigate factors involved in biliary atresia, especially forkhead box A3 (Foxa3), which might exert a role in the treatment of liver disease. We used RNA sequencing to sequence the whole transcriptomes of livers from six biliary atresia and six choledochal cysts patients. Then, we employed a rat disease model by bile duct ligation (BDL) and adenovirus transduction to address the function of Foxa3 in biliary atresia. We found that tight junction, adherence junction, cell cycle, apoptosis, chemokine singling, VEGF and MAPK signaling pathways were enriched in biliary atresia livers. We showed that Foxa3 expression was notably decreased in liver samples from biliary atresia patients. More importantly, we found that its lower expression predicted a poorer overall survival of biliary atresia patients. Rats that received BDL surgery and Foxa3 expression adenovirus resulted in a significant decrease in the deposition of collagen, and expression of profibrotic cytokines (transforming growth factor-β and connective tissue growth factor) and fibrosis markers (α-smooth muscle actin, collagen I and collagen III), as compared with rats that received BDL surgery and control adenovirus. Our data suggested a protection role for Foxa3 during the progression of liver fibrosis in biliary atresia, and thereby supported increasing Foxa3 as a targeted treatment strategy.

The activity of the carbamoyl phosphate synthase 1 promoter in human liver-derived cells is dependent on hepatocyte nuclear factor 3-beta

Carbamoyl phosphate synthase 1 (CPS1) is the rate‐limiting enzyme in the first step of the urea cycle and an indispensable enzyme in the metabolism of human liver. However, CPS1 epigenetic regulation involves promoter analysis and the role of liver‐enriched transcription factors (LETFs), which is not fully elucidated. In this work, the promoter region of hCPS1 gene was cloned, and its activity was investigated. An LETF, hepatocyte nuclear factor 3‐beta (HNF3β), was found to promote the transcriptional expression of CPS1 in liver‐derived cell lines. In addition, dual‐luciferase reporter assay shows that the essential binding sites of the HNF3β may exist in the oligonucleotide −70 nt to +73 nt. Two putative binding sites are available for HNF3β. Mutation analysis results show that the binding site 2 of HNF3β was effective, and the transcriptional activity of CPS1 promoter significantly decreased after mutation. Electrophoretic mobile shift assay (EMSA) and ChIP assay confirmed that HNF3β can interact with the binding site in the CPS1 promoter region of −70 nt to +73 nt promoter region in vivo and in vitro to regulate the transcription of CPS1. Moreover, HNF3β overexpression enhanced the transcription of CPS1 and consequently improved the mRNA and protein levels of CPS1, whereas the knockdown of HNF3β showed the opposite effects. Finally, urea production in cells was measured, and ammonia detoxification improved significantly in cells after transfection with HNF3β. HNF3β plays a vital role in regulation of CPS1 gene and could promote the metabolism of ammonia by regulating CPS1 expression.

Hepatic deficiency of the pioneer transcription factor FoxA restricts hepatitis B virus biosynthesis by the developmental regulation of viral DNA methylation

The FoxA family of pioneer transcription factors regulates hepatitis B virus (HBV) transcription, and hence viral replication. Hepatocyte-specific FoxA-deficiency in the HBV transgenic mouse model of chronic infection prevents the transcription of the viral DNA genome as a result of the failure of the developmentally controlled conversion of 5-methylcytosine residues to cytosine during postnatal hepatic maturation. These observations suggest that pioneer transcription factors such as FoxA, which mark genes for expression at subsequent developmental steps in the cellular differentiation program, mediate their effects by reversing the DNA methylation status of their target genes to permit their ensuing expression when the appropriate tissue-specific transcription factor combinations arise during development. Furthermore, as the FoxA-deficient HBV transgenic mice are viable, the specific developmental timing, abundance and isoform type of pioneer factor expression must permit all essential liver gene expression to occur at a level sufficient to support adequate liver function. This implies that pioneer transcription factors can recognize and mark their target genes in distinct developmental manners dependent upon, at least in part, the concentration and affinity of FoxA for its binding sites within enhancer and promoter regulatory sequence elements. This selective marking of cellular genes for expression by the FoxA pioneer factor compared to HBV may offer the opportunity for the specific silencing of HBV gene expression and hence the resolution of chronic HBV infections which are responsible for approximately one million deaths worldwide annually due to liver cirrhosis and hepatocellular carcinoma.

This study demonstrates the connection between FoxA expression and gene silencing by DNA methylation in vivo during liver maturation. Insufficient FoxA expression results in selective developmentally regulated hepatitis B virus (HBV) silencing by DNA methylation. To our knowledge, this is the first in vivo demonstration that pioneer factors such as FoxA function by mediating the developmental demethylation of their target genes, leading to their tissue specific gene expression. Furthermore, our results strongly imply that the marking of cellular target genes for subsequent transcription later in development is dependent upon the level and timing of FoxA expression plus its affinity for its target sequences within enhancer and promoter regions. Consequently, these findings suggest that the appropriate control of FoxA activity during development could lead to the transcriptional inactivation of nuclear HBV covalently closed circular DNA by methylation and hence resolution of chronic HBV infection. This represents a clinical goal that current therapies are unable to attain, and hence suggests a potential route to a cure for this chronic infection which kills approximately 1 million individuals annually.

DNA methylation alters transcriptional rates of differentially expressed genes and contributes to pathophysiology in mice fed a high fat diet

OBJECTIVE

Overnutrition can alter gene expression patterns through epigenetic mechanisms that may persist through generations. However, it is less clear if overnutrition, for example a high fat diet, modifies epigenetic control of gene expression in adults, or by what molecular mechanisms, or if such mechanisms contribute to the pathology of the metabolic syndrome. Here we test the hypothesis that a high fat diet alters hepatic DNA methylation, transcription and gene expression patterns, and explore the contribution of such changes to the pathophysiology of obesity.

METHODS

RNA-seq and targeted high-throughput bisulfite DNA sequencing were used to undertake a systematic analysis of the hepatic response to a high fat diet. RT-PCR, chromatin immunoprecipitation and in vivo knockdown of an identified driver gene, Phlda1, were used to validate the results.

RESULTS

A high fat diet resulted in the hypermethylation and decreased transcription and expression of Phlda1 and several other genes. A subnetwork of genes associated with Phlda1 was identified from an existing Bayesian gene network that contained numerous hepatic regulatory genes involved in lipid and body weight homeostasis. Hepatic-specific depletion of Phlda1 in mice decreased expression of the genes in the subnetwork, and led to increased oil droplet size in standard chow-fed mice, an early indicator of steatosis, validating the contribution of this gene to the phenotype.

CONCLUSIONS

We conclude that a high fat diet alters the epigenetics and transcriptional activity of key hepatic genes controlling lipid homeostasis, contributing to the pathophysiology of obesity.

Fox transcription factors: from development to disease

Forkhead box (Fox) transcription factors are evolutionarily conserved in organisms ranging from yeast to humans. They regulate diverse biological processes both during development and throughout adult life. Mutations in many Fox genes are associated with human disease and, as such, various animal models have been generated to study the function of these transcription factors in mechanistic detail. In many cases, the absence of even a single Fox transcription factor is lethal. In this Primer, we provide an overview of the Fox family, highlighting several key Fox transcription factor families that are important for mammalian development.

Single-Cell RNAseq Reveals That Pancreatic β-Cells From Very Old Male Mice Have a Young Gene Signature

Aging improves pancreatic β-cell function in mice. This is a surprising finding because aging is typically associated with functional decline. We performed single-cell RNA sequencing of β-cells from 3- and 26-month-old mice to explore how changes in gene expression contribute to improved function with age. The old mice were healthy and had reduced blood glucose levels and increased β-cell mass, which correlated to their body weight. β-Cells from young and old mice had similar transcriptome profiles. In fact, only 193 genes (0.89% of all detected genes) were significantly regulated (≥2-fold; false discovery rate < 0.01; normalized counts > 5). Of these, 183 were down-regulated and mainly associated with pathways regulating gene expression, cell cycle, cell death, and survival as well as cellular movement, function, and maintenance. Collectively our data show that β-cells from very old mice have transcriptome profiles similar to those of young mice. These data support previous findings that aging is not associated with reduced β-cell mass or functional β-cell decline in mice.

Resveratrol improves glycemic control in insulin-treated diabetic rats: participation of the hepatic territory

BACKGROUND

Resveratrol is a natural polyphenol that has been proposed to improve glycemic control in diabetes, by mechanisms that involve improvement in insulin secretion and activity. In type 1 diabetes (T1D), in which insulin therapy is obligatory, resveratrol treatment has never been investigated. The present study aimed to evaluate resveratrol as an adjunctive agent to insulin therapy in a T1D-like experimental model.

METHODS

Rats were rendered diabetic by streptozotocin (STZ) treatment. Twenty days later, four groups of animals were studied: non-diabetic (ND); diabetic treated with placebo (DP); diabetic treated with insulin (DI) and diabetic treated with insulin plus resveratrol (DIR). After 30 days of treatment, 24-hour urine was collected; then, blood, soleus muscle, proximal small intestine, renal cortex and liver were sampled. Specific glucose transporter proteins were analyzed (Western blotting) in each territory of interest. Solute carrier family 2 member 2 (Slc2a2), phosphoenolpyruvate carboxykinase (Pck1) and glucose-6-phosphatase catalytic subunit (G6pc) mRNAs (qPCR), glycogen storage and sirtuin 1 (SIRT1) activity were analyzed in liver.

RESULTS

Diabetes induction increased blood glucose, plasma fructosamine concentrations, and glycosuria. Insulin therapy partially recovered the glycemic control; however, resveratrol as adjunctive therapy additionally improved glycemic control and restored plasma fructosamine concentration to values of non-diabetic rats. Resveratrol did not alter the expression of the glucose transporters GLUT2 and SGLT1 in the intestine, GLUT2 and SGLT2 in kidney and GLUT4 in soleus, suggesting that fluxes of glucose in these territories were unaltered. Differently, in liver, resveratrol promoted a reduction in Slc2a2, Pck1, and G6pc mRNAs, as well as in GLUT2 protein (P < 0.05, DIR vs. DI); besides, it increased (P < 0.01, DIR vs. DI) the hepatic glycogen content, and SIRT1 protein.

CONCLUSIONS

Resveratrol is able to improve glycemic control in insulin-treated T1D-like rats. This effect seems not to involve changes in glucose fluxes in the small intestine, renal proximal tubule, and soleus skeletal muscle; but to be related to several changes in the liver, where downregulation of Slc2a2/GLUT2, Pck1, and G6pc expression was observed, favoring reduction of glucose production and efflux. Besides, resveratrol increased SIRT1 nuclear protein content in liver, which may be related to the observed gene expression regulations.

Forkhead box A3 mediates glucocorticoid receptor function in adipose tissue

Glucocorticoids (GCs) are widely prescribed anti-inflammatory agents, but their chronic use leads to undesirable side effects such as excessive expansion of adipose tissue. We have recently shown that the forkhead box protein A3 (Foxa3) is a calorie-hoarding factor that regulates the selective enlargement of epididymal fat depots and suppresses energy expenditure in a nutritional- and age-dependent manner. It has been demonstrated that Foxa3 levels are elevated in adipose depots in response to high-fat diet regimens and during the aging process; however no studies to date have elucidated the mechanisms that control Foxa3's expression in fat. Given the established effects of GCs in increasing visceral adiposity and in reducing thermogenesis, we assessed the existence of a possible link between GCs and Foxa3. Computational prediction analysis combined with molecular studies revealed that Foxa3 is regulated by the glucocorticoid receptor (GR) in preadipocytes, adipocytes, and adipose tissues and is required to facilitate the binding of the GR to its target gene promoters in fat depots. Analysis of the long-term effects of dexamethasone treatment in mice revealed that Foxa3 ablation protects mice specifically against fat accretion but not against other pathological side effects elicited by this synthetic GC in tissues such as liver, muscle, and spleen. In conclusion our studies provide the first demonstration, to our knowledge, that Foxa3 is a direct target of GC action in adipose tissues and point to a role of Foxa3 as a mediator of the side effects induced in fat tissues by chronic treatment with synthetic steroids.

Calorie hoarding and thrifting: Foxa3 finds a way

Obesity and diabetes are major health concerns worldwide. Western diets, often calorically rich, paired with sedentary habits are driving the current worldwide epidemic of pediatric and adult obesity. In addition, age related energy imbalances lead to increased adiposity and metabolic disorders later in life, making the middle aged population particularly susceptible. Here we discuss how Forkhead box A3 (Foxa3), a family member of the forkhead box binding proteins, can potentially contribute to pathology by playing a double role in metabolism. Recent data revealed that Foxa3 favors the selective expansion of visceral depots under high caloric conditions (e.g., high fat diet) and suppresses subcutaneous fat tissue energy expenditure during aging. This evidence suggests that Foxa3 acts to both preserve and conserve calories, by accumulating fat and by reducing metabolic burn. In other words, Foxa3 appears to function to enable energy "hoarding," which may be critical for survival of organisms with intermittent exposure to external caloric sources, but pathologic in circumstances where calories are abundant. Understanding how this "calorie hoarder gene" functions may suggest approaches to combat obesity and associated metabolic disorders.

Loss of Foxm1 Results in Reduced Somatotrope Cell Number during Mouse Embryogenesis

FOXM1, a member of the forkhead box transcription factor family, plays a key role in cell cycling progression by regulating the expression of critical G1/S and G2/M phase transition genes. In vivo studies reveal that Foxm1 null mice have a 91% lethality rate at e18.5 due to significant cardiovascular and hepatic hypoplasia. Thus, FOXM1 has emerged as a key protein regulating mitotic division and cell proliferation necessary for embryogenesis. In the current study, we assess the requirement for Foxm1 in the developing pituitary gland. We find that Foxm1 is expressed in the pituitary at embryonic days 10.5-e18.5 and localizes with markers for active cell proliferation (BrdU). Interestingly, direct analysis of Foxm1 null mice at various embryonic ages, reveals no difference in gross pituitary morphology or cell proliferation. We do observe a downward trend in overall pituitary cell number and a small reduction in pituitary size in e18.5 embryos suggesting there may be subtle changes in pituitary proliferation not detected with our proliferation makers. Consistent with this, Foxm1 null mice have reductions in both the somatotrope and gonadotrope cell populations.

A pathway to bone: signaling molecules and transcription factors involved in chondrocyte development and maturation

Decades of work have identified the signaling pathways that regulate the differentiation of chondrocytes during bone formation, from their initial induction from mesenchymal progenitor cells to their terminal maturation into hypertrophic chondrocytes. Here, we review how multiple signaling molecules, mechanical signals and morphological cell features are integrated to activate a set of key transcription factors that determine and regulate the genetic program that induces chondrogenesis and chondrocyte differentiation. Moreover, we describe recent findings regarding the roles of several signaling pathways in modulating the proliferation and maturation of chondrocytes in the growth plate, which is the 'engine' of bone elongation.

Heterozygous deletion of FOXA2 segregates with disease in a family with heterotaxy, panhypopituitarism, and biliary atresia

Biliary atresia (BA) is a pediatric cholangiopathy with unknown etiology occurring in isolated and syndromic forms. Laterality defects affecting the cardiovascular and gastrointestinal systems are the most common features present in syndromic BA. Most cases are sporadic, although reports of familial cases have led to the hypothesis of genetic susceptibility in some patients. We identified a child with BA, malrotation, and interrupted inferior vena cava whose father presented with situs inversus, polysplenia, panhypopituitarism, and mildly dysmorphic facial features. Chromosomal microarray analysis demonstrated a 277 kb heterozygous deletion on chromosome 20, which included a single gene, FOXA2, in the proband and her father. This deletion was confirmed to be de novo in the father. The proband and her father share a common diagnosis of heterotaxy, but they also each presented with a variety of other issues. Further genetic screening revealed that the proband carried an additional protein-altering polymorphism (rs1904589; p.His165Arg) in the NODAL gene that is not present in the father, and this variant has been shown to decrease expression of the gene. As FOXA2 can be a regulator of NODAL expression, we propose that haploinsufficiency for FOXA2 combined with a decreased expression of NODAL is the likely cause for syndromic BA in this proband.

dCaP: detecting differential binding events in multiple conditions and proteins

BACKGROUND

Current ChIP-seq studies are interested in comparing multiple epigenetic profiles across several cell types and tissues simultaneously for studying constitutive and differential regulation. Simultaneous analysis of multiple epigenetic features in many samples can gain substantial power and specificity than analyzing individual features and/or samples separately. Yet there are currently few tools can perform joint inference of constitutive and differential regulation in multi-feature-multi-condition contexts with statistical testing. Existing tools either test regulatory variation for one factor in multiple samples at a time, or for multiple factors in one or two samples. Many of them only identify binary rather than quantitative variation, which are sensitive to threshold choices.

RESULTS

We propose a novel and powerful method called dCaP for simultaneously detecting constitutive and differential regulation of multiple epigenetic factors in multiple samples. Using simulation, we demonstrate the superior power of dCaP compared to existing methods. We then apply dCaP to two datasets from human and mouse ENCODE projects to demonstrate its utility. We show in the human dataset that the cell-type specific regulatory loci detected by dCaP are significantly enriched near genes with cell-type specific functions and disease relevance. We further show in the mouse dataset that dCaP captures genomic regions showing significant signal variations for TAL1 occupancy between two mouse erythroid cell lines. The novel TAL1 occupancy loci detected only by dCaP are highly enriched with GATA1 occupancy and differential gene expression, while those detected only by other methods are not.

CONCLUSIONS

Here, we developed a novel approach to utilize the cooperative property of proteins to detect differential binding given multivariate ChIP-seq samples to provide better power, aiming for complementing existing approaches and providing new insights in the method development in this field.

microRNA-141 inhibits cell proliferation and invasion and promotes apoptosis by targeting hepatocyte nuclear factor-3β in hepatocellular carcinoma cells

Background

Hepatocyte nuclear factor-3β (HNF-3β) plays a critical role in hepatocyte differentiation and controls liver-specific gene expression during the development of hepatocellular carcinoma (HCC), but the molecular basis of this process has not been fully elucidated. microRNAs (miRNAs) are powerful, post-transcriptional regulators of gene expression. Whether miRNAs can impact the effects of HNF-3β in HCC is still unknown.

Methods

HNF-3β and miR-141 expression levels were detected in HepG2 cells, using real-time quantitative RT-PCR (qRT-PCR). Luciferase reporter assays and Western blots were used to validate HNF-3β as a direct target gene of miR-141. Cell proliferation, invasion, and apoptosis were also examined to confirm whether miR-141 could impact on HNF-3β in HCC.

Results

In this study, we found that HNF-3β protein levels were consistently upregulated in HCC clinical tissues compared with matched normal adjacent tissues. However, the mRNA levels of HNF-3β varied in random tissues, suggesting that a post-transcriptional mechanism was involved in its regulation. We used bioinformatic analyses to search for miRNAs that could potentially target HNF-3β, and identified specific targeting sites for miR-141 in the 3′-untranslated region (3′-UTR) of the HNF-3β gene. By overexpressing miR-141 in HepG2 cells, we experimentally validated that miR-141 directly regulated HNF-3β expression. Furthermore, the biological consequences of targeting HNF-3β by miR-141 were examined using cell proliferation, invasion and apoptosis assays in vitro. We demonstrated that the repression of HNF-3β by miR-141 suppressed the proliferation and invasion and promoted the apoptosis of HepG2 cells.

Conclusions

miR-141 functions as a tumor suppressor in HCC cells through the inhibition of HNF-3β translation.

Role of forkhead box protein A3 in age-associated metabolic decline

Aging is associated with increased adiposity and diminished thermogenesis, but the critical transcription factors influencing these metabolic changes late in life are poorly understood. We recently demonstrated that the winged helix factor forkhead box protein A3 (Foxa3) regulates the expansion of visceral adipose tissue in high-fat diet regimens; however, whether Foxa3 also contributes to the increase in adiposity and the decrease in brown fat activity observed during the normal aging process is currently unknown. Here we report that during aging, levels of Foxa3 are significantly and selectively up-regulated in brown and inguinal white fat depots, and that midage Foxa3-null mice have increased white fat browning and thermogenic capacity, decreased adipose tissue expansion, improved insulin sensitivity, and increased longevity. Foxa3 gain-of-function and loss-of-function studies in inguinal adipose depots demonstrated a cell-autonomous function for Foxa3 in white fat tissue browning. Furthermore, our analysis revealed that the mechanisms of Foxa3 modulation of brown fat gene programs involve the suppression of peroxisome proliferator activated receptor γ coactivtor 1 α (PGC1α) levels through interference with cAMP responsive element binding protein 1-mediated transcriptional regulation of the PGC1α promoter. Overall, our data demonstrate a role for Foxa3 in energy expenditure and in age-associated metabolic disorders.

Alterations in hepatic miRNA expression during negative energy balance in postpartum dairy cattle

BACKGROUND

Negative energy balance (NEB), an altered metabolic state, occurs in early postpartum dairy cattle when energy demands to support lactation exceed energy intake. During NEB the liver undergoes oxidative stress and increased breakdown of fatty acids accompanied by changes in gene expression. It is now known that micro RNAs (miRNA) can have a role in mediating such alterations in gene expression through repression or degradation of target mRNAs. miRNA expression is known to be altered by metabolism and environmental factors and miRNAs are implicated in expression modulation of metabolism related genes.

RESULTS

miRNA expression was profiled in the liver of moderate yielding dairy cattle under severe NEB (SNEB) and mild NEB (MNEB) using the Affymetrix Gene Chip miRNA_2.0 array with 679 probe sets for Bos-taurus miRNAs. Ten miRNAs were found to be differentially expressed using the 'samr' statistical package (delta = 0.6) at a q-value FDR of < 12%. Five miRNAs including miR-17-5p, miR-31, miR-140, miR-1281 and miR-2885 were validated using RT-qPCR, to be up-regulated under SNEB. Liver diseases associated with these miRNAs include non-alcoholic fatty liver (NAFLD) and hepatocellular carcinoma (HCC). miR-140 and miR-17-5p are known to show differential expression under oxidative stress. A total of 32 down-regulated putative target genes were also identified among 418 differentially expressed hepatic genes previously reported for the same animal model. Among these, GPR37 (G protein-coupled receptor 37), HEYL (hairy/enhancer-of-split related with YRPW motif-like), DNJA1, CD14 (Cluster of differentiation 14) and GNS (glucosamine (N-acetyl)-6-sulfatase) are known to be associated with hepatic metabolic disorders. In addition miR-140 and miR-2885 have binding sites on the most down-regulated of these genes, FADS2 (Fatty acid desaturase 2) which encodes an enzyme critical in lipid biosynthesis. Furthermore, HNF3-gamma (Hepatocyte nuclear factor 3-gamma), a hepatic transcription factor (TF) that is involved in IGF-1 expression regulation and maintenance of glucose homeostasis is a putative target of miR-31.

CONCLUSIONS

This study shows that SNEB affects liver miRNA expression and these miRNAs have putative targets in hepatic genes down-regulated under this condition. This study highlights the potential role of miRNAs in transcription regulation of hepatic gene expression during SNEB in dairy cattle.

Insight into mechanism of in vitro insulin secretion increase induced by antipsychotic clozapine: role of FOXA1 and mitochondrial citrate carrier

The use of clozapine and other antipsychotic drugs is known to be associated with a number of adverse metabolic side effects, including diabetes mellitus. These side effects could be, at least in part, the result of impaired islet cell function and abnormal insulin secretion, although the underlying mechanisms are unknown. The aim of this study is the identification of targets for clozapine related to the abnormal insulin secretion. We identify a specific activation of the transcriptional factor FOXA1, but not FOXA2 and FOXA3, by clozapine in HepG2 cells. Clozapine enhances FOXA1 DNA-binding and its transcriptional activity, increasing mitochondrial citrate carrier gene expression, which contains a FOXA1 site in its promoter. Haloperidol, a conventional antipsychotic drug, does not determine any increase of FOXA1 gene expression. We also demonstrate that clozapine upregulates FOXA1 and CIC gene expression in INS-1 cells only at basal glucose concentration. In addition, we find that abnormal insulin secretion in basal glucose conditions could be completely abolished by FOXA1 silencing in INS-1 cells treated with clozapine. The identification of FOXA1 as a novel target for clozapine may shed more light to understand molecular mechanism of abnormal insulin secretion during clozapine treatment.

The winged helix transcription factor Foxa3 regulates adipocyte differentiation and depot-selective fat tissue expansion

Conversion of mesenchymal stem cells into terminally differentiated adipocytes progresses sequentially through regulated transcriptional steps. While it is clear that the late phases of adipocyte maturation are governed by the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ), less is known about the transcriptional control of the initial stages of differentiation. To identify early regulators, we performed a small interfering RNA (siRNA) screen of Forkhead-box genes in adipocytes and show here for the first time that the winged helix factor Foxa3 promotes adipocyte differentiation by cooperating with C/EBPβ and -δ to transcriptionally induce PPARγ expression. Furthermore, we demonstrate that mice with genetic ablation of Foxa3 have a selective decrease in epididymal fat depot and a cell-autonomous defect to induce PPARγ specifically in their visceral adipocytes. In obese subjects, FOXA3 is differentially expressed in visceral and subcutaneous adipose depots. Overall, our study implicates Foxa3 in the regulation of adipocyte differentiation and depot-selective adipose tissue expansion.

FoxA family members are crucial regulators of the hypertrophic chondrocyte differentiation program

During endochondral ossification, small, immature chondrocytes enlarge to form hypertrophic chondrocytes, which express collagen X. In this work, we demonstrate that FoxA factors are induced during chondrogenesis, bind to conserved binding sites in the collagen X enhancer, and can promote the expression of a collagen X-luciferase reporter in both chondrocytes and fibroblasts. In addition, we demonstrate by both gain- and loss-of-function analyses that FoxA factors play a crucial role in driving the expression of both endogenous collagen X and other hypertrophic chondrocyte-specific genes. Mice engineered to lack expression of both FoxA2 and FoxA3 in their chondrocytes display defects in chondrocyte hypertrophy, alkaline phosphatase expression, and mineralization in their sternebrae and, in addition, exhibit postnatal dwarfism that is coupled to significantly decreased expression of both collagen X and MMP13 in their growth plates. Our findings indicate that FoxA family members are crucial regulators of the hypertrophic chondrocyte differentiation program.

Foxa1 and Foxa2 are essential for sexual dimorphism in liver cancer

Hepatocellular carcinoma (HCC) is sexually dimorphic in both rodents and humans, with significantly higher incidence in males, an effect that is dependent on sex hormones. The molecular mechanisms by which estrogens prevent and androgens promote liver cancer remain unclear. Here, we discover that sexually dimorphic HCC is completely reversed in Foxa1- and Foxa2-deficient mice after diethylnitrosamine-induced hepatocarcinogenesis. Coregulation of target genes by Foxa1/a2 and either the estrogen receptor (ERα) or the androgen receptor (AR) was increased during hepatocarcinogenesis in normal female or male mice, respectively, but was lost in Foxa1/2-deficient mice. Thus, both estrogen-dependent resistance to and androgen-mediated facilitation of HCC depend on Foxa1/2. Strikingly, single nucleotide polymorphisms at FOXA2 binding sites reduce binding of both FOXA2 and ERα to their targets in human liver and correlate with HCC development in women. Thus, Foxa factors and their targets are central for the sexual dimorphism of HCC.

FOXA1: a transcription factor with parallel functions in development and cancer

When aberrant, factors critical for organ morphogenesis are also commonly involved in disease progression. FOXA1 (forkhead box A1), also known as HNF3α (hepatocyte nuclear factor 3α), is required for postnatal survival due to its essential role in controlling pancreatic and renal function. In addition to regulating a variety of tissues during embryogenesis and early life, rescue experiments have revealed a specific role for FOXA1 in the postnatal development of the mammary gland and prostate. Activity of the nuclear hormone receptors ERα (oestrogen receptor α) and AR (androgen receptor) is also required for proper development of the mammary gland and prostate respectively. FOXA1 modulates ER and AR function in breast and prostate cancer cells, supporting the postulate that FOXA1 is involved in ER and AR signalling under normal conditions, and that some carcinogenic processes in these tissues stem from hormonally regulated developmental pathways gone awry. In addition to broadly reviewing the function of FOXA1 in various aspects of development and cancer, this review focuses on the interplay of FOXA1/ER and FOXA1/AR, in normal and cancerous mammary and prostate epithelial cells. Given the hormone dependency of both breast and prostate cancer, a thorough understanding of FOXA1's role in both cancer types is critical for battling hormone receptor-positive disease and acquired anti-hormone resistance.

Foxa1 reduces lipid accumulation in human hepatocytes and is down-regulated in nonalcoholic fatty liver

Triglyceride accumulation in nonalcoholic fatty liver (NAFL) results from unbalanced lipid metabolism which, in the liver, is controlled by several transcription factors. The Foxa subfamily of winged helix/forkhead box (Fox) transcription factors comprises three members which play important roles in controlling both metabolism and homeostasis through the regulation of multiple target genes in the liver, pancreas and adipose tissue. In the mouse liver, Foxa2 is repressed by insulin and mediates fasting responses. Unlike Foxa2 however, the role of Foxa1 in the liver has not yet been investigated in detail. In this study, we evaluate the role of Foxa1 in two human liver cell models, primary cultured hepatocytes and HepG2 cells, by adenoviral infection. Moreover, human and rat livers were analyzed to determine Foxa1 regulation in NAFL. Results demonstrate that Foxa1 is a potent inhibitor of hepatic triglyceride synthesis, accumulation and secretion by repressing the expression of multiple target genes of these pathways (e.g., GPAM, DGAT2, MTP, APOB). Moreover, Foxa1 represses the fatty acid transporter protein FATP2 and lowers fatty acid uptake. Foxa1 also increases the breakdown of fatty acids by inducing peroxisomal fatty acid β-oxidation and ketone body synthesis. Finally, Foxa1 is able to largely up-regulate UCP1, thereby dissipating energy and consistently decreasing the mitochondria membrane potential. We also report that human and rat NAFL have a reduced Foxa1 expression, possibly through a protein kinase C-dependent pathway. We conclude that Foxa1 is an antisteatotic factor that coordinately tunes several lipid metabolic pathways to block triglyceride accumulation in hepatocytes. However, Foxa1 is down-regulated in human and rat NAFL and, therefore, increasing Foxa1 levels could protect from steatosis. Altogether, we suggest that Foxa1 could be a novel therapeutic target for NAFL disease and insulin resistance.

Deletion of interleukin-6 improves pyruvate tolerance without altering hepatic insulin signaling in the leptin receptor-deficient mouse

Obesity is associated with increased circulating interleukin-6 (IL-6), which may contribute to hepatic insulin resistance by impairing insulin receptor signaling. This study was designed to assess the impact of the systemic absence of IL-6 on the development of insulin resistance and glucose intolerance in an obese mouse model. Systemic insulin, glucose, and pyruvate tolerance tests were performed in IL-6 knockout (IL6KO) mice that had been crossed with a genetically obese (leptin receptor-deficient mouse model [Lep(db)]) mouse model. Real-time reverse transcriptase polymerase chain reaction and Western blot analysis assessed cellular and molecular markers of insulin signaling, inflammation, and metabolism. Absence of IL-6 did not improve systemic glucose or insulin tolerance, but Lep(db) × IL6KO mice displayed a smaller blood glucose increase following a pyruvate challenge. These results suggest that loss of IL-6 in the context of obesity may locally reduce hepatic glucose production from a gluconeogenic precursor. Hepatic insulin-dependent insulin receptor autophosphorylation, Akt activation, and FoxO1 phosphorylation were similar between Lep(db) × IL6KO mice and Lep(db) controls. Basal gene expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase was reduced in male Lep(db) × IL6KO mice relative to Lep(db) controls; but gene expression of another regulatory enzyme, glucose-6-phosphatase, remained unaltered. Absence of IL-6 reduced gene expression of serum amyloid A and RelA in female Lep(db) mice, but did not alter hepatic triglyceride accumulation or lipogenic gene expression. Overall, our results suggest that IL-6 may be detrimental in obesity by contributing to elevated hepatic glucose output.

The nucleosome map of the mammalian liver

Binding to nucleosomal DNA is critical for 'pioneer' transcription factors such as the winged-helix transcription factors Foxa1 and Foxa2 to regulate chromatin structure and gene activation. Here we report the genome-wide map of nucleosome positions in the mouse liver, with emphasis on transcriptional start sites, CpG islands, Foxa2 binding sites and their correlation with gene expression. Despite the heterogeneity of liver tissue, we could clearly discern the nucleosome pattern of the predominant liver cell, the hepatocyte. By analyzing nucleosome occupancy and the distributions of heterochromatin protein 1 (Hp1), CBP (also known as Crebbp) and p300 (Ep300) in Foxa1- and Foxa2-deficient livers, we find that the maintenance of nucleosome position and chromatin structure surrounding Foxa2 binding sites is independent of Foxa1 and Foxa2.