FHL2, a novel tissue-specific coactivator of the androgen receptor

Unlocking the secrets of Cardiac development and function: the critical role of FHL2

FHL2 (Four-and-a-half LIM domain protein 2) is a crucial factor involved in cardiac morphogenesis, the process by which the heart develops its complex structure. It is expressed in various tissues during embryonic development, including the developing heart, and has been shown to play important roles in cell proliferation, differentiation, and migration. FHL2 interacts with multiple proteins to regulate cardiac development as a coactivator or a corepressor. It is involved in cardiac specification and determination of cell fate, cardiomyocyte growth, cardiac remodeling, myofibrillogenesis, and the regulation of HERG channels. Targeting FHL2 has therapeutic implications as it could improve cardiac function, control arrhythmias, alleviate heart failure, and maintain cardiac integrity in various pathological conditions. The identification of FHL2 as a signature gene in atrial fibrillation suggests its potential as a diagnostic marker and therapeutic target for this common arrhythmia.

The cyclin-dependent kinase inhibitor AT7519 is a human RORγt agonist

AT7519, which inhibits multiple cyclin-dependent kinases, has been extensively investigated in various types of cancer cells. Previous studies have demonstrated the ability of this molecule to suppress the expression of the nuclear receptor retinoic acid-related orphan receptor gamma (RORγ) and several genes involved in hepatocellular carcinoma progression. In this study, we identified a distinct agonistic effect of AT7519 on RORγt, an isoform expressed by various immune cells, including T helper 17 lymphocytes. These immune cells play pivotal roles in shaping the tumor microenvironment and promoting the anticancer response of the immune system. After exposure to AT7519 during differentiation, primary human CD4+ T cells presented increased expression of IL17A/F, IFNG and GZMB and decreased expression of PDCD1 and CTLA4. These findings elucidate a previously unrecognized facet of AT7519 activity and suggest the potential incorporation of this molecule into immune therapies to augment the effectiveness of diverse anticancer strategies involving anti-programmed cell death protein 1 (anti-PD-1) and anti-cytotoxic T-lymphocyte antigen 4 (anti-CTLA4) regimens.

Unraveling the role of the FHL family in cardiac diseases: Mechanisms, implications, and future directions

Heart diseases are a major cause of morbidity and mortality worldwide. Understanding the molecular mechanisms underlying these diseases is essential for the development of effective diagnostic and therapeutic strategies. The FHL family consists of five members: FHL1, FHL2, FHL3, FHL4, and FHL5/Act. These members exhibit different expression patterns in various tissues including the heart. FHL family proteins are implicated in cardiac remodeling, regulation of metabolic enzymes, and cardiac biomechanical stress perception. A large number of studies have explored the link between FHL family proteins and cardiac disease, skeletal muscle disease, and ovarian metabolism, but a comprehensive and in-depth understanding of the specific molecular mechanisms targeting FHL on cardiac disease is lacking. The aim of this review is to explore the structure and function of FHL family members, to comprehensively elucidate the mechanisms by which they regulate the heart, and to explore in depth the changes in FHL family members observed in different cardiac disorders, as well as the effects of mutations in FHL proteins on heart health.

Downregulation of FHL2 suppressed trophoblast migration, invasion and epithelial-mesenchymal transition in recurrent miscarriage

RESEARCH QUESTION

Is four and a half LIM domain 2 (FHL2) involved in trophoblast migration, invasion and epithelial-mesenchymal transition (EMT) in recurrent miscarriage?

DESIGN

Villus tissue was collected from 24 patients who had experienced recurrent miscarriage and 24 healthy controls. FHL2 mRNA and protein expression in villus specimens were observed by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. Small interfering RNA and overexpression plasmid were used to change the FHL2 expression. JAR and HTR8/SVneo cell lines were used to conduct scratch-wound assay and transwell assay to detect trophoblast migration and invasion of FHL2. Downstream molecule expression of mRNA and protein and EMT markers were verified by qRT-PCR and Western blot.

RESULTS

Significantly lower FHL2 mRNA (P = 0.019) and protein (P = 0.0014) expression was found in trophoblasts from the recurrent miscarriage group compared with healthy controls. FHL2 knockdown repressed migration (P = 0.0046), invasion (P < 0.001) and EMT, as shown by significant differences in mRNA and protein expression of the EMT markers N-cadherin, E-cadherin, Vimentin and Snail (all P < 0.05) of extravillus trophoblasts. FHL2 overexpression enhanced migration (P = 0.025), invasion (P < 0.001) and EMT of extravillus trophoblasts (all EMT markers P < 0.05). The positive upstream factor FHL2 in the extracellular signal-related kinase pathway induced JunD expression, thereby promoting trophoblast migration and invasion via matrix metalloproteinase 2.

CONCLUSIONS

FHL2 is involved in a regulatory pathway of trophoblast migration, invasion and EMT during early pregnancy, and may have a role in recurrent miscarriage pathogenesis, which can serve as a possible target for novel therapeutic development.

FHL2 Inhibits SARS-CoV-2 Replication by Enhancing IFN-β Expression through Regulating IRF-3

SARS-CoV-2 triggered the global COVID-19 pandemic, posing a severe threat to public health worldwide. The innate immune response in cells infected by SARS-CoV-2 is primarily orchestrated by type I interferon (IFN), with IFN-β exhibiting a notable inhibitory impact on SARS-CoV-2 replication. FHL2, acting as a docking site, facilitates the assembly of multiprotein complexes and regulates the transcription of diverse genes. However, the association between SARS-CoV-2 and FHL2 remains unclear. In this study, we report for the first time that SARS-CoV-2 infection in Caco2 cells results in the upregulation of FHL2 expression, while the virus's N proteins can enhance FHL2 expression. Notably, the knockdown of FHL2 significantly amplifies SARS-CoV-2 replication in vitro. Conversely, the overexpression of FHL2 leads to a marked reduction in SARS-CoV-2 replication, with the antiviral property of FHL2 being independent of the cell or virus type. Subsequent experiments reveal that FHL2 supports IFN-β transcription by upregulating the expression and phosphorylation of IRF-3, thereby impeding SARS-CoV-2 replication in cells. These findings highlight FHL2 as a potential antiviral target for treating SARS-CoV-2 infections.

Transcription factor E4F1 as a regulator of cell life and disease progression

E4F transcription factor 1 (E4F1), a member of the GLI-Kruppel family of zinc finger proteins, is now widely recognized as a transcription factor. It plays a critical role in regulating various cell processes, including cell growth, proliferation, differentiation, apoptosis and necrosis, DNA damage response, and cell metabolism. These processes involve intricate molecular regulatory networks, making E4F1 an important mediator in cell biology. Moreover, E4F1 has also been implicated in the pathogenesis of a range of human diseases. In this review, we provide an overview of the major advances in E4F1 research, from its first report to the present, including studies on its protein domains, molecular mechanisms of transcriptional regulation and biological functions, and implications for human diseases. We also address unresolved questions and potential research directions in this field. This review provides insights into the essential roles of E4F1 in human health and disease and may pave the way for facilitating E4F1 from basic research to clinical applications.

Biased regulation of glucocorticoid receptors signaling

Glucocorticoids (GCs), steroid hormones that depend on glucocorticoid receptor (GR) binding for their action, are essential for regulating numerous homeostatic functions in the body.GR signals are biased, that is, GR signals are various in different tissue cells, disease states and ligands. This biased regulation of GR signaling appears to depend on ligand-induced metameric regulation, protein post-translational modifications, assembly at response elements, context-specific assembly (recruitment of co-regulators) and intercellular differences. Based on the bias regulation of GR, selective GR agonists and modulators (SEGRAMs) were developed to bias therapeutic outcomes toward expected outcomes (e.g., anti-inflammation and immunoregulation) by influencing GR-mediated gene expression. This paper provides a review of the bias regulation and mechanism of GR and the research progress of drugs.

Silencing FHL2 inhibits bleomycin-induced pulmonary fibrosis through the TGF-β1/Smad signaling pathway

OBJECTIVE

This study aimed to investigate the inhibiting effects of FHL2 and Arbutin on cell fibrosis and their possible mechanisms.

METHODS

The mRNA expression of FHL2 in pulmonary fibrosis tissues was analyzed by bioinformatics. TGF⁃β1 induced fibrosis of mouse lung fibroblast (Mlg) and mouse primary pulmonary fibroblast (PPF) in rat's lung fibroblasts. FHL2 siRNA was transfected into Mlg and mouse PPF cells to inhibit FHL2. FHL2, α-smooth muscle actin (α-SMA), collagen 1 (Col I), and Fibronectin (Fn) were detected by qRT-PCR. Western blot expression levels of Smad3, p-Smad3, Smad2, and p-Smad2 proteins in cells. High-throughput drug screening for FHL2 inhibitors and the inhibitory effect of Arbutin on pulmonary fibrosis were validated in cellular and animal models of pulmonary fibrosis.

RESULTS

The mRNA expression of FHL2 in lung fiber tissue was increased. Meanwhile, the decrease of FHL2 expression significantly inhibited the cellular fibrosis morphological changes of rat's lung fibroblasts (Mlgs) and primary lung fibroblasts (PPFs). The expression levels of α⁃SMA, Col I, and Fn were decreased. High-throughput screening showed that Arbutin targeted FHL2. Arbutin alleviated bleomycin (BLM)-induced pulmonary fibrosis in rats by inhibiting FHL2 and then the TGF-β1/Smad signaling pathway.

CONCLUSION

Inhibition of FHL2 can effectively reduce the fibrosis process induced by TGF⁃β1 and bleomycin, and then inhibit the fibrosis.

DNA methylation-based age prediction with bloodstains using pyrosequencing and random forest regression

The use of DNA methylation to predict chronological age has shown promising potential for obtaining additional information in forensic investigations. To date, several studies have reported age prediction models based on DNA methylation in body fluids with high DNA content. However, it is often difficult to apply these existing methods in practice due to the low amount of DNA present in stains of body fluids that are part of a trace material. In this study, we present a sensitive and rapid test for age prediction with bloodstains based on pyrosequencing and random forest regression. This assay requires only 0.1 ng of genomic DNA and the entire procedure can be completed within 10 h, making it practical for forensic investigations that require a short turnaround time. We examined the methylation levels of 46 CpG sites from six genes using bloodstain samples from 128 males and 113 females aged 10-79 years. A random forest regression model was then used to construct an age prediction model for males and females separately. The final age prediction models were developed with seven CpG sites (three for males and four for females) based on the performance of the random forest regression. The mean absolute deviation was less than 3 years for each model. Our results demonstrate that DNA methylation-based age prediction using pyrosequencing and random forest regression has potential applications in forensics to accurately predict the biological age of a bloodstain donor.

Energy Trade-Off and Four Extreme Human Body Types

BACKGROUND

Resource trade-off theory suggests that increased performance on a given trait comes at the cost of decreased performance on other traits.

METHODS

Growth data from 1889 subjects (996 girls) were used from the GrowUp1974 Gothenburg study. Energy Trade-Off (ETO) between height and weight for individuals with extreme body types was characterized using a novel ETO-Score (ETOS). Four extreme body types were defined based on height and ETOI at early adulthood: tall-slender, short-stout, short-slender, and tall-stout; their growth trajectories assessed from ages 0.5-17.5 years.A GWAS using UK BioBank data was conducted to identify gene variants associated with height, BMI, and for the first time with ETOS.

RESULTS

Height and ETOS trajectories show a two-hit pattern with profound changes during early infancy and at puberty for tall-slender and short-stout body types.Several loci (including FTO, ADCY3, GDF5, ) and pathways were identified by GWAS as being highly associated with ETOS. The most strongly associated pathways were related to 'extracellular matrix', 'signal transduction', 'chromatin organization', and 'energy metabolism'.

CONCLUSIONS

ETOS represents a novel anthropometric trait with utility in describing body types. We discovered the multiple genomic loci and pathways probably involved in energy trade-off.

Glucose-mediated insulin secretion is improved in FHL2-deficient mice and elevated FHL2 expression in humans is associated with type 2 diabetes

AIMS/HYPOTHESIS

The general population is ageing, involving an enhanced incidence of chronic diseases such as type 2 diabetes. With ageing, DNA methylation of FHL2 increases, as well as expression of the four and a half LIM domains 2 (FHL2) protein in human pancreatic islets. We hypothesised that FHL2 is actively involved in glucose metabolism.

METHODS

Publicly available microarray datasets from human pancreatic islets were analysed for FHL2 expression. In FHL2-deficient mice, we studied glucose clearance and insulin secretion. Gene expression analysis and glucose-stimulated insulin secretion (GSIS) were determined in isolated murine FHL2-deficient islets to evaluate insulin-secretory capacity. Moreover, knockdown and overexpression of FHL2 were accomplished in MIN6 cells to delineate the underlying mechanism of FHL2 function.

RESULTS

Transcriptomics of human pancreatic islets revealed that individuals with elevated levels of HbA_1c displayed increased FHL2 expression, which correlated negatively with insulin secretion pathways. In line with this observation, FHL2-deficient mice cleared glucose more efficiently than wild-type littermates through increased plasma insulin levels. Insulin sensitivity was comparable between these genotypes. Interestingly, pancreatic islets isolated from FHL2-deficient mice secreted more insulin in GSIS assays than wild-type mouse islets even though insulin content and islet size was similar. To support this observation, we demonstrated increased expression of the transcription factor crucial in insulin secretion, MAF BZIP transcription factor A (MafA), higher expression of GLUT2 and reduced expression of the adverse factor c-Jun in FHL2-deficient islets. The underlying mechanism of FHL2 was further delineated in MIN6 cells. FHL2-knockdown led to enhanced activation of forkhead box protein O1 (FOXO1) and its downstream genes such as Mafa and Pdx1 (encoding pancreatic and duodenal homeobox 1), as well as increased glucose uptake. On the other hand, FHL2 overexpression in MIN6 cells blocked GSIS, increased the formation of reactive oxygen species and increased c-Jun activity.

CONCLUSIONS/INTERPRETATION

Our data demonstrate that FHL2 deficiency improves insulin secretion from beta cells and improves glucose tolerance in mice. Given that FHL2 expression in humans increases with age and that high expression levels of FHL2 are associated with beta cell dysfunction, we propose that enhanced FHL2 expression in elderly individuals contributes to glucose intolerance and the development of type 2 diabetes.

DATA AVAILABILITY

The human islet microarray datasets used are publicly available and can be found on https://www.ncbi.nlm.nih.gov/geo/ .

Integrated analysis of the miRNA and mRNA expression profiles in Leiocassis longirostris at gonadal maturation

Leiocassis longirostris is a commercially important fish species that shows a sexually dimorphic growth pattern. A lack of molecular data from the gonads of this species has hindered research and selective breeding efforts. In this study, we conducted a comprehensive analysis of the expression profile of miRNA and mRNA to explore their regulatory roles in the gonadal maturation stage of L. longirostris. We identified 60 differentially expressed miRNAs and 20,752 differentially expressed genes by sequencing. A total of 90 miRNAs and 21 target genes involved in gonad development and sex determination were identified. Overall, the results of this study enhance our understanding of the molecular mechanisms underlying sex determination and differentiation and provide valuable genomic information for the selective breeding of L. longirostris.

Analyzing the Androgen Receptor Interactome in Prostate Cancer: Implications for Therapeutic Intervention

The androgen receptor (AR) is a member of the ligand-activated nuclear receptor family of transcription factors. AR's transactivation activity is turned on by the binding of androgens, the male sex steroid hormones. AR is critical for the development and maintenance of the male phenotype but has been recognized to also play an important role in human diseases. Most notably, AR is a major driver of prostate cancer (CaP) progression, which remains the second leading cause of cancer deaths in American men. Androgen deprivation therapies (ADTs) that interfere with interactions between AR and its activating androgen ligands have been the mainstay for treatment of metastatic CaP. Although ADTs are effective and induce remissions, eventually they fail, while the growth of the majority of ADT-resistant CaPs remains under AR's control. Alternative approaches to inhibit AR activity and bypass resistance to ADT are being sought, such as preventing the interaction between AR and its cofactors and coregulators that is needed to execute AR-dependent transcription. For such strategies to be efficient, the 3D conformation of AR complexes needs to be well-understood and AR-regulator interaction sites resolved. Here, we review current insights into these 3D structures and the protein interaction sites in AR transcriptional complexes. We focus on methods and technological approaches used to identify AR interactors and discuss challenges and limitations that need to be overcome for efficient therapeutic AR complex disruption.

sPmel17 Secreted by Ultraviolet B-Exposed Melanocytes Alters the Intercellular Adhesion of Keratinocytes

Repigmentation of the skin in patients with vitiligo represents an intricate process in which the depigmented epidermis is replenished by functional melanocytes (MCs) that migrate from undamaged hair follicles and/or surrounding areas. We characterized whether MCs release a secreted form of Pmel17 (sPmel17) protein after exposure to UVB, thereby weakening the cell-cell adhesions of keratinocytes (KCs), which provides MCs the opportunity to migrate to areas devoid of MCs. At first, we examined the interactions of sPmel17 and FHL2 (four-and-a-half LIM domain protein 2) in KCs treated with the conditioned media (CM) from MCs exposed to UVB. The results showed that both the protein and mRNA levels of FHL2 were significantly upregulated in KCs treated with sPmel17-enriched CM from UVB-exposed MCs. We also found that there are physical interactions between sPmel17 and FHL2 as analyzed by reciprocal coimmunoprecipitation assays and double immunofluorescence staining. The CM from UVB-exposed MCs signaled KCs to remodel the actin cytoskeleton and reduce E-cadherin expression. However, the CM from UVB-exposed and Pmel17-silenced or from UVB-unexposed MCs failed to do this. To further determine the in situ distributions of sPmel17, FHL2, and E-cadherin, we examined the expression profiles of those proteins in the skin from healthy subjects and from depigmented or repigmented vitiligo using immunofluorescence and immunohistochemical staining. The results showed that the expression of sPmel17 was positively correlated with FHL2 but not to E-cadherin. The colocalization of FHL2 and sPmel17 was also observed in UVB-exposed mouse tail skin. Together, the upregulation of FHL2 in KCs requires stimulation by sPmel17 secreted from MCs and activation of the sPmel17-FHL2-E-cadherin axis offers a potential therapeutic target to expedite the repigmentation process in patients with vitiligo.

Decoding Cinnabarinic Acid-Specific Stanniocalcin 2 Induction by Aryl Hydrocarbon Receptor

Aryl hydrocarbon receptor (AhR) is a ligand-mediated transcription factor known for regulating response to xenobiotics, including prototypical 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) through the activation of CYP1A1 expression. Upon ligand-binding, AhR translocates to the nucleus, interacts with the AhR nuclear translocator, and binds to xenobiotic response elements (XREs; GCGTG) present in the promoter region of AhR-regulated genes. Recently, we identified a novel tryptophan catabolite, cinnabarinic acid (CA), as an endogenous AhR agonist capable of activating expression of AhR target gene stanniocalcin 2 (stc2). The CA-driven stc2 induction bestowed cytoprotection against hepatotoxicity in an AhR-dependent manner. Interestingly, only CA but not TCDD was able to induce stc2 expression in liver, and CA was unable to upregulate the TCDD responsive cyp1a1 gene. In this report, we identified CA-specific histone H4 lysine 5 acetylation and H3 lysine 79 methylation at the AhR-bound stc2 promoter. Moreover, histone H4 lysine 5 acetylation writer, activating transcription factor 2 (Atf2), and H3 lysine 79 methylation writer, disruptor of telomeric silencing 1-like histone lysine methyltransferase (Dot1l), were interacting with the AhR complex at the stc2 promoter exclusively in response to CA treatment concurrent with the histone epigenetic marks. Suppressing Atf2 and Dot1l expression using RNA interference confirmed their role in stc2 expression. CRISPR/Cas9-assisted replacement of cyp1a1 promoter-encompassing XREs with stc2 promoter XREs resulted in CA-dependent induction of cyp1a1, underlining a fundamental role of quaternary structure of XRE sequence in agonist-specific gene regulation. In conclusion, CA-driven recruitment of specific chromatin regulators to the AhR complex and resulting histone epigenetic modifications may serve as a molecular basis for agonist-specific stc2 regulation by AhR. SIGNIFICANCE STATEMENT: Results reported here provide a mechanistic explanation for the agonist-specific differential gene regulation by identifying interaction of aryl hydrogen receptor with specific chromatin regulators concomitant with unique histone epigenetic marks. This study also demonstrated that the agonist-specific target-gene expression can be transferred with the gene-specific promoter xenobiotic response element-sequence in the context of chromatin architecture.

The titin N2B and N2A regions: biomechanical and metabolic signaling hubs in cross-striated muscles

Muscle specific signaling has been shown to originate from myofilaments and their associated cellular structures, including the sarcomeres, costameres or the cardiac intercalated disc. Two signaling hubs that play important biomechanical roles for cardiac and/or skeletal muscle physiology are the N2B and N2A regions in the giant protein titin. Prominent proteins associated with these regions in titin are chaperones Hsp90 and αB-crystallin, members of the four-and-a-half LIM (FHL) and muscle ankyrin repeat protein (Ankrd) families, as well as thin filament-associated proteins, such as myopalladin. This review highlights biological roles and properties of the titin N2B and N2A regions in health and disease. Special emphasis is placed on functions of Ankrd and FHL proteins as mechanosensors that modulate muscle-specific signaling and muscle growth. This region of the sarcomere also emerged as a hotspot for the modulation of passive muscle mechanics through altered titin phosphorylation and splicing, as well as tethering mechanisms that link titin to the thin filament system.

Screening and identification of a novel FHL2 mutation by whole exome sequencing in twins with familial Waldenström macroglobulinemia

BACKGROUND

Waldenström macroglobulinemia (WM) is a rare chronic B-cell lymphoma. Familial clustering of WM has been observed over the years. However, little is known about the contribution of inherited genetic variants to familial WM cases.

METHODS

The authors performed whole exome sequencing (WES) of germline DNA samples from twins, one diagnosed with WM and the other diagnosed with immunoglobulin M monoclonal gammopathy of undetermined significance, and their healthy siblings. Bioinformatics analysis of public biological databases was used to identify the most relevant familial WM candidate from WES. Transcript expression and protein levels of the familial WM candidate were evaluated in the WM patient and 2 unaffected members of the kindred.

RESULTS

Among the 10 shared candidate mutations in the twins, the authors identified a novel heterozygous germline mutation in four and a half LIM domains protein 2 (FHL2; c.G226A, p.V76M) as a familial WM-associated mutation. FHL2 appeared to be connected with reported signaling pathways and disease-driving genes such as IL6 and HCK in WM. In addition, the authors found reduced FHL2 messenger RNA and protein expression in peripheral blood samples from the patient with WM in comparison with the healthy siblings.

CONCLUSIONS

Taken together, these findings indicate that an FHL2^g226a mutation may play an important role in familial WM, and they provide new screening possibilities for familial cases.

LAY SUMMARY

Familial clustering in Waldenström macroglobulinemia (WM) has been observed over the years. The authors performed whole exome sequencing of germline DNA samples from twins, one diagnosed with WM and the other diagnosed with immunoglobulin M monoclonal gammopathy of undetermined significance, and their healthy siblings. Among the 10 shared candidate mutations in the twins, a novel heterozygous germline mutation in four and a half LIM domains protein 2 (FHL2; c.G226A, p.V76M) was identified as the most relevant familial WM candidate through bioinformatics analysis of a public database. Also, messenger RNA and protein expression of FHL2 was significantly lower in peripheral blood mononuclear cells of the WM patient in comparison with the healthy siblings, and this suggested that the function of FHL2 was impaired when mutated.

Functional Versatility of the CDK Inhibitor p57Kip2

The cyclin/CDK inhibitor p57^Kip2 belongs to the Cip/Kip family, with p21^Cip1 and p27^Kip1, and is the least studied member of the family. Unlike the other family members, p57^Kip2 has a unique role during embryogenesis and is the only CDK inhibitor required for embryonic development. p57^Kip2 is encoded by the imprinted gene CDKN1C, which is the gene most frequently silenced or mutated in the genetic disorder Beckwith-Wiedemann syndrome (BWS), characterized by multiple developmental anomalies. Although initially identified as a cell cycle inhibitor based on its homology to other Cip/Kip family proteins, multiple novel functions have been ascribed to p57^Kip2 in recent years that participate in the control of various cellular processes, including apoptosis, migration and transcription. Here, we will review our current knowledge on p57^Kip2 structure, regulation, and its diverse functions during development and homeostasis, as well as its potential implication in the development of various pathologies, including cancer.

LncRNA DLX6-AS1 aggravates the development of ovarian cancer via modulating FHL2 by sponging miR-195-5p

Background

Ovarian cancer (OC) is a huge burden on women’s lives. Recently, the implication of long non-coding RNAs (lncRNAs) in cancers, including OC, has aroused much attention. The objective of this study was to explore the role and functional mechanism of lncRNA distal-less homeobox 6 antisense 1 (DLX6-AS1) in OC.

Methods

The expression of DLX6-AS1, miR-195-5p, and four and a half LIM domains protein 2 (FHL2) was measured by quantitative real-time polymerase chain reaction (qRT-PCR). The cell proliferation, apoptosis, migration, and invasion were assessed by cell count kit 8 (CCK-8), flow cytometry and transwell assays, respectively. The protein levels of proliferating cell nuclear antigen (PCNA), cleaved-caspase-3 (C-caspase 3), N-cadherin, Vimentin, E-cadherin and FHL2 were quantified by western blot. The relationship between miR-195-5p and DLX6-AS1 or FHL2 was predicted by bioinformatics tool starBase and verified by luciferase reporter assay and RNA immunoprecipitation (RIP) assay. Xenograft tumor model was established to observe the role of DLX6-AS1 in vivo.

Results

DLX6-AS1 and FHL2 were up-regulated in OC tissues and cells, while miR-195-5p was down-regulated. DLX6-AS1 knockdown inhibited proliferation, migration, and invasion but induced apoptosis of OC cells. However, miR-195-5p inhibition reversed these effects. Overexpression of miR-195-5p also depleted proliferation, migration, and invasion but promoted apoptosis of OC cells, while FHL2 overexpression overturned these influences. DLX6-AS1 knockdown blocked tumor growth in vivo.

Conclusion

DLX6-AS1, as an oncogene in OC, accelerated tumor progression by up-regulating FHL2 via mediating miR-195-5p, suggesting that DLX6-AS1 was a hopeful target for the lncRNA-targeted therapy in OC.

Recapitulation of prostate tissue cell type-specific transcriptomes by an in vivo primary prostate tissue xenograft model

Studies of the normal functions and diseases of the prostate request in vivo models that maintain the tissue architecture and the multiple-cell type compartments of human origin in order to recapitulate reliably the interactions of different cell types. Cell type-specific transcriptomes are critical to reveal the roles of each cell type in the functions and diseases of the prostate. A primary prostate tissue xenograft model was developed using fresh human prostate tissue specimens transplanted onto male mice that were castrated surgically and implanted with a device to maintain circulating testosterone levels comparable to adult human males. Endothelial cells and epithelial cells were isolated from 7 fresh human prostate tissue specimens and from primary tissue xenografts established from 9 fresh human prostate tissue specimens, using antibody-conjugated magnetic beads specific to human CD31 and human EpCAM, respectively. Transcriptomes of endothelial, epithelial and stromal cell fractions were obtained using RNA-Seq. Global and function-specific gene expression profiles were compared in inter-cell type and inter-tissue type manners. Gene expression profiles in the individual cell types isolated from xenografts were similar to those of cells isolated from fresh tissue, demonstrating the value of the primary tissue xenograft model for studies of the inter-relationships between prostatic cell types and the role of such inter-relationships in organ development, disease progression, and response to drug treatments.

The CDK inhibitor p57Kip2 enhances the activity of the transcriptional coactivator FHL2

The eukaryotic cell cycle is negatively regulated by cyclin-dependent kinase inhibitors (CKIs). p57^Kip2 is a member of the Cip/Kip family of CKIs and frequently inactivated by genomic mutations associated with human overgrowth disorders. There is increasing evidence for p57 to control cellular processes in addition to cell cycle and CDK regulation including transcription, apoptosis, migration or development. In order to obtain molecular insights to unknown functions of p57, we performed a protein interaction screen. We identified the transcription regulator four-and-a-half LIM-only protein 2 (FHL2) as a novel p57-binding protein. Co-immunoprecipitation and reporter gene assays were used to elucidate the physiological and functional relevance of p57/FHL2 interaction. We found in cancer cells that endogenous p57 and FHL2 are in a complex. We observed a substantial induction of established FHL2-regulated gene promoters by p57 in reporter gene experiments and detected strong induction of the intrinsic transactivation activity of FHL2. Treatment of cells with histone deacetylase (HDAC) inhibitors and binding of exogenous FHL2 to HDACs indicated repression of FHL2 transcription activity by HDACs. In the presence of the HDAC inhibitor sodium butyrate activation of FHL2 by p57 is abrogated suggesting that p57 shares a common pathway with HDAC inhibitors. p57 competes with HDACs for FHL2 binding which might partly explain the mechanism of FHL2 activation by p57. These results suggest a novel function of p57 in transcription regulation.

Expression, location and biological effects of four and a half LIM domain protein 2 (FHL2) on granulosa cells in ovine

Previous studies have shown that four and a half LIM domain protein 2 (FHL2) plays an essential role in the regulation of follicular development in mammals. Although the FHL2 genes of human and mouse have been well characterized, the expression and location of FHL2 in ovary and the biological functions of FHL2 on granulosa cells (GCs) of ovine are still not clear. In this study, full-length complementary DNA (cDNA) of FHL2 from ovine follicular GCs was amplified by real-time PCR (RT-PCR). The expression and location of FHL2 in ovary and GCs of ovine were studied by immunohistochemistry and immunofluorescence, and the biological effects of FHL2 on the cell proliferation, cell apoptosis, cell cycles and expression level of related genes of ovine GCs were also explored by overexpression or knockdown of FHL2. The results indicated that FHL2 was expressed in ovine follicular GCs and the sequence of the FHL2 cDNA was consistent with that predicted in GenBank, which did not cause an amino acid change. According to the results, FHL2 was expressed in ovine ovary and mainly located in the cytoplasm and nucleus of GCs. In addition, overexpression of FHL2 significantly reduced the cell viability, promoted the cell apoptosis and decreased the percentage of G0/G1 and S phase cells. RT-PCR showed that overexpression of FHL2 significantly increased the mRNA expression level of Bax and decreased the expression of Bcl-2 and the Bcl-2/Bax mRNA ratio compared with the control group. Besides, the knockdown of FHL2 gene in ovine GCs significantly improved the cell viability, suppressed the cell apoptosis, decreased the mRNA expression level of Caspase-3 gene, increased the Bcl-2/Bax mRNA ratio and increased the percentage of S and G2/M phase cells. Our results suggest that FHL2 may play an important role in the biological functions of GCs in ovine.

Up-regulated FHL2 inhibits ovulation through interacting with androgen receptor and ERK1/2 in polycystic ovary syndrome

BACKGROUND

The ovulatory dysfunction mechanisms underlying polycystic ovary syndrome (PCOS) are not completely understood. There is no effective therapy for PCOS so far.

METHODS

We measured the expression of four and a half LIM domain 2 (FHL2) and other related-genes in human granulosa cells (hGCs) from patients with and without PCOS. To minimise the heterogeneity of patients with PCOS, we only included PCOS patients meeting all three criteria according to the revised Rotterdam consensus. The in vitro effects of FHL2 on ovulatory genes and the underlying mechanisms were examined in KGN cells. The role of FHL2 in ovulation was investigated in vivo by overexpressing FHL2 in rat ovaries via intrabursal lentivirus injection.

FINDINGS

Increased FHL2 and androgen receptor (AR) expression and decreased CCAAT/enhancer-binding protein β (C/EBPβ) expression were observed in hGCs from patients with PCOS. FHL2 inhibited the expression of ovulation-related genes, including phosphorylated ERK1/2, C/EBPβ, COX2 and HAS2 in KGN cells. It was partially by interacting with AR to act as its co-regulator to inhibit C/EBPβ expression and by binding to ERK1/2 to inhibit its phosphorylation. Moreover, FHL2 abundance in hGCs was positively correlated with the basal serum testosterone concentration of patients with PCOS, and dihydrotestosterone (DHT)-induced FHL2 upregulation was mediated by AR signalling in KGN cells. Additionally, lentiviral-mediated functional FHL2 overexpression in rat ovaries for 1 week contributed to an impaired superovulatory response, displaying decreased numbers of retrieved oocytes and a lower MII oocyte rate. 3-week FHL2 overexpression rat models without superovulation led to acyclicity and polycystic ovary morphology.

INTERPRETATION

Our findings provide novel insights into the mechanisms underlying the pathogenesis of PCOS, suggesting that FHL2 could be a potential treatment target for ovulatory obstacles in PCOS. FUND: National Key Research and Development Program of China, National Natural Science Foundation, National Institutes of Health project and Shanghai Commission of Science and Technology.

FHL2 mediates podocyte Rac1 activation and foot process effacement in hypertensive nephropathy

RAAS inhibition has been the standard treatment for CKD for years because it can reduce proteinuria and hence retard renal function decline, but the proteinuria reduction effect is still insufficient in many patients. Podocyte foot process and slit diaphragm are the final barrier to prevent serum proteins leak into urine, and podocyte foot process effacement is the common pathway of all proteinruic diseases. Cell structure are regulated by three evolutionarily conserved Rho GTPases, notably, Rac1 activation is sufficient and necessary for podocyte foot process effacement, however, Rac1 inhibition is not an option for kidney disease treatment because of its systemic side effects. Four-and-a-half LIM domains protein 2 (FHL2) is highly expressed in podocytes and has been implicated in regulating diverse biological functions. Here, we used micro-dissected human kidney samples, in vitro podocyte culture experiments, and a hypertension animal model to determine the possible role of FHL2 in hypertensive nephropathy. FHL2 was abundantly upregulated in hypertensive human glomeruli and animal kidney samples. Genetic deletion of the FHL2 did not alter normal renal structure or function but mitigated hypertension-induced podocyte foot process effacement and albuminuria. Mechanistically, angiotensin II-induced podocyte cytoskeleton reorganization via FAK-Rac1 axis, FHL2 binds with FAK and is an important mediator of Ang II induced Rac1 activation, thus, FHL2 inhibition can selectively block FAK-Rac1 axis in podocyte and prevent proteinuria. These results provide important insights into the mechanisms of podocyte foot process effacement and points out a promising strategy to treat kidney disease.

Deficiency of Fhl2 leads to delayed neuronal cell migration and premature astrocyte differentiation

The four and a half LIM domains protein 2 (Fhl2) is an adaptor protein capable of mediating protein-protein interactions. Here, we report for the first time phenotypic changes in the brain of Fhl2-deficient mice. We showed that Fhl2 is expressed in neural stem cells, precursors and mature cells of neuronal lineage. Moreover, Fhl2 deficiency leads to delayed neuroblast migration in vivo, premature astroglial differentiation of neural stem cells (NSCs) in vitro, and a gliosis-like accumulation of glial fibrillary acidic protein (GFAP)-positive astrocytes in vivo that substantially increases with age. Collectively, Fhl2-deficiency in the brain interrupts the maintenance and the balanced differentiation of adult NSCs, resulting in preferentially glial differentiation and early exhaustion of the NSC pool required for adult neurogenesis.

The LIM-Only Protein FHL2 is involved in Autophagy to Regulate the Development of Skeletal Muscle Cell

Scope: Four and a half LIM domain protein 2 (FHL2) is a LIM domain protein expressed in muscle tissue whose deletion is causative of myopathies. Although FHL2 has a confirmed important role in muscle development, its autophagy-related function in muscle differentiation has not been fully determined. Methods: C2C12 cells were treated with FHL2-konwdown or FHL2-overexpression. The morphology of C2C12 cells was observed by transmission electron microscopy. The mRNA and protein abundances of muscle related genes and autophagy related genes were measured by RT-PCR and western blot. Immunofluorescence and co-immunoprecipitation assay were used to verify the interaction between FHL2 and LC3 protein. Results: FHL2 silencing reduced LC3-Ⅱ protein expression and the amount of LC3 that co-immunoprecipitated with FHL2, indicating that FHL2 interacts with LC3-Ⅱ in the formation of autophagosomes. Moreover, the expression of muscle development marker genes such as MyoD1 and MyoG was lower in FHL2-silenced C2C12 cells but not in FHL2-overexpressing C2C12 cells. Electron microscopy analysis revealed large empty autophagosomes in FHL2-silenced myoblasts, while flow cytometry suggested that FHL2 silencing made cells more vulnerable to staurosporine-induced cell death. Conclusion: These results suggest that FHL2 interacts with LC3-Ⅱ in autophagosome formation to regulate the development of muscle cells.

The Divergent Function of Androgen Receptor in Breast Cancer; Analysis of Steroid Mediators and Tumor Intracrinology

Androgen receptor (AR) is the most widely expressed steroid receptor protein in normal breast tissue and is detectable in approximately 90% of primary breast cancers and 75% of metastatic lesions. However, the role of AR in breast cancer development and progression is mired in controversy with evidence suggesting it can either inhibit or promote breast tumorigenesis. Studies have shown it to antagonize estrogen receptor alpha (ERα) DNA binding, thereby preventing pro-proliferative gene transcription; whilst others have demonstrated AR to take on the mantle of a pseudo ERα particularly in the setting of triple negative breast cancer. Evidence for a potentiating role of AR in the development of endocrine resistant breast cancer has also been mounting with reports associating high AR expression with poor response to endocrine treatment. The resurgence of interest into the function of AR in breast cancer has resulted in various emergent clinical trials evaluating anti-AR therapy and selective androgen receptor modulators in the treatment of advanced breast cancer. Trials have reported varied response rates dependent upon subtype with overall clinical benefit rates of ~19-29% for anti-androgen monotherapy, suggesting that with enhanced patient stratification AR could prove efficacious as a breast cancer therapy. Androgens and AR have been reported to facilitate tumor stemness in some cancers; a process which may be mediated through genomic or non-genomic actions of the AR, with the latter mechanism being relatively unexplored in breast cancer. Steroidogenic ligands of the AR are produced in females by the gonads and as sex-steroid precursors secreted from the adrenal glands. These androgens provide an abundant reservoir from which all estrogens are subsequently synthesized and their levels are undiminished in the event of standard hormonal therapeutic intervention in breast cancer. Steroid levels are known to be altered by lifestyle factors such as diet and exercise; understanding their potential role in dictating the function of AR in breast cancer development could therefore have wide-ranging effects in prevention and treatment of this disease. This review will outline the endogenous biochemical drivers of both genomic and non-genomic AR activation and how these may be modulated by current hormonal therapies.

Differentially Methylated Genes in Saliva are linked to Childhood Stress

Chronic and severe stress exposure in early childhood is associated with the development of psychiatric disorders. Yet, the molecular mechanisms underlying this relationship remain poorly understood. Here, we profile molecular marks (DNA methylation and gene expression) throughout the human genome to determine the associations between childhood stress exposure and gene regulation. To do so, we collected saliva tissue from prepubertal girls (mean age 10.9 ± 1.26 years) who had experienced different levels of childhood adversity, ranging from mild to severe. We found 122 differentially methylated genes (FDR P-value < 0.05) associated with high childhood stress exposures that affect brain development. Of these differentially methylated genes, 12 also differed in gene expression. To further investigate the potential effects of stress exposure on gene regulation, we examined the DNA sequences flanking all the differentially methylated loci. This analysis revealed enrichment of known binding sites for transcription factors, suggesting that DNA methylation may regulate gene expression by mediating transcription factor binding on these genes. Together, these findings indicate a possible neuromolecular mechanism linking children’s social experiences with risk for anxiety and depressive disorders.

An emerging link between LIM domain proteins and nuclear receptors

Nuclear receptors are ligand-activated transcription factors that partake in several biological processes including development, reproduction and metabolism. Over the last decade, evidence has accumulated that group 2, 3 and 4 LIM domain proteins, primarily known for their roles in actin cytoskeleton organization, also partake in gene transcription regulation. They shuttle between the cytoplasm and the nucleus, amongst other as a consequence of triggering cells with ligands of nuclear receptors. LIM domain proteins act as important coregulators of nuclear receptor-mediated gene transcription, in which they can either function as coactivators or corepressors. In establishing interactions with nuclear receptors, the LIM domains are important, yet pleiotropy of LIM domain proteins and nuclear receptors frequently occurs. LIM domain protein-nuclear receptor complexes function in diverse physiological processes. Their association is, however, often linked to diseases including cancer.

Prognostic relevance of androgen receptor expression in renal cell carcinomas

Background

Despite rapid discoveries in molecular biology of renal cell carcinoma (RCC) and advances in systemic targeted therapies, development of new diagnostic and therapeutic strategies is urgently needed. The androgen receptor (AR) has been shown to hold prognostic and predicitve value in several malignancies. Here, we studied a possible association between AR expression and prognosis in patients with RCCs.

Results

Low AR expression levels were associated with occurrence of distant metastasis and higher tumor stage in papillary and clear-cell RCCs. Importantly, multivariate Cox regression analyses revealed that AR is an independent prognostic factor for cancer-specific survival.

Materials and Methods

The expression of AR was measured by immunohistochemistry and assessed by digital image analysis using a tissue microarray containing tumor tissue of a large and well-documented series of RCC patients with long-term follow-up information. Chi-squared tests, Kaplan-Meier curves and Cox regression models were used to investigate the possible relationship between AR expression and clinico-pathological characteristics and patient survival.

Conclusions

Patients affected by AR-positive tumors exhibit a favorable prognosis by multiple Cox regression, while loss of AR expression is related to aggressive disease. Therefore, assessing AR expression offers valuable prognostic information that could improve treatment selection for metastatic disease. Moreover, our findings highlight a potential therapeutic use of AR pharmaceuticals in patients with RCCs.

LIM-Only Protein FHL2 Is a Negative Regulator of Transforming Growth Factor β1 Expression

Transforming growth factor β1 (TGF-β1) is a master cytokine in many biological processes, including tissue homeostasis, epithelial-to-mesenchymal transition, and wound repair. Here, we report that four and a half LIM-only protein 2 (FHL2) is a critical regulator of TGF-β1 expression. Devoid of a DNA-binding domain, FHL2 is a transcriptional cofactor that plays the role of coactivator or corepressor, depending on the cell and promoter contexts. We detected association of FHL2 with the TGF-β1 promoter, which showed higher activity in Fhl2^-/- cells than in wild-type (WT) cells in a reporter assay. Overexpression of FHL2 abrogates the activation of the TGF-β1 promoter, whereas the upregulation of TGF-β1 gene transcription correlates with reduced occupancy of FHL2 on the promoter. Moreover, ablation of FHL2 facilitates recruitment of RNA polymerase II on the TGF-β1 promoter, suggesting that FHL2 may be involved in chromatin remodeling in the control of TGF-β1 gene transcription. Enhanced expression of TGF-β1 mRNA and cytokine was evidenced in the livers of Fhl2^-/- mice. We tested the in vivo impact of Fhl2 loss on hepatic fibrogenesis that involves TGF-β1 activation. Fhl2^-/- mice developed more severe fibrosis than their WT counterparts. These results demonstrate the repressive function of FHL2 on TGF-β1 expression and contribute to the understanding of the TGF-β-mediated fibrogenic response.

Emerging data on androgen receptor splice variants in prostate cancer

Androgen receptor splice variants are alternatively spliced variants of androgen receptor, which are C-terminally truncated and lack the canonical ligand-binding domain. Accumulating evidence has indicated a significant role of androgen receptor splice variants in mediating resistance of castration-resistant prostate cancer to current therapies and in predicting therapeutic responses. As such, there is an urgent need to target androgen receptor splicing variants for more effective treatment of castration-resistant prostate cancer. Identification of precise and critical targeting points to deactivate androgen receptor splicing variants relies on a deep understanding of how they are generated and the mechanisms of their action. In this review, we will focus on the emerging data on their generation, clinical significance and mechanisms of action as well as the therapeutic influence of these findings.

Four-and-a-half LIM Domains 1 (FHL1) Protein Interacts with the Rho Guanine Nucleotide Exchange Factor PLEKHG2/FLJ00018 and Regulates Cell Morphogenesis

PLEKHG2/FLJ00018 is a Gβγ-dependent guanine nucleotide exchange factor for the small GTPases Rac and Cdc42 and has been shown to mediate the signaling pathways leading to actin cytoskeleton reorganization. Here we showed that the zinc finger domain-containing protein four-and-a-half LIM domains 1 (FHL1) acts as a novel interaction partner of PLEKHG2 by the yeast two-hybrid system. Among the isoforms of FHL1 (i.e. FHL1A, FHL1B, and FHL1C), FHL1A and FHL1B interacted with PLEKHG2. We found that there was an FHL1-binding region at amino acids 58-150 of PLEKHG2. The overexpression of FHL1A but not FHL1B enhanced the PLEKHG2-induced serum response element-dependent gene transcription. The co-expression of FHL1A and Gβγ synergistically enhanced the PLEKHG2-induced serum response element-dependent gene transcription. Increased transcription activity was decreased by FHL1A knock-out with the CRISPR/Cas9 system. Compared with PLEKHG2-expressing cells, the number and length of finger-like protrusions were increased in PLEKHG2-, Gβγ-, and FHL1A-expressing cells. Our results provide evidence that FHL1A interacts with PLEKHG2 and regulates cell morphological change through the activity of PLEKHG2.

Expression of the Transcriptional Coregulator FHL2 in Human Breast Cancer: A Clinicopathologic Study

OBJECTIVE

Although the Four and a Half LIM domain protein 2 (FHL2) has been suggested to play an important role in tumor development, this has not been investigated in breast cancer.

METHODS

Paraffin-embedded tissues from patients (n = 85) with primary breast cancer were submitted to immunohistochemical investigation of FHL2 expression and subsequent correlation with clinicopathologic parameters and patient survival.

RESULTS

The expression of FHL2 was confined to the cytoplasm of the tumor cells. Forty (47%) of 85 samples showed weak expression of FHL2, whereas high expression was found in 45 tumors (53%). A statistically significant positive correlation was observed between FHL2 and androgen receptor expression (P = .029). Patients with tumors expressing low amounts of FHL2 were characterized by a significantly better survival compared to those with high intratumoral FHL2 expression (P = .0215, log-rank test). The additional stratification according to adjuvant tamoxifen treatment revealed a significantly improved survival rate for patients receiving tamoxifen and being diagnosed with a tumor expressing high amounts of FHL2. This might indicate that tamoxifen is at least partially capable of reversing the negative prognostic impact of high FHL2 expression. Multivariate Cox regression analysis revealed FHL2 expression as a significant independent predictor of survival.

CONCLUSION

The specific expression in tumor tissue points to an important functional role of FHL2 in human breast cancer. Our survival data indicate that the expression of FHL2 in primary breast cancer is a potentially relevant prognostic factor. Further studies are warranted to elucidate whether analysis of FHL2 expression is suitable to predict response to antihormonal treatment with tamoxifen.

The four and a half LIM domains 2 (FHL2) regulates ovarian granulosa cell tumor progression via controlling AKT1 transcription

The four and a half LIM domains 2 (FHL2) has been shown to play important roles in the regulation of cell proliferation, survival, adhesion, motility and signal transduction in a cell type and tissue-dependent manner. However, the function of FHL2 in ovarian physiology and pathology is unclear. The aim of this study was to determine the role and functional mechanism of FHL2 in the progression of ovarian granulosa cell tumors (GCTs). Immunohistochemical analysis indicated that FHL2 was overexpressed in GCT tissues. Cellular localization of FHL2 in GCT cells was cell cycle dependent. Knockdown of FHL2 suppressed GCT cell growth, reduced cell viability and inhibited cell migration. Consistently, ectopic expression of FHL2 in GCT cells with very low endogenous FHL2 promoted cell growth, improved cell viability and enhance cell migration. Importantly, overexpression of FHL2 promoted GCT progression in vivo. Mechanistic studies indicated that FHL2 regulates AKT1 gene expression in vitro and in vivo. Knockdown of FHL2 or AKT1 in GCT cell lines induced very similar phenotypes. Ectopic expression of constitutively active AKT1 rescued FHL2 knockdown-induced arrest of GCT cell growth and reduction of GCT cell viability, suggesting that FHL2 regulates GCT cell growth and viability through controlling AKT1 expression. Finally, co-immunoprecipitation and chromatin immunoprecipitation analyses indicated that FHL2 functions as a co-activator of NFκB and AP-1 to regulate AKT1 gene transcription. In conclusion, results from the present study indicate that FHL2 exerts its oncogenic action in GCT cells via controlling AKT1 gene expression. FHL2 is a promising target for the development of novel drugs against ovarian granulosa cell tumor.

Plumbagin exhibits an anti-proliferative effect in human osteosarcoma cells by downregulating FHL2 and interfering with Wnt/β-catenin signalling

Plumbagin, a naphthoquinone constituent of Plumbago zeylanica L. (Plumbaginaceae) is widely used in traditional Chinese medicine as an antifungal, antibacterial and anti-inflammatory agent. Plumbagin is known to exhibit proapoptotic, antiangiogenic and antimetastatic effects in cancer cells. The transcriptional co-factor four and a half LIM domains 2 (FHL2) is a multifunctional adaptor protein that is involved in the regulation of gene expression, signal transduction and cell proliferation and differentiation, and also acts as a tumor suppressor or oncoprotein depending on the tissue microenvironment. The present study investigated the effect of plumbagin on FHL2 expression, Wnt/β-catenin signalling and its anti-proliferative activity in various human osteosarcoma cell lines, including SaOS2, MG63, HOS and U2OS. The cells were exposed to plumbagin and the expression of FHL2 was evaluated using western blot analysis. Furthermore, the anti-proliferative effect of plumbagin was evaluated using a 3-(4,5 dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. In addition, since FHL2 is involved in Wnt/β-catenin signaling, the effect of plumbagin on β-catenin and its primary target genes, including v-myc avian myelocytomatosis viral oncogene homolog (c-Myc) and WNT1 inducible signaling pathway protein-1 (WISP-1), was evaluated using western blot analysis. It was observed that plumbagin suppressed the expression of FHL2 and exhibited significant anti-proliferative activity in osteosarcoma cells. It also attenuated Wnt/β-catenin signalling by downregulating β-catenin and its target genes, including c-Myc and WISP-1. In conclusion, plumbagin demonstrated anti-proliferative activity in osteosarcoma cells by downregulating FHL2 and interfering with Wnt/β-catenin signalling.

Role of Nuclear Receptors in Central Nervous System Development and Associated Diseases

The nuclear hormone receptor (NHR) superfamily is composed of a wide range of receptors involved in a myriad of important biological processes, including development, growth, metabolism, and maintenance. Regulation of such wide variety of functions requires a complex system of gene regulation that includes interaction with transcription factors, chromatin-modifying complex, and the proper recognition of ligands. NHRs are able to coordinate the expression of genes in numerous pathways simultaneously. This review focuses on the role of nuclear receptors in the central nervous system and, in particular, their role in regulating the proper development and function of the brain and the eye. In addition, the review highlights the impact of mutations in NHRs on a spectrum of human diseases from autism to retinal degeneration.

Lysine-specific demethylase 1 regulates differentiation onset and migration of trophoblast stem cells

Propagation and differentiation of stem cell populations are tightly regulated to provide sufficient cell numbers for tissue formation while maintaining the stem cell pool. Embryonic parts of the mammalian placenta are generated from differentiating trophoblast stem cells (TSCs) invading the maternal decidua. Here we demonstrate that lysine-specific demethylase 1 (Lsd1) regulates differentiation onset of TSCs. Deletion of Lsd1 in mice results in the reduction of TSC number, diminished formation of trophectoderm tissues and early embryonic lethality. Lsd1-deficient TSCs display features of differentiation initiation, including alterations of cell morphology, and increased migration and invasion. We show that increased TSC motility is mediated by the premature expression of the transcription factor Ovol2 that is directly repressed by Lsd1 in undifferentiated cells. In summary, our data demonstrate that the epigenetic modifier Lsd1 functions as a gatekeeper for the differentiation onset of TSCs, whereby differentiation-associated cell migration is controlled by the transcription factor Ovol2.

Deficiency of FHL2 attenuates airway inflammation in mice and genetic variation associates with human bronchial hyper-responsiveness

BACKGROUND

Asthma is an inflammatory disease that involves airway hyper-responsiveness and mucus hypersecretion. The LIM-only protein FHL2 is a crucial modulator of multiple signal transduction pathways and functions as a scaffold in specific protein-protein interactions.

OBJECTIVE

We sought to investigate the role of FHL2 in airway inflammation.

METHODS

Allergic airway inflammation was induced in WT and FHL2-knock out (FHL2-KO) mice with ovalbumin (OVA). Lung tissue, bronchoalveolar lavage fluid (BALF) and draining lymph node cells were analysed for inflammation. FHL2 loss and gain of function studies were performed in lung epithelial cells.

RESULTS

FHL2-deficient mice challenged with OVA show significantly reduced airway inflammation as evidenced by reduced infiltration of inflammatory cells including eosinophils, dendritic cells, B cells and T cells. Furthermore, mucus production was decreased in FHL2-KO mice. In BALF, the levels of IL-5, IL-13, eotaxin-1 and eotaxin-2 were significantly lower in FHL2-KO mice. In addition, draining lymph node cells from FHL2-KO mice show reduced levels of IL-5 and IL-13. Consistent with this, OVA-specific serum IgG and IgE levels were reduced in FHL2-KO mice. We also found that phosphorylation of ERK1/2 is markedly attenuated in FHL2-KO lung. Knock-down of FHL2 in human lung epithelial cells resulted in a striking decrease in ERK1/2 phosphorylation and mRNA levels of inflammatory cytokines and MUC5AC, whereas FHL2 overexpression exhibited opposite effects. Finally, the SNP rs4851765 shows an association with the severity of bronchial hyper-responsiveness.

CONCLUSION

These results highlight functional involvement of FHL2 in airway inflammation and identify FHL2 as a novel gene associated with asthma severity in human.

Protein-protein interactions of the LIM-only protein FHL2 and functional implication of the interactions relevant in cardiovascular disease

FHL2 belongs to the LIM-domain only proteins and contains four and a half LIM domains, each of which are composed of two zinc finger structures. FHL2 exhibits specific interaction with proteins exhibiting diverse functions, including transmembrane receptors, transcription factors and transcription co-regulators, enzymes, and structural proteins. The function of these proteins is regulated by FHL2, which modulates intracellular signal transduction pathways involved in a plethora of cellular tasks. The present review summarizes the current knowledge on the protein interactome of FHL2 and provides an overview of the functional implication of these interactions in apoptosis, migration, and regulation of nuclear receptor function. FHL2 was originally identified in the heart and there is extensive literature available on the role of FHL2 in the cardiovascular system, which is also summarized in this review.

Absence of Four-and-a-Half LIM Domain Protein 2 Decreases Atherosclerosis in ApoE −/− Mice

Objective—

Four-and-a-half LIM domain protein-2 (FHL2) is expressed in endothelial cells, vascular smooth muscle cells, and leukocytes. It regulates cell survival, migration, and inflammatory response, but its role in atherogenesis is unknown.

Approach and Results—

To investigate the role of FHL2 in atherosclerosis, FHL2-deficient mice were crossed with ApoE-deficient mice, to generate ApoE/FHL2−/− mice. After high-fat diet, ApoE/FHL2−/− mice had significantly smaller atherosclerotic plaques than ApoE−/− mice in the aortic sinus, the brachiocephalic artery, and the aorta. This was associated with enhanced collagen and smooth muscle cell contents and a 2-fold reduction in macrophage content within the plaques of ApoE/FHL-2−/− versus ApoE−/− mice. This could be explained, in part, by the reduction in aortic ICAM-1 (intracellular adhesion molecule) mRNA and VCAM-1 (vascular cell adhesion molecule) protein expression in the plaque. Aortic gene expression of the chemokines CX3CL1 and CCL5 was increased in ApoE/FHL2−/− versus ApoE−/− mice. Peritoneal thioglycollate injection elicited equivalent numbers of monocytes and macrophages in both groups, but a significantly lower number of proinflammatory Ly6C high monocytes were recruited in ApoE/FHL2−/− versus ApoE−/− mice. Furthermore, mRNA levels of CX3CR1 were 2-fold higher in monocytes from ApoE/FHL2−/− versus ApoE−/− mice. Finally, we investigated the potential importance of myeloid cell FHL2 deficiency in atherosclerosis. After being irradiated, ApoE−/− or ApoE/FHL2−/− mice were transplanted with ApoE−/− or ApoE/FHL2−/− bone marrow. After high-fat diet, both chimeric groups developed smaller plaques than ApoE−/− transplanted with ApoE−/− bone marrow.

Conclusions—

These results suggest that FHL2 in both myeloid and vascular cells may play an important role in atherosclerosis by promoting proinflammatory chemokine production, adhesion molecule expression, and proinflammatory monocyte recruitment.

Splicing variants of NOL4 differentially regulate the transcription activity of Mlr1 and Mlr2 in cultured cells

Mlr1 (Mblk-1-related protein-1) and Mlr2 are mouse homologs of transcription factor Mblk-1 (Mushroom body large-type Kenyon cell-specific protein-1), which we originally identified from the honeybee brain. In the present study, aiming at identifying coregulator(s) of Mlr1 and Mlr2 from the mouse brain, we used yeast two-hybrid screening of mouse brain cDNA library to search for interaction partners of Mlr 1 and Mlr2, respectively. We identified nucleolar protein 4 (NOL4) splicing variants as major interaction partners for both Mlr1 and Mlr2. Among the three murine NOL4 splicing variants, we further characterized NOL4-S, which lacks an N-terminal part of NOL4-L, and NOL4-SΔ, which lacks nuclear localization signal (NLS)-containing domain of NOL4-S. A GST pull-down assay revealed that Mlr1 interacts with both NOL4-S and NOL4-SΔ, whereas Mlr2 interacts with NOL4-S, but not with NOL4-SΔ. These results indicate that the NLS-containing domain of NO4-S Is necessary for in vitro binding with Mlr2, but not for that with Mlr1. Furthermore, a luciferase assay using Schneider's Line 2 cells revealed that transactivation activity of Mlr1 was significantly suppressed by both NOL4-S and NOL4-SΔ, with almost complete suppression by NOL4-SΔ. In contrast, transactivation activity of Mlr2 was significantly suppressed by NOL4-S but rather activated by NOL4-SΔ. Our findings suggest that transactivation activities of Mlr1 and Mlr2 are differentially regulated by splicing variants of NOL4, which are expressed in a tissue-selective manner.

Identification of gene co-expression clusters in liver tissues from multiple porcine populations with high and low backfat androstenone phenotype

Background

Boar taint is principally caused by accumulation of androstenone and skatole in adipose tissues. Studies have shown high heritability estimates for androstenone whereas skatole production is mainly dependent on nutritional factors. Androstenone is a lipophilic steroid mainly metabolized in liver. Majority of the studies on hepatic androstenone metabolism focus only on a single breed and very few studies account for population similarities/differences in gene expression patterns. In this work, we concentrated on population similarities in gene expression to identify the common genes involved in hepatic androstenone metabolism of multiple pig populations. Based on androstenone measurements, publicly available gene expression datasets from three porcine populations were compiled into either low or high androstenone dataset. Gene expression correlation coefficients from these datasets were converted to rank ratios and joint probabilities of these rank ratios were used to generate dataset specific co-expression clusters. Finally, these networks were clustered using a graph clustering technique.

Results

Cluster analysis identified a number of statistically significant co-expression clusters in the dataset. Further enrichment analysis of these clusters showed that one of the clusters from low androstenone dataset was highly enriched for xenobiotic, drug, cholesterol and lipid metabolism and cytochrome P450 associated metabolism of drugs and xenobiotics. Literature references revealed that a number of genes in this cluster were involved in phase I and phase II metabolism. Physical and functional similarity assessment showed that the members of this cluster were dispersed across multiple clusters in high androstenone dataset, possibly indicating a weak co-expression of these genes in high androstenone dataset.

Conclusions

Based on these results we hypothesize that majority of the genes in this cluster forms a signature co-expression cluster in low androstenone dataset in our experiment and that majority of the members of this cluster might be responsible for hepatic androstenone metabolism across all the three populations used in our study. We propose these results as a background work towards understanding breed similarities in hepatic androstenone metabolism. Additional large scale experiments using data from multiple porcine breeds are necessary to validate these findings.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-014-0158-8) contains supplementary material, which is available to authorized users.

Enhanced FHL2 and TGF-β1 Expression Is Associated With Invasive Growth and Poor Survival in Malignant Melanomas

OBJECTIVES

This study examines the expression and the role of four-and-a-half LIM domains protein 2 (FHL2) and transforming growth factor β1 (TGF-β1) in human malignant melanoma. It is determined whether both proteins influence melanoma survival time.

METHODS

We analyzed the immunohistochemical staining intensities of FHL2 and TGF-β1 in normal skin and in 50 malignant melanomas with different mutation status (BRAF-V600E, NRAS codon 61 mutation, and wild type). Survival data were available for 45 cases.

RESULTS

In melanocytes of nonneoplastic human skin, FHL2 expression was absent. In contrast, 38 (76%) of 50 melanomas showed strong cytoplasmic and partly nuclear FHL2 expression. At the invasion front, cytoplasmic TGF-β1 staining was observed in 32 (64%) of 50 melanomas, and a correlation of FHL2 and TGF-β1 staining intensities was detectable. In follow-up analyses, enhanced FHL2 and TGF-β1 staining intensities in the tumor invasion front were associated with poor survival.

CONCLUSIONS

Enhanced FHL2 and TGF-β1 expression is correlated with poor survival in human malignant melanoma. Protumorigenic effects of autocrine TGF-β1 secretion might be exerted by induction of FHL2 expression in melanoma cells. Since melanomas treated with targeted therapies often do not show sufficient response rates, inhibition of FHL2 and/or TGF-β1 might be a promising therapeutic approach.

Tumoral expression of nuclear cofactor FHL2 is associated with lymphatic metastasis in sporadic but not in HNPCC-associated colorectal cancer

BACKGROUND

Four and a half LIM domain protein-2 (FHL2) is part of the focal adhesion structures modulating cell motility. FHL2 may translocate into the nucleus serving as a transcriptional cofactor binding several transcription factors. Overexpression of FHL2 has been linked to cancer progression in various neoplasias. The aim of the present study was to determine, whether FHL2's function as nuclear cofactor plays a prognostic role in invading tumor cells of sporadic and HNPCC-associated colorectal cancer (CRC).

DESIGN

Immunohistochemical staining intensity of nuclear FHL2 was quantified by Remmele score analysing 47 sporadic and 42 HNPCC-associated colorectal cancers. Analysis was restricted to carcinoma cells of the tumoral invasion front.

RESULTS

Confocal microscopy detected nuclear expression of FHL2 in colon cancer cells and absence of nuclear FHL2 signal in normal colon enterocytes. In colon cancer, nuclear FHL2 expression was predominantly observed in low-differentiated, often mucinous tumor areas. 42.55% of sporadic and 54.76% of HNPCC-associated CRC showed enhanced (Remmele score 6-12) nuclear FHL2 expression in the carcinoma cells of the tumoral advancing edge. Enhanced nuclear FHL2 expression was significantly linked to lymphatic metastasis in sporadic CRC (p=0.0197) and almost reached significance in HNPCC-associated CRC (p=0.0545). In contrast, nuclear FHL2 expression was neither associated with hematogenic metastasis in sporadic (p=0.7087) nor in HNPCC-associated colorectal cancer (p=0.3007).

CONCLUSIONS

We recently demonstrated that enhanced nuclear FHL2 expression in tumor stroma of sporadic colon cancer is associated with lymphatic metastasis. The results of the present study indicate a synergistic effect of nuclear cofactor FHL2 in tumor cells as well as in peritumoral stroma cells promoting lymphatic metastasis in sporadic CRC. As HNPCC-associated tumors did not show a significant association between tumoral nuclear FHL2 expression and lymphatic metastasis we speculate, that the intensive lymphocytic immune response in HNPCC precludes a direct contact of tumor cells and stromal cells resulting in reduced lymphatic spread.

LIM-only protein FHL2 is a positive regulator of liver X receptors in smooth muscle cells involved in lipid homeostasis

The LIM-only protein FHL2 is expressed in smooth muscle cells (SMCs) and inhibits SMC-rich-lesion formation. To further elucidate the role of FHL2 in SMCs, we compared the transcriptomes of SMCs derived from wild-type (WT) and FHL2 knockout (KO) mice. This revealed that in addition to the previously recognized involvement of FHL2 in SMC proliferation, the cholesterol synthesis and liver X receptor (LXR) pathways are altered in the absence of FHL2. Using coimmunoprecipitation experiments, we found that FHL2 interacts with the two LXR isoforms, LXRα and LXRβ. Furthermore, FHL2 strongly enhances transcriptional activity of LXR element (LXRE)-containing reporter constructs. Chromatin immunoprecipitation (ChIP) experiments on the ABCG1 promoter revealed that FHL2 enhances the association of LXRβ with DNA. In line with these observations, we observed reduced basal transcriptional LXR activity in FHL2-KO SMCs compared to WT SMCs. This was also reflected in reduced expression of LXR target genes in intact aorta and aortic SMCs of FHL2-KO mice. Functionally, the absence of FHL2 resulted in attenuated cholesterol efflux to both ApoA-1 and high-density lipoprotein (HDL), in agreement with reduced LXR signaling. Collectively, our findings demonstrate that FHL2 is a transcriptional coactivator of LXRs and points toward FHL2 being an important determinant of cholesterol metabolism in SMCs.

TGF-β1-dependent induction and nuclear translocation of FHL2 promotes keratin expression in pilomatricoma

Pilomatricoma is a tumour derived from hair matrix cells, which shows progressive keratin expression. Tumorigenesis is frequently associated with activating mutations in β-catenin gene inducing nuclear expression of β-catenin protein. The present study analysed the role of transforming growth factor-β1 (TGF-β1) and four-and-a-half LIM domain protein 2 (FHL2) in pilomatricoma in synopsis with their expression patterns in human anagen hair. Human anagen hair showed TGF-β1 and nuclear FHL2 expression in the outer root sheath layer separated from nuclear β-catenin staining, which was observed in cells of matrix and inner root sheath layers. Correspondingly, 41 out of 50 pilomatricomas showed co-labelling of TGF-β1 and nuclear FHL2 in tumour cells, which mostly lacked nuclear β-catenin expression. Tumoural proliferation (ki67) was associated with nuclear β-catenin staining but not with expression of nuclear FHL2. In early pilomatricomas, TGF-β1 expression was observed in few peripheral tumour cells showing absent or faint nuclear FHL2 co-staining. TGF-β1 expression extended in growing tumours going along with strong nuclear FHL2 co-labelling as well as progressive keratin 14 and keratin 1 expression. In vitro, cultured human keratinocytes showed weak to marked autocrine TGF-β1 expression; in case of enhanced TGF-β1 expression associated with keratin 10 staining. TGF-β1-treatment of cultured human keratinocytes induced nuclear and cytoplasmatic FHL2 staining as well as keratin 14 staining. Accordingly, siRNA-mediated FHL2 knockdown of TGF-β1-stimulated keratinocytes reduced keratin 14 staining. In conclusion, tumoural TGF-β1 secretion seems to induce nuclear translocation of co-factor FHL2 mediating progressive keratin expression in pilomatricoma.

The evolution of cichlid fish egg-spots is linked with a cis-regulatory change

The origin of novel phenotypic characters is a key component in organismal diversification; yet, the mechanisms underlying the emergence of such evolutionary novelties are largely unknown. Here we examine the origin of egg-spots, an evolutionary innovation of the most species-rich group of cichlids, the haplochromines, where these conspicuous male fin colour markings are involved in mating. Applying a combination of RNAseq, comparative genomics and functional experiments, we identify two novel pigmentation genes, fhl2a and fhl2b, and show that especially the more rapidly evolving b-paralog is associated with egg-spot formation. We further find that egg-spot bearing haplochromines, but not other cichlids, feature a transposable element in the cis-regulatory region of fhl2b. Using transgenic zebrafish, we finally demonstrate that this region shows specific enhancer activities in iridophores, a type of pigment cells found in egg-spots, suggesting that a cis-regulatory change is causally linked to the gain of expression in egg-spot bearing haplochromines.

The mechanisms underlying the emergence of novel morphological traits are largely unknown. Here, the authors show that cis-regulatory changes controlling the expression of the fhl2b pigmentation gene are associated with the evolution of egg-spots colour markings in the male fins of a group of cichlids.