Brief report: VGLL4 is a novel regulator of survival in human embryonic stem cells

Comparative computational analysis to distinguish mesenchymal stem cells from fibroblasts

Introduction

Mesenchymal stem cells (MSCs) are considered to be the most promising stem cell type for cell-based therapies in regenerative medicine. Based on their potential to home to diseased body sites following a therapeutically application, these cells could (i) differentiate then into organ-specific cell types to locally restore injured cells or, most prominently, (ii) foster tissue regeneration including immune modulations more indirectly by secretion of protective growth factors and cytokines. As tissue-resident stem cells of mesenchymal origin, these cells are morphologically and even molecularly- at least concerning the classical marker genes- indistinguishable from similar lineage cells, particularly fibroblasts.

Methods

Here we used microarray-based gene expression and global DNA methylation analyses as well as accompanying computational tools in order to specify differences between MSCs and fibroblasts, to further unravel potential identity genes and to highlight MSC signaling pathways with regard to their trophic and immunosuppressive action.

Results

We identified 1352 differentially expressed genes, of which in the MSCs there is a strong signature for e.g., KRAS signaling, known to play essential role in stemness maintenance, regulation of coagulation and complement being decisive for resolving inflammatory processes, as well as of wound healing particularly important for their regenerative capacity. Genes upregulated in fibroblasts addressed predominately transcription and biosynthetic processes and mapped morphological features of the tissue. Concerning the cellular identity, we specified the already known HOX code for MSCs, established a potential HOX code for fibroblasts, and linked certain HOX genes to functional cell-type-specific properties. Accompanied methylation profiles revealed numerous regions, especially in HOX genes, being differentially methylated, which might provide additional biomarker potential.

Discussion

Conclusively, transcriptomic together with epigenetic signatures can be successfully be used for the definition (cellular identity) of MSCs versus fibroblasts as well as for the determination of the superior functional properties of MSCs, such as their immunomodulatory potential.

The time-resolved genomic impact of Wnt/β-catenin signaling

Wnt signaling orchestrates gene expression via its effector, β-catenin. However, it is unknown whether β-catenin binds its target genomic regions simultaneously and how this impacts chromatin dynamics to modulate cell behavior. Using a combination of time-resolved CUT&RUN against β-catenin, ATAC-seq, and perturbation assays in different cell types, we show that Wnt/β-catenin physical targets are tissue-specific, β-catenin "moves" on different loci over time, and its association to DNA accompanies changing chromatin accessibility landscapes that determine cell behavior. In particular, Wnt/β-catenin progressively shapes the chromatin of human embryonic stem cells (hESCs) as they undergo mesodermal differentiation, a behavior that we define as "plastic." In HEK293T cells, on the other hand, Wnt/β-catenin drives a transient chromatin opening, followed by re-establishment of the pre-stimulation state, a response that we define as "elastic." Future experiments shall assess whether other cell communication mechanisms, in addition to Wnt signaling, are ruled by time, cellular idiosyncrasies, and chromatin constraints. A record of this paper's transparent peer review process is included in the supplemental information.

VGLL4 promotes vascular endothelium specification via TEAD1 in the vascular organoids and human pluripotent stem cells-derived endothelium model

BACKGROUND

We have shown that Hippo-YAP signaling pathway plays an important role in endothelial cell differentiation. Vestigial-like family member 4 (VGLL4) has been identified as a YAP inhibitor. However, the exact function of VGLL4 in vascular endothelial cell development remains unclear. In this study, we investigated the role of VGLL4, in human endothelial lineage specification both in 3D vascular organoid and 2D endothelial cell differentiation.

METHODS AND RESULTS

In this study, we found that VGLL4 was increased during 3D vascular organoids generation and directed differentiation of human embryonic stem cells H1 towards the endothelial lineage. Using inducible ectopic expression of VGLL4 based on the piggyBac system, we proved that overexpression of VGLL4 in H1 promoted vascular organoids generation and endothelial cells differentiation. In contrast, VGLL4 knockdown (heterozygous knockout) of H1 exhibited inhibitory effects. Using bioinformatics analysis and protein immunoprecipitation, we further found that VGLL4 binds to TEAD1 and facilitates the expression of endothelial master transcription factors, including FLI1, to promote endothelial lineage specification. Moreover, TEAD1 overexpression rescued VGLL4 knockdown-mediated negative effects.

CONCLUSIONS

In summary, VGLL4 promotes EC lineage specification both in 3D vascular organoid and 2D EC differentiation from pluripotent stem cell, VGLL4 interacts with TEAD1 and facilitates EC key transcription factor, including FLI1, to enhance EC lineage specification.

Single-cell response to Wnt signaling activation reveals uncoupling of Wnt target gene expression

Wnt signaling drives nuclear translocation of β-catenin and its subsequent association with the DNA-bound TCF/LEF transcription factors, which dictate target gene specificity by recognizing Wnt responsive elements across the genome. β-Catenin target genes are therefore thought to be collectively activated upon Wnt pathway stimulation. However, this appears in contrast with the non-overlapping patterns of Wnt target gene expression in several contexts, including early mammalian embryogenesis. Here we followed Wnt target gene expression in human embryonic stem cells after Wnt pathway stimulation at a single-cell resolution. Cells changed gene expression program over time consistent with three key developmental events: i) loss of pluripotency, ii) induction of Wnt target genes, and iii) mesoderm specification. Contrary to our expectation, not all cells displayed equal amplitude of Wnt target gene activation; rather, they distributed in a continuum from strong to weak responders when ranked based on the expression of the target AXIN2. Moreover, high AXIN2 did not always correspond to elevated expression of other Wnt targets, which were activated in different proportions in individual cells. The uncoupling of Wnt target gene expression was also identified in single cell transcriptomics profiling of other Wnt-responding cell types, including HEK293T, murine developing forelimbs, and human colorectal cancer. Our finding underlines the necessity to identify additional mechanisms that explain the heterogeneity of the Wnt/β-catenin-mediated transcriptional outputs in single cells.

Leveraging Hot Spots of TEAD-Coregulator Interactions in the Design of Direct Small Molecule Protein-Protein Interaction Disruptors Targeting Hippo Pathway Signaling

The Hippo signaling pathway is a highly conserved pathway that plays important roles in the regulation of cell proliferation and apoptosis. Transcription factors TEAD1-4 and transcriptional coregulators YAP/TAZ are the downstream effectors of the Hippo pathway and can modulate Hippo biology. Dysregulation of this pathway is implicated in tumorigenesis and acquired resistance to therapies. The emerging importance of YAP/TAZ-TEAD interaction in cancer development makes it a potential therapeutic target. In the past decade, disrupting YAP/TAZ-TEAD interaction as an effective approach for cancer treatment has achieved great progress. This approach followed a trajectory wherein peptidomimetic YAP-TEAD protein-protein interaction disruptors (PPIDs) were first designed, followed by the discovery of allosteric small molecule PPIDs, and currently, the development of direct small molecule PPIDs. YAP and TEAD form three interaction interfaces. Interfaces 2 and 3 are amenable for direct PPID design. One direct YAP-TEAD PPID (IAG933) that targets interface 3 has entered a clinical trial in 2021. However, in general, strategically designing effective small molecules PPIDs targeting TEAD interfaces 2 and 3 has been challenging compared with allosteric inhibitor development. This review focuses on the development of direct surface disruptors and discusses the challenges and opportunities for developing potent YAP/TAZ-TEAD inhibitors for the treatment of cancer.

Hsa_circ_0006427 Suppresses Multiplication, Migration and Invasion of Non-Small Cell Lung Cancer Cells through miR-346/VGLL4 Pathway

Objective

Circular RNAs (circRNAs) are identified as key modulators in cancer biology. Nonetheless, the role of circ_0006427 in non-small cell lung cancer (NSCLC) and its modulatory mechanism are undefined. This study aimed to investigate the potential function and mechanism of circ_0006427 in NSCLC.

Materials and Methods

In this experimental study, circ_0006427, miR-346 and vestigial like family member 4 (VGLL4) mRNA expressions were analyzed in NSCLC tissues and cells, using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Multiplication, migration and invasion of NSCLC cells were examined using the CCK-8 method and Transwell experiment, respectively. Dual-luciferase reporter gene experiments were conducted to identify the paring relationship between circ_0006427 and miR-346. Western blot was employed to determine expressions of VGLL4 and epithelial-mesenchymal transition (EMT) markers on protein levels. Immuno-histochemistry (IHC) method was adopted to assess VGLL4 protein expression in NSCLC tissues.

Results

Circ_0006427 expression was down-regulated in NSCLC tissues and cells, and circ_0006427 suppressed multiplication, migration, invasion and EMT of NSCLC cells. miR-346 expression was upregulated in NSCLC tissues and cells, and miR-346 worked as a target of circ_0006427. VGLL4 was down-regulated in NSCLC tissues and cells, and knockdown of VGLL4 accelerated multiplication, migration, invasion and EMT of NSCLC cells. Circ_0006427 enhanced VGLL4 expression by competitively binding with miR-346.

Conclusion

Circ_0006427/miR-346/VGLL4 axis regulated NSCLC progression.

Integrated loss- and gain-of-function screens define a core network governing human embryonic stem cell behavior

In this Resource/Methodology, Naxerova et al. describe an integrated genome-scale loss- and gain-of-function screening approach to identify genetic networks governing embryonic stem cell proliferation and differentiation into the three germ layers. They identify a deep link between pluripotency maintenance and survival by showing that genetic alterations that cause pluripotency dissolution simultaneously increase apoptosis resistance, and their results show the power of integrated multilayer genetic screening for the robust mapping of complex genetic networks.

Understanding the genetic control of human embryonic stem cell function is foundational for developmental biology and regenerative medicine. Here we describe an integrated genome-scale loss- and gain-of-function screening approach to identify genetic networks governing embryonic stem cell proliferation and differentiation into the three germ layers. We identified a deep link between pluripotency maintenance and survival by showing that genetic alterations that cause pluripotency dissolution simultaneously increase apoptosis resistance. We discovered that the chromatin-modifying complex SAGA and in particular its subunit TADA2B are central regulators of pluripotency, survival, growth, and lineage specification. Joint analysis of all screens revealed that genetic alterations that broadly inhibit differentiation across multiple germ layers drive proliferation and survival under pluripotency-maintaining conditions and coincide with known cancer drivers. Our results show the power of integrated multilayer genetic screening for the robust mapping of complex genetic networks.

Identification of Genes Whose Expression Overlaps Age Boundaries and Correlates with Risk Groups in Paediatric and Adult Acute Myeloid Leukaemia

Simple Summary

To better understand whether acute myeloid leukaemia differs between children and adults, we have analysed the expression of genes in samples from both patient groups. Using previously published data, we compared gene expression between patient risk subgroups. We examined patients who had a poor chance of survival, based on clinical assessments, and those with a good chance of survival, to see whether there was any difference in the genes expressed in their leukaemic cells. Then we compared the genes on these lists between adults and children with acute myeloid leukaemia. We believe that patients with good or poor survival chances express genes that provide insights into how leukaemic cells behave. We hope that this work will provide new information about the mechanisms that underlie acute myeloid leukaemia and answer questions on the ways this form of leukaemia is similar in adults and children, which will then tell us whether the same treatments could be used for both age groups of patients.

Abstract

Few studies have compared gene expression in paediatric and adult acute myeloid leukaemia (AML). In this study, we have analysed mRNA-sequencing data from two publicly accessible databases: (1) National Cancer Institute’s Therapeutically Applicable Research to Generate Effective Treatments (NCI-TARGET), examining paediatric patients, and (2) The Cancer Genome Atlas (TCGA), examining adult patients with AML. With a particular focus on 144 known tumour antigens, we identified STEAP1, SAGE1, MORC4, SLC34A2 and CEACAM3 as significantly different in their expression between standard and low risk paediatric AML patient subgroups, as well as between poor and good, and intermediate and good risk adult AML patient subgroups. We found significant differences in event-free survival (EFS) in paediatric AML patients, when comparing standard and low risk subgroups, and quartile expression levels of BIRC5, MAGEF1, MELTF, STEAP1 and VGLL4. We found significant differences in EFS in adult AML patients when comparing intermediate and good, and poor and good risk adult AML patient subgroups and quartile expression levels of MORC4 and SAGE1, respectively. When examining Kyoto Encyclopedia of Genes and Genomes (KEGG) (2016) pathway data, we found that genes altered in AML were involved in key processes such as the evasion of apoptosis (BIRC5, WNT1) or the control of cell proliferation (SSX2IP, AML1-ETO). For the first time we have compared gene expression in paediatric AML patients with that of adult AML patients. This study provides unique insights into the differences and similarities in the gene expression that underlies AML, the genes that are significantly differently expressed between risk subgroups, and provides new insights into the molecular pathways involved in AML pathogenesis.

Zebrafish Vestigial Like Family Member 4b Is Required for Valvulogenesis Through Sequestration of Transcription Factor Myocyte Enhancer Factor 2c

A variety of cardiac transcription factors/cofactors, signaling pathways, and downstream structural genes integrate to form the regulatory hierarchies to ensure proper cardiogenesis in vertebrate. Major interaction proteins of the transcription cofactor vestigial like family member 4 (VGLL4) include myocyte enhancer factor 2 (MEF2) and TEA domain transcription factors (TEAD), both of which play important roles in embryonic cardiac development and in adulthood. In this study, we identified that the deficiency of zebrafish vgll4b paralog, a unique family member expressed in developing heart, led to an impaired valve development. Mechanistically, in vgll4b mutant embryos the disruption of Vgll4b-Mef2c complex, rather than that of Vgll4b-Tead complex, resulted in an aberrant expression of krüppel-like factor 2a (klf2a) in endocardium. Such misexpression of klf2a eventually evoked the valvulogenesis defects. Our findings suggest that zebrafish Vgll4b plays an important role in modulating the transcription activity of Mef2c on klf2a during valve development in a blood-flow-independent manner.

Dual function of VGLL4 in muscle regeneration

VGLL4 has previously been identified as a negative regulator of YAP. Here we show that VGLL4 regulates muscle regeneration in both YAP-dependent and YAP-independent manners at different stages. Knockout of VGLL4 in mice leads to smaller myofiber size and defective muscle contraction force. Furthermore, our studies reveal that knockout of VGLL4 results in increased muscle satellite cells proliferation and impaired myoblast differentiation, which ultimately leads to delayed muscle regeneration. Mechanistically, the results show that VGLL4 works as a conventional repressor of YAP at the proliferation stage of muscle regeneration. At the differentiation stage, VGLL4 acts as a co-activator of TEAD4 to promote MyoG transactivation and facilitate the initiation of differentiation in a YAP-independent manner. Moreover, VGLL4 stabilizes the protein-protein interactions between MyoD and TEAD4 to achieve efficient MyoG transactivation. Our findings define the dual roles of VGLL4 in regulating muscle regeneration at different stages and may open novel therapeutic perspectives for muscle regeneration.

Serotonin and YAP/VGLL4 Balance Correlated with Progression and Poor Prognosis of Hepatocellular Carcinoma

YAP-TEAD complex plays an important role in tumorigenesis. 5-HT is proved to upregulate YAP expression by our previous study and VGLL4 is found to compete with YAP for binding to TEAD in several of cancers. Here, we investigated whether 5-HT could affect progression and prognosis of hepatocellular carcinoma (HCC) patients and regulate YAP/VGLL4 balance. We found that 5-HT and YAP/VGLL4 ratio were higher in HCC patients and closely related with progression and poor prognosis. Furthermore, 5-HT level, YAP/VGLL4 ratio and tumor size were proved as independent risk factors of HCC patients in our study. Based on the independent risk factors, nomogram was established to exactly predict prognosis of HCC patients. Additionally, the study revealed that a higher total point of the nomogram was closely correlated with poorer prognosis. As a result, 5-HT might contribute to the progression and poor prognosis of hepatocellular carcinoma via regulating YAP/VGLL4 balance. Therefore, the established nomogram based on the independent risk factors may become an important part of HCC prediction system and YAP/VGLL4 balance may be a potential therapeutic target in future.

VGLL4 is a transcriptional cofactor acting as a novel tumor suppressor via interacting with TEADs

Vestigial Like Family Member 4 (VGLL4) is a transcriptional cofactor of VGLL family, which includes VGLL1-4. Unlike other members of VGLL family, VGLL4 was described as a novel tumor suppressor containing two TDU motifs. VGLL4 executes its biological function through two TDU domains via interacting with TEA domain (TEAD) transcription factors. Lower expression of VGLL4 usually indicates poor survival in many cancers, such as lung cancer, gastric cancer, breast cancer, colorectal cancer, bladder cancer, pancreatic adenocarcinoma and esophageal squamous cancer. In cancer cells, the expression of VGLL4 is lower than that of normal tissues, moreover, expression level of VGLL4 is positively related to survival rate. VGLL4 is found to play an important role in several signal pathways, mainly acts as a tumor suppressor interacting with TEADs. In Hippo signaling pathway, VGLL4 competes with YAP in binding to TEADs and inhibits the downstream of YAP. In Wnt/β-catenin signaling pathway, VGLL4 negatively regulates Wnt/β-catenin signaling pathway via inhibiting β-catenin and TCF (T-cell factor). VGLL4 can also suppress epithelial-mesenchymal transition (EMT) and contribute to apoptosis signaling pathway.

Expression Profiling of Clinical Specimens Supports the Existence of Neural Progenitor-Like Stem Cells in Basal Breast Cancers

BACKGROUND

We previously characterized in salivary adenoid cystic carcinoma (ACC) a novel population of cancer stem cells (CSCs) marked by coexpression of 2 stemness genes, sex-determining region Y (SRY)-related HMG box-containing factor 10 (SOX10) and CD133. We also reported that in ACC and basal-like breast carcinoma (BBC), a triple-negative breast cancer subtype, expression of SOX10 similarly demarcates a highly conserved gene signature enriched with neural stem cell genes. On the basis of these findings, we hypothesized that BBC might be likewise driven by SOX10-positive (SOX10⁺)/CD133⁺ cells with neural stem cell properties.

MATERIALS AND METHODS

To validate our hypothesis on clinical data, we used a novel approach to meta-analysis that merges gene expression data from independent breast cancer studies and ranks genes according to statistical significance of their coexpression with the gene of interest. Genes that showed strong association with CD133/PROM1 as well as SOX10 were validated across different platforms and data sets and analyzed for enrichment with genes involved in neurogenesis.

RESULTS

We identified in clinical breast cancer data sets a highly conserved SOX10/PROM1 gene signature that contains neural stem cell markers common for Schwann cells, ACC, BBC, and melanoma. Identification of tripartite motif-containing 2 (TRIM2), TRIM29, MPZL2, potassium calcium-activated channel subfamily N member 4 (KCNN4), and V-set domain containing T cell activation inhibitor 1 (VTCN1)/B7 homolog 4 (B7H4) within this signature provides insight into molecular mechanisms of CSC maintenance.

CONCLUSION

Our results suggest that BBC is driven by SOX10⁺/CD133⁺ cells that express neural stem cell-specific markers and share molecular similarities with CSCs of neural crest origin. Our study provides clinically relevant information on possible drivers of these cells that might facilitate development of CSC-targeting therapies against this cancer distinguished with poor prognosis and resistance to conventional therapies.

Characterisation of non-coding genetic variation in histamine receptors using AnNCR-SNP

Almost 90 % of disease-associated genetic variants found using genome wide association studies (GWAS) are located in non-coding regions of the genome. Such variants can affect phenotype by altering important regulatory elements such as promoters, enhancers or repressors, leading to changes in gene expression and consequently disease, such as thyroid cancer and allergic diseases. A number of allergy and atopy related diseases such as asthma and atopic dermatitis are related to histamine receptors; however, these diseases are not fully characterized at the molecular level. Moreover, candidate gene based studies of common variants known as single nucleotide polymorphism (SNPs) located in the coding regions of these receptors have given mixed results. It is important to complement these approaches by identifying and characterising non-coding variants in order to further elucidate the role of these receptors in disease. Here we present an analysis of histamine receptor genes using the tool AnNCR-SNP to characterise variants in non-coding genomic regions. AnNCR-SNP combines bioinformatics and experimental data sets from various sources to predict the effects of genetic variation on gene expression regulation. We find many SNPs located in areas of open chromatin, overlapping with transcription factor binding sites and associated with changes in gene expression in expression quantitative trait loci (eQTL) experiments. Here we present the results as a catalogue of non-coding variation in histamine receptor genes to aid histamine researchers in identifying putative functional SNPs found in GWAS for further validation, and to help select variants for candidate gene studies.

The TEAD Family and Its Oncogenic Role in Promoting Tumorigenesis

The TEAD family of transcription factors is necessary for developmental processes. The family members contain a TEA domain for the binding with DNA elements and a transactivation domain for the interaction with transcription coactivators. TEAD proteins are required for the participation of coactivators to transmit the signal of pathways for the downstream signaling processes. TEADs also play an important role in tumor initiation and facilitate cancer progression via activating a series of progression-inducing genes, such as CTGF, Cyr61, Myc and Gli2. Recent studies have highlighted that TEADs, together with their coactivators, promote or even act as the crucial parts in the development of various malignancies, such as liver, ovarian, breast and prostate cancers. Furthermore, TEADs are proposed to be useful prognostic biomarkers due to the ideal correlation between high expression and clinicopathological parameters in gastric, breast, ovarian and prostate cancers. In this review, we summarize the functional role of TEAD proteins in tumorigenesis and discuss the key role of TEAD transcription factors in the linking of signal cascade transductions. Improved knowledge of the TEAD proteins will be helpful for deep understanding of the molecular mechanisms of tumorigenesis and identifying ideal predictive or prognostic biomarkers, even providing clinical translation for anticancer therapy in human cancers.

Downregulation of VGLL4 in the progression of esophageal squamous cell carcinoma

VGLL4, a member of the Vestigial-like (VGLL) proteins, has been reported to be dysregulated in several cancer types. However, its function in esophageal squamous cell carcinoma (ESCC) remains poorly understood. Here, it was found that the expression level of VGLL4 was decreased in ESCC tissues. Moreover, forced expression of VGLL4 in ESCC cells inhibited cell growth and migration, while knockdown of VGLL4 expression promoted the tumorigenecity of ESCC cells. Mechanistically, VGLL4 regulated the growth and motility of ESCC cells through downregulating the expression of connective tissue growth factor (CTGF), a known oncogene in the progression of ESCC. Taken together, our study suggested that downregulation of VGLL4 was very important in the progression of ESCC, and restoring the function of VGLL4 might be a promising therapeutic strategy for ESCC.