Functional impact of heterogeneous nuclear ribonucleoprotein A2/B1 in smooth muscle differentiation from stem cells and embryonic arteriogenesis

Bioinformatics Analysis of Hub Genes Involved in Smoke-Induced Hemifacial Microsomia Pathogenesis

OBJECTIVE

Tobacco smoke is a recognized teratogen, which increases the risk for hemifacial microsomia (HFM) of the fetus during maternal pregnancy. The present study aimed to explore potential mechanisms and verify hub genes of HFM associated with smoke and tobacco smoke pollution (TSP) via bioinformatics methods.

METHODS

Hemifacial microsomia and smoke and TSP pathogenic genes were obtained. A protein-protein interactional (PPI) network was constructed. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses and molecular complex detection were performed by Metascape. Finally, we used the cytoHubba plug-in to screen the hub genes.

RESULTS

A total of 43 HFM genes and 50 optimal smoke candidate genes were selected. Functional enrichment analysis largely focused on tissue morphogenesis and development. Two modules were identified from the PPI network, and 10 hub genes were screened out. The genes most relevant to smoke-induced HFM pathogenesis included TP53 , ESR1 , ESR2 , and HNRNPL.

CONCLUSIONS

This study identified some significant hub genes, pathways, and modules of HFM related to smoke by bioinformatics analyses. Our results suggest that the TP53 , ESR1 , ESR2 , and HNRNPL gene subfamilies may have played a major role in HFM induced by smoke and TSP.

Research Progress on the Structural and Functional Roles of hnRNPs in Muscle Development

Heterogeneous nuclear ribonucleoproteins (hnRNPs) are a superfamily of RNA-binding proteins consisting of more than 20 members. These proteins play a crucial role in various biological processes by regulating RNA splicing, transcription, and translation through their binding to RNA. In the context of muscle development and regeneration, hnRNPs are involved in a wide range of regulatory mechanisms, including alternative splicing, transcription regulation, miRNA regulation, and mRNA stability regulation. Recent studies have also suggested a potential association between hnRNPs and muscle-related diseases. In this report, we provide an overview of our current understanding of how hnRNPs regulate RNA metabolism and emphasize the significance of the key members of the hnRNP family in muscle development. Furthermore, we explore the relationship between the hnRNP family and muscle-related diseases.

RNA-binding proteins in vascular inflammation and atherosclerosis

Atherosclerotic cardiovascular disease (ASCVD) remains the major cause of premature death and disability worldwide, even when patients with an established manifestation of atherosclerotic heart disease are optimally treated according to the clinical guidelines. Apart from the epigenetic control of transcription of the genetic information to messenger RNAs (mRNAs), gene expression is tightly controlled at the post-transcriptional level before the initiation of translation. Although mRNAs are traditionally perceived as the messenger molecules that bring genetic information from the nuclear DNA to the cytoplasmic ribosomes for protein synthesis, emerging evidence suggests that processes controlling RNA metabolism, driven by RNA-binding proteins (RBPs), affect cellular function in health and disease. Over the recent years, vascular endothelial cell, smooth muscle cell and immune cell RBPs have emerged as key co- or post-transcriptional regulators of several genes related to vascular inflammation and atherosclerosis. In this review, we provide an overview of cell-specific function of RNA-binding proteins involved in all stages of ASCVD and how this knowledge may be used for the development of novel precision medicine therapeutics.

Role of Heterogeneous Nuclear Ribonucleoproteins in the Cancer-Immune Landscape

Cancer remains the second leading cause of death, accounting for approximately 20% of all fatalities. Evolving cancer cells and a dysregulated immune system create complex tumor environments that fuel tumor growth, metastasis, and resistance. Over the past decades, significant progress in deciphering cancer cell behavior and recognizing the immune system as a hallmark of tumorigenesis has been achieved. However, the underlying mechanisms controlling the evolving cancer-immune landscape remain mostly unexplored. Heterogeneous nuclear ribonuclear proteins (hnRNP), a highly conserved family of RNA-binding proteins, have vital roles in critical cellular processes, including transcription, post-transcriptional modifications, and translation. Dysregulation of hnRNP is a critical contributor to cancer development and resistance. HnRNP contribute to the diversity of tumor and immune-associated aberrant proteomes by controlling alternative splicing and translation. They can also promote cancer-associated gene expression by regulating transcription factors, binding to DNA directly, or promoting chromatin remodeling. HnRNP are emerging as newly recognized mRNA readers. Here, we review the roles of hnRNP as regulators of the cancer-immune landscape. Dissecting the molecular functions of hnRNP will provide a better understanding of cancer-immune biology and will impact the development of new approaches to control and treat cancer.

RNA methylation in vascular disease: a systematic review

Despite the rise in morbidity and mortality associated with vascular diseases, the underlying pathophysiological molecular mechanisms are still unclear. RNA N6-methyladenosine modification, as the most common cellular mechanism of RNA regulation, participates in a variety of biological functions and plays an important role in epigenetics. A large amount of evidence shows that RNA N6-methyladenosine modifications play a key role in the morbidity caused by vascular diseases. Further research on the relationship between RNA N6-methyladenosine modifications and vascular diseases is necessary to understand disease mechanisms at the gene level and to provide new tools for diagnosis and treatment. In this study, we summarize the currently available data on RNA N6-methyladenosine modifications in vascular diseases, addressing four aspects: the cellular regulatory system of N6-methyladenosine methylation, N6-methyladenosine modifications in risk factors for vascular disease, N6-methyladenosine modifications in vascular diseases, and techniques for the detection of N6-methyladenosine-methylated RNA.

Host-Directed Targeting of LincRNA-MIR99AHG Suppresses Intracellular Growth of Mycobacterium tuberculosis

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) kills 1.6 million people worldwide every year, and there is an urgent need for targeting host-pathogen interactions as a strategy to reduce mycobacterial resistance to current antimicrobials. Noncoding RNAs are emerging as important regulators of numerous biological processes and avenues for exploitation in host-directed therapeutics. Although long noncoding RNAs (lncRNAs) are abundantly expressed in immune cells, their functional role in gene regulation and bacterial infections remains understudied. In this study, we identify an immunoregulatory long intergenic noncoding RNA, lincRNA-MIR99AHG, which is upregulated in mouse and human macrophages upon IL-4/IL-13 stimulation and downregulated after clinical Mtb HN878 strain infection and in peripheral blood mononuclear cells from active TB patients. To evaluate the functional role of lincRNA-MIR99AHG, we used antisense locked nucleic acid (LNA) GapmeR-mediated antisense oligonucleotide (ASO) lncRNA knockdown experiments. Knockdown of lincRNA-MIR99AHG with ASOs significantly reduced intracellular Mtb growth in mouse and human macrophages and reduced pro-inflammatory cytokine production. In addition, in vivo treatment of mice with MIR99AHG ASOs reduced the mycobacterial burden in the lung and spleen. Furthermore, in macrophages, lincRNA-MIR99AHG is translocated to the nucleus and interacts with high affinity to hnRNPA2/B1 following IL-4/IL-13 stimulation and Mtb HN878 infection. Together, these findings identify lincRNA-MIR99AHG as a positive regulator of inflammation and macrophage polarization to promote Mtb growth and a possible target for adjunctive host-directed therapy against TB.

Exosomal Transfer of miR-185 Is Controlled by hnRNPA2B1 and Impairs Re-endothelialization After Vascular Injury

Dysfunction of endothelial cells (ECs) contributes to restenosis after vascular reconstruction for patients with coronary artery disease (CAD). The intercellular communication between ECs and vascular smooth muscle cells (VSMCs) might be critical in the development of restenosis and can be mediated by exosomes carrying functional microRNAs. miR-185 is reported to be associated with atherosclerosis, whether it plays a similar role in restenosis is unknown. In this study, we observed an elevated level of extracellular miR-185 in platelet-derived growth factor (PDGF)-stimulated VSMCs. The medium from PDGF-stimulated VSMCs promoted miR-185 expression in rat aortic ECs and inhibited EC angiogenesis. PDGF-stimulated VSMCs transferred miR-185 into ECs via exosomes. Furthermore, we found that the CXCL12 gene, a target of miR-185, is essential for the angiogenic potential of ECs. Exosomes derived from miR-185 mimic transfected VSMCs attenuated re-endothelialization after vascular injury. Moreover, we show that exosome-mediated miR-185 transfer is modulated by hnRNPA2B1. We also observed that hnRNPA2B1 is up-regulated during neointima formation and hnRNPA2B1 inhibition accelerates re-endothelialization and attenuates neointima formation following carotid injury. Taken together, our results indicate that exosomal miR-185 transfer from VSMCs to ECs is controlled by hnRNPA2B1 and impairs re-endothelialization after vascular injury.

RNA Modification by m6A Methylation in Cardiovascular Disease

Cardiovascular disease is currently the leading cause of death worldwide, and its underlying regulatory mechanisms remain largely unknown. N⁶-Methyladenosine (m⁶A) RNA methylation is an epigenetic modification involved in the splicing, nuclear export, translational regulation, and degradation of RNA. After the initial identification of m⁶A RNA methylation in 1974, the rise of next-generation sequencing technology to detect m⁶A throughout the transcriptome led to its renewed recognition in 2012. Since that time, m⁶A methylation has been extensively studied, and its functions, mechanisms, and effectors (e.g., METTL3, FTO, METTL14, WTAP, ALKBH5, and YTHDFs) in various diseases, including cardiovascular diseases, have rapidly been investigated. In this review, we first examine and summarize the molecular and cellular functions of m⁶A methylation and its readers, writers, and erasers in the cardiovascular system. Finally, we discuss future directions for m⁶A methylation research and the potential for therapeutic targeting of m⁶A modification in cardiovascular disease.

The RNA-binding protein QKI controls alternative splicing in vascular cells, producing an effective model for therapy

Dysfunction of endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) leads to ischaemia, the central pathology of cardiovascular disease. Stem cell technology will revolutionise regenerative medicine, but a need remains to understand key mechanisms of vascular differentiation. RNA-binding proteins have emerged as novel post-transcriptional regulators of alternative splicing and we have previously shown that the RNA-binding protein Quaking (QKI) plays roles in EC differentiation. In this study, we decipher the role of the alternative splicing isoform Quaking 6 (QKI-6) to induce VSMC differentiation from induced pluripotent stem cells (iPSCs). PDGF-BB stimulation induced QKI-6, which bound to HDAC7 intron 1 via the QKI-binding motif, promoting HDAC7 splicing and iPS-VSMC differentiation. Overexpression of QKI-6 transcriptionally activated SM22 (also known as TAGLN), while QKI-6 knockdown diminished differentiation capability. VSMCs overexpressing QKI-6 demonstrated greater contractile ability, and upon combination with iPS-ECs-overexpressing the alternative splicing isoform Quaking 5 (QKI-5), exhibited higher angiogenic potential in vivo than control cells alone. This study demonstrates that QKI-6 is critical for modulation of HDAC7 splicing, regulating phenotypically and functionally robust iPS-VSMCs. These findings also highlight that the QKI isoforms hold key roles in alternative splicing, giving rise to cells which can be used in vascular therapy or for disease modelling.This article has an associated First Person interview with the first author of the paper.

Functional roles of hnRNPA2/B1 regulated by METTL3 in mammalian embryonic development

Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2/B1) plays an important role in RNA processing via in m⁶A modification of pre-mRNA or pre-miRNA. However, the functional role of and relationship between m⁶A and hnRNPA2/B1 in early embryonic development are unclear. Here, we found that hnRNPA2/B1 is crucial for early embryonic development by virtue of regulating specific gene transcripts. HnRNPA2/B1 was localized to the nucleus and cytoplasm during subsequent embryonic development, starting at fertilization. Knockdown of hnRNPA2/B1 delayed embryonic development after the 4-cell stage and blocked further development. RNA-Seq analysis revealed changes in the global expression patterns of genes involved in transcription, translation, cell cycle, embryonic stem cell differentiation, and RNA methylation in hnRNPA2/B1 KD blastocysts. The levels of the inner cell mass markers OCT4 and SOX2 were decreased in hnRNPA2/B1 KD blastocysts, whereas that of the differentiation marker GATA4 was decreased. N6-Adenosine methyltransferase METTL3 knock-down caused embryonic developmental defects similar to those in hnRNPA2/B1 KD embryos. Moreover, METTL3 KD blastocysts showed increased mis-localization of hnRNPA2/B1 and decreased m⁶A RNA methylation. Taken together, our results suggest that hnRNPA2/B1 is essential for early embryogenesis through the regulation of transcription-related factors and determination of cell fate transition. Moreover, hnRNPA2/B1 is regulated by METTL3-dependent m⁶A RNA methylation.

Glycoprotein M6B Interacts with TβRI to Activate TGF-β-Smad2/3 Signaling and Promote Smooth Muscle Cell Differentiation

Smooth muscle cells (SMCs), which form the walls of blood vessels, play an important role in vascular development and the pathogenic process of vascular remodeling. However, the molecular mechanisms governing SMC differentiation remain poorly understood. Glycoprotein M6B (GPM6B) is a four-transmembrane protein that belongs to the proteolipid protein family and is widely expressed in neurons, oligodendrocytes, and astrocytes. Previous studies have revealed that GPM6B plays a role in neuronal differentiation, myelination, and osteoblast differentiation. In the present study, we found that the GPM6B gene and protein expression levels were significantly upregulated during transforming growth factor-β1 (TGF-β1)-induced SMC differentiation. The knockdown of GPM6B resulted in the downregulation of SMC-specific marker expression and repressed the activation of Smad2/3 signaling. Moreover, GPM6B regulates SMC Differentiation by Controlling TGF-β-Smad2/3 Signaling. Furthermore, we demonstrated that similar to p-Smad2/3, GPM6B was profoundly expressed and coexpressed with SMC differentiation markers in embryonic SMCs. Moreover, GPM6B can regulate the tightness between TβRI, TβRII, or Smad2/3 by directly binding to TβRI to activate Smad2/3 signaling during SMC differentiation, and activation of TGF-β-Smad2/3 signaling also facilitate the expression of GPM6B. Taken together, these findings demonstrate that GPM6B plays a crucial role in SMC differentiation and regulates SMC differentiation through the activation of TGF-β-Smad2/3 signaling via direct interactions with TβRI. This finding indicates that GPM6B is a potential target for deriving SMCs from stem cells in cardiovascular regenerative medicine. Stem Cells 2018 Stem Cells 2019;37:190-201.

Identification of long noncoding RNAs involved in muscle differentiation

Long noncoding RNAs (lncRNAs) are a large class of regulatory RNAs with diverse roles in cellular processes. Thousands of lncRNAs have been discovered; however, their roles in the regulation of muscle differentiation are unclear because no comprehensive analysis of lncRNAs during this process has been performed. In the present study, by combining diverse RNA sequencing datasets obtained from public database, we discovered lncRNAs that could behave as regulators in the differentiation of smooth or skeletal muscle cells. These analyses confirmed the roles of previously reported lncRNAs in this process. Moreover, we discovered dozens of novel lncRNAs whose expression patterns suggested their possible involvement in the phenotypic switch of vascular smooth muscle cells. The comparison of lncRNA expression change suggested that many lncRNAs have common roles during the differentiation of smooth and skeletal muscles, while some lncRNAs may have opposite roles in this process. The expression change of lncRNAs was highly correlated with that of their neighboring genes, suggesting that they may function as cis-acting lncRNAs. Furthermore, within the lncRNA sequences, there were binding sites for miRNAs with expression levels inversely correlated with the expression of corresponding lncRNAs during differentiation, suggesting a possible role of these lncRNAs as competing endogenous RNAs. The lncRNAs identified in this study will be a useful resource for future studies of gene regulation during muscle differentiation.

Differentiation and Application of Induced Pluripotent Stem Cell–Derived Vascular Smooth Muscle Cells

Vascular smooth muscle cells (VSMCs) play a role in the development of vascular disease, for example, neointimal formation, arterial aneurysm, and Marfan syndrome caused by genetic mutations in VSMCs, but little is known about the mechanisms of the disease process. Advances in induced pluripotent stem cell technology have now made it possible to derive VSMCs from several different somatic cells using a selection of protocols. As such, researchers have set out to delineate key signaling processes involved in triggering VSMC gene expression to grasp the extent of gene regulatory networks involved in phenotype commitment. This technology has also paved the way for investigations into diseases affecting VSMC behavior and function, which may be treatable once an identifiable culprit molecule or gene has been repaired. Moreover, induced pluripotent stem cell–derived VSMCs are also being considered for their use in tissue-engineered blood vessels as they may prove more beneficial than using autologous vessels. Finally, while several issues remains to be clarified before induced pluripotent stem cell–derived VSMCs can become used in regenerative medicine, they do offer both clinicians and researchers hope for both treating and understanding vascular disease. In this review, we aim to update the recent progress on VSMC generation from stem cells and the underlying molecular mechanisms of VSMC differentiation. We will also explore how the use of induced pluripotent stem cell–derived VSMCs has changed the game for regenerative medicine by offering new therapeutic avenues to clinicians, as well as providing researchers with a new platform for modeling of vascular disease.

Novel Pathological Role of hnRNPA1 (Heterogeneous Nuclear Ribonucleoprotein A1) in Vascular Smooth Muscle Cell Function and Neointima Hyperplasia

Supplemental Digital Content is available in the text.

Objective—

hnRNPA1 (heterogeneous nuclear ribonucleoprotein A1) plays a variety of roles in gene expression. However, little is known about the functional involvement of hnRNPA1 in vascular smooth muscle cell (VSMC) function and neointima hyperplasia. In this study, we have attempted to investigate the functional roles of hnRNPA1 in the contexts of VSMC function, injury-induced vessel remodeling, and human atherosclerotic lesions, as well as discern the molecular mechanisms involved.

Approach and Results—

hnRNPA1 expression levels were consistently modulated during VSMC phenotype switching and neointimal lesion formation induced by wire injury. Functional studies showed that VSMC-specific gene expression, proliferation, and migration were regulated by hnRNPA1. Our data show that hnRNPA1 exerts its effects on VSMC functions through modulation of IQGAP1 (IQ motif containing GTPase activating protein 1). Mechanistically, hnRNPA1 regulates IQGAP1 mRNA degradation through 2 mechanisms: upregulating microRNA-124 (miR-124) and binding to AU-rich element of IQGAP1 gene. Further evidence suggests that hnRNPA1 upregulates miR-124 by modulating miR-124 biogenesis and that IQGAP1 is the authentic target gene of miR-124. Importantly, ectopic overexpression of hnRNPA1 greatly reduced VSMC proliferation and inhibited neointima formation in wire-injured carotid arteries. Finally, lower expression levels of hnRNPA1 and miR-124, while higher expression levels of IQGAP1, were observed in human atherosclerotic lesions.

Conclusions—

Our data show that hnRNPA1 is a critical regulator of VSMC function and behavior in the context of neointima hyperplasia, and the hnRNPA1/miR-124/IQGAP1 regulatory axis represents a novel therapeutic target for the prevention of cardiovascular diseases.

MicroRNA-29a promotes smooth muscle cell differentiation from stem cells by targeting YY1

MicroRNA-29a (miR-29a) has been extensively studied in tumor biology and fibrotic diseases, but little is known about its functional roles in vascular smooth muscle cell (VSMC) differentiation from embryonic stem cells (ESCs). Using well-established VSMC differentiation models, we have observed that miR-29a induces VSMC differentiation from mouse ESCs by negatively regulating YY1, a transcription factor that inhibits muscle cell differentiation and muscle-specific gene expression. Moreover, gene expression levels of three VSMC specific transcriptional factors were up-regulated by miR-29a over-expression, but down-regulated by miR-29a inhibition or YY1 over-expression. Taken together, our data demonstrate that miR-29a and its target gene, YY1, play a regulatory role in VSMC differentiation from ESCs in vitro and in vivo.

Origin and differentiation of vascular smooth muscle cells

Vascular smooth muscle cells (SMCs), a major structural component of the vessel wall, not only play a key role in maintaining vascular structure but also perform various functions. During embryogenesis, SMC recruitment from their progenitors is an important step in the formation of the embryonic vascular system. SMCs in the arterial wall are mostly quiescent but can display a contractile phenotype in adults. Under pathophysiological conditions, i.e. vascular remodelling after endothelial dysfunction or damage, contractile SMCs found in the media switch to a secretory type, which will facilitate their ability to migrate to the intima and proliferate to contribute to neointimal lesions. However, recent evidence suggests that the mobilization and recruitment of abundant stem/progenitor cells present in the vessel wall are largely responsible for SMC accumulation in the intima during vascular remodelling such as neointimal hyperplasia and arteriosclerosis. Therefore, understanding the regulatory mechanisms that control SMC differentiation from vascular progenitors is essential for exploring therapeutic targets for potential clinical applications. In this article, we review the origin and differentiation of SMCs from stem/progenitor cells during cardiovascular development and in the adult, highlighting the environmental cues and signalling pathways that control phenotypic modulation within the vasculature.

MicroRNA-22 regulates smooth muscle cell differentiation from stem cells by targeting methyl CpG-binding protein 2

OBJECTIVE

In this study, we attempted to uncover the functional impact of microRNA-22 (miR-22) and its target gene in smooth muscle cell (SMC) differentiation and delineate the molecular mechanism involved.

APPROACH AND RESULTS

miR-22 was found to be significantly upregulated during SMC differentiation from embryonic stem cells and adventitia stem/progenitor cells. Enforced expression of miR-22 by its mimic, while knockdown of miR-22 by its antagomiR, promotes or inhibits SMC differentiation from embryonic stem cells and adventitia stem/progenitor cells, respectively. Expectedly, miR-22 overexpression in stem cells promoted SMC differentiation in vivo. Methyl CpG-binding protein 2 (MECP2) was predicted as one of the top targets of miR-22. Interestingly, the gene expression levels of MECP2 were significantly decreased during SMC differentiation, and MECP2 was dramatically decreased in miR-22 overexpressing cells but significantly increased when miR-22 was knockdown in the differentiating stem cells. Importantly, luciferase assay showed that miR-22 substantially inhibited wild-type, but not mutant MECP2-3' untranslated region-luciferase activity. In addition, modulation of MECP2 expression levels affects multiple SMC-specific gene expression in differentiated embryonic stem cells. Mechanistically, our data showed that MECP2 could transcriptionally repress SMC gene expression through modulating various SMC transcription factors, as well as several proven SMC differentiation regulators. Evidence also revealed that enrichment of H3K9 trimethylation around the promoter regions of the SMC differentiation regulators genes were significantly increased by MECP2 overexpression. Finally, miR-22 was upregulated by platelet-derived growth factor-BB and transforming growth factor-β through a transcriptional mechanism during SMC differentiation.

CONCLUSIONS

miR-22 plays an important role in SMC differentiation, and epigenetic regulation through MECP2 is required for miR-22 mediated SMC differentiation.

Heterogeneous nuclear ribonucleoprotein A2/B1 regulates the self-renewal and pluripotency of human embryonic stem cells via the control of the G1/S transition

Self-renewal and pluripotency of human embryonic stem cells (hESCs) are a complex biological process for maintaining hESC stemness. However, the molecular mechanisms underlying these special properties of hESCs are not fully understood. Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) is a multifunctional RNA-binding protein whose expression is related to cell proliferation and carcinogenesis. In this study, we found that hnRNP A2/B1 expression was localized to undifferentiated hESCs and decreased upon differentiation of hESCs. hnRNP A2/B1 knockdown reduced the number of alkaline phosphatase-positive colonies in hESCs and led to a decrease in the expression of pluripotency-associated transcription factors OCT4, NANOG, and SOX2, indicating that hnRNP A2/B1 is essential for hESC self-renewal and pluripotency. hnRNP A2/B1 knockdown increased the expression of gene markers associated with the early development of three germ layers, and promoted the process of epithelial-mesenchymal transition, suggesting that hnRNP A2/B1 is required for maintaining the undifferentiated and epithelial phenotypes of hESCs. hnRNP A2/B1 knockdown inhibited hESC proliferation and induced cell cycle arrest in the G0/G1 phase before differentiation via degradation of cyclin D1, cyclin E, and Cdc25A. hnRNP A2/B1 knockdown increased p27 expression and induced phosphorylation of p53 and Chk1, suggesting that hnRNP A2/B1 also regulates the G1/S transition of hESC cell cycle through the control of p27 expression and p53 and Chk1 activity. Analysis of signaling molecules further revealed that hnRNP A2/B1 regulated hESC proliferation in a PI3K/Akt-dependent manner. These findings provide for the first time mechanistic insights into how hnRNP A2/B1 regulates hESC self-renewal and pluripotency.

Significance of expression of Gstp and HnRNPA2/B1 in esophageal squamous cell carcinoma

AIM: To investigate the expression of Gstp and HnRNPA2/B1 in esophageal squamous cell carcinoma (ESCC) and to analyze their clinical significance.

METHODS: Immunohistochemical method was used to detect the expression of Gstp and HnRNPA2/B1 in 68 ESCC tissues and 48 normal esophageal tissues, and their correlations with the clinicopathologic characteristics of ESCC were analyzed.

RESULTS: The positive rates of Gstp and HnRNPA2/B1 expression were significantly higher in ESCC than in normal esophageal tissues (60.3% vs 27.1%, 54.4% vs 29.1%, P < 0.05). Gstp expression had no significant correlation with gender, age, ethnicity, tumor size or infiltration depth (P > 0.05), but was significantly correlated with tumor differentiation, lymph node metastasis and clinical stage (P < 0.05). HnRNPA2/B1 expression had no significant correlation with gender, age, national, tumor size or infiltration depth (P > 0.05), but was significantly correlated with tumor differentiation, lymph node metastasis and clinical stage (P < 0.05).

CONCLUSION: Gstp and HnRNPA2/B1 may play a role in the occurrence and development of ESCC. Gstp and HnRNPA2/B1 expression may be used to judge the malignant degree of ESCC.

Upregulated sirtuin 1 by miRNA-34a is required for smooth muscle cell differentiation from pluripotent stem cells

microRNA-34a (miR-34a) and sirtuin 1 (SirT1) have been extensively studied in tumour biology and longevity/aging, but little is known about their functional roles in smooth muscle cell (SMC) differentiation from pluripotent stem cells. Using well-established SMC differentiation models, we have demonstrated that miR-34a has an important role in SMC differentiation from murine and human embryonic stem cells. Surprisingly, deacetylase sirtuin 1 (SirT1), one of the top predicted targets, was positively regulated by miR-34a during SMC differentiation. Mechanistically, we demonstrated that miR-34a promoted differentiating stem cells' arrest at G0/G1 phase and observed a significantly decreased incorporation of miR-34a and SirT1 RNA into Ago2-RISC complex upon SMC differentiation. Importantly, we have identified SirT1 as a transcriptional activator in the regulation of SMC gene programme. Finally, our data showed that SirT1 modulated the enrichment of H3K9 tri-methylation around the SMC gene-promoter regions. Taken together, our data reveal a specific regulatory pathway that miR-34a positively regulates its target gene SirT1 in a cellular context-dependent and sequence-specific manner and suggest a functional role for this pathway in SMC differentiation from stem cells in vitro and in vivo.

Nucleotide sequences of an important functional gene hnRNPA2/B1 from Ailuropoda melanoleuca and Ursus thibetanus mupinensis and its potential value in phylogenetic study

The cDNA fragments of hnRNPA2/B1 were cloned from the giant panda and black bear using RT-PCR method, which were, respectively, 1029bp and 1026bp in length encoding 343 and 341 amino acids. Analysis indicated the cDNA cloned from the giant panda encoded variant B1 while the cDNA cloned from black bear encoded variant A2. Analyzing the hnRNPA2B1 peptide of the giant panda and black bear, 76 glycine residues and 86 glycine residues were, respectively, found, and moreover, most glycine are concentrated in the latter halves of the hnRNPA2B1 peptides. Functional sites prediction also showed many N-myristoylation sites existed in the glycine-rich domain, which is probably related to the role of telomere maintenance. From base bias and substitution analysis, we can conclude that the ORF of hnRNPA2/B1 biased G while hated C, and transition of the third site did not achieve the level of saturation. Orthology analysis indicated that both the nucleotide sequence and the deduced amino acid sequence showed high identity to other 26 hnRNPA2/B1 sequences from mammals and nonmammals reported. These sequences were used to construct phylogenetic trees employing the NJ method with 1000 bootstrap, and the obtained tree demonstrated similar topology with the classical systematics, which suggested the potential value of hnRNPA2/B1 in phylogenetic analysis. This report will be the first step to the study function of hnRNPA2/B1 in the giant panda and black bear, and will provide a scientific basis to disease surveillance, captive breeding, and conservation of the endangered species.

Novel role of hnRNP-A2/B1 in modulating aryl hydrocarbon receptor ligand sensitivity

The aryl hydrocarbon receptor (AHR) is responsible for susceptibility to its ligand-dependent responses. However, the effect of non-AHR factors is less clear. To explore the non-AHR factors, we used two mouse strains with different AHR genetic variants, namely C3H/lpr and MRL/lpr strains with Ala and Val as the 375th amino acid residue, respectively. To assess the contribution of AHR alone, COS-7 cells transiently expressing AHR from each strain were treated with 6-formylindolo[3,2-b]carbazole (FICZ) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and xenobiotic-responsive element (XRE)-driven reporter gene activities were measured. FICZ-EC50 values for the C3H/lpr and MRL/lpr AHR-mediated transactivation were 0.023 and 0.046 nM, respectively, indicating a similar susceptibility in both AHR genotypes. In contrast, C3H/lpr AHR was fourfold more sensitive to TCDD than MRL/lpr AHR. By a pull-down assay using a XRE-containing PCR product as bait and the hepatic nuclear extracts of both FICZ-treated mouse strains, we identified two interacting proteins as heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP-A2) and its splicing variant (hnRNP-A2b). Immunoprecipitation assays demonstrated the AHR interaction with hnRNP-A2/B1. When hnRNP-A2 was co-expressed with the MRL/lpr or C3H/lpr AHR in COS-7, FICZ treatment decreased EC50 to about threefold in both AHR genotypes, compared with EC50 in AHR alone. Similarly, hnRNP-A2b co-expression also lowered the FICZ-EC50 values. In TCDD-treated COS-7, responses depended on the AHR genotype; while no change in TCDD-EC50 was observed for C3H/lpr AHR when hnRNP-A2 was co-expressed, the value was reduced to nearly tenfold for MRL/lpr AHR. Co-transfection with hnRNP-A2b attenuated the AHR sensitivity to TCDD. In conclusion, the hnRNP-A2/B1 interacting with AHR may be a modulator of the AHR ligand sensitivity.

Effects of BMSCs interactions with adventitial fibroblasts in transdifferentiation and ultrastructure processes

In this study an in vitro model of simulated blood vessel injury was used to study the effects of bone marrow-derived mesenchymal stem cells (BMSCs) morphology and to detect vascular smooth muscle actin (SM α-actin) expression in the presence of adventitial fibroblasts. BMSCs from rats with DAPI-labeled nuclei were co-cultured with adventitial fibroblasts for 7 days, while BMSCs cultured alone served as controls. Cell morphology of BMSCs was assessed by laser confocal microscopy and SM α-actin or calponin expression in BMSCs was detected by immunofluorescence staining. The expression of SM α-actin mRNA was identified using RT-PCR. Cell ultrastructure was assessed by electron microscopy. The results demonstrate that BMSCs with DAPI-labeled nuclei were smaller compared with fibroblasts, and their nuclei emitted a blue fluorescence. Most BMSCs displayed a polygonal shape changing from their original long fusiform shape. BMSCs with blue nuclei and red cytoplasm (SM α-actin positive or calponin positive) were observed, and a substantial number of filaments were present in the cytoplasm as observed under electron microscopy. The number of these cells increased as a function of culture duration. However, SM α-actin expression was weak and calponin expression was not detected in the control group. This study provides important new information on the characterization of artherosclerosis pathogenesis and vascular restenosis after blood vessel injury. Our findings demonstrate that direct interactions with adventitial fibroblasts can induce vascular smooth muscle-like cell differentiation in BMSCs.

MicroRNA-200C and -150 play an important role in endothelial cell differentiation and vasculogenesis by targeting transcription repressor ZEB1

To investigate the role of miRNA in controlling human embryonic stem (hES) cell differentiation toward the endothelial lineage and chick embryonic blood vessel formation, undifferentiated hES cells were first cultured on Matrigel-coated flasks and in endothelial cell growth medium-2 (EGM-2) to initiate endothelial cell (EC) differentiation. CD146(+) cells were isolated from differentiating hES cells and expanded in vitro. The in vitro expanded CD146(+) cells were positive for EC markers, capable of Ac-LDL uptake, lectin binding, and the formation of vascular structures in vitro and in vivo. miRNA gain/loss-of-function analyses revealed that miR-150 and miR-200c were crucial in EC differentiation. Transcriptional repressor zinc finger E-box-binding homeobox 1 (ZEB1) was identified as the communal target gene of miRNA-200C and -150, and inhibition of ZEB1 was required for miRNA-200C or -150 mediated EC gene expressions. Moreover, we demonstrated that ZEB1 could transcriptionally repress EC gene expression through direct binding to promoters of EC genes. Finally, we also demonstrated that miRNA-200c and -150 played an important role in chick embryonic blood vessel formation by in vivo inhibition of miRNA-200C or -150 in developing chick embryos, and blocking ZEB1 signaling in CD146-positive cells could rescue the inhibitory effects of miR-200c inhibiton in in vivo vasculogenesis. Our findings revealed that miR-150 and miR-200c play an important role in human endothelial lineage specification and chick embryonic vasculogenesis by targeting ZEB1.

Functional involvements of heterogeneous nuclear ribonucleoprotein A1 in smooth muscle differentiation from stem cells in vitro and in vivo

To investigate the functional involvements of heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) in smooth muscle cell (SMC) differentiation from stem cells, embryonic stem cells were cultivated on collagen IV-coated plates to allow for SMC differentiation. We found that hnRNPA1 gene and protein expression was upregulated significantly during differentiation and coexpressed with SMC differentiation markers in the stem cell-derived SMCs as well as embryonic SMCs of 12.5 days of mouse embryos. hnRNPA1 knockdown resulted in downregulation of smooth muscle markers and transcription factors, while enforced expression of hnRNPA1 enhanced the expression of these genes. Importantly, knockdown of hnRNPA1 also resulted in impairment of SMC differentiation in vivo. Moreover, we demonstrated that hnRNPA1 could transcriptionally regulate SMC gene expression through direct binding to promoters of Acta2 and Tagln genes using luciferase and chromatin immunoprecipitation assays. We further demonstrated that the binding sites for serum response factor (SRF), a well-investigated SMC transcription factor, within the promoter region of the Acta2 and Tagln genes were responsible for hnRNPA1-mediated Acta2 and Tagln gene expression using in vitro site-specific mutagenesis and luciferase activity analyses. Finally, we also demonstrated that hnRNPA1 upregulated the expression of SRF, myocyte-specific enhancer factor 2c (MEF2c), and myocardin through transcriptional activation and direct binding to promoters of the SRF, MEF2c, and Myocd genes. Our findings demonstrated that hnRNPA1 plays a functional role in SMC differentiation from stem cells in vitro and in vivo. This indicates that hnRNPA1 is a potential modulating target for deriving SMCs from stem cells and cardiovascular regenerative medicine.

Proteomic changes in the base of chrysanthemum cuttings during adventitious root formation

Background

A lack of competence to form adventitious roots by cuttings of Chrysanthemum (Chrysanthemum morifolium) is an obstacle for the rapid fixation of elite genotypes. We performed a proteomic analysis of cutting bases of chrysanthemum cultivar ‘Jinba’ during adventitious root formation (ARF) in order to identify rooting ability associated protein and/or to get further insight into the molecular mechanisms controlling adventitious rooting.

Results

The protein profiles during ARF were analyzed by comparing the 2-DE gels between 0-day-old (just severed from the stock plant) and 5-day-old cutting bases of chrysanthemum. A total of 69 differentially accumulated protein spots (two-fold change; t-test: 95% significance) were excised and analyzed using MALDI-TOF/TOF, among which 42 protein spots (assigned as 24 types of proteins and 7 unknown proteins) were confidently identified using the NCBI database. The results demonstrated that 19% proteins were related to carbohydrate and energy metabolism, 16% to photosynthesis, 10% to protein fate, 7% to plant defense, 6% to cell structure, 7% to hormone related, 3% to nitrate metabolism, 3% to lipid metabolism, 3% to ascorbate biosynthesis and 3% to RNA binding, 23% were unknown proteins. Twenty types of differentially accumulated proteins including ACC oxidase (CmACO) were further analyzed at the transcription level, most of which were in accordance with the results of 2-DE. Moreover, the protein abundance changes of CmACO are supported by western blot experiments. Ethylene evolution was higher during the ARF compared with day 0 after cutting, while silver nitrate, an inhibitor of ethylene synthesis, pretreatment delayed the ARF. It suggested that ACC oxidase plays an important role in ARF of chrysanthemum.

Conclusions

The proteomic analysis of cutting bases of chrysanthemum allowed us to identify proteins whose expression was related to ARF. We identified auxin-induced protein PCNT115 and ACC oxidase positively or negatively correlated to ARF, respectively. Several other proteins related to carbohydrate and energy metabolism, protein degradation, photosynthetic and cell structure were also correlated to ARF. The induction of protein CmACO provide a strong case for ethylene as the immediate signal for ARF. This strongly suggests that the proteins we have identified will be valuable for further insight into the molecular mechanisms controlling ARF.

Adventitial stem cells in vein grafts display multilineage potential that contributes to neointimal formation

OBJECTIVE

This study was designed to carry out the characterization of stem cells within the adventitia and to elucidate their functional role in the pathogenesis of vein graft atherosclerosis.

APPROACH AND RESULTS

A mouse vein graft model was used to investigate the functional role of adventitial stem/progenitor cells on atherosclerosis. The adventitia of vein grafts underwent significant remodeling during early stages of vessel grafting and displayed markedly heterogeneous cell compositions. Immunofluorescence staining indicated a significant number of stem cell antigen-1-positive cells that were closely located to vasa vasorum. In vitro clonogenic assays demonstrated 1% to 11% of growing rates from adventitial cell cultures, most of which could be differentiated into smooth muscle cells (SMCs). These stem cell antigen-1-positive cells also displayed a potential to differentiate into adipogenic, osteogenic, or chondrogenic lineages in vitro. In light of the proatherogenic roles of SMCs in atherosclerosis, we focused on the functional roles of progenitor-SMC differentiation, in which we subsequently demonstrated that it was driven by direct interaction of the integrin/collagen IV axis. The ex vivo bioreactor system revealed the migratory capacity of stem cell antigen-1-positive progenitor cells into the vessel wall in response to stromal cell-derived factor-1. Stem cell antigen-1-positive cells that were applied to the outer layer of vein grafts showed enhanced atherosclerosis in apolipoprotein E-deficient mice, which contributed to ≈ 30% of neointimal SMCs.

CONCLUSIONS

We demonstrate that during pathological conditions in vein grafting, the adventitia harbors stem/progenitor cells that can actively participate in the pathogenesis of vascular disease via differentiation into SMCs.

Functions of heterogeneous nuclear ribonucleoproteins in stem cell potency and differentiation

Stem cells possess huge importance in developmental biology, disease modelling, cell replacement therapy, and tissue engineering in regenerative medicine because they have the remarkable potential for self-renewal and to differentiate into almost all the cell types in the human body. Elucidation of molecular mechanisms regulating stem cell potency and differentiation is essential and critical for extensive application. Heterogeneous nuclear ribonucleoproteins (hnRNPs) are modular proteins consisting of RNA-binding motifs and auxiliary domains characterized by extensive and divergent functions in nucleic acid metabolism. Multiple roles of hnRNPs in transcriptional and posttranscriptional regulation enable them to be effective gene expression regulators. More recent findings show that hnRNP proteins are crucial factors implicated in maintenance of stem cell self-renewal and pluripotency and cell differentiation. The hnRNPs interact with certain sequences in target gene promoter regions to initiate transcription. In addition, they recognize 3′UTR or 5′UTR of specific gene mRNA forming mRNP complex to regulate mRNA stability and translation. Both of these regulatory pathways lead to modulation of gene expression that is associated with stem cell proliferation, cell cycle control, pluripotency, and committed differentiation.

Reactive oxygen species in vascular formation and development

Reactive oxygen species (ROS) are derived from the metabolism of oxygen and are traditionally viewed as toxic byproducts that cause damage to biomolecules. It is now becoming widely acknowledged that ROS are key modulators in a variety of biological processes and pathological states. ROS mediate key signaling transduction pathways by reversible oxidation of certain signaling components and are involved in the signaling of growth factors, G-protein-coupled receptors, Notch, and Wnt and its downstream cascades including MAPK, JAK-STAT, NF-κB, and PI3K/AKT. Vascular formation and development is one of the most important events during embryogenesis and is vital for postnasal tissue repair. In this paper, we will discuss how ROS regulate different steps in vascular development, including smooth muscle cell differentiation, angiogenesis, endothelial progenitor cells recruitment, and vascular cell migration.

An updated view on stem cell differentiation into smooth muscle cells

Stem cells possess the ability of self-renewal and give rise to specific cell types. The differentiation of stem cells involves environmental factors, transduction of extra and intra-cellular signals, regulation of gene expression by transcriptional factors, microRNAs and chromosome structural modifiers. Vascular SMCs play a profound role in blood vessel physiology and participate in a number of cardiovascular diseases such as atherosclerosis, hypertension and restenosis. In addition, SMCs could be a crucial cell component for vascular tissue engineering. In this review, we aim to update the recent progress on the mechanisms of SMC differentiation from stem cells, which involve reactive oxygen species, epigenetic modifiers, transcription factors and microRNAs coordinately regulated during stem cell differentiation. We will also discuss the potential application of stem cell therapy for patients with cardiovascular diseases.

Nrf3-Pla2g7 interaction plays an essential role in smooth muscle differentiation from stem cells

OBJECTIVE

Phospholipase A2, group 7 (Pla2g7) is an important mediator in cardiovascular development and diseases because of its divergent physiological and pathological functions in inflammation and oxidative stress. However, little is known about the functional role of Pla2g7 in smooth muscle cell (SMC) differentiation from stem cells.

METHODS AND RESULTS

In the present study, embryonic stem cells were cultivated on collagen IV-coated plates to allow SMC differentiation. Pla2g7 gene expression and activity were upregulated significantly following 4 to 14 days of cell differentiation and colocalized with SMC differentiation markers in the differentiated SMCs. Knockdown of Pla2g7 resulted in downregulation of smooth muscle-specific markers in vitro and impairment of SMC differentiation in vivo, whereas enforced expression of Pla2g7 enhanced SMC differentiation and increased reactive oxygen species generation. Importantly, enforced expression of Pla2g7 significantly increased the binding of serum response factor to SMC differentiation gene promoters, resulting in SMC differentiation, which was abolished by free radical scavenger and flavoprotein inhibitor of NADPH oxidase but not hydrogen peroxide inhibitor. Moreover, we demonstrated that nuclear factor erythroid 2-related factor 3 (Nrf3) regulates Pla2g7 gene expression through direct binding to the promoter regions of Pla2g7 gene.

CONCLUSION

Our findings demonstrated that Pla2g7 plays a crucial physiological role in SMC differentiation from stem cells, and the fine interactions between Nrf3 and Pla2g7 are essential for SMC differentiation.