Expression of Concern: TSHZ3 and SOX9 Regulate the Timing of Smooth Muscle Cell Differentiation in the Ureter by Reducing Myocardin Activity.
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SUBMITTER: PLOS ONE Editors
PROVIDER: S-EPMC6370214 | biostudies-literature | 2019
REPOSITORIES: biostudies-literature
Publications
Expression of Concern: TSHZ3 and SOX9 Regulate the Timing of Smooth Muscle Cell Differentiation in the Ureter by Reducing Myocardin Activity.
PloS one 20190211 2
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Project description:Smooth muscle cells are of key importance for the proper functioning of different visceral organs including those of the urogenital system. In the mouse ureter, the two transcriptional regulators TSHZ3 and SOX9 are independently required for initiation of smooth muscle differentiation from uncommitted mesenchymal precursor cells. However, it has remained unclear whether TSHZ3 and SOX9 act independently or as part of a larger regulatory network. Here, we set out to characterize the molecular function of TSHZ3 in the differentiation of the ureteric mesenchyme. Using a yeast-two-hybrid screen, we identified SOX9 as an interacting protein. We show that TSHZ3 also binds to the master regulator of the smooth muscle program, MYOCD, and displaces it from the coregulator SRF, thereby disrupting the activation of smooth muscle specific genes. We found that the initiation of the expression of smooth muscle specific genes in MYOCD-positive ureteric mesenchyme coincides with the down regulation of Sox9 expression, identifying SOX9 as a possible negative regulator of smooth muscle cell differentiation. To test this hypothesis, we prolonged the expression of Sox9 in the ureteric mesenchyme in vivo. We found that Sox9 does not affect Myocd expression but significantly reduces the expression of MYOCD/SRF-dependent smooth muscle genes, suggesting that down-regulation of Sox9 is a prerequisite for MYOCD activity. We propose that the dynamic expression of Sox9 and the interaction between TSHZ3, SOX9 and MYOCD provide a mechanism that regulates the pace of progression of the myogenic program in the ureter.
| S-EPMC3646048 | biostudies-literature
Project description:BackgroundChanges in the vascular smooth muscle cell (VSMC) contractile phenotype occur in pathological states such as restenosis and atherosclerosis. Multiple cytokines, signaling through receptor tyrosine kinases (RTK) and PI3K/Akt and MAPK/ERK pathways, regulate these phenotypic transitions. The Spry proteins are feedback modulators of RTK signaling, but their specific roles in VSMC have not been established.Methodology/principal findingsHere, we report for the first time that Spry1, but not Spry4, is required for maintaining the differentiated state of human VSMC in vitro. While Spry1 is a known MAPK/ERK inhibitor in many cell types, we found that Spry1 has little effect on MAPK/ERK signaling but increases and maintains Akt activation in VSMC. Sustained Akt signaling is required for VSMC marker expression in vitro, while ERK signaling negatively modulates Akt activation and VSMC marker gene expression. Spry4, which antagonizes both MAPK/ERK and Akt signaling, suppresses VSMC differentiation marker gene expression. We show using siRNA knockdown and ChIP assays that FoxO3a, a downstream target of PI3K/Akt signaling, represses myocardin promoter activity, and that Spry1 increases, while Spry4 decreases myocardin mRNA levels.ConclusionsTogether, these data indicate that Spry1 and Spry4 have opposing roles in VSMC phenotypic modulation, and Spry1 maintains the VSMC differentiation phenotype in vitro in part through an Akt/FoxO/myocardin pathway.
| S-EPMC3598808 | biostudies-literature
Project description:RationaleVascular smooth muscle cell (VSMC) differentiation from neural crest cells (NCCs) is critical for cardiovascular development, but the mechanisms remain largely unknown.ObjectiveTransforming growth factor-β (TGF-β) function in VSMC differentiation from NCCs is controversial. Therefore, we determined the role and mechanism of a TGF-β downstream signaling intermediate Smad2 in NCC differentiation to VSMCs.Methods and resultsBy using Cre/loxP system, we generated a NCC tissue-specific Smad2 knockout mouse model and found that Smad2 deletion resulted in defective NCC differentiation to VSMCs in aortic arch arteries during embryonic development and caused vessel wall abnormality in adult carotid arteries where the VSMCs are derived from NCCs. The abnormalities included 1 layer of VSMCs missing in the media of the arteries with distorted and thinner elastic lamina, leading to a thinner vessel wall compared with wild-type vessel. Mechanistically, Smad2 interacted with myocardin-related transcription factor B (MRTFB) to regulate VSMC marker gene expression. Smad2 was required for TGF-β-induced MRTFB nuclear translocation, whereas MRTFB enhanced Smad2 binding to VSMC marker promoter. Furthermore, we found that Smad2, but not Smad3, was a progenitor-specific transcription factor mediating TGF-β-induced VSMC differentiation from NCCs. Smad2 also seemed to be involved in determining the physiological differences between NCC-derived and mesoderm-derived VSMCs.ConclusionsSmad2 is an important factor in regulating progenitor-specific VSMC development and physiological differences between NCC-derived and mesoderm-derived VSMCs.
| S-EPMC3837448 | biostudies-literature
Project description:Yin Yang 1 (YY1) regulates gene transcription in a variety of biological processes. In this study, we aim to determine the role of YY1 in vascular smooth muscle cell (VSMC) phenotypic modulation both in vivo and in vitro. Here we show that vascular injury in rodent carotid arteries induces YY1 expression along with reduced expression of smooth muscle differentiation markers in the carotids. Consistent with this finding, YY1 expression is induced in differentiated VSMCs in response to serum stimulation. To determine the underlying molecular mechanisms, we found that YY1 suppresses the transcription of CArG box-dependent SMC-specific genes including SM22α, SMα-actin and SMMHC. Interestingly, YY1 suppresses the transcriptional activity of the SM22α promoter by hindering the binding of serum response factor (SRF) to the proximal CArG box. YY1 also suppresses the transcription and the transactivation of myocardin (MYOCD), a master regulator for SMC-specific gene transcription by binding to SRF to form the MYOCD/SRF/CArG box triad (known as the ternary complex). Mechanistically, YY1 directly interacts with MYOCD to competitively displace MYOCD from SRF. This is the first evidence showing that YY1 inhibits SMC differentiation by directly targeting MYOCD. These findings provide new mechanistic insights into the regulatory mechanisms that govern SMC phenotypic modulation in the pathogenesis of vascular diseases.
| S-EPMC7732823 | biostudies-literature
Project description:In ureter peristalsis, the orientation of the contracting smooth muscle cells is essential, yet current descriptions of orientation and composition of the smooth muscle layer in human as well as in rat ureter are inconsistent. The present study aims to improve quantification of smooth muscle orientation in rat ureters as a basis for mechanistic understanding of peristalsis. A crucial step in our approach is to use two-photon laser scanning microscopy and image analysis providing objective, quantitative data on smooth muscle cell orientation in intact ureters, avoiding the usual sectioning artifacts. In 36 rat ureter segments, originating from a proximal, middle or distal site and from a left or right ureter, we found close to the adventitia a well-defined longitudinal smooth muscle orientation. Towards the lamina propria, the orientation gradually became slightly more disperse, yet the main orientation remained longitudinal. We conclude that smooth muscle cell orientation in rat ureter is predominantly longitudinal, though the orientation gradually becomes more disperse towards the proprial side. These findings do not support identification of separate layers. The observed longitudinal orientation suggests that smooth muscle contraction would rather cause local shortening of the ureter, than cause luminal constriction. However, the net-like connective tissue of the ureter wall may translate local longitudinal shortening into co-local luminal constriction, facilitating peristalsis. Our quantitative, minimally invasive approach is a crucial step towards more mechanistic insight into ureter peristalsis, and may also be used to study smooth muscle cell orientation in other tube-like structures like gut and blood vessels.
| S-EPMC3897663 | biostudies-literature
Project description:ObjectiveAtherosclerosis, the cause of 50% of deaths in westernized societies, is widely regarded as a chronic vascular inflammatory disease. Vascular smooth muscle cell (VSMC) inflammatory activation in response to local proinflammatory stimuli contributes to disease progression and is a pervasive feature in developing atherosclerotic plaques. Therefore, it is of considerable therapeutic importance to identify mechanisms that regulate the VSMC inflammatory response.Approach and resultsWe report that myocardin, a powerful myogenic transcriptional coactivator, negatively regulates VSMC inflammatory activation and vascular disease. Myocardin levels are reduced during atherosclerosis, in association with phenotypic switching of smooth muscle cells. Myocardin deficiency accelerates atherogenesis in hypercholesterolemic apolipoprotein E(-/-) mice. Conversely, increased myocardin expression potently abrogates the induction of an array of inflammatory cytokines, chemokines, and adhesion molecules in VSMCs. Expression of myocardin in VSMCs reduces lipid uptake, macrophage interaction, chemotaxis, and macrophage-endothelial tethering in vitro, and attenuates monocyte accumulation within developing lesions in vivo. These results demonstrate that endogenous levels of myocardin are a critical regulator of vessel inflammation.ConclusionsWe propose myocardin as a guardian of the contractile, noninflammatory VSMC phenotype, with loss of myocardin representing a critical permissive step in the process of phenotypic transition and inflammatory activation, at the onset of vascular disease.
| S-EPMC4390125 | biostudies-literature
Project description:BackgroundMyocardin (Myocd) is a strong coactivator that binds the serum response factor (SRF) transcription factor over CArG elements embedded within smooth muscle cell (SMC) and cardiac muscle cyto-contractile genes. Here, we sought to ascertain whether Myocd-mediated gene expression confers a structural and physiological cardiac or SMC phenotype.Methods and resultsAdenoviral-mediated expression of Myocd in the BC(3)H1 cell line induces cardiac and SMC genes while suppressing both skeletal muscle markers and cell growth. Immunofluorescence microscopy shows that SRF and a SMC-like cyto-contractile apparatus are elevated with Myocd overexpression. A short hairpin RNA to Srf impairs BC(3)H1 cyto-architecture; however, cotransduction with Myocd results in complete restoration of the cyto-architecture. Electron microscopic studies demonstrate a SMC ultrastructural phenotype with no evidence for cardiac sarcomerogenesis. Biochemical and time-lapsed videomicroscopy assays reveal clear evidence for Myocd-induced SMC-like contraction.ConclusionsMyocd is sufficient for the establishment of a SMC-like contractile phenotype.
| S-EPMC2574857 | biostudies-literature
Project description:Skeletal and smooth muscle can mutually transdifferentiate, but little molecular insight exists as to how each muscle program may be subverted to the other. The myogenic basic helix-loop-helix transcription factors MyoD and myogenin (Myog) direct the development of skeletal muscle and are thought to be dominant over the program of smooth muscle cell (SMC) differentiation. Myocardin (Myocd) is a serum response factor (SRF) coactivator that promotes SMC differentiation through transcriptional stimulation of SRF-dependent smooth muscle genes. Here we show by lineage-tracing studies that Myocd is expressed transiently in skeletal muscle progenitor cells of the somite, and a majority of skeletal muscle is derived from Myocd-expressing cell lineages. However, rather than activating skeletal muscle-specific gene expression, Myocd functions as a transcriptional repressor of Myog, inhibiting skeletal muscle differentiation while activating SMC-specific genes. This repressor function of Myocd is complex, involving histone deacetylase 5 silencing of the Myog promoter and Myocd's physical contact with MyoD, which undermines MyoD DNA binding and transcriptional synergy with MEF2. These results reveal a previously unrecognized role for Myocd in repressing the skeletal muscle differentiation program and suggest that this transcriptional coregulator acts as a bifunctional molecular switch for the smooth versus skeletal muscle phenotypes.
| S-EPMC2034223 | biostudies-literature
Project description:Myocardin (Myocd) and Myocd-related transcription factors (MRTFs) are robust coactivators of serum response factor (SRF). RPEL motifs are monomeric globular actin (G-actin) binding elements that regulate MRTF localization and activity. However, the function of the RPEL motif in Myocd is largely unknown because of its low affinity for G-actin. Here, we demonstrated that the Myocd RPEL motif bound to actin-related protein 5 (Arp5) instead of conventional actin, resulting in a significant suppression of Myocd activity. In addition, Arp5 bound to a DNA binding domain of SRF via its C-terminal sequence and prevented the association of the Myocd-SRF complex with the promoter regions of smooth muscle genes. Well-differentiated smooth muscle cells mainly expressed a specific splicing variant of arp5; therefore, the protein level of Arp5 was markedly reduced by partial messenger RNA decay and translational suppression. In dedifferentiated smooth muscle cells, Arp5 knockdown restored the differentiated phenotype via Myocd activation. Thus, Arp5 is a key regulator of Myocd activity.
| S-EPMC3941051 | biostudies-literature
Project description:Vascular endothelial growth factor A (VEGF-A) is a pivotal player in angiogenesis. It is capable of influencing such cellular processes as tubulogenesis and vascular smooth muscle cell (VSMC) proliferation, yet very little is known about the actual signaling events that mediate VEGF-A induced VSMC phenotypic switch. In this report, we describe the identification of an intricate VEGF-A-induced signaling cascade that involves VEGFR2, STAT3, and Myocardin. We demonstrate that VEGF-A promotes VSMC proliferation via VEGFR2/STAT3-mediated upregulating the proliferation of markers like Cyclin D1 and PCNA. Specifically, VEGF-A leads to nitrosylation of Myocardin, weakens its effect on promoting the expression of contractile markers and is unable to inhibit the activation of STAT3. These observations reinforce the importance of nitric oxide and S-nitrosylation in angiogenesis and provide a mechanistic pathway for VEGF-A-induced VSMC phenotypic switch. In addition, Myocardin, GSNOR and GSNO can create a negative feedback loop to regulate the VSMC phenotypic switch. Thus, the discovery of this interactive network of signaling pathways provides novel and unexpected therapeutic targets for angiogenesis-dependent diseases.
| S-EPMC5453982 | biostudies-literature