Sema4C participates in myogenic differentiation in vivo and in vitro through the p38 MAPK pathway

Single-Cell Mapping of Brain Myeloid Cell Subsets Reveals Key Transcriptomic Changes Favoring Neuroplasticity after Ischemic Stroke

Interactions between brain-resident and peripheral infiltrated immune cells are thought to contribute to neuroplasticity after cerebral ischemia. However, conventional bulk sequencing makes it challenging to depict this complex immune network. Using single-cell RNA sequencing, we mapped compositional and transcriptional features of peri-infarct immune cells. Microglia were the predominant cell type in the peri-infarct region, displaying a more diverse activation pattern than the typical pro- and anti-inflammatory state, with axon tract-associated microglia (ATMs) being associated with neuronal regeneration. Trajectory inference suggested that infiltrated monocyte-derived macrophages (MDMs) exhibited a gradual fate trajectory transition to activated MDMs. Inter-cellular crosstalk between MDMs and microglia orchestrated anti-inflammatory and repair-promoting microglia phenotypes and promoted post-stroke neurogenesis, with SOX2 and related Akt/CREB signaling as the underlying mechanisms. This description of the brain's immune landscape and its relationship with neurogenesis provides new insight into promoting neural repair by regulating neuroinflammatory responses.

Netrin-4 synthesized in satellite cell-derived myoblasts stimulates autonomous fusion

Satellite cells are indispensable for skeletal muscle regeneration and hypertrophy by forming nascent myofibers (myotubes). They synthesize multi-potent modulator netrins (secreted subtypes: netrin-1, -3, and -4), originally found as classical neural axon guidance molecules. While netrin-1 and -3 have key roles in myogenic differentiation, the physiological significance of netrin-4 is still unclear. This study examined whether netrin-4 regulates myofiber type commitment and myotube formation. Initially, the expression profiles indicated that satellite cells isolated from the extensor digitorum longus muscle (EDL muscle: fast-twitch myofiber-abundant) expressed slightly more netrin-4 than the soleus muscle (slow-type abundant) cells. As netrin-4 knockdown inhibited both slow- and fast-type myotube formation, netrin-4 may not directly regulate myofiber type commitment. However, netrin-4 knockdown in satellite cell-derived myoblasts reduced the myotube fusion index, while exogenous netrin-4 promoted myotube formation, even though netrin-4 expression level was maximum during the initiation stage of myogenic differentiation. Furthermore, netrin-4 knockdown also inhibited MyoD (a master transcriptional factor of myogenesis) and Myomixer (a myoblast fusogenic molecule) expression. These data suggest that satellite cells synthesize netrin-4 during myogenic differentiation initiation to promote their own fusion, stimulating the MyoD-Myomixer signaling axis.

Skeletal Muscle Regeneration in Cardiotoxin-Induced Muscle Injury Models

Skeletal muscle injuries occur frequently in daily life and exercise. Understanding the mechanisms of regeneration is critical for accelerating the repair and regeneration of muscle. Therefore, this article reviews knowledge on the mechanisms of skeletal muscle regeneration after cardiotoxin-induced injury. The process of regeneration is similar in different mouse strains and is inhibited by aging, obesity, and diabetes. Exercise, microcurrent electrical neuromuscular stimulation, and mechanical loading improve regeneration. The mechanisms of regeneration are complex and strain-dependent, and changes in functional proteins involved in the processes of necrotic fiber debris clearance, M1 to M2 macrophage conversion, SC activation, myoblast proliferation, differentiation and fusion, and fibrosis and calcification influence the final outcome of the regenerative activity.

Cross-regulation between microRNAs and key proteins of signaling pathways in hepatocellular carcinoma

INTRODUCTION

Hepatocellular carcinoma (HCC) is a subtype of primary liver cancer and a major cause of death. Although miRNA plays an important role in hepatocellular carcinoma, the specific regulatory network remains unclear. Therefore, this paper comprehensively describes the miRNA-related signaling pathways in HCC and the possible interactions among different signaling pathways. The aim is to lay the foundation for the discovery of new molecular targets and multi-target therapy.

AREAS COVERED

Based on miRNA, HCC, and signaling pathways, the literature was searched on Web of Science and PubMed. Then, common targets between different signaling pathways were found from KEGG database, and possible cross-regulation mechanisms were further studied. In this review, we elaborated from two aspects, respectively, laying a foundation for studying the regulatory mechanism and potential targets of miRNA in HCC.

EXPERT OPINION

Non-coding RNAs have become notable molecules in cancer research in recent years, and many types of targeted drugs have emerged. From the outset, molecular targets and signal pathways are interlinked, which suggests that signal pathways and regulatory networks should be concerned in basic research, which also provides a strong direction for future mechanism research.

The circular RNA circNlgnmediates doxorubicin-inducedcardiac remodeling and fibrosis

Doxorubicin is a chemotherapeutic medication commonly used to treat many types of cancers, but it has side effects including vomiting, rash, hair loss, and bone marrow suppression. The most dangerous side effects are cardiomyopathy, cardiofibrosis, and heart failure, as doxorubicin generates cytotoxicity and stops DNA replication. There is no treatment to block these side effects. We have developed a transgenic mouse line overexpressing the circular RNA circNlgn and shown that circNlgn is a mediator of doxorubicin-induced cardiofibrosis. Increased expression of circNlgn decreased cardiac function and induced cardiofibrosis by upregulating Gadd45b, Sema4C, and RAD50 and activating p38 and pJNK in circNlgn transgenic heart. Silencing circNlgn decreased the effects of doxorubicin on cardiac cell activities and prevented doxorubicin-induced expression of fibrosis-associated molecules. The protein (Nlgn173) translated by circNlgn could bind and activate H2AX, producing γH2AX, resulting in upregulation of IL-1b, IL-2Rb, IL-6, EGR1, and EGR3. We showed that silencing these molecules in the signaling pathway prevented doxorubicin-induced cardiomyocyte apoptosis, increased cardiomyocyte viability, decreased cardiac fibroblast proliferation, and inhibited collagen production. This mechanism may hold therapeutic implications for mitigating the side effects of doxorubicin therapy in cancer patients.

Sema4C modulates the migration of primary tumor-associated lymphatic endothelial cells via an ERK-mediated pathway

Although lymphatic endothelial cells (LECs) serve a positive role in tumor lymphatic metastasis, the regulation of LECs undergoing migration similar to that of tumor cells remains poorly understood. A previous study revealed that semaphorin 4C (Sema4C) could be a marker of LECs in cervical cancer. Thus, the present study aimed to understand the mechanism via which Sema4C could promote the development of tumor-associated characteristics in LECs in cervical cancer. Primary tumor-associated LECs (TLECs) were distinguished from cervical cancer by flow cytometry. The promigratory ability was assessed using the Transwell assay. Lentivirus infection was used to alter the expression of Sema4C in TLECs. Confocal laser scanning was used to determine the infection efficiency of lentivirus infection. Sema4C/ERK/E-cadherin pathway was measured by reverse transcription-quantitative PCR and western blotting. The co-localization of Sema4C and the lymphatic marker lymphatic vessel endothelial hyaluronan receptor 1 was verified. Primary tumor-associated LECs (TLECs) were isolated from a mouse xenograft cervical tumor model. It was revealed that overexpressing Sema4C stimulated the migratory ability of TLECs, downregulated E-cadherin expression and stimulated ERK phosphorylation, whereas knocking down Sema4C had the opposite effects. The treatment of PD98059 (ERK inhibitor) blocked the pro-migratory ability of TLECs, which indicated a dependence on the ERK signaling pathway. It was identified that the Sema4C/ERK/E-cadherin pathway may be critical for the migration of TLECs, which may promote lymph node metastasis. Therefore, Sema4C could be a promising target for the treatment of cervical cancer with lymphatic metastasis.

miR-642 serves as a tumor suppressor in hepatocellular carcinoma by regulating SEMA4C and p38 MAPK signaling pathway

Hepatocellular carcinoma (HCC) is a malignant tumor with high incidence and high risk. Study of the role and mechanism of miRNAs are a hot spot of research providing new treatment ideas in malignant tumors. The effect of miR-642a on HCC progression and the underlying molecular mechanism were investigated. Expression of miR-642a and SEMA4C was measured by western blot analysis and RT-PCR. miR-642a expression was elevated while SEMA4C expression was attenuated in HCC tissues and cells. Results of luciferase reporter and western blot analyses show that miR-642a modulated SEMA4C expression by binding to its 3′UTR. Moreover, miR-642a negatively regulated SEMA4C expression. HCC cell migration and invasion was tested by Transwell assays. The findings revealed that the number of migrated and invaded cells were reduced by miR-642a mimic and raised by miR-642a inhibitor, indicating that miR-642a showed a suppression effect on HCC cell migration and invasion. Additionally, the migration and invasion of HCC cells were inhibited by SEMA4C siRNA, and SEMA4C reversed miR-642a effect on HCC migration and invasion. Furthermore, p38 MAPK signaling pathway was proven to be inhibited by miR-642a mimic, whereas facilitated by miR-642a inhibitor and SEMA4C siRNA could overturn the promotion effect of miR-642a inhibitor. Briefly, miR-642a targeted SEMA4C to repress HCC cell migration and invasion through p38 MAPK signaling pathway providing a new strategy for treatment of HCC patients.

Downregulation of SEMA4C Inhibit Epithelial-Mesenchymal Transition (EMT) and the Invasion and Metastasis of Cervical Cancer Cells via Inhibiting Transforming Growth Factor-beta 1 (TGF-β1)-Induced Hela cells p38 Mitogen-Activated Protein Kinase (MAPK) Activation

BACKGROUND Epithelial-mesenchymal transition (EMT) plays a key role in promoting invasion and metastasis of tumor cells. SEMA4C can regulate the generation of transforming growth factor-beta 1 (TGF-ß1)-induced EMT in cervical cancer. This study investigated the relationship between the regulation of SEMA4C on TGF-ß1-induced p38 mitogen-activated protein kinase (MAPK) activation and invasion and metastasis of cervical cancer. MATERIAL AND METHODS Hela-shSEMA4C cell line was established and the success of transfection was confirmed with fluorescence intensity. Cell experiments were divided into 2 groups. Group 1 was Hela, Hela-shNC, and Hela-shSEMA4C; and Group 2 was Hela, Hela-shNC, Hela-shSEMA4C, Hela+TGF-ß1, Hela-shNC+TGF-ß1, and Hela-shSEMA4C+TGF-ß1. Group 1 was detected for SEMA4C mRNA expression by real-time polymerase chain reaction (RT-PCR), cell viability by Cell Counting Kit-8 (CCK-8), F-actin fluorescence intensity by immunofluorescence, cell migration by scratch test, and cell invasion by invasion test. Group 2 was analyzed for E-cadherin fluorescence intensity by immunofluorescence, human fibronectin (FN) content by enzyme-linked immunosorbent assay (ELISA), and SEMA4C, E-cadherin and p-p38 expressions by Western blot. RESULTS For Group 1, compared with Hela and Hela-shNC subgroups, the SEMA4C mRNA expression, cell viability, F-actin fluorescence intensity, cell migration and invasion ability in the Hela-shSEMA4C subgroup were significantly decreased (P<0.05). For Group 2, compared with Hela and Hela-shNC subgroups, the E-cadherin expression and fluorescence intensity in the Hela-shSEMA4C subgroup were significantly increased (P<0.01), while the FN content, SEMA4C, and p-p38 MAPK expressions were significantly decreased (P<0.01). Compared with Hela-shNC+TGF-ß1 and Hela+TGF-ß1 subgroups, the E-cadherin expression and fluorescence intensity in the Hela-shSEMA4C+TGF-ß1 subgroup were significantly increased (P<0.01), while the FN content, SEMA4C and p-p38 expressions were significantly decreased (P<0.01). CONCLUSIONS Downregulation of SEMA4C can inhibit EMT and the invasion and metastasis of cervical cancer cells via inhibiting TGF-ß1-induced Hela cells p38 MAPK activation.

Semaphorin 4C Promotes Macrophage Recruitment and Angiogenesis in Breast Cancer

Semaphorins are a large family of evolutionarily conserved morphogenetic molecules that are associated with repelling axonal guidance. Intriguingly, recent researches indicate that semaphorins are involved in cancer progression. Semaphorin 4C (SEMA4C) has long been considered a neuronal migration gene, but we detected that it is also highly expressed in many malignant human cancers. During an investigation of subcutaneous tumor models, we found that SEMA4C expression promoted tumor growth and progression. We discovered that SEMA4C was involved in maintaining tumor cell self-renewal, likely by regulating the p53 pathway. Inhibiting the expression of endogenous SEMA4C in tumor cells impaired growth and induced senescence and cell-cycle arrest in the G₂-phase. In addition, we found that SEMA4C induced the production of angiogenin and colony-stimulating factor-1 (CSF-1) in tumor cells by activating the NF-κB pathway in a plexinB2-dependent manner. In conclusion, SEMA4C expression in breast cancer cells promotes cancer cell proliferation, macrophage recruitment, and angiogenesis. Thus, inhibition of SEMA4C activity may be a novel therapeutic strategy for human breast cancer. IMPLICATIONS: In breast cancer, therapeutic targeting of the SEMA4C pathway may prevent tumor growth, angiogenesis, metastasis, and progression.

Genomic imbalances defining novel intellectual disability associated loci

Background

High resolution genome-wide copy number analysis, routinely used in clinical diagnosis for several years, retrieves new and extremely rare copy number variations (CNVs) that provide novel candidate genes contributing to disease etiology. The aim of this work was to identify novel genetic causes of neurodevelopmental disease, inferred from CNVs detected by array comparative hybridization (aCGH), in a cohort of 325 Portuguese patients with intellectual disability (ID).

Results

We have detected CNVs in 30.1% of the patients, of which 5.2% corresponded to novel likely pathogenic CNVs. For these 11 rare CNVs (which encompass novel ID candidate genes), we identified those most likely to be relevant, and established genotype-phenotype correlations based on detailed clinical assessment. In the case of duplications, we performed expression analysis to assess the impact of the rearrangement. Interestingly, these novel candidate genes belong to known ID-related pathways. Within the 8% of patients with CNVs in known pathogenic loci, the majority had a clinical presentation fitting the phenotype(s) described in the literature, with a few interesting exceptions that are discussed.

Conclusions

Identification of such rare CNVs (some of which reported for the first time in ID patients/families) contributes to our understanding of the etiology of ID and for the ever-improving diagnosis of this group of patients.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1135-0) contains supplementary material, which is available to authorized users.

Lrrc75b is a novel negative regulator of C2C12 myogenic differentiation

Many transcription factors and signaling molecules involved in the guidance of myogenic differentiation have been investigated in previous studies. However, the precise molecular mechanisms of myogenic differentiation remain largely unknown. In the present study, by performing a meta-analysis of C2C12 myogenic differentiation microarray data, we found that leucine-rich repeat-containing 75B (Lrrc75b), also known as AI646023, a molecule of unknown biological function, was downregulated during C2C12 myogenic differentiation. The knockdown of Lrrc75b using specific siRNA in C2C12 myoblasts markedly enhanced the expression of muscle-specific myogenin and increased myoblast fusion and the myotube diameter. By contrast, the adenovirus-mediated overexpression of Lrrc75b in C2C12 cells markedly inhibited myoblast differentiation accompanied by a decrease in myogenin expression. In addition, the phosphorylation of extracellular signal-regulated kinase 1/2 (Erk1/2) was suppressed in the cells in which Lrrc75b was silenced. Taken together, our results demonstrate that Lrrc75b is a novel suppressor of C2C12 myogenic differentiation by modulating myogenin and Erk1/2 signaling.

The role of semaphorin3A in myogenic regeneration and the formation of functional neuromuscular junctions on new fibres

Current research on skeletal muscle injury and regeneration highlights the crucial role of nerve-muscle interaction in the restoration of innervation during that process. Activities of muscle satellite or stem cells, recognized as the 'currency' of myogenic repair, have a pivotal role in these events, as shown by ongoing research. More recent investigation of myogenic signalling events reveals intriguing roles for semaphorin3A (Sema3A), secreted by activated satellite cells, in the muscle environment during development and regeneration. For example, Sema3A makes important contributions to regulating the formation of blood vessels, balancing bone formation and bone remodelling, and inflammation, and was recently implicated in the establishment of fibre-type distribution through effects on myosin heavy chain gene expression. This review highlights the active or potential contributions of satellite-cell-derived Sema3A to regulation of the processes of motor neurite ingrowth into a regenerating muscle bed. Successful restoration of functional innervation during muscle repair is essential; this review emphasizes the integrative role of satellite-cell biology in the progressive coordination of adaptive cellular and tissue responses during the injury-repair process in voluntary muscle.

Genomewide association analysis for average birth interval and stillbirth in swine

Reproductive efficiency has a great impact on the economic success of pork production. Stillborn pigs and average birth interval contribute to the number of pigs born alive in a litter. To better understand the underlying genetics of these traits, a genomewide association study was undertaken. Samples of DNA were collected and tested using the Illumina Porcine SNP60 BeadChip from 798 females farrowing over a 4-yr period (all first parity). Birth intervals and piglet birth status (stillborn or alive) were determined by videotaping each farrowing event. A total of 41,148 SNP were tested using the Bayes C option of GenSel (version 4.61) and 1-Mb windows. These 1-Mb windows explained proportions of 0.017, 0.002, 0.032, 0.029, and 0.030 of the total variation, respectively, for litter average birth interval after deletion of the last piglet born, last birth interval in the litter, number of stillborn piglets ignoring the last piglet born, number of stillborns in the last birth position, and percent stillborn ignoring the last piglet. Significant 1-Mb nonoverlapping SNP windows were identified by using a conservative approach requiring 1-Mb windows to have a genetic variance ≥1.0% of genomic variance and these were considered to be QTL. Quantitative trait loci were located for number of stillborn piglets ignoring the last piglet born (1 QTL), number of stillborns in the last birth position (1 QTL), and percent stillborn ignoring the last piglet (3 QTL). In addition, 2, 13, 3, and 6 suggestive 1-Mb nonoverlapping SNP windows were identified for litter average birth interval after deletion of the last piglet born, number of stillborn piglets ignoring the last piglet born, number of stillborns in the last birth position, and percent stillborn ignoring the last piglet, respectively. Possible candidate genes affecting both birth interval and stillbirth included () and (). Possible genes affecting only birth interval included (), and (), and those affecting only stillbirth included (), LOC100518697 (a nostrin-like gene), and (). The QTL and the suggestive 1-Mb nonoverlapping SNP windows may lead to genetic markers for marker assisted selection, marker assisted management, or genomic selection applications in commercial pig populations.

Tumor Necrosis Factor Alpha and Insulin-Like Growth Factor 1 Induced Modifications of the Gene Expression Kinetics of Differentiating Skeletal Muscle Cells

Introduction

TNF-α levels are increased during muscle wasting and chronic muscle degeneration and regeneration processes, which are characteristic for primary muscle disorders. Pathologically increased TNF-α levels have a negative effect on muscle cell differentiation efficiency, while IGF1 can have a positive effect; therefore, we intended to elucidate the impact of TNF-α and IGF1 on gene expression during the early stages of skeletal muscle cell differentiation.

Methodology/Principal Findings

This study presents gene expression data of the murine skeletal muscle cells PMI28 during myogenic differentiation or differentiation with TNF-α or IGF1 exposure at 0 h, 4 h, 12 h, 24 h, and 72 h after induction. Our study detected significant coregulation of gene sets involved in myoblast differentiation or in the response to TNF-α. Gene expression data revealed a time- and treatment-dependent regulation of signaling pathways, which are prominent in myogenic differentiation. We identified enrichment of pathways, which have not been specifically linked to myoblast differentiation such as doublecortin-like kinase pathway associations as well as enrichment of specific semaphorin isoforms. Moreover to the best of our knowledge, this is the first description of a specific inverse regulation of the following genes in myoblast differentiation and response to TNF-α: Aknad1, Cmbl, Sepp1, Ndst4, Tecrl, Unc13c, Spats2l, Lix1, Csdc2, Cpa1, Parm1, Serpinb2, Aspn, Fibin, Slc40a1, Nrk, and Mybpc1. We identified a gene subset (Nfkbia, Nfkb2, Mmp9, Mef2c, Gpx, and Pgam2), which is robustly regulated by TNF-α across independent myogenic differentiation studies.

Conclusions

This is the largest dataset revealing the impact of TNF-α or IGF1 treatment on gene expression kinetics of early in vitro skeletal myoblast differentiation. We identified novel mRNAs, which have not yet been associated with skeletal muscle differentiation or response to TNF-α. Results of this study may facilitate the understanding of transcriptomic networks underlying inhibited muscle differentiation in inflammatory diseases.

MiR-138 inhibits cell proliferation and reverses epithelial-mesenchymal transition in non-small cell lung cancer cells by targeting GIT1 and SEMA4C

Non-small-cell lung cancer (NSCLC) is one of the most common and lethal malignant tumours worldwide with a poor 5-year survival rate. Recent studies indicated that miRNAs have been involved in the tumorigenic driver pathways in NSCLC, but the relevant molecular mechanisms are not well-understood. In this study, we investigated the biological functions and molecular mechanisms of miR-138 in human NSCLC. The effects of miR-138 on the NSCLC cell growth and epithelial-mesenchymal transition (EMT) were first examined. Then the targeting connections of miR-138 with G-protein-coupled receptor kinase-interacting protein 1 (GIT1) and semaphorin 4C (SEMA4C) were confirmed by dual luciferase reporter assays. Finally, the effects of GIT1 and SEMA4C on the NSCLC cell growth and EMT were investigated respectively. We found that the ectopic expression of miR-138 resulted in a significant inhibition of NSCLC growth and reversion of EMT. GIT1 and SEMA4C were identified as two novel targets of miR-138. Furthermore, GIT1 and SEMA4C knockdown inhibited the cell growth and reversed EMT, just like the effects of miR-138 overexpression on NSCLC cells, whereas ectopic expression of GIT1 and SEMA4C partly rescued the suppressive effects of miR-138 in NSCLC cells. These data represent a crucial step towards the understanding of the novel roles and molecular mechanism of miR-138, GIT1 and SEMA4C in NSCLC progression, which may provide some new targets or prognostic biomarkers for NSCLC treatment, thus having implications in translational oncology.

Adipocytokine expression associated with miRNA regulation and diagnosis of NASH in obese patients with NAFLD

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with visceral adiposity. The secretion of adipocytokines from white adipose tissue (WAT) promoting necroinflammation, and/or fibrosis may play important roles in the pathogenesis of non-alcoholic steatohepatits (NASH). In a previous study, reduced expression of a number of miRNA species in WAT concomitant with histological diagnosis of NASH was successfully demonstrated. In this study, we measure the expression of several predicted miRNA regulatory targets relevant to NAFLD and NASH including mTOR, FAS, IL20, SEMA4C, ADAMTS6 and IL13RA. We then examine hepatic receptor expression by immunohistochemical staining and qPCR.

METHODS

White adipose tissue was collected from 24 obese patients undergoing bariatric surgery with biopsy-proven NAFLD. Extracted total RNAs from the adipose tissue were reverse transcribed and profiled for gene expression by qPCR for specific individual mRNA targets defined after identification by any two of three of the major prediction services: miRanda, TarBase or PicTar. All liver biopsies were read by a singly hepatopathologist. The same liver tissue was used to stain for hepatic receptor expression for FASLG and IL20. Additionally, the same tissue was used for qPCR for FASLG and IL20.

RESULTS

Increases in the expression of IL13RA, mTOR, IL20, SEMA4C and FAS were detected and negatively correlated with putative regulatory miRNA. Hepatic receptor expression for FAS and IL20 was noted to correlate with markers of inflammation and severity of NAFLD.

CONCLUSION

These data are consistent with the hypothesis that specific adipocytokines secreted by WAT will impact hepatic tissue and participate in the pathogenesis of NASH.

Gene expression profiling of the hyperplastic growth zones of the late trout embryo myotome using laser capture microdissection and microarray analysis

Background

A unique feature of fish is that new muscle fibres continue to be produced throughout much of the life cycle; a process termed muscle hyperplasia. In trout, this process begins in the late embryo stage and occurs in both a discrete, continuous layer at the surface of the primary myotome (stratified hyperplasia) and between existing muscle fibres throughout the myotome (mosaic hyperplasia). In post-larval stages, muscle hyperplasia is only of the mosaic type and persists until 40% of the maximum body length is reached. To characterise the genetic basis of myotube neoformation in trout, we combined laser capture microdissection and microarray analysis to compare the transcriptome of hyperplastic regions of the late embryo myotome with that of adult myotomal muscle, which displays only limited hyperplasia.

Results

Gene expression was analysed using Agilent trout oligo microarrays. Our analysis identified more than 6800 transcripts that were significantly up-regulated in the superficial hyperplastic zones of the late embryonic myotome compared to adult myotomal muscle. In addition to Pax3, Pax7 and the fundamental myogenic basic helix-loop-helix regulators, we identified a large set of up-regulated transcriptional factors, including Myc paralogs, members of Hes family and many homeobox-containing transcriptional regulators. Other cell-autonomous regulators overexpressed in hyperplastic zones included a large set of cell surface proteins belonging to the Ig superfamily. Among the secreted molecules found to be overexpressed in hyperplastic areas, we noted growth factors as well as signalling molecules. A novel finding in our study is that many genes that regulate planar cell polarity (PCP) were overexpressed in superficial hyperplastic zones, suggesting that the PCP pathway is involved in the oriented elongation of the neofibres.

Conclusion

The results obtained in this study provide a valuable resource for further analysis of novel genes potentially involved in hyperplastic muscle growth in fish. Ultimately, this study could yield insights into particular genes, pathways or cellular processes that may stimulate muscle regeneration in other vertebrates.

The Roles of Mitogen-Activated Protein Kinase Pathways in TGF-β-Induced Epithelial-Mesenchymal Transition

The mitogen-activated protein kinase (MAPK) pathway allows cells to interpret external signals and respond appropriately, especially during the epithelial-mesenchymal transition (EMT). EMT is an important process during embryonic development, fibrosis, and tumor progression in which epithelial cells acquire mesenchymal, fibroblast-like properties and show reduced intercellular adhesion and increased motility. TGF-β signaling is the first pathway to be described as an inducer of EMT, and its relationship with the Smad family is already well characterized. Studies of four members of the MAPK family in different biological systems have shown that the MAPK and TGF-β signaling pathways interact with each other and have a synergistic effect on the secretion of additional growth factors and cytokines that in turn promote EMT. In this paper, we present background on the regulation and function of MAPKs and their cascades, highlight the mechanisms of MAPK crosstalk with TGF-β signaling, and discuss the roles of MAPKs in EMT.

Role of Sema4C in TGF-β1-induced mitogen-activated protein kinase activation and epithelial-mesenchymal transition in renal tubular epithelial cells

Background. The p38 mitogen-activated protein kinase (p38 MAPK) is an important intracellular signal transduction pathway involved in TGF-β1-induced epithelial–mesenchymal transition (EMT). Sema4C, a member of the semaphorin family, was found to be essential for the activation of p38 MAPK. However, the role of Sema4C in promoting TGF-β1-induced EMT is unclear.

Methods. Renal fibrosis was induced by 5/6 subtotal nephrectomy rat model. In vitro, Sema4C was induced in human proximal tubular epithelial cells (HKC) by treatment with TGF-β1, or was inhibited by siRNA or was over-expressed by Sema4C transfection. The selective p38 MAPK inhibitor, SB203580, was administered to inhibit the p38 pathway. The expression of Sema4C, the markers of EMT, p38 phosphorylation and fibronectin secretion were measured by western blotting, immunohistochemistry, immunocytochemistry or enzyme-linked immunosorbent assay.

Results. The expression of Sema4C increased in HKC cells that were treated with TGF-β1. Knockdown of Sema4C potently inhibited phosphorylation of p38 MAPK and reversed TGF-β1-induced EMT. Over-expression of Sema4C via Sema4C transfection elicited p38 MAPK phosphorylation and promoted EMT. The effects of Sema4C during EMT were blocked by a p38-specific inhibitor. In vivo, the expression of Sema4C increased in the tubular epithelia of 5/6-nephrectomized rats and human fibrotic renal tissue, and similar localization of phosphorylated p38 and Sema4C was demonstrated by immunohistochemistry on serial sections.

Conclusions. Our findings suggest that Sema4C plays an important role in TGF-β1-induced EMT through activation of p38 MAPK in proximal tubular epithelial cells.

Dynamics of the skeletal muscle secretome during myoblast differentiation

During recent years, increased efforts have focused on elucidating the secretory function of skeletal muscle. Through secreted molecules, skeletal muscle affects local muscle biology in an auto/paracrine manner as well as having systemic effects on other tissues. Here we used a quantitative proteomics platform to investigate the factors secreted during the differentiation of murine C2C12 skeletal muscle cells. Using triple encoding stable isotope labeling by amino acids in cell culture, we compared the secretomes at three different time points of muscle differentiation and followed the dynamics of protein secretion. We identified and quantitatively analyzed 635 secreted proteins, including 35 growth factors, 40 cytokines, and 36 metallopeptidases. The extensive presence of these proteins that can act as potent signaling mediators to other cells and tissues strongly highlights the important role of the skeletal muscle as a prominent secretory organ. In addition to previously reported molecules, we identified many secreted proteins that have not previously been shown to be released from skeletal muscle cells nor shown to be differentially released during the process of myogenesis. We found 188 of these secreted proteins to be significantly regulated during the process of myogenesis. Comparative analyses of selected secreted proteins revealed little correlation between their mRNA and protein levels, indicating pronounced regulation by posttranscriptional mechanisms. Furthermore, analyses of the intracellular levels of members of the semaphorin family and their corresponding secretion dynamics demonstrated that the release of secreted proteins is tightly regulated by the secretory pathway, the stability of the protein, and/or the processing of secreted proteins. Finally, we provide 299 unique hydroxyproline sites mapping to 48 distinct secreted proteins and have discovered a novel hydroxyproline motif.

A systematic expression analysis implicates Plexin-B2 and its ligand Sema4C in the regulation of the vascular and endocrine system

Plexins serve as receptors for semaphorins and play important roles in the developing nervous system. Plexin-B2 controls decisive developmental programs in the neural tube and cerebellum. However, whether Plexin-B2 also regulates biological functions in adult nonneuronal tissues is unknown. Here we show by two methodologically independent approaches that Plexin-B2 is expressed in discrete cell types of several nonneuronal tissues in the adult mouse. In the vasculature, Plexin-B2 is selectively expressed in functionally specialized endothelial cells. In endocrine organs, Plexin-B2 localizes to the pancreatic islets of Langerhans and to both cortex and medulla of the adrenal gland. Plexin-B2 expression is also detected in certain types of immune and epithelial cells. In addition, we report on a systematic comparison of the expression patterns of Plexin-B2 and its ligand Sema4C, which show complementarity or overlap in some but not all tissues. Furthermore, we demonstrate that Plexin-B2 and its family member Plexin-B1 display largely nonredundant expression patterns. This work establishes Plexin-B2 and Sema4C as potential regulators of the vascular and endocrine system and provides an anatomical basis to understand the biological functions of this ligand-receptor pair.

Sema4D/CD100 deficiency leads to superior performance in mouse motor behavior

BACKGROUND

Sema4D/CD100 is a type of class 4 semaphorin, exhibiting crucial roles in growth cone guidance in developing neurons. Sema4D is widely expressed throughout the central nervous system in embryonic mouse brain, and is selectively localized to oligodendrocytes and myelin in the postnatal brain. However, direct evidence of the actual involvement of Sema4D in the neuronal network development crucial for neurobehavioral performance is still lacking. The present study therefore examined whether Sema4D deficiency leads to abnormal behavioral development.

METHODS

Both wild-type and Sema4D-deficient mice were subjected to behavioral analyses including open-field, adhesive tape removal, rotarod tests and a water maze task.

RESULTS

Open-field tests revealed increased locomotor activity in Sema4D-deficient mice with less percentage of time spent in the center of the field. In both the adhesive tape removal and rotarod tests, which examine motor coordination and balance, Sema4D-deficient mice showed significantly superior performance, suggesting facilitated motor behavior. Both Sema4D-deficient and wild-type mice successfully learnt the water maze task, locating a hidden escape platform, and also showed precise memory for the platform position in probe tests. However, the swimming speed of Sema4D-deficient mice was significantly faster than that of wild-type mice, providing further evidence of their accelerated motor behavior.

CONCLUSION

Our mouse behavioral analyses revealed enhanced motor activity in Sema4D-deficient mice, suggesting the crucial involvement of Sema4D in the neurodevelopmental processes of the central structures mediating motor behavior in mice.

Cdo binds Abl to promote p38alpha/beta mitogen-activated protein kinase activity and myogenic differentiation

The p38 mitogen-activated protein kinase (MAPK) pathway is required for differentiation of skeletal myoblasts, but how the pathway is activated during this process is not well understood. One mechanism involves the cell surface receptor Cdo (also known as Cdon), which binds to Bnip-2 and JLP, scaffold proteins for Cdc42 and p38, respectively; formation of these complexes results in Bnip-2/Cdc42-dependent activation of p38. It has been reported that the tyrosine kinase Abl promotes myogenic differentiation in a manner dependent on its cytoplasmic localization, but the cytoplasmic signaling proteins with which it interacts to achieve this effect are unidentified. We report that Abl associates with both Cdo and JLP during myoblast differentiation. Abl binds a proline-rich motif in Cdo via its SH3 domain, and these regions of Abl and Cdo are required for their promyogenic effects. Cdo is important for full Abl kinase activity, and Abl is necessary for full activation of p38 MAPK, during myogenic differentiation. As seen with myoblasts depleted of Cdo, the diminished differentiation displayed by Abl-depleted cells is rescued by the expression of an activated form of the immediate upstream p38-activating kinase MAPK kinase 6. Abl's promyogenic effect is therefore linked to a multiprotein cell surface complex that regulates differentiation-dependent p38 activation.

Spherical self-organizing map as a helpful tool to identify category-specific cell surface markers

We analyzed gene expression profiles of five tumor cell lines (NB2a, NB41A3, C1300N18, BC3H1, and Neuro2a) derived from a category of nervous system using our originally developed cell surface marker DNA microarray in order to search for tumor-specific cell surface markers common to these cells. To visualize the expression patterns and to extract candidate genes of interest based on the expression profiles of several cell lines, we employed the clustering procedure of spherical self-organizing-map. As the result, three candidates of tumor-specific cell surface markers were picked up when the expression profiles were compared with that from normal brain tissue. RT-qPCR showed the expression of these genes was higher in tumor cells than in normal brain. Here we demonstrated the spherical self-organizing-map analysis should be useful to identify the candidates of cell surface markers common and specific to the group of cells or tissues of interest.

A Cdo-Bnip-2-Cdc42 signaling pathway regulates p38alpha/beta MAPK activity and myogenic differentiation

The p38α/β mitogen-activated protein kinase (MAPK) pathway promotes skeletal myogenesis, but the mechanisms by which it is activated during this process are unclear. During myoblast differentiation, the promyogenic cell surface receptor Cdo binds to the p38α/β pathway scaffold protein JLP and, via JLP, p38α/β itself. We report that Cdo also interacts with Bnip-2, a protein that binds the small guanosine triphosphatase (GTPase) Cdc42 and a negative regulator of Cdc42, Cdc42 GTPase-activating protein (GAP). Moreover, Bnip-2 and JLP are brought together through mutual interaction with Cdo. Gain- and loss-of-function experiments with myoblasts indicate that the Cdo–Bnip-2 interaction stimulates Cdc42 activity, which in turn promotes p38α/β activity and cell differentiation. These results reveal a previously unknown linkage between a cell surface receptor and downstream modulation of Cdc42 activity. Furthermore, interaction with multiple scaffold-type proteins is a distinctive mode of cell surface receptor signaling and provides one mechanism for specificity of p38α/β activation during cell differentiation.