Sox9 inhibits Wnt signaling by promoting beta-catenin phosphorylation in the nucleus

Exogenous Oestrogen Impacts Cell Fate Decision in the Developing Gonads: A Potential Cause of Declining Human Reproductive Health

The increasing incidence of testicular dysgenesis syndrome-related conditions and overall decline in human fertility has been linked to the prevalence of oestrogenic endocrine disrupting chemicals (EDCs) in the environment. Ectopic activation of oestrogen signalling by EDCs in the gonad can impact testis and ovary function and development. Oestrogen is the critical driver of ovarian differentiation in non-mammalian vertebrates, and in its absence a testis will form. In contrast, oestrogen is not required for mammalian ovarian differentiation, but it is essential for its maintenance, illustrating it is necessary for reinforcing ovarian fate. Interestingly, exposure of the bi-potential gonad to exogenous oestrogen can cause XY sex reversal in marsupials and this is mediated by the cytoplasmic retention of the testis-determining factor SOX9 (sex-determining region Y box transcription factor 9). Oestrogen can similarly suppress SOX9 and activate ovarian genes in both humans and mice, demonstrating it plays an essential role in all mammals in mediating gonad somatic cell fate. Here, we review the molecular control of gonad differentiation and explore the mechanisms through which exogenous oestrogen can influence somatic cell fate to disrupt gonad development and function. Understanding these mechanisms is essential for defining the effects of oestrogenic EDCs on the developing gonads and ultimately their impacts on human reproductive health.

Sox17 Promotes Oligodendrocyte Regeneration by Dual Modulation of Hedgehog and Wnt Signaling

Signaling pathways that promote oligodendrocyte development improve oligodendrocyte regeneration and myelin recovery from demyelinating pathologies. Sox factors critically control myelin gene expression and oligodendroglial fate, but little is known about signaling events underlying Sox-mediated oligodendroglial regeneration. In this study of the SoxF member Sox17, we demonstrate that Sox17-induced oligodendrocyte regeneration in adult myelin lesions occurs by suppressing lesion-induced Wnt/beta-catenin signaling which is inhibitory to oligodendrocyte regeneration and by increasing Sonic Hedgehog/Smoothened/Gli2 activity. Hedgehog signaling through Smoothened critically supports adult oligodendroglial viability and is an upstream regulator of beta-catenin. Gli2 ablation in adult oligodendrocyte progenitor cells indicates that Gli2 regulates beta-catenin differentially in wild-type and Sox17-overexpressing white matter. Myelin lesions in Sox17-deficient mice show beta-catenin hyperactivation, regenerative failure, and loss of oligodendrogenesis, despite exogenous Hedgehog stimulation. These studies indicate the benefit of Sox17 signaling targets to enhance oligodendrocyte regeneration after demyelination injury by modulating both Hedgehog and Wnt/beta-catenin signaling.

MicroRNA-27b targets CBFB to inhibit differentiation of human bone marrow mesenchymal stem cells into hypertrophic chondrocytes

Background

Human bone marrow-derived mesenchymal stem cells (hBMSCs) have chondrocyte differentiation potential and are considered to be a cell source for cell-transplantation-mediated repair of cartilage defects, including those associated with osteoarthritis (OA). However, chondrocyte hypertrophic differentiation is a major obstacle for the application of hBMSCs in articular cartilage defect treatment. We have previously shown that microRNA-27b (miR-27b) inhibits hypertrophy of chondrocytes from rat knee cartilage. In this study, we investigated the role of miR-27b in chondrocyte hypertrophic differentiation of hBMSCs.

Methods

Chondrogenic marker and microRNA expression in hBMSC chondrogenic pellets were evaluated using RT-qPCR and immunohistochemistry. The hBMSCs were transfected with miR-27b before inducing differentiation. Gene and protein expression levels were analyzed using RT-qPCR and western blot. Coimmunoprecipitation was used to confirm interaction between CBFB and RUNX2. Luciferase reporter assays were used to demonstrate that CBFB is a miR-27b target. Chondrogenic differentiation was evaluated in hBMSCs treated with shRNA targeting CBFB. Chondrogenic hBMSC pellets overexpressing miR-27b were implanted into cartilage lesions in model rats; therapeutic effects were assessed based on histology and immunohistochemistry.

Results

The hBMSCs showed typical MSC differentiation potentials. During chondrogenic differentiation, collagen 2 and 10 (COL2 and COL10), SOX9, and RUNX2 expression was upregulated. Expression of miR-140, miR-143, and miR-181a increased over time, whereas miR-27b and miR-221 were downregulated. Cartilage derived from hBMSC and overexpressing miR-27b exhibited higher expression of COL2 and SOX9, but lower expression of COL10, RUNX2, and CBFB than did the control cartilage. CBFB and RUNX2 formed a complex, and CBFB was identified as a novel miR-27b target. CBFB knockdown by shRNA during hBMSC chondrogenic differentiation led to significantly increased COL2 and SOX9 expression and decreased COL10 expression. Finally, miR-27b-overexpressing hBMSC chondrogenic pellets had better hyaline cartilage morphology and reduced expression of hypertrophic markers and tend to increase repair efficacy in vivo.

Conclusion

MiR-27b plays an important role in preventing hypertrophic chondrogenesis of hBMSCs by targeting CBFB and is essential for maintaining a hyaline cartilage state. This study provides new insights into the mechanism of hBMSC chondrocyte differentiation and will aid in the development of strategies for treating cartilage injury based on hBMSC transplantation.

Old Mice Have Less Transcriptional Activation But Similar Periosteal Cell Proliferation Compared to Young-Adult Mice in Response to in vivo Mechanical Loading

Mechanical loading is a potent strategy to induce bone formation, but with aging, the bone formation response to the same mechanical stimulus diminishes. Our main objectives were to (i) discover the potential transcriptional differences and (ii) compare the periosteal cell proliferation between tibias of young-adult and old mice in response to strain-matched mechanical loading. First, to discover potential age-related transcriptional differences, we performed RNA sequencing (RNA-seq) to compare the loading responses between tibias of young-adult (5-month) and old (22-month) C57BL/6N female mice following 1, 3, or 5 days of axial loading (loaded versus non-loaded). Compared to young-adult mice, old mice had less transcriptional activation following loading at each time point, as measured by the number of differentially expressed genes (DEGs) and the fold-changes of the DEGs. Old mice engaged fewer pathways and gene ontology (GO) processes, showing less activation of processes related to proliferation and differentiation. In tibias of young-adult mice, we observed prominent Wnt signaling, extracellular matrix (ECM), and neuronal responses, which were diminished with aging. Additionally, we identified several targets that may be effective in restoring the mechanoresponsiveness of aged bone, including nerve growth factor (NGF), Notum, prostaglandin signaling, Nell-1, and the AP-1 family. Second, to directly test the extent to which periosteal cell proliferation was diminished in old mice, we used bromodeoxyuridine (BrdU) in a separate cohort of mice to label cells that divided during the 5-day loading interval. Young-adult and old mice had an average of 15.5 and 16.7 BrdU+ surface cells/mm, respectively, suggesting that impaired proliferation in the first 5 days of loading does not explain the diminished bone formation response with aging. We conclude that old mice have diminished transcriptional activation following mechanical loading, but periosteal proliferation in the first 5 days of loading does not differ between tibias of young-adult and old mice. © 2020 American Society for Bone and Mineral Research.

A Recurrent Rare SOX9 Variant (M469V) is Associated with Congenital Vertebral Malformations

OBJECTIVE

The genetic variations contributed to a substantial proportion of congenital vertebral malformations (CVM). SOX9 gene, a member of the SOX gene family, has been implicated in CVM. To study the SOX9 mutation in CVM patients is of great significance to explain the pathogenesis of scoliosis (the clinical manifestation of CVM) and to explore the pathogenesis of SOX9-related skeletal deformities.

METHODS

A total of 50 singleton patients with CVM were included in this study. Exome Sequencing (ES) was performed on all the patients. The recurrent candidate variant of SOX9 gene was validated by Sanger sequencing. Luciferase assay was performed to investigate the functional changes of this variant.

RESULTS

A recurrent rare heterozygous missense variant in SOX9 gene (NM_000346.3: c.1405A>G, p.M469V) which had not been reported previously was identified in three CVM patients who had the clinical findings of congenital scoliosis without deformities in other systems. This variant was absent from our in-house database and it was predicted to be deleterious (CADD = 24.5). The luciferase assay demonstrated that transactivation capacity of the mutated SOX9 protein was significantly lower than that of the wild-type for the two luciferase reporters (p = 0.0202, p = 0.0082, respectively).

CONCLUSION

This SOX9 mutation (p.M469V) may contribute to CVM without other systematic deformity, which provides important implications and better understanding of phenotypic variability in SOX9-related skeletal deformities.

β-Catenin: oncogenic role and therapeutic target in cervical cancer

Cervical cancer is a common and fatal malignancy of the female reproductive system. Human papillomavirus (HPV) is the primary causal agent for cervical cancer, but HPV infection alone is insufficient to cause the disease. Actually, most HPV infections are sub-clinical and cleared spontaneously by the host immune system; very few persist and eventually develop into cervical cancer. Therefore, other host or environmental alterations could also contribute to the malignant phenotype. One of the candidate co-factors is the β-catenin protein, a pivotal component of the Wnt/β-catenin signaling pathway. β-Catenin mainly implicates two major cellular activities: cell–cell adhesion and signal transduction. Recent studies have indicated that an imbalance in the structural and signaling properties of β-catenin leads to various cancers, such as cervical cancer. In this review, we will systematically summarize the role of β-catenin in cervical cancer and provide new insights into therapeutic strategies.

Increased Expression of Sox9 during Balance of BMSCs/Chondrocyte Bricks in Platelet-Rich Plasma Promotes Construction of a Stable 3-D Chondrogenesis Microenvironment for BMSCs

Sox9 is an intrinsic transcription factor related to the determination and maintenance of chondrogenic lineage of bone marrow mesenchymal stem cells (BMSCs). In recent research, we have proved that fragmented chondrocyte aggregates (cell bricks) could promote chondrogenesis of BMSCs in vivo. However, it is still unknown whether the ratio of BMSCs/chondrocyte bricks has a significant influence on 3-D cartilage regeneration and related molecular mechanism. To address this issue, the current study subcutaneously injected three groups of cell complex with different rabbit BMSCs/chondrocyte bricks' ratios (1 : 2, 1 : 1, and 2 : 1) into nude mice. Gross morphology observation, histological and immunohistochemical assays, biochemical analysis, gene expression analysis, and western blot were used to compare the influence of different BMSCs/chondrocyte bricks' ratios on the properties of tissue-engineered cartilage and explore the related molecular mechanism. The constructs of 1 : 1 BMSCs/chondrocyte bricks, (B1CB1) group resulted in persistent chondrogenesis with appropriate morphology and adequate central nutritional perfusion without ossification. The related mechanism is that increased expression of Sox9 in the B1C1 group promoted chondrogenesis and inhibited the osteogenesis of BMSCs through upregulating Col-II as well as downregulating RUNX2 and downstream of Col-X and Col-I by upregulating Nkx3.2. This study demonstrated that BMSCs/chondrocyte bricks 1:1 should be a suitable ratio and the Sox9-Nkx3.2-RUNX2 pathway was a related mechanism which played an important role in the niche for stable chondrogenesis of BMSCs constructed by chondrocyte bricks and PRP.

Cell Survival Is Regulated via SOX9/BCL2L1 Axis in HCT-116 Colorectal Cancer Cell Line

Colorectal cancer (CRC) is one of the most frequent types of malignancies and one of the major causes of cancer-related death worldwide. Sex-determining region Y (SRY)-box 9 protein (SOX9) is a member of the SOX family of transcription factors which are involved in the regulation of differentiation and development. Recently, several reports suggest an important role of SOX9 in tumorigenesis since its overexpression correlates with tumor progression and poor outcome in several types of cancer; however, its role in CRC is not clear until now. Therefore, in this work, we searched for novel SOX9-regulated genes involved in cell survival of CRC. We silenced SOX9 in the poorly differentiated HCT-116 cell line, using a specific siRNA, to identify differential expressed genes by DNA microarrays and analyzed the role or candidate genes in apoptosis and autophagy. Transcriptome analysis showed that diverse cellular pathways, associated with CRC carcinogenesis such as Wnt/β-catenin, MAPK, TGF-β, and mTOR, were modulated after SOX9 silencing. Interestingly, we found that SOX9 silencing promotes downregulation of BCL2L1 and overexpression of CASP3, proteins related to apoptosis, which was further confirmed in SW-480, a moderated-differentiated cell line, but not in HT-29, well-differentiated cell line. Moreover, inhibition of BCL2L1 by ABT-737 (BH3 mimetic) in SOX9-silenced HCT-116 cells resulted in an increased apoptosis percentage. However, downregulation of BCL2L1 was not enough to induce autophagy. This is the first report, suggesting that cell survival in poorly and moderated-differentiated CRC cells lines is regulated by SOX9/BCL2L1 axis, but not in well-differentiated cell lines.

Detection of a 4 bp Mutation in the 3'UTR Region of Goat Sox9 Gene and Its Effect on the Growth Traits

Simple Summary

The sex determining region Y (SRY)-type high mobility group (HMG) box 9 (Sox9) gene is critically important in the formation and development of cartilage and is considered the “main regulator” of chondrogenesis. Additionally, a large number of studies have shown that mutations in a single allele of human Sox9 can lead to campomelic dysplasia syndrome. Therefore, the mutations of Sox9 have been the subject of increasing interest among researchers. However, no studies to date have examined the association between Sox9 gene variants and growth traits in goats. Here, we detected a 4 bp indel in the 3′Untranslated Regions (3′UTR) region of Sox9 in Shaanbei white cashmere (SBWC) goats (n = 1109) and studied the association between this indel and growth traits. The 4 bp indel of Sox9 was significantly associated with body length, heart girth, hip width, and all body measurement indexes (p < 0.05) in SBWC goats. Thus, this deletion could be used as an effective molecular marker for maximizing the growth traits of goats in breeding programs.

Abstract

The SRY-type HMG box 9 (Sox9) gene plays an important role in chondrocyte development as well as changes in hypertrophic chondrocytes, indicating that Sox9 can regulate growth in animals. However, no studies to date have examined the correlation between variations in Sox9 and growth traits in goats. Here, we found a 4 bp indel in the 3′UTR of Sox9 and verified its association with growth traits in Shaanbei white cashmere goats (n = 1109). The frequencies of two genotypes (ID and II) were 0.397 and 0.603, respectively, and polymorphic information content (PIC) values showed that the indel had a medium PIC (PIC > 0.25). The 4 bp indel was significantly correlated with body length (p = 0.006), heart girth (p = 0.001), and hip width (p = 4.37 × 10 ⁻⁴). Notably, individuals with the ID genotype had significantly superior phenotypic traits compared with individuals bearing the II genotype. Hence, we speculated that the 4 bp indel is an important mutation affecting growth traits in goat, and may serve as an effective DNA molecular marker for marker-assisted selection in goat breeding programs.

Animal mesenchymal stem cell research in cartilage regenerative medicine - a review

Healing of articular cartilage is a major clinical challenge as it also lacks a direct vasculature and nerves, and carries a limited number of resident chondrocytes that do not proliferate easily. Damaged articular cartilages are usually replaced by fibrocartilages, which are mechanically and structurally weaker and less resilient. Regenerative medicine involving stem cells is considered to have a definitive potential to overcome the limitations associated with the currently available surgical methods of cartilage repair. Among various stem cell types, mesenchymal stem cells (MSCs) are preferred for clinical applications. These cells can be readily derived from various sources and have the ability to trans-differentiate into various tissue-specific cells, including those of the cartilage by the process of chondrogenesis. Compared to embryonic or induced pluripotent stem cells (iPSCs), no ethical or teratogenic issues are associated with MSCs. These stem cells are being extensively evaluated for the treatment of joint affections and the results appear promising. Unlike human medicine, in veterinary medicine, the literature on stem cell research for cartilage regeneration is limited. This review, therefore, aims to comprehensively discuss the available literature and pinpoint the achievements and limitations associated with the use of MSCs for articular cartilage repair in animal species.

Role of the Wnt signaling pathway in keratoacanthoma

BACKGROUND

Keratoacanthoma (KA) has a unique life cycle of rapid growth and spontaneous regression that shows similarities to the hair follicle cycle, which involves an active Wnt signaling during physiological regeneration. We analyzed the expression of the Wnt signaling proteins β-catenin, Lef1, Sox9, and Cyclin D1 in young and old human KAs to investigate a possible role for Wnt signaling in KAs.

AIM

To investigate the role of the Wnt/β-catenin signaling pathway in human KAs.

METHODS AND RESULTS

Formalin-fixed, paraffin-embedded tissue samples of 67 KAs were analyzed for protein expression using immunohistochemistry. The majority of KAs were positive for Sox9 and Cyclin D1 but not for nuclear-localized β-catenin or Lef-1. No significant differences in protein expressions were seen between young and old KAs. However, we found a significant association between Ki67 and Cyclin D1 proteins (P= .008).

CONCLUSIONS

The Wnt signaling pathway does not appear to play a significant role in the biogenesis of human KA. Sox9 overexpression may be indicative of inhibition of Wnt signaling. Sox-9 and Cyclin D1 are proliferation markers that are most likely transactivated by alternate signaling pathways.

Understanding the Cellular and Molecular Mechanisms That Control Early Cell Fate Decisions During Appendicular Skeletogenesis

The formation of the vertebrate skeleton is orchestrated in time and space by a number of gene regulatory networks that specify and position all skeletal tissues. During embryonic development, bones have two distinct origins: bone tissue differentiates directly from mesenchymal progenitors, whereas most long bones arise from cartilaginous templates through a process known as endochondral ossification. Before endochondral bone development takes place, chondrocytes form a cartilage analgen that will be sequentially segmented to form joints; thus, in the cartilage template, either the cartilage maturation programme or the joint formation programme is activated. Once the cartilage differentiation programme starts, the growth plate begins to form. In contrast, when the joint formation programme is activated, a capsule begins to form that contains special articular cartilage and synovium to generate a functional joint. In this review, we will discuss the mechanisms controlling the earliest molecular events that regulate cell fate during skeletogenesis in long bones. We will explore the initial processes that lead to the recruitment of mesenchymal stem/progenitor cells, the commitment of chondrocyte lineages, and the formation of skeletal elements during morphogenesis. Thereafter, we will review the process of joint specification and joint morphogenesis. We will discuss the links between transcription factor activity, cell–cell interactions, cell–extracellular matrix interactions, growth factor signalling, and other molecular interactions that control mesenchymal stem/progenitor cell fate during embryonic skeletogenesis.

N-Cadherin Mimetic Peptide Nanofiber System Induces Chondrogenic Differentiation of Mesenchymal Stem Cells

Cadherins are vital for cell-to-cell interactions during tissue growth, migration, and differentiation processes. Both biophysical and biochemical inputs are generated upon cell-to-cell adhesions, which determine the fate of the mesenchymal stem cells (MSCs). The effect of cadherin interactions on the MSC differentiation still remains elusive. Here we combined the N-Cadherin mimetic peptide (HAV-PA) with the self-assembling E-PA and the resultant N-cadherin mimetic peptide nanofibers promoted chondrogenic differentiation of MSCs in conjunction with chondrogenic factors as a synthetic extracellular matrix system. Self-assembly of the precursor peptide amphiphile molecules HAV-PA and E-PA enable the organization of HAV peptide residues in close proximity to the cell interaction site, forming a supramolecular N-cadherin-like system. These bioactive peptide nanofibers not only promoted viability and enhanced adhesion of MSCs but also augmented the expression of cartilage specific matrix components compared to the nonbioactive control nanofibers. Overall, the N-cadherin mimetic peptide nanofiber system facilitated MSC commitment into the chondrogenic lineage presenting an alternative bioactive platform for stem-cell-based cartilage regeneration.

Deacetylation of β-catenin by SIRT1 regulates self-renewal and oncogenesis of liver cancer stem cells

Hepatocellular carcinoma (HCC) is a highly malignant liver tumor. The presence of cancer stem cells (CSCs) figures prominently in tumor invasion, therapeutic resistance and tumor recurrence resulting in poor outcome and limited therapeutic options. Wnt/β-catenin signaling is essential for cancer stem cell regulation and tumorigenesis in HCC, but its molecular mechanisms are not fully understood. Here, we demonstrate that β-catenin is overexpressed in liver CSCs, and its expression level is positively correlated with SIRT1 in HCC specimens. SIRT1 regulates the protein stability of β-catenin, thereby affecting the transcriptional activity of Wnt/β-catenin signaling in liver CSCs. Mechanistically, we show that nuclear accumulation of β-catenin results from deacetylation mediated by SIRT1. Further, nuclear β-catenin promotes the transcription of Nanog to help maintain self-renewal of liver CSCs. Taken together, our findings indicate that the deacetylation of β-catenin by SIRT1 represents a critical mechanism for regulating liver CSCs self-renewal and tumorigenesis. It provides an improved understanding of molecular mechanisms underlying β-catenin activation and tumorigenesis in HCC.

Expression and Clinical Relevance of SOX9 in Gastric Cancer

Gastric cancer is one of the most frequent tumours and the third leading cause of cancer-related death worldwide. The investigation of new biomarkers that can predict patient outcome more accurately and allow better treatment and follow-up decisions is of crucial importance. SOX9 (sex-determining region Y (SRY)-box 9) is a regulator of cell fate decisions in embryogenesis and adulthood. Here, we sought to ascertain the relevance of SOX9 transcription factor as a prognostic marker in gastric cancer. SOX9 expression was analyzed by immunohistochemistry in 333 gastric adenocarcinoma cases, and its association with clinicopathological and follow-up data was evaluated. SOX9 nuclear expression was absent in 17% of gastric cancer cases and predicted worse disease-free survival (P = 0.03). SOX9 expression was associated with lower risk of relapse in Cox univariable analysis (HR = 0.58; 95% CI = 0.35-0.97; P = 0.04). The prognostic value of SOX9 was more pronounced in tumours with expansive growth (P = 0.01) or with venous invasion (P = 0.02). Two validation cohorts from the Cancer Genome Atlas (TCGA) and the Asian Cancer Research Group (ACRG) confirmed that low SOX9 expression was significantly associated with poor patient outcome. In conclusion, we have identified SOX9 as a biomarker of disease relapse in gastric cancer patients. Further experiments are needed to elucidate its biological relevance at the cellular level.

A Second Career for Chondrocytes-Transformation into Osteoblasts

PURPOSE OF REVIEW

The goal of the review is to summarize the current knowledge on the process of chondrocyte-to-osteoblast transdifferentiation during endochondral bone formation and its potential implications in fracture healing and disease.

RECENT FINDINGS

Lineage tracing experiments confirmed the transdifferentiation of chondrocytes into osteoblasts. More recent studies lead to the discovery of molecules involved in this process, as well as to the hypothesis that these cells may re-enter a stem cell-like phase prior to their osteoblastic differentiation. This review recapitulates the current knowledge regarding chondrocyte transdifferentiating into osteoblasts, the developmental and postnatal events where transdifferentiation appears to be relevant, and the molecules implicated in this process.

SOX9 drives the epithelial-mesenchymal transition in non-small-cell lung cancer through the Wnt/β-catenin pathway

Background

The distant metastasis of cancer cells is a risk factor for tumor lethality and poor prognosis in non-small-cell lung carcinoma (NSCLC). Increased SOX9 expression has been associated with clinical stage and poor prognosis in NSCLC, but the molecular mechanisms by which SOX9 promotes metastasis in NSCLC are still unknown.

Methods

The relationship between SOX9 expression and T, N, M classification was assessed using the χ² test and Spearman’s analysis in 142 immunohistochemically diagnosed specimens of NSCLC. We also generated SOX9-overexpression and SOX9-knockdown cells lines and their corresponding control cell lines by transfection with lentiviral constructs. In vivo assay, SOX9-overexpressing and SOX9-knockdown NSCLC cells were injected in zebrafish to examine distance metastasis. Gene set enrichment analysis (GSEA) was applied to analysis the correlation between SOX9 overexpression and Wnt/β-catenin pathway. Luciferase assay was used to check transcriptional activity of TCF/LEF and western blot and immunofluorescence was employed to detect β-catenin translocation in SOX9-overexpression, SOX9-knockdown and their corresponding control cell lines.

Results

We found that SOX9 overexpression correlates with the T, N and M stage significantly (p = 0.03, 0.000, and 0.032 respectively) in 142 immunohistochemically diagnosed specimens of NSCLC. SOX9 overexpression was found to decrease the expression of the epithelial cell markers E-cadherin and γ-catenin and increase the expression of the mesenchymal cell markers N-cadherin and vimentin. An in vivo assay showed distant metastasis of the SOX9-overexpressing cells, which was not observed in the SOX9-knockdown cells. These findings indicate that SOX9 promotes distant metastasis by promoting EMT in NSCLC cells. GSEA showed that SOX9 overexpression was significantly correlated with the Wnt/β-catenin pathway which was corroborated by the expression of EMT-associated proteins in this pathway and its downstream target genes. SOX9 overexpression was also found to enhance the transcriptional activity of TCF/LEF, promote the nuclear translocation of β-catenin and increase the phosphorylation of GSK3β at Ser9. Further, inhibition of β-catenin suppressed the metastasis-promoting effects of SOX9 overexpression.

Conclusions

This study is the first to report that SOX9 is associated with clinical TNM stage and indicates that SOX9 promotes migration, invasion and the EMT process through the Wnt/β-catenin pathway.

Roles and regulation of SOX transcription factors in skeletogenesis

SOX transcription factors participate in the specification, differentiation and activities of many cell types in development and beyond. The 20 mammalian family members are distributed into eight groups based on sequence identity, and while co-expressed same-group proteins often have redundant functions, different-group proteins typically have distinct functions. More than a handful of SOX proteins have pivotal roles in skeletogenesis. Heterozygous mutations in their genes cause human diseases, in which skeletal dysmorphism is a major feature, such as campomelic dysplasia (SOX9), or a minor feature, such as LAMSHF syndrome (SOX5) and Coffin-Siris-like syndromes (SOX4 and SOX11). Loss- and gain-of-function experiments in animal models have revealed that SOX4 and SOX11 (SOXC group) promote skeletal progenitor survival and control skeleton patterning and growth; SOX8 (SOXE group) delays the differentiation of osteoblast progenitors; SOX9 (SOXE group) is essential for chondrocyte fate maintenance and differentiation, and works in cooperation with SOX5 and SOX6 (SOXD group) and other types of transcription factors. These and other SOX proteins have also been proposed, mainly through in vitro experiments, to have key roles in other aspects of skeletogenesis, such as SOX2 in osteoblast stem cell self-renewal. We here review current knowledge of well-established and proposed skeletogenic roles of SOX proteins, their transcriptional and non-transcriptional actions, and their modes of regulation at the gene, RNA and protein levels. We also discuss gaps in knowledge and directions for future research to further decipher mechanisms underlying skeletogenesis in health and diseases and identify treatment options for skeletal malformation and degeneration diseases.

GSK3β: a plausible mechanism of cognitive and hippocampal changes induced by erythropoietin treatment in mood disorders?

Mood disorders are associated with significant psychosocial and occupational disability. It is estimated that major depressive disorder (MDD) will become the second leading cause of disability worldwide by 2020. Existing pharmacological and psychological treatments are limited for targeting cognitive dysfunctions in mood disorders. However, growing evidence from human and animal studies has shown that treatment with erythropoietin (EPO) can improve cognitive function. A recent study involving EPO-treated patients with mood disorders showed that the neural basis for their cognitive improvements appeared to involve an increase in hippocampal volume. Molecular mechanisms underlying hippocampal changes have been proposed, including the activation of anti-apoptotic, antioxidant, pro-survival and anti-inflammatory signalling pathways. The aim of this review is to describe the potential importance of glycogen synthase kinase 3-beta (GSK3β) as a multi-potent molecular mechanism of EPO-induced hippocampal volume change in mood disorder patients. We first examine published associations between EPO administration, mood disorders, cognition and hippocampal volume. We then highlight evidence suggesting that GSK3β influences hippocampal volume in MDD patients, and how this could assist with targeting more precise treatments particularly for cognitive deficits in patients with mood disorders. We conclude by suggesting how this developing area of research can be further advanced, such as using pharmacogenetic studies of EPO treatment in patients with mood disorders.

Thermal Response of Epigenetic Genes Informs Turtle Sex Determination with and without Sex Chromosomes

Vertebrate sexual fate can be established by environmental cues (e.g., temperature-dependent sex determination, TSD) or by genetic content (genotypic sex determination, GSD). While methylation is implicated in TSD, the influence of broader epigenetic processes in sexual development remains obscure. Here, we investigated for the first time the embryonic gonadal expression of the genome-wide epigenetic machinery in turtles, including genes and noncoding RNAs (ncRNAs) involved in DNA/histone acetylation, methylation, ubiquitination, phosphorylation, and RNAi. This machinery was active and differentially thermosensitive in TSD versus GSD (ZZ/ZW) turtles. Methylation and histone acetylation genes responded the strongest. The results suggest these working hypotheses: (i) TSD might be mediated by epigenetically controlled hormonal pathways (via acetylation, methylation, and ncRNAs), or by (ii) hormonally controlled epigenetic processes, and (iii) key epigenetic events prior to the canonical thermosensitive period may explain differences between TSD and GSD. Novel epigenetic candidate regulators other than methylation were identified, including previously unknown ncRNAs that could potentially mediate gonadogenesis. These findings illuminate the molecular ecology of reptilian sex determination and permitted hypothesis building to help guide future functional studies on the epigenetic transduction of external cues in TSD versus GSD systems.

Origin of Reparative Stem Cells in Fracture Healing

PURPOSE OF REVIEW

The identity and functional roles of stem cell population(s) that contribute to fracture repair remains unclear. This review provides a brief history of mesenchymal stem cell (MSCs) and provides an updated view of the many stem/progenitor cell populations contributing to fracture repair.

RECENT FINDINGS

Functional studies show MSCs are not the multipotential stem cell population that form cartilage and bone during fracture repair. Rather, multiple studies have confirmed the periosteum is the primary source of stem/progenitor cells for fracture repair. Newer work is also identifying other stem/progenitor cells that may also contribute to healing. Although the heterogenous periosteal cells migrate to the fracture site and contribute directly to callus formation, other cell populations are involved. Pericytes and bone marrow stromal cells are now thought of as key secretory centers that mostly coordinate the repair process. Other populations of stem/progenitor cells from the muscle and transdifferentiated chondroctyes may also contribute to repair, and their functional role is an area of active research.

The Interaction of CD97/ADGRE5 With β-Catenin in Adherens Junctions Is Lost During Colorectal Carcinogenesis

The adhesion G-protein-coupled receptor CD97/ADGRE5 is present in adherens junctions of human normal intestinal cells and upregulated in colorectal carcinomas. Here, we examined whether CD97 directly interacts with junctional proteins in normal and malignant colorectal tissue. We identified an association of CD97 with β-catenin using a proximity ligation assay and confirmed the interaction between both endogenous proteins at the biochemical level by co-immunoprecipitation in human and mouse tissues and cell lines. Glutathione S-transferase-pulldown revealed that CD97 binds β-catenin through its seven-span transmembrane/intracellular domain(s). To study tumor-associated changes in the interaction of CD97 and β-catenin in situ, we quantified and correlated both proteins at the membrane, and in the cytoplasm and nuclei of colorectal carcinomas and their corresponding normal tissues (n = 111). In normal colon, membranous levels of CD97 and β-catenin correlated strongly (p < 0.0001). To some degree both molecules disappeared in carcinomas simultaneously from the membrane of tumor cells (p = 0.017). CD97 accumulated in the cytoplasm, whereas β-catenin emerged in the cytoplasm and nuclei. CD97 and β-catenin levels in the cytoplasm correlated well (p < 0.0001). Irrespective of their subcellular localization, interaction of CD97 with β-catenin in tumor cells was also restricted to the cell contacts. Accordingly, CD97 did not regulate β-catenin-dependent TCF-mediated transcriptional activity. In summary, while CD97 and β-catenin interact in adherens junctions, their interaction is lost and both molecules follow different functional paths inside tumor cells.

Odd-skipped related 1 inhibits lung cancer proliferation and invasion by reducing Wnt signaling through the suppression of SOX9 and β-catenin

The odd‐skipped related 1 (OSR1) gene encodes a zinc‐finger transcription factor. The expression and significance of OSR1 in human tumors remains unclear. We found that OSR1 was downregulated in lung cancers, and its expression was correlated with poor differentiation. Overexpression of OSR1 by OSR1 gene transfection into H1299 cells (H1299‐OSR1) inhibited the proliferation and invasion of lung cancer cells. Knockdown of OSR1 with small interfering (si)RNA against OSR1 in A549 cells (A549‐siOSR1) enhanced the proliferation and invasion of lung cancer cells. Western blot analysis showed that the expression level of GSK3β increased, while that of p‐GSK3β, nuclear β‐catenin, cyclin D1, c‐Myc and matrix metallopeptidase 7 significantly decreased in the H1299‐OSR1 cells, and this pattern was reversed in the A549‐siOSR1 cells compared to that in the control cells. Furthermore, upregulation of sex‐determining region Y‐box 9 (SOX9) by SOX9 gene transfection increased the expression of β‐catenin, which was inhibited by OSR1. The mRNA and protein expression levels of SOX9 and β‐catenin were reduced in H1299‐OSR1 cells and increased in A549‐siOSR1 cells. In conclusion, the expression of OSR1 was more reduced in lung cancer tissues than in normal lung tissues, and was correlated with poor differentiation. OSR1 downregulated the activity of the Wnt signaling pathway by suppressing the expression of SOX9 and β‐catenin.

Microenvironmental Regulation of Chondrocyte Plasticity in Endochondral Repair-A New Frontier for Developmental Engineering

The majority of fractures heal through the process of endochondral ossification, in which a cartilage intermediate forms between the fractured bone ends and is gradually replaced with bone. Recent studies have provided genetic evidence demonstrating that a significant portion of callus chondrocytes transform into osteoblasts that derive the new bone. This evidence has opened a new field of research aimed at identifying the regulatory mechanisms that govern chondrocyte transformation in the hope of developing improved fracture therapies. In this article, we review known and candidate molecular pathways that may stimulate chondrocyte-to-osteoblast transformation during endochondral fracture repair. We also examine additional extrinsic factors that may play a role in modulating chondrocyte and osteoblast fate during fracture healing such as angiogenesis and mineralization of the extracellular matrix. Taken together the mechanisms reviewed here demonstrate the promising potential of using developmental engineering to design therapeutic approaches that activate endogenous healing pathways to stimulate fracture repair.

Highly Proliferative α-Cell-Related Islet Endocrine Cells in Human Pancreata

The proliferative response of non-β islet endocrine cells in response to type 1 diabetes (T1D) remains undefined. We quantified islet endocrine cell proliferation in a large collection of nondiabetic control and T1D human pancreata across a wide range of ages. Surprisingly, islet endocrine cells with abundant proliferation were present in many adolescent and young-adult T1D pancreata. But the proliferative islet endocrine cells were also present in similar abundance within control samples. We queried the proliferating islet cells with antisera against various islet hormones. Although pancreatic polypeptide, somatostatin, and ghrelin cells did not exhibit frequent proliferation, glucagon-expressing α-cells were highly proliferative in many adolescent and young-adult samples. Notably, α-cells only comprised a fraction (∼1/3) of the proliferative islet cells within those samples; most proliferative cells did not express islet hormones. The proliferative hormone-negative cells uniformly contained immunoreactivity for ARX (indicating α-cell fate) and cytoplasmic Sox9 (Sox9^Cyt). These hormone-negative cells represented the majority of islet endocrine Ki67+ nuclei and were conserved from infancy through young adulthood. Our studies reveal a novel population of highly proliferative ARX+ Sox9^Cyt hormone-negative cells and suggest the possibility of previously unrecognized islet development and/or lineage plasticity within adolescent and adult human pancreata.

SOX9 is an atypical intestinal tumor suppressor controlling the oncogenic Wnt/ß-catenin signaling

SOX9 inactivation is frequent in colorectal cancer (CRC) due to SOX9 gene mutations and/or to ectopic expression of MiniSOX9, a dominant negative inhibitor of SOX9. In the present study, we report a heterozygous L142P inactivating mutation of SOX9 in the DLD-1 CRC cell line and we demonstrate that the conditional expression of a wild type SOX9 in this cell line inhibits cell growth, clonal capacity and colonosphere formation while decreasing both the activity of the oncogenic Wnt/ß-catenin signaling pathway and the expression of the c-myc oncogene. This activity does not require SOX9 transcriptional function but, rather, involves an interaction of SOX9 with nuclear ß-catenin. Furthermore, we report that SOX9 inhibits tumor development when conditionally expressed in CRC cells injected either subcutaneous or intraperitoneous in BALB/c mice as an abdominal metastasis model. These observations argue in favor of a tumor suppressor activity for SOX9. As an siRNA targeting SOX9 paradoxically also inhibits DLD-1 and HCT116 CRC cell growth, we conclude that there is a critical level of endogenous active SOX9 needed to maintain CRC cell growth.

Sox5 is involved in germ-cell regulation and sex determination in medaka following co-option of nested transposable elements

Background

Sex determination relies on a hierarchically structured network of genes, and is one of the most plastic processes in evolution. The evolution of sex-determining genes within a network, by neo- or sub-functionalization, also requires the regulatory landscape to be rewired to accommodate these novel gene functions. We previously showed that in medaka fish, the regulatory landscape of the master male-determining gene dmrt1bY underwent a profound rearrangement, concomitantly with acquiring a dominant position within the sex-determining network. This rewiring was brought about by the exaptation of a transposable element (TE) called Izanagi, which is co-opted to act as a silencer to turn off the dmrt1bY gene after it performed its function in sex determination.

Results

We now show that a second TE, Rex1, has been incorporated into Izanagi. The insertion of Rex1 brought in a preformed regulatory element for the transcription factor Sox5, which here functions in establishing the temporal and cell-type-specific expression pattern of dmrt1bY. Mutant analysis demonstrates the importance of Sox5 in the gonadal development of medaka, and possibly in mice, in a dmrt1bY-independent manner. Moreover, Sox5 medaka mutants have complete female-to-male sex reversal.

Conclusions

Our work reveals an unexpected complexity in TE-mediated transcriptional rewiring, with the exaptation of a second TE into a network already rewired by a TE. We also show a dual role for Sox5 during sex determination: first, as an evolutionarily conserved regulator of germ-cell number in medaka, and second, by de novo regulation of dmrt1 transcriptional activity during primary sex determination due to exaptation of the Rex1 transposable element.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0485-8) contains supplementary material, which is available to authorized users.

Targeting immune checkpoints potentiates immunoediting and changes the dynamics of tumor evolution

The cancer immunoediting hypothesis postulates a dual role of the immune system: protecting the host by eliminating tumor cells, and shaping the tumor by editing its genome. Here, we elucidate the impact of evolutionary and immune-related forces on editing the tumor in a mouse model for hypermutated and microsatellite-instable colorectal cancer. Analyses of wild-type and immunodeficient RAG1 knockout mice transplanted with MC38 cells reveal that upregulation of checkpoint molecules and infiltration by Tregs are the major tumor escape mechanisms. Our results show that the effects of immunoediting are weak and that neutral accumulation of mutations dominates. Targeting the PD-1/PD-L1 pathway using immune checkpoint blocker effectively potentiates immunoediting. The immunoediting effects are less pronounced in the CT26 cell line, a non-hypermutated/microsatellite-instable model. Our study demonstrates that neutral evolution is another force that contributes to sculpting the tumor and that checkpoint blockade effectively enforces T-cell-dependent immunoselective pressure.

The cancer immunoediting hypothesis assumes the immune system sculpts the cancer genome. Here the authors show, in a mouse model, that neutral evolution outweighs the effects of immunoselection and that immune checkpoint blockade potentiates the immunoediting, switching the system to non-neutral evolution.

Expression of SRY-related HMG Box Transcription Factors (Sox) 2 and 9 in Craniopharyngioma Subtypes and Surrounding Brain Tissue

Stem cells have been discovered as key players in the genesis of different neoplasms including craniopharyngioma (CP), a rare tumour entity in the sellar region. Sox2 and Sox9 are well-known stem cell markers involved in pituitary development. In this study we analysed the expression of both transcription factors using immunohistochemistry in a large cohort of 64 adamantinomatous (aCP) and 9 papillary CP (pCP) and quantitative PCR in 26 aCP and 7 pCP. Whereas immunohistochemically Sox2+ cells were verifiable in only five aCP (7.8%) and in 39.1% of the respective surrounding cerebral tissue, pCP specimens appeared always negative. In contrast, Sox9 was detectable in all tumours with a significantly higher expression in aCP compared to pCP (protein, p < 0.0001; mRNA p = 0.0484) This was also true for the respective tumour adjacent CNS where 63 aCP (98.4%) and six pCP (66.7%) showed Sox9+ cells. We further confirmed absence of Sox9 expression in nuclear β-catenin accumulating cells of aCP. Our results point to the conclusion that Sox2 and Sox9, seem to play essential roles not only in the specific formation of aCP, but also in processes involving the cerebral tumour environment, which needs to be illuminated in the future.

SHP2 Regulates the Osteogenic Fate of Growth Plate Hypertrophic Chondrocytes

Transdifferentiation of hypertrophic chondrocytes into bone-forming osteoblasts has been reported, yet the underlying molecular mechanism remains incompletely understood. SHP2 is an ubiquitously expressed cytoplasmic protein tyrosine phosphatase. SHP2 loss-of-function mutations in chondroid cells are linked to metachondromatosis in humans and mice, suggesting a crucial role for SHP2 in the skeleton. However, the specific role of SHP2 in skeletal cells has not been elucidated. To approach this question, we ablated SHP2 in collagen 2α1(Col2α1)-Cre- and collagen 10α1(Col10α1)-Cre-expressing cells, predominantly proliferating and hypertrophic chondrocytes, using "Cre-loxP"-mediated gene excision. Mice lacking SHP2 in Col2α1-Cre-expressing cells die at mid-gestation. Postnatal SHP2 ablation in the same cell population caused dwarfism, chondrodysplasia and exostoses. In contrast, mice in which SHP2 was ablated in the Col10α1-Cre-expressing cells appeared normal but were osteopenic. Further mechanistic studies revealed that SHP2 exerted its influence partly by regulating the abundance of SOX9 in chondrocytes. Elevated and sustained SOX9 in SHP2-deficient hypertrophic chondrocytes impaired their differentiation to osteoblasts and impaired endochondral ossification. Our study uncovered an important role of SHP2 in bone development and cartilage homeostasis by influencing the osteogenic differentiation of hypertrophic chondrocytes and provided insight into the pathogenesis and potential treatment of skeletal diseases, such as osteopenia and osteoporosis.

Emerging potential of gene silencing approaches targeting anti-chondrogenic factors for cell-based cartilage repair

The field of cartilage repair has exponentially been growing over the past decade. Here, we discuss the possibility to achieve satisfactory regeneration of articular cartilage by means of human mesenchymal stem cells (hMSCs) depleted of anti-chondrogenic factors and implanted in the site of injury. Different types of molecules including transcription factors, transcriptional co-regulators, secreted proteins, and microRNAs have recently been identified as negative modulators of chondroprogenitor differentiation and chondrocyte function. We review the current knowledge about these molecules as potential targets for gene knockdown strategies using RNA interference (RNAi) tools that allow the specific suppression of gene function. The critical issues regarding the optimization of the gene silencing approach as well as the delivery strategies are discussed. We anticipate that further development of these techniques will lead to the generation of implantable hMSCs with enhanced potential to regenerate articular cartilage damaged by injury, disease, or aging.

Cartilage to bone transformation during fracture healing is coordinated by the invading vasculature and induction of the core pluripotency genes

Fractures heal predominantly through the process of endochondral ossification. The classic model of endochondral ossification holds that chondrocytes mature to hypertrophy, undergo apoptosis and new bone forms by invading osteoprogenitors. However, recent data demonstrate that chondrocytes transdifferentiate to osteoblasts in the growth plate and during regeneration, yet the mechanism(s) regulating this process remain unknown. Here, we show a spatially-dependent phenotypic overlap between hypertrophic chondrocytes and osteoblasts at the chondro-osseous border in the fracture callus, in a region we define as the transition zone (TZ). Hypertrophic chondrocytes in the TZ activate expression of the pluripotency factors [Sox2, Oct4 (Pou5f1), Nanog], and conditional knock-out of Sox2 during fracture healing results in reduction of the fracture callus and a delay in conversion of cartilage to bone. The signal(s) triggering expression of the pluripotency genes are unknown, but we demonstrate that endothelial cell conditioned medium upregulates these genes in ex vivo fracture cultures, supporting histological evidence that transdifferentiation occurs adjacent to the vasculature. Elucidating the cellular and molecular mechanisms underlying fracture repair is important for understanding why some fractures fail to heal and for developing novel therapeutic interventions.

Methylation-mediated silencing of miR-124 facilitates chondrogenesis by targeting NFATc1 under hypoxic conditions

Chondrogenic differentiation of mesenchymal stem cells is regulated by many different pathways. Recent studies have established that hypoxia and epigenetic alterations potently affect expression of chondrogenesis marker genes. Sox9 is generally regarded as a master regulator of chondrogenesis and microRNA-124 (miRNA-124) regulates gene expression in murine bone marrow-derived mesenchymal stem cells. Therefore, in this study we investigated whether epigenetic regulation of miRNA-124 could affect the expression of Sox9 and thereby regulate chondrogenesis. A cell pellet culture model was used to induce chondrogenesis in C3H10T1/2 cells under hypoxic conditions (2% O₂) to determine the effects of hypoxia on miR-124 expression and DNA methylation. The expression of miR-124 was significantly downregulated under hypoxic conditions compared to normoxic conditions (21% O₂). The expression of chondrogenesis marker genes was significantly increased under hypoxic conditions. Bisulfite sequencing of the CpG islands in the promoter region of miR-124-3 showed that CpG methylation was significantly increased under hypoxic conditions. Treating the cells with the DNA demethylating agent 5'-AZA significantly increased miR-124 expression and decreased expression of markers of chondrogenesis. Overexpressing miR-124 under hypoxic conditions inhibited NFATc1 reporter activity. NFATc1 was shown to bind to the promoter region of Sox9. Taken together, our data provide evidence that miR-124 acts as an inhibitor of NFATc1. Under hypoxic conditions when miR-124 is downregulated by methylation of CpG islands in the promoter, NFATc1 can bind to the Sox9 promoter and induce the expression of Sox9 leading to chondrogenesis. These results support the role of epigenetic regulation in establishing and maintaining a chondrogenic phenotype.

Self-assembled N-cadherin mimetic peptide hydrogels promote the chondrogenesis of mesenchymal stem cells through inhibition of canonical Wnt/β-catenin signaling

N-cadherin, a transmembrane protein and major component of adherens junction, mediates cell-cell interactions and intracellular signaling that are important to the regulation of cell behaviors and organ development. Previous studies have identified mimetic peptides that possess similar bioactivity as that of N-cadherin, which promotes chondrogenesis of human mesenchymal stem cells (hMSCs); however, the molecular mechanism remains unknown. In this study, we combined the N-cadherin mimetic peptide (HAVDI) with the self-assembling KLD-12 peptide: the resultant peptide is capable of self-assembling into hydrogels functionalized with N-cadherin peptide in phosphate-buffered saline (PBS) at 37 °C. Encapsulation of hMSCs in these hydrogels showed enhanced expression of chondrogenic marker genes and deposition of cartilage specific extracellular matrix rich in proteoglycan and Type II Collagen compared to control hydrogels, with a scrambled-sequence peptide after 14 days of chondrogenic culture. Furthermore, western blot showed a significantly higher expression of active glycogen synthase kinase-3β (GSK-3β), which phosphorylates β-catenin and facilitates ubiquitin-mediated degradation, as well as a lower expression of β-catenin and LEF1 in the N-cadherin peptide hydrogels versus controls. Immunofluorescence staining revealed significantly less nuclear localization of β-catenin in N-cadherin mimetic peptide hydrogels. Our findings suggest that N-cadherin peptide hydrogels suppress canonical Wnt signaling in hMSCs by reducing β-catenin nuclear translocation and the associated transcriptional activity of β-catenin/LEF-1/TCF complex, thereby enhancing the chondrogenesis of hMSCs. Our biomimetic self-assembled peptide hydrogels can serve as a tailorable and versatile three-dimensional culture platform to investigate the effect of biofunctionalization on stem cell behavior.

Impact of mechanical stimulation on the chondrogenic processes in human bone marrow aspirates modified to overexpress sox9 via rAAV vectors

Background

Evaluation of gene-based approaches to target human bone marrow aspirates in conditions of mechanical stimulation that aim at reproducing the natural joint environment may allow to develop improved treatments for articular cartilage injuries. In the present study, we investigated the potential of rAAV-mediated sox9 gene transfer to enhance the chondrogenic differentiation processes in human bone marrow aspirates under established hydrodynamic conditions compared with the more commonly employed static culture conditions.

Methods

Fresh human bone marrow aspirates were transduced with rAAV-FLAG-hsox9 (40 μl) and maintained for up to 28 days in chondrogenic medium under mechanically-induced conditions in dynamic flow rotating bioreactors that permit tissue growth and matrix deposition relative to static culture conditions. The samples were then processed to examine the potential effects of sox9 overexpression on the cellular activities (matrix synthesis, proliferation) and on the chondrogenic differentiation potency compared with control treatments (absence of rAAV vector; reporter rAAV-lacZ, rAAV-RFP, and rAAV-luc gene transfer).

Results

Prolonged, significant sox9 overexpression via rAAV was achieved in the aspirates for at least 28 days when applying the rAAV-FLAG-hsox9 construct, leading to higher, prolonged levels of matrix biosynthesis and to enhanced chondrogenic activities relative to control treatments especially when maintaining the samples under mechanical stimulation. Administration of sox9 however did not impact the indices of proliferation in the aspirates. Remarkably, sox9 gene transfer also durably delayed hypertrophic and osteogenic differentiation in the samples regardless of the conditions of culture applied versus control treatments.

Conclusions

The current observations show the value of genetically modifying human bone marrow aspirates upon mechanical stimulation by rAAV sox9 as a promising strategy for future treatments to improve cartilage repair by implantation in lesions where the tissue is submitted to natural mechanical forces.

The LncRNA ZBED3-AS1 induces chondrogenesis of human synovial fluid mesenchymal stem cells

Human synovial fluid-derived mesenchymal stem cells (SFMSCs) have great potential for cartilage induction and are promising for cell-based strategies for articular cartilage repair. Many long non-coding RNAs (lncRNAs) regulate chondrogenesis of MSCs. We hypothesized that the divergent lncRNA ZBED3-AS1, which binds locally to chromatin, could promote the expression of zbed3, a novel Axin-interacting protein that activates Wnt/β-catenin signaling, involved in chondrogenesis. However, the function of ZBED3-AS1 in SFMSCs is unclear. In this study, the expression, biological function, and roles of ZBED3-AS1 in SFMSC chondrogenesis were examined by multilineage differentiation, flow cytometry, and gain-of-function studies. We found that ZBED3-AS1 promotes chondrogenesis. Furthermore, ZBED3-AS1 could directly increase zbed3 expression. Finally, the wnt-inhibitor DKK1 could reverse the stimulatory effect of ZBED3-AS1 on chondrogenesis. These findings demonstrate the role of a new lncRNA, ZBED3-AS1, in SFMSC chondrogenesis and may improve osteoarthritis treatment.

Lawsonia intracellularis exploits β-catenin/Wnt and Notch signalling pathways during infection of intestinal crypt to alter cell homeostasis and promote cell proliferation

Lawsonia intracellularis is an obligate intracellular bacterial pathogen that causes proliferative enteropathy (PE) in pigs. L. intracellularis infection causes extensive intestinal crypt cell proliferation and inhibits secretory and absorptive cell differentiation. However, the affected host upstream cellular pathways leading to PE are still unknown. β-catenin/Wnt signalling is essential in maintaining intestinal stem cell (ISC) proliferation and self-renewal capacity, while Notch signalling governs differentiation of secretory and absorptive lineage specification. Therefore, in this report we used immunofluorescence (IF) and quantitative reverse transcriptase PCR (RTqPCR) to examine β-catenin/Wnt and Notch-1 signalling levels in uninfected and L. intracellularis infected pig ileums at 3, 7, 14, 21 and 28 days post challenge (dpc). We found that while the significant increase in Ki67+ nuclei in crypts at the peak of L. intracellularis infection suggested enhanced cell proliferation, the expression of c-MYC and ASCL2, promoters of cell growth and ISC proliferation respectively, was down-regulated. Peak infection also coincided with enhanced cytosolic and membrane-associated β-catenin staining and induction of AXIN2 and SOX9 transcripts, both encoding negative regulators of β-catenin/Wnt signalling and suggesting a potential alteration to β-catenin/Wnt signalling levels, with differential regulation of the expression of its target genes. We found that induction of HES1 and OLFM4 and the down-regulation of ATOH1 transcript levels was consistent with the increased Notch-1 signalling in crypts at the peak of infection. Interestingly, the significant down-regulation of ATOH1 transcript levels coincided with the depletion of MUC2 expression at 14 dpc, consistent with the role of ATOH1 in promoting goblet cell maturation. The lack of significant change to LGR5 transcript levels at the peak of infection suggested that the crypt hyperplasia was not due to the expansion of ISC population. Overall, simultaneous induction of Notch-1 signalling and the attenuation of β-catenin/Wnt pathway appear to be associated with the inhibition of goblet cell maturation and enhanced crypt cell proliferation at the peak of L. intracellularis infection. Moreover, the apparent differential regulation of apoptosis between crypt and lumen cells together with the strong induction of Notch-1 signalling and the enhanced SOX9 expression along crypts 14 dpc suggest an expansion of actively dividing transit amplifying and/or absorptive progenitor cells and provide a potential basis for understanding the development and maintenance of PE.

Sox9 transcriptionally regulates Wnt signaling in intestinal epithelial stem cells in hypomethylated crypts in the diabetic state

Background

Distinctive structures called crypts harbor intestinal epithelial stem cells (IESCs) which generate progenitor and terminally differentiated cells in the intestinal epithelium. Mammalian IESCs and their daughter cells require the participation of DNA methylation and the transcription factor Sox9 for proliferation and differentiation. However, the association between Sox9 and DNA methylation in this process remains elusive.

Methods

The DNA methylation of small intestinal epithelial crypts in db/db mice was detected via combining methylated DNA immunoprecipitation with microarray hybridization. DNA methylation of Sox9 promoter in crypts and IESCs was validated using bisulfite sequence analysis. The target sequence of the transcription factor Sox9 in IESCs was investigated via chromatin immunoprecipitation (ChIP) combined with deep sequencing (ChIP-seq).

Results

Increased Sox9 expression is accompanied by the loss of methylation in its promoter in IESCs. Sox9 targets the enhancers of the Wnt signaling pathway-related genes. Sox9 predominantly acts as a transcriptional activator at proximal enhancers of Wnt4, Tab2, Sox4, and Fzd8, but also functions as a potential transcriptional inhibitor at a distant enhancer of Cdk1. Lack of Sox9 transcriptional activation in specific repressors of the Wnt signaling pathway leads to the loss of intrinsic inhibitory action and ultimately produces overactivation of this pathway in db/db mice.

Conclusions

Our study sheds light on the connections among DNA methylation, transcription factor modulation, and Wnt signaling in IESCs in the diabetic state. Hypomethylation in the Sox9 promoter is correlated to increased Sox9 expression in db/db IESCs. Although there is increased expression of Sox9 in db/db IESCs, the loss of Sox9 transcriptional activation in specific repressors of the Wnt signaling pathway might result in abnormalities in this pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0507-4) contains supplementary material, which is available to authorized users.

Significant Associations of SOX9 Gene Polymorphism and Gene Expression with the Risk of Osteonecrosis of the Femoral Head in a Han Population in Northern China

Sex determining region Y-box 9 (SOX9) is a key transcription factor involved in cartilage formation during the embryonic development stage and cartilage growth and repair after birth. To explore the roles of polymorphism and expression of the SOX9 gene in the development of osteonecrosis of the femoral head (ONFH), we analyzed the polymorphism of rs12601701 [A/G] and rs1042667 [A/C] and the serum protein expression of the SOX9 gene in 182 patients with ONFH and 179 healthy control subjects. Results revealed that the A-A haplotype of SOX9 gene as well as the GG and AA genotypes of rs12601701 was significantly associated with increased ONFH risk (P = 0.038) and the risk of bilateral hip lesions of ONFH (P = 0.009), respectively. The C-A, A-A, and A-G haplotypes were also statistically associated with the decreased and increased risk of bilateral hip lesions of ONFH (P = 0.03, P = 0.048, and P = 0.013), respectively, while the A-A haplotype closely related to the clinical stages of ONFH (P = 0.041). More importantly, the serum SOX9 protein expression of the ONFH group was greatly decreased compared to control group (P = 0.0001). Our results first showed that the gene polymorphism and gene expression of SOX9 were significantly associated with the risk and clinical phenotypes of ONFH and also indicate that the SOX9 gene may play a key role in the development of ONFH.

SOX9 and the many facets of its regulation in the chondrocyte lineage

SOX9 is a pivotal transcription factor in developing and adult cartilage. Its gene is expressed from the multipotent skeletal progenitor stage and is active throughout chondrocyte differentiation. While it is repressed in hypertrophic chondrocytes in cartilage growth plates, it remains expressed throughout life in permanent chondrocytes of healthy articular cartilage. SOX9 is required for chondrogenesis: it secures chondrocyte lineage commitment, promotes cell survival, and transcriptionally activates the genes for many cartilage-specific structural components and regulatory factors. Since heterozygous mutations within and around SOX9 were shown to cause the severe skeletal malformation syndrome called campomelic dysplasia, researchers around the world have worked assiduously to decipher the many facets of SOX9 actions and regulation in chondrogenesis. The more we learn, the more we realize the complexity of the molecular networks in which SOX9 fulfills its functions and is regulated at the levels of its gene, RNA, and protein, and the more we measure the many gaps remaining in knowledge. At the same time, new technologies keep giving us more means to push further the frontiers of knowledge. Research efforts must be pursued to fill these gaps and to better understand and treat many types of cartilage diseases in which SOX9 has or could have a critical role. These diseases include chondrodysplasias and cartilage degeneration diseases, namely osteoarthritis, a prevalent and still incurable joint disease. We here review the current state of knowledge of SOX9 actions and regulation in the chondrocyte lineage, and propose new directions for future fundamental and translational research projects.

The Signaling Pathways Involved in Chondrocyte Differentiation and Hypertrophic Differentiation

Chondrocytes communicate with each other mainly via diffusible signals rather than direct cell-to-cell contact. The chondrogenic differentiation of mesenchymal stem cells (MSCs) is well regulated by the interactions of varieties of growth factors, cytokines, and signaling molecules. A number of critical signaling molecules have been identified to regulate the differentiation of chondrocyte from mesenchymal progenitor cells to their terminal maturation of hypertrophic chondrocytes, including bone morphogenetic proteins (BMPs), SRY-related high-mobility group-box gene 9 (Sox9), parathyroid hormone-related peptide (PTHrP), Indian hedgehog (Ihh), fibroblast growth factor receptor 3 (FGFR3), and β-catenin. Except for these molecules, other factors such as adenosine, O₂ tension, and reactive oxygen species (ROS) also have a vital role in cartilage formation and chondrocyte maturation. Here, we outlined the complex transcriptional network and the function of key factors in this network that determine and regulate the genetic program of chondrogenesis and chondrocyte differentiation.

Signalling pathways in trophic skeletal development and morphogenesis: Insights from studies on teleost fish

During the development of the vertebrate feeding apparatus, a variety of complicated cellular and molecular processes participate in the formation and integration of individual skeletal elements. The molecular mechanisms regulating the formation of skeletal primordia and their development into specific morphological structures are tightly controlled by a set of interconnected signalling pathways. Some of these pathways, such as Bmp, Hedgehog, Notch and Wnt, are long known for their pivotal roles in craniofacial skeletogenesis. Studies addressing the functional details of their components and downstream targets, the mechanisms of their interactions with other signals as well as their potential roles in adaptive morphological divergence, are currently attracting considerable attention. An increasing number of signalling pathways that had previously been described in different biological contexts have been shown to be important in the regulation of jaw skeletal development and morphogenesis. In this review, I provide an overview of signalling pathways involved in trophic skeletogenesis emphasizing studies of the most species-rich group of vertebrates, the teleost fish, which through their evolutionary history have undergone repeated episodes of spectacular trophic diversification.

SOX9 is a novel cancer stem cell marker surrogated by osteopontin in human hepatocellular carcinoma

The current lack of cancer stem cell (CSC) markers that are easily evaluated by blood samples prevents the establishment of new therapeutic strategies in hepatocellular carcinoma (HCC). Herein, we examined whether sex determining region Y-box 9 (SOX9) represents a new CSC marker, and whether osteopontin (OPN) can be used as a surrogate marker of SOX9 in HCC. In HCC cell lines transfected with a SOX9 promoter-driven enhanced green fluorescence protein gene, FACS-isolated SOX9⁺ cells were capable of self-renewal and differentiation into SOX9⁻ cells, and displayed high proliferation capacity in vitro. Xenotransplantation experiments revealed that SOX9⁺ cells reproduced, differentiated into SOX9⁻ cells, and generated tumors at a high frequency in vivo. Moreover, SOX9⁺ cells were found to be involved in epithelial-mesenchymal transition (EMT) and activation of TGFb/Smad signaling. Gain/loss of function experiments showed that SOX9 regulates Wnt/beta-catenin signaling, including cyclin D1 and OPN. Immunohistochemistry of 166 HCC surgical specimens and serum OPN measurements showed that compared to SOX9⁻ patients, SOX9⁺ patients had significantly poorer recurrence-free survival, stronger venous invasion, and higher serum OPN levels. In conclusion, SOX9 is a novel HCC-CSC marker regulating the Wnt/beta-catenin pathway and its downstream target, OPN. OPN is a useful surrogate marker of SOX9 in HCC.

HMGA1 facilitates tumor progression through regulating Wnt/β-catenin pathway in endometrial cancer

Recent studies have identified a unique role for high mobility group protein A1 (HMGA1) as a major regulator of tumor progression and in diverse tumor models. Emerging evidences indicate that overexpressed HMGA1 facilitates multiple malignant phenotypes of cancer cells, however, the oncogenic activities of HMGA1 in endometrial cancer (EC) remains elusive. Here we showed that HMGA1 was more frequently expressed in human EC tissues compared to non-tumor tissues. Elevated HMGA1 was significantly associated with advanced clinical stage. Wound-healing assay and transwell assay showed that HMGA1 can positively regulate cell migration and invasion. Mechanistically, luciferase reporter assay and Western blotting assay demonstrated that activation of Wnt/β-catenin pathway contributed to the oncogenic activity of HMGA1. Taken together, our data reveal that HMGA1 may function as an oncogene and modulate EC cell migration and invasion by activating Wnt/β-catenin pathway, implying that suppression of HMGA1 might be a potential therapeutic strategy for EC.