Overexpression of Galnt3 in chondrocytes resulted in dwarfism due to the increase of mucin-type O-glycans and reduction of glycosaminoglycans

Runx2 Regulates Galnt3 and Fgf23 Expressions and Galnt3 Decelerates Osteoid Mineralization by Stabilizing Fgf23

Runx2 (runt related transcription factor 2) is an essential transcription factor for osteoblast proliferation and differentiation. Uridine diphosphate (UDP)-N-acetylgalactosamine (GalNAc): polypeptide GalNAc-transferase 3 (Galnt3) prevents proteolytic processing of fibroblast growth factor 23 (Fgf23), which is a hormone that regulates the serum level of phosphorus. Runx2 and Galnt3 were expressed in osteoblasts and osteocytes, and Fgf23 expression was restricted to osteocytes in bone. Overexpression and knock-down of Runx2 upregulated and downregulated, respectively, the expressions of Galnt3 and Fgf23, and Runx2 directly regulated the transcriptional activity of Galnt3 in reporter assays. The expressions of Galnt3 and Fgf23 in osteoblast-specific Runx2 knockout (Runx2fl/flCre) mice were about half those in Runx2fl/fl mice. However, the serum levels of phosphorus and intact Fgf23 in Runx2fl/flCre mice were similar to those in Runx2fl/fl mice. The trabecular bone volume was increased during aging in both male and female Galnt3-/- mice, but the osteoid was reduced. The markers for bone formation and resorption in Galnt3-/- mice were similar to the control in both sexes. Galnt3-/- mice exhibited hyperphosphatemia and hypercalcemia, and the intact Fgf23 was about 40% that of wild-type mice. These findings indicated that Runx2 regulates the expressions of Galnt3 and Fgf23 and that Galnt3 decelerates the mineralization of osteoid by stabilizing Fgf23.

Relationship between rs7586085, GALNT3 and CCDC170 gene polymorphisms and the risk of osteoporosis among the Chinese Han population

Osteoporosis (OP) has plagued many women for years, and bone density loss is an indicator of OP. The purpose of this study was to evaluate the relationship between the polymorphism of the rs7586085, CCDC170 and GALNT3 gene polymorphisms and the risk of OP in the Chinese Han population. Using the Agena MassArray method, we identified six candidate SNPs on chromosomes 2 and 6 in 515 patients with OP and 511 healthy controls. Genetic model analysis was performed to evaluate the significant association between variation and OP risk, and meanwhile, the multiple tests were corrected by false discovery rate (FDR). Haploview 4.2 was used for haplotype analysis. In stratified analysis of BMI ˃ 24, rs7586085, rs6726821, rs6710518, rs1346004, and rs1038304 were associated with the risk of OP based on the results of genetic models among females even after the correction of FDR (qd < 0.05). In people at age ≤ 60 years, rs1038304 was associated with an increased risk of OP under genetic models after the correction of FDR (qd < 0.05). Our study reported that GALNT3 and CCDC170 gene polymorphisms and rs7586085 are the effective risk factors for OP in the Chinese Han population.

Role of Glycosylation in Vascular Calcification

Glycosylation is an important step in post-translational protein modification. Altered glycosylation results in an abnormality that causes diseases such as malignancy and cardiovascular diseases. Recent emerging evidence highlights the importance of glycosylation in vascular calcification. Two major types of glycosylation, N-glycosylation and O-glycosylation, are involved in vascular calcification. Other glycosylation mechanisms, which polymerize the glycosaminoglycan (GAG) chain onto protein, resulting in proteoglycan (PG), also have an impact on vascular calcification. This paper discusses the role of glycosylation in vascular calcification.

Alteration of the Total Cellular Glycome during Late Differentiation of Chondrocytes

In normal articular cartilage, chondrocytes do not readily proliferate or terminally differentiate, and exhibit a low level of metabolism. Hypertrophy-like changes of chondrocytes have been proposed to play a role in the pathogenesis of osteoarthritis by inducing protease-mediated cartilage degradation and calcification; however, the molecular mechanisms underlying these changes are unclear. Glycans are located on the outermost cell surface. Dynamic cellular differentiation can be monitored and quantitatively characterized by profiling the glycan structures of total cellular glycoproteins. This study aimed to clarify the alterations in glycans upon late differentiation of chondrocytes, during which hypertrophy-like changes occur. Primary mouse chondrocytes were differentiated using an insulin-induced chondro-osteogenic differentiation model. Comprehensive glycomics, including N-glycans, O-glycans, free oligosaccharides, glycosaminoglycan, and glycosphingolipid, were analyzed for the chondrocytes after 0-, 10- and 20-days cultivation. The comparison and clustering of the alteration of glycans upon hypertrophy-like changes of primary chondrocytes were performed. Comprehensive glycomic analyses provided complementary alterations in the levels of various glycans derived from glycoconjugates during hypertrophic differentiation. In addition, expression of genes related to glycan biosynthesis and metabolic processes was significantly correlated with glycan alterations. Our results indicate that total cellular glycan alterations are closely associated with chondrocyte hypertrophy and help to describe the glycophenotype by chondrocytes and their hypertrophic differentiation. our results will assist the identification of diagnostic and differentiation biomarkers in the future.

Mechanism of Low Expression of miR-30a-5p on Epithelial-Mesenchymal Transition and Metastasis in Ovarian Cancer

Metastasis of ovarian cancer is regulated by microRNAs. This study focused on the effects of miR-30a-5p on ovarian cancer migration and invasion. Our results showed that the miR-30a-5p and mucin type O-glycan biosynthesis are closely related to ovarian cancer, and that miR-30a-5p was downregulated in ovarian cancer cells. miR-30a-5p overexpression reduced cell viability and inhibited migration and invasion in HO-8910 and HO-8910PM cells. S phase kinase-associated protein 2 (SKP2), B cell lymphoma 9 (BCL9), and NOTHC1 are direct target genes of miR-30a-5p. MTDH, SKP2, BCL9, and NOTCH1 genes were overexpressed in ovarian cancer cells, and they are direct target genes of miR-30a-5p. miR-30a-5p overexpression inhibited epithelial-mesenchymal transition (EMT) process, while upregulation of SKP2, BCL9, and NOTCH1 gene expression levels reduced the inhibition of EMT process by miR-30a-5p. miR-30a-5p was lowly expressed in ovarian cancer, and such a phenomenon is related to ovarian cancer metastasis. miR-30a-5p might inhibit the migration and invasion of ovarian cancer cells by downregulating the expression of SKP2, BCL9, and NOTCH1 genes.

Characterization of 5-Fluorouracil Daily Oral Dosing versus Dietary Restriction on Femoral Growth Plates in Rats

We evaluated the growth plates (GPs) of rats after a 14-day reduction in food consumption caused by either daily oral dosing with 5-fluorouracil (5-FU: a positive control reducing food consumption and affecting the GPs) or a direct reduction in food consumption to determine whether the observed changes were attributable to a direct effect of drug toxicity. Histomorphometric analyses of the femoral GP were performed for a nontreated (NT) control group, three groups treated with 5-FU (12, 15, and 18 mg/kg/day) and three groups with food intake restricted to levels corresponding to those consumed by the rats in the three 5-FU-treated groups. Compared with the NT group, the GP widths and the number of chondrocytes in the proliferative zone decreased significantly in all the 5-FU-treated groups and the dietary restriction groups. Importantly, no significant differences between the 5-FU-treated groups and the groups with matched dietary restrictions were seen for most parameters. Thus, the 14-day dietary restriction caused significant changes in the proliferative zone of the GP, and similar changes observed in the 5-FU-treated groups were presumed to result from the comparable reduction in food intake rather than being a direct toxic effect of the drug.

Genome-wide analysis of endogenously expressed ZEB2 binding sites reveals inverse correlations between ZEB2 and GalNAc-transferase GALNT3 in human tumors

BACKGROUND

ZEB2 is a transcriptional repressor that regulates epithelial-to-mesenchymal transition (EMT) through binding to bipartite E-box motifs in gene regulatory regions. Despite the abundant presence of E-boxes within the human genome and the multiplicity of pathophysiological processes regulated during ZEB2-induced EMT, only a small fraction of ZEB2 targets has been identified so far. Hence, we explored genome-wide ZEB2 binding by chromatin immunoprecipitation-sequencing (ChIP-seq) under endogenous ZEB2 expression conditions.

METHODS

For ChIP-Seq we used an anti-ZEB2 monoclonal antibody, clone 6E5, in SNU398 hepatocellular carcinoma cells exhibiting a high endogenous ZEB2 expression. The ChIP-Seq targets were validated using ChIP-qPCR, whereas ZEB2-dependent expression of target genes was assessed by RT-qPCR and Western blotting in shRNA-mediated ZEB2 silenced SNU398 cells and doxycycline-induced ZEB2 overexpressing colorectal carcinoma DLD1 cells. Changes in target gene expression were also assessed using primary human tumor cDNA arrays in conjunction with RT-qPCR. Additional differential expression and correlation analyses were performed using expO and Human Protein Atlas datasets.

RESULTS

Over 500 ChIP-Seq positive genes were annotated, and intervals related to these genes were found to include the ZEB2 binding motif CACCTG according to TOMTOM motif analysis in the MEME Suite database. Assessment of ZEB2-dependent expression of target genes in ZEB2-silenced SNU398 cells and ZEB2-induced DLD1 cells revealed that the GALNT3 gene serves as a ZEB2 target with the highest, but inversely correlated, expression level. Remarkably, GALNT3 also exhibited the highest enrichment in the ChIP-qPCR validation assays. Through the analyses of primary tumor cDNA arrays and expO datasets a significant differential expression and a significant inverse correlation between ZEB2 and GALNT3 expression were detected in most of the tumors. We also explored ZEB2 and GALNT3 protein expression using the Human Protein Atlas dataset and, again, observed an inverse correlation in all analyzed tumor types, except malignant melanoma. In contrast to a generally negative or weak ZEB2 expression, we found that most tumor tissues exhibited a strong or moderate GALNT3 expression.

CONCLUSIONS

Our observation that ZEB2 negatively regulates a GalNAc-transferase (GALNT3) that is involved in O-glycosylation adds another layer of complexity to the role of ZEB2 in cancer progression and metastasis. Proteins glycosylated by GALNT3 may be exploited as novel diagnostics and/or therapeutic targets.

Ethanolic extracts of babandotan leaves (Ageratum conyzoides L.) prevents inflammation and proteoglycan degradation by inhibiting TNF-α and MMP-9 on osteoarthritis rats induced by monosodium iodoacetate

OBJECTIVE

To analyze the effects of Ageratum conyzoides L. on the monosodium iodoacetate induced osteoarthritis rats.

METHODS

Thin layer chromatography was performed to analyze the constituents of the babandotan extract leaves. White male Sprague-Dawley rats used in this study were divided into 6 groups: normal control and negative control groups, both given 0.5% carboxymethyl cellulose; the positive control group that was given glucosamine and chondroitin suspension (486 mg/200 g B.W.); the 3 dose variation extract groups including dose 1, 2, and 3 that were given 40, 80, and 160 mg/200 g B.W. respectively on day 29 until 50. All the groups were induced with 0.05 mL monosodium iodoacetate (20 mg/mL) on day 1, except normal control induced by saline. Measurement of edema volume of rat knees was performed on day 0, 8, 15, 22, 29, 43, and 50. Hematology data was measured at day 1, 29 and 50. Serum was collected at day 50 to evaluate TNF-α and MMP-9 by ELISA. Cartilage histopathology was evaluated by staining with H&E and Safranin-O-fast green staining on day 50.

RESULTS

The babandotan leaves extract dose 2 (80 mg/200 g B.W.) and dose 3 (160 mg/200 g B.W.) could decrease the edema volume, increase the area and thickness of articular cartilage, and increase proteoglycan level. Particularly, dose 3 (160 mg/200 g B.W.) of extract babandotan leaves were able to significantly decrease the number of leukocytes, lymphocytes and udem volume, and decrease TNF alpha and MMP-9 levels.

CONCLUSIONS

Babandotan leaves extract can recover inflammation and cartilages degradation by inhibiting TNF-α in inflammation processes and MMP-9 in the collagenase reaction in the cartilages.

Genetics of pediatric bone strength

Osteoporosis is one of the most common chronic forms of disability in postmenopausal women and represents a major health burden around the world. Bone fragility is affected by bone mineral density (BMD), and, one of the most important factors in preventing osteoporosis is optimizing peak bone mass, which is achieved during growth in childhood and adolescence. BMD is a complex trait resulting from environmental and genetic factors. Genome-wide association studies have discovered robust genetic signals influencing BMD in adults, and similar studies have also been conducted to investigate the genetics of BMD in the pediatric setting. These latter studies have revealed that many adult osteoporosis-related loci also regulate BMD during growth. These investigations have the potential to profoundly impact public health and will allow for the eventual development of effective interventions for the prevention of osteoporosis.

Influenza A Virus-Induced Expression of a GalNAc Transferase, GALNT3, via MicroRNAs Is Required for Enhanced Viral Replication

Influenza A virus (IAV) affects the upper and lower respiratory tracts and rapidly induces the expression of mucins, which are common O-glycosylated proteins, on the epithelial surfaces of the respiratory tract. Although mucin production is associated with the inhibition of virus transmission as well as characteristic clinical symptoms, little is known regarding how mucins are produced on the surfaces of respiratory epithelial cells and how they affect IAV replication. In this study, we found that two microRNAs (miRNAs), miR-17-3p and miR-221, which target GalNAc transferase 3 (GALNT3) mRNA, are rapidly downregulated in human alveolar basal epithelial cells during the early stage of IAV infection. We demonstrated that the expression of GALNT3 mRNA is upregulated in an IAV replication-dependent fashion and leads to mucin production in bronchial epithelial cells. A lectin microarray analysis revealed that the stable expression of GALNT3 by human alveolar basal epithelial cells induces mucin-type O-glycosylation modifications similar to those present in IAV-infected cells, suggesting that GALNT3 promotes mucin-type O-linked glycosylation in IAV-infected cells. Notably, analyses using short interfering RNAs and miRNA mimics showed that GALNT3 knockdown significantly reduces IAV replication. Furthermore, IAV replication was markedly decreased in embryonic fibroblast cells obtained from galnt3-knockout mice. Interestingly, IAV-infected galnt3-knockout mice exhibited high mortality and severe pathological alterations in the lungs compared to those of wild-type mice. Our results demonstrate not only the molecular mechanism underlying rapid mucin production during IAV infection but also the contribution of O-linked glycosylation to the replication and propagation of IAV in lung cells.

IMPORTANCE

Viral infections that affect the upper or lower respiratory tracts, such as IAV, rapidly induce mucin production on the epithelial surfaces of respiratory cells. However, the details of how mucin-type O-linked glycosylation is initiated by IAV infection and how mucin production affects viral replication have not yet been elucidated. In this study, we show that levels of two miRNAs that target the UDP-GalNAc transferase GALNT3 are markedly decreased during the early stage of IAV infection, resulting in the upregulation of GALNT3 mRNA. We also demonstrate that the expression of GALNT3 initiates mucin production and affects IAV replication in infected cells. This is the first report demonstrating the mechanism underlying the miRNA-mediated initiation of mucin-type O-glycosylation in IAV-infected cells and its role in viral replication. Our results have broad implications for understanding IAV replication and suggest a strategy for the development of novel anti-influenza approaches.

Overexpression of heparan sulfate 6-O-sulfotransferase-2 enhances fibroblast growth factor-mediated chondrocyte growth and differentiation

In our previous study, we reported that heparan sulfate 6-O-sulfotransferase‑2 (HS6ST2) plays an important role in the cartilage of patients with osteoarthritis and Kashin-Beck disease and that it regulates aggrecan (Acan) metabolism and the viability of chondrocytes. However, its role in chondrocyte differentiation remains poorly understood. In the present study, we aimed to investigate the role of HS6ST2 in chondrocyte differentiation in vitro using mouse prechondrocytic cells. We found that the overexpression or silencing of HS6ST2 significantly enhanced or abrogated the effects of fibroblast growth factor (FGF)‑2 on chondrocyte growth, respectively. We found that the overexpression of HS6ST2 significantly induced the expression of Acan as well as the amount of total proteoglycans in the prechondrocytic cells in the presence of FGF‑2, whereas the silencing of HS6ST2 caused the opposite effect. Furthermore, the expresssion of FGF‑2‑induced sex‑determining region Y‑type high mobility group box protein 9 (SOX9), a major transcription factor for chondrocyte proliferation and differentiation, was also enhanced or blocked by HS6ST2 overexpression or HS6ST2 knockdown, respectively. Additionally, Wnt/β‑catenin signaling, which inhibited chondrocyte proliferation and differentiation, was suppressed by HS6ST2. Taken together, these data suggest that HS6ST2 plays an important role in regulating chondrocyte growth and differentiation by modulating FGF‑2 signaling, thus indicating that it may be a potential and valuable molecular target for the treatment of skeletal dysplasias, such as dwarfism.