Obox4 regulates the expression of histone family genes and promotes differentiation of mouse embryonic stem cells

Obox genes are preferentially expressed in the ovary, testis and oocyte, and play important roles in many developmental processes. In this study, we report that Obox4 and Obox6 are expressed in mouse embryonic stem cells (mESCs) and that Obox4 regulates histone family gene expression in mESCs. Obox4 protein expressing mESCs formed colonies with a flattened and irregular morphology, and exhibited decreased expression levels of self-renewal related proteins, such as Oct4 and Sox2, as well as reduced alkaline phosphatase activity. The results of microarray analysis and siRNA mediated knockdown experiments suggest that Obox4 is an upstream regulator of the histone gene family.     

胚胎干细胞向造血干/祖细胞定向诱导分化的研究进展

胚胎干细胞(embryonic stem cell,ES细胞)是指由胚胎内细胞团(inner cell mass,ICM)细胞经体外抑制培养而筛选得到的细胞,具有无限增殖潜能,在体外可以向造血细胞分化,有可能为造血干细胞移植和血细胞输注开辟新的来源．此外,ES细胞向造血干/祖细胞的定向诱导分化也为阐明哺乳动物造血发育的细胞和分子机制提供了良好的体外模型．对ES细胞向造血干/祖细胞定向分化的研究进展进行了综述．     

Mutation and expression analysis of the IDH1, IDH2, DNMT3A, and MYD88 genes in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of death around the world. Its genetic mechanism was intensively investigated in the past decades with findings of a number of canonical oncogenes and tumor-suppressor genes such as APC, KRAS, and TP53. Recent genome-wide association and sequencing studies have identified a series of promising oncogenes including IDH1, IDH2, DNMT3A, and MYD88 in hematologic malignancies. However, whether these genes are involved in CRC remains unknown. In this study, we screened the hotspot mutations of these four genes in 305 CRC samples from Han Chinese by direct sequencing. mRNA expression levels of these genes were quantified by quantitative real-time PCR (RT-qPCR) in paired cancerous and paracancerous tissues. Association analyses between mRNA expression levels and different cancerous stages were performed. Except for one patient harboring IDH1 mutation p.I99M, we identified no previously reported hotspot mutations in colorectal cancer tissues. mRNA expression levels of IDH1, DNMT3A, and MYD88, but not IDH2, were significantly decreased in the cancerous tissues comparing with the paired paracancerous normal tissues. Taken together, the hotspot mutations of IDH1, IDH2, DNMT3A, and MYD88 gene were absent in CRC. Aberrant mRNA expression of IDH1, DNMT3A, and MYD88 gene might be actively involved in the development of CRC.     

Laminin-511 expression is associated with the functionality of feeder cells in human embryonic stem cell culture

Fibroblast feeder cells play an important role in supporting the derivation and long term culture of undifferentiated, pluripotent human embryonic stem cells (hESCs). The feeder cells secrete various growth factors and extracellular matrix (ECM) proteins into extracellular milieu. However, the roles of the feeder cell-secreted factors are largely unclear. Animal feeder cells and use of animal serum also make current feeder cell culture conditions unsuitable for derivation of clinical grade hESCs. We established xeno-free feeder cell lines using human serum (HS) and studied their function in hESC culture. While human foreskin fibroblast (hFF) feeder cells were clearly hESC supportive, none of the established xeno-free human dermal fibroblast (hDF) feeder cells were able to maintain undifferentiated hESC growth. The two fibroblast types were compared for their ECM protein synthesis, integrin receptor expression profiles and key growth factor secretion. We show that hESC supportive feeder cells produce laminin-511 and express laminin-binding integrins α3ß1, α6ß1 and α7ß1. These results indicate specific laminin isoforms and integrins in maintenance of hESC pluripotency in feeder-dependent cultures. In addition, several genes with a known or possible role for hESC pluripotency were differentially expressed in distinct feeder cells.     

Chemical and physical stimuli induce cardiomyocyte differentiation from stem cells

In this study we investigated cardiomyocyte differentiation of rat bone marrow-mesenchymal stem cells (BM-MSCs) by treating the stem cells with conditions mimicking that of myocardial infarction. The extract from infarcted rat myocardium contained the biochemical factors arising after infarction. The cardiac contraction and relaxation were simulated by applying 4% strain at 1 Hz to the stem cells. We found that the extract from infarcted myocardium or 4% strain each alone could induce cardiomyocyte differentiation of BM-MSCs, as shown by expression of cardiomyocyte-specific genes including α-actin, connexin 43, Nkx2.5, MEF2c, GATA4, α-MHC, and Troponin I. Furthermore, a combination of the extract and 4% strain had stronger effects on cardiomyocyte differentiation than what either treatment alone had. Our results suggest that this in vitro model system simulates the local cardiac environment cues after infarction and may be useful in identifying the biochemical and physical factors involved in cardiomyocyte differentiation.     

Evidence of expression variation and allelic imbalance in Crohn's disease susceptibility genes NOD2 and ATG16L1 in human dendritic cells

Human dendritic cells (DCs) play an important role in induction and progression of Crohn's disease (CD). Accumulating evidence suggests that viral infection is required to trigger CD pathogenesis in genetically predisposed individuals. NOD2 and ATG16L1 are among the major CD susceptibility genes implicated in impaired immune response to bacterial infection. In this study, we investigated gene expression and allelic imbalance (AI) of NOD2 and ATG16L1 using common variants in human monocyte-derived DCs. Significant AI was observed in ~ 40% and ~ 70% of NOD2 and ATG16L1 heterozygotes, respectively (p < 0.05). AI of NOD2 was inversely associated with its expression level (p = 0.015). No correlation was detected between gene expression and AI for ATG16L1. When infected with Newcastle Disease Virus (NDV), NOD2 expression in DCs was induced about four-fold (p < 0.001), whereas ATG16L1 expression was not affected (p = 0.88). In addition, NDV infection tended to lower the variance in AI among DC populations for the NOD2 gene (p = 0.05), but not the ATG16L1 gene (p = 0.32). Findings of a simulation study, aimed to verify whether the observed variation in gene expression and AI is a result of sample-to-sample variability or experimental measurement error, suggested that NOD2 AI is likely to result from a deterministic event at a single cell level. Overall, our results present initial evidence that AI of the NOD2 and ATG16L1 genes exists in populations of human DCs. In addition, our findings suggest that viral infection may regulate NOD2 expression.     

Null genotypes of GSTM1 and GSTT1 contribute to increased risk of diabetes mellitus: A meta-analysis

Diabetes mellitus (DM) is a common disease which results from various causes including genetic and environmental factors. Glutathione S-Transferase M1 (GSTM1) and Glutathione S-Transferase T1 (GSTT1) genes are polymorphic in human and the null genotypes lead to the absence of enzyme function. Many studies assessed the associations between GSTM1/GSTT1 null genotypes and DM risk but reported conflicting results. In order to get a more precise estimate of the associations of GSTM1/GSTT1 null genotypes with DM risk, we performed this meta-analysis. Published literature from PubMed, Embase and China Biology Medicine (CBM) databases was searched for eligible studies. Pooled odds ratios (OR) and corresponding 95% confidence intervals (95%CI) were calculated using a fixed- or random-effects model. 11 publications (a total of 2577 cases and 4572 controls) were finally included into this meta-analysis. Meta-analyses indicated that null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 were all associated with increased risk of DM (GSTM1: OR _{random-effects} = 1.60, 95%CI 1.10–2.34, P_OR = 0.014; GSTT1: OR _{random-effects} = 1.47, 95%CI 1.12–1.92, P_OR = 0.005; GSTM1–GSTT1: OR _{fixed-effects} = 1.83, 95%CI 1.30–2.59, P_OR = 0.001). Subgroup by ethnicity suggested significant associations between null genotypes of GSTM1 and GSTT1 and DM risk among Asians (GSTM1: OR _{random-effects} = 1.77, 95%CI 1.24–2.53, P_OR = 0.002; GSTT1: OR _{random-effects} = 1.58, 95%CI 1.09–2.27, P_OR = 0.015). This meta-analysis suggests null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 are all associated with increased risk of DM, and null genotypes of GSTM1/GSTT1 and dual null genotype of GSTM1–GSTT1 are potential biomarkers of DM.     

Simvastatin coating of TiO2 scaffold induces osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells

Bone tissue engineering requires an osteoconductive scaffold, multipotent cells with regenerative capacity and bioactive molecules. In this study we investigated the osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells (hAD-MSCs) on titanium dioxide (TiO₂) scaffold coated with alginate hydrogel containing various concentrations of simvastatin (SIM). The mRNA expression of osteoblast-related genes such as collagen type I alpha 1 (COL1A1), alkaline phosphatase (ALPL), osteopontin (SPP1), osteocalcin (BGLAP) and vascular endothelial growth factor A (VEGFA) was enhanced in hAD-MSCs cultured on scaffolds with SIM in comparison to scaffolds without SIM. Furthermore, the secretion of osteoprotegerin (OPG), vascular endothelial growth factor A (VEGFA), osteopontin (OPN) and osteocalcin (OC) to the cell culture medium was higher from hAD-MSCs cultured on scaffolds with SIM compared to scaffolds without SIM. The TiO₂ scaffold coated with alginate hydrogel containing SIM promote osteogenic differentiation of hAD-MSCs in vitro, and demonstrate feasibility as scaffold for hAD-MSC based bone tissue engineering.     

Atlantic salmon (Salmo salar) muscle precursor cells differentiate into osteoblasts in vitro: Polyunsaturated fatty acids and hyperthermia influence gene expression and differentiation

The formation and mineralisation of bone are two critical processes in fast-growing Atlantic salmon (Salmo salar). The mechanisms of these processes, however, have not been described in detail. Thus, in vitro systems that allow the study of factors that influence bone formation in farmed Atlantic salmon are highly warranted. We describe here a method by which unspecialised primary cells from salmon white muscle can differentiate to osteoblasts in vitro. We have subsequently used the differentiated cells as a model system to study the effects of two factors that influence bone formation in Atlantic salmon under commercial farming conditions, namely polyunsaturated fatty acids, PUFAs, and temperature. Muscle precursor cells changed their morphology from triangular or spindle-shaped cells to polygonal or cubical cells after 3 weeks in osteogenic medium. In addition, gene expression studies showed that marker genes for osteoblastogenesis; alp, col1a1, osteocalcin, bmp2 and bmp4 increased after 3 weeks of incubation in osteogenic media showing that these cells have differentiated to osteoblasts at this stage. Adding CLA or DHA to the osteoblast media resulted in a reduced PGE₂ production and increased expression of osteocalcin. Further, temperature studies showed that differentiating osteoblasts are highly sensitive to increased incubation temperature at early stages of differentiation. Our studies show that unspecialised precursor cells isolated from salmon muscle tissue can be caused to differentiate to osteoblasts in vitro. Furthermore, this model system appears to be suitable for the study of osteoblast biology in vitro.