Role of the RUNX2 p.R225Q mutation in cleidocranial dysplasia: a rare presentation and an analysis of the RUNX2 protein structure

Cleidocranial dysplasia (CCD; MIM 119600) is an autosomal dominant hereditary disorder of skeletal features whose characteristic clinical symptoms are caused by mutations in the RUNX2 gene. Varying degrees of clavicular hypoplasia and dental abnormalities are the most prominent features of this disorder. In this study, we presented a Chinese family that included 4 individuals with a p.R225Q mutation in the RUNX2 gene and characteristic CCD phenotypes. Through structural analysis of the p.R225Q mutation in the RUNX2 protein, we determined that the location of this mutation has the potential to affect DNA binding by RUNX2. The proband in this CCD-affected family showed a specific clinical phenotype of CCD that included a median pseudo-cleft palate, which is a presentation of this mutation that has not been reported previously. On the basis of the structural analysis, this study further demonstrated that the p.R225Q mutation abolished DNA binding by RUNX2 and its results also suggested that other genetic and/or environmental factors could affect the CCD phenotypes.

MEAT SCIENCE AND MUSCLE BIOLOGY SYMPOSIUM--mechanism of growth hormone stimulation of skeletal muscle growth in cattle

Growth hormone, also called somatotropin (ST), is a polypeptide hormone produced by the anterior pituitary. The major functions of GH include stimulating bone and skeletal muscle growth, lipolysis, milk production, and expression of the IGF-I gene in the liver. Based on these functions, recombinant bovine ST (bST) and recombinant porcine ST (pST) have been used to improve milk production in dairy cows and lean tissue growth in pigs, respectively. However, despite these applications, the mechanisms of action of GH are not fully understood. Indeed, there has been a lot of controversy over the role of liver-derived circulating IGF-I and locally produced IGF-I in mediating the growth-stimulatory effect of GH during the last 15 yr. It is in this context that we have conducted studies to further understand how GH stimulates skeletal muscle growth in cattle. Our results do not support a role of skeletal muscle-derived IGF-I in GH-stimulated skeletal muscle growth in cattle. Our results indicate that GH stimulates skeletal muscle growth in cattle, in part, by stimulating protein synthesis in muscle through a GH receptor-mediated, IGF-I-independent mechanism. In this review, besides discussing these results, we also argue that liver-derived circulating IGF-I should be still considered as the major mechanism that mediates the growth-stimulatory effect of GH on skeletal muscle in cattle and other domestic animals.

Impact of wave front and coherence optimization in coherent diffractive imaging

We present single shot nanoscale imaging using a table-top femtosecond soft X-ray laser harmonic source at a wavelength of 32 nm. We show that the phase retrieval process in coherent diffractive imaging critically depends on beam quality. Coherence and image fidelity are measured from single-shot coherent diffraction patterns of isolated nano-patterned slits. Impact of flux, wave front and coherence of the soft X-ray beam on the phase retrieval process and the image quality are discussed. After beam improvements, a final image reconstruction is presented with a spatial resolution of 78 nm (half period) in a single 20 fs laser harmonic shot.

Metadherin contributes to the pathogenesis of diffuse large B-cell lymphoma

Background

Metadherin (MTDH) has been demonstrated as a potentially crucial mediator of various types of human malignancies. However, the expression and role of MTDH in diffuse large-B-cell lymphoma (DLBCL) have not been reported yet. This study aimed to illuminate the role of MTDH in the pathogenesis of DLBCL.

Methodology/Principal Findings

A remarkable elevation of MTDH on mRNA level was detected in DLBCL tissues by quantitative polymerase chain reaction (PCR). Using Western-blot analysis we found that the expression of MTDH protein was significantly upregulated in DLBCL cell lines and DLBCL tissues compared with peripheral blood mononuclear cells (PBMCs) from healthy samples and tissues from patients of reactive hyperplasia of lymph node. The results showed high expression of MTDH in 23 of 30 (76.67%) DLBCL tissues by using immunohistochemical analysis and the over expression of MTDH was strongly correlated to the clinical staging of patients with DLBCL (P<0.05). Furthermore, the finding suggested that the increase of MTDH in DLBCL cells could distinctly enhance cell proliferation and inhibit cell apoptosis; meanwhile, inhibition of MTDH expression by specific siRNA clearly enhanced LY8 cell apoptosis. Upregulation of MTDH elevated the protein level of total β-catenin and translocation of β-catenin to the nucleus directly or indirectly. Knockdown of MTDH decreased the level of total, cytoplasmic β-catenin and reduced nuclear accumulation of β-catenin protein. This indicated that the function of MTDH on the development of DLBCL was mediated through regulation of Wnt/β-catenin signaling pathway.

Conclusions/Significance

Our results suggest that MTDH contributes to the pathogenesis of DLBCL mediated by activation of Wnt/β-catenin pathway. This novel study may contribute to further investigation on the useful biomarkers and potential therapeutic target in the DLBCL patients.

High expression and nuclear localization of β-catenin in diffuse large B-cell lymphoma

The Wnt/β-catenin signaling pathway plays diverse roles in embryonic development and maintenance of organs and tissues in adults as well as in the pathogenesis of a range of diseases, including many types of carcinomas. β-catenin, the principal downstream effector of the Wnt/β-catenin pathway, migrates to the nucleus and mediates the activation of the Wnt/β-catenin pathway. The aim of the present study was to investigate the expression and localization of β-catenin in diffuse large B-cell lymphoma (DLBCL) tissues and to illuminate the role of β-catenin in the pathogenesis of DLBCL. The mRNA expression levels of β-catenin were determined by quantitative polymerase chain reaction (PCR), while β-catenin protein levels were detected by western blot analysis and immunohistochemical staining. DLBCL showed a higher expression of β-catenin in contrast to reactive hyperplasia of lymph node tissues at both the mRNA and protein levels (P<0.001). Immunohistochemical analysis indicated nuclear localization of β-catenin in 14 (46.67%) DLBCL cases, whereas no inflammatory lymph node tissue showed nuclear accentuation of β-catenin. The overexpression and nuclear accentuation of β-catenin were strongly correlated to the clinical staging of patients with DLBCL (P<0.05). These results suggest that the Wnt/β-catenin pathway is partly activated in DLBCL and may contribute to its pathogenesis.

Donor age-specific injury and immune responses

Utilization rates of organs from elderly donors have shown the highest proportional increase during the last decade. Clinical reports support the concept of transplanting older organs. However, the engraftment of such organs has been linked to accelerated immune responses based on ageing changes per se and a proinflammatory environment subsequent to compromised injury and repair mechanism. We analyzed the clinical consequences of transplanting older donor organs and present mechanistic aspects correlating age, injury repair and effects on host immunoresponsiveness.

Inhibition of myostatin protects against diet-induced obesity by enhancing fatty acid oxidation and promoting a brown adipose phenotype in mice

AIMS/HYPOTHESIS

Although myostatin-null (Mstn (-/-)) mice fail to accumulate fat in adipose tissue when fed a high-fat diet (HFD), little is known about the molecular mechanism(s) behind this phenomenon. We therefore sought to identify the signalling pathways through which myostatin regulates accumulation and/or utilisation of fat.

METHODS

Wild-type, Mstn (-/-) and wild-type mice treated with soluble activin type IIB receptor (sActRIIB) were fed a control chow diet or an HFD for 12 weeks. Changes in gene expression were measured by microarray and quantitative PCR. Histological changes in white adipose tissue were assessed together with peripheral tissue fatty acid oxidation and changes in circulating hormones following HFD feeding.

RESULTS

Our results demonstrate that inactivation of myostatin results in reduced fat accumulation in mice on an HFD. Molecular analysis revealed that metabolic benefits, due to lack of myostatin, are mediated through at least two independent mechanisms. First, lack of myostatin increased fatty acid oxidation in peripheral tissues through induction of enzymes involved in lipolysis and in fatty acid oxidation in mitochondria. Second, inactivation of myostatin also enhanced brown adipose formation in white adipose tissue of Mstn (-/-) mice. Consistent with the above, treatment of HFD-fed wild-type mice with the myostatin antagonist, sActRIIB, reduced the obesity phenotype.

CONCLUSIONS/INTERPRETATION

We conclude that absence of myostatin results in enhanced peripheral tissue fatty acid oxidation and increased thermogenesis, culminating in increased fat utilisation and reduced adipose tissue mass. Taken together, our data suggest that anti-myostatin therapeutics could be beneficial in alleviating obesity.

Growth hormone stimulates protein synthesis in bovine skeletal muscle cells without altering insulin-like growth factor-I mRNA expression

Growth hormone is a major stimulator of skeletal muscle growth in animals, including cattle. In this study, we determined whether GH stimulates skeletal muscle growth in cattle by direct stimulation of proliferation or fusion of myoblasts, by direct stimulation of protein synthesis, or by direct inhibition of protein degradation in myotubes. We also determined whether these direct effects of GH are mediated by IGF-I produced by myoblasts or myotubes. Satellite cells were isolated from cattle skeletal muscle and were allowed to proliferate as myoblasts or induced to fuse into myotubes in culture. Growth hormone at 10 and 100 ng/mL increased protein synthesis in myotubes (P < 0.05), but had no effect on protein degradation in myotubes or proliferation of myoblasts (P > 0.05). Insulin-like growth factor-I at 50 and 500 ng/mL stimulated protein synthesis (P < 0.01), and this effect of IGF-I was much greater than that of GH (P < 0.05). Besides stimulating protein synthesis, IGF-I at 50 and 500 ng/mL also inhibited protein degradation in myotubes (P < 0.01), and IGF-I at 500 ng/mL stimulated proliferation of myoblasts (P < 0.05). Neither GH nor IGF-I had effects on fusion of myoblasts into myotubes (P > 0.1). These data indicate that GH and IGF-I have largely different direct effects on bovine muscle cells. Growth hormone at 10 and 100 ng/mL had no effect on IGF-I mRNA expression in either myoblasts or myotubes (P > 0.1). This lack of effect was not because the cultured myoblasts or myotubes were not responsive to GH; GH receptor mRNA was detectable in them and the expression of the cytokine-inducible SH2-containing protein (CISH) gene, a well-established GH target gene, was increased by GH in bovine myoblasts (P < 0.05). Overall, the data suggest that GH stimulates skeletal muscle growth in cattle in part through stimulation of protein synthesis in the muscle and that this stimulation is not mediated through increased IGF-I mRNA expression in the muscle.

Identification and characterization of the cysteine protease inhibitor gene MdCPI from Musca domestica

Cysteine proteinase inhibitors (CPIs) are involved in many vital cellular processes such as signalling pathways, apoptosis, immune response and development; however, no CPIs have yet been reported from the housefly Musca domestica. Here we report the isolation and characterization of a housefly CPI gene designated MdCPI. The gene contains an open reading frame of 357 bp encoding a protein of 118 amino acid residues with a putative signal peptide of 17 amino acid residues. Protein alignment demonstrated a high homology to that of Sarcophaga crassipalpis (identity = 51%). Phylogenetic analysis suggested that all CPIs from dipterans, including the housefly, belong to the I25A family and may be descended from a single common ancestor. The gene was expressed in and purified from Escherichia coli. Biochemical studies showed that MdCPI exerts an inhibiting function on papain, which is a classical assay to confirm CPIs. Real-time quantitative PCR and immunolocalization analysis revealed that MdCPI is specifically expressed in haemocytes and fat bodies. It is highly down-regulated in larvae and markedly up-regulated in the pupal stage, suggesting that it may be related to development.

Myostatin-deficient mice exhibit reduced insulin resistance through activating the AMP-activated protein kinase signalling pathway

AIMS/HYPOTHESIS

Myostatin-null mice (Mstn(-/-)) have reduced body fat and increased tolerance to glucose. To date the molecular mechanisms through which myostatin regulates body fat content and insulin sensitivity are not known. Therefore, the aim of the current study was to identify signalling pathways through which myostatin regulates insulin sensitivity.

METHODS

Wild-type (WT) mice and Mstn(-/-) mice were fed either a control chow diet or a high fat diet (HFD) for 12 weeks. Glucose tolerance testing and insulin stimulated glucose uptake by M. extensor digitorum longus (EDL) were used as variables to determine insulin sensitivity. Quantitative PCR, Western blotting and enzyme assays were used to monitor AMP-activated protein kinase (AMPK) levels and activity.

RESULTS

Mstn(-/-) mice exhibited reduced fat accumulation and peripheral insulin resistance when compared with WT mice, even when they were fed an HFD. Furthermore, treatment with a myostatin antagonist also increased insulin sensitivity during HFD. Consistent with increased insulin sensitivity, we also detected elevated levels of GLUT4, AKT, p-AKT and insulin receptor substrate-1 in Mstn(-/-) muscles. Molecular analysis showed that there is increased expression and activity of AMPK in Mstn(-/-) muscles. Furthermore, we also observed an increase in the AMPK downstream target genes, Sirt1 and Pgc-1α (also known as Ppargc1a), in skeletal muscle of Mstn(-/-) mice.

CONCLUSIONS/INTERPRETATION

We conclude that myostatin inactivation leads to increased AMPK levels and activity resulting in increased insulin sensitivity of skeletal muscle. We propose that, by regulating AMPK in skeletal muscle and adipose tissues, myostatin plays a major role in regulating insulin signalling.

Interruption of the denitrification pathway influences cell growth and magnetosome formation in Magnetospirillum magneticum AMB-1

AIMS

Intracellular magnetosome synthesis in magnetotactic bacteria has been proposed to be a process involving functions of a variety of proteins. To learn more about the genetic control that is involved in magnetosome formation, nonmagnetic mutants are screened and characterized.

METHODS AND RESULTS

Conjugation-mediated transposon mutagenesis was applied to screen for nonmagnetic mutants of Magnetospirillum magneticum AMB-1 that were unable to respond to the magnetic field. A mutant strain with disruption of a gene locus encoding nitric oxide reductase was obtained. Growth and magnetosome formation under different conditions were further characterized.

CONCLUSIONS

Interruption of denitrification by inactivating nitric oxide reductase was responsible for the compromised growth and magnetosome formation in the mutant with shorter intracellular chains of magnetite crystals than those of wild-type cells under anaerobic conditions. Nevertheless, the mutant displayed apparently normal growth in aerobic culture.

SIGNIFICANCE AND IMPACT OF THE STUDY

Efficient denitrification in the absence of oxygen is not only necessary for maintaining cell growth but may also be required to derive sufficient energy to mediate the formation of magnetosome vesicles necessary for the initiation or activation of magnetite formation.

Physiological and molecular characterization of genetic competence in Streptococcus sanguinis

Streptococcus sanguinis is a major component of the oral flora and an important cause of infective endocarditis. Although S. sanguinis is naturally competent, genome sequencing has suggested significant differences in the S. sanguinis competence system relative to those of other streptococci. An S. sanguinis mutant possessing an in-frame deletion in the comC gene, which encodes competence-stimulating peptide (CSP), was created. Addition of synthetic CSP induced competence in this strain. Gene expression in this strain was monitored by microarray analysis at multiple time-points from 2.5 to 30 min after CSP addition, and verified by quantitative reverse transcription-polymerase chain reaction. Over 200 genes were identified whose expression was altered at least two-fold in at least one time point, with the majority upregulated. The 'late' response was typical of that seen in previous studies. However, comparison of the 'early' response in S. sanguinis with that of other oral streptococci revealed unexpected differences with regard to the number of genes induced, the nature of those genes, and their putative upstream regulatory sequences. Streptococcus sanguinis possesses a comparatively limited early response, which may define a minimal streptococcal competence regulatory circuit.

Spectral graph analysis of modularity and assortativity

Expressions and bounds for Newman's modularity are presented. These results reveal conditions for or properties of the maximum modularity of a network. The influence of the spectrum of the modularity matrix on the maximum modularity is discussed. The second part of the paper investigates how the maximum modularity, the number of clusters, and the hop count of the shortest paths vary when the assortativity of the graph is changed via degree-preserving rewiring. Via simulations, we show that the maximum modularity increases, the number of clusters decreases, and the average hop count and the effective graph resistance increase with increasing assortativity.

Role of Wnt canonical pathway in hematological malignancies

Wnt canonical signaling pathway plays a diverse role in embryonic development and maintenance of organs and tissues in adults. It has been observed that Wnt/β-catenin signaling pathway is involved in the pathogenesis of many carcinomas. Moreover, Wnt/β-catenin pathway has been revealed to be associated with angiogenesis. Wnt canonical pathway signaling has great potential as a therapeutic target. It has been disclosed that some hematological malignancies, such as chronic lymphocytic leukemia, mantle cell lymphoma, may occur partly due to the constitutive activation of Wnt canonical signaling pathway. This review will summarize the latest development in Wnt canonical signaling pathway and its roles in tumorigenesis and angiogenesis.