Homodimerization of Ror2 tyrosine kinase receptor induces 14-3-3(beta) phosphorylation and promotes osteoblast differentiation and bone formation

Ror2 receptor plays a key role in bone formation, but its signaling pathway is not completely understood. We demonstrate that Ror2 homodimerizes at the cell surface, and that dimerization can be induced by a bivalent antibody. Antibody-mediated dimerization causes receptor autophosphorylation and induces functional consequences of its signaling, including osteogenesis in mesenchymal stem cells and bone formation in organ culture. We further show that Ror2 associates with and phosphorylates 14-3-3beta scaffold protein. Endogenous Ror2 binds 14-3-3beta in U2OS osteosarcoma cells, and purified intracellular domain of Ror2 interacts with 14-3-3beta in vitro. 14-3-3beta Is tyrosine phosphorylated in U2OS cells, and this phosphorylation is inhibited by down-regulating Ror2 and enhanced by overexpressing the kinase. Purified Ror2 phosphorylates 14-3-3beta in vitro, confirming 14-3-3beta as the first identified Ror2 substrate. Down-regulating 14-3-3beta potentiates osteoblastogenesis in mesenchymal stem cells and increases bone formation in calvarial cultures, indicating that 14-3-3beta exerts a negative effect on osteogenesis. This raises a possibility that Ror2 induces osteogenic differentiation, at least in part, through a release of the 14-3-3beta-mediated inhibition. Our research forms a foundation for several new areas of investigation, including the molecular regulation of 14-3-3 by tyrosine phosphorylation and the role of this scaffold in osteogenesis.     

Modelling an outbreak of an emerging pathogen

To illustrate the usefulness of mathematical models to the microbiology and medical communities, we explain how to construct and apply a simple transmission model of an emerging pathogen. We chose to model, as a case study, a large (>8,000 reported cases) on-going outbreak of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) in the Los Angeles County Jail. A major risk factor for CA-MRSA infection is incarceration. Here, we show how to design a within-jail transmission model of CA-MRSA, parameterize the model and reconstruct the outbreak. The model is then used to assess the severity of the outbreak, predict the epidemiological consequences of a catastrophic outbreak and design effective interventions for outbreak control.     

Quantification of angiogenesis in estrogen receptor-positive and negative breast carcinoma

Background

The objective of this study was to evaluate angiogenesis according to CD34 antigen expression in estrogen receptor (ER)-positive and negative breast carcinomas.

Methods

This study comprised 64 cases of infiltrating ductal carcinoma in postmenopausal women divided into two groups: Group A: ER-positive, n = 35; and Group B: ER-negative, n = 29. The anti-CD34 monoclonal antibody was used as a marker for endothelial cells. Microvessel count was carried out in 10 fields per slide using a 40× objective lens (magnification 400×). Statistical analysis of the data was performed using Student's t-test (p < 0.05).

Results

The mean number of vessels stained with the anti-CD34 antibody in the estrogen receptor-positive and negative tumors was 23.51 ± 1.15 and 40.24 ± 0.42, respectively. The number of microvessels was significantly greater in the estrogen receptor-negative tumors (p < 0.001).

Conclusion

ER-negative tumors have significantly greater CD34 antigen expression compared to ER-positive tumors.

     

Regulation of hematopoiesis and the hematopoietic stem cell niche by Wnt signaling pathways

Hematopoietic stem cells （HSCs） are a rare population of cells that are responsible for life-long generation of blood cells of all lineages. In order to maintain their numbers, HSCs must establish a balance between the opposing cell fates of self-renewal （in which the ability to function as HSCs is retained） and initiation of hematopoietic differentiation. Multiple signaling pathways have been implicated in the regulation of HSC cell fate. One such set of pathways are those activated by the Wnt family of ligands. Wnt signaling pathways play a crucial role during embryogenesis and deregulation of these pathways has been implicated in the formation of solid tumors. Wnt signaling also plays a role in the regulation of stem cells from multiple tissues, such as embryonic, epidermal, and intestinal stem cells. However, the function of Wnt signaling in HSC biology is still controversial. In this review, we will discuss the basic characteristics of the adult HSC and its regulatory microenvironment, the ＂niche＂, focusing on the regulation of the HSC and its niche by the Wnt signaling pathways.     

Metabolic effects of low aflatoxin B1 levels on broiler chicks.

The effects of daily ingestion of aflatoxin B1 (AFB1) on growth, feed intake, plasma glucose, plasma cholesterol, plasma amino acids, plasma albumin, plasma ceruloplasmin, muscle amino acids, liver lipid, and bone strength were studied. For 3 weeks, beginning at an age of 2 days, broiler chicks were dosed daily per os with 50 or 100 micrograms of AFB1 per kg of body weight. Body weight and feed consumption were recorded daily, and metabolic responses were determined at 3 weeks. Treatment with AFB1 did not significantly alter body weight or feed intake. Relative liver weight showed a significant increase at the highest dose, with a significant concomitant increase in liver lipid and decrease in hepatic zinc. Relative spleen and heart weights were not affected by the toxin. Plasma glucose and cholesterol were significantly elevated at the highest dose. AFB1 significantly decreased plasma lysine and histidine and significantly increased muscle histidine, arginine, and valine. AFB1 decreased plasma albumin and markedly increased plasma ceruloplasmin. Dimensions of the long bones (femur and tibiotarsus) were not altered by the toxin. However, AFB1 caused a significant linear decline in the resistance of bone to breakage ("bone breaking strength"). The results indicate that low levels of AFB1 reduced bone strength in broiler chicks. The alterations in blood parameters indicated that AFB1 can disrupt metabolism even at low levels.