Project description:Obesity is associated with an increase in β-cell mass in response to the rising demand for insulin. β-cell plasticity is essential to maintaining glucose homeostasis, however, the cellular and molecular mechanisms by which β-cell mass is regulated remain poorly understood. Recently, we described the existence of a crosstalk between the peripancreatic adipose tissue and β-cells as a novel mechanism that participates in the regulation of β-cell plasticity. Here, we identify the secreted frizzled-related protein (Sfrp) 5 as down-regulated in the pancreatic islets of obese rats as well as in the pancreatic islets of human obese patients. Our results demonstrate that the silencing of Sfrp5 induces an increase in β-cell proliferation, which we correlate with the activation of Wnt signaling and of the MAPK and PI3 kinase pathways. Together, these findings expand our understanding of the mechanisms underlying β-cell proliferation under conditions of obesity. Furthermore, this study opens new insights into the specific targeting of Sfrp5 as a novel therapeutic strategy for balancing β-cell mass. Adult male Wistar rats (Charles River Laboratories, Wilmington, MA), 7 wk old (weighing 225–250 g), were caged individually in a 12-h light, 12-h dark cycle in a temperature- and humidity-controlled environment. Animals were divided into two dietary sets for 10 days. One group was fed with standard chow diet (supplying 8% of calories as fat; type AO4 from Panlab, Barcelona, Spain). The second group was fed with a cafeteria diet (66% of calories as fat), as previously described (Endocrinology 2012;153:177-87). Pancreatic islets were isolated through collagenase perfusion of the pancreas, Histopaque gradient and hand-picking under microscopic guidance. Ten micrograms of total RNA from islets were converted into cRNA, biotinylated, fragmented, and hybridized to GeneChip Rat Genome 230 2.0 (Affymetrix, Santa Clara, CA). Ten microarrays were hybridized, five with independent samples coming from rats fed with standard chow (lean group) and five with independent samples coming from rats fed with the cafeteria diet (obese group).

Project description:Multiple miliary osteoma cutis (MMOC) is a rare skin disorder characterized by heterotopic ossification in dermis and subcutis. The etiology and disease mechanism is unknown, but earlier data indicates that it seems to be different from other diseases containing heterotopic intramembranous ossification. The purpose of this study was to further investigate the pathogenesis of MMOC by comparing patients’ osteoma affected skin area to their unaffected healthy skin area, as well as to skin from controls. This comparison was made by using osteogenic differentiation studies in cell cultures and by gene expression experiments. Both patient and control dermal fibroblast-like cells were able to differentiate into osteoblast-like matrix mineralizing cells. The differentiation seems to diminish with bone morphogenetic protein (BMP) 4 and 2/7 exposures and seems to correlate with proportion of stem cell associated cell surface marker CD105 positive cells. Microarray analysis revealed altered gene expression patterns between skin samples of patients and controls, as well as between samples taken from different skin areas. BMP receptor II and G-protein α-stimulatory subunit genes were among downregulated and β-catenin among upregulated genes in patient compared to control samples. Genes for homeobox proteins were among downregulated and gene for secreted frizzled related protein 2 among upregulated genes when compared patients’ osteoma area to their unaffected area. Differences in unaffected skin area in patients and controls suggest that the nature of MMOC may be more systemic than previously thought. Detected differences in separate skin areas may, in turn, provide new information for understanding the localized characteristics of MMOC. BMPs’ inhibitory effect to osteogenic differentiation of human dermal fibroblast-like cells may provide a new perspective to the clinical use of BMPs. Skin biopsies were taken from three patients and two controls for RNA extraction and hybridization on Affymetrix microarrays.

Project description:Sivakumar2011_WntSignalingPathway The secreted protein Wnt activates the heptahelical receptor Frizzled on nieghboring cells. Activation of Frizzled causes the recruitment of additional membrane proteins which in turn result in 1) the activation of the protein Dishevelled via phosphorylation and 2) the activation of a heterotrimeric G protein of unknown type. Activation of Dishevelled results in the down-regulation of the Beta-Catenin destruction complex which causes ubiquitination of Beta-Catenin and its ultimate degradation via the proteasome. Inhibition of the Beta-Catenin destruction complex yields a higher cytosolic concentration of Beta-Catenin, which enters the nucleus, binds various transcriptional regulatory molecules including the TCF/LEF class of proteins, and results in the transcription of TCF/LEF target genes. Activation of the heterotrimeric G-protein pathway in turn activates Phospholipase C which in turn catalyzes the catalysis of PI(4,5)P2 into DAG and IP3. Reference: The Wnt signalling pathway. You Wnt some, you lose some: oncogenes in the Wnt signaling pathway. Wnt signaling pathway. This model is described in the article: A systems biology approach to model neural stem cell regulation by notch, shh, wnt, and EGF signaling pathways. Sivakumar KC, Dhanesh SB, Shobana S, James J, Mundayoor S. OMICS 2011 Oct; 15(10): 729-737 Abstract: The Notch, Sonic Hedgehog (Shh), Wnt, and EGF pathways have long been known to influence cell fate specification in the developing nervous system. Here we attempted to evaluate the contemporary knowledge about neural stem cell differentiation promoted by various drug-based regulations through a systems biology approach. Our model showed the phenomenon of DAPT-mediated antagonism of Enhancer of split [E(spl)] genes and enhancement of Shh target genes by a SAG agonist that were effectively demonstrated computationally and were consistent with experimental studies. However, in the case of model simulation of Wnt and EGF pathways, the model network did not supply any concurrent results with experimental data despite the fact that drugs were added at the appropriate positions. This paves insight into the potential of crosstalks between pathways considered in our study. Therefore, we manually developed a map of signaling crosstalk, which included the species connected by representatives from Notch, Shh, Wnt, and EGF pathways and highlighted the regulation of a single target gene, Hes-1, based on drug-induced simulations. These simulations provided results that matched with experimental studies. Therefore, these signaling crosstalk models complement as a tool toward the discovery of novel regulatory processes involved in neural stem cell maintenance, proliferation, and differentiation during mammalian central nervous system development. To our knowledge, this is the first report of a simple crosstalk map that highlights the differential regulation of neural stem cell differentiation and underscores the flow of positive and negative regulatory signals modulated by drugs. This model is hosted on BioModels Database and identified by: BIOMD0000000397. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

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