Project description:Scoliosis is a common disorder, affecting one out of every twenty females. Some forms of scoliosis are congenital, resulting from disruptions in early spinal development. The spinal column is patterned during a cycling process called somitogenesis, and is the first musculoskeletal structure formed during development. Genes in the notch signaling pathway regulate somitogenesis, and display oscillatory expression in synchrony with somite formation. During somitogenesis, oscillatory expression of genes in the notch and wnt signaling pathways plays a key role in regulating segmentation. These oscillations in expression levels are elements of a species-specific developmental mechanism. The periodicity and components of the human clock have recently been described by our group (William et al., Dev Biol, 2007). In that publication, we showed that a human mesenchymal stem/stromal cell (MSC) model can be induced to display oscillatory gene expression, including known cycling genes such as HES1 that displayed a period of 5 hours. We also observed cycling of Hes1 expression in mouse C2C12 myoblasts with a period of 2 hours, consistent with previous in vitro and embryonic studies. Furthermore, we used microarray and quantitative PCR (Q-PCR) analysis to identify additional genes that display oscillatory expression both in vitro and in mouse embryos. We confirmed oscillatory expression of the notch pathway gene Maml3 and the wnt pathway gene Nkd2 by whole mount in situ hybridization analysis and Q-PCR. Studies in mouse cell lines, including fibroblasts and PC12 neuronal cells, by R. Kageyema (Kyoto University, Hirata et al., Science, 2002) have shown that a number of mouse cell types can be synchronized to display oscillatory expression. In this study, we extend our analysis of human cells to human primary fibroblasts. Developing an in vitro model of somitogenesis using human mesenchymal stem cells and fibroblasts; a. Induce cycling gene expression in human mesenchymal stem cells (MSC) and fibroblasts and identify oscillatory genes (using Affymetrix U133 GeneChipsÂ®). Compare lists of oscillatory genes identified in these two human cell types. b. Characterize and validate mouse homologues of oscillatory genes for expression during somitogenesis. Using notch and wnt pathway mutants and cultured half embryos, determine if these oscillatory genes also display cycling expression during somitogenesis. We hypothesized that human fibroblasts could be synchronized to display oscillatory expression of notch and wnt pathway genes, including the marker gene HES1. Preliminary quantitative analysis by Taqman-based Real-Time PCR for these samples confirms that HES1 expression displays oscillatory expression. Homo sapiens fibroblasts were maintained in culture medium (DMEM high glucose with 10% fetal bovine serum, FBS), which was replaced twice weekly. The cells were then seeded at a density of 6,000-10,000 cells/cm2 and expanded in DMEM high glucose with 10% FBS. After 5-7 days of incubation at 37C in a humidified atmosphere containing 5% carbon dioxide, cells were detached with 0.05% trypsin for 2 minutes at confluency. Cells were synchronized using low serum treatment, which has been described previously for Hes1 (Hirata et al., 2002). Cell culture synchronization is required to assay oscillatory expression levels, otherwise the oscillations of individual cells would be out of phase and cancel one another. Synchronized cells will gradually desynchronize, leading to diminished oscillatory amplitude. Briefly, synchronization was carried out as follows: T-25 cm flasks were set up in parallel. These cells were grown to 90% confluence in DMEM supplemented with 10% FBS (UCB-MSC), then incubated in DMEM with only 0.2% FBS for 24 hours, and returned to DMEM supplemented with FBS. Samples were collected at 1 hr. intervals from 0 to 12 hours. In addition, an unsynchronized cell culture was sampled. Total RNA was isolated from cells in culture using the RNeasy Mini Kit (Qiagen) and quantitated using a Nanodrop 2000. Experiment Overall Design: A biological replicate of the submitted project (hCycle11) time-series was carried out in parallel has been collected (hCycle12). We have evaluated both biological replicates by Q-PCR. We have selected hCycle11 for HG-U133A Plus 2.0 analysis, and we reserve hCycle12 for possible future microarray analysis or comparison by Q-PCR.

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Mus musculus

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