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Identification of mechanosensitive genes during skeletal development: alteration of genes associated with cytoskeletal rearrangement and cell signalling pathways.

ABSTRACT: Mechanical stimulation is necessary for regulating correct formation of the skeleton. Here we test the hypothesis that mechanical stimulation of the embryonic skeletal system impacts expression levels of genes implicated in developmentally important signalling pathways in a genome wide approach. We use a mutant mouse model with altered mechanical stimulation due to the absence of limb skeletal muscle (Splotch-delayed) where muscle-less embryos show specific defects in skeletal elements including delayed ossification, changes in the size and shape of cartilage rudiments and joint fusion. We used Microarray and RNA sequencing analysis tools to identify differentially expressed genes between muscle-less and control embryonic (TS23) humerus tissue.We found that 680 independent genes were down-regulated and 452 genes up-regulated in humeri from muscle-less Spd embryos compared to littermate controls (at least 2-fold; corrected p-value ?0.05). We analysed the resulting differentially expressed gene sets using Gene Ontology annotations to identify significant enrichment of genes associated with particular biological processes, showing that removal of mechanical stimuli from muscle contractions affected genes associated with development and differentiation, cytoskeletal architecture and cell signalling. Among cell signalling pathways, the most strongly disturbed was Wnt signalling, with 34 genes including 19 pathway target genes affected. Spatial gene expression analysis showed that both a Wnt ligand encoding gene (Wnt4) and a pathway antagonist (Sfrp2) are up-regulated specifically in the developing joint line, while the expression of a Wnt target gene, Cd44, is no longer detectable in muscle-less embryos. The identification of 84 genes associated with the cytoskeleton that are down-regulated in the absence of muscle indicates a number of candidate genes that are both mechanoresponsive and potentially involved in mechanotransduction, converting a mechanical stimulus into a transcriptional response.This work identifies key developmental regulatory genes impacted by altered mechanical stimulation, sheds light on the molecular mechanisms that interpret mechanical stimulation during skeletal development and provides valuable resources for further investigation of the mechanistic basis of mechanoregulation. In particular it highlights the Wnt signalling pathway as a potential point of integration of mechanical and molecular signalling and cytoskeletal components as mediators of the response.

SUBMITTER: Rolfe RA

PROVIDER: S-EPMC3905281 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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Identification of mechanosensitive genes during skeletal development: alteration of genes associated with cytoskeletal rearrangement and cell signalling pathways.

Rolfe Rebecca A RA Nowlan Niamh C NC Kenny Elaine M EM Cormican Paul P Morris Derek W DW Prendergast Patrick J PJ Kelly Daniel D Murphy Paula P

BMC genomics 20140120

<h4>Background</h4>Mechanical stimulation is necessary for regulating correct formation of the skeleton. Here we test the hypothesis that mechanical stimulation of the embryonic skeletal system impacts expression levels of genes implicated in developmentally important signalling pathways in a genome wide approach. We use a mutant mouse model with altered mechanical stimulation due to the absence of limb skeletal muscle (Splotch-delayed) where muscle-less embryos show specific defects in skeletal ...[more]

PMID: 24443808

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Project description:Although it is known that mechanical forces are needed for normal bone development, the current understanding of how biophysical stimuli are interpreted by and integrated with genetic regulatory mechanisms is limited. Mechanical forces are thought to be mediated in cells by "mechanosensitive" genes, but it is a challenge to demonstrate that the genetic regulation of the biological system is dependant on particular mechanical forces in vivo. We propose a new means of selecting candidate mechanosensitive genes by comparing in vivo gene expression patterns with patterns of biophysical stimuli, computed using finite element analysis. In this study, finite element analyses of the avian embryonic limb were performed using anatomically realistic rudiment and muscle morphologies, and patterns of biophysical stimuli were compared with the expression patterns of four candidate mechanosensitive genes integral to bone development. The expression patterns of two genes, Collagen X (ColX) and Indian hedgehog (Ihh), were shown to colocalise with biophysical stimuli induced by embryonic muscle contractions, identifying them as potentially being involved in the mechanoregulation of bone formation. An altered mechanical environment was induced in the embryonic chick, where a neuromuscular blocking agent was administered in ovo to modify skeletal muscle contractions. Finite element analyses predicted dramatic changes in levels and patterns of biophysical stimuli, and a number of immobilised specimens exhibited differences in ColX and Ihh expression. The results obtained indicate that computationally derived patterns of biophysical stimuli can be used to inform a directed search for genes that may play a mechanoregulatory role in particular in vivo events or processes. Furthermore, the experimental data demonstrate that ColX and Ihh are involved in mechanoregulatory pathways and may be key mediators in translating information from the mechanical environment to the molecular regulation of bone formation in the embryo.

Project description:Multiple molecular and cellular mechanisms are associated with the initiation and progression of aortic valve disease. Alterations in ECM remodeling, increased expression of pro-inflammatory cytokines, calcification, lipid deposition and changes in valve cell phenotype have demonstrated roles in development of aortic valve disease. Mechanical stimulation has a significant role in determining the physiological properties of valve tissue and an altered hemodynamic environment may result in pathological changes. We used microarrays to detail the global of gene expression profiles underlying valve remodeling during valve exposure to of two levels of cyclic mechanical pressure (normotensive 0-80mmHg and hypertensive 0-120mmHg ) on porcine valve tissue transcriptome using Sus Scrofa cDNA microarrays from Affymetrix and we identified distinct classes of up-regulated genes during this process. Hybridizations were carried out with RNA isolated from six independetn samples of valve tissue exposed to normotensive and hypertensive pressure for 24 hours at 1hz frecuency. Differentially expressed genes were identified by The t test with the option of unequal variance was used to calculate P values for each gene. The fold change and Q values for each gene were calculated with SAM program with permutation of 500 . Biological modeling of the differentially expressed genes (DE) was carried out based on GO groups and network analysis in ingenuity Pathway Analysis (IPA). Experiment Overall Design: The experimental design included three biological samples of porcine valve leaflets exposed to cyclic pressures of 0-80 or 0-120 mmHg for 24 hours, representing normotensive and hypertensive diastolic transvalvular pressure, respectively. Using Affymetrix porcine microarrays, we compared global gene expression profiles of aortic valve leaflets exposed to elevated and normal physiological pressure conditions . The effects of cyclic pressure on the transcriptome was determined by comparing the quantity and magnitud of change in gene expression levels of valve leflets, as well evaluating the molecular function each gene has in the cell,in the presence of hypertennsive (experimental) and normotensve pressurec (control).

Dataset Information

Identification of mechanosensitive genes during skeletal development: alteration of genes associated with cytoskeletal rearrangement and cell signalling pathways.

Publications

Identification of mechanosensitive genes during skeletal development: alteration of genes associated with cytoskeletal rearrangement and cell signalling pathways.

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