Actin filaments (F-actin) plays a crucial role in composing the three-dimensional cytoskeleton in mammalian cells. The formation of F-actin is dynamic in a cell, and the arrangement needs to be reorganized during cell migration, proliferation, morphological change and differentiation in a stem cell. F-actin, physiologically link the plasma membrane and nuclear membrane, makes itself sensitive to deliver the mechanical forces from mechanoreceptor on the cell membrane into the nucleus directly. Actin dynamics, bundling, cross-linking, attachment to membranes and movement are regulated by actin-binding proteins so that the arrangement of F-actin can be controlled. However, the in v^-vo molecular mechanism responsible for the generation of force via F-actin arrangement is not fully understood. Mesenchymal stem cells (MSCs) are adult stem cells with self-renewal, multi-potency and immunomodulation ability. In a series of studies, we have demonstrated that F-actin serves as a reactor to response different patterns of physical stimuli delivered from different mechanoreceptors such as integrin, cadherin, and opsin. The de-polymerization and re-polymerization of F-actin in MSC triggered by shear force not only results in change of the F-actin orientation, but also alters the plasticity, and which is accompanied by dynamic changes from differential expressed genes (DEGs) and differential expressed proteins (DEPs) in MSCs. We also observe microRNA regulation and shunting of transcriptional factor into nucleus in MSCs participate in enhancement of stem cell property. It is known that differences of chromatin and genome characteristics exist between embryonic stem cells and differentiated somatic cells. LIM domain, binds to F-actin, presents in many proteins involving regulation of gene expression, cytoarchitecture, cell adhesion, cell motility and signal transduction. LIM proteins are thought to be mediators communicating between the cytosolic and the nuclear compartments. However, the mechanism of shear force systemically regulating DEGs/DEPs mediated by F-actin orientation in control of MSC plasticity needs to be further investigated. The aim of this study is to investigate the underlying mechanism of F-actin orientation governed dynamic biophysical response in MSCs via a system bioinformatics analysis. We hypothesis that F-actin orientation controlled by a shear force sensitive actin-binding protein. De-polymerization of F-actin regulates cytoplasmic to nuclear communication, and key LIM protein/TF(s) into nucleus turns on/off the genetic expressions in MSCs; at the same time, actin-dependent microRNA(s) regulates protein expression rapidly in MSCs. In the 1st year, time-dependent Hub map of DEGs and DEPs in MSCs responsible for shear stress through a systemic, functional analysis will be established. In the 2nd year, key regulator(s) of F-actin orientation and key LIM proteins/TF(s)/microRNA(s) accounting for the shear stress induced DEGs and DEPs in MSCs will be investigated. In the 3rd year, we will confirm the proposed hypothesis and the molecular mechanism in this study. The originality of the study is high as no similar studies have been reported in the literature. The significance of the research achievements of this study is that it will offer a novel, powerful platform technology to analyze the complexity of dynamic molecular mechanism in a biophysical response via a systemic fashion, rather than a target-oriented approach.
|Effective start/end date||8/1/15 → 7/31/16|
- Dynamic biophysical response
- F-actin orientation
- Mesenchymal stem cells (MSCs)
- Shear force
- System bioinformatics analysis