A focus of our research efforts is to discern the influence of mechanical and osmotic stress that build up in tumor microenvironments being causal in metastatic phenotype formation.  Osmotic stress is due to differences in the activity of water between the cell interior and the microenvironment.  We have investigated how the difference in water activity causes stochasticity in a synthetic gene network in E.coli as a model. A synthetic gene network consisting of three genes in a cascade that are sequentially downregulated and reported by CFP and YFP, and fourth independent gene reported by RFP was subjected to osmotic stress with varying concentrations of NaCl and sucrose (0 � 3 M). The fluorescence intensities and self-correlation parameters for CFP, YFP, and RFP expression, and intrinsic, and extrinsic noise parameters and transfer functions for cfp-yfp, cfp-rfp, and yfp-rfp gene pairs determined from the respective protein expression exhibit a combined repression and activation depending on activity of water.  Stochasticity in gene expression is very sensitive to changes in water activity and almost entirely due to intrinsic noise which decreases in the order cfp-yfp>yfp-rfp>cfp-rfp.  The transfer functions provide information on the directionality of noise propagation in the gene network.  Differences between NaCl and sucrose as solutes were observed and could indicate the participation of mechanosensitive ion channels on the membrane wall.  Significant aspects of these studies will be discussed.

Osmotic stress induced stochasticity in <i>E.coli</i> synthetic gene network

247th National Meeting (2014)

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Osmotic stress induced stochasticity in E.coli synthetic gene network