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Role of Feedback and Dynamics of a Gene Regulatory Network


Venturelli, Ophelia Shalini (2013) Role of Feedback and Dynamics of a Gene Regulatory Network. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/WGK3-Y839.


Cells exhibit a diverse repertoire of dynamic behaviors. These dynamic functions are implemented by circuits of interacting biomolecules. Although these regulatory networks function deterministically by executing specific programs in response to extracellular signals, molecular interactions are inherently governed by stochastic fluctuations. This molecular noise can manifest as cell-to-cell phenotypic heterogeneity in a well-mixed environment. Single-cell variability may seem like a design flaw but the coexistence of diverse phenotypes in an isogenic population of cells can also serve a biological function by increasing the probability of survival of individual cells upon an abrupt change in environmental conditions. Decades of extensive molecular and biochemical characterization have revealed the connectivity and mechanisms that constitute regulatory networks. We are now confronted with the challenge of integrating this information to link the structure of these circuits to systems-level properties such as cellular decision making. To investigate cellular decision-making, we used the well studied galactose gene-regulatory network in Saccharomyces cerevisiae. We analyzed the mechanism and dynamics of the coexistence of two stable on and off states for pathway activity. We demonstrate that this bimodality in the pathway activity originates from two positive feedback loops that trigger bistability in the network. By measuring the dynamics of single-cells in a mixed sugar environment, we observe that the bimodality in gene expression is a transient phenomenon. Our experiments indicate that early pathway activation in a cohort of cells prior to galactose metabolism can accelerate galactose consumption and provide a transient increase in growth rate. Together these results provide important insights into strategies implemented by cells that may have been evolutionary advantageous in competitive environments.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:bistability, gene regulatory network, circuit, dynamics
Degree Grantor:California Institute of Technology
Major Option:Biochemistry and Molecular Biophysics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Murray, Richard M.
Thesis Committee:
  • Phillips, Robert B. (chair)
  • Elowitz, Michael B.
  • Deshaies, Raymond Joseph
  • El-Samad, Hana
  • Murray, Richard M.
Defense Date:30 May 2013
Record Number:CaltechTHESIS:06072013-095239958
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7863
Deposited By: Ophelia Venturelli
Deposited On:07 Jun 2013 23:49
Last Modified:04 Oct 2019 00:02

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