Document Detail

Cell population heterogeneity in expression of a gene-switching network with fluorescent markers of different half-lives.
MedLine Citation:
PMID:  17092594     Owner:  NLM     Status:  MEDLINE    
We studied the distribution of expression levels amongst the cells of an Escherichia coli population carrying a gene-switching network, known as the genetic toggle. We employed two green fluorescent protein (GFP) reporter proteins with different half-lives and characterized the effect of isopropyl-beta-D-thiogalactopyranoside (IPTG) inducer concentration on fluorescence distribution characteristics. Our flow cytometric measurements indicated that there is a spread of fluorescence phenotypes of one to three orders of magnitude, due to the highly heterogeneous nature of the cell populations under investigation. Moreover, the shape of the distribution at a specific quasi-time-invariant reference state, defined for comparison purposes, strongly depended on inducer concentration. For very low and very high inducer concentrations, the distributions at the reference state are unimodal. On the contrary, for intermediate IPTG concentrations, two distinct subpopulations were formed below and above a single-cell threshold, resulting in distributions with a bimodal shape. The region of inducer concentrations where bimodality is observed is the same and independent of GFP half-life. Bimodal number density functions are not only obtained at the reference state. Transient studies revealed that even in cases where the distribution at the reference state is unimodal, the distribution becomes bimodal for a period of time required for the population to pass through the single-cell induction threshold. However, this feature was only captured by the system with the reduced half-life GFP. A simple single-cell model was used to shed light into the effect of inducer concentration and GFP half-life on the shape of the experimentally measured number density functions. The wide range of fluorescent phenotypes and the inability of the average population properties to fully characterize network behavior, indicate the importance of taking into account cell population heterogeneity when designing such a gene-switching network for biotechnological and biomedical applications.
Stephanie Portle; Thomas B Causey; Kim Wolf; George N Bennett; Ka-Yiu San; Nikos Mantzaris
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2006-10-17
Journal Detail:
Title:  Journal of biotechnology     Volume:  128     ISSN:  0168-1656     ISO Abbreviation:  J. Biotechnol.     Publication Date:  2007 Feb 
Date Detail:
Created Date:  2007-01-16     Completed Date:  2007-04-02     Revised Date:  2007-12-03    
Medline Journal Info:
Nlm Unique ID:  8411927     Medline TA:  J Biotechnol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  362-75     Citation Subset:  IM    
Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX 77251-1892, USA.
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MeSH Terms
Flow Cytometry
Gene Expression Regulation, Bacterial*
Gene Targeting / methods*
Green Fluorescent Proteins / metabolism*
Isopropyl Thiogalactoside / metabolism*
Models, Biological
Recombinant Fusion Proteins / metabolism*
Grant Support
Reg. No./Substance:
0/Recombinant Fusion Proteins; 147336-22-9/Green Fluorescent Proteins; 367-93-1/Isopropyl Thiogalactoside

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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