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Stochastic protein expression in individual cells at the single molecule level
Long Cai1, Nir Friedman, X Sunney Xie
1Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
Nature
|March 17, 2006
Summary
This study introduces a microfluidic assay for real-time, single-molecule observation of gene expression in living cells. The assay reveals that protein production occurs in bursts, enabling characterization of low-copy number proteins.
Area of Science:
- Cellular and Molecular Biology
- Biophysics
- Systems Biology
Background:
- Gene expression in living cells is inherently stochastic due to low molecule counts.
- Observing individual protein production events is challenging in unsynchronized cell populations.
- Existing single-cell measurements lack the sensitivity for resolving discrete protein production events.
Purpose of the Study:
- To develop a sensitive assay for real-time, single-molecule observation of gene expression in individual cells.
- To investigate the dynamics of protein production, specifically focusing on burst-like events.
- To demonstrate the assay's applicability across different cell types for studying low-abundance proteins.
Main Methods:
- Development of a microfluidic-based assay enabling real-time monitoring.
- Single-molecule sensitivity for observing beta-galactosidase expression in Escherichia coli.
- Application of the assay to budding yeast and mouse embryonic stem cells.
Main Results:
- Demonstrated real-time, single-molecule observation of gene expression.
- Observed that protein production occurs in stochastic bursts.
- Characterized burst size and frequency, showing an exponential distribution for burst size.
- Showcased the assay's generality across prokaryotic and eukaryotic cells.
Conclusions:
- The microfluidic assay provides unprecedented real-time, single-molecule resolution of gene expression dynamics.
- Protein production is characterized by bursts, with quantifiable parameters like burst size and frequency.
- This technique is crucial for studying low-copy number proteins inaccessible to current genomic and proteomic methods.
- The assay's broad applicability facilitates system-wide characterization of gene expression in diverse biological systems.
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