The volumes and transcript counts of single cells reveal concentration homeostasis and capture biological noise.
Bottom Line: We compared three cell clones that differ only in the genomic integration site of an identical constitutively expressed reporter gene.We found that the cell-to-cell variability in the mRNA concentration is almost exclusively due to cell-to-cell variation in gene expression activity, whereas the cell-to-cell variation in mRNA number is larger, due to a significant contribution of cell volume variability.We concluded that the precise relationship between transcript number and cell volume sets the biological stochasticity of living cells.
Affiliation: Synthetic Systems Biology and Nuclear Organization Group, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH Amsterdam, The Netherlands.Show MeSH
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Mentions: Early studies on stochastic gene expression relied on fluorescent proteins to assess protein noise by either taking snapshots (Elowitz et al., 2002; Ozbudak et al., 2002) or by using real-time fluorescence imaging (Rosenfeld et al., 2005; Sigal et al., 2006). More recently, single-molecule mRNA counting has been introduced as a method for absolute quantification of mRNA number (Golding et al., 2005; Raj et al., 2006, 2008). The advantage of single-transcript counting with single-molecule RNA fluorescence in situ hybridization (smFISH) is that it does not require genetic engineering (Raj et al., 2006, 2008; Zenklusen et al., 2008; Youk et al., 2010). Specific DNA probes tagged with fluorescent dyes are used to visualize individual mRNA molecules within fixed cells (Figure 1A).
Affiliation: Synthetic Systems Biology and Nuclear Organization Group, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH Amsterdam, The Netherlands.