Measuring Gene Expression, One Molecule at a Time

Although there is a trend in the life sciences towards big Biology, recently all the greatest insights have come from studies of single molecules. Some of the best work has come from Stephen Kowalczykowski's group. They have used single particle imaging to monitor how a single RecBCD complex unfold DNA.

Now in the latest issue of Nature, the Xie group, monitor the expression product of single genes in E. Coli. They perform this Herculean task by affixing the cells to small wells. When the gene (beta-galactosidase) is turned on, mRNA is produced and then translated into a secreted enzyme. In the microwell, enzymatic product accumulates and can be monitored by microscopy. In this study, the Xie group detect bursts of enzymes secreted by a single cell. They hypothesize that these bursts represent batches of enzymes that are produced from single mRNA. They then apply this technique to measure the production of enzymes in yeast and mammalian tissue culture cells.

Ref: Long Cai, Nir Friedman, and X. Sunney Xie. Stochastic protein expression in individual cells at the single molecule level. Nature (2006) 440:358-362