Wilhelm Huck and colleagues, and in collaboration with colleagues from the Eindhoven University of Technology, have published their research in Nature Nanotechnology in an article entitled: Macromolecular crowding creates heterogeneous environments of gene expression in picolitre droplets.
Understanding the dynamics of complex enzymatic reactions in highly crowded small volumes is crucial for the development of synthetic minimal cells. Compartmentalised biochemical reactions in cell-sized containers exhibit a degree of randomness due to the small number of molecules involved. However, it is unknown how the physical environment contributes to the stochastic nature of multistep enzymatic processes. Here, we present a robust method to quantify gene expression noise in vitro using droplet microfluidics. We study the changes in stochasticity in cell-free gene expression of two genes compartmentalised within droplets as a function of DNA copy number and macromolecular crowding. We find that decreased diffusion caused by a crowded environment leads to the spontaneous formation of heterogeneous micro-environments of mRNA as local production rates exceed diffusion rates of macromolecules. This heterogeneity leads to a higher probability of the molecular machinery to stay in the same microenvironment, directly increasing the system’s stochasticity.
Maike M. K. Hansen, Lenny H. H. Meijer, Evan Spruijt, Roel J. M. Maas, Marta Ventosa Rosquelles, Joost Groen, Hans A. Heus & Wilhelm T. S. Huck. Macromolecular crowding creates heterogeneous environments of gene expression in picolitre droplets, Nature Nanotechnology (2015), doi:10.1038/nnano.2015.243