Soft Matter Seminar: Sorting out tenascin

Thursday, July 29, 2010 - 1:00pm - 2:00pm
Reiss 261A
Dan Sisan

The extracellular matrix protein tenascin-C plays a critical role in development, wound healing, and cancer progression, but how it is controlled and exerts its physiological role remains unclear. To study the dynamic regulation of tenascin-C, we use a cell line that is stably transfected with the tenascin-C promoter ligated to green fluorescent protein (GFP). Flow cytometry and automated live cell microscopy and image analysis show that the promoter activity within the population of clonal cells has a distribution spanning several orders of magnitude, with a large ratio of standard deviation to mean, and a long exponential tail. In contrast, many other promoters show bimodal distributions. The activity levels within the population change dynamically on time scales from days to weeks, as revealed by experiments using fluorescence activated cell sorting (FACS). With FACS, we sorted two subpopulations based on promoter activity and found that the bright (transcriptionally active) subpopulation relaxed back to the steady state distribution faster than the dim (transcriptionally inactive) subpopulation. Simulations were developed that rule out plausible models, but only hint at possible mechanisms. Furthermore, the sorted subpopulations show differences in motility, size, and proliferation that are not seen in live cell experiments in an unsorted populations, suggesting nonlinear effects of the extracellular environment.

Host: Daniel Blair