Role of the mechanical microenvironment in modulating transcriptional bursting dynamics

In many genes, transcription occurs in stochastic “bursts” of mRNA synthesis followed by periods of inactivity. By tuning burst dynamics, cells can control mRNA levels, thereby regulating gene expression. Such stochastic behavior has been observed in cell responses to external chemical cues. Matrix stiffness is known to influence gene expression and can enhance progression of diseases involving altered tissue mechanics, but individual gene responses to mechanical cues are less well-studied.

To explore transcriptional responses to mechanical input, we examined the relationship between substrate stiffness and bursting dynamics in MCF7 breast cancer cells. We focused on Trefoil Factor 1 (TFF1), an estrogen-responsive gene upregulated in breast cancer. Cells with fluorescent reporters for TFF1 mRNA were grown on hydrogels mimicking healthy (1 kPa) or cancerous tissue (12-100 kPa) and imaged to visualize transcriptional bursts. Measurements of interest were extracted using automated nucleus segmentation and burst detection. Results suggest TFF1 bursting is enhanced on soft substrates, consistent with bulk RNA-seq data. To elucidate mechanisms of regulation, we monitored bursting dynamics in live cells and measured average burst frequency, amplitude, and duration. Ongoing and future work will investigate the mechanisms underlying mechanosensing and use information theoretic approaches to characterize how cells encode mechanical information.