Leyes Porello, E. A. | Search bioRxiv

bioRxiv2025

Enhancer Placement Impacts Transcriptional Dynamics in Drosophila Embryos

The functional role of enhancer-promoter configurations in transcription regulation remains poorly understood, despite the wide range of linear genomic distance and relative enhancer positioning observed in endogenous contexts. While canonical models suggest that enhancers operate independently of genomic position, technical limitations have obscured insights on transcriptional kinetics. Here, we employ single-cell MS2/MCP-based live imaging in Drosophila embryos to systematically analyze transcriptional dynamics driven by sub-10kb enhancer-promoter arrangements. Kinetic analyses reveal that while linear enhancer-promoter distance moderately tunes transcriptional output, downstream enhancer positioning reduces mRNA output by 70%. Each configuration modulates distinct transcriptional parameters: linear distance governs initiation kinetics, while relative enhancer positioning dictates transcriptional stability. These effects are consistent across varied enhancer and reporter sequences, revealing configuration-dependent cis-regulatory element arrangement as an intrinsic mechanism for transcriptional fine-tuning. This work challenges the paradigm of configuration-independent enhancer function and establishes a framework to dissect the interplay between genome architecture and trans-acting factors.

molecular biology↗

bioRxiv2024

SCO-pH: Microfluidic dynamic phenotyping platform for high-throughput screening of single cell acidification

Studies on the dynamics of single cell phenotyping have been hampered by the lack of quantitative high-throughput metabolism assays. Extracellular acidification, a prominent phenotype, yields significant insights into cellular metabolism, including tumorigenicity. Here, we develop a versatile microfluidic system for single cell optical pH analysis (SCO-pH), which compartmentalizes single cells in 140-pL droplets and immobilizes approximately 40,000 droplets in a two-dimensional array for temporal extracellular pH analysis. SCO-pH distinguishes cells undergoing hyperglycolysis induced by oligomycin A from untreated cells by monitoring their extracellular acidification. To facilitate pH sensing in each droplet, we encapsulate a cell-impermeable pH probe whose fluorescence intensities are quantified. Using this approach, we can differentiate hyperglycolytic cells and concurrently observe single cell heterogeneity in extracellular acidification dynamics. This high-throughput system will be useful in applications that require dynamic phenotyping of single cells with significant heterogeneity.

bioengineering↗