Transcriptional Coupling of Distant Regulatory Genes in Living Embryos

The prevailing view of metazoan gene regulation is that individual genes are independently regulated by their own dedicated sets of transcriptional enhancers. Past studies reported long-range gene-gene associations, but their functional significance in regulating transcription remains uncertain and controversial. Here we employ quantitative single cell live imaging methods to provide the first demonstration of co-dependent transcriptional dynamics of genes separated by large genomic distances in living embryos. We find extensive physical and functional associations of distant paralogous genes, including co-regulation by shared enhancers and co-transcriptional bursting over distances of nearly 250kb. Regulatory inter-connectivity depends on promoter-proximal tethering elements and perturbations in these elements uncouple transcription and alter the bursting dynamics of distant genes, suggesting a role of genome topology in the formation and stability of co-transcriptional hubs. Transcriptional coupling of distant genes throughout the Drosophila genome underlies a broad spectrum of conserved developmental processes, suggesting a general strategy for long-range integration of gene activities. Overall design: MicroC experiments were conducted in biological duplicates. The control line was yw. Experimental lines were CRISPR-mediated deletions of specific architectural elements. All experiments were conducted with embryos at the nc14 stage.