The Wg and Dpp morphogens regulate gene expression by modulating the frequency of transcriptional bursts.

Rachael Bakker,Madhav Mani,Richard W Carthew

doi:10.7554/elife.56076

Abstract

Morphogen signaling contributes to the patterned spatiotemporal expression of genes during development. One mode of regulation of signaling-responsive genes is at the level of transcription. Single-cell quantitative studies of transcription have revealed that transcription occurs intermittently, in bursts. Although the effects of many gene regulatory mechanisms on transcriptional bursting have been studied, it remains unclear how morphogen gradients affect this dynamic property of downstream genes. Here we have adapted single molecule fluorescence in situ hybridization (smFISH) for use in the Drosophila wing imaginal disc in order to measure nascent and mature mRNA of genes downstream of the Wg and Dpp morphogen gradients. We compared our experimental results with predictions from stochastic models of transcription, which indicated that the transcription levels of these genes appear to share a common method of control via burst frequency modulation. Our data help further elucidate the link between developmental gene regulatory mechanisms and transcriptional bursting.

Highlights

Paracrine signaling is a highly conserved means for cells within a tissue to communicate with one another to regulate diverse activities including proliferation, differentiation, apoptosis, and movement
MRNA synthesis occurs in bursts that are interrupted by periods of dormant output
We have explored how the Wg and Dpp morphogens regulate transcription dynamics in the wing disc

Summary

INTRODUCTION

Paracrine signaling is a highly conserved means for cells within a tissue to communicate with one another to regulate diverse activities including proliferation, differentiation, apoptosis, and movement. Many of these activities are mediated by changes in gene transcription that are brought about by reception of the signals. Enhancer strength and enhancerpromoter contact correlate with burst frequency of genes (Bartman, Hsu, Hsiung, Raj, & Blobel, 2016; Bothma et al, 2014; Chen et al, 2019; Fukaya, Lim, & Levine, 2016; Larsson et al, 2019) These studies altogether suggest that bursting frequency is potentiated by enhancer-promoter contact and is mediated by transcription factors binding to DNA. All of the genes are regulated by modulation of transcription burst frequency by Dpp and Wg even though their expression patterns are highly different from one another

RESULTS

DISCUSSION

MATERIALS AND METHODS