Preformed Chromatin Topology Assists Transcriptional Robustness of Shh During Limb Development

Proc Natl Acad Sci U S A. 2019 Jun 18;116(25):12390-12399. doi: 10.1073/pnas.1900672116. Epub 2019 May 30.

Abstract

Long-range gene regulation involves physical proximity between enhancers and promoters to generate precise patterns of gene expression in space and time. However, in some cases, proximity coincides with gene activation, whereas, in others, preformed topologies already exist before activation. In this study, we investigate the preformed configuration underlying the regulation of the Shh gene by its unique limb enhancer, the ZRS, in vivo during mouse development. Abrogating the constitutive transcription covering the ZRS region led to a shift within the Shh-ZRS contacts and a moderate reduction in Shh transcription. Deletion of the CTCF binding sites around the ZRS resulted in the loss of the Shh-ZRS preformed interaction and a 50% decrease in Shh expression but no phenotype, suggesting an additional, CTCF-independent mechanism of promoter-enhancer communication. This residual activity, however, was diminished by combining the loss of CTCF binding with a hypomorphic ZRS allele, resulting in severe Shh loss of function and digit agenesis. Our results indicate that the preformed chromatin structure of the Shh locus is sustained by multiple components and acts to reinforce enhancer-promoter communication for robust transcription.

Keywords: 3D genome; development; gene regulation; genetics; limb.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • CCCTC-Binding Factor / metabolism
  • Cell Cycle Proteins / metabolism
  • Chromatin / metabolism*
  • Chromosomal Proteins, Non-Histone / metabolism
  • Down-Regulation
  • Enhancer Elements, Genetic
  • Extremities / embryology*
  • Hedgehog Proteins / genetics*
  • Membrane Proteins / genetics
  • Mice
  • Promoter Regions, Genetic
  • Transcription, Genetic*

Substances

  • CCCTC-Binding Factor
  • Cell Cycle Proteins
  • Chromatin
  • Chromosomal Proteins, Non-Histone
  • Ctcf protein, mouse
  • Hedgehog Proteins
  • Lmbr1 protein, mouse
  • Membrane Proteins
  • Shh protein, mouse
  • cohesins