Combgap Promotes Ovarian Niche Development and Chromatin Association of EcR-Binding Regions in BR-C

PLoS Genet. 2016 Nov 15;12(11):e1006330. doi: 10.1371/journal.pgen.1006330. eCollection 2016 Nov.

Abstract

The development of niches for tissue-specific stem cells is an important aspect of stem cell biology. Determination of niche size and niche numbers during organogenesis involves precise control of gene expression. How this is achieved in the context of a complex chromatin landscape is largely unknown. Here we show that the nuclear protein Combgap (Cg) supports correct ovarian niche formation in Drosophila by controlling ecdysone-Receptor (EcR)- mediated transcription and long-range chromatin contacts in the broad locus (BR-C). Both cg and BR-C promote ovarian growth and the development of niches for germ line stem cells. BR-C levels were lower when Combgap was either reduced or over-expressed, indicating an intricate regulation of the BR-C locus by Combgap. Polytene chromosome stains showed that Cg co-localizes with EcR, the major regulator of BR-C, at the BR-C locus and that EcR binding to chromatin was sensitive to changes in Cg levels. Proximity ligation assay indicated that the two proteins could reside in the same complex. Finally, chromatin conformation analysis revealed that EcR-bound regions within BR-C, which span ~30 KBs, contacted each other. Significantly, these contacts were stabilized in an ecdysone- and Combgap-dependent manner. Together, these results highlight Combgap as a novel regulator of chromatin structure that promotes transcription of ecdysone target genes and ovarian niche formation.

MeSH terms

  • Animals
  • Chromatin / genetics*
  • Drosophila Proteins / genetics*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / growth & development
  • Ecdysone / biosynthesis
  • Ecdysone / genetics
  • Female
  • Gene Expression Regulation, Developmental
  • Organ Specificity
  • Ovary / growth & development
  • Ovary / metabolism
  • Polytene Chromosomes / genetics
  • Receptors, Steroid / genetics*
  • Stem Cell Niche / genetics
  • Transcription Factors / genetics*
  • Transcription, Genetic*

Substances

  • Br protein, Drosophila
  • Chromatin
  • Drosophila Proteins
  • Receptors, Steroid
  • Transcription Factors
  • cg protein, Drosophila
  • ecdysone receptor
  • Ecdysone

Grants and funding

This study was funded by the Israel Science Foundation. Grant number 1316/12 to LG. http://www.isf.org.il/ The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.