Visualization of trans-homolog enhancer-promoter interactions at the Abd-B Hox locus in the Drosophila embryo

Dev Cell. 2004 Dec;7(6):925-32. doi: 10.1016/j.devcel.2004.11.001.


The Hox gene Abdominal-B (Abd-B) controls the morphogenesis of posterior abdominal segments in Drosophila. Expression is regulated by a series of 3' enhancers that are themselves transcribed. RNA FISH was used to visualize nascent transcripts associated with coding and noncoding regions of Abd-B in developing embryos. Confocal imaging suggests that distal enhancers often loop to the Abd-B promoter region. Surprisingly, enhancers located on one chromosome frequently associate with the Abd-B transcription unit located on the other homolog. These trans-homolog interactions can be interpreted as the direct visualization of a genetic phenomenon known as transvection, whereby certain mutations in Abd-B can be rescued in trans by the other copy of the gene. A 10 kb sequence in the 3' flanking region mediates tight pairing of Abd-B alleles, thereby facilitating trans looping of distal enhancers. Such trans-homolog interactions might be a common mechanism of gene regulation in higher metazoans.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alleles
  • Animals
  • DNA / metabolism
  • Drosophila Proteins / genetics*
  • Drosophila melanogaster / metabolism
  • Enhancer Elements, Genetic*
  • Homeodomain Proteins / genetics*
  • Homozygote
  • Image Processing, Computer-Assisted
  • In Situ Hybridization, Fluorescence
  • Microscopy, Confocal
  • Models, Biological
  • Models, Genetic
  • Mutation
  • Promoter Regions, Genetic*
  • Protein Binding
  • RNA / chemistry
  • RNA, Messenger / metabolism
  • Transcription, Genetic


  • Abd-B proteins, Drosophila
  • Drosophila Proteins
  • Homeodomain Proteins
  • RNA, Messenger
  • RNA
  • DNA