Regulation of a remote Shh forebrain enhancer by the Six3 homeoprotein

Nat Genet. 2008 Nov;40(11):1348-53. doi: 10.1038/ng.230. Epub 2008 Oct 5.

Abstract

In humans, SHH haploinsufficiency results in holoprosencephaly (HPE), a defect in anterior midline formation. Despite the importance of maintaining SHH transcript levels above a critical threshold, we know little about the upstream regulators of SHH expression in the forebrain. Here we describe a rare nucleotide variant located 460 kb upstream of SHH in an individual with HPE that resulted in the loss of Shh brain enhancer-2 (SBE2) activity in the hypothalamus of transgenic mouse embryos. Using a DNA affinity-capture assay, we screened the SBE2 sequence for DNA-binding proteins and identified members of the Six3 and Six6 homeodomain family as candidate regulators of Shh transcription. Six3 showed reduced binding affinity for the mutant compared to the wild-type SBE2 sequence. Moreover, Six3 with HPE-causing alterations failed to bind and activate SBE2. These data suggest a direct link between Six3 and Shh regulation during normal forebrain development and in the pathogenesis of HPE.

Publication types

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

MeSH terms

  • Animals
  • Base Sequence
  • COS Cells
  • Chlorocebus aethiops
  • Eye Proteins / metabolism*
  • Hedgehog Proteins / genetics
  • Hedgehog Proteins / metabolism*
  • Holoprosencephaly / genetics
  • Holoprosencephaly / pathology
  • Homeodomain Proteins / metabolism*
  • Humans
  • Hypothalamus / metabolism
  • Mice
  • Molecular Sequence Data
  • Mutation / genetics
  • Nerve Tissue Proteins / metabolism*
  • Protein Binding
  • Trans-Activators

Substances

  • Eye Proteins
  • Hedgehog Proteins
  • Homeodomain Proteins
  • Nerve Tissue Proteins
  • Sine oculis homeobox homolog 3 protein
  • Six6 protein, mouse
  • Trans-Activators