Linking pattern formation to cell-type specification: Dichaete and Ind directly repress achaete gene expression in the Drosophila CNS

*Program in Molecular Cell Biology and
^‡Department of Genetics, Washington University School of Medicine, 4566 Scott Avenue, St. Louis, MO 63110; and
^†Department of Anatomy, University of Wisconsin Medical School, 1300 University Avenue, Madison, WI 53706

Communicated by Marshall Nirenberg, National Institutes of Health, Bethesda, MD, January 4, 2007 (received for review October 1, 2006)

Abstract

Mechanisms regulating CNS pattern formation and neural precursor formation are remarkably conserved between Drosophila and vertebrates. However, to date, few direct connections have been made between genes that pattern the early CNS and those that trigger neural precursor formation. Here, we use Drosophila to link directly the function of two evolutionarily conserved regulators of CNS pattern along the dorsoventral axis, the homeodomain protein Ind and the Sox-domain protein Dichaete, to the spatial regulation of the proneural gene achaete (ac) in the embryonic CNS. We identify a minimal achaete regulatory region that recapitulates half of the wild-type ac expression pattern in the CNS and find multiple putative Dichaete-, Ind-, and Vnd-binding sites within this region. Consensus Dichaete sites are often found adjacent to those for Vnd and Ind, suggesting that Dichaete associates with Ind or Vnd on target promoters. Consistent with this finding, we observe that Dichaete can physically interact with Ind and Vnd. Finally, we demonstrate the in vivo requirement of adjacent Dichaete and Ind sites in the repression of ac gene expression in the CNS. Our data identify a direct link between the molecules that pattern the CNS and those that specify distinct cell-types.

Footnotes

^§To whom correspondence should be addressed. E-mail: jskeath{at}genetics.wustl.edu
Author contributions: G.Z. and J.B.S. designed research; G.Z., G.B.-F., B.A.W., and J.B.S. performed research; G.B.-F. contributed new reagents/analytic tools; G.Z. and J.B.S. analyzed data; and G.Z. and J.B.S. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/cgi/content/full/0611700104/DC1.
Abbreviations:

ac,

achaete;

sc,

scute.