Wingless directly represses DPP morphogen expression via an armadillo/TCF/Brinker complex.
BACKGROUND
Spatially restricted morphogen expression drives many patterning and regeneration processes, but how is the pattern of morphogen expression established and maintained? Patterning of Drosophila leg imaginal discs requires expression of the DPP morphogen dorsally and the wingless (WG) morphogen ventrally. We have shown that these mutually exclusive patterns of expression are controlled by a self-organizing system of feedback loops that involve WG and DPP, but whether the feedback is direct or indirect is not known.


RESULTS
By analyzing expression patterns of regulatory DNA driving reporter genes in different genetic backgrounds, we identify a key component of this system by showing that WG directly represses transcription of the dpp gene in the ventral leg disc. Repression of dpp requires a tri-partite complex of the WG mediators armadillo (ARM) and dTCF, and the co-repressor Brinker, (BRK), wherein ARM.dTCF and BRK bind to independent sites within the dpp locus.


CONCLUSIONS
Many examples of dTCF repression in the absence of WNT signaling have been described, but few examples of signal-driven repression requiring both ARM and dTCF binding have been reported. Thus, our findings represent a new mode of WG mediated repression and demonstrate that direct regulation between morphogen signaling pathways can contribute to a robust self-organizing system capable of dynamically maintaining territories of morphogen expression.
Theisen
Heidi
H
Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America.
Syed
Adeela
A
Nguyen
Baochi T
BT
Lukacsovich
Tamas
T
Purcell
Judith
J
Srivastava
Gyan Prakash
GP
Iron
David
D
Gaudenz
Karin
K
Nie
Qing
Q
Wan
Frederic Y M
FY
Waterman
Marian L
ML
Marsh
J Lawrence
JL
D000818:Animals; D051186:Armadillo Domain Proteins / Q000235:genetics / Q000378:metabolism*; D019521:Body Patterning / Q000502:physiology; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000196:embryology / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051155:Wnt1 Protein / Q000235:genetics / Q000378:metabolism*
C495305:ARM protein, Drosophila; D051186:Armadillo Domain Proteins; D029721:Drosophila Proteins; D046912:Multiprotein Complexes; D012097:Repressor Proteins; D014157:Transcription Factors; D051155:Wnt1 Protein; C118082:brk protein, Drosophila; C064196:dpp protein, Drosophila; C115159:pan protein, Drosophila; C074622:wg protein, Drosophila