A. Gallet et al., TRUNK-SPECIFIC MODULATION OF WINGLESS SIGNALING IN DROSOPHILA BY TEASHIRT BINDING TO ARMADILLO, Current biology, 8(16), 1998, pp. 893-902
Background: One function of the Wingless signal cascade is to determin
e the 'naked' cuticle cell-fate choice instead of the denticled one in
Drosophila larvae. Wingless stabilises cytoplasmic Armadillo, which m
ay act in a transcriptional activator complex with the DNA-binding pro
tein T-cell factor (also known as Pangolin). As these components are c
ritical for all Wingless-dependent patterning events, the problem aris
es as to how specific outputs are achieved. Results: The Teashirt zinc
finger protein was found to be necessary for a subset of late Wingles
s-dependent functions in the embryonic trunk segments where the teashi
rt gene is expressed. Teashirt was found to be required for the mainte
nance of the late Wingless signalling target gene wingless but not for
an earlier one, engrailed. Armadillo and Teashirt proteins showed sim
ilar Wingless-dependent modulation patterns in homologous parts of eac
h trunk segment in embryos, with high levels of nuclear Teashirt and i
ntracellular Armadillo within cells destined to form naked cuticle. We
found that Teashirt associates with, and requires, Armadillo in a com
plex for its function. Conclusions: Teashirt binds to, and requires, A
rmadillo for the naked cell-fate choice in the larval trunk. Teashirt
is required for trunk segment identity, suggesting that Teashirt provi
des a region-specific output to Armadillo activity. Further modulation
of Wingless is achieved in homologous parts of each trunk segment whe
re Wingless and Teashirt are especially active. Our results provide a
novel, cell-intrinsic mechanism to explain the modulation of the activ
ity of the Wingless signalling pathway. (C) Current Biology Publicatio
ns ISSN 0960-9822.