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Molecular and Cellular Biology, June 2004, p. 5028-5038, Vol. 24, No. 11
0270-7306/04/$08.00+0 DOI: 10.1128/MCB.24.11.5028-5038.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Nicolas Pilon,1,
Martin Houle,1,2 Karen Oh,1 Jean-René Sylvestre,1 Panagiotis Prinos,1,
and David Lohnes1,2,3*
Institut de Recherches Cliniques de Montréal,1 Department of Molecular Biology, Université de Montréal,2 Department of Experimental Medicine, McGill University, Montréal, Québec, Canada3
Received 27 August 2003/ Returned for modification 9 December 2003/ Accepted 12 March 2004
The Cdx1 gene product is essential for normal anterior-posterior vertebral patterning. Expression of Cdx1 is regulated by several pathways implicated in anterior-posterior patterning events, including retinoid and Wnt signaling. We have previously shown that retinoic acid plays a key role in early stages of Cdx1 expression at embryonic day 7.5 (E7.5), while both Wnt3a signaling and an autoregulatory loop, dependent on Cdx1 itself, are involved in later stages of expression (E8.5 to E9.5). This autoregulation is reflected by the ability of Cdx1 to affect expression from proximal Cdx1 promoter sequences in tissue culture. However, this region is devoid of a demonstrable Cdx response element(s). We have now found that Cdx1 and LEF1, a nuclear effector of Wnt signaling, synergize to induce expression from the Cdx1 promoter through previously documented LEF/T-cell factor response elements. We also found a direct physical interaction between the homeodomain of Cdx1 and the B box of LEF1, suggesting a basis for this synergy. Consistent with these observations, analysis of Cdx1 Wnt3avt compound mutants demonstrated that Wnt and Cdx1 converged on Cdx1 expression and vertebral patterning in vivo. Further data suggest that Cdx-high-mobility group box interactions might be involved in a number of additional pathways.
M.B. and N.P. contributed equally to this work.
Present address: Aurelium Biopharma Inc., Laval H7V 4A9, Canada.
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