Cooperative Action of Multiple cis-Acting Elements Is Required for N-myc Expression in Branchial Arches: Specific Contribution of GATA3

Abstract

The precise expression of the N-myc proto-oncogene is essential for normal mammalian development, whereas altered N-myc gene regulation is known to be a determinant factor in tumor formation. Using transgenic mouse embryos, we show that N-myc sequences from kb −8.7 to kb +7.2 are sufficient to reproduce the N-myc embryonic expression profile in developing branchial arches and limb buds. These sequences encompass several regulatory elements dispersed throughout the N-myc locus, including an upstream limb bud enhancer, a downstream somite enhancer, a branchial arch enhancer in the second intron, and a negative regulatory element in the first intron. N-myc expression in the limb buds is under the dominant control of the limb bud enhancer. The expression in the branchial arches necessitates the interplay of three regulatory domains. The branchial arch enhancer cooperates with the somite enhancer region to prevent an inhibitory activity contained in the first intron. The characterization of the branchial arch enhancer has revealed a specific role of the transcription factor GATA3 in the regulation of N-myc expression. Together, these data demonstrate that correct N-myc developmental expression is achieved via cooperation of multiple positive and negative regulatory elements.

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Cooperative Action of Multiple cis-Acting Elements Is Required for N-myc Expression in Branchial Arches: Specific Contribution of GATA3

We thank Lucie Jeannotte, Josée Aubin, and Robert S. Viger for critical comments on the manuscript, Benoit Lachapelle, Julie Pageau, and Valérie Garceau for technical support, Hiroaki Taniguchi, Robert S. Viger, Nikita Avvakumov, and Jacques Coté for technical advice on ChIP assays, and Michael Parmacek for the GATA5 expression vector and James D. Engel for the Gata3 mutant mouse line.

J.-F.C.-G. held a studentship from the Fonds pour la Formation de Chercheurs et l'Aide à la Recherche. This work was supported by funding from NSERC and the Cancer Research Society Inc. to J.C.