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When Brachyury meets Smad1: the evolution of bilateral symmetry during gastrulation
Author(s) -
Marcellini Sylvain
Publication year - 2006
Publication title -
bioessays
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.175
H-Index - 184
eISSN - 1521-1878
pISSN - 0265-9247
DOI - 10.1002/bies.20387
Subject(s) - brachyury , gastrulation , bilateria , biology , evolutionary biology , effector , genetics , microbiology and biotechnology , phylogenetics , gene , mesoderm , embryogenesis , embryonic stem cell
Understanding the events that led to the emergence of the bilaterians is a daunting task, impaired by the huge evolutionary gap separating us from the pre‐Cambrian. During gastrulation, the expression of the transcription factor Brachyury is remarkably well conserved around the blastopore of bilaterians and cnidarians. Only the bilaterian Brachyury proteins, however, share a distinctive N‐terminal sequence not found in outgroups such as cnidarians, sponges or placozoans. We now know that, in vertebrates, this N‐terminal domain confers specific transcriptional activity, by recruiting Smad1, the first identified co‐factor for Brachyury. Smad1 is an effector of the BMP pathway, and has been isolated in bilaterians and cnidarians. Here, I propose that the protein–protein interaction between Brachyury and Smad1 represents an evolutionary novelty of the Urbilateria. The gain of the N‐terminal domain might have been selected to spatially modulate the activity of Brachyury, thereby facilitating the establishment of bilateral symmetry during gastrulation movements. BioEssays 28: 413–420, 2006. © 2006 Wiley Periodicals, Inc.