Xiro‐1 controls mesoderm patterning by repressing bmp‐4 expression in the spemann organizer

The Iroquois genes code for homeodomain proteins that have been implicated in the neural development of Drosophila and vertebrates. We show here for the first time that Xiro‐1, one of the Xenopus Iroquois genes, is expressed in the Spemann organizer from the start of gastrulation and that its overex...

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Bibliographic Details
Published in:Developmental dynamics 2001-11, Vol.222 (3), p.368-376
Main Authors: Glavic, Alvaro, Gómez‐Skarmeta, Jose Luis, Mayor, Roberto
Format: Article
Language:English
Subjects:
Animals
BMP‐4
Bone Morphogenetic Protein 4
Bone Morphogenetic Proteins - antagonists & inhibitors
Bone Morphogenetic Proteins - metabolism
Embryo, Nonmammalian - physiology
mesoderm
Mesoderm - physiology
Nerve Tissue Proteins
Organizers, Embryonic - metabolism
Repressor Proteins - physiology
Spemann organizer
Transcription Factors - physiology
Xenopus - embryology
Xenopus Proteins
Xiro‐1
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Summary:The Iroquois genes code for homeodomain proteins that have been implicated in the neural development of Drosophila and vertebrates. We show here for the first time that Xiro‐1, one of the Xenopus Iroquois genes, is expressed in the Spemann organizer from the start of gastrulation and that its overexpression induces a secondary axis as well as the ectopic expression of several organizer genes, such as chordin, goosecoid, and Xlim‐1. Our results also indicate that Xiro‐1 normally functions as a transcriptional repressor in the mesoderm. Overexpression of Xiro‐1 or a chimeric form fused to the repressor domain of Engrailed cause similar phenotypes while overexpression of functional derivatives of Xiro‐1 fused with transactivation domains (VP16 or E1A) produce the opposite effects. Finally, we show that Xiro‐1 works as a repressor of bmp‐4 transcription and that its effect on organizer development is dependent on BMP‐4 activity. We propose that the previously observed down regulation of bmp‐4 in the dorsal mesoderm during gastrulation can be explained by the repressor activity of Xiro‐1 described here. Thus, Xiro‐1 seems to have at least two different functions: control of neural plate and organizer development, both of which could be mediated by repression of bmp‐4 transcription. © 2001 Wiley‐Liss, Inc.
ISSN:1058-8388
1097-0177
DOI:10.1002/dvdy.1189