Msx1 is required for dorsal diencephalon patterning.
The dorsal midline of the neural tube has recently emerged as a major signaling center for dorsoventral patterning. Msx genes are expressed at the dorsal midline, although their function at this site remains unknown. Using Msx1(nlacZ) mutant mice, we show that the normal expression domain of Msx1 is interrupted in the pretectum of mutant embryos. Morphological and gene expression data further indicate that a functional midline is not maintained along the whole prosomere 1 in Msx1 mutant mice. This results in the downregulation of genes expressed laterally to the midline in prosomere 1, confirming the importance of the midline as a signaling center. Wnt1 is essential for dorsoventral patterning of the neural tube. In the Msx1 mutant, Wnt1 is downregulated before the midline disappears, suggesting that its expression depends on Msx1. Furthermore, electroporation in the chick embryo demonstrates that Msx1 can induce Wnt1 expression in the diencephalon neuroepithelium and in the lateral ectoderm. In double Msx1/Msx2 mutants, Wnt1 expression is completely abolished at the dorsal midline of the diencephalon and rostral mesencephalon. This indicates that Msx genes may regulate Wnt1 expression at the dorsal midline of the neural tube. Based on these results, we propose a model in which Msx genes are intermediary between Bmp and Wnt at this site.
Bach
Antoine
A
Unité de Génétique Moléculaire de la Morphogenèse, Institut Pasteur, URA 2578 du CNRS, 25 rue du Dr Roux, 75724 Paris Cedex 15, France.
Lallemand
Yvan
Y
Nicola
Marie-Anne
MA
Ramos
Casto
C
Mathis
Luc
L
Maufras
Mathilde
M
Robert
Benoît
B
D000818:Animals; D015415:Biomarkers; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004027:Diencephalon / Q000196:embryology*; D004475:Ectoderm / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D051957:MSX1 Transcription Factor; D051379:Mice; D009154:Mutation; D011518:Proto-Oncogene Proteins; D013351:Subcommissural Organ / Q000196:embryology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029961:Zebrafish Proteins
D015415:Biomarkers; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D051957:MSX1 Transcription Factor; C084119:MSX2 protein; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D051153:Wnt Proteins; D051155:Wnt1 Protein; C495246:Wnt1 protein, mouse; D029961:Zebrafish Proteins