Xmsx-1 modifies mesodermal tissue pattern along dorsoventral axis in Xenopus laevis embryo.
This study analyzes the expression and the function of Xenopus msx-1 (Xmsx-1) in embryos, in relation to the ventralizing activity of bone morphogenetic protein-4 (BMP-4). Expression of Xmsx-1 was increased in UV-treated ventralized embryos and decreased in LiCl-treated dorsalized embryos at the neurula stage (stage 14). Whole-mount in situ hybridization analysis showed that Xmsx-1 is expressed in marginal zone and animal pole areas, laterally and ventrally, but not dorsally, at mid-gastrula (stage 11) and late-gastrula (stage 13) stages. Injection of BMP-4 RNA, but not activin RNA, induced Xmsx-1 expression in the dorsal marginal zone at the early gastrula stage (stage 10+), and introduction of a dominant negative form of BMP-4 receptor RNA suppressed Xmsx-1 expression in animal cap and ventral marginal zone explants at stage 14. Thus, Xmsx-1 is a target gene specifically regulated by BMP-4 signaling. Embryos injected with Xmsx-1 RNA in dorsal blastomeres at the 4-cell stage exhibited a ventralized phenotype, with microcephaly and swollen abdomen. Histological observation and immunostaining revealed that these embryos had a large block of muscle tissue in the dorsal mesodermal area instead of notochord. On the basis of molecular marker analysis, however, the injection of Xmsx-1 RNA did not induce the expression of alpha-globin, nor reduce cardiac alpha-actin in dorsal marginal zone explants. Furthermore, a significant amount of alpha-actin was induced and alpha-globin was turned off in the ventral marginal zone explants injected with Xmsx-1. These results indicated that Xmsx-1 is a target gene of BMP-4 signaling, but possesses a distinct activity on dorsal-ventral patterning of mesodermal tissues.
Maeda
R
R
Department of Biology, Faculty of Science, Niigata University, Japan.
Kobayashi
A
A
Sekine
R
R
Lin
J J
JJ
Kung
H
H
Maéno
M
M
D000818:Animals; D019521:Body Patterning; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D005775:Gastrula; D018398:Homeodomain Proteins / Q000096:biosynthesis*; D051957:MSX1 Transcription Factor; D008648:Mesoderm; D009132:Muscles / Q000196:embryology; D009420:Nervous System / Q000196:embryology; D015398:Signal Transduction; D014157:Transcription Factors; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology*
D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D018398:Homeodomain Proteins; D051957:MSX1 Transcription Factor; C497996:MSX1 protein, Xenopus; D014157:Transcription Factors; D029867:Xenopus Proteins; C525812:bmp4 protein, Xenopus