Patterning of the mesoderm involves several threshold responses to BMP-4 and Xwnt-8.
Two secreted signaling molecules, Xwnt-8 and BMP-4, play an essential role in the dorso-ventral patterning of the mesoderm in Xenopus. Here we investigate how the Wnt-8 and the BMP-4 pathways are connected and how they regulate target genes in the lateral and ventral marginal zone. BMP-4 regulates the transcription of Xwnt-8 in a threshold dependent manner. High levels of BMP-4 induce the expression of the Wnt antagonist sizzled in the ventral marginal zone, independent of Xwnt-8 signaling. Xwnt-8 induces the early muscle marker myf-5 in the lateral marginal zone in a BMP independent manner. The expression of the homeobox gene Xvent-1 can be modulated through both the BMP-4 and the Xwnt-8 pathways. The spatial distribution and the level of BMP-4 activity in the lateral and ventral marginal zone is reflected in the dynamic expression pattern of Xwnt-8. The data support the view that Xwnt-8 is involved in the specification of lateral (somitogenic) mesoderm and BMP-4 in the specification of ventral mesoderm.
Marom
K
K
Department of Cellular Biochemistry, Faculty of Medicine, Hebrew University, Jerusalem, Israel.
Fainsod
A
A
Steinbeisser
H
H
D000818:Animals; D019521:Body Patterning; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D017403:In Situ Hybridization; D018021:Lithium Chloride / Q000494:pharmacology; D008648:Mesoderm / Q000187:drug effects / Q000502:physiology*; D009124:Muscle Proteins / Q000378:metabolism; D051787:Myogenic Regulatory Factor 5; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012313:RNA / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators; D014158:Transcription, Genetic; D051153:Wnt Proteins; D014981:Xenopus; D029867:Xenopus Proteins; D029961:Zebrafish Proteins
D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D009124:Muscle Proteins; C497419:Myf5 protein, Xenopus; D051787:Myogenic Regulatory Factor 5; D011506:Proteins; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; C525812:bmp4 protein, Xenopus; C525813:bmp4 protein, zebrafish; C109976:szl protein, Xenopus; C495248:wnt8a protein, Xenopus; D012313:RNA; D018021:Lithium Chloride