Ventral mesodermal patterning in Xenopus embryos: Expression patterns and activities of BMP-2 and BMP-4
Article first published online: 6 FEB 2005
Copyright © 1995 Wiley-Liss, Inc.
Volume 17, Issue 1, pages 78–89, 1995
How to Cite
Hemmati-Brivanlou, A. and Thomsen, G. H. (1995), Ventral mesodermal patterning in Xenopus embryos: Expression patterns and activities of BMP-2 and BMP-4. Dev. Genet., 17: 78–89. doi: 10.1002/dvg.1020170109
- Issue published online: 6 FEB 2005
- Article first published online: 6 FEB 2005
- Manuscript Accepted: 16 MAR 1995
- Manuscript Received: 23 JAN 1995
- bone morpho-genetic proteins;
- TGF-β receptors;
We provide a comparative analysis of the expression patterns and ventral mesoderm-inducing properties of Xenopus BMP-2 and BMP-4. Transcripts for BMP-2 and BMP-4 are maternally stored in eggs, and zygotic expression of these genes is uniform in the ectoderm and mesoderm in late blastulae. During gastrulation, BMP-2 is expressed at a low level throughout the ectoderm and marginal zone, but at early neurula stages a patch of dorso-anterior cells displays enhanced expression. In contrast, BMP-4 transcripts are restricted to the ventrolateral marginal zone during gastrulation, and in late gastrula and early neurula BMP-4 is expressed in the epidermis but not the neural plate. At post-neurula stages, BMP-2 and BMP-4 transcripts are associated with a variety of mesodermal structures, including the pharyngeal pouches, heart, blood island, and blastopore. At tailbud stages, BMP-2 and BMP-4 are expressed in neural tissues including the neural tube and brain. In mesoderm induction assays, BMP-2 and BMP-4 induce Xhox3, an early ventral-posterior mesoderm marker, and larval βT1 globin, a marker for red blood cells. Induction of red blood cells in response to BMP-4 was demonstrated by staining with a hemoglobin-specific reagent. Little is known about factors that induce hematopoietic lineages in vertebrates, and these results provide evidence linking BMP activity and blood differentiation. Globin induction by BMP-2 and BMP-4 is blocked by co-expression of a dominant-negative activin receptor, suggesting that either endogenous activin signals are required for BMP-mediated induction, or that the trancated activin receptor interferes with signaling by BMP receptors. In assays on marginal zone explants, we demonstrate that BMP-4 respecifies dorsal mesoderm to form ventral mesoderm, consistent with its ability to induce blood and to ventralize embryos. BMP-2, however, does not display such activity. The findings extend and support evidence that BMP-2 and BMP-4 function in ventral mesoderm induction and patterning in Xenopus. Our data furthermore high light the multiple functions these factors fulfill during early vertebrate embryogenesis. © 1995 Wiley-Liss, Inc.