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Specification of mesodermal pattern in Xenopus laevis by interactions between Brachyury, noggin and Xwnt‐8.
Author(s) -
Cunliffe V.,
Smith J.C.
Publication year - 1994
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1994.tb06268.x
Subject(s) - noggin , biology , brachyury , xenopus , developmental biology , notochord , polarity in embryogenesis , anatomy , mesoderm , genetics , embryo , embryogenesis , embryonic stem cell , gastrulation , bone morphogenetic protein , gene
We demonstrate that the nuclear, sequence‐specific DNA‐binding protein Xbra causes dorsal mesodermal differentiation of animal cap ectoderm when co‐expressed with the secreted proteins noggin and Xwnt‐8. None of these molecules causes dorsal mesoderm formation when expressed alone. Co‐expression of Xenopus Brachyury (Xbra) mRNA with noggin mRNA in animal caps specifies the main dorsal tissues, namely muscle, notochord and neural tissue. Co‐expression of Xbra with Xwnt‐8, in contrast, converts animal caps to muscle masses. We have previously shown that expression of Xbra alone in animal caps is sufficient to specify ventral mesoderm which expresses Xhox3 and low levels of muscle‐specific actin. We now conclude that the putative transcription factor Xbra defines a cell state in the vertebrate embryo which can respond to diffusible dorsal signals such as noggin and Xwnt‐8, resulting in dorsal mesodermal differentiation. In the absence of such dorsal signals Xbra causes ventral mesodermal differentiation. This state is only partially maintained after the mid‐blastula transition as it permits the dorsal response to zygotically expressed noggin but it does not allow a dorsal response to zygotically expressed Xwnt‐8, which elicits only ventral mesodermal differentiation.