Mad; neural crest, ectoderm, mesoderm

Mad, nucleic acid

Mad, Mothers against Decapentaplegic, was first isolated in Drosophila genetic screens searching for enhancers of the dpp mutant phenotype. The Mad protein has no significant homology to other known proteins. The Xenopus ortholog appears to transduce the BMP signal during mesoderm patterning, and overexpression of Mad produces a similar ventralized phenotype to overexpression of BMP-4 or BMP-2, and XMad expression can rescue the embryonic phenotype caused by expression of dominant-negative BMP receptor. After nonlocalized expression in early embryos, the major site of expression in tailbud stages is in the cranial crest.

Xenopus Mad has been cloned by Jerry Thomsen at Stony Brook and by Jon Graf and Doug Melton at Harvard.

A. B.
A. A mid-gastrula embryo (stage 12) split sagitally reveals that XMad is expressed in the ectoderm and neurectoderm (arrows mark the ectodermal-mesodermal boundry), and expression in the underlying mesoderm is greater in the posterior, adjacent to the yolk plug (YP). This embryo is lightly pigmented and the brown line anterior to the yolk corresponds to involuted bottle cells. The embryo is positioned with the anterior to the left and dorsal at the top.
B. At tailbud tadpole stage 26 XMad expression is high in the central nervous system and head. XMad expression is observed in the brain , eye, and head neural crest derivatives (mandibular crest, hyoid crest, anterior branchial crest, posterior branchial crest). Expression in the otic vesicle, between the hyoid crest and anterior branchial crest, is also visible.
These images are Copyright © Company of Biologists, 1996.

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Reference; Thomsen, G.H. (1996) Xenopus mothers against decapentaplegic is an embryonic ventralizing agent that acts downstream of the BMP-2/4 receptor. Development, in press.
Plasmid name; XMad. XMad cDNA in CS2+
Download sequence
For antisense probe;
Available from; Jerry Thomsen

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