Fig. 2. Developmental expression of Xenopus Mad. (A) A developmental northern blot of total embryonic RNA shows that XMad is maternal and expressed at all stages of early development. Three transcripts are detected with the sizes (in kb) indicated on the left. The most abundant mRNA is 3.4 kb, and minor transcripts of 4.3 kb and 3.0 kb are also detected. It is not known whether these transcripts derive from closely related genes or splicing variants. Lane numbers correspond to developmental stages (Nieuwkoop and Faber, 1967): (7, 9) blastula, (11) gastrula, (15, 18) neurula, (26) tailbud tadpole and (38) swimming tadpole. (B) In situ hybridization shows that XMad transcripts are uniformly distributed in the early gastrula (stage 10). Dense staining covers the entire prospective ectoderm and marginal zone, but vegetal cells (the lighter region) do not stain efficiently by this procedure (Harland, 1991). A northern blot on isolated dorsal, ventral, animal and vegetal regions confirmed the uniformity of XMad expression at early stages (not shown). (C) A mid-gastrula embryo (stage 12) split sagitally reveals that XMad is expressed in the ectoderm and neurectoderm (arrows mark the ectodermal-mesodermal boundary), 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. (D) At tailbud tadpole stage 26 XMad expression is high in the central nervous system and head. (E) A close-up of the head of the embryo in D, highlighting XMad expression in the brain (b), eye (e) and head neural crest derivatives (mc, mandibular crest; hc, hyoid crest; abc, anterior branchial crest; pbc, posterior branchial crest). Expression in the otic vesicle, between the hyoid crest and anterior branchial crest, is also visible. Scale bars, 0.1 mm.
Image published in: Thomsen GH (1996)
Copyright © 1996. Image reproduced with permission of the publisher and the copyright holder. This is an Open Access article distributed under the terms of the Creative Commons Attribution License.
| Gene | Synonyms | Species | Stage(s) | Tissue |
|---|---|---|---|---|
| smad1.L | MLP, smad-1, smad1-a, smad1-b, XMad, Xmad1, Xsmad1 | X. laevis | Sometime during NF stage 10 to NF stage 26 | cranial neural crest mandibular crest hyoid crest branchial crest pharyngeal arch otic vesicle neural tube posterior neural tube anterior neural tube central nervous system brain spinal cord |
| smad1.L | MLP, smad-1, smad1-a, smad1-b, XMad, Xmad1, Xsmad1 | X. laevis | Throughout NF stage 12 | ectoderm neuroectoderm |
| smad1.L | MLP, smad-1, smad1-a, smad1-b, XMad, Xmad1, Xsmad1 | X. laevis | Throughout NF stage 10 | ectoderm marginal zone animal hemisphere |
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