Figure 6
From: Mesodermal origin of median fin mesenchyme and tail muscle in amphibian larvae
Expression of molecular markers for epidermis, mesoderm and neural crest.
In situ hybridization of axolotl neurulae (stage 15) with keratin (A, A’), sox2 (B, B’ and B”), brachyury (C, C’ and C”) and tfap2a (D, D’ and D”) riboprobes. A–D, dorsal views of whole embryos. A’–D’, posterior views of whole embryos. A”–D”, posterior aspects of anterior halves of bisected embryos. Sectioning planes are indicated by dashed lines and run through the middle of region 3 fold/plate (A’, C’ and D’) or through region 2 (B). Red double-dashed lines indicate neural folds; prospective epidermis is lateral and neural plate medial to the folds. E, fate of plate/fold region3 based on in situ hybridization with brachyury (bra), sox2 and tfap2a riboprobes (neurula stage 15). Brachyury: positive in the centre of plate region 3; tfap2a: positive.in cranial and trunk neural folds until the anterior part of fold region 3; sox2: positive in cranial and region 2 plate. F and G, transverse sections through neural fold/plate (stage 15) in region 1–2 (F) and middle of region3 (G). Axial differences of neural plate and neural crest potential become evident (neuroectoderm vs. mesoderm and neural crest vs. neural fold, respectively). These data and the indication of the distribution of the tfap2-, sox2- and bra-zones in E are based on in situ hybridization (see above). nc in F, prospective neural crest; nfo in G, tfap2a-negative neural fold tissue, probably mesoderm. Number of experiments: about 20 for each riboprobe. White arrowheads in A‘-D‘ point to blastopore. Abbreviations: not, notochord; nfo, neural fold; cr. nfo, cranial neurl fold; npl, neural plate; ax, axial mesoderm; pax, paraxial mesoderm. Scale bars, 500 μm (D’) and 200 μm (D”).
