FIGURE SUMMARY
Title

Goosecoid expression in neurectoderm and mesendoderm is disrupted in zebrafish cyclops gastrulas

Authors
Thisse, C., Thisse, B., Halpern, M.E., and Postlethwait, J.H.
Source
Full text @ Dev. Biol.

Localization of gsc transcripts by in situ hybridization in wild-type late blastula and early gastrula. (a) Lateral view of an embryo at 45% epiboly (late blastula) showing gsc transcripts restricted to a group of deep cells at the dorsal margin of the embryo (animal pole up; dorsal, right). (b) Animal pole view of the same embryo. The territory of goosecoid expression occupies about 60° of the circumference of the embryo at the dorsal margin (dorsal, right; ventral, left). (e) Lateral view of an embryo at 60% epiboly (early gastrula). All goosecoid-expressing cells have involuted and the territory has begun to extend toward the animal pole. (d) Dorsal view of the same embryo showing that the gsc-expression territory now occupies the central part of the embryonic shield, the precursor of the prechordal plate (animal pole, up).

Localization of gsc transcripts by in situ hybridization during gastrulation in wild-type embryos. (a) Whole mount at 70% epiboly in lateral view. gsc RNA is restricted to axial mesendoderm (animal pole up; dorsal, right). (b) Lateral view of a whole mount embryo at 80% epiboly showing both mesendodermal and ectodermal (between the arrowheads) gsc expression (animal pole up; dorsal, right). (c) Animal pole view at the end of gastrulation, focusing on the new anterolateral expression of gsc (anterior, left). (d) Transverse section at 75% epiboly. Abundant gsc transcripts are detected in mesendoderm and smaller quantities are observed for the first time in ectodermal cells in contact with axial mesendoderm (dorsal, top; ventral, bottom). (e) Transverse section at 90% epiboly. Two gradients of gsc transcripts are detected in ectoderm: one along ventrodorsal and the other along mediolateral coordinates, both decreasing from a maximum in the ventral midline ectoderm. (f) Sagittal section at the end of gastrulation. In the mesendoderm, staining extends from the anterior tip of the embryo, including the presumptive hatching gland (left) to the middle of the gsc-expressing ectodermal territory. In ectoderm, the anterior labeling on top of the presumptive hatching gland is continuous with the anterolateral domain shown in (b). Note the intense labeling in axial ectodermal cells directly in contact with the axial mesendoderm. This labeling decreases in neighboring cells dorsally and posteriorly (anterior, left; dorsal, top). Scale bars, 100 μm (a-c), 40 μm (d-f).

Localization of gsc RNA in cyclops (cycb16) mutant embryos. (a) Side view of a whole mount cyclops embryo at 70% epiboly. Expression of gsc in the mesendoderm is reduced compared to wild-type control (Fig. 2a) (animal pole up; dorsal, right). (b) Dorsal view of the same embryo. gsc is confined to the most anterior part of the mesendodermal layer and encompasses only a portion of the wild-type gsc territory shown in (c) (anterior, top). (c) Dorsal view of a wild-type sibling embryo at 70% epiboly, showing gsc expression in the entire axial mesendoderm (compare to (b); see also Fig. 2a) (anterior, top). (d) Side view of a cyclops embryo at 95% epiboly, gsc expression is not detected in the ectoderm and is reduced in the mesodermal territory compared to wild-type expression shown in (e) (anterior, upper left). (e) Wild-type sibling embryo at 95% epiboly. Scale bars, 100 μm. Phenotypically mutant embryos were approximately one-quarter (23.4% = 55/235) of the total, as expected for simple Mendelian segregation.

Extent of cephalic mesendodermal alteration in cycbl6 mutant embryos. (a) Side view and (b) dorsal view of the same wild-type embryo at 100 % epiboly labeled with hatching gland gene 1 (hggl) RNA probe. (c) Side view and (d) dorsal view of a cyclops embryo from the same in situ hybridization reaction (24.1% mutants = 36/149), showing strong reduction of the hatching gland territory. (e) Animal pole view of a wild-type embryo at 100% epiboly labeled with snail2 RNA probe, snail2 RNA is detected in neural crest cells, in a subset Of paraxial and lateral cephalic mesoderm, and in the prechordal plate caudal to the hatching gland territory (unpublished data). In wild type, the axial mesendoderma! staining is continuous and easily distinguishable from the surrounding loose network of paraxial and lateral mesendodermal label. (f) Animal pole view of a cyclops embryo (22.4% mutants = 11/49). Labeling of the prechordal plate is greatly reduced and apparently replaced by staining characteristic of snail2 in paraxial mesendoderm. As an internal control, neural crest cell labeling (arrowheads) appears normal in the cyclops embryo. Scale bars, 100 μm (a and c; dorsal on right; b, d-f, anterior on top).

Acknowledgments
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Reprinted from Developmental Biology, 164, Thisse, C., Thisse, B., Halpern, M.E., and Postlethwait, J.H., Goosecoid expression in neurectoderm and mesendoderm is disrupted in zebrafish cyclops gastrulas, 420-429, Copyright (1994) with permission from Elsevier. Full text @ Dev. Biol.