File:Eye-neural crest signaling.jpg

Wnt mediates lens repression by neural crest cells and Transforming growth factor-β

• Transforming growth factor β (TGF-β)
• Neural crest cell (NCC)

(a–c) Wnt2b (blue) gene expression during neural crest cell (NCC) migration:

(a) Whole-mount embryo showing the forebrain section used in panel b and the midbrains section used in panel c. (b) Forebrain level section stained for Wnt2b; (c) midbrain level section stained for Wnt2b.

(d) Forebrain level section stained for Axin2 gene expression (blue). (e) Midbrain level section showing Axin2 expression. All sections are immunostained for NCC-specific HNK1 (brown). Arrowheads indicate gene expression in non-lens ectoderm.

(f–h) Presumtive lens ectoderm (PLE) explants were cultured alone or in combination with NCC or SB431542 and assayed for Wnt2b gene expression (blue) and HNK1 (brown): (f) PLE alone; (g) PLE+NCC; (h) PLE+NCC+SB431542.

(i, j) PLE explants were cultured alone or with Activin A and assayed for Wnt2b gene expression: (i) PLE alone; (j) PLE+Activin A.

(k, l) Wnt2b gene expression (blue) following in ovo ablation of premigratory NCCs: (k) control embryo; (l) NCC ablated embryo. Compare Wnt2b expression in the brain (white arrowheads) with non-lens surface ectoderm (yellow arrowheads).

(m, n) Wnt2b gene expression (blue) following in ovo electroporation of expression vectors encoding green fluorescent protein (GFP) or Smad7+GFP: (m) GFP; (n) Smad7+GFP.

(o–q) PLE explants were cultured alone or in combination with Activin A or N-Fz8 and assayed for Pax6 gene expression (blue): (o) PLE alone; (p) PLE+Activin A; (q) PLE+Activin A+N-Fz8.

(r) Proposed molecular model to explain TGF-β- and Wnt-mediated lens restriction. Broken lines: interactions inferred from the literature.

(s) Proposed embryological model summarizing how NCCs organize the eye: NCCs (blue) secrete TGF-βs, which signal to the non-lens ectoderm and dorsal optic vesicle. As a consequence, Wnt2b (red) is induced, and together they repress lens formation in the non-lens ectoderm. This leads to the alignment of Pax6 expression in the future lens and neural retina (grey).

Scale bars: a, 500 μm; b, 50 μm for panels b–e; f, 50 μm for panels f–j, o–q; k, 250 μm for panels k, l; m, 250 μm for panels m, n.

Links: Lens Development | Lens repression by neural crest cells | Proposed model how NCCs organize the eye | molecular model to explain TGF-β- and Wnt-mediated lens restriction

Original image name: Figure 3 http://www.nature.com/ncomms/journal/v2/n4/fig_tab/ncomms1269_F3.html

Reference

Grocott T, Johnson S, Bailey AP, Streit A. Neural crest cells organize the eye via TGF-β and canonical Wnt signalling. Nat Commun. 2011 Apr;2:265. PMID21468017 | Nat Commun.

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