Limits...
Neural crest cells organize the eye via TGF-β and canonical Wnt signalling.

Grocott T, Johnson S, Bailey AP, Streit A - Nat Commun (2011)

Bottom Line: In vertebrates, the lens and retina arise from different embryonic tissues raising the question of how they are aligned to form a functional eye.Here we show, using the chick as a model system, that neural crest-derived transforming growth factor-βs activate both Smad3 and canonical Wnt signalling in the adjacent ectoderm to position the lens next to the retina.They do so by controlling Pax6 activity: although Smad3 may inhibit Pax6 protein function, its sustained downregulation requires transcriptional repression by Wnt-initiated β-catenin.

View Article: PubMed Central - PubMed

Affiliation: Department of Craniofacial Development, King's College London, Guy's Campus, London SE1 9RT, UK.

Show MeSH

Related in: MedlinePlus

β-Catenin inhibits lens formation, and Wnt signalling is required for lens repression by NCCs.(a–c). Presumptive lens ectoderm (PLE) was electroporated with expression vector encoding green fluorescent protein (GFP) and embryos were cultured for 48 h. (a) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (b) GFP and δ-crystallin staining only; (c) δ-crystallin staining only. (d–i) PLE was electroporated with caβ-catenin+GFP and embryos were cultured for 24 or 48 h. (d–f) Twenty-four hours: (d) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (e) GFP and δ-crystallin staining only; (f) δ-crystallin staining only. (g–i) Forty-eight hours: (g) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (h) GFP and δ-crystallin staining only; (i) δ-crystallin staining only. (j) Mean proportion of GFP+ electroporated cells within the lens that also express δ-crystallin protein. GFP control: n=3 lenses; 66 of 87 electroporated cells express δ-crystallin. caβ-catenin: n=5 lenses; 27 of 77 electroporated cells δ-crystallin. Error bars: ±1 s.d. (k–m) PLE explants were cultured alone or in combination with neural crest cells (NCCs) or N-Fz8 and assayed for lens (δ-crystallin; brown) and NCC (CRABP1; blue) gene expression: (k) PLE alone; (l) PLE+NCC; (m) PLE+NCC+N-Fz8. (n) Model for lens inhibition by TGF-β and canonical Wnt signalling. Scale bars: a, 50 μm for panels a–i; k, 50 μm for panels k–m.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3104559&req=5

f2: β-Catenin inhibits lens formation, and Wnt signalling is required for lens repression by NCCs.(a–c). Presumptive lens ectoderm (PLE) was electroporated with expression vector encoding green fluorescent protein (GFP) and embryos were cultured for 48 h. (a) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (b) GFP and δ-crystallin staining only; (c) δ-crystallin staining only. (d–i) PLE was electroporated with caβ-catenin+GFP and embryos were cultured for 24 or 48 h. (d–f) Twenty-four hours: (d) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (e) GFP and δ-crystallin staining only; (f) δ-crystallin staining only. (g–i) Forty-eight hours: (g) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (h) GFP and δ-crystallin staining only; (i) δ-crystallin staining only. (j) Mean proportion of GFP+ electroporated cells within the lens that also express δ-crystallin protein. GFP control: n=3 lenses; 66 of 87 electroporated cells express δ-crystallin. caβ-catenin: n=5 lenses; 27 of 77 electroporated cells δ-crystallin. Error bars: ±1 s.d. (k–m) PLE explants were cultured alone or in combination with neural crest cells (NCCs) or N-Fz8 and assayed for lens (δ-crystallin; brown) and NCC (CRABP1; blue) gene expression: (k) PLE alone; (l) PLE+NCC; (m) PLE+NCC+N-Fz8. (n) Model for lens inhibition by TGF-β and canonical Wnt signalling. Scale bars: a, 50 μm for panels a–i; k, 50 μm for panels k–m.

Mentions: In mouse, canonical Wnt signalling suppresses lens development20. Consistent with this, we found that overexpression of constitutively active β-catenin in PLE prevented the expression of δ-crystallin. Although 83% of control cells were δ-crystallin+ (66/87 cells in three lenses; Fig. 2a–c), this was reduced to 35% when canonical Wnt signalling was activated (27/77 cells in five lenses; Fig. 2d–j). Interestingly, similar to caSmad3-expressing cells (Fig. 1d–f), those carrying β-catenin were excluded from the lens over time: after 24 h β-catenin+/δ-crystallin− cells were found in the lens placode (Fig. 2d–f), but were mostly absent from the lens after 48 h (Fig. 2g–i). If Wnt signalling is involved in the residual lens-repressing activity of NCCs, Wnt inhibition should rescue lens development in the presence of NCCs. To test this, we cocultured NCCs and PLE with the Wnt antagonist N-Fz8. Indeed, inhibition of Wnt signalling rescued δ-crystallin expression (Fig. 2k–m), suggesting that Wnt is required for lens repression by NCCs and suppresses lens formation through β-catenin (Fig. 2n).


Neural crest cells organize the eye via TGF-β and canonical Wnt signalling.

Grocott T, Johnson S, Bailey AP, Streit A - Nat Commun (2011)

β-Catenin inhibits lens formation, and Wnt signalling is required for lens repression by NCCs.(a–c). Presumptive lens ectoderm (PLE) was electroporated with expression vector encoding green fluorescent protein (GFP) and embryos were cultured for 48 h. (a) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (b) GFP and δ-crystallin staining only; (c) δ-crystallin staining only. (d–i) PLE was electroporated with caβ-catenin+GFP and embryos were cultured for 24 or 48 h. (d–f) Twenty-four hours: (d) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (e) GFP and δ-crystallin staining only; (f) δ-crystallin staining only. (g–i) Forty-eight hours: (g) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (h) GFP and δ-crystallin staining only; (i) δ-crystallin staining only. (j) Mean proportion of GFP+ electroporated cells within the lens that also express δ-crystallin protein. GFP control: n=3 lenses; 66 of 87 electroporated cells express δ-crystallin. caβ-catenin: n=5 lenses; 27 of 77 electroporated cells δ-crystallin. Error bars: ±1 s.d. (k–m) PLE explants were cultured alone or in combination with neural crest cells (NCCs) or N-Fz8 and assayed for lens (δ-crystallin; brown) and NCC (CRABP1; blue) gene expression: (k) PLE alone; (l) PLE+NCC; (m) PLE+NCC+N-Fz8. (n) Model for lens inhibition by TGF-β and canonical Wnt signalling. Scale bars: a, 50 μm for panels a–i; k, 50 μm for panels k–m.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3104559&req=5

f2: β-Catenin inhibits lens formation, and Wnt signalling is required for lens repression by NCCs.(a–c). Presumptive lens ectoderm (PLE) was electroporated with expression vector encoding green fluorescent protein (GFP) and embryos were cultured for 48 h. (a) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (b) GFP and δ-crystallin staining only; (c) δ-crystallin staining only. (d–i) PLE was electroporated with caβ-catenin+GFP and embryos were cultured for 24 or 48 h. (d–f) Twenty-four hours: (d) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (e) GFP and δ-crystallin staining only; (f) δ-crystallin staining only. (g–i) Forty-eight hours: (g) GFP-expressing cells (green) were stained for δ-crystallin protein (magenta) and cell nuclei (grey); (h) GFP and δ-crystallin staining only; (i) δ-crystallin staining only. (j) Mean proportion of GFP+ electroporated cells within the lens that also express δ-crystallin protein. GFP control: n=3 lenses; 66 of 87 electroporated cells express δ-crystallin. caβ-catenin: n=5 lenses; 27 of 77 electroporated cells δ-crystallin. Error bars: ±1 s.d. (k–m) PLE explants were cultured alone or in combination with neural crest cells (NCCs) or N-Fz8 and assayed for lens (δ-crystallin; brown) and NCC (CRABP1; blue) gene expression: (k) PLE alone; (l) PLE+NCC; (m) PLE+NCC+N-Fz8. (n) Model for lens inhibition by TGF-β and canonical Wnt signalling. Scale bars: a, 50 μm for panels a–i; k, 50 μm for panels k–m.
Mentions: In mouse, canonical Wnt signalling suppresses lens development20. Consistent with this, we found that overexpression of constitutively active β-catenin in PLE prevented the expression of δ-crystallin. Although 83% of control cells were δ-crystallin+ (66/87 cells in three lenses; Fig. 2a–c), this was reduced to 35% when canonical Wnt signalling was activated (27/77 cells in five lenses; Fig. 2d–j). Interestingly, similar to caSmad3-expressing cells (Fig. 1d–f), those carrying β-catenin were excluded from the lens over time: after 24 h β-catenin+/δ-crystallin− cells were found in the lens placode (Fig. 2d–f), but were mostly absent from the lens after 48 h (Fig. 2g–i). If Wnt signalling is involved in the residual lens-repressing activity of NCCs, Wnt inhibition should rescue lens development in the presence of NCCs. To test this, we cocultured NCCs and PLE with the Wnt antagonist N-Fz8. Indeed, inhibition of Wnt signalling rescued δ-crystallin expression (Fig. 2k–m), suggesting that Wnt is required for lens repression by NCCs and suppresses lens formation through β-catenin (Fig. 2n).

Bottom Line: In vertebrates, the lens and retina arise from different embryonic tissues raising the question of how they are aligned to form a functional eye.Here we show, using the chick as a model system, that neural crest-derived transforming growth factor-βs activate both Smad3 and canonical Wnt signalling in the adjacent ectoderm to position the lens next to the retina.They do so by controlling Pax6 activity: although Smad3 may inhibit Pax6 protein function, its sustained downregulation requires transcriptional repression by Wnt-initiated β-catenin.

View Article: PubMed Central - PubMed

Affiliation: Department of Craniofacial Development, King's College London, Guy's Campus, London SE1 9RT, UK.

Show MeSH
Related in: MedlinePlus