Limits...
Def6 is required for convergent extension movements during zebrafish gastrulation downstream of Wnt5b signaling.

Goudevenou K, Martin P, Yeh YJ, Jones P, Sablitzky F - PLoS ONE (2011)

Bottom Line: Wnt signaling results in downstream activation of Rho GTPases that in turn regulate actin cytoskeleton rearrangements essential for co-ordinated CE cell movement.Here we show that def6, a novel GEF, regulates CE cell movement during zebrafish gastrulation.In addition, by knocking down both def6 and Wnt11, we show that def6 synergises with the Wnt11 signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: School of Biology, Queen's Medical Centre, The University of Nottingham, Nottingham, United Kingdom.

ABSTRACT
During gastrulation, convergent extension (CE) cell movements are regulated through the non-canonical Wnt signaling pathway. Wnt signaling results in downstream activation of Rho GTPases that in turn regulate actin cytoskeleton rearrangements essential for co-ordinated CE cell movement. Rho GTPases are bi-molecular switches that are inactive in their GDP-bound stage but can be activated to bind GTP through guanine nucleotide exchange factors (GEFs). Here we show that def6, a novel GEF, regulates CE cell movement during zebrafish gastrulation. Def6 morphants exhibit broadened and shortened body axis with normal cell fate specification, reminiscent of the zebrafish mutants silberblick and pipetail that lack Wnt11 or Wnt5b, respectively. Indeed, def6 morphants phenocopy Wnt5b mutants and ectopic overexpression of def6 essentially rescues Wnt5b morphants, indicating a novel role for def6 as a central GEF downstream of Wnt5b signaling. In addition, by knocking down both def6 and Wnt11, we show that def6 synergises with the Wnt11 signaling pathway.

Show MeSH

Related in: MedlinePlus

Def6 MO induced-defects resemble those of wnt5b morphants.Embryos were injected with def6 MO (2.5 ng) or wnt5b MO (5 ng) and development was assessed at different stages. (A–C) 1-somite stage, arrowheads indicate the anterior- and posterior-most structures of the embryos. (D) Statistical analysis of the angle between the anterior- and posterior- most embryonic structures. (E–G) 25-somite stage, def6 and wnt5b MO-injected embryos show brain, somite and tail defects when compared to wt embryos. The tail abnormalities are magnified on E'–G''.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3198796&req=5

pone-0026548-g006: Def6 MO induced-defects resemble those of wnt5b morphants.Embryos were injected with def6 MO (2.5 ng) or wnt5b MO (5 ng) and development was assessed at different stages. (A–C) 1-somite stage, arrowheads indicate the anterior- and posterior-most structures of the embryos. (D) Statistical analysis of the angle between the anterior- and posterior- most embryonic structures. (E–G) 25-somite stage, def6 and wnt5b MO-injected embryos show brain, somite and tail defects when compared to wt embryos. The tail abnormalities are magnified on E'–G''.

Mentions: The CE movement defects observed in def6 MO-injected embryos strongly resembled previously published ppt/wnt5b mutants and/or morphants [11], [29]. At tail-bud stage, the embryonic axis failed to move around the yolk (Figure 6A–C, arrowheads). This effect was statistically significant (Figure 6D), with the def6 MO having a stronger effect than the wnt5b MO at the concentrations of MO tested. At later stages, embryos were shorter with truncated tails (Figure 6E–G). At 4dpf, def6 morphants developed the ‘hammerhead’-like phenotype, a hallmark of ppt/wnt5b mutants (Figure 7A–C). A direct side-by-side comparison of def6 and wnt5b morphants was therefore undertaken. Alcian blue staining of the cartilaginous structures in the region of the head indicated impaired growth of the head skeleton in both def6 and wnt5b morphants (Figure 7D–F). In detail, Meckel's cartilage (Figure 7D–F, black arrowhead) did not extend as far anteriorly beyond the eyes as in wt embryos. Also, the ceratohyal was posteriorly shifted and thicker in def6 and wnt5b MO-injected embryos in comparison to wt embryos (Figure 7 D–F, red arrowhead). Morphometric analysis indicated that both of these changes were significantly different between def6 morphants and wild-type controls (Figure 7G and H), similar to wnt5b morphants.


Def6 is required for convergent extension movements during zebrafish gastrulation downstream of Wnt5b signaling.

Goudevenou K, Martin P, Yeh YJ, Jones P, Sablitzky F - PLoS ONE (2011)

Def6 MO induced-defects resemble those of wnt5b morphants.Embryos were injected with def6 MO (2.5 ng) or wnt5b MO (5 ng) and development was assessed at different stages. (A–C) 1-somite stage, arrowheads indicate the anterior- and posterior-most structures of the embryos. (D) Statistical analysis of the angle between the anterior- and posterior- most embryonic structures. (E–G) 25-somite stage, def6 and wnt5b MO-injected embryos show brain, somite and tail defects when compared to wt embryos. The tail abnormalities are magnified on E'–G''.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198796&req=5

pone-0026548-g006: Def6 MO induced-defects resemble those of wnt5b morphants.Embryos were injected with def6 MO (2.5 ng) or wnt5b MO (5 ng) and development was assessed at different stages. (A–C) 1-somite stage, arrowheads indicate the anterior- and posterior-most structures of the embryos. (D) Statistical analysis of the angle between the anterior- and posterior- most embryonic structures. (E–G) 25-somite stage, def6 and wnt5b MO-injected embryos show brain, somite and tail defects when compared to wt embryos. The tail abnormalities are magnified on E'–G''.
Mentions: The CE movement defects observed in def6 MO-injected embryos strongly resembled previously published ppt/wnt5b mutants and/or morphants [11], [29]. At tail-bud stage, the embryonic axis failed to move around the yolk (Figure 6A–C, arrowheads). This effect was statistically significant (Figure 6D), with the def6 MO having a stronger effect than the wnt5b MO at the concentrations of MO tested. At later stages, embryos were shorter with truncated tails (Figure 6E–G). At 4dpf, def6 morphants developed the ‘hammerhead’-like phenotype, a hallmark of ppt/wnt5b mutants (Figure 7A–C). A direct side-by-side comparison of def6 and wnt5b morphants was therefore undertaken. Alcian blue staining of the cartilaginous structures in the region of the head indicated impaired growth of the head skeleton in both def6 and wnt5b morphants (Figure 7D–F). In detail, Meckel's cartilage (Figure 7D–F, black arrowhead) did not extend as far anteriorly beyond the eyes as in wt embryos. Also, the ceratohyal was posteriorly shifted and thicker in def6 and wnt5b MO-injected embryos in comparison to wt embryos (Figure 7 D–F, red arrowhead). Morphometric analysis indicated that both of these changes were significantly different between def6 morphants and wild-type controls (Figure 7G and H), similar to wnt5b morphants.

Bottom Line: Wnt signaling results in downstream activation of Rho GTPases that in turn regulate actin cytoskeleton rearrangements essential for co-ordinated CE cell movement.Here we show that def6, a novel GEF, regulates CE cell movement during zebrafish gastrulation.In addition, by knocking down both def6 and Wnt11, we show that def6 synergises with the Wnt11 signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: School of Biology, Queen's Medical Centre, The University of Nottingham, Nottingham, United Kingdom.

ABSTRACT
During gastrulation, convergent extension (CE) cell movements are regulated through the non-canonical Wnt signaling pathway. Wnt signaling results in downstream activation of Rho GTPases that in turn regulate actin cytoskeleton rearrangements essential for co-ordinated CE cell movement. Rho GTPases are bi-molecular switches that are inactive in their GDP-bound stage but can be activated to bind GTP through guanine nucleotide exchange factors (GEFs). Here we show that def6, a novel GEF, regulates CE cell movement during zebrafish gastrulation. Def6 morphants exhibit broadened and shortened body axis with normal cell fate specification, reminiscent of the zebrafish mutants silberblick and pipetail that lack Wnt11 or Wnt5b, respectively. Indeed, def6 morphants phenocopy Wnt5b mutants and ectopic overexpression of def6 essentially rescues Wnt5b morphants, indicating a novel role for def6 as a central GEF downstream of Wnt5b signaling. In addition, by knocking down both def6 and Wnt11, we show that def6 synergises with the Wnt11 signaling pathway.

Show MeSH
Related in: MedlinePlus