N-Cadherin Locks Left-Right Asymmetry by Ending the Leftward Movement of Hensen’s Node Cells

Abstract

The stereotypic left-right (LR) asymmetric distribution of internal organs is due to an asymmetric molecular cascade in the lateral plate mesoderm (LPM) that is originated at the embryonic node. In chicken embryos, molecular asymmetries at Hensen's node are created by leftward cell movements that occur transiently. What terminates these movements, and, moreover, what is the impact of prolonging them on the LR asymmetry cascade? We show that leftward movements last longer when N-cadherin function is blocked and cease prematurely when N-cadherin is overexpressed on the right side of the node. The prolonged leftward movements lead to loss of asymmetric expression of fgf8 and nodal at the node region. This originates an abnormal expression of the asymmetric genes cer1 and snai1 in the LPM, resulting in mispositioned hearts. We conclude that N-cadherin stops the leftward cell movements and that this termination is an essential step in the establishment of LR asymmetry.

Neuromesodermal progenitors separate the axial stem zones while producing few single- and dual-fated descendants

“…They are replaced by the long-term resident cells originating from the periphery of the node at the end of gastrulation (yellow and red in Figures 3dg and 3h-j, Supplementary Videos S8 and S9), and composing the Hensen's node at the end of the sequence. During the first 5 hours after the end of gastrulation (HH 4-6), the cells in the right-hand sector of the node transiently rotate by about 30° leftward as they move toward the centre of the PS (Figures 3h-j), confirming earlier observations (Gros et al, 2009;Mendes et al, 2014). The resident cells occupying the very tip of the PS at late stages (yellow) are derived from cells located in an anterior ∇-shaped quadrant of the organizer, previously shown as the origin of prechordal mesendoderm and notochord (Selleck and Stern, 1991).…”

H+/K+ ATPase activity is required for biomineralization in sea urchin embryos

“…Activity of this pump has also been implicated in patterning of the left-right axis in frog, zebrafish, and chicken embryos (Gros et al, 2009;Kawakami et al, 2005;Levin et al, 2002;Mendes et al, 2014), and in signaling events that mediate head regeneration and regenerative tissue remodeling in planaria (Beane et al, 2011(Beane et al, , 2013Nogi et al, 2005). Discriminating the closely related HKA and NKA genes on the basis of sequence alone is extremely challenging, and HKA genes have not been identified in any sea urchin species to date.…”

Adenohypophysis placodal precursors exhibit distinctive features within the rostral preplacodal ectoderm

“…To verify this different behaviour, we tracked the movements of individual rostral PPE cells by forcing the expression of the photoconvertible Kaede protein (Mendes et al, 2014) in the PPE of HH4/5 cultured embryos by means of electroporation ( Fig. 2; Movies 1, 2).…”

“…The pCAGGS-Kaede-NLS vector (1 mg/ml; Mendes et al, 2014) was electroporated in HH3+/4 New-cultured embryos (Voiculescu et al, 2008). Kaede photo-conversion was obtained by illuminating the region of interest with a UV (405 nm) laser beam for 10-20 interactions.…”