Specification of an anterior neuroectoderm patterning by Frizzled8a-mediated Wnt8b signalling during late gastrulation in zebrafish

Abstract

Wnts have been shown to provide a posteriorizing signal that has to be repressed in the anterior neuroectoderm for normal anteroposterior (AP) patterning. We have previously identified a zebrafish frizzled8a (fz8a) gene expressed in the presumptive anterior neuroectoderm as well as prechordal plate at the late gastrula stage. We have investigated the role of Fz8a-mediated Wnt8b signalling in anterior brain patterning in zebrafish. We show that in zebrafish embryos: (1) Wnt signalling has at least two different stage-specific posteriorizing activities in the anterior neuroectoderm, one before mid-gastrulation and the other at late gastrulation; (2) Fz8a plays an important role in mediating anterior brain patterning; (3) Wnt8b and Fz8a can functionally interact to transmit posteriorizing signals that determine the fate of the posterior diencephalon and midbrain in late gastrula embryos; and (4) Wnt8b can suppress fz8a expression in the anterior neuroectoderm and potentially affect the level and/or range of Wnt signalling. In conclusion, we suggest that a gradient of Fz8a-mediated Wnt8b signalling may play crucial role in patterning the posterior diencephalon and midbrain regions in the late gastrula.

Specific knockdown of WNT8b expression protects against phosphate‐induced calcification in vascular smooth muscle cells by inhibiting the Wnt–β‐catenin signaling pathway

“…Our study provided evidence suggesting that WNT8b expression was upregulated, and the knockdown of WNT8b consequently suppressed calcium deposition and activity of ALP, as well as decreased the expressions of BMP2, Pit1, MSX2, and Runx2, whereas it increased the expression of α‐SMA, suggesting that increased WNT8b activated the Wnt–β‐catenin signaling pathway and thereby stimulated high phosphate‐induced T/G HA‐VSMCs calcification. WNT8b is a member of class I Wnt family signaling through β‐catenin, and Wnts could regulate cell fate and behavior in the Wnt–β‐catenin signaling pathway (Kim et al, ). WNT8b has been suggested to be a cancer‐related gene through the synergistic activation of the β‐catenin signaling, and the expression of WNT8b mRNA, specifically, was elevated in the breast cancer cell line MCF‐7 (Saitoh et al, ).…”

Fezf2 Regulates Telencephalic Precursor Differentiation from Mouse Embryonic Stem Cells

“…Fezf2 Affects Early A--P Patterning of Forebrain Through Regulating Wnt Signaling Wnts including Wnt1, Wnt3a, and Wnt8b are key regulators in the caudalization of progenitor cells to form the diencephalon and midbrain (Sasai and De Robertis 1997;Kim et al 2002;Lagutin et al 2003). Since Fezf2 is essential for regulating the A--P patterning, we examined whether the role of Fezf2 is achieved through the regulation of Wnts.…”

Nkx2.9 Contributes to Mid-Hindbrain Patterning by Regulation of mdDA Neuronal Cell-Fate and Repression of a Hindbrain-Specific Cell-Fate

“…En1 , En2 , and Wnt8b have previously been linked to the development of mdDA neurons and cytoarchitecture of the midbrain [ 17 , 19 , 25 ]. Besides their function in development of the DA system, En1 and Wnt8b have also been implicated in the establishment of the IsO and development of the serotonin system [ 19 , 26 , 27 ], whereas Pax7 , and Tph2 have both been implicated in the development of the noradrenergic and serotonin system of the hindbrain [ 28 , 29 , 30 ]. The differential regulation of genes involved in the development of mid- and hindbrain-specific neuronal systems and genes important for the establishment of the IsO, points to a possible function of Nkx2.9 in development of these brain areas, similar to the previously described function of Nkx2.2 [ 7 , 31 ].…”