Reiterated Wnt signaling during zebrafish neural crest development

Abstract

While Wnt/β-catenin signaling is known to be involved in the development of neural crest cells in zebrafish, it is unclear which Wnts are involved, and when they are required. To address these issues we employed a zebrafish line that was transgenic for an inducible inhibitor of Wnt/β-catenin signaling, and inhibited endogenous Wnt/β-catenin signaling at discrete times in development. Using this approach, we defined a critical period for Wnt signaling in the initial induction of neural crest,which is distinct from the later period of development when pigment cells are specified from neural crest. Blocking Wnt signaling during this early period interfered with neural crest formation without blocking development of dorsal spinal neurons. Transplantation experiments suggest that neural crest precursors must directly transduce a Wnt signal. With regard to identifying which endogenous Wnt is responsible for this initial critical period, we established that wnt8 is expressed in the appropriate time and place to participate in this process. Supporting a role for Wnt8, blocking its function with antisense morpholino oligonucleotides eliminates initial expression of neural crest markers. Taken together, these results demonstrate that Wnt signals are critical for the initial induction of zebrafish neural crest and suggest that this signaling pathway plays reiterated roles in its development.

Midkine‐b regulates cell specification at the neural plate border in zebrafish

“…In zebrafish, gene knockdown studies demonstrated that wnt8 is required for initial ncc induction (Lewis et al, 2004). We found that activation of the Wnt pathway by incubating embryos in LiCl dramatically increased mdkb expression in neural tissues.…”

“…It has been shown that reiterative Wnt signaling is crucial for posterior neural development and neural crest induction (Lewis et al, 2004). To test whether mdkb expression is modulated by Wnt activity, embryos were treated with LiCl to inhibit GSK3 activity and ectopically activate the Wnt pathway (Klein and Melton, 1996).…”

“…There, pax3 precedes expression of established ncc markers such as foxd3, which overlaps with pax3 3 hr later. Thus, pax3 is an indicative marker for early ncc induction (Lewis et al, 2004). We determined pax3 expression at 8.5 hpf (80% epiboly) in mdkb MO and mdkb RNAinjected embryos.…”

“…In addition to BMP signals, also Wnts have been implicated in ncc induction in many species (LaBonne, 2002;Yanfeng et al, 2003). Investigations in zebrafish show that in particular wnt8 is essential for ncc formation (Lewis et al, 2004). A third pathway thought to regulate ncc formation is activated by FGF, which is also essential for posteriorization the neural plate (LaBonne and Bronner-Fraser, 1998;Villanueva et al, 2002).…”

Controlled levels of canonical Wnt signaling are required for neural crest migration

“…Canonical Wnt signaling has been associated with development of craniofacial structures and NC derivatives including melanocytes and sensory neural cells (Dorsky et al, 1998;Brault et al, 2001;Hari et al, 2002;Lee et al, 2004;Lewis et al, 2004;Hari et al, 2012). In zebrafish, overexpression of ß-catenin in premigratory NC cells has been shown to promote pigment cell formation at the expense of neurons and glia, while inhibition of Wnt signaling using a truncated form of Tcf3 or a dominant-negative Wnt1 caused an opposite effect promoting neuronal fate at the expense of pigment cells (Dorsky et al, 1998).…”