Roles of Wnt pathway genes wls, wnt9a, wnt5b, frzb and gpc4 in regulating convergent-extension during palate morphogenesis

Abstract

The Wnt signaling pathway is crucial for tissue morphogenesis, participating in cellular behavior changes, notably during the process of convergent-extension. Interactions between Wnt-secreting and receiving cells during convergent-extension remain elusive. We investigated the role and genetic interactions of Wnt ligands and their trafficking factors Wls, Gpc4 and Frzb in the context of palate morphogenesis in zebrafish. We describe that the chaperon Wls and its ligands Wnt9a and Wnt5b are expressed in the ectoderm, whereas juxtaposed chondrocytes express Frzb and Gpc4. Using wls, gpc4, frzb, wnt9a and wnt5b mutants, we genetically dissected the Wnt signals operating between secreting ectoderm and receiving chondrocytes. Our analysis delineates that non-canonical Wnt signaling is required for cell intercalation, and that wnt5b and wnt9a are required for palate extension in the anteroposterior and transverse axes, respectively.

Distinct requirements of wls , wnt9a , wnt5b and gpc4 in regulating chondrocyte maturation and timing of endochondral ossification

“…Previous studies have showed that wls, wnt9a, wnt5b and gpc4 are expressed in ventral cartilage elements at the early time points of 55 h post-fertilization (hpf) and 72 hpf (Curtin et al, 2011; Rochard et al, 2016; Sisson et al, 2015). Sisson et al showed that gpc4 is expressed in the pharyngeal endoderm, neural crest and mesoderm while wnt5b is restricted to the neural crest and mesoderm (Sisson et al, 2015).…”

“…Indeed, mesenchymal expression of wls is necessary for the expansion and differentiation of chondrocytes to enable growth of Meckel’s cartilage (Rochard et al, 2016). The data underscores the spatiotemporal regulation of Wnt signaling in ventral cartilage development.…”

“…However, the non-canonical pathway has been less studied. It has been shown that both the planar cell polarity (PCP) and Ca 2+ have been shown to induce cytoskeleton reorganization, chondrocyte stacking and axial patterning (Fanto and McNeill, 2004; Le Pabic et al, 2014; Rochard et al, 2016; Sisson et al, 2015). Here we showed that the Wnt non-canonical genes; wls , wnt9a , wnt5b and gpc4 each have distinct requirements in chondrogenesis and osteogenesis during craniofacial ventral cartilage development.…”

“…Heat-shock studies inhibiting Wnt through the overexpression of dkk1, a Wnt antagonist and dntcf3, a dominant negative form of the Tcf3 transcription factor, showed ventral patterning defects in the mandibular arch (Alexander et al, 2014). Recent studies using Wls to manipulate Wnt signaling, implicated its role in skeletal development by regulating osteogenesis and chondrogenesis (Maruyama et al, 2013; Rochard et al, 2016; Zhong et al, 2012). In zebrafish, a previous study suggested that wls modulates fgf3 expression to direct cell proliferation (Wu et al, 2015).…”

“…In zebrafish, a previous study suggested that wls modulates fgf3 expression to direct cell proliferation (Wu et al, 2015). We recently highlighted the importance of wls in medialateral and dorsal-ventral patterning during palate morphogenesis (Rochard et al, 2016). We found that wls affected ventral cartilage elements similar to the ethmoid plate where Meckel’s cartilage appeared shorter and chondrocytes were smaller and cuboidal.…”