Wnt signalling regulates myogenic differentiation in the developing avian wing

Abstract

The limb musculature arises by delamination of premyogenic cells from the lateral dermomyotome. Initially the cells express Pax3 but, upon entering the limb bud, they switch on the expression of MyoD and Myf5 and undergo terminal differentiation into slow or fast fibres, which have distinct contractile properties that determine how a muscle will function. In the chick, the premyogenic cells express the Wnt antagonist Sfrp2, which is downregulated as the cells differentiate, suggesting that Wnts might regulate myogenic differentiation. Here, we have investigated the role of Wnt signalling during myogenic differentiation in the developing chick wing bud by gain-and loss-of-function studies in vitro and in vivo. We show that Wnt signalling changes the number of fast and/or slow fibres. For example, in vivo, Wnt11 decreases and increases the number of slow and fast fibres, respectively, whereas overexpression of Wnt5a or a dominant-negative Wnt11 protein have the opposite effect. The latter shows that endogenous Wnt11 signalling determines the number of fast and slow myocytes. The distinct effects of Wnt5a and Wnt11 are consistent with their different expression patterns, which correlate with the ultimate distribution of slow and fast fibres in the wing. Overexpression of activated calmodulin kinase II mimics the effect of Wnt5a, suggesting that it uses this pathway. Finally, we show that overexpression of the Wnt antagonist Sfrp2 and ∆Lef1 reduces the number of myocytes. In Sfrp2-infected limbs, the number of Pax3 expressing cells was increased, suggesting that Sfrp2 blocks myogenic differentiation. Therefore, Wnt signalling modulates both the number of terminally differentiated myogenic cells and the intricate slow/fast patterning of the limb musculature.

Wnt signaling promotes AChR aggregation at the neuromuscular synapse in collaboration with agrin

“…As various Wnts are expressed in muscle tissue (22,25,26) and inhibition of endogenous Wnt-like activity in vivo reduces post-synaptic differentiation at the NMJ (Fig. 2D), we tested whether Wnts secreted by muscle cells might contribute to agrinmediated AChR clustering.…”

Tbx1 regulation of myogenic differentiation in the limb and cranial mesoderm

“…Embryos were obtained from time-mated females, and they were genotyped by analysis of genomic DNA from tail snips. Embryos were fixed in 4% paraformaldehyde and were either analyzed by digoxigenin (DIG) in situ hybridization for gene expression, histological staining, or immunolabeling to determine MyHC or Tbx1 expression as in Anakwe et al (2003) and Zhang et al (2006), respectively.…”

Mechanical stretching induces osteoprotegerin in differentiating C2C12 precursor cells through noncanonical Wnt Pathways

“…Noncanonical Wnt signaling involves many distinct signaling cascades and effectors, including protein kinase C, (24) Dvl, (25,26) Rho, (27)(28)(29) c-jun N-terminal kinase, (30) and calcium/ calmodulin-dependent kinase II (CaMKII). (13,(31)(32)(33) Nemo-like kinase (NLK) and the nuclear factor of activated T cells (NF-AT) are well characterized effectors of Ca 2þ -dependent noncanonical Wnt signaling. (34)(35)(36) NLK phosphorylates TCF/LEF1 and inhibits its binding to b-catenin, thus antagonizing canonical Wnt signaling.…”