Combinatorial signaling by Sonic hedgehog and Wnt family members induces myogenic bHLH gene expression in the somite.

Abstract

We have demonstrated previously that a combination of signals from the neural tube and the floor platelnotochord complex synergistically induce the expression of myogenic bHLH genes and myogenic differentiation markers in unspecified somites. In this study we demonstrate that Sonic hedgehog (Shh), which is expressed in the floor platelnotochord, and a subset of Wnt family members (Wnt-1, Wnt-3, and Wnt-4), which are expressed in dorsal regions of the neural tube, mimic the muscle inducing activity of these tissues. In combination, Shh and either Wnt-1 or Wnt-3 are sufficient to induce myogenesis in somitic tissue in vitro. Therefore, we propose that myotome formation in vivo may be directed by the combinatorial activity of Shh secreted by ventral midline tissues (floor plate and notochord) and Wnt ligands secreted by the dorsal neural tube.

Cell fate specification along the anterior–posterior axis of the intermediate mesoderm

“…Chick embryonic tissue was cultured in type I collagen gels (Mü nsterberg et al, 1995) suffused with defined tissue culture medium: DMEM-F12 (Gibco), 5 r/ml human transferrin (Gibco), 100 r/ml conalbumin (Sigma), 1ϫ insulin-transferrin-selenium (Gibco), 1% Pen-Strep, and 1% L-glutamine. The cultures were incubated up to 24 hr (equivalent to the in vivo experiments) and fixed in 4% PFA.…”

Fin development in a cartilaginous fish and the origin of vertebrate limbs

“…RT-PCR was performed as previously described 27 . The primers used for PCR amplification of ScShh (172 bp) were 5 0 -GAGCTGACAGGCTGATGACAC-3 0 and 5 0 -TGGTGATGTCCACAGCTCGGC-3 0 .…”

FGF‐4 signaling is involved in mir‐206 expression in developing somites of chicken embryos

“…Somite morphogenesis is closely linked to the progressive commitment of cells to adopt a particular fate, for example skeletal muscle, and both processes are governed and coordinated by networks of developmental signaling molecules that regulate gene expression (Buckingham, 2001). We have demonstrated, using somite explant cultures and reverse transcriptase-polymerase chain reaction (RT-PCR), that Wnt and Sonic hedgehog (Shh) signaling molecules, derived from the dorsal neural tube and notochord/floor plate, respectively, promote skeletal muscle specific gene expression and, thus, the myogenic differentiation program (Mü nsterberg et al, 1995;Schmidt et al, 2000). Recent work demonstrated that myotome-derived fibroblast growth factor (FGF) signals, acting through extracellular regulated kinase-mitogen-activated protein (ERK-MAP) kinase, specify a population of progenitor cells in the ventral somite, which gives rise to ribs and tendons (Smith et al, 2005).…”