A highly conserved Wnt-dependent TCF4 binding site within the proximal enhancer of the anti-myogenic Msx1 gene supports expression within Pax3-expressing limb bud muscle precursor cells

Abstract

The product of the Msx1 gene is a potent inhibitor of muscle differentiation. Msx1 is expressed in muscle precursor cells of the limb bud that also express Pax3. It is thought that Msx1 may facilitate distal migration by delaying myogenesis in these cells. Despite the role played by Msx1 in inhibiting muscle differentiation, nothing is known of the mechanisms that support the expression of the Msx1 gene within limb bud muscle precursor cells. In the present study we have used a combination of comparative genomics, mouse transgenic analysis, in situ hybridisation and immunohistochemistry to identify a highly conserved and tissue-specific regulatory sub-domain within the previously characterised Msx1 gene proximal enhancer element that supports the expression of the Msx1 gene in Pax3-expressing mouse limb pre-muscle masses. Furthermore, using a combination of in situ hybridisation, in vivo ChIP assay and transgenic explant culture analysis we provide evidence that Msx1 expression in limb bud muscle precursor cells is dependent on the canonical Wnt/TCF signalling pathway that is important in muscle shape formation. The results of these studies provide evidence of a mechanistic link between the Wnt/TCF and the Msx1/Pax3/MyoD pathways within limb bud muscle precursor cells.

Direct control of Hoxd1 and Irx3 expression by Wnt/beta-catenin signaling during anteroposterior patterning of the neural axis in Xenopus

“…We identified several homeodomaincontaining transcription factors that are induced by Wnt signaling in the neurula stage embryo. Of these, Cdx1, Cdx4, Msx1, Msx2 and Otx2 have all been described before as direct Wnt target genes (Fujimura et al, 2009, Hussein et al, 2003, Lickert et al, 2000, Miller et al, 2007, Pilon et al, 2006, Pilon et al, 2007, Westenskow et al, 2009. We here identify two other homeodomain-containing genes, Hoxd1 and Irx3, as direct Wnt/ -catenin target genes.…”

“…In addition to the 5 genes that have already been identified as direct Wnt/-catenin target genes, i.e. Cdx1, Cdx4, Otx2, Msx1 and Msx2 (Fujimura et al, 2009, Hussein et al, 2003, Lickert et al, 2000, Miller et al, 2007, Pilon et al, 2006, Pilon et al, 2007, Westenskow et al, 2009, we identified the homeobox-containing genes Hoxd1 and Irx3 as potential novel direct target genes. In addition, we focused our attention on the Crabp2 gene since it encodes a protein that potentially feeds into the RA signaling pathway.…”

Embryonic and fetal limb myogenic cells are derived from developmentally distinct progenitors and have different requirements for β-catenin

“…Several studies show that Wnts promote embryonic limb myogenesis (Anakwe et al 2003;GeethaLoganathan et al 2005GeethaLoganathan et al , 2006Takata et al 2007). However, others found that Tcf/Lef signaling inhibits differentiation of muscle progenitors (Miller et al 2007). Wnts also regulate embryonic fiber type, via canonical and noncanonical signaling (Anakwe et al 2003;Takata et al 2007).…”

PAX3: A Molecule with Oncogenic or Tumor Suppressor Function Is Involved in Cancer

“…PAX3 is downregulated when muscle tissue begins to differentiate and the muscle specific transcription factors are activated [54,56]. Ectopic expression of PAX3 prevents the myogenic differentiation of myoblasts into myotubes, which might involve the cooperation of Msx1 and Notch genes [57,58].…”