title: 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.
authors.affiliation: School of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD, UK.
authors.forename: Kerry Ann
authors.initials: KA
authors.lastname: Miller
authors.forename: John
authors.initials: J
authors.lastname: Barrow
authors.forename: J Martin
authors.initials: JM
authors.lastname: Collinson
authors.forename: Scott
authors.initials: S
authors.lastname: Davidson
authors.forename: Marissa
authors.initials: M
authors.lastname: Lear
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hill
authors.forename: Alasdair
authors.initials: A
authors.lastname: Mackenzie
mesh_terms: D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D001665:Binding Sites; D019295:Computational Biology; D004622:Embryo, Mammalian / Q000033:anatomy & histology / Q000502:physiology; D004742:Enhancer Elements, Genetic; D006801:Humans; D017403:In Situ Hybridization; D018878:Limb Buds / Q000166:cytology / Q000502:physiology; D051957:MSX1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D032342:Muscle Cells / Q000166:cytology / Q000502:physiology*; D024510:Muscle Development / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism*; D046509:Tissue Culture Techniques; D000073940:Transcription Factor 4; D051153:Wnt Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D051957:MSX1 Transcription Factor; C484084:Msx1 protein, mouse; D009419:Nerve Tissue Proteins; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D051820:TCF Transcription Factors; C090743:Tcf4 protein, mouse; D000073940:Transcription Factor 4; D051153:Wnt Proteins; C068686:Pax3 protein, mouse