title: The contribution of Islet1-expressing splanchnic mesoderm cells to distinct branchiomeric muscles reveals significant heterogeneity in head muscle development.
abstract: During embryogenesis, paraxial mesoderm cells contribute skeletal muscle progenitors, whereas cardiac progenitors originate in the lateral splanchnic mesoderm (SpM). Here we focus on a subset of the SpM that contributes to the anterior or secondary heart field (AHF/SHF), and lies adjacent to the cranial paraxial mesoderm (CPM), the precursors for the head musculature. Molecular analyses in chick embryos delineated the boundaries between the CPM, undifferentiated SpM progenitors of the AHF/SHF, and differentiating cardiac cells. We then revealed the regionalization of branchial arch mesoderm: CPM cells contribute to the proximal region of the myogenic core, which gives rise to the mandibular adductor muscle. SpM cells contribute to the myogenic cells in the distal region of the branchial arch that later form the intermandibular muscle. Gene expression analyses of these branchiomeric muscles in chick uncovered a distinct molecular signature for both CPM- and SpM-derived muscles. Islet1 (Isl1) is expressed in the SpM/AHF and branchial arch in both chick and mouse embryos. Lineage studies using Isl1-Cre mice revealed the significant contribution of Isl1(+) cells to ventral/distal branchiomeric (stylohyoid, mylohyoid and digastric) and laryngeal muscles. By contrast, the Isl1 lineage contributes to mastication muscles (masseter, pterygoid and temporalis) to a lesser extent, with virtually no contribution to intrinsic and extrinsic tongue muscles or extraocular muscles. In addition, in vivo activation of the Wnt/beta-catenin pathway in chick embryos resulted in marked inhibition of Isl1, whereas inhibition of this pathway increased Isl1 expression. Our findings demonstrate, for the first time, the contribution of Isl1(+) SpM cells to a subset of branchiomeric skeletal muscles.
authors.affiliation: Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Elisha
authors.initials: E
authors.lastname: Nathan
authors.forename: Amir
authors.initials: A
authors.lastname: Monovich
authors.forename: Libbat
authors.initials: L
authors.lastname: Tirosh-Finkel
authors.forename: Zachary
authors.initials: Z
authors.lastname: Harrelson
authors.forename: Tal
authors.initials: T
authors.lastname: Rousso
authors.forename: Ariel
authors.initials: A
authors.lastname: Rinon
authors.forename: Itamar
authors.initials: I
authors.lastname: Harel
authors.forename: Sylvia M
authors.initials: SM
authors.lastname: Evans
authors.forename: Eldad
authors.initials: E
authors.lastname: Tzahor
mesh_terms: D000818:Animals; D001934:Branchial Region / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D002454:Cell Differentiation; D019070:Cell Lineage; D002642:Chick Embryo; D018507:Gene Expression Regulation, Developmental; D006257:Head; D006321:Heart / Q000196:embryology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D017404:In Situ Hybridization, Fluorescence; D008648:Mesoderm / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D009024:Morphogenesis; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014781:Viscera / Q000166:cytology* / Q000196:embryology; D051153:Wnt Proteins / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin