title: Evolutionary origins of vertebrate appendicular muscle.
abstract: The evolution of terrestrial tetrapod species heralded a transition in locomotor strategies. While most fish species use the undulating contractions of the axial musculature to generate propulsive force, tetrapods also rely on the appendicular muscles of the limbs to generate movement. Despite the fossil record generating an understanding of the way in which the appendicular skeleton has evolved to provide the scaffold for tetrapod limb musculature, there is, by contrast, almost no information as to how this musculature arose. Here we examine fin muscle formation within two extant classes of fish. We find that in the teleost, zebrafish, fin muscles arise from migratory mesenchymal precursor cells that possess molecular and morphogenetic identity with the limb muscle precursors of tetrapod species. Chondrichthyan dogfish embryos, however, use the primitive mechanism of direct epithelial somitic extensions to derive the muscles of the fin. We conclude that the genetic mechanism controlling formation of tetrapod limb muscles evolved before the Sarcopterygian radiation.
authors.affiliation: Comparative and Developmental Genetics Section, Medical Research Council, Western General Hospital, Edinburgh, UK.
authors.forename: C
authors.initials: C
authors.lastname: Neyt
authors.forename: K
authors.initials: K
authors.lastname: Jagla
authors.forename: C
authors.initials: C
authors.lastname: Thisse
authors.forename: B
authors.initials: B
authors.lastname: Thisse
authors.forename: L
authors.initials: L
authors.lastname: Haines
authors.forename: P D
authors.initials: PD
authors.lastname: Currie
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002454:Cell Differentiation; D047108:Embryonic Development; D005121:Extremities / Q000196:embryology; D005399:Fishes; D009024:Morphogenesis; D009132:Muscles / Q000196:embryology*; D017570:MyoD Protein / Q000096:biosynthesis / Q000235:genetics; D015027:Zebrafish
chemical_list: D017570:MyoD Protein