title: Unique features of Myf-5 in turtles: nucleotide deletion, alternative splicing, and unusual expression pattern.
abstract: Turtles characteristically possess a bony shell and show an extensive reduction of the trunk muscles. To gain insight into the evolution of this animal group, we focused on the underlying mechanism of the turtle-specific developmental pattern associated with the somitic mesoderm, which differentiates into both skeleton and muscle. We isolated Myf-5, a member of the myogenic-transcription-factor-encoding gene family expressed in the myotome, from the Chinese soft-shelled turtle Pelodiscus sinensis. We detected a deletion of 12 sequential nucleotides in P. sinensis Myf-5 (PsMyf-5), which appears to be shared by the turtle group. The expression pattern of PsMyf-5 in P. sinensis embryos differed from those of its orthologs in other amniotes, especially in the hypaxial region of the flank. We also identified two isoforms of the PsMyf-5 protein, a normal form similar to those of other vertebrates, and a short form produced by a translational frameshift. The short PsMyf-5 showed weaker myogenic activity in cultured cells than that of the normal protein, although the tissue distribution of the two isoforms overlapped perfectly. We propose that the unusual features of PsMyf-5 may be related to the unique developmental patterns of this animal group, and constitute one of the molecular bases for their evolutionary origin.
authors.affiliation: Laboratory for Evolutionary Morphology, Center for Developmental Biology (CDB), RIKEN, Kobe 650-0047, Japan. yk-ohya@cdb.riken.jp
authors.forename: Yoshie Kawashima
authors.initials: YK
authors.lastname: Ohya
authors.forename: Ryo
authors.initials: R
authors.lastname: Usuda
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Kuraku
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nagashima
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kuratani
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D002642:Chick Embryo; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000378:metabolism; D018965:Frameshifting, Ribosomal; D008969:Molecular Sequence Data; D051787:Myogenic Regulatory Factor 5 / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D020033:Protein Isoforms / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D017384:Sequence Deletion; D014426:Turtles / Q000196:embryology / Q000235:genetics* / Q000378:metabolism
chemical_list: D051787:Myogenic Regulatory Factor 5; D020033:Protein Isoforms