title: The structural organization of ascidian Halocynthia roretzi troponin I genes.
abstract: The organization of troponin I (TnI) genes from the ascidian Halocynthia roretzi have been determined. Halocynthia possesses roughly two types of TnI isoforms. One type is a single-copied adult TnI (adTnI) gene, which contains eight exons and seven introns. adTnI expresses two isoforms, the shorter body wall muscle TnI and the longer cardiac TnI, through alternative splicing. The mRNAs of these TnI isoforms may undergo trans-splicing of the 5'-leader sequences, like the TnI mRNA of another ascidian species, Ciona intestinalis. The other type comprises multi-copied larval TnI (laTnI) genes. Halocynthia has at least three laTnIs (alpha, beta, and gamma), which are composed of five exons and four introns, and two of them (alpha and gamma) are clustered in tandem. All laTnIs have B- and M-regions within their 5'-upstream regions, which have been discovered to be the regulatory elements of Halocynthia larval actin genes. The expression of Halocynthia laTnIs and larval actins may be regulated in the same manner. It is known that Ciona does not possess a larva-specific TnI isoform. The phylogenetic tree of ascidian TnIs suggests that laTnIs might have only been generated within the Pleurogona lineage after Enterogona/Pleurogona divergence, and this scenario well agrees with the absence of laTnIs in Ciona.
authors.affiliation: Laboratory of Biochemistry, Faculty of Science, Kochi University, Kochi, 780-8520, Japan. julie@cc.kochi-u.ac.jp
authors.forename: Hajime Julie
authors.initials: HJ
authors.lastname: Yuasa
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kawamura
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Takagi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons; D005796:Genes; D007814:Larva; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D020040:Trans-Splicing; D019210:Troponin I / Q000096:biosynthesis / Q000235:genetics*; D014561:Urochordata / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D019210:Troponin I