title: A novel G protein alpha subunit in embryo of the ascidian, Halocynthia roretzi.
abstract: A cDNA clone encoding a novel G protein alpha subunit, HrGalpha(n) was isolated from the larvae of ascidian, Halocynthia roretzi. In contrast with overall amino acid identity (63%) with G protein alpha subunit of G(i) or G(o) subclass, HrGalpha(n) has a unique amino acid sequence, which lacks a residue for pertussis toxin substrate, but retains for cholera toxin substrate for ADP-ribosylation. The sequence characteristics and molecular phylogenetic analysis suggest that HrGalpha(n) defines a novel subclass within G(i) class of G protein alpha subunits. The zygotic expression of HrGalpha(n) was first detected at the 64-cell stage and observed in all blastomeres except for B7.4, B7.5 and B7.6 cells till the 110-cell stage. As progress of the developmental stages, the expression of HrGalpha(n) became restricted and was observed in the muscle, mesenchyme and a part of trunk lateral cells in tailbud embryos. With HrGalpha(n)-GFP fusion-gene construct it was showed that the genomic fragment containing 2674 bp upstream of the putative translation start site of HrGalpha(n) contained the regulatory sequence responsible for the expression in the muscle and mesenchyme cells, and that the regulatory sequence functioned also in Ciona intestinalis. Our results suggest a possible involvement of HrGalpha(n) in the signaling system regulates the cell fate during the embryogenesis of the ascidian.
authors.affiliation: Department of Life Science, Graduate School of Science, Himeji Institute of Technology, Kamigori, Hyogo, Japan. iwasat@mmm.muroran-it.ac.jp
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Iwasa
authors.forename: Sachiko
authors.initials: S
authors.lastname: Mishima
authors.forename: Ayako
authors.initials: A
authors.lastname: Watari
authors.forename: Mahito
authors.initials: M
authors.lastname: Ohkuma
authors.forename: Takahiro
authors.initials: T
authors.lastname: Azuma
authors.forename: Kazue
authors.initials: K
authors.lastname: Kanehara
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Tsuda
mesh_terms: D024506:5' Flanking Region / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014561:Urochordata / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D020962:Heterotrimeric GTP-Binding Proteins