title: Identification and comparative analyses of Siamois cluster genes in Xenopus laevis and tropicalis.
abstract: Two siamois-related homeobox genes siamois (sia1) and twin (sia2), have been reported in Xenopus laevis. These genes are expressed in the blastula chordin- and noggin-expressing (BCNE) center and the Nieuwkoop center, and have complete secondary axis-inducing activity when over-expressed on the ventral side of the embryo. Using whole genome sequences of X. tropicalis and X. laevis, we identified two additional siamois-related genes, which are tandemly duplicated near sia1 and sia2 to form the siamois gene cluster. Four siamois genes in X. tropicalis are transcribed at blastula to gastrula stages. In X. laevis, the siamois gene cluster is present on both homeologous chromosomes, XLA3L and XLA3S. Transcripts from seven siamois genes (three on XLA3L and four on XLA3S) in X. laevis were detected at blastula to gastrula stages. A transcribed gene, sia1p. S, encodes an inactive protein without a homeodomain. When over-expressed ventrally, all siamois-related genes tested in this study except for sia1p. S induced a complete secondary axis, indicating that X. tropicalis and X. laevis have four and six active siamois-related genes, respectively. Of note, each gene required different amounts of mRNA for full activity. These results suggest the possibility that siamois cluster genes have functional redundancy to endow robustness and quickness to organizer formation in Xenopus species.
authors: Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
authors: Yoshikazu
authors: Y
authors: Haramoto
authors: Institute for Amphibian Biology, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
authors: Tomohito
authors: T
authors: Saijyo
authors: School of Life Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan.
authors: Toshiaki
authors: T
authors: Tanaka
authors: Institute for Amphibian Biology, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
authors: Nobuaki
authors: N
authors: Furuno
authors: Institute for Amphibian Biology, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
authors: Atsushi
authors: A
authors: Suzuki
authors: Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
authors: Yuzuru
authors: Y
authors: Ito
authors: Misaki Marine Biological Station (MMBS), Graduate School of Science, The University of Tokyo, 1024 Koajiro, Misaki, Miura, Kanagawa 238-0225, Japan.
authors: Mariko
authors: M
authors: Kondo
authors: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Masanori
authors: M
authors: Taira
authors: Institute for Amphibian Biology, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan. Electronic address: shujit@hiroshima-u.ac.jp.
authors: Shuji
authors: S
authors: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D036703:Blastula / Q000378:metabolism; D019521:Body Patterning / Q000235:genetics; D002874:Chromosome Mapping; D017124:Conserved Sequence; D004171:Diploidy; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005775:Gastrula / Q000378:metabolism; D018628:Gene Dosage; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D005810:Multigene Family; D020897:Organizers, Embryonic; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D057891:Tetraploidy; D060449:Wnt Signaling Pathway; D014981:Xenopus / Q000196:embryology / Q000235:genetics*; D029867:Xenopus Proteins / Q000235:genetics*; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics
chemical_list: D018398:Homeodomain Proteins; C093133:SIA1 protein, Xenopus; D029867:Xenopus Proteins
keywords: Early development; Genome; Secondary axis; Siamois-related gene; Wnt/β--catenin; Xenopus