1998 Fiscal Year Final Research Report Summary
ONTOGENETIC STUDIES ON THE ORIGIN OF ECHINODERM BODY PLAN
| Project/Area Number |
09839009
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
自然史科学
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| Research Institution | The UUNIVERSITY OF TOKYO |
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Principal Investigator |
AMEMIYA Shonan UNIVERSITY OF TOKYO, GRADUATE SCHOOL OF SCIENCE, PROFESSOR, 大学院・理学系研究科, 教授 (30011670)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Shoji MITSUBISHI KASEI INSTITUTED OF LIFE SCIENCES, LABORATORY OF BIOIMAGES, CHIEF RESEARCHER, 生命画像情報研究室, 主任研究員
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| Project Period (FY) |
1997 – 1998
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| Keywords | Sea urchin / Echinoderm / Body plan / Ontogeny / Left-right asymmety / Small micromere / Crinoid / Torsion |
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| Research Abstract |
1) Studies on torsion and left-right asymmetry in sea urchin larvae. In sea urchins, embryos and larvae are bilateral symmetry in morphology through early pluteus stage. The symmetry is lost at late pluteus stage when an adult rudiment develops from the left coelomic pouch, and a left-right polarity arises in the larvae. The formation of adult rudiment on the left side of the larval body results in torsion between the body axis along mouth and anus of the larvae and adults. Distribution of small micromere-derivatives between left-right coelomic pouches were investigated to study the origin of establishment of left-right asymmetry in sea urchin larvae. Sea urchin eggs divide equally in first three cleavages to form eight blastomeres of equal size. Vegetal blastomeres devide unequally at fourth cleavage to form four micomeres in vegetal pole. The micromeres divide unequally again at the next cleavage to form four small micromeres in the vegetal pole. The small micromeres are located on t
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he tip of invaginating archenteron and incorporated into a pair of coelomic pouches formed left and right sides of the archenteron tip. According to the mode of distribution of the small micromere derivatives into the coelomic pouches, the sea urchin species were classified into two different groups. In the first group which is refered to as "5-3type", the small micromere derivatives distributed into the left and right coelomic pouches in the ratio about 5 : 3. In the second group refered to as "8-0 type" they did in the ratio 8 : 0. The mode of distribution of the small micromere derivatives into the coelomic pouches in the hybrid embryos between the species of "5-3 type" and "8-0 type" was examined. The results indicated that the distribution of the small micromere derivatives into the coelomic pouches is under the control of nuclear activity after fertilization.
2) A homeobox gene esolated from a stalked crinoid. Stalked crinoids are the most primitive group in Phylum Echinodermata. Phylogenetic analysis of the stalked crinoids has not yet been performed moleculary. We tried to clone homeobox genes in a stalked crinoid, Metacrinus rotundus, in order to investigate the phylogenetic situation of the stalked crinoid among and within the Phylum. A homeobox gene was cloned from a genomic library of the species by using a homeodomain with highly conserved protein motif of 60 amino acids in homeobox gene as a prove. The comparative analysis of the homeodomain showed that the crinoid homeobox gene had the highest homology with two genes, Nkx-5.2 of mice and spHmx of sea urchins, belonging to H6 subfamily. However, the ratios of homology in the homeodomains between the crinoid homeobox gene and Nka-5.2 or spHmx were less than 60%, suggesting that the gene belongs to a novel homeobox family. Less
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[Publications] Kurokawa, D., Kitajima, T., Mitsunaga-Nakatsubo, K., Amemiya, S., Shimada, H. and Akasaka, K.: "HpEts, an ets-related transcription factor implicated in primary mesenchyme cell differentiation of the sea urchin embryo."Mechanisms of Development. 80. 41-52 (1999)
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「研究成果報告書概要(欧文)」より
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[Publications] Nomaguchi, T. A., Nishijima, C., Minowa, S., Hashimoto, M., Haraguchi, C., Amemiya, S., and Fujisawa, H.: "Embryonic thermosensitivity of the ascidian, Ciona savignyi."Zool. Sci.. 14. 511-515 (1997)
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「研究成果報告書概要(欧文)」より
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