| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2001: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2000: ¥2,100,000 (Direct Cost: ¥2,100,000)
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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 symmetry in morphology through early pluteus stage. The symmetry is lost at late pluteus stage when an adult rudiment from the left coelomic pouch, and a left-right polarity arises in the larvae. The formation of adult rudiment on the left side larval body results in torsion between the body axis along mouth and anus of the larvae and adults. Distribution of small mic** derivatives between left-right coelomic pouches were investigated to study the origin of establishment of left-right asymmetry urchin larvae. Sea urchin eggs divide equally in first three cleavages to form eight blastomeres of equal size. Vegetal blas** devide unequally at fourth cleavage to form four micomeres in vegetal pole. The micromeres divide unequally again at cleavage to form four small micromeres in the vegetal pole. The small micromeres are located on the tip of invaginating arc** and incorporated into
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a pair of coelomic pouches formed left and right sides of the archenteron tip. According to the distribution of the small micromere derivatives into the coelomic pouches, the sea urchin species were classified into two groups. In the first group which is refered to as "5-3 type", the small micromere derivatives distributed into the left ** 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 distribution of the small micromere derivatives into the coelomic pouches in the hybrid embryos between the species of "5-3 "8-0 type" was examined. The results indicated that the distribution of the small micromere derivatives into the coelomic p** 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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