| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2002: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
1.β-Catenin in the early lancelet embryo
Cytoplasmic β-Catenin was first localized to animal pole in fertilized eggs, and then distributed asymmetrically during cleaving until 32-cell stage. The furst nuclear localization occurred in all the blastomeres at the 64-cell stage. Although concentrated β-Catenin was found on the dorsal side at the early gastrula stage, expression of goosecoid and lhx3 appeared simultaneously. Embryos heated with LiCl showed showed symmetrical nuclear accumulation of β-Catenin around animal pole. However, these embryos developed correct dorso-ventral and left-right polarity.
2.Left-right asymmetry in the early lancelet embryo
Monozygotic conjoined twins arisen spontaneously and embryos with dorsal axis defects induced by LiCl showed normal left-sided expression of pitx. Conjoined twins induced by exposing fertilized eggs to an electric pulse expressed pitx on the left side of the left individual and on the right of the partner. These observations suggest early e
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stablishment of the left-right asymmetry in the lancelet embryo. When blastomeres were separated at the 2-cell stage, each developed into normal but small-sized embryo. In these embryos, pitx and nodal were expressed normally on the left side with a small number of exception. However, about a half of the embryos showed strong expression of both genes and the other half weak expression. The exception was bilateral expression. The results suggest that left-right determination starts as early as 2-cell stage in the lancelet embryo.
3.Expression of soxC gene in anterior half of prospective neural plate
A gene of the HMG family has been isolated and analyzed its relation with other members in tree patterns based on amino acid sequences within the HMG domain and whole sequences. The gene was located within the group C cluster and called soxC. It was first expressed in the anterior half of prospective neural plate at the mid-gastrula stage. The region that expressed soxC seems to transform into cerebral vesicle later. In the anterior expression region, pan-neural marker gene, neurogenein, is expressed soon, and posteriorly soxC-expressed zones of nenral plate differentiate cells expressing early neuronal marker genes.
4.T-box genes in the early lancelet embryo
Form a cDNA library constructed from early gastrulae, five T-box genes have been cloned. They are Tbrain/eomesodermin (Tbr/eomes), bachyury2, tbx2/3, tbx15/18/22, and newly identified tbx2/3/4/5. Among the 103 clones isolsted, Thr/eomes occupied 95%. Expression of tbx2/3/4/5 appeared at blastopore margin at the initial gastrula stage and was observed posterior end of archenteron, around neurenteric canal, and epidermis overlying the region of neurenteric canal in neurulae and early larvae. The epidermal cells expressing the gene became columner shape and formed tail fin that is sole fin developed in lancelets. Less
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