| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
Formation of the chordate body is accomplished by a complex set of morphogenetic movements including convergent extension of notochord cells. In the urochordate ascidian Ciona intestinalis, Brachyury (Ci-Bra) plays a key role in the formation of the notochord, and more than thirty Ci-Bra-downstream notochord genes have been identified. In the present study, we examined the effects of functional suppression of nine Ci-Bra-downstream notochord genes, which include Ci-PTP (protein tyrosine phosphatase), Ci-ACL (ATP: citratelyase), Ci-prickle, Ci-netrin, Ci-trop (tropomyosin-like), Ci-Noto3, Ci-ASAK (ATP sulfurylase/APS kinase), Ci-ERM (ezrin/redixin/meiosin) and Ci-pellino. When function of first two genes (Ci-PTP and Ci-ACL) was suppressed with specific morpholinos, the notochord cells failed convergent, while functional suppression of Ci-prickle resulted in a failure of intercalation, and therefore the cells in these three types of embryo remained in mid-dorsal region of the embryo. Functional suppression of the next four genes (Ci-netrin, Ci-trop, Ci-Noto3 and Ci-ASAK) resulted in the partial defect of intercalation, and the notochord did not consist of a single row of coin-shaped cells. In addition, when the function of the last two genes (Ci-ERM and Ci-pellino) was suppressed, the embryo showed failure of notochord cell elongation, even though convergent/extension took place normally. These results indicate that many Ci-Bra-downstream notochord genes are involved in convergent/extension of the embryo. The results also suggest that an evolutionary event leading to the formation of a chordate-specific character or notochord was the recruitment of genes required for convergent/extension of embryonic cells.
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