| Research Abstract |
Results obtained in the present study are as follows :
We have shown that
1. Hroth, the otx homologous gene of the ascidian Halocynthia roretzi, regulates the transcription of HrTRP, a marker for the sensory vesicle, the anterior-most part of the central nervous system (CNS) as a positive transcription factor.
2. Hroth also plays a role in differentiation of the sensory vesicle and patterning in the anterior epidermis, including formation of the palp.
3. HrZicN, a Zic homologous gene, plays a role not only as a proneural gene involved in formation of neural cells, but also as a key regulator gene for differentiation of notochord cells. Thus, the ascidian Zic has an important function in the formation of the midline structures, the neural tube and notochord.
4. HrPitx, the homologue of vertebrate Pitx1, Pitx2 and Pitx3, is expressed in the several cell lineages leading to the palp, left epidermis, neurohypophysis and ocellus, which is very reminiscent of the expression patterns of vertebrate
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's three Pitx paralogous genes, and that the left-sided expression of HrPitx in the epidermis is under control of Nodal like vertebrate's counterpart, Pitx2.
5. Hremx, the emx/ems homologue, is not expressed in the anterior CNS. This is rather an unexpected result, considering properties of Urbilateria proposition. We have suggested a scenario that acquisition of emx/ems expression in the CNS occurred independently in the deuterostome and protosome lineages.
6. Bblhx3, the amphioxus homologue of lhx3, is expressed in the anterior inner and outer layers during gastrulation, like in ascidians and unlike in vertebrates.
7. cis-regulatory regions of Hroth identified by deletion analysis in the Halocynthia roretzi embryos are capable of reproducing the expression pattern in Ciona intestinalis embryos, too.
8. some members of Hox genes (paralogous group 7, 8, 9 and 11) are absent from Ciona intestinalis genome through the whole genome sequence analysis. This was done when I was invited by Nori Satoh (Kyoto Univ) to the Annotation Jamboree of Ciona intestinalis genome held at JGI, USA, in April 2002 Less
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