| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1994: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1993: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
We report the structure of genomic DNA of salmonid neurohypophysial hormohe precursor molecules, the nucleotide sequence of the promoter region in the 5' upstream of the DNA and a phylogenetic tree of neurohypophysial hormone precursors in vertebrates constructed from the cDNA sequence data. Since salmonids are tetraploid, they have two (I and II) precursors for each of vasotocin (VT) and isotocin (IT). Only VT-I and IT-I precursor were used for analysis in this study.
The VT-I gene has two introns and three exsons with the 5' untranslated region on the first exon. This structure is principally the same as that of the mammalian vasopresin gene. Comparison of the 5' untranslated region with the salmon VT and mammalian vasopresin showed a different organization of regulatory elements in promoter region. The other differences between salmon and mammal were the followings : there was only one AP-2 in salmon but a lot of in mammal. There are several CAT boxes in salmon and few in mammal. An
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putative ERE exist in salmon but not in mammalian vasopresin although mammalian oxytocin gene contain an effective ERE.
The salmon IT-I gene had two introns and three exsons as the well as the mammalian oxytocin gene. Interestingly, IT gene of white sucker have been shown not to contain intron by the southern hybridization method. There may be at least two types of IT genes in the teleost group.
A phylogenetic tree of neurohypophysial hormone precursors in vertebrates were constructed with the sequence data of the amino acid translated from the nucleotide sequences of their cDNA.Two methods, neighbor joining and maximum liklihood, were used for the calculation of phylogenic distances. The present tree is different from the tree reported by Hyodo et al., 1991 in some portions. A large divergence first occurred in the common ancestral neurohypophysial hormone of vertebrates, i.e.bifurcation into the tetrapod and teleost tranks. The tetrapod trank was further divided into two groups, the toad VT group and group of remainers that includes toad mesotocin, mammalian vasopresin, and oxytocin. Not only oxytocin but also vasopresin had a common ancestral molecule with toad mesotocin.
In summary, this study revealed the precursor region of teleost neurohypophysial hormone genes have different structures from other vertebrates. Furthermore, a new evolutionary tree of neurohypophysial hormones based on the amino acid sequence and genomic DNA structures was proposed. Less
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