| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2000: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1999: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
Major histocompatibility complex (MHC) is important molecules in immunodefense system in vertebrates. In mammalian studies, MHC genes are regarded hypervariable by positive selection. However, evolutionary studies of MHC are not. frequently carried out in teleosts. In this study, we undertook to establish analysis system of MHC genes of a cyprinid, genus Tribolodon and to deduce evolutionary features of Tribolodon based on MHC genes.
Using T.hakonensis that were caught in the Mogami River, Yamagata, we tried to detect MHC class I genes from DNA.Using primers designed from class I genes of a carp and a zebrafish, we succeeded amplification and cloning of MHC class I genes of T.hakonensis. The aligned sequences with those of a carp and a zebrafish were identified as class I α3. However, some sequences of other individuals of T.hakonensis could not be identified. Such sequences are probably those of pseudogenes that are not expressed.Thus, it was difficult to detect class I genes from DNA.We further tried to detect MHC class II genes expressed. Using cDNA synthesized from mRNA, class II genes of T.hakonensis were amplified and cloned. The detected sequences of T.hakonensis were identified as class IIB genes. A phylogenetic tree of amino acid sequences translated was constructed according to neighbor joining (NJ) method. The NJ tree suggests that class IIB of T.hakonensis are encoded at four loci and that alleles exsist at each locus. In the tree, some of T.hakonensis are included in same clusters of a carp and a zebrafish, and others form independent own clusters. It suggests that MHC class IIB genes have been duplicated some times before such cyprinids were speciated. Thus, hypervariable MHC genes are expected as available markers for evolutionary studies also in teleosts.
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