Interchromosomal duplication of major histocompatibility complex class I regions in rainbow trout (Oncorhynchus mykiss), a species with a presumably recent tetraploid ancestry |
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Authors: | Takashi Shiina Johannes Martinus Dijkstra Sayoko Shimizu Atsushi Watanabe Kazuyo Yanagiya Ikunari Kiryu Atushi Fujiwara Chizuko Nishida-Umehara Yuuichi Kaba Ikuo Hirono Yasutoshi Yoshiura Takashi Aoki Hidetoshi Inoko Jerzy Kazimierz Kulski Mitsuru Ototake |
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Institution: | (1) Department of Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, Bohseidai, Isehara Kanagawa, 259–1193, Japan;(2) Inland Station, National Research Institute of Aquaculture, Tamaki Mie, 519-0423, Japan;(3) College of Advanced Science and Technology, Hokkaido University, Sapporo Hokkaido, 060-0810, Japan;(4) Laboratory of Genome Science, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan;(5) Centre for Bioinformatics and Biological Computing, School of Information Technology, Division of Arts, Murdoch University, Murdoch, WA, 6150, Australia |
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Abstract: | Salmonid fishes are among the few animal taxa with a probable recent tetraploid ancestor. The present study is the first to compare large (>100 kb) duplicated genomic sequence fragments in such species. Two contiguous stretches with major histocompatibility complex (MHC) class I genes were detected in a rainbow trout BAC library, mapped and sequenced. The MHC class I duplicated regions, mapped by fluorescence in situ hybridization (FISH), were shown to be located on different metaphase chromosomes, Chr 14 and 18. Gene organization in both duplications is similar to that in other fishes, in that the class I loci are tightly linked with the PSMB8, PSMB9, PSMB10 and ABCB3 genes. Whereas one region, Onmy-IA, has a classical MHC class I locus (UBA), Onmy-IB encodes only non-classical class Ib proteins. The nucleotide diversity between the Onmy-IA and Onmy-IB noncoding regions is about 14%. This suggests that the MHC class I duplication event has occurred about 60 mya close to the time of an hypothesized ancestral tetraploid event. The present article is the first convincing report on the co-existence of two closely related MHC class I core regions on two different chromosomes. The interchromosomal duplication and the homology levels are supportive of the tetraploid model.Nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank database under the accession numbers AB162342, AB162343 and from AY525774 to AY525776. |
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Keywords: | Rainbow trout MHC Duplications Class I Genomic sequence analysis |
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