Interchromosomal duplication of major histocompatibility complex class I regions in rainbow trout (Oncorhynchus mykiss), a species with a presumably recent tetraploid ancestry.
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.
Shiina
Takashi
T
Department of Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, Isehara, Kanagawa 259-1193, Japan. tshiina@is.icc.u-tokai.ac.jp
Dijkstra
Johannes Martinus
JM
Shimizu
Sayoko
S
Watanabe
Atsushi
A
Yanagiya
Kazuyo
K
Kiryu
Ikunari
I
Fujiwara
Atushi
A
Nishida-Umehara
Chizuko
C
Kaba
Yuuichi
Y
Hirono
Ikuo
I
Yoshiura
Yasutoshi
Y
Aoki
Takashi
T
Inoko
Hidetoshi
H
Kulski
Jerzy Kazimierz
JK
Ototake
Mitsuru
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002874:Chromosome Mapping; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D004247:DNA / Q000235:genetics; D005091:Exons; D020440:Gene Duplication; D005805:Genes, MHC Class I; D017404:In Situ Hybridization, Fluorescence; D007438:Introns; D008957:Models, Genetic; D008969:Molecular Sequence Data; D017686:Oncorhynchus mykiss / Q000145:classification / Q000235:genetics* / Q000276:immunology*; D010802:Phylogeny; D011123:Polyploidy; D011401:Promoter Regions, Genetic; D017386:Sequence Homology, Amino Acid; D009626:Terminology as Topic; D014158:Transcription, Genetic
D004247:DNA