| Co-Investigator(Kenkyū-buntansha) |
SASAKI Takashi Keio University, School of Medicine, Research Associate, 医学部, 助手 (70306843)
MITA Kazuei National Institute of Agrobiological Sciences, Senior Researcher, 主任研究官 (30159165)
NARUSE Kiyoshi The University of Tokyo, Graduate school of Sciences, Lecturer, 大学院・理学系研究科, 講師 (50208089)
ODA Shoji The University of Tokyo, Graduate school of Frontier Science, Lecturer, 大学院・新領域創成科学研究科, 講師 (50266714)
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| Research Abstract |
Medaka (Oryzias latipes) is emerging as an important model fish that is phylogenically distant from zebrafish but closer to pufferfish. With the recent additions of the genetic toolkits such as BAC recourses and WGS sequences, the highly dense genome markers based on polymorphic inbred strains, which is essential for genome assembly with high quality come to be available by this research. This genomic map is a powerful tool for positional cloning of mutated genes in medaka and several of them are already cloned. About non-redundant 1200 genes and expressed sequence tags (ESTs) are mapped on a single meiotic backcross panel obtained from inbred strains.
Gene duplication is thought to be important in the generation of the genetic diversity that determines the adaptability of a species to a changing environment and an additional ancient genome duplication has been proposed in ray-finned fishes based on comparative studies showing that many genes and gene clusters exist for which two copies
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are present in teleost compared to only one in other vertebrates. To compare the linkage relationships of orthologous genes among three species of vertebrates (medaka, zebrafish and human), we developed statistical method to identify the chromosomal similarity. The data suggests the number and content of the chromosomes of the last common ancestor of ray-fined fish and lobe-fined fish and that the extra whole genome duplication event in the ray-fin lineage occurred in the common ancestor of perhaps all euteleosts. For example, medaka LG2, LG21 and zebrafish LG6. LG9 share genes, which human homologues are located on human chromosome 2 and 21. And number of duplicated genes located on different medaka LG, suggests 20-30% of genes are duplicated in Medaka.
Our comparative genomic analysis of medaka and zebrafish with reference to the human gene suggests that most teleost fish genomes mainly consist of paired chromosomes each pair derived from a single common proto-chromosome. And there may have been some chromosomal fission after the scrambling of gene order in the zebrafish linage, since zebrafish LG1 appeared to lack paired LG, and two cases of two to three LG-relationships between medaka and zebrafish were observed. This suggests that Medaka and zebrafish may have considerably different sets of genes with subfunctional or neofunction because the gene degeneration process after whole genome duplication would have affected different genes in the two fish lineage. Less
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