Hiroshi Mitani

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The mapping of Hox clusters and many duplicated genes in zebrafish indicated an extra whole-genome duplication in ray-fined fish. However, to reconstruct the preduplication chromosomes (proto-chromosomes), the comparative genomic studies of more distantly related teleosts are essential. Medaka and zebrafish are ideal for this purpose, because their lineages(More)
A variety of visual pigment repertoires present in fish species is believed due to the great variation under the water of light environment. A complete set of visual opsin genes has been isolated and characterized for absorption spectra and expression in the retina only in zebrafish. Medaka (Oryzias latipes) is a fish species phylogenetically distant from(More)
TLR22 occurs exclusively in aquatic animals and its role is unknown. Herein we show that the fugu (Takifugu rubripes) (fg)TLR3 and fgTLR22 link the IFN-inducing pathway via the fg Toll-IL-1R homology domain-containing adaptor protein 1(fgTICAM-1, or TRIF) adaptor in fish cells. fgTLR3 resides in endoplasmic reticulum and recognizes relatively short-sized(More)
Natriuretic peptides (NPs) are major cardiovascular and osmoregulatory hormones in vertebrates. Although tetrapods generally have three subtypes, atrial NP (ANP), B-type NP (BNP), and C-type NP (CNP), some teleosts lack BNP, and sharks and hagfish have only one NP. Thus, NPs have diverged during fish evolution, possibly reflecting changes in osmoregulatory(More)
Sry-related HMG-box genes are key regulators of several developmental processes. Sox9 encodes a transcription factor required for cartilage formation and testis determination in mammals. In zebrafish (Danio rerio) and stickleback (Gasterosteus aculeatus) two co-orthologs of Sox9 are present. To date, only one Sox9 had been identified in medaka (Oryzias(More)
Mouse phospholipase C, zeta 1 (PLCZ1), a strong candidate of egg-activating sperm factor, induces Ca(2+) oscillations and accumulates into formed pronucleus (PN) when expressed by cRNA injection. These activities were compared among mouse and human PLCZ1, newly cloned rat Plcz1, and medaka fish plcz1. The PLCZ1 proteins of the four species have an(More)
Gonadotropin-releasing hormone (GnRH) plays pivotal roles in the regulation of vertebrate reproduction through binding to its specific membrane receptor. Within the past few years, substantial evidence has accumulated that more than one GnRH receptor (GnRH-R) is expressed in individual vertebrate species. Two GnRH-Rs, termed GnRH-R1 and GnRH-R2, have been(More)
Although the sex-determining genes are known in mammals, Drosophila, and C. elegans, little is known in other animals. Fishes are an attractive group of organisms for studying the evolution of sex determination because they show an amazing variety of mechanisms, ranging from environmental sex determination and different forms of hermaphroditism to classical(More)
This introductory review briefly describes the history of medaka as a research organism and the previous accomplishments of the medaka field. The medaka genome project currently underway through the efforts of an international consortium, the Medaka Genome Initiative, and the future prospects for medaka research, particularly for genomic analyses, are also(More)
Major histocompatibility complex (MHC) class I molecules play a pivotal role in immune defense system, presenting the antigen peptides to cytotoxic CD8+ T lymphocytes. Most vertebrates possess multiple MHC class I loci, but the analysis of their evolutionary relationships between distantly related species has difficulties because genetic events such as gene(More)