Internet-Based Inquiries From Users With the Intention to Overdose With Over-the-Counter Drugs: Qualitative Analysis of Yahoo! Chiebukuro.

BACKGROUND: Public concern with regard to over-the-counter (OTC) drug abuse is growing rapidly across countries. OTC drug abuse has serious effects on the mind and body, such as poisoning symptoms, and often requires specialized treatments. In contrast, there is concern about people who potentially abuse OTC drugs whose symptoms are not serious enough to consult medical institutions or drug addiction rehabilitation centers yet are at high risk of becoming drug dependent in the future. OBJECTIVE: Consumer-generated media (CGM), which allows users to disseminate information, is being used by people who abuse (and those who are trying to abuse) OTC drugs to obtain information about OTC drug abuse. This study aims to analyze the content of CGM to explore the questions of people who potentially abuse OTC drugs. METHODS: The subject of this research was Yahoo! Chiebukuro, the largest question and answer website in Japan. A search was performed using the names of drugs commonly used in OTC drug abuse and the keywords overdose and OD, and the number of questions posted on the content of OTC drug abuse was counted. Furthermore, a thematic analysis was conducted by extracting text data on the most abused antitussive and expectorant drug, BRON. RESULTS: The number of questions about the content of overdose medications containing the keyword BRON has increased sharply as compared with other product names. Furthermore, 467 items of question data that met the eligibility criteria were obtained from 528 items of text data on BRON; 26 codes, 6 categories, and 3 themes were generated from the 578 questions contained in these items. Questions were asked about the effects they would gain from abusing OTC drugs and the information they needed to obtain the effects they sought, as well as about the effects of abuse on their bodies. Moreover, there were questions on how to stop abusing and what is needed when seeking help from a health care provider if they become dependent. It has become clear that people who abuse OTC drugs have difficulty in consulting face-to-face with others, and CGM is used as a means to obtain the necessary information anonymously. CONCLUSIONS: On CGM, people who abused or tried to abuse OTC drugs were asking questions about their abuse expectations and anxieties. In addition, when they became dependent, they sought advice to quit their abuse. CGM was used to exchange information about OTC drug abuse, and many questions on anxieties and hesitations were posted. This study suggests that it is necessary to produce and disseminate information on OTC drug abuse, considering the situation of those who abuse or are willing to abuse OTC drugs. Support from pharmacies and drugstores would also be essential to reduce opportunities for OTC drug abuse.

Social prescribing from the patient's perspective: A literature review.

Social prescribing (SP) has aroused widespread interest across countries. SP is a way of linking patients in primary care with sources of support within the community by empowering patients to coproduce solutions to improve their health and well-being. While previous research has demonstrated that SP contributes to reducing the total cost of the National Health Service, the analysis of its effects on patients is still inadequate. This literature review critically evaluated SP from the patient's perspective through the lens of medical anthropology. The review was made with respect to the three key concepts: treatment evaluation, coproduction, and empowerment. The study revealed that SP services in the UK enabled patients to feel comfort in many cases, but general practitioners, link workers, and patients should be collaborative with each other, and their interrelationships should not be hierarchical. Nevertheless, certain modifications may be needed to introduce SP in other healthcare systems.

[The Japanese legal system and the applicability of laws and regulations on private information protection and research ethics relating to medical research].

Objectives　To clarify the structure, applicability, and objectives of the current Japanese legislation for private information protection and research ethics and to examine the clauses of the related laws/regulations for academic research purposes.Methods　The research design is a descriptive study based on a systematic literature review. Using the "e-Gov" database, the laws/regulations relating to private information protection and research ethics that apply to medical research involving human subjects and human genome/gene analysis research were included in the research. The Drugs Law (Law No. 145 of 1960) and related GCP/GPSP regulations and laws/regulations on administrative organizations, management, and procedures were excluded. Furthermore, the guidelines and Q&A relating to these laws/regulations and all 47 prefectural regulations on private information protection have been selected from the websites of the related ministries, government organizations, and prefectures.Results　Our study demonstrated that the current legal system on private information protection consists of three layers and that the applicability of the laws/regulations in this area varies according to the type of research organization. Additionally, the applicability of the laws/regulations on research ethics is different depending on the research area. While the Private Information Protection Law (PIPL) for the private sector contains two objectives, PIPL for administrative organizations and PIPL for independent administrative organizations both include three objectives. For academic research purposes, PIPL for the private sector sets out a holistic exemption clause, whereas the other two PIPLs stipulate three specific exemption clauses. Furthermore, our research revealed that the clauses of the prefectural regulations demonstrated many variances.Conclusion　This study suggests that the current Japanese legal system relating to private information protection could be defined as a "mixed model," wherein the laws/regulations concerned are not necessarily consistent. The protection of medical information is solely regulated by a few specific laws with a narrow scope of application; the ethical guidelines are not directly based on any laws; and identifying applicable laws/regulations, depending on the category of research organization, is complicated, especially in the case of collaborative research involving researchers from various organizations. Therefore, in the larger framework of legislation, it is indispensable to reconsider the protection of private medical information and its effective use, including the ethics of this process because of the sensitive and useful nature of private medical information.

Identification of Sex-associated SNPs of Greater Amberjack (Seriola dumerili).

The sex determination systems of fish are highly diverse compared with those of mammals. Thus, performing investigations using nonmodel fish species helps to understand the highly diverse sex determination systems of fish. Because greater amberjack (Seriola dumerili) is one of the most important edible fish globally and knowledge of its sex determination system is economically important in the field of aquaculture, we are interested in the mechanisms of sex determination of Seriola species. In this study, we identified sex-associated SNPs of greater amberjack using SNP information of 10 males and 10 females by an association test. We determined that the sex-associated SNPs were on chromosome 12 and mainly covered with two scaffolds (about 7.1 Mbp). Genotypes of sex-associated SNPs indicated that females are the heterogametic sex (ZZ/ZW). Furthermore, we compared the genomic structure of greater amberjack with those of Japanese amberjack (Seriola quinqueradiata), California yellowtail (Seriola dorsalis), and medaka (Oryzias latipes). Whole-genome alignments and synteny analysis indicated that the sex determination system of greater amberjack is markedly different from that of medaka and implied that the sex determination system is conserved in the Seriola species.

Whole Genome Sequencing of Greater Amberjack (Seriola dumerili) for SNP Identification on Aligned Scaffolds and Genome Structural Variation Analysis Using Parallel Resequencing.

Greater amberjack (Seriola dumerili) is distributed in tropical and temperate waters worldwide and is an important aquaculture fish. We carried out de novo sequencing of the greater amberjack genome to construct a reference genome sequence to identify single nucleotide polymorphisms (SNPs) for breeding amberjack by marker-assisted or gene-assisted selection as well as to identify functional genes for biological traits. We obtained 200 times coverage and constructed a high-quality genome assembly using next generation sequencing technology. The assembled sequences were aligned onto a yellowtail (Seriola quinqueradiata) radiation hybrid (RH) physical map by sequence homology. A total of 215 of the longest amberjack sequences, with a total length of 622.8 Mbp (92% of the total length of the genome scaffolds), were lined up on the yellowtail RH map. We resequenced the whole genomes of 20 greater amberjacks and mapped the resulting sequences onto the reference genome sequence. About 186,000 nonredundant SNPs were successfully ordered on the reference genome. Further, we found differences in the genome structural variations between two greater amberjack populations using BreakDancer. We also analyzed the greater amberjack transcriptome and mapped the annotated sequences onto the reference genome sequence.

Constructing a 'Chromonome' of Yellowtail (Seriola quinqueradiata) for Comparative Analysis of Chromosomal Rearrangements.

To investigate chromosome evolution in fish species, we newly mapped 181 markers that allowed us to construct a yellowtail (Seriola quinqueradiata) radiation hybrid (RH) physical map with 1,713 DNA markers, which was far denser than a previous map, and we anchored the de novo assembled sequences onto the RH physical map. Finally, we mapped a total of 13,977 expressed sequence tags (ESTs) on a genome sequence assembly aligned with the physical map. Using the high-density physical map and anchored genome sequences, we accurately compared the yellowtail genome structure with the genome structures of five model fishes to identify characteristics of the yellowtail genome. Between yellowtail and Japanese medaka (Oryzias latipes), almost all regions of the chromosomes were conserved and some blocks comprising several markers were translocated. Using the genome information of the spotted gar (Lepisosteus oculatus) as a reference, we further documented syntenic relationships and chromosomal rearrangements that occurred during evolution in four other acanthopterygian species (Japanese medaka, zebrafish, spotted green pufferfish and three-spined stickleback). The evolutionary chromosome translocation frequency was 1.5-2-times higher in yellowtail than in medaka, pufferfish, and stickleback.

A novel C-type lectin gene is a strong candidate gene for Benedenia disease resistance in Japanese yellowtail, Seriola quinqueradiata.

Little is known about mechanisms of resistance to parasitic diseases in marine finfish. Benedenia disease is caused by infection by the monogenean parasite Benedenia seriolae. Previous quantitative trait locus (QTL) analyses have identified a major QTL associated with resistance to Benedenia disease in linkage group Squ2 of the Japanese yellowtail/amberjack Seriola quinqueradiata. To uncover the bioregulatory mechanism of Benedenia disease resistance, complete Illumina sequencing of BAC clones carrying genomic DNA for the QTL region in linkage group Squ2 was performed to reveal a novel C-type lectin in this region. Expression of the mRNA of this C-type lectin was detected in skin tissue parasitized by B. seriolae. Scanning for single nucleotide polymorphisms (SNPs) uncovered a SNP in the C-type lectin/C-type lectin-like domain that was significantly associated with B. seriolae infection levels. These results strongly suggest that the novel C-type lectin gene controls resistance to Benedenia disease in Japanese yellowtails.

Identification of Sex-Linked SNPs and Sex-Determining Regions in the Yellowtail Genome.

Unlike the conservation of sex-determining (SD) modes seen in most mammals and birds, teleost fishes exhibit a wide variety of SD systems and genes. Hence, the study of SD genes and sex chromosome turnover in fish is one of the most interesting topics in evolutionary biology. To increase resolution of the SD gene evolutionary trajectory in fish, identification of the SD gene in more fish species is necessary. In this study, we focused on the yellowtail, a species widely cultivated in Japan. It is a member of family Carangidae in which no heteromorphic sex chromosome has been observed, and no SD gene has been identified to date. By performing linkage analysis and BAC walking, we identified a genomic region and SNPs with complete linkage to yellowtail sex. Comparative genome analysis revealed the yellowtail SD region ancestral chromosome structure as medaka-fugu. Two inversions occurred in the yellowtail linage after it diverged from the yellowtail-medaka ancestor. An association study using wild yellowtails and the SNPs developed from BAC ends identified two SNPs that can reasonably distinguish the sexes. Therefore, these will be useful genetic markers for yellowtail breeding. Based on a comparative study, it was suggested that a PDZ domain containing the GIPC protein might be involved in yellowtail sex determination. The homomorphic sex chromosomes widely observed in the Carangidae suggest that this family could be a suitable marine fish model to investigate the early stages of sex chromosome evolution, for which our results provide a good starting point.

Second generation physical and linkage maps of yellowtail (Seriola quinqueradiata) and comparison of synteny with four model fish.

BACKGROUND: Physical and linkage maps are important aids for the assembly of genome sequences, comparative analyses of synteny, and to search for candidate genes by quantitative trait locus analysis. Yellowtail, Seriola quinqueradiata, is an economically important species in Japanese aquaculture, and genetic information will be useful for DNA-assisted breeding. We report the construction of a second generation radiation hybrid map, its synteny analysis, and a second generation linkage map containing SNPs (single nucleotide polymorphisms) in yellowtail. RESULTS: Approximately 1.4 million reads were obtained from transcriptome sequence analysis derived from 11 tissues of one individual. To identify SNPs, cDNA libraries were generated from a pool of 500 whole juveniles, and the gills and kidneys of 100 adults. 9,356 putative SNPs were detected in 6,025 contigs, with a minor allele frequency ≥ 25%. The linkage and radiation hybrid maps were constructed based on these contig sequences. 2,081 markers, including 601 SNPs markers, were mapped onto the linkage map, and 1,532 markers were mapped in the radiation hybrid map. CONCLUSIONS: The second generation linkage and physical maps were constructed using 6,025 contigs having SNP markers. These maps will aid the de novo assembly of sequencing reads, linkage studies and the identification of candidate genes related to important traits. The comparison of marker contigs in the radiation hybrid map indicated that yellowtail is evolutionarily closer to medaka than to green-spotted pufferfish, three-spined stickleback or zebrafish. The synteny analysis may aid studies of chromosomal evolution in yellowtail compared with model fish.

Construction of a high-coverage bacterial artificial chromosome library and comprehensive genetic linkage map of yellowtail Seriola quinqueradiata.

BACKGROUND: Japanese amberjack/yellowtail (Seriola quinqueradiata) is a commonly cultured marine fish in Japan. For cost effective fish production, a breeding program that increases commercially important traits is one of the major solutions. In selective breeding, information of genetic markers is useful and sufficient to identify individuals carrying advantageous traits but if the aim is to determine the genetic basis of the trait, large insert genomic DNA libraries are essential. In this study, toward prospective understanding of genetic basis of several economically important traits, we constructed a high-coverage bacterial artificial chromosome (BAC) library, obtained sequences from the BAC-end, and constructed comprehensive female and male linkage maps of yellowtail using Simple Sequence Repeat (SSR) markers developed from the BAC-end sequences and a yellowtail genomic library. RESULTS: The total insert length of the BAC library we constructed here was estimated to be approximately 11 Gb and hence 16-times larger than the yellowtail genome. Sequencing of the BAC-ends showed a low fraction of repetitive sequences comparable to that in Tetraodon and fugu. A total of 837 SSR markers developed here were distributed among 24 linkage groups spanning 1,026.70 and 1,057.83 cM with an average interval of 4.96 and 4.32 cM in female and male map respectively without any segregation distortion. Oxford grids suggested conserved synteny between yellowtail and stickleback. CONCLUSIONS: In addition to characteristics of yellowtail genome such as low repetitive sequences and conserved synteny with stickleback, our genomic and genetic resources constructed and revealed here will be powerful tools for the yellowtail breeding program and also for studies regarding the genetic basis of traits.

Construction of a radiation hybrid panel and the first yellowtail (Seriola quinqueradiata) radiation hybrid map using a nanofluidic dynamic array.

BACKGROUND: Yellowtail (Seriola quinqueradiata) are an economically important species in Japan. However, there are currently no methods for captive breeding and early rearing for yellowtail. Thus, the commercial cultivation of this species is reliant upon the capture of wild immature fish. Given this, there is a need to develop captive breeding techniques to reduce pressure on wild stocks and facilitate the sustainable development of yellowtail aquaculture. We constructed a whole genome radiation hybrid (RH) panel for yellowtail gene mapping and developed a framework physical map using a nanofluidic dynamic array to use SNPs (single nucleotide polymorphisms) in ESTs (expressed sequence tags) for the DNA-assisted breeding of yellowtail. RESULTS: Clonal RH cell lines were obtained after ionizing radiation; specifically, 78, 64, 129, 55, 42, and 53 clones were isolated after treatment with 3,000, 4,000, 5,000, 6,000, 8,000, or 10,000 rads, respectively. A total of 421 hybrid cell lines were obtained by fusion with mouse B78 cells. Ninety-four microsatellite markers used in the genetic linkage map were genotyped using the 421 hybrid cell lines. Based upon marker retention and genome coverage, we selected 93 hybrid cell lines to form an RH panel. Importantly, we performed the first genotyping of yellowtail markers in an RH panel using a nanofluidic dynamic array (Fluidigm, CA, USA). Then, 580 markers containing ESTs and SNPs were mapped in the first yellowtail RH map. CONCLUSIONS: We successfully developed a yellowtail RH panel to facilitate the localization of markers. Using this, a framework RH map was constructed with 580 markers. This high-density physical map will serve as a useful tool for the identification of genes related to important breeding traits using genetic structural information, such as conserved synteny. Moreover, in a comparison of 30 sequences in the RH group 1 (SQ1), yellowtail appeared to be evolutionarily closer to medaka and the green-spotted pufferfish than to zebrafish. We suggest that synteny analysis may be potentially useful as a tool to investigate chromosomal evolution by comparison with model fish.

Quantitative trait loci (QTL) associated with resistance to a monogenean parasite (Benedenia seriolae) in yellowtail (Seriola quinqueradiata) through genome wide analysis.

Benedenia infections caused by the monogenean fluke ectoparasite Benedenia seriolae seriously impact marine finfish aquaculture. Genetic variation has been inferred to play a significant role in determining the susceptibility to this parasitic disease. To evaluate the genetic basis of Benedenia disease resistance in yellowtail (Seriola quinqueradiata), a genome-wide and chromosome-wide linkage analyses were initiated using F1 yellowtail families (n = 90 per family) based on a high-density linkage map with 860 microsatellite and 142 single nucleotide polymorphism (SNP) markers. Two major quantitative trait loci (QTL) regions on linkage groups Squ2 (BDR-1) and Squ20 (BDR-2) were identified. These QTL regions explained 32.9-35.5% of the phenotypic variance. On the other hand, we investigated the relationship between QTL for susceptibility to B. seriolae and QTL for fish body size. The QTL related to growth was found on another linkage group (Squ7). As a result, this is the first genetic evidence that contributes to detailing phenotypic resistance to Benedenia disease, and the results will help resolve the mechanism of resistance to this important parasitic infection of yellowtail.

Homozygous and heterozygous GH transgenesis alters fatty acid composition and content in the liver of Amago salmon (Oncorhynchus masou ishikawae).

Growth hormone (GH) transgenic Amago (Oncorhynchus masou ishikawae), containing the sockeye GH1 gene fused with metallothionein-B promoter from the same species, were generated and the physiological condition through lipid metabolism compared among homozygous (Tg/Tg) and heterozygous GH transgenic (Tg/+) Amago and the wild type control (+/+). Previously, we have reported that the adipose tissue was generally smaller in GH transgenic fish compared to the control, and that the Δ-6 fatty acyl desaturase gene was down-regulated in the Tg/+ fish. However, fatty acid (FA) compositions have not been measured previously in these fish. In this study we compared the FAs composition and content in the liver using gas chromatography. Eleven kinds of FA were detected. The composition of saturated and monounsaturated fatty acids (SFA and MUFA) such as myristic acid (14:0), palmitoleic acid (16:1n-7), and cis-vaccenic acid (cis-18:1n-7) was significantly (P<0.05) decreased in GH transgenic Amago. On the other hand, the composition of polyunsaturated fatty acids (PUFAs) such as linoleic acid (18:2n-6), arachidonic acid (20:4n-6), and docosapentaenoic acid (22:5n-3) was significantly (P<0.05) increased. Levels of serum glucose and triacylglycerol were significantly (P<0.05) decreased in the GH transgenics compared with +/+ fish. Furthermore, 3'-tag digital gene expression profiling was performed using liver tissues from Tg/Tg and +/+ fish, and showed that Mid1 interacting protein 1 (Mid1ip1), which is an important factor to activate Acetyl-CoA carboxylase (ACC), was down-regulated in Tg/Tg fish, while genes involved in FA catabolism were up-regulated, including long-chain-fatty-acid-CoA ligase 1 (ACSL1) and acyl-coenzyme A oxidase 3 (ACOX3). These data suggest that liver tissue from GH transgenic Amago showed starvation by alteration in glucose and lipid metabolism due to GH overexpression. The decrease of serum glucose suppressed Mid1ip1, and caused a decrease of de novo FA synthesis, resulting in a decrease of SFA and MUFA. This induced expression of ACSL1 and ACOX3 to produce energy through ß-oxidation in the GH transgenic Amago.

Identification of the hybrid between Oryzias latipes and Oryzias curvinotus using nuclear genes and mitochondrial gene region.

Commercialized transgenic fish should be sterilized to prevent their genetic effects on native wild fish in the event of their accidental release to the environment. Diploid and allotriploid hybrids between Oryzias latipes and Oryzias curvinotus are sterile, which contributes to the sterilization of transgenic O. latipes or O. curvinotus strains, for example, fluorescent aquarium fish. However, it is very difficult to distinguish these hybrids from their parental species by morphological measurements. Thus, we confirmed whether our previously developed species identification method for O. latipes and O. curvinotus by restriction fragment length polymorphism (RFLP) analysis of polymerase chain reaction (PCR) products of nuclear DNA gene regions, namely, PCR-RFLP using Hinf I or Hsp92 II for the aromatase gene, Rsa I for the calmodulin gene, and Hae III for the caspase-6 gene, is useful for distinguishing the diploid and allotriploid hybrids from their parental Oryzias species. We found that the hybrids have maternal mitochondrial DNA by PCR-RFLP analysis using Mse I of the 16S rRNA gene.

Effects of growth hormone on the salmon pituitary proteome.

Growth hormone 1 (GH1), a pituitary hormone, plays a key role in the regulation of growth. Both excess GH1 treatment and overexpression of a GH1 transgene promote growth of salmon, but these animals exhibit physiological abnormalities in viability, fertility and metabolism, which might be related to pituitary function. However, the molecular dynamics induced in the pituitary by excess GH1 remain unknown. In this study, we performed iTRAQ proteome analysis of the amago salmon pituitary, with and without excess GH1 treatment, and found that the expression levels of proteins related to endocrine systems, metabolism, cell growth and proliferation were altered in the GH1-treated pituitary. Specifically, pituitary hormone prolactin (2.29 fold), and somatolactin α (0.14 fold) changed significantly. This result was confirmed by proteome and transcriptome analyses of pituitary from the GH1-transgenic (GH1-Tg) amago salmon. The dynamics of protein and gene expression in the pituitary of GH1-Tg amago salmon were similar to those of pituitary treated with excess GH1. Our findings suggest that not only excess GH1 hormone, but also the quantitative changes in other pituitary hormones, might be essential for the abnormal growth of amago salmon. These data will be useful in future attempts to increase the productivity of fish farming.

Induction of ambicoloration by exogenous cortisol during metamorphosis of spotted halibut Verasper variegatus.

Cortisol, the main glucocorticoid in fish, increases during flatfish metamorphosis and peaks before the surge of thyroxine. A large body of evidence indicates the essential role of thyroxine in flatfish metamorphosis, whereas information on cortisol is limited. We administered cortisol to spotted halibut Verasper variegatus larvae in order to examine the effect on pigmentation during metamorphosis. Administration of 10 µg cortisol per mL of water from before the onset of metamorphosis (stage E) to metamorphic climax (stage G) induced the development of adult type pigment cells on the blind side of the metamorphosed juveniles and increased the occurrence of ambicolored juveniles. When 10 µg/mL cortisol was administered during stage D, stages E-F, stage G or stage H, only the administration during stages E-F induced the development of adult type pigment cells on the blind side. In addition, the expression of the gene dopachrome tautomerase (dct), a marker of melanoblasts, was enhanced at Stage E by cortisol administration. These results clearly indicated, for the first time, the enhancement of pigmentation by exogenous high-dose cortisol. Since endogenous cortisol is secreted in response to various kinds of stress in rearing conditions, these results indicate a possible influence of stress conditions in the occurrence of ambicoloration in flatfish.

Origin of adult-type pigment cells forming the asymmetric pigment pattern, in Japanese flounder (Paralichthys olivaceus).

The flatfish-specific asymmetric pigment pattern depends on the asymmetric appearance of adult-type pigment cells after the late metamorphic stages. To understand the mechanism enabling the formation of this asymmetric pattern, we investigated the behavior of pigment cell latent precursors in postembryonic Japanese flounder, Paralichthys olivaceus, by analysis of the expression patterns of pigment lineage markers (colony stimulating factor 1 receptor, dopachrome tautomerase, kit) and the DiI (DiO) labeling test for latent precursors. We found that, throughout the larval stages, pigment cell latent precursors were predominantly localized along the dorsal and ventral margins of the flank symmetrically and migrated continuously from these regions to the lateral sides symmetrically, and after late metamorphic stages these precursors differentiated into adult-type pigment cells on the lateral side asymmetrically. We conclude that adult-type pigment cells that form the asymmetric pigment pattern are continuously derived from the dorsal and ventral margins of the flank during larval development.

Phenotypic analyses of a medaka mutant reveal the importance of bilaterally synchronized expression of isthmic fgf8 for bilaterally symmetric formation of the optic tectum.

Developing neural tubes are bilaterally symmetric in all vertebrate embryos, irrespective of the presence of gene networks that generate left-right asymmetry. To explore the mechanisms that underlie the bilaterally symmetric formation of the neural tube, we examined a medaka (Oryzias latipes) dominant mutant, Oot, the neural tube of which transiently lacks normal symmetry in the optic tectum. We found that spatial changes in isthmic fgf8 expression do not occur on one side of the mutant, resulting in a transient desynchronized expression that correlates with tectal asymmetry. The application of exogenous FGF8 on one side of a wild-type embryo mimics the Oot phenotype, indicating that the bilaterally equivalent expression of isthmic fgf8 is crucial for the bilaterally symmetric development of the tectum. These results suggest that tectal symmetry is not a "default" state, but rather is maintained actively by a bilaterally coupled and synchronized regulation of isthmic fgf8 expression.

Phenotypic analysis of a novel chordin mutant in medaka.

We have isolated and characterized a ventralized mutant in medaka (the Japanese killifish; Oryzias latipes), which turned out to have a mutation in the chordin gene. The mutant exhibits ventralization of the body axis, malformation of axial bones, over-bifurcation of yolk sac blood vessels, and laterality defects in internal organs. The mutant exhibits variability of phenotypes, depending on the culture temperature, from embryos with a slightly ventralized phenotype to those without any head and trunk structures. Taking advantages of these variable and severe phenotypes, we analyzed the role of Chordin-dependent tissues such as the notochord and Kupffer's vesicle (KV) in the establishment of left-right axis in fish. The results demonstrate that, in the absence of the notochord and KV, the medaka lateral plate mesoderm autonomously and bilaterally expresses spaw gene in a default state.

Mutant analyses reveal different functions of fgfr1 in medaka and zebrafish despite conserved ligand-receptor relationships.

Medaka (Oryzias latipes) is a small freshwater teleost that provides an excellent developmental genetic model complementary to zebrafish. Our recent mutagenesis screening using medaka identified headfish (hdf) which is characterized by the absence of trunk and tail structures with nearly normal head including the midbrain-hindbrain boundary (MHB). Positional-candidate cloning revealed that the hdf mutation causes a functionally null form of Fgfr1. The fgfr1hdf is thus the first fgf receptor mutant in fish. Although FGF signaling has been implicated in mesoderm induction, mesoderm is induced normally in the fgfr1hdf mutant, but subsequently, mutant embryos fail to maintain the mesoderm, leading to defects in mesoderm derivatives, especially in trunk and tail. Furthermore, we found that morpholino knockdown of medaka fgf8 resulted in a phenotype identical to the fgfr1hdf mutant, suggesting that like its mouse counterpart, Fgf8 is a major ligand for Fgfr1 in medaka early embryogenesis. Intriguingly, Fgf8 and Fgfr1 in zebrafish are also suggested to form a major ligand-receptor pair, but their function is much diverged, as the zebrafish fgfr1 morphant and zebrafish fgf8 mutant acerebellar (ace) only fail to develop the MHB, but develop nearly unaffected trunk and tail. These results provide evidence that teleost fish have evolved divergent functions of Fgf8-Fgfr1 while maintaining the ligand-receptor relationships. Comparative analysis using different fish is thus invaluable for shedding light on evolutionary diversification of gene function.