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Lisianthus (Eustoma grandiflorum) is an important floricultural crop cultivated worldwide. Despite its commercial importance, few DNA markers are available for molecular genetic research. In this study, we constructed a genetic linkage map and to detect quantitative trait loci (QTLs) for important agronomic traits of lisianthus. To develop simple sequence repeat (SSR) markers, we used 454-pyrosequencing technology to obtain genomic shotgun sequences and subsequently identified 8263 putative SSRs. A total of 3990 primer pairs were designed in silico and 1189 unique primer pairs were extracted through a BLAST search. Amplification was successful for more than 1000 primer pairs, and ultimately 278 SSR markers exhibited polymorphism between the two lisianthus accessions evaluated. Based on these markers, a genetic linkage map was constructed using a breeding population derived from crosses between the two accessions, for which flowering time differed (>140 days when grown under 20°C). We detected one QTL associated with flowering time (phenotypic variance, 27%; LOD value, 3.7). The SSR marker located at this QTL may account for variation in flowering time among accessions (i.e., three accessions whose nodes of the first flower were over 30 had late-flowering alleles of this QTL).

The Rice Core Collection of Japanese Landraces (JRC) consisting of 50 accessions was developed by the genebank at the National Agriculture and Food Research Organization (NARO) in 2008. As a Japanese landrace core collection, the JRC has been used for many research projects, including screening for different phenotypes and allele mining for target genes. To understand the genetic diversity of Japanese Landraces, we performed whole-genome resequencing of these 50 accessions and obtained a total of 2,145,095 single nucleotide polymorphism (SNPs) and 317,832 insertion–deletions (indels) by mapping against the Oryza sativa ssp. japonica Nipponbare genome. A JRC phylogenetic tree based on 1,394 representative SNPs showed that JRC accessions were divided into two major groups and one small group. We used the multiple genome browser, TASUKE+, to examine the haplotypes of flowering genes and detected new mutations in these genes. Finally, we performed genome-wide association studies (GWAS) for agronomical traits using the JRC and another core collection, the World Rice Core Collection (WRC), comprising 69 accessions also provided by the NARO genebank. In leaf blade width, a strong peak close to NAL1, a key gene for the regulation of leaf width, and, in heading date, a peak near HESO1 involved in flowering regulation were observed in GWAS using the JRC. They were also detected in GWAS using the combined JRC + WRC. Thus, JRC and JRC + WRC are suitable populations for GWAS of particular traits.

Genebanks provide access to diverse materials for crop improvement. To utilize and evaluate them effectively, core collections, such as the World Rice Core Collection (WRC) in the Genebank at the National Agriculture and Food Research Organization, have been developed. Because the WRC consists of 69 accessions with a high degree of genetic diversity, it has been used for >300 projects. To allow deeper investigation of existing WRC data and to further promote research using Genebank rice accessions, we performed whole-genome resequencing of these 69 accessions, examining their sequence variation by mapping against the Oryza sativa ssp. japonica Nipponbare genome. We obtained a total of 2,805,329 single nucleotide polymorphisms (SNPs) and 357,639 insertion–deletions. Based on the principal component analysis and population structure analysis of these data, the WRC can be classified into three major groups. We applied TASUKE, a multiple genome browser to visualize the different WRC genome sequences, and classified haplotype groups of genes affecting seed characteristics and heading date. TASUKE thus provides access to WRC genotypes as a tool for reverse genetics. We examined the suitability of the compact WRC population for genome-wide association studies (GWASs). Heading date, affected by a large number of quantitative trait loci (QTLs), was not associated with known genes, but several seed-related phenotypes were associated with known genes. Thus, for QTLs of strong effect, the compact WRC performed well in GWAS. This information enables us to understand genetic diversity in 37,000 rice accessions maintained in the Genebank and to find genes associated with different phenotypes.The sequence data have been deposited in DNA Data Bank of Japan Sequence Read Archive (DRA) (Supplementary Table S1).

The genus Prevotella plays an important role in polysaccharide degradation and fermentation in the rumen. To further understand the function of the phylogenetically diverse genus Prevotella , it is necessary to explore the individual characteristics at the species level. In this study, Gram-negative anaerobic bacterial strains isolated from the rumen of Holstein cows were identified. Strain R5019T was classified within the genus Prevotella based on 16S rRNA gene sequence-based phylogenetic analysis. The values of 16S rRNA gene sequence similarity, average nucleotide identity and digital DNA–DNA hybridization between strain R5019T and its phylogenetically nearest species Prevotella multisaccharivorax PPPA20T were 89.8, 82.6, and 29.3 %, respectively. The genome size of R5019T was estimated to be ca. 4.19 Mb with a genomic G+C content of 49.5 mol%. The major cellular fatty acids and menaquinones were C15 : 0 anteiso and C17 : 0 anteiso and MK-11 and MK-12, respectively. Succinate, lactate, malate, acetate and formate were produced as the fermentation end products using glucose. Based on phylogenetic, physiological, biochemical and genomic differences between 11 strains and other phylogenetically related Prevotella species, a novel species, Prevotella lacticifex sp. nov., is proposed within the genus Prevotella . The type strain is R5019T (=JCM 34664T=DSM 112675T).

Recent revolutionary advancements in sequencing technologies have made it possible to obtain mass quantities of genome-scale sequence data in a cost-effective manner and have drastically altered molecular biological studies. To utilize these sequence data, genome-wide association studies (GWASs) have become increasingly important. Hence, there is an urgent need to develop a visualization tool that enables efficient data retrieval, integration of GWAS results with diverse information and rapid public release of such large-scale genotypic and phenotypic data. We developed a web-based genome browser TASUKE+ (https://tasuke.dna.affrc.go.jp/), which is equipped with the following functions: (i) interactive GWAS results visualization with genome resequencing data and annotation information, (ii) PCR primer design, (iii) phylogenetic tree reconstruction and (iv) data sharing via the web. GWAS results can be displayed in parallel with polymorphism data, read depths and annotation information in an interactive and scalable manner. Users can design PCR primers for polymorphic sites of interest. In addition, a molecular phylogenetic tree of any region can be reconstructed so that the overall relationship among the examined genomes can be understood intuitively at a glance. All functions are implemented through user-friendly web-based interfaces so that researchers can easily share data with collaborators in remote places without extensive bioinformatics knowledge.

Chromatin looping plays an important role in genome regulation. However, because ChIP-seq and loop-resolution Hi-C (DNA-DNA proximity ligation) are extremely challenging in mammalian early embryos, the developmental stage at which cohesin-mediated loops form remains unknown. Here, we study early development in medaka (the Japanese killifish, Oryzias latipes) at 12 time points before, during, and after gastrulation (the onset of cell differentiation) and characterize transcription, protein binding, and genome architecture. We find that gastrulation is associated with drastic changes in genome architecture, including the formation of the first loops between sites bound by the insulator protein CTCF and a large increase in the size of contact domains. In contrast, the binding of the CTCF is fixed throughout embryogenesis. Loops form long after genome-wide transcriptional activation, and long after domain formation seen in mouse embryos. These results suggest that, although loops may play a role in differentiation, they are not required for zygotic transcription. When we repeated our experiments in zebrafish, loops did not emerge until gastrulation, that is, well after zygotic genome activation. We observe that loop positions are highly conserved in synteny blocks of medaka and zebrafish, indicating that the 3D genome architecture has been maintained for >110–200 million years of evolution.

The Japanese Archipelago is widely covered with acidic soil made of volcanic ash, an environment which is detrimental to the preservation of ancient biomolecules. More than 10,000 Palaeolithic and Neolithic sites have been discovered nationwide, but few skeletal remains exist and preservation of DNA is poor. Despite these challenging circumstances, we succeeded in obtaining a complete mitogenome sequence from Palaeolithic human remains. We also obtained those of Neolithic (hunting-gathering Jomon and the farming Yayoi cultures) remains, and over 2,000 present-day Japanese. The Palaeolithic mitogenome is potentially an ancestral type of haplogroup M, suggesting it is not only connected to present-day Japanese but also present-day East Asians. There were no changes in the gene pool from the hunting-gathering (Jomon) to the farming cultures (Yayoi), and this is different from in Europe, where there was no genetic continuity between hunter-gatherers and farmers. We also found that a vast increase of population size happened and has continued since the Yayoi period, characterized with paddy rice farming. It means that the cultural transition, i.e. rice agriculture, had significant impact on the demographic history of Japanese population.

In 2018, Brucella ceti was isolated from a bottlenose dolphin from the western Pacific Ocean. Here, we report a draft genome sequence of the isolate BD1442 of sequence type 27, which is the only sequence type known to have been isolated from human clinical cases.

Background Endogenous viral elements play important roles in eukaryotic evolution by giving rise to genetic novelties. Herpesviruses are a large family of DNA viruses, most of which do not have the ability to endogenize into host genomes. Recently, we identified a novel type of endogenous herpesvirus, which we named “Teratorn”, from the medaka (Oryzias latipes) genome, in which the herpesvirus is fused with a piggyBac-like DNA transposon, forming a novel mobile element. Teratorn is a unique herpesvirus that retains its viral genes intact and has acquired the endogenized lifestyle by hijacking the transposon system. However, it is unclear how this novel element evolved in the teleost lineage and whether fusion of two mobile elements is a general phenomenon in vertebrates. Results Here we performed a comprehensive genomic survey searching for Teratorn-like viruses in publicly available genome data and found that they are widely distributed in teleosts, forming a clade within Alloherpesviridae. Importantly, at least half of the identified Teratorn-like viruses contain piggyBac-like transposase genes, suggesting the generality of the transposon-herpesvirus fusion in teleosts. Phylogenetic tree topologies between the piggyBac-like transposase gene and herpesvirus-like genes are nearly identical, supporting the idea of a long-term evolutionary relationship between them. Conclusion We propose that piggyBac-like elements and Teratorn-like viruses have co-existed for a long time, and that fusion of the two mobile genetic elements occurred frequently in teleosts. Electronic supplementary material The online version of this article (10.1186/s40851-018-0089-8) contains supplementary material, which is available to authorized users.

Mobile genetic elements (e.g., transposable elements and viruses) display significant diversity with various life cycles, but how novel elements emerge remains obscure. Here, we report a giant (180-kb long) transposon, Teratorn, originally identified in the genome of medaka, Oryzias latipes. Teratorn belongs to the piggyBac superfamily and retains the transposition activity. Remarkably, Teratorn is largely derived from a herpesvirus of the Alloherpesviridae family that could infect fish and amphibians. Genomic survey of Teratorn-like elements reveals that some of them exist as a fused form between piggyBac transposon and herpesvirus genome in teleosts, implying the generality of transposon-herpesvirus fusion. We propose that Teratorn was created by a unique fusion of DNA transposon and herpesvirus, leading to life cycle shift. Our study supports the idea that recombination is the key event in generation of novel mobile genetic elements., Teratorn is a large mobile genetic element originally identified in the small teleost fish medaka. Here, the authors show that Teratorn is derived from the fusion of a piggyBac superfamily DNA transposon and an alloherpesvirus and that it is widely found across teleost fish.

SUMMARYLegumes have evolved a unique manner of seed dispersal in that the seed pods explosively split open with helical tension generated by sclerenchyma on the endocarp. During domestication, azuki bean (Vigna angularis) and yard-long bean (Vigna unguiculata cv-gr. Sesquipedalis) have reduced or lost the sclerenchyma and lost the shattering behavior of seed pods. Here we performed fine-mapping with back-crossed populations and narrowed the candidate genomic region down to 4 kbp in azuki bean and 13 kbp in yard-long bean. Among genes located in these regions, we found MYB26 genes encoded truncated proteins in both the domesticated species. We also found in azuki bean and other legumes that MYB26 is duplicated and only the duplicated copy is expressed in seed pods. Interestingly, in Arabidopsis MYB26 is single copy and is specifically expressed in anther to initiate secondary wall thickening that is required for anther dehiscence. These facts indicated that, in legumes, MYB26 has been duplicated and acquired a new role in development of pod sclerenchyma. However, pod shattering is unfavorable phenotype for harvesting and thus has been selected against by human.

The Asian cultivated rice, Oryza sativa, is one of the most important crops feeding more than a third of global population. In spite of the studies for several decades, the origin and domestication history of rice varietal groups, japonica and indica, have not been fully unveiled. Genetic information of ancient rice remains is essential for direct and exclusive insight into the domestication history of rice. We performed ancient DNA analysis of 950- to 2,800-year-old rice remains excavated from Japan and Korea. We found the presence of both japonica- and indica-type varieties in the Yayoi period and the middle ages of Japan and the middle part of Korea Peninsula 2,000 years ago. It is popularly considered that japonica has been exclusively cultivated in northern part of East Asia including Japan and Korea. Our result disclosed unexpectedly wide diversity of rice varieties in archaic East Asia. The present results from ancient rice DNA reveal an exclusive insight for the domestication history of rice which is not provided as far as contemporary rice.

Genome architecture plays a critical role in gene regulation, but how the structures seen in mature cells emerge during embryonic development remains poorly understood. Here, we study early development in medaka (the Japanese killifish, Oryzias latipes) at 12 time points before, during, and after gastrulation which is the most dramatic event in early embryogenesis, and characterize transcription, protein binding, and genome architecture. We find that gastrulation is most associated with drastic changes in genome architecture, including the formation of the first loops between sites bound by the insulator protein CTCF and great increase in the size of contact domains. However, the position of CTCF is fixed throughout medaka embryogenesis. Interestingly, genome-wide transcription precedes the emergence of mature domains and CTCF-CTCF loops.

This chapter summarizes recent data obtained from genome sequencing, annotation projects, and studies on the genome diversity of Oryza sativa and related Oryza species. O. sativa, commonly known as Asian rice, is the first monocot species whose complete genome sequence was deciphered based on physical mapping by an international collaborative effort. This genome, along with its accurate and comprehensive annotation, has become an indispensable foundation for crop genomics and breeding. With the development of innovative sequencing technologies, genomic studies of O. sativa have dramatically increased; in particular, a large number of cultivars and wild accessions have been sequenced and compared with the reference rice genome. Since de novo genome sequencing has become cost-effective, the genome of African cultivated rice, O. glaberrima, has also been determined. Comparative genomic studies have highlighted the independent domestication processes of different rice species, but it also turned out that Asian and African rice share a common gene set that has experienced similar artificial selection. An international project aimed at constructing reference genomes and examining the genome diversity of wild Oryza species is currently underway, and the genomes of some species are publicly available. This project provides a platform for investigations such as the evolution, development, polyploidization, and improvement of crops. Studies on the genomic diversity of Oryza species, including wild species, should provide new insights to solve the problem of growing food demands in the face of rapid climatic changes.

It is considered that more than 15 depths of coverage are necessary for next-generation sequencing (NGS) data to obtain reliable complete nucleotide sequences of the mitogenome. However, it is difficult to satisfy this requirement for all nucleotide positions because of problems obtaining a uniform depth of coverage for poorly preserved materials. Thus, we propose an imputation approach that allows a complete mitogenome sequence to be deduced from low-depth-coverage NGS data. We used different types of mitogenome data files as panels for imputation: a worldwide panel comprising all the major haplogroups, a worldwide panel comprising sequences belonging to the estimated haplogroup alone, a panel comprising sequences from the population most closely related to an individual under investigation, and a panel comprising sequences belonging to the estimated haplogroup from the population most closely related to an individual under investigation. The number of missing nucleotides was drastically reduced in all the panels, but the contents obtained by imputation were quite different among the panels. The efficiency of the imputation method differed according to the panels used. The missing nucleotides were most credibly imputed using sequences of the estimated haplogroup from the population most closely related to the individual under investigation as a panel.

The aim of this report is to recognize the significance of the public support necessary for maintenance and recovery of rural areas damaged by earthquakes, comparing the case of Western Tottori Earthquake with that of Mid Niigata Earthquake. The Japanese housing reconstruction support system was not adequate enough to satisfy the demands of the people in rural area damaged by the earthquakes. There were some limits to the application of the system such as income limit, age limit and the damage’s degree limit. The local government should clearly proclaim the housing reconstruction support according to the actual situation at early time.

The purpose of this study is to clarify the evaluation of the public support for the reconstruction of the houses damaged by the 2004 Mid Niigata Earthquake. This housing reconstruction system was not adequate enough to satisfy the demands of people and local officers in rural areas damaged by the earthquakes. People want to ease regulations requirement, complicated procedures for public support and so on for rebuilding and repairing the houses.

Bunching onion (Allium fistulosum L.) is one of the most important vegetables in Japan. Although expressed sequence tag (EST)-derived markers for bulb onion (A. cepa L.) have been developed from medium-scale sequencing, comparable EST sequences in bunching onion are lacking. In this study, we obtained 54,903 bunching onion unigenes using transcriptome shotgun assembly (TSA) and two next-generation sequencing technologies, GS-FLX and HiSeq 2000. When bunching onion and bulb onion unigenes were compared, 10,688 were estimated as reciprocal best-hit relationships. In the bunching onion TSA sequences, we discovered 2,396 di- to pentanucleotide simple sequence repeat (SSR) motifs and 5,505 exon–intron boundary sites. Moreover, we detected 9,002 single nucleotide polymorphisms and 4,335 insertion–deletion (InDel) by comparing sequence reads obtained from two inbred lines, “F” and “A.” TSA-derived SSR, cleaved amplified polymorphic sequences, InDels and intron-spanning markers were used to develop a linkage map. The genetic map, designated the FA map, contained 17 linkage groups with 364 markers (190 bunching onion TSAs, 96 bunching onion genomic SSRs, 39 bulb onion ESTs and 4 other markers) and covered a distance of 1,150 cM.

New repeat sequences were found in the Drosophila ananassae genome sequence. They accounted for approximately 1.2% of the D. ananassae genome and were estimated to be more abundant in genomes of its closely related species belonging to the Drosophila bipectinata complex, whereas it was entirely absent in the Drosophila melanogaster genome. They were interspersed throughout euchromatic regions of the genome, usually as short tandem arrays of unit sequences, which were mostly 175-200 bp long with two distinct peaks at 180 and 189 bp in the length distribution. The nucleotide differences among unit sequences within the same array (locus) were much smaller than those between separate loci, suggesting within-locus concerted evolution. The phylogenetic tree of the repeat sequences from different loci showed that divergences between sequences from different chromosome arms occurred only at earlier stages of evolution, while those within the same chromosome arm occurred thereafter, resulting in the increase in copy number. We found RNA polymerase III promoter sequences (A box and B box), which play a critical role in retroposition of short interspersed elements. We also found conserved stem-loop structures, which are possibly associated with certain DNA rearrangements responsible for the increase in copy number within a chromosome arm. Such an atypical combination of characteristics (i.e., wide dispersal and tandem repetition) may have been generated by these different transposition mechanisms during the course of evolution.

Summary: Because an enormous amount of sequence data is being collected, a method to effectively display sequence variation information is urgently needed. tasuke is a web application that visualizes large-scale resequencing data generated by next-generation sequencing technologies and is suitable for rapid data release to the public on the web. The variation and read depths of multiple genomes, as well as annotations, can be shown simultaneously at various scales. We demonstrate the use of TASUKE by applying it to 50 rice and 100 human genome resequencing datasets. Availability and implementation: The tasuke program package and user manual are available from http://tasuke.dna.affrc.go.jp/. Contact: taitoh@affrc.go.jp

The heavily methylated vertebrate genomes are punctuated by stretches of poorly methylated DNA sequences that usually mark gene regulatory regions. It is known that the methylation state of these regions confers transcriptional control over their associated genes. Given its governance on the transcriptome, cellular functions and identity, genome-wide DNA methylation pattern is tightly regulated and evidently predefined. However, how is the methylation pattern determined in vivo remains enigmatic. Based on in silico and in vitro evidence, recent studies proposed that the regional hypomethylated state is primarily determined by local DNA sequence, e.g., high CpG density and presence of specific transcription factor binding sites. Nonetheless, the dependency of DNA methylation on nucleotide sequence has not been carefully validated in vertebrates in vivo. Herein, with the use of medaka (Oryzias latipes) as a model, the sequence dependency of DNA methylation was intensively tested in vivo. Our statistical modeling confirmed the strong statistical association between nucleotide sequence pattern and methylation state in the medaka genome. However, by manipulating the methylation state of a number of genomic sequences and reintegrating them into medaka embryos, we demonstrated that artificially conferred DNA methylation states were predominantly and robustly maintained in vivo, regardless of their sequences and endogenous states. This feature was also observed in the medaka transgene that had passed across generations. Thus, despite the observed statistical association, nucleotide sequence was unable to autonomously determine its own methylation state in medaka in vivo. Our results apparently argue against the notion of the governance on the DNA methylation by nucleotide sequence, but instead suggest the involvement of other epigenetic factors in defining and maintaining the DNA methylation landscape. Further investigation in other vertebrate models in vivo will be needed for the generalization of our observations made in medaka., Author summary The genomes of vertebrate animals are naturally and extensively modified by methylation. The DNA methylation is essential to normal functions of cells, hence the whole animal, since it governs gene expression. Defects in the establishment and maintenance of proper methylation pattern are commonly associated with various developmental abnormalities and diseases. How exactly is the normal pattern defined in vertebrate animals is not fully understood, but recent researches with computational analyses and cultured cells suggested that DNA sequence is a primary determinant of the methylation pattern. This study encompasses the first experiments that rigorously test this notion in whole animal (medaka fish). In statistical sense, we observed the very strong correlation between DNA sequence and methylation state. However, by introducing unmethylated and artificially methylated native genomic DNA sequences into the genome, we demonstrated that the artificially conferred methylation states were robustly maintained in the animal, independent of the sequence and native state. Our results thus demonstrate that genome-wide DNA methylation pattern is not autonomously determined by the DNA sequence, which underpins the vital role of DNA methylation pattern as a core epigenetic element.

Gene targeting (GT) is a technique used to modify endogenous genes in target genomes precisely via homologous recombination (HR). Although GT plants are produced using genetic transformation techniques, if the difference between the endogenous and the modified gene is limited to point mutations, GT crops can be considered equivalent to non-genetically modified mutant crops generated by conventional mutagenesis techniques. However, it is difficult to guarantee the non-incorporation of DNA fragments from Agrobacterium in GT plants created by Agrobacterium-mediated GT despite screening with conventional Southern blot and/or PCR techniques. Here, we report a comprehensive analysis of herbicide-tolerant rice plants generated by inducing point mutations in the rice ALS gene via Agrobacterium-mediated GT. We performed genome comparative genomic hybridization (CGH) array analysis and whole-genome sequencing to evaluate the molecular composition of GT rice plants. Thus far, no integration of Agrobacterium-derived DNA fragments has been detected in GT rice plants. However, >1,000 single nucleotide polymorphisms (SNPs) and insertion/deletion (InDels) were found in GT plants. Among these mutations, 20-100 variants might have some effect on expression levels and/or protein function. Information about additive mutations should be useful in clearing out unwanted mutations by backcrossing.

The present study showed that there were close relationships between tinnitus relief and improved word perception by means of a grammatically correct but non-sense Japanese word perception test. Fourteen out of 20 patients reported tinnitus relief and improvement in hearing. Nine out of the 14 patients were thought to be significantly improved in word perception. Improved word perception was observed in 7 out of 10 patients whose ears tested were opposite to ears treated while in 2 out of 10 patients whose ears tested were the same as ears treated. Improved word perception was observed in 5 patients at one segment, 2 patients at two segments and 2 patients at three segments. Improved word perception was observed in one patient at the first segment, 5 patients at the second segment, 5 patients at the third segment and 5 patients at the fourth segment. There were no significant differences in hearing level nor age in patients with and without relief of tinnitus.

Improved word perception in hearing-impaired patients following electrical stimulation of ears was shown by means of a grammatically correct but non-sense Japanese 4-segment sentence perception test. Improved word perception was reported in 15 out of 20 patients without tinnitus following electrical stimulation of ears. In 11 out of 15 patients, the number of incorrect words significantly decreased, showing that electrical stimulation of ears improved word perception. Improved word perception was observed in 5 out of 8 patients whose tested ears were contralateral to treated ears while in 8 out of 12 patients whose tested ears were the same as treated ears. The present study suggests that electrical stimulation of ears improves word perception in hearing-impaired patients without tinnitus.

In this study, the usefulness of three-dimensional angiographic imagings from helical scanning computed tomography (CT) enhanced by contrast media were evaluated based on results from three patients with a cervical mass, e.g. thyroid cancer and carotid body tumor. Three-dimensional CT (3D-CT) angiographic imagings in these cases clearly demonstrated secondary dislocation or distortion of the major cervical vessels caused by the tumor or metastatic lymph nodes. It was remarkable that in the highly vascularized tumor in case 3, all features of the tumor were delineated by 3D-CT angiography. Our results indicate that 3D-CT angiographic imagings are especially useful for preoperative evaluation of the relationship of the cervical mass to major cervical vessels as well as in the observation of tumors rich in vasculature.

The purpose of this study was to introduce the electroconduction system for an implantable tinnitus suppressor. This system is a modification of the extracochlear implant system, which was developed at Hokkaido University. This system consists of a stimulator and two coils. One of the coils is implanted inside the temporal bone and its size, including the current limiter, is 9 mm long, 6.4 mm wide and 6 mm thick. Another is contained in the plastic case which is used for hearing aids. The efficacy of conduction depends on the wave frequency. The most effective frequency was about 30 kHz. The maximum current required to relieve tinnitus is 100 microA when using this system. The heat emitted from the coil inside the case is so minimal at an intensity of 100 microA as to be negligible systemically. The electromagnetic coupling system works well for more than 4 months in saline.