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Kenta Nakai

Publications and source records attributed to Kenta Nakai.

At least 19 recordsLinked to original sources
PubMed2026

Spatial transcriptomics of Ciona adult brains reveals functional zonalization and insights into neural gland function.

The ascidian Ciona is a pivotal chordate model for illuminating the evolutionary origins of the vertebrate brain. Here, spatial transcriptomics of the adult Ciona neural complex, combined with image-based computational super-resolution mapping, resolved distinct tissue domains including the cerebral ganglion, neural gland, ciliated funnel, neural gland duct/dorsal strand, and body wall muscle. Within the cerebral ganglion, high-resolution mapping revealed clear molecular zonalization separating the cortex and medulla, alongside regional specialization within the cortex itself. The neural gland exhibited localized enrichment of genes associated with extracellular matrix and cell-cell interactions. These spatial features suggest that the neural gland functions as a homeostatic and signaling interface, reminiscent of primitive vertebrate meninges or choroid plexus. Overall, this spatially defined gene expression map provides a foundational framework for understanding functional regionalization in the tunicate brain and its evolutionary relationship to vertebrate nervous systems.

Ciona↗
PubMed2006

DBTGR: a database of tunicate promoters and their regulatory elements.

The high similarity of tunicates and vertebrates during their development coupled with the transparency of tunicate larvae, their well-studied cell lineages and the availability of simple and efficient transgenesis methods makes of this subphylum an ideal system for the investigation of vertebrate physiological and developmental processes. Recently, the sequencing of two different Ciona genomes has lead to the identification of numerous genes. In order to better understand the regulation of these genes, a database was created containing information on regulation of tunicate genes collected from literature. It includes for instance information regarding the minimal promoter length, the transcription factors involved and their binding sites, as well as the localization of the gene expression. Additionally, binding sites for characterized transcription factors were predicted based on published in vitro recognition sites. Comparison of the promoters of homologous genes in different species is also provided to allow identification of conserved cis elements. At the time of writing, information about 184 promoters, containing 73 identified binding sites and >2000 newly predicted binding sites is available. This database is accessible at http://dbtgr.hgc.jp.

Animals↗
PubMed2006

DBTSS: DataBase of Human Transcription Start Sites, progress report 2006.

DBTSS was first constructed in 2002 based on precise, experimentally determined 5' end clones. Several major updates and additions have been made since the last report. First, the number of human clones has drastically increased, going from 190,964 to 1,359,000. Second, information about potential alternative promoters is presented because the number of 5' end clones is now sufficient to determine several promoters for one gene. Namely, we defined putative promoter groups by clustering transcription start sites (TSSs) separated by <500 bases. A total of 8308 human genes and 4276 mouse genes were found to have putative multiple promoters. Third, DBTSS provides detailed sequence comparisons of user-specified TSSs. Finally, we have added TSS information for zebrafish, malaria and schyzon (a red algae model organism). DBTSS is accessible at http://dbtss.hgc.jp.

Animals↗
PubMed2005

Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes.

By analyzing 1,780,295 5'-end sequences of human full-length cDNAs derived from 164 kinds of oligo-cap cDNA libraries, we identified 269,774 independent positions of transcriptional start sites (TSSs) for 14,628 human RefSeq genes. These TSSs were clustered into 30,964 clusters that were separated from each other by more than 500 bp and thus are very likely to constitute mutually distinct alternative promoters. To our surprise, at least 7674 (52%) human RefSeq genes were subject to regulation by putative alternative promoters (PAPs). On average, there were 3.1 PAPs per gene, with the composition of one CpG-island-containing promoter per 2.6 CpG-less promoters. In 17% of the PAP-containing loci, tissue-specific use of the PAPs was observed. The richest tissue sources of the tissue-specific PAPs were testis and brain. It was also intriguing that the PAP-containing promoters were enriched in the genes encoding signal transduction-related proteins and were rarer in the genes encoding extracellular proteins, possibly reflecting the varied functional requirement for and the restricted expression of those categories of genes, respectively. The patterns of the first exons were highly diverse as well. On average, there were 7.7 different splicing types of first exons per locus partly produced by the PAPs, suggesting that a wide variety of transcripts can be achieved by this mechanism. Our findings suggest that use of alternate promoters and consequent alternative use of first exons should play a pivotal role in generating the complexity required for the highly elaborated molecular systems in humans.

Base Sequence↗
PubMed2005

Prediction of transcriptional terminators in Bacillus subtilis and related species.

In prokaryotes, genes belonging to the same operon are transcribed in a single mRNA molecule. Transcription starts as the RNA polymerase binds to the promoter and continues until it reaches a transcriptional terminator. Some terminators rely on the presence of the Rho protein, whereas others function independently of Rho. Such Rho-independent terminators consist of an inverted repeat followed by a stretch of thymine residues, allowing us to predict their presence directly from the DNA sequence. Unlike in Escherichia coli, the Rho protein is dispensable in Bacillus subtilis, suggesting a limited role for Rho-dependent termination in this organism and possibly in other Firmicutes. We analyzed 463 experimentally known terminating sequences in B. subtilis and found a decision rule to distinguish Rho-independent transcriptional terminators from non-terminating sequences. The decision rule allowed us to find the boundaries of operons in B. subtilis with a sensitivity and specificity of about 94%. Using the same decision rule, we found an average sensitivity of 94% for 57 bacteria belonging to the Firmicutes phylum, and a considerably lower sensitivity for other bacteria. Our analysis shows that Rho-independent termination is dominant for Firmicutes in general, and that the properties of the transcriptional terminators are conserved. Terminator prediction can be used to reliably predict the operon structure in these organisms, even in the absence of experimentally known operons. Genome-wide predictions of Rho-independent terminators for the 57 Firmicutes are available in the Supporting Information section.

Bacillus subtilis↗
PubMed2005

Large-scale analysis of human alternative protein isoforms: pattern classification and correlation with subcellular localization signals.

We investigated human alternative protein isoforms of >2600 genes based on full-length cDNA clones and SwissProt. We classified the isoforms and examined their co-occurrence for each gene. Further, we investigated potential relationships between these changes and differential subcellular localization. The two most abundant patterns were the one with different C-terminal regions and the one with an internal insertion, which together account for 43% of the total. Although changes of the N-terminal region are less common than those of the C-terminal region, extension of the C-terminal region is much less common than that of the N-terminal region, probably because of the difficulty of removing stop codons in one isoform. We also found that there are some frequently used combinations of co-occurrence in alternative isoforms. We interpret this as evidence that there is some structural relationship which produces a repertoire of isoformal patterns. Finally, many terminal changes are predicted to cause differential subcellular localization, especially in targeting either peroxisomes or mitochondria. Our study sheds new light on the enrichment of the human proteome through alternative splicing and related events. Our database of alternative protein isoforms is available through the internet.

Alternative Splicing↗
PubMed2005

Genome-wide analysis reveals strong correlation between CpG islands with nearby transcription start sites of genes and their tissue specificity.

It has been envisaged that CpG islands are often observed near the transcriptional start sites (TSS) of housekeeping genes. However, neither the precise positions of CpG islands relative to TSS of genes nor the correlation between the presence of the CpG islands and the expression specificity of these genes is well-understood. Using thousands of sequences with known TSS in human and mouse, we found that there is a clear peak in the distribution of CpG islands around TSS in the genes of these two species. Thus, we classified human (mouse) genes into 6600 (2948) CpG+ genes and 2619 (1830) CpG- ones, based on the presence of a CpG island within the -100: +100 region. We estimated the degree of each gene being a housekeeper by the number of cDNA libraries where its ESTs were detected. Then, the tendency that a gene lacking CpG islands around its TSS is expressed with a higher degree of tissue specificity turned out to be evolutionarily conserved. We also confirmed this tendency by analyzing the gene ontology annotation of classified genes. Since no such clear correlation was found in the control data (mRNAs, pre-mRNAs, and chromosome banding pattern), we concluded that the effect of a CpG island near the TSS should be more important than the global GC content of the region where the gene resides.

Animals↗
PubMed2005

Cancer gene expression database (CGED): a database for gene expression profiling with accompanying clinical information of human cancer tissues.

Gene expression profiling of cancer tissues is expected to contribute to our understanding of cancer biology as well as developments of new methods of diagnosis and therapy. Our collaborative efforts in Japan have been mainly focused on solid tumors such as breast, colorectal and hepatocellular cancers. The expression data are obtained by a high-throughput RT-PCR technique, and patients are recruited mainly from a single hospital. In the cancer gene expression database (CGED), the expression and clinical data are presented in a way useful for scientists interested in specific genes or biological functions. The data can be retrieved either by gene identifiers or by functional categories defined by Gene Ontology terms or the Swiss-Prot annotation. Expression patterns of multiple genes, selected by names or similarity search of the patterns, can be compared. Visual presentation of the data with sorting function enables users to easily recognize of relationships between gene expression and clinical parameters. Data for other cancers such as lung and thyroid cancers will be added in the near future. The URL of CGED is http://cged.hgc.jp.

Databases, Genetic↗
PubMed2004

DBTBS: database of transcriptional regulation in Bacillus subtilis and its contribution to comparative genomics.

DBTBS (http://dbtbs.hgc.jp) was originally released in 1999 as a reference database of published transcriptional regulation events in Bacillus subtilis, one of the best studied bacteria. It is essentially a compilation of transcription factors with their regulated genes as well as their recognition sequences, which were experimentally characterized and reported in the literature. Here we report its major update, which contains information on 114 transcription factors, including sigma factors, and 633 promoters of 525 genes. The number of references cited in the database has increased from 291 to 378. It also supports a function to find putative transcription factor binding sites within input sequences by using our collection of weight matrices and consensus patterns. Furthermore, though preliminarily, DBTBS now aims to contribute to comparative genomics by showing the presence or absence of potentially orthologous transcription factors and their corresponding cis-elements on the promoters of their potentially orthologously regulated genes in 50 eubacterial genomes.

Bacillus subtilis↗
PubMed2004

DBTSS, DataBase of Transcriptional Start Sites: progress report 2004.

DBTSS (http://dbtss.hgc.jp) was originally constructed based on a collection of experimentally determined TSSs of human genes. Since its first release in 2002, it has been updated several times. First, the amount of stored data has increased significantly: e.g. the number of clones that match both the RefSeq mRNA set and the genome sequence has increased from 111,382 to 190,964, now covering 1,234 genes. Second, the positions of SNPs in dbSNP were displayed on the upstream regions of contained human genes. Third, DBTSS now covers other species such as mouse and the human malaria parasite. It will become a central database containing data for many more species with oligo-capping and related methods. Lastly, the database now serves for comparative promoter analyses: in the current version, comparative views of potentially orthologous promoters from human and mouse are presented with an additional function of searching potential transcription-factor binding sites, which are either conserved or diverged between species.

Animals↗
PubMed2004

Sequence comparison of human and mouse genes reveals a homologous block structure in the promoter regions.

Comparative sequence analysis was carried out for the regions adjacent to experimentally validated transcriptional start sites (TSSs), using 3324 pairs of human and mouse genes. We aligned the upstream putative promoter sequences over the 1-kb proximal regions and found that the sequence conservation could not be further extended at, on average, 510 bp upstream positions of the TSSs. This discontinuous manner of the sequence conservation revealed a "block" structure in about one-third of the putative promoter regions. Consistently, we also observed that G+C content and CpG frequency were significantly different inside and outside the blocks. Within the blocks, the sequence identity was uniformly 65% regardless of their length. About 90% of the previously characterized transcription factor binding sites were located within those blocks. In 46% of the blocks, the 5' ends were bounded by interspersed repetitive elements, some of which may have nucleated the genomic rearrangements. The length of the blocks was shortest in the promoters of genes encoding transcription factors and of genes whose expression patterns are brain specific, which suggests that the evolutional diversifications in the transcriptional modulations should be the most marked in these populations of genes.

Animals↗
PubMed2004

Large-scale collection and characterization of promoters of human and mouse genes.

We report the generation and initial characterization of a large-scale collection of sequences of putative promoter regions (PPRs) of human and mouse genes. Based on our unique collection of 400,225 and 580,209 human and mouse full-length cDNAs, we determined exact transcriptional start sites (TSSs). Using positional information of the TSSs, we could retrieve adjacent sequences as PPRs for 8,793 and 6,875 human and mouse genes, respectively. The positions of the PPRs were 4 kb upstream to previously reported 5'-ends of cDNAs on average, demonstrating that full-length cDNA information is indispensable for this purpose. Among those PPRs supported by experimentally validated TSSs, 3,324 could be paired as mutually homologous genes between human and mouse and were used for the comprehensive comparative studies. The sequence identities in the proximal regions of the TSSs were 45% on average, and 22,794 putative transcription factor binding sites that are conserved between human and mouse were identified. The data resource created in the present work and the results of the sequences' initial characterization should lay the firm foundation for deciphering the transcriptional modulations of human genes. All the data were deposited and made available through a database for comparative studies, DBTSS.

Animals↗
PubMed2003

PSORT-B: Improving protein subcellular localization prediction for Gram-negative bacteria.

Automated prediction of bacterial protein subcellular localization is an important tool for genome annotation and drug discovery. PSORT has been one of the most widely used computational methods for such bacterial protein analysis; however, it has not been updated since it was introduced in 1991. In addition, neither PSORT nor any of the other computational methods available make predictions for all five of the localization sites characteristic of Gram-negative bacteria. Here we present PSORT-B, an updated version of PSORT for Gram-negative bacteria, which is available as a web-based application at http://www.psort.org. PSORT-B examines a given protein sequence for amino acid composition, similarity to proteins of known localization, presence of a signal peptide, transmembrane alpha-helices and motifs corresponding to specific localizations. A probabilistic method integrates these analyses, returning a list of five possible localization sites with associated probability scores. PSORT-B, designed to favor high precision (specificity) over high recall (sensitivity), attained an overall precision of 97% and recall of 75% in 5-fold cross-validation tests, using a dataset we developed of 1443 proteins of experimentally known localization. This dataset, the largest of its kind, is freely available, along with the PSORT-B source code (under GNU General Public License).

Bacterial Proteins↗
PubMed2003

Melina: motif extraction from promoter regions of potentially co-regulated genes.

UNLABELLED: 'Melina' assists users to compare the results of four public softwares for DNA motif extraction in order to both confirm the reliability of each finding and avoid missing important motifs. It is also useful to optimize the sensitivity of software with a series of different parameter settings. AVAILABILITY: Melina is available at http://www.hgc.ims.u-tokyo.ac.jp/Melina/.

Amino Acid Motifs↗
PubMed2002

Sequence-based approach for identification of cell wall proteins in Saccharomyces cerevisiae.

Open reading frames (ORFs) in the genome of Saccharomyces cerevisiae were screened for cell wall proteins and extracellular proteins, using an in silico sequence analysis combined with biochemical examination. The selection criteria used in the sequence analysis were the presence of a signal sequence for secretion and the absence of any targeting and retention signal to/in intracellular components. By using the PSORT II program, 163 ORFs/proteins were selected as potential extracellular proteins, including cell wall proteins. Of these, 51 ORFs/proteins of unknown localization and more than 120 amino acids in size were further studied on their cellular localization. A hemagglutinin (HA) epitope was inserted in the most C-terminus of each protein and the resulting HA-tagged protein was expressed under the authentic promoter in yeast cells. Out of the 51 constructs, 35 gave protein bands on Western blots. Examination of proteins in fractionated samples identified 11 extracellular proteins; six proteins that were weakly associated with the cell wall and five proteins that were relatively tightly associated with the cell wall.

Cell Wall↗
PubMed2002

DBTSS: DataBase of human Transcriptional Start Sites and full-length cDNAs.

Although the information of cDNAs is indispensable for analyzing gene function, most of the cDNA sequences stored in current databases are imperfect in the sense that they lack the precise information of 5' end termini. To overcome this difficulty, we have developed the oligo-capping method to obtain full-length cDNAs, the information of which has been partly deposited in public databases. In this study, we further constructed human cDNA libraries enriched in clones containing the cap structure to systematically explore the 5' end structure of expressed genes. Of approximately 217 402 5' end sequences obtained, 111 382 have been matched to cDNA sequences of known genes (7889 genes) and are presented in our new database, DataBase of Transcriptional Start Sites (DBTSS; http://elmo.ims.u-tokyo.ac.jp/dbtss/). Sequence comparison between our entries and those of a reference sequence database, RefSeq, revealed that 4683 (34%) of RefSeq sequences should be extended towards the 5' ends. We also mapped each sequence on the human draft genome sequence to identify its transcriptional start site, which provides us with more detailed information on distribution patterns of transcriptional start sites and adjacent regulatory regions.

5' Flanking Region↗