PubMed Health⌕ Search

Biomedical subjects

C Amemiya

Publications and source records attributed to C Amemiya.

12 recordsLinked to original sources
PubMed2000

Hox cluster genomics in the horn shark, Heterodontus francisci.

Reconstructing the evolutionary history of Hox cluster origins will lead to insights into the developmental and evolutionary significance of Hox gene clusters in vertebrate phylogeny and to their role in the origins of various vertebrate body plans. We have isolated two Hox clusters from the horn shark, Heterodontus francisci. These have been sequenced and compared with one another and with other chordate Hox clusters. The results show that one of the horn shark clusters (HoxM) is orthologous to the mammalian HoxA cluster and shows a structural similarity to the amphioxus cluster, whereas the other shark cluster (HoxN) is orthologous to the mammalian HoxD cluster based on cluster organization and a comparison with noncoding and Hox gene-coding sequences. The persistence of an identifiable HoxA cluster over an 800-million-year divergence time demonstrates that the Hox gene clusters are highly integrated and structured genetic entities. The data presented herein identify many noncoding sequence motifs conserved over 800 million years that may function as genetic control motifs essential to the developmental process.

Animals↗
PubMed1998

Zebrafish hox clusters and vertebrate genome evolution.

HOX genes specify cell fate in the anterior-posterior axis of animal embryos. Invertebrate chordates have one HOX cluster, but mammals have four, suggesting that cluster duplication facilitated the evolution of vertebrate body plans. This report shows that zebrafish have seven hox clusters. Phylogenetic analysis and genetic mapping suggest a chromosome doubling event, probably by whole genome duplication, after the divergence of ray-finned and lobe-finned fishes but before the teleost radiation. Thus, teleosts, the most species-rich group of vertebrates, appear to have more copies of these developmental regulatory genes than do mammals, despite less complexity in the anterior-posterior axis.

Animals↗
PubMed1996

The location of MZF-1 at the telomere of human chromosome 19q makes it vulnerable to degeneration in aging cells.

A zinc-finger gene encoding a transcription factor that regulates hematopoiesis, MZF-1, is located at the extreme end of the q arm of human chromosome 19. Several lines of evidence indicate that MZF-1 lies less than 20 kb from the subtelomeric repeat region of 19q. Telomeres are known to degenerate as cells age; disruption of MZF-1 due to telomeric degeneration may play a role in the increased incidence of leukemia in the elderly.

Aging↗
PubMed1994

Complete genomic sequence and patterns of transcription of a member of an unusual family of closely related, chromosomally dispersed Ig gene clusters in Raja.

Ig genes in cartilaginous fish are organized in clusters. This unique form of organization suggests major differences in the regulation of the segmental rearrangement mechanism from that found in mammals and other higher vertebrates. The complete DNA sequence of an IgX-type cluster in the species Raja eglanteria is defined, and shown to consist of four rearranging segmental elements and three constant region exons. Using fluorescence in situ hybridization it is shown that Raja clusters are present at multiple sites within the genome, and that there is no apparent relationship between the chromosomally dispersed IgX clusters and a second isotype (IgM type) in this species. Comprehensive examination of sequence motifs associated with transcription regulation reveals an abundance of short sequences closely resembling those found in higher vertebrate Ig and other genes. However, the linear relationship of these motifs differs markedly from that associated with regulation of expression of the mammalian Ig gene locus. Additional studies of the transcription products of the IgX gene loci emphasize the diversity of transcription and processing of these genes. Considerable variation was noted in the processing of putative IgX transcripts, including the detection of a heretofore unrecognized form containing at least four additional Ig-like domains. These results have profound significance in terms of understanding the selective expression and the evolutionary diversification of Ig genes.

Animals↗
PubMed1993

Clustered organization of homologous KRAB zinc-finger genes with enhanced expression in human T lymphoid cells.

KRAB zinc-finger proteins (KRAB-ZFPs) constitute a large subfamily of ZFPs of the Krüppel C2H2 type. KRAB (Krüppel-associated box) is an evolutionarily conserved protein domain found N-terminally with respect to the finger repeats. We report here the characterization of a particular subgroup of highly related human KRAB-ZFPs. ZNF91 is one representative of this subgroup and contains 35 contiguous finger repeats at its C-terminus. Three mRNA isoforms with sequence identity to ZNF91 were isolated by the polymerase chain reaction. These encode proteins with a KRAB domain present, partially deleted or absent. Five genomic fragments were characterized, each encoding part of a gene: the ZNF91 gene or one of four distinct, related KRAB-ZFP genes. All exhibit a common exon/intron organization with the variant zinc finger repeats organized in a single exon and the KRAB domain encoded by two separate exons. This positioning of introns supports the hypothesis that the mRNA isoforms encoding polypeptides with variability in the KRAB domain could arise by alternative splicing. By in situ chromosomal mapping studies and by analysis of fragments from a human genomic yeast artificial chromosome library containing KRAB-ZFP genes, we show that these genes occur in clusters; in particular, a gene complex containing over 40 genes has been identified in chromosomal region 19p12-p13.1. These ZNF91-related genes probably arose late during evolution since no homologous genes are detected in the mouse and rat genomes. Although the transcription of members of this KRAB-ZFP gene subgroup is detectable in all human tissues, their expression is significantly higher in human T lymphoid cells.

Amino Acid Sequence↗
PubMed1993

Structure and genomic sequence of the myotonic dystrophy (DM kinase) gene.

The mutation causing myotonic dystrophy (DM) has recently been identified as an unstable CTG trinucleotide repeat located in the 3' untranslated region of a gene encoding for a protein with putative serine-threonine protein kinase activity. In this report we present the genomic sequences of the human and murine DM kinase gene. A comparison of these sequences with each other and with known cDNA sequences from both species, led us to predict a translation initiation codon, as well as determine the organization of the DM kinase gene. Several polymorphisms within the human DM kinase gene have been identified, and PCR assays to detect two of these are described. The complete sequence and characterization of the structure of the DM kinase gene, as well as the identification of novel polymorphisms within the gene, represent an important step in a further understanding of the genetics of myotonic dystrophy and the molecular biology of the gene.

Animals↗
PubMed1993

Automated production of high density cosmid and YAC colony filters using a robotic workstation.

We report here on a system for automated preparation of high-density colony filters of arrayed libraries using the high density replicating system (HDR) for the Beckman Biomek 1000 robotic workstation. This system, consisting of a 96-pin tool, a sterilization station and controlling software, transfers samples from microplates onto target membranes in arrays up to 36 times the density of a 96-well microplate. The transfer operation can be completely automated with the addition of the Biomek Side Loader System, which consists of a robotic arm capable of transferring plates and filters between the Biomek working tablet and a storage area. Using the complete system, we are able to plate 32 replica filters (8 x 12 cm), each containing the clones from 16 different microplates (i.e., 1536 clones per filter), in a 16-h overnight run without any operator intervention. We describe conditions used for transfer of bacterial yeast colonies and fixation of DNA to the membranes, and we illustrate hybridization results obtained with cosmid and YAC filters.

Biotechnology↗
PubMed1992

Myotonic dystrophy mutation: an unstable CTG repeat in the 3' untranslated region of the gene.

Myotonic dystrophy (DM) is the most common inherited neuromuscular disease in adults, with a global incidence of 1 in 8000 individuals. DM is an autosomal dominant, multisystemic disorder characterized primarily by myotonia and progressive muscle weakness. Genomic and complementary DNA probes that map to a 10-kilobase Eco RI genomic fragment from human chromosome 19q13.3 have been used to detect a variable length polymorphism in individuals with DM. Increases in the size of the allele in patients with DM are now shown to be due to an increased number of trinucleotide CTG repeats in the 3' untranslated region of a DM candidate gene. An increase in the severity of the disease in successive generations (genetic anticipation) is accompanied by an increase in the number of trinucleotide repeats. Nearly all cases of DM (98 percent or 253 of 258 individuals) displayed expansion of the CTG repeat region. These results suggest that DM is primarily caused by mutations that generate an amplification of a specific CTG repeat.

Base Sequence↗
PubMed1992

Cloning of the essential myotonic dystrophy region and mapping of the putative defect.

Myotonic dystrophy is a common dominant disorder (global incidence of 1:8,000) with variable onset and a protean nature of symptoms mainly involving progressive muscle wasting, myotonia and cataracts. To define the molecular defect, we have cloned the essential region of chromosome 19q13.3, including proximal and distal markers in a 700-kilobase contig formed by overlapping cosmids and yeast artificial chromosomes (YACs). The central part of the contig bridges an area of about 350 kilobases between two new flanking crossover borders. This segment has been extensively characterized through the isolation of five YAC clones and the subsequent subcloning in cosmids from which a detailed EcoRI, HindIII, MluI and NotI restriction map has been derived. Two genomic probes and two homologous complementary DNA probes were isolated using the cosmids. These probes are all situated within approximately 10 kilobases of genomic DNA and detect an unstable genomic segment in myotonic dystrophy patients. The length variation in this segment shows similarities to the instability seen at the fragile X locus. The physical map location and the genetic characteristics of the length polymorphism is compatible with a direct role in the pathogenesis of myotonic dystrophy.

Blotting, Southern↗
PubMed1992

Physical and genetic characterization of the distal segment of the myotonic dystrophy area on 19q.

The mutation involved in myotonic dystrophy (DM) has been mapped to the region between the ERCC1 DNA repair gene and the anonymous D19S51 locus on 19q13.3. Starting at locus D19S112 (probe pX75b), which served as a novel entry site for this chromosome region, we have established a cosmid contig of approximately 200 kb. In the contig, a gene expressed in the brain and a highly informative, 12-allele (TG)n variable simple sequence motif (VSSM) were identified. With this marker, designated X75b-VSSM, a highly characteristic size distribution of alleles linked with DM, which differed significantly from that on normal chromosomes, was observed. Combining our physical mapping and genetic data, we show that the X75b-VSSM marker is the closest distal to DM, thus excluding the DM mutation from the entire telomeric portion of the ERCC1-D19S51 region.

Base Sequence↗
PubMed1992

Characterization of the myotonic dystrophy region predicts multiple protein isoform-encoding mRNAs.

The mutation underlying myotonic dystrophy (DM) has been identified as an expansion of a polymorphic CTG-repeat in a gene encoding protein kinase activity. Brain and heart transcripts of the DM-kinase (DMR-B15) gene are subject to alternative RNA splicing in both human and mouse. The unstable [CTG]5-30 motif is found uniquely in humans, although the flanking nucleotides are also present in mouse. Characterization of the DM region of both species reveals another active gene (DMR-N9) in close proximity to the kinase gene. DMR-N9 transcripts, mainly expressed in brain and testis, possess a single, large open reading frame, but the function of its protein product is unknown. Clinical manifestation of DM may be caused by the expanded CTG-repeat compromising the (alternative) expression of DM-kinase or DMR-N9 proteins.

Alternative Splicing↗