Jun Sugimoto

Identification of the TCL6 genes within the breakpoint cluster region on chromosome 14q32 in T-cell leukemia.

A region on chromosome 14q32.1 is often involved in chromosomal translocations and inversions with one of the T-cell receptor loci in T-cell lymphoproliferative diseases. The breakpoints of the different rearrangements segregate into two clusters; a cluster due to inversion on the centromeric side and a cluster due to simple balanced translocations on the telomeric side. If the target gene activated by these different types of chromosomal rearrangements is the same, the gene must be localized between the two clusters of breakpoints in a region of around 160 kb. Within this breakpoint cluster region, we isolated two genes; namely, TCL1 and TML1/TCL1b genes. In the course of characterizing the TML1 gene, we further identified a third novel gene, which we named TCL6 (T-cell leukemia/lymphoma 6), from a region 7 kb upstream of the TML1 locus. The TCL6 gene expressed at least 11 isoforms through very complex alternative-splicing, including splicing with the TML1 gene. Those isoforms encode at least five open reading frames (ORFs) with no homology to known sequences. The localization of the proteins corresponding to these ORF was determined by fusing green fluorescence protein at the carboxyl terminal of each ORF. ORF141 and ORF72 were observed in the cytoplasmic region, while ORF105, ORF119, and ORF163 were predominantly localized in the nuclear region. Since the TCL6 gene was expressed in T-cell leukemia carrying a t(14;14)(q11;q32.1) chromosome translocation and was not expressed in normal T-cells (just like the TML1 and TCL1 genes), it is also a candidate gene potentially involved in leukemogenesis.

Human endogenous retroviruses with transcriptional potential in the brain

AbstractGenetic studies of neuropsychiatric disorders have often produced conflicting results, which might partly result from the involvement of epigenetic modifications. We intended to explore the possible implication of DNA methylation and human endogenous retroviruses (HERVs) in neuropsychiatric disorders. In the present study, we identified two HERV loci that are expected to retain the transcriptional activity in the brain. One was located on chromosome 1q21-q22 and the other on 22q12. Interestingly, these regions were overlapped with or included in those of schizophrenia-susceptible loci, SCZD9 and SCZD4, respectively. Particularly, the HERV on 22q12 was located in the opposite direction 4 kb downstream of the Synapsin III gene. These HERV loci could afford clear targets for methylation and expression analyses in postmortem brains of patients with psychiatric disorders such as schizophrenia. In addition, we confirmed our previous finding that only a few of particular HERV-K loci were activated among a number of highly homologous loci in teratocarcinoma cell lines. These activated loci included ones common to all teratocarcinoma cell lines analyzed and depending on their male or female origin.

Tissue specificity of methylation and expression of human genes coding for neuropeptides and their receptors, and of a human endogenous retrovirus K family

AbstractThe purpose of the present study was to understand the tissue specificity of DNA methylation and the relationship between methylation and expression of genes with essential roles in neurodevelopment and brain function. We chose dopamine receptor genes (DRD1 and DRD2), NCAM, and COMT as examples of genes with CpG islands around the promoter region, and serotonin receptor genes (HTR2A and HTR3A), HCRT, and DRD3 as genes without CpG islands. Methylation states were investigated in fetal brain, fetal liver, placenta, and in adult peripheral leukocytes from three individuals by Southern blot and bisulfite-modified DNA sequencing. A repetitive sequence, human endogenous retrovirus (HERV)-K was also examined. All genes examined were almost completely unmethylated in brains. The genes with CpG islands were unmethylated regardless of their expression state. In contrast, genes without CpG islands showed various methylation patterns, which did not necessarily reflect the transcriptional activity of the genes. Most HERV-K loci were methylated, but some loci showed relatively low methylation in the placenta and liver. Interestingly, we found inter-individual differences in methylation levels in HTR2A and HCRT in the placenta and in some loci of HERV-K in the placenta and liver. The sample with the lowest methylation levels in the two unique genes showed higher methylation of HERV-K loci than the other samples. These results provide detailed information about the methylation states of the genes analyzed and evidence for inter-individual variations in methylation in both unique and repetitive sequences.

Identification of nonsynonymous polymorphisms in the superantigen-coding region of IDDMK1,222 and a pilot study on the association between IDDMK1,222 and type 1 diabetes

AbstractTo investigate the possible involvement of IDDMK1,222/HERV-K18 in childhood type 1 diabetes mellitus, we identified two nonsynonymous A/G polymorphisms in the superantigen-coding region of IDDMK1,222 at the 290- and 461-nucleotide (nt) positions from the initial methionine codon and compared their frequencies in 74 Japanese patients with type 1 diabetes and in 54 nondiabetic controls. Although the G substitution was observed more frequently at either site in the patients than it was in the controls (7% vs. 4% at 290 nt, and 29% vs. 20% at 461 nt), the differences were not statistically significant. A weak significance of difference in the frequency of 461G was obtained only in an early-onset group of patients manifesting the disease at 5 years of age or less (n = 24) when compared with controls (38% vs. 20%; P = 0.03). However, in addition to the common absence of a particular allele among the expected four alleles, remarkable differences in allele frequencies were present between Japanese and European populations. This first trial investigating the association of IDDMK1,222 with type 1 diabetes presents intriguing suggestions for the role of this region in the etiology of autoimmune and infectious diseases.

Assignment of the human poly(A) polymerase (PAP) gene to chromosome 14q32.1-q32.2 and isolation of a polymorphic CA repeat sequence

AbstractWe report the chromosomal localization of the gene for human poly(A) polymerase (PAP) and the characterization of a newly isolated CA repeat near the PAP locus. By fluorescence in situ hybridization and polymerase chain reaction (PCR)-based analysis with both a human/rodent monochromosomal hybrid cell panel and a radiation hybrid mapping panel, this gene was mapped on the q32.1–q32.2 region of chromosome 14. From a genomic clone containing the human PAP locus, we have isolated a polymorphic dinucleotide (CA) sequence. High heterozygosity (0.81) makes this polymorphism a useful marker in the genetic study of disorders localized at the 14q32 region, such as autosomal recessive congenital microphthalmia (CMIC).

ISOLATION AND MAPPING OF A POLYMORPHIC CA REPEAT SEQUENCE AT THE HUMAN VRK1 LOCUS

AbstractVRK1 is a novel human putative serine/threonine kinase, and is located on chromosome 14 at band q32 where an autosomal recessive congenital microphthalmia (CMIC) is mapped. We isolated a polymorphic dinucleotide CA repeat marker from a genomic clone containing the human VRK1 gene. This polymorphism will be useful in genetic studies of disorders localized at the 14q32 region, such as CMIC.