Masako Abe

Molecular genotyping of N-acetylation polymorphism to predict phenotype

SummaryN-acetylation polymorphism is one of the representative pharmacogenetic traits that underlie interindividual and interethnic differences in response to xenobiotics. To develop a practical genotyping method to predict acetylator phenotype, we studied the conditions for accurate phenotyping, and identified the phenotype in 51 Japanese. Then we performed Southern blot analysis of genomic DNA from these subjects using 32P-labeled cDNA for polymorphic N-acetyltransferase in the liver, and found that four N-acetyltransferase alleles generated six genotypes. The present genotyping method predicted the rapid, intermediate, and slow acetylators correctly in 48 of 51 overall subjects (96%) and in all of 4 slow acetylators.

Molecular genotyping for N-acetylation polymorphism in Japanese patients with colorectal cancer.

Background. N‐acetylation polymorphism has been documented as a representative pharmacogenetic trait, and also has been implicated ecogenetically in an individuals susceptibility to cancer. However, there still remains controversy concerning the association between colorectal cancer and N‐acetylation polymorphism.

A genotype of the polymorphic DNA repair gene MGMT is associated with de novo glioblastoma

Abstract Glioblastoma is one of the most malignant tumors in humans. This tumor is thought to develop as a result of the accumulation of genetic abnormalities, mainly focused on the loss of heterozygosity on chromosome 10. O6-methylguanine-DNA methyltransferase (MGMT), which is one of the most important DNA repair proteins, has also been reported that enzymatic activity, as well as the methylation status of the promoter region of the MGMT gene, contributes to the therapeutic response of alkylating agents. We previously found three allelic variants in the MGMT gene and assayed the characteristics of these polymorphic proteins. We designed a case-control study to investigate the role of MGMT genotypic risk factors for primary brain tumors. We compared the distributions of MGMT genotypes in primary brain tumors and normal controls. The frequencies of MGMT genotypes in examined primary brain tumors were not different from normal subjects. However, the combined heterozygote of V1 and a wild allele (V1/W) was frequently detected in de novo glioblastoma group with significant difference. Interestingly, among glial tumors, the V1/W genotype was dominantly detected in the patients with de novo glioblastoma. This study suggests that the V1/W genotype of the MGMT gene may contribute to the de novo occurrence of glioblastoma.

An improved method for genotyping of N -acetyltransferase polymorphism by polymerase chain reaction

SummaryPolymorphic N-acetyltransferase in human liver catalyzes N-acetylation of various arylamine-containing drugs and environmental chemicals. To accelerate the pharmacogenetic and ecogenetic studies of N-acetyltransferase polymorphism, we have developed a rapid and simple method for genotyping using a polymerase chain reaction based restriction fragment length polymorphism. This method distinguishes four kinds of allele of the N-acetyltransferase gene using a single polymerase chain reaction starting with a set of primers, followed by successive Asp718, BamHI and TaqI digestions, and then running the samples on a single electrophoresis lane. This method allows us to determine ten different genotypes easily and reliably.

A convenient method for genotyping of humanO 6-methylguanine-DNA methyltransferase polymorphism

SummaryO6-methylguanine-DNA methyltransferase (MGMT) is one of the DNA repair enzymes in mammals. We previously screened the variant alleles for the MGMT gene in the general population, and found three variants (V1, V2, V3), two of which caused amino acid substitutions (Leu84Phe for V1, and Trp65Cys for V2). In order to accelerate the ecogenetic and pharmacogenetic studies on MGMT polymorphism, we therefore developed a new PCR-based RFLP method for genotyping. The present method has some advantages over the initial PCR-single strand conformation polymorphism (SSCP) method, particularly regarding its simplicity, rapidity and specificity.

Generalized Resistance to Thyroid Hormone--Identification of a Novel c-erbAβ Thyroid Hormone Receptor Variant(Leu450) in a Japanese Family and Analysis of Its Secondary Structure by the Chou and Fasman Method

SummaryGeneralized resistance to thyroid hormone (GRTH) is characterized by elevated circulating levels of thyroid hormone in the presence of a eumetabolic state and failure to respond to triiodothyronine. Various point mutations in the c-erbAβ thyroid hormone receptor gene are known to be responsible for different phenotypes of GRTH. We herein report a new c-erbAβ variant in a Japanese family. The variant consisting of a cytosine to adenine base substitution at nucleotide position 1650 altered phenylalanine to leucine in codon 450 in the T3-binding domain of c-erbAβ. This base substitution was found in one allele of the 2 affected members of the family. The in vitro translation products of this mutant c-erbAβ gene demonstrated a significantly reduced T3-binding affinity. The secondary structure of this mutant thyroid hormone receptor predicted by the Chou and Fasman method included a new turn in the α helix structure in the T3-binding domain. We also discuss the secondary structures of the previously reported mutant receptors.