Search

Multiple endocrine neoplasia type 2A (MEN2A) is a dominantly inherited cancer syndrome characterized by medullary thyroid carcinoma, pheochromocytoma, and parathyroid hyperplasia. The gene responsible for MEN2A was localized by linkage analysis to chromosome 10q11.2 in 1987, and recently mutations in RET, a proto-oncogene in the candidate region, were discovered in patients with MEN. The majority of mutations found so far in MEN2A patients have been located in nucleotide sequences encoding cysteine residues in the extracellular domain of RET. To characterize MEN2A germline alterations in the Japanese population, we screened DNA from eight unrelated patients for mutations in exons 10 and 11 of the RET proto-oncogene and found mutations in all eight patients, at codons 618, 620, or 634; each of these sites encodes a cysteine residue in the extracellular domain of RET. The mutations were confirmed in other affected individuals in the respective families by digestion of polymerase chain reaction (PCR) products containing the mutated codons with restriction enzymes (Rs alpha I, CfoI, or AluI) for which cleavage sites had been generated by the specific genetic alteration. These PCR-restriction enzyme systems will be useful for genetic diagnosis in members of families carrying these mutations.

Tyrosinase-negative oculocutaneous albinism, the most severe subtype of a heterogeneous group of albinism, is an autosomal recessive trait caused by mutations in the tyrosinase gene. Prenatal diagnosis had been made previously only by evaluating fetal skin obtained by biopsy, an invasive procedure that cannot be performed earlier than 19 weeks of gestation. A pregnant mother of a 9-year-old Japanese boy with tyrosinase-negative oculocutaneous albinism wanted a prenatal diagnosis. Polymerase chain reaction amplification and allele-specific oligonucleotide hybridization revealed that the child is homozygous and the parents heterozygous for the pathologic mutation of the tyrosinase gene in exon 2 (single base insertion) but not for the one in exon 1. Prenatal diagnosis was made by analyzing the tyrosinase gene in fetal cells obtained by amniocentesis at 14 weeks of gestation, which demonstrated that the fetus was heterozygous for mutant tyrosinase gene. Pregnancy was therefore continued and a normal male infant was born. This procedure, the analysis of the fetal genomic tyrosinase DNA, is a rapid and reliable approach to the prenatal diagnosis of oculocutaneous albinism at a relatively early stage of pregnancy and is safer and less invasive than previous methods using fetal skin biopsy.

Polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) was used to identify the common apoprotein E (apo E) isoform genotypes. DNA from the target sequence on apo E was amplified by PCR from peripheral blood genomic DNA. Non-radiolabelled natural PCR products were electrophoresed on a polyacrylamide gradient gel and automatically silver-stained. Bands compatible with each of the three common apo E isoforms were obtained. This method, which does not require restriction enzymes or DNA purification, is a rapid and useful means of detecting the apo E isoform genotype.

A cell line designated SKM-1 was newly established from leukaemic cells of a 76-year-old Japanese male patient with monoblastic leukaemia following myelodysplastic syndrome (MDS). The cells were obtained from peripheral blood of the patient when he lost multiple point mutations of ras genes with acquisition of chromosomal abnormalities during disease progression in MDS. The cells grew as a single floating cell, and have been continuously growing with the morphological characteristics of immature monoblasts by serial passages during the past 42 months with a doubling time of about 48 h. By cytochemical analysis, the cloned cells were positive for butyrate esterase, but negative for the Epstein-Barr virus associated nuclear antigen. Phenotypic analysis revealed the expression of myelomonocyte specific antigens such as CD4, CD13, CD33 and HLA-DR. Cells from the primary peripheral blood and those from 50 passages of the SKM-1 cell line both possessed no activated ras genes but showed karyotype abnormalities with 46,XY, del(9)(q13;q22), der(17) t(17;?)(p13;?). The SKM-1 cells have two mutations in p53 gene and overexpress the p53 products. This cell line may contribute to a better understanding of molecular mechanisms in the progression from MDS to myelogenous leukaemia.

Four cDNA clones encoding myeloperoxidase were isolated from a cDNA library of monocytic leukemia SKM-1 cells. The sequences of two of them were identical to those of cDNA clones previously isolated from a HL-60 cell cDNA library. The sequences of the other two cDNA clones, MP-S34 and MP-S29, differed from those previously described. There was a deletion of 57 bp in the MP-S34 sequence, which was generated by partially skipping exon 9. MP-S29 had a 171 bp deletion, which was generated by completely skipping exon 10. Thus MP-S34 and MP-S29 encoded polypeptides lacking 19 and 57 amino acids, respectively. Both deletions were located on the sequence encoding the heavy subunit. These results indicate that the heterogeneity of the heavy subunit of MPO observed in leukocytes or leukemia could be in part produced by partial or complete skipping of an exon.

The development of a polymerase chain reaction (PCR) method for detection of human parvovirus B19 DNA and serological test of clinical specimens using ELISA is described. Of 43 serum (or plasma) samples, 29 were found to be positive for B19 DNA using the PCR, anti-IgM was detected in 16 specimens and anti-IgG in 25. In all specimens confirmed to contain B19-specific IgM, the presence of B19 DNA was demonstrated. Furthermore, B19 DNA was demonstrated in a patient with B19 infection for a longer period of time than was anti-IgM. In addition, we discuss the diagnosis of B19 infection using anti-IgG, in the acute stage and convalescent stage. In fetal infection, the PCR method provides sufficient detection of B19 DNA in cord blood, amniotic fluid, ascitic fluid, and fetal pericardial effusion and pleural effusion.

Several rodent studies based on molecular biology have suggested that accumulation of genetic alterations in cancer-associated genes is required to convert a normal cell into a malignant cell. Activation of oncogenes and inactivation of tumor suppressor genes appear to be involved in carcinogenesis. In renal cell carcinomas, we have recently implied that the presence of tumor suppressor genes at chromosome 3p13-14.3 and 21.3, the regions where are also commonly deleted in adenocarcinoma of the lung; at chromosome 5q21, the region where the MCC (mutated in colorectal cancer) gene and APC (adenomatous polyposis coli) gene are located; at chromosome 6q27; and at 10q 21-23. We have also indicated that genes on 3p is probably important for development of RCCs and genes on 5q, 6q, and 10q may be associated with progression of RCCs.

A newly established human monocytic cell line, SKM-1, showed strong expression of myeloperoxidase mRNA, to the same extent as in HL-60 cells. We studied the cell morphology and myeloperoxidase expression of this cell line, which was established from a patient with myelodysplastic syndrome who had an abnormal chromosome on the upstream region of 17p13. Electron micrographs showed the cells to have a fragile and irregular cell surface. SKM-1 cells were peroxidase-positive. About 60% of myeloperoxidase (MPO) was released to the culture fluid from SKM-1 cells but only a few percent of MPO was released from HL-60 cells into the culture fluid. The predominant mRNA size of SKM-1 myeloperoxidase was 3.3 kb although there was a smaller size as well. Fluorescent in situ hybridization of MPO mRNA showed strong staining in 5% to 10% of SKM-1 cells and of bone marrow cells from patients with myelogenous leukemia, while all cells from HL-60 were positive.

Six kinds of human herpes viruses have been identified and classified on the basis of structure and characteristics. We studied the identification and classification of these types using PCR to amplify the virus-specific DNA sequences. This method showed higher sensitivity than the conventional method of virus isolation and culture for HSV and CMV detection. For each positive control, the viral DNA was amplified only when the complementary primers themselves were used. PCR apparently detects only the activated virus, because normal controls were negative when this method was used. Therefore, the present method is thought to closely reflect viral activation and infectious diseases in patients with latent infections.

Adenine phosphoribosyltransferase (APRT) deficiency causes 2,8-dihydroxyadenine(DHA) urolithiasis and renal failure. Recently, two different common mutations were identified; one was APRT* J with a substitution of ACG for ATG at codon 136, called "Japanese-type", another was APRT* Q0 with TGA for TGG at codon 98. Approximately 98% of all Japanese patients with this disorder have been estimated to have these mutations APRT* J (approximately 80%) and/or APRT*Q0 (approximately 20%). We developed a diagnostic method to detect these genotypes. After gene amplification by PCR, target DNA was hybridized with a biotinylated specific probe in the presence of the non-labelled competitive probe on a dot-blotted membrane. To detect the APRT* J (or APRT* Q0) mutation, the biotinylated APRT* J (or APRT* Q0) probe and non-labelled normal probe for the same region were used as specific and competitive probes, respectively. After incubation at 60 degrees C for 30 min, the temperature was gradually decreased from 60 degrees C to 40 degrees C during 120 min, and then incubation was continued at 40 degrees C for 30 min. By using method, we were able to omit the posthybridization process, and the detecting signal was clear and highly specific. This method is useful for detecting point mutations in other genes.

About 50% of Japanese have been estimated to possess at least one ALDH2*2 allele with a substitution of AAA for GAA at codon 487 of the aldehyde dehydrogenase gene. This mutation is tightly associated with the sensitivity of an individual to alcohol. We developed a method of identifying the ALDH2*2 allele by a non-radioactive technique. DNA from individuals was subjected to polymerase chain reaction in which part of the aldehyde dehydrogenase 2 gene was amplified. After dot-blotting onto nylon membranes, the DNA was hybridized with biotin-labelled allele-specific oligonucleotides. Determination of genotypes on 77 unrelated healthy Japanese individuals, using the conventional method and our new method with gradient hybridization temperature and competitive oligonucleotides, indicated that the latter was superior to the former.

The mutations of codon 17, 23, 58, and 347 of rhodopsin gene were investigated in 24 unrelated Japanese families including 33 patients with autosomal dominant retinitis pigmentosa (ADRP). A patient with codon 17 mutation (Thr-17-Met, ACG-->ATG) and a family including 4 patients with codon 347 mutation (Pro-347-Leu, CCG-->CTG) were detected among them. Their clinical findings were extremely different between the two mutations. The former showed type 2 and the latter showed type 1 ADRP. No mutation of codon 23 and 58 was detected in any families so far analyzed in the present study. Clinical findings associated with the mutation in codon 17 and 347 of the rhodopsin gene show an existence of allelic heterogeneity.

The human IgG subclasses have specific characteristics in response to respective antigens, and determination of their characteristics is important in analysis of infectious, autoimmune and other diseases. We developed quantitative EIA (ELISA) assays for Japanese human IgG subclasses with excellent reproducibilities using monoclonal antibodies. The assays enable determinations between 0.4 ng/ml and 2,000 ng/ml. The serum IgG subclass levels (mean+SD) in healthy adults are as follows: IgG1, 5.93 + 2.07 mg/ml (59.94%); IgG2, 3.36 + 1.84 mg/ml (32.97%); IgG3, 0.30 + 0.19 mg/ml (3.07%); and IgG4, 0.22 + 0.15 mg/ml (2.34%). Excellent correlation was obtained between total IgG level measured by EIA using anti-whole human serum and the sum of the four IgG subclasses (IgG1+IgG2+IgG3+IgG4). Samples from every patient with M protein of IgG1 and IgG2 types shown by M band on immunoelectrophoresis also had the highest level in four IgG subclasses.

The presence of hepatitis C virus sequence was detected in liver tissue extracts by the polymerase chain reaction (PCR) method using primers of non-coding region in six out of eight cases with chronic hepatitis seropositive for Chiron's antibody. Subsequently, liver extracts from these cases were added to cell cultures of Chang cells for 3 days. The liver extracts of the six cases positive for PCR appeared to infect the Chang cells.

We analyzed activating mutations of N-ras and K-ras by the polymerase chain reaction and oligonucleotide hybridization in hematological disorders. Activating mutations of these codons were detected in 4 of 20 cases of myelodysplastic syndrome (MDS) and 15 of 77 cases of acute myelogenous leukemia (AML). Our of 19 cases of MDS and AML who carried active mutations, 7 cases were found to have two or more distinct mutations in activating codons of N-ras and K-ras. Ras mutation was found preferentially in progressive disease such as refractory anemia with excess of blasts (RAEB) of RAEB in transformation (RAEB-t). A relatively high incidence of ras mutation was found in M5 AML (40%). No ras mutations were found in other hematological disorders, such as acute lymphoblastic leukemia and chronic myelogenous-leukemia. The most frequent amino acid substitution was that of an aspartate for glycine at codon 12 of N-ras resulting from G to A mutation (11/35). The survival of AML patients who carried ras mutations showed no significant differences from those without ras mutations calculated by Kaplan-Meier. Seven cases of MDS and 7 cases of AML patients could be investigated at various points during their clinical course. Among these 14 cases, we found 2 interesting cases of MDS. The first case lost multiple clones carrying ras mutations during disease progression, the second case acquired mutation of the ras gene during disease progression. These results suggested that multiple point mutations of ras genes may not be initiating events but may contribute to a clonal evolution of MDS and AML.

About 79% of all the Japanese patients with adenine phosphoribosyltransferase (APRT) deficiency have been estimated to possess at least one APRT*J allele with a substitution of ACG for ATG at codon 136. We developed a non-radioactive method for diagnosing genotypes of this disease. Part of the genomic DNA including the mutation site of the APRT*J allele was amplified using polymerase chain reaction and the amplified product was dot-blotted onto nylon membranes and then hybridized with either APRT*J-specific or non-APRT*J-specific synthetic oligonucleotides labelled at the 5' termini with biotin in the presence of non-labelled competitive synthetic sequences. The temperature was gradually decreased during the hybridization. When competitive sequences were omitted, difference in the intensity of the hybridization between APRT*J-containing and non-containing samples was not sufficiently clear to differentiate the genotypes. When an excess amount of competitive sequences was added in addition to biotin-labelled oligonucleotides, this method effectively differentiated samples containing only APRT*J alleles from those containing only non-APRT*J alleles. The present method was also useful to differentiate samples with both APRT*J and non-APRT*J alleles from those having only either of the alleles. An equivalent procedure using competitive sequence for hybridization and gradually decreasing the temperature will be useful for detecting point mutations in other genes.

Several recent studies based on restriction fragment length polymorphism analysis have supported the concept that the accumulation of multiple genetic alterations converts a normal cell to a malignant cell. Activation of oncogenes and/or inactivation of tumor suppressor genes have been observed during tumor progression in colorectal cancer, lung cancer, and breast cancer. To investigate the possibility that multiple genes are altered during the progression of renal cell carcinoma, we have used restriction fragment length polymorphism markers throughout the genome to test for loss of heterozygosity in 38 renal cell carcinomas. Nearly 64% of the tumors had lost heterozygosity on the short arm of chromosome 3. We also observed loss of heterozygosity averaging about 30% at informative loci on six other chromosomal arms (chromosomes 5q, 6q, 10q, 11q, 17p, and 19p). These results lead us to suspect the existence of several tumor suppressor genes associated with carcinogenesis of renal cell carcinoma.

We studied an anti-insulin receptor antibody (IRAb) assay that excludes the influence of serum insulin and anti-insulin antibody in patients with anti-insulin antibody and normal subjects. The placental membranes strongly bound with 125I-insulin at 4 degrees C. The insulin specificity of the radioreceptor assay was confirmed by adding excess non-labeled insulin and other human hormones to the assay system. The strong correlation between the receptor binding reactivity (%) and the anti-insulin antibody levels was noted in the conventional direct IRAb assay (r = -0.95), but not in the present IRAb assay (r = 0.46) in 10 clinical samples. The placental membranes were stable as the target insulin receptor for IRAb assay at -80 degrees C for at least 4 months. A significant difference in IRAb levels was found between 10 patients with positive anti-insulin antibody and 20 normal controls (p less than 0.01, student t test). The coexistence of insulin and anti-insulin antibody were removed by absorbance to silicagel and by utilizing the two-step (indirect) assay, respectively. IRAb assay without the influence of serum cofactors showed excellent reproducibilities (CV 4.4% (N = 5) and 12.5% (N = 5) in within and between assay variations, respectively).

The platelet-associated IgG (PAIgG) has been reported to elevate in the patients with idiopathic thrombocytopenic purpura (ITP) and other autoimmune diseases. However, low PAIgG levels have been often recognized in thrombocytopenia. We speculated about the increasing of other platelet-associated proteins in those patients, and tried to determine platelet-associated IgM (PAIgM) and platelet-associated C3 (PAC3) using a high sensitive competitive micro-ELISA as well as PAIgG. Our results showed the specific elevation of PAIgM and PAC3 in thrombocytopenia as well as the PAIgG level (p less than 0.01). Further, the weak correlations among these levels were found (PAIgG/PAIgM: n = 7, correlation coefficient (r) = 0.55, PAIgG/PAC3: n = 73, r = 0.61, PAIgM/PAC3: n = 56, r = 0.39). We discussed on the possibility that the PAIgM and PAC3 also could be an indicator for the platelet injury and may cause the short platelet life span resulting thrombocytopenia as well as PAIgG.