Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Point Mutation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources
PubMed2003

[Detection and analysis of the new kind of G743C and G743A point mutation of HBV P gene in hepatitis B virus infected patients resistant to lamivudine].

OBJECTIVE: To explore the point mutation in hepatitis B virus polymerase (HBV P) gene in HBV-infected patients resistant to lamivudine. METHODS: HBV P gene was amplified by PCR and the products was sequenced to analyze the YMDD mutation. Then the variants were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) with the following restriction enzymes: Fok I, Ssp I, Alw441 and were separated by 8.0% polyacrylamide gel electrophoresis. RESULTS: Comparing with the sequences of standard HBV genome, there were 16 patients with G743C mutation and 1 patient with G743A mutation, and the codon ATG turned to ATC and ATA, YMDD motif changed into YIDD. But this kind of YIDD mutation was not proved by PCR-RFLP assay in the 17 patients. CONCLUSIONS: The G743C and G743A mutations in HBV P gene, resulting in YMDD motif changed into YIDD, are detected only by direct sequencing, not by PCR-RFLP. The new kind of G743C and G743A point mutations in HBV P gene is important for the detection of HBV P gene YMDD mutation.

Adult↗
PubMed2003

[A case report and pedigree study of a single point mutation in RET proto-oncogene and type 2B multiple endocrine neoplasia].

OBJECTIVE: To determine the relationship between a single point mutation in RET proto-oncogene and the occurrence of multiple endocrine neoplasia type 2B (MEN-2B) in a Chinese pedigree. METHODS: We used the methods of polymerase chain reaction (PCR), reverse transcriptase polymerase chain reaction (RT-PCR) and direct gene sequencing of PCR products by an automated DNA sequencer to scan the entire exon 16 of RET proto-oncogene in the tumor (c)DNA from one patient with MEN-2B and the leukocyte DNA from this patient and both of his parents. RESULTS: We found the same mutation Met(ATG)-->Thr(ACG) at codon 918 in exon 16 of RET proto-oncogene in both the tumor (c)DNA and leukocyte DNA of the MEN-2B patient in the form of homozygous missense mutation, but there was no corresponding mutation in leukocytes DNA of his parents. CONCLUSION: We propose that in Chinese population, the point mutation M918T is also associated with the onset of MEN-2B and this case of MEN-2B is sporadic. Thus it may provide a genetic basis for the early diagnosis and treatment of patients suffering from MEN-2B and their at-risk family members in Chinese population.

Adolescent↗
PubMed1998

A case of small pancreatic cancer diagnosed by serial follow-up studies promptly by a positive K-ras point mutation in pure pancreatic juice.

We report a 74-yr-old woman who was referred to our hospital because of abdominal fullness. ERP showed a questionable irregularity of the main pancreatic duct at the body. Examination of pure pancreatic juice was positive for K-ras point mutation at codon 12 and negative for cytology. Because neither US nor CT showed apparent lesions in the pancreas, we decided to follow up the patient with serial ERP and pure pancreatic juice studies at 3-month intervals. No changes had been seen up to 18 months later, when cytology was conclusive for malignancy with an apparent stenosis of the main pancreatic duct at the body. Distal pancreatectomy with splenectomy was performed. A round mass, 12 mm in diameter, was found in the body, which proved to be an adenocarcinoma at histological examination. No extrapancreatic extension and metastases were noted. Although positive K-ras point mutation has been reported in some cases of adenoma or mucinous cell hyperplasia of the pancreas and chronic pancreatitis, our case, along with previous reports, indicated the importance of testing K-ras point mutation in pure pancreatic juices for the diagnosis of pancreatic cancer at an early stage.

Adenocarcinoma↗
PubMed2002

Unlike AML1, CBFbeta gene is not deregulated by point mutations in acute myeloid leukemia and in myelodysplastic syndromes.

The core-binding factor (CBF) complex is a heterodimeric transcription factor composed of 2 subunits, CBFalpha and CBFbeta, that play a major role in hematopoiesis. Both members of the CBF complex are frequently altered in acute myeloid leukemia (AML) by translocation, most commonly t(8;21), t(12;21), and t(3;21) for CBFalpha, located in 21q22, and inv(16)(p13;q22) for CBFbeta, located on 16q22. Recently, a new mechanism of alteration of CBFalpha, by point mutation, has been reported in myeloid malignancies, particularly in M0 AML. In the present study, we found no point mutation of the CBFbeta gene in 30 myelodysplastic syndromes and 100 AMLs, suggesting a limited role, if any, of CBFbeta point mutations in those disorders.

Acute Disease↗
PubMedDate not supplied

Identification of a rare point mutation at C-terminus of merozoite surface antigen-1 gene of Plasmodium falciparum in eastern Indian isolates.

Merozoite surface antigen-1 (MSA-1) of Plasmodium falciparum is highly immunogenic in human. Several studies suggest that MSA-1 protein is an effective target for a protective immune response. Attempt has been made to find new point mutations by analyzing 244 bp [codon 1655(R) to 1735 (I)] relatively conserved C-terminus region of MSA-1 gene in 125 isolates. This region contains two EGF like domains, which are involved in generating protective immune response in human. Point mutations in this region are very much important in view of vaccine development. Searching of mutational hot spots in MSA-1 protein by sequencing method in a representative number of isolates is quite critical and expensive. Therefore, in this study slot blot and PCR-SSCP method have been used to find out new mutations in the individual isolates showing alterations in the mobility of DNA fragment. Sequencing of the altered bands from the SSCP gel shows a rare non-synonymous point mutation in 7 (5.6%) of the 125 isolates at amino acid position 1704 of MSA-1 gene where isoleucine is replaced by valine.

Animals↗
PubMed1995

A novel point mutation in the mitochondrial tRNA(Ser(UCN)) gene detected in a family with MERRF/MELAS overlap syndrome.

We found a new point mutation in the mitochondrial tRNA(Ser(UCN)) gene in a family with MERRF/MELAS overlap syndrome by screening for heteroplasmy by means of chemical cleavage of mismatch (CCM). Our strategy was based on the previous observations that most pathogenic mtDNA mutations in mitochondrial encephalomyopathies are heteroplasmic, whereas almost all neutral mitochondrial polymorphisms are homoplasmic. CCM followed by nucleotide sequencing of the corresponding region of the mitochondrial genome revealed a heteroplasmic mutation at nt 7512 in the tRNA(Ser(UCN)) gene. The 7512 (T to C) mutation disrupts a highly conserved base pair in the acceptor stem, and this mutation was not found in any of 120 normal controls, or in 43 patients with mitochondrial diseases. The proportion of the mutant mtDNA was 93% in muscle, 76 and 87% in the blood of the patients. A family member without apparent neuromuscular symptoms carried less mutant mtDNA. These findings support the view that this mutation is pathogenic in this family. Detection of heteroplasmy by CCM is an efficient means of screening pathogenic mtDNA point mutations.

Adult↗
PubMed1998

Activating point mutations in the betaC chain of the GM-CSF, IL-3 and IL-5 receptors are not a major contributory factor in the pathogenesis of acute myeloid leukaemia.

A number of mutant growth factor receptors have been described which are constitutively activated and confer factor independence on growth factor dependent cells, possibly through constitutive dimerization in the absence of ligand or induction of a conformational change. Mutations in receptor chains may therefore contribute to the pathogenesis of haemopoietic malignancies, for example by causing constitutive receptor activation or uncontrolled downstream signalling. Since most of the activated mutants reported for the betaC chain of the GM-CSF/IL-3/IL-5 receptor involve point mutations or truncations of the extracellular domain, we have analysed the coding sequence of this region using RT-PCR-SSCP of RNA from blast cells of 31 patients with acute myeloid leukaemia (AML). Two point mutations detected were silent, C301-->T (Cys91) and C1306-->T (Ser426). The latter had previously been identified with an allele frequency of 0.13 in the general population. Two further point mutations detected led to amino acid substitutions, G773-->C (Glu249Gln), which is equivalent to the mouse sequences, and G962-->A (Asp312Asn), both of which were found at similar frequencies in normal controls. Activating mutations of the betaC chain which might contribute to the pathogenesis of the disease are therefore rare in AML.

Acute Disease↗
PubMed1996

Single somatic ras gene point mutation in soft tissue malignant fibrous histiocytomas.

The frequency of ras gene mutations in human soft tissue malignant fibrous histiocytomas within and around the hot spot codons (12, 13, and 61) of all ras genes, (H-ras-1, K-ras-2, and N-ras) was studied by nested polymerase chain reaction and direct DNA sequencing from archival formalin-fixed, paraffin-embedded tissue. Light microscopy and immunohistochemistry served to define malignant fibrous histiocytoma. All of the four differentiation subtypes (storiform-pleomorphic, inflammatory, myxoid, and giant cell) were investigated. Nine of thirty-two malignant fibrous histiocytomas (28%) contained ras gene point mutations. The highest incidence was found in the myxoid subtype (four of nine). H-ras-1 gene codon 12.2 was the only codon affected and contained in all mutated cases a GGC-->GTC exchange. Seven of the nine mutations were homozygous and probably affected more than 80% of the tumor DNA. The flanking regions of all hotspot codons did not contain any point mutation. The presence of a single and often homozygous point mutation of the H-ras-1 gene, especially in myxoid malignant fibrous histiocytoma could serve as a basis for further genomic discrimination of myxoid sarcomas.

Aged↗
PubMed1994

Lack of synergistic association between human papillomavirus and ras gene point mutation in laryngeal carcinomas.

The spectrum of human papillomavirus (HPV) subtypes in laryngeal carcinomas was investigated by combined polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis. HPV DNA was detected in 11 (24%) of 45 cases, including HPV 16 in 9 cases and HPV 18 in 2 cases. Other HPV subtypes commonly found in the female genital organs were not detected. In addition, the point mutation of codons 12 and 13 in c-Ki-ras-2, c-Ha-ras-1, and N-ras genes was studied by the PCR-single-strand conformational polymorphism (SSCP) method. Of 45 cases tested, only 1 had a point mutation of c-Ki-ras-2 gene at codon 12. These results indicate that the incidence of ras gene point mutation is uncommon and that the synergistic effect of HPV infection and ras gene activation in laryngeal carcinogenesis is probably rare.

Adult↗
PubMed2005

Point mutations in the DNA- and cNMP-binding domains of the homologue of the cAMP receptor protein (CRP) in Mycobacterium bovis BCG: implications for the inactivation of a global regulator and strain attenuation.

The genome of Mycobacterium tuberculosis H37Rv includes a homologue of the CRP/FNR (cAMP receptor protein/fumarate and nitrate reduction regulator) family of transcription regulators encoded by Rv3676. Sequencing of the orthologous gene from attenuated Mycobacterium bovis Bacille Calmette-Guérin (BCG) strains revealed point mutations that affect the putative DNA-binding and cNMP-binding domains of the encoded protein. These mutations are not present in the published sequences of the Rv3676 orthologues in M. bovis, M. tuberculosis or Mycobacterium leprae. An Escherichia coli lacZ reporter system was used to show that the M. tuberculosis Rv3676 protein binds to DNA sites for CRP, but this DNA binding was decreased or abolished with the Rv3676 protein counterparts from BCG strains. The DNA-binding ability of the M. tuberculosis Rv3676 protein was decreased by the introduction of base changes corresponding to the BCG point mutations. Conversely, the DNA binding of the BCG Rv3676 proteins from BCG strains was restored by removing the mutations. These data show that in this reporter system the point mutations present in the Rv3676 orthologue in BCG strains render its function defective (early strains) or abolished (late strains) and suggest that this protein might be naturally defective in M. bovis BCG strains. This raises the possibility that a contributing factor to the attenuation of BCG strains may be an inability of this global regulator to control the expression of genes required for in vivo survival and persistence.

Amino Acid Sequence↗
PubMed1999

A novel and de novo spontaneous point mutation (Glu271STOP) of the antithrombin gene results in a type I deficiency and thrombophilia.

We describe a novel, de novo point mutation in one antithrombin (AT) allele resulting in type I AT deficiency and thrombophilia. Low plasma AT activity as well as low plasma AT antigen were documented in the propositus, but not in the parents, or in a male sibling. AT gene analysis by sequencing polymerase chain reaction-amplified genomic DNA from exon 5 of the propositus revealed a novel point mutation, GAG-->TAG at codon 271, resulting in a stop codon (Glu271STOP). This mutation was not demonstrable in the other members of his immediate family. DNA marker polymorphism analysis indicated the expected parentage. Based on allele frequency data for Caucasians in the United States the cumulative paternity index, or CPI, for the propositus and his father is 219,077. This corresponds to a probability of paternity of 99.9995% based on a prior probability of 50%. Included in this analysis is a linkage analysis of a trinucleotide repeat in intron 5 of the AT gene of the various family members, which also confirmed maternity and paternity. These studies provide documentation of the first spontaneous mutation of an AT gene in a thrombophilic individual, resulting in a type I AT deficiency.

Adolescent↗
PubMed1992

Absence of point mutation of N-ras oncogene in bone marrow cells with aplastic anemia.

Point mutation of N-ras oncogene at codons 12, 13 and 61 was studied in the bone marrow cells of patients with typical aplastic anemia using the polymerase chain reaction method for DNA amplification and dot blot hybridization to synthetic oligonucleotide probes. Point mutation was observed in none of the 15 patients studied. These findings indicate either that the pathogenesis of typical aplastic anemia is different from that of preleukemic states of myelodysplastic syndrome or acute leukemia in clonal evolution, or that the overlapping area sharing a common pathogenesis is much smaller than was presumed.

Anemia, Aplastic↗
PubMed2001

A point mutation in the N-terminal coiled-coil domain releases c-Fes tyrosine kinase activity and survival signaling in myeloid leukemia cells.

The c-fes locus encodes a 93-kDa non-receptor protein tyrosine kinase (Fes) that regulates the growth and differentiation of hematopoietic and vascular endothelial cells. Unique to Fes is a long N-terminal sequence with two regions of strong homology to coiled-coil oligomerization domains. We introduced leucine-to-proline substitutions into the coiled coils that were predicted to disrupt the coiled-coil structure. The resulting mutant proteins, together with wild-type Fes, were fused to green fluorescent protein and expressed in Rat-2 fibroblasts. We observed that a point mutation in the first coiled-coil domain (L145P) dramatically increased Fes tyrosine kinase and transforming activities in this cell type. In contrast, a similar point mutation in the second coiled-coil motif (L334P) was without effect. However, combining the L334P and L145P mutations reduced transforming and kinase activities by approximately 50% relative to the levels of activity produced with the L145P mutation alone. To study the effects of the coiled-coil mutations in a biologically relevant context, we expressed the mutant proteins in the granulocyte-macrophage colony-stimulating factor (GM-CSF)-dependent myeloid leukemia cell line TF-1. In this cellular context, the L145P mutation induced GM-CSF independence, cell attachment, and spreading. These effects correlated with a marked increase in L145P protein autophosphorylation relative to that of wild-type Fes. In contrast, the double coiled-coil mutant protein showed greatly reduced kinase and biological activities in TF-1 cells. These data are consistent with a role for the first coiled coil in the negative regulation of kinase activity and a requirement for the second coiled coil in either oligomerization or recruitment of signaling partners. Gel filtration experiments showed that the unique N-terminal region interconverts between monomeric and oligomeric forms. Single point mutations favored oligomerization, while the double point mutant protein eluted essentially as the monomer. These data provide new evidence for coiled-coil-mediated regulation of c-Fes tyrosine kinase activity and signaling, a mechanism unique among tyrosine kinases.

Cell Survival↗
PubMed1990

Point mutations of c-ras genes in human bladder cancer and kidney cancer.

Point mutations of c-ras genes at codons 12, 13 and 61 were analyzed in 26 cases of bladder cancer and 16 cases of kidney cancer. DNA prepared from either frozen tissues or 10% formalin-fixed, paraffin-embedded tissues were amplified by means of polymerase chain reaction methods, and mutations were analyzed by dot blot hybridization assays with oligonucleotide probes. In three cases of bladder cancer c-ras mutations were found, at codons 13 and 61 of c-Ha-ras and at codon 61 of c-Ki-ras, while no mutation was found in kidney cancer. No mutation was found in normal bladder epithelial tissues from the same patients. Our findings, taken together, may indicate relative scarcity of c-ras mutations in these types of human cancer. The results of dot blot hybridization assays and DNA sequencing showed a G-to-C transition of the first nucleotide at codon 13 c-Ha-ras. This is the first time that such a point mutation has been detected in human cancer tissues.

Aged↗
PubMed2001

Occupational cancer genetics: infrequent ras oncogenes point mutations in lung cancer samples from chromate workers.

BACKGROUND: Chromium carcinogenicity and mutagenicity are no longer disputed. However, although chromium has various genetic effects that induce cancer, its mechanism of inducing lung cancer in humans is still not fully understood. p53, a tumor suppressor gene, was found to be infrequently mutated in samples of lung cancer in workers with long occupational exposure to chromium, suggesting other cancer-related genes to be targeted in such tumors. METHODS: To assess the contribution of the ras oncogenes in the pathogenesis of chromate-related lung cancer, we studied point mutations at the critical positions of codons 12, 13, and 61 of the Ha-ras and Ki-ras oncogenes in 38 lung cancer samples derived from Japanese patients who worked in the chromate industry for long periods. We used both radioactive isotope and non-radioisotope PCR-SSCP techniques. RESULTS: The results of this study demonstrated that activation of ras genes due to point mutations in chromate-related lung cancer is a rare event. CONCLUSIONS: Ras oncogenes activated by point mutations do not have a major role in the process of tumorigenesis of chromate-related lung cancer.

Adult↗
PubMed1995

Point mutations of mitochondrial genome in Parkinson's disease.

Oxidative stress and subsequent energy crisis have been proposed as the cause of nigral neuronal cell death in Parkinson's disease. We have reported defects in the mitochondrial respiratory chain and increased amount of deleted mitochondrial genome in the nigrostriatal system of patients with Parkinson's disease. Deletion in mitochondrial DNA could be ascribed to somatically acquired premature aging leading to cell death. To elucidate the contribution of maternally transmitted point mutations in mitochondrial DNA to the premature DNA damages, we employed a direct sequencing system and analyzed the total nucleotide sequences of mitochondrial DNA in the brains of five patients with idiopathic Parkinson's disease. There were no predominant point mutations among the patients in contrast to some neuromuscular diseases. However, each patient had several point mutations that would result in a significant change in the gene products. Some of these mutations may be involved either in the increased production of oxygen radicals from the mitochondrial respiratory chain or in the increased susceptibility of the respiratory chain components to oxidative damage. We propose that some of these mutations can be regarded as one of the risk factors accelerating degeneration of nigrostriatal pathway in Parkinson's disease.

Base Sequence↗
PubMed1993

Competitive assay to improve the specificity of detection of single-point mutations in alpha 1-antitrypsin deficiency.

Allele-specific oligonucleotides are used widely for the detection of single point mutations in genes. A modification of this assay based on competition has been developed for detection of the Z mutation of alpha 1-antitrypsin (alpha 1-AT). The normal alpha 1-AT allele is referred to as M, and the Z mutation arises from a single base substitution. Amplified DNA products corresponding to homozygous M, heterozygous MZ, and homozygous Z obtained by the polymerase chain reaction were incubated with a twofold molar excess of unlabeled oligonucleotide prior to hybridization with a radiolabeled oligonucleotide. Thus, initial incubation with unlabeled M-specific oligonucleotide was followed by hybridization with radiolabeled Z-specific oligonucleotide, and vice versa. This assay increased the specificity of single-point mutation detection three- to four-fold. Furthermore, specific hybridization was obtained at a lower temperature as a consequence of improving the signal-to-noise ratio.

Base Sequence↗
PubMed2001

No evidence for point mutations of the calcium-sensing receptor in familial idiopathic hypercalciuria.

BACKGROUND: Idiopathic hypercalciuria (IH) is frequently associated with nephrolithiasis. As 40% of patients have a positive familial history of IH, an autosomal dominant mode of inheritance has been suggested. Numerous genes have been studied in this regard but none have been found to be linked to IH. Mutation of the calcium-sensing receptor (CaR) has never been studied. Therefore, we conducted a study to detect such mutations. METHODS: Seven families with IH and nephrolithiasis were recruited in a prospective study. Forty-two family members underwent 24-h urine calcium measurement. Twenty-five of them with 24-h hypercalciuria also underwent extensive metabolic evaluation. Blood samples were collected in one or two affected family members in each family and exons 2-7 of the CaR gene were sequenced. RESULTS: In the seven families, at least one parent and more than half of the children had hypercalciuria (21/30), consistent with autosomal dominant inheritance. Among the nine affected family members whose CaR gene has been studied, all nine had absorptive hypercalciuria, three also had fasting hypercalciuria, and one had renal phosphorous leak. No mutation of the CaR gene was detected in these seven families. Two previously reported polymorphisms were detected, each of them in five families: A986S and C-to-T change at -60 in intron 5. CONCLUSION: In these seven families, IH is not related to the CaR gene mutation. Although we cannot exclude that point mutations can be found in other families, familial IH does not seem to be generally associated with CaR mutation.

Adult↗