HPRT mutation spectrum reporting.
Explore the source record for details and available documents.
DNA, Complementary↗
SEARCH · PubMed Health
Results for “Mutation spectrum”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Spontaneous mutation spectrum at the lambda cII locus in liver, lung, and spleen tissue of Big Blue transgenic mice.
Big Blue mice harbor a recoverable transgene in a lambda/LIZ shuttle vector. In the standard assay, in vivo mutations are measured in the bacterial lacI gene using a labor-intensive color plaque assay. Applying a simpler assay [Jakubczak et al. (1996): Proc Natl Acad Sci USA 93:9073-9078], we measured mutations in the lambda cII gene portion of the transgene. Spontaneous clear plaque mutants were analyzed from liver, lung, and spleen of five untreated mice. Of 314 mutants, 182 (58%) had independent mutations, 74 (23.5%) appeared clonal, and 58 (18.5%) showed no cII mutations. Of 182 independent cII mutations, 156 (85.7%) were base substitutions, 20 (10.9%) were frameshifts, and 6 (3.2%) were multiple substitutions and one deletion. G:C --> A:T transitions were the predominant base substitution (78% of these at CpG sites). The major mutation hotspot, a six G run and its 3' flanking T at bases 179 to 185, comprised 18.7% of the independent mutations. Other hotspots were positions 103, 196, and 212. The in vivo cII spectrum had a significantly higher proportion of G --> A and G --> T mutations and fewer frameshifts than reported in vitro. The cII and published lacI spectra are similar, though G --> A transitions and deletions were fewer in the cII gene. The cI gene was sequenced in 48 mutants with no cII mutations and most had cI mutations: 81.3% base substitutions and 18.7% frameshifts. We conclude that the cII/cI system is insensitive to deletion events, but is useful for detecting point mutations.
Animals↗
Mutational spectrum of the iduronate-2-sulfatase (IDS) gene in 36 unrelated Russian MPS II patients.
We present a mutational analysis of the iduronate-2-sulfatase (IDS) gene of 36 Russian patients with Hunter syndrome. Among 29 mutant alleles, there were 19 missense mutations, 1 nonsense mutation, 6 mutations affecting splice sites, and 3 major structural alterations resulting in deletions. Of the 25 different mutations, 15 are novel and unique. Most of the missense mutations result in intermediate or severe phenotypes.
Blotting, Southern↗
Mutation spectrum of the gene encoding the beta subunit of rod phosphodiesterase among patients with autosomal recessive retinitis pigmentosa.
Mutations in the gene encoding the beta subunit of rod cGMP phosphodiesterase are known causes of photoreceptor degeneration in two animal models of retinitis pigmentosa, the rd (retinal degeneration) mouse and the Irish setter dog with rod/cone dysplasia. Here we report a screen of 92 unrelated patients with autosomal recessive retinitis pigmentosa for defects in the human homologue of this gene. We identified seven different mutations that cosegregate with the disease. They were found among four patients with each patient heterozygously carrying two mutations. All of these mutations are predicted to affect the putative catalytic domain, probably leading to a decrease in phosphodiesterase activity and an increase in cGMP levels within rod photoreceptors. Mutations in the gene encoding the beta subunit of rod phosphodiesterase are the most common identified cause of autosomal recessive retinitis pigmentosa, accounting for approximately 4% of cases in North America.
3',5'-Cyclic-GMP Phosphodiesterases↗
Bruton's tyrosine kinase: cell biology, sequence conservation, mutation spectrum, siRNA modifications, and expression profiling.
Bruton's tyrosine kinase (Btk) is encoded by the gene that when mutated causes the primary immunodeficiency disease X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (Xid) in mice. Btk is a member of the Tec family of protein tyrosine kinases (PTKs) and plays a vital, but diverse, modulatory role in many cellular processes. Mutations affecting Btk block B-lymphocyte development. Btk is conserved among species, and in this review, we present the sequence of the full-length rat Btk and find it to be analogous to the mouse Btk sequence. We have also analyzed the wealth of information compiled in the mutation database for XLA (BTKbase), representing 554 unique molecular events in 823 families and demonstrate that only selected amino acids are sensitive to replacement (P < 0.001). Although genotype-phenotype correlations have not been established in XLA, based on these findings, we hypothesize that this relationship indeed exists. Using short interfering-RNA technology, we have previously generated active constructs downregulating Btk expression. However, application of recently established guidelines to enhance or decrease the activity was not successful, demonstrating the importance of the primary sequence. We also review the outcome of expression profiling, comparing B lymphocytes from XLA-, Xid-, and Btk-knockout (KO) donors to healthy controls. Finally, in spite of a few genes differing in expression between Xid- and Btk-KO mice, in vivo competition between cells expressing either mutation shows that there is no selective survival advantage of cells carrying one genetic defect over the other. We conclusively demonstrate that for the R28C-missense mutant (Xid), there is no biologically relevant residual activity or any dominant negative effect versus other proteins.
Agammaglobulinaemia Tyrosine Kinase↗
Posttreatment with sodium arsenite alters the mutational spectrum induced by ultraviolet light irradiation in Chinese hamster ovary cells.
Arsenic, a potent carcinogen, fails to induce gene mutations in mammalian cells. However, posttreatment of ultraviolet light (UV) irradiated cells with sodium arsenite synergistically enhances the mutation frequency on the hypoxanthine (guanine) phosphoribosyltransferase locus. To investigate the molecular mechanism of the comutagenic effects of sodium arsenite, we characterized the alterations of nucleotide sequences in 30 UV-induced and 39 sodium arsenite enhanced hprt mutants from Chinese hamster ovary K1 cells by direct sequencing of mRNA-PCR amplified cDNA. The majority of sequence alterations derived from UV irradiation (80%) and from sodium arsenite posttreatment (70%) were single base substitutions. UV irradiation induced all types of base substitutions. Among them, 57% were transversions. The frequency of transversions increased to 70% in sodium arsenite enhanced mutants. While base substitutions observed in UV-induced mutants were evenly distributed along with the whole coding region, exons 3 and 8 were most frequently mutated in sodium arsenite enhanced mutants. Sodium arsenite posttreatment did not alter the strand bias for mutation induction, i.e., 73% and 78%, of the mutations were located on the non-transcribed strand in UV-induced and sodium arsenite enhanced mutants, respectively. In contrast to UV-induced mutations, bases at the 5' position of TT and the 3' position of CT sequences were the most frequent mutation sites observed in sodium arsenite enhanced mutants. We hypothesize that sodium arsenite may interfere with the process of mutation fixation of TT and CT dimers during DNA replication.
Animals↗
Dependence of the mutation spectrum in a shuttle plasmid replicated in human lymphoblasts on dose of gamma radiation.
The frequencies and types of mutations induced in the target gene, supF-tRNA, of the shuttle vector pZ189 were analysed following the replication of the gamma-irradiated plasmid in the human lymphoblastoid cell line, GM606. The mutation frequency measured in progeny of unirradiated pZ189 was 1.02 x 10(-4), increasing to 17.5 x 10(-4) at 1000 cGy, and to 63.4 x 10(-4) at 5000 cGy, approximately 17- and 62-fold over background levels, respectively. Simultaneously, the number of plasmids capable of replicating in Escherichia coli decreased with increasing radiation dose to 4% of the control value at 5000 cGy. Electrophoresis of the irradiated DNA showed a correlation between increases in mutation frequency and decreases in plasmid survival, and the formation of open-circular and linear DNA. The majority of the spontaneous (69.8%) and induced mutations (85.7%) at 1000 and 79.4% at 5000 cGy) were base substitutions and were generally of similar types among all groups. However, changes at 2500 (12.7%) and 5000 cGy (13.2%) involving A:T base pairs were greater than those in unirradiated controls (3.4%) or those at 1000 cGy (2.0%). This increase in A:T base pair mutations could be a result of reduced repair fidelity when the DNA is extensively damaged by high doses of ionizing radiation.
Cell Line↗
Mutation spectrum of heat-induced abasic sites on a single-stranded shuttle vector replicated in mammalian cells.
The mutational potency of apurinic/apyrimidinic (AP) sites induced by heat-treatment under acidic conditions has been studied in mammalian cells. Abasic sites were induced on a single-stranded DNA shuttle vector carrying the supF tRNA gene, eliminating, therefore, any ambiguity concerning the damaged strand. This vector was able to replicate both in mammalian cells and in bacteria where the mutations induced in animal cells on the supF tRNA gene were screened by the white/blue beta-galactosidase assay in the presence of isopropyl-1-thio-beta-D-galactopyranoside and 5-bromo-4-chloro-3-indoyl-beta-D-galactoside. All white colonies contained plasmid with a mutation on the target gene which was directly sequenced. Our results show that one AP site was induced/22 min of heating as measured by sensitivity of DNA to alkali denaturation or treatment with the AP-endonuclease activity of the FPG protein (Fapy-DNA glycosylase). Putative AP sites decrease survival of the plasmid with a lethal hit of one AP site/single-stranded molecule. Mutation frequency was increased by a factor of approximately six after 2 h at 70 degrees C. Most of the induced mutations were point mutations not distributed at random and clustered in the gene region which will give rise to the mature tRNA. Mutations were abolished by treatments that eliminated AP sites such as alkali treatment or incubation with the Fapy-DNA glycosylase protein. Under our experimental conditions, when only single mutations were taken into account, the order of base insertion opposite AP sites was G greater than A greater than T greater than C.
Animals↗
Lead acetate mutagenicity and mutational spectrum in the hypoxanthine guanine phosphoribosyltransferase gene of Chinese hamster ovary K1 cells.
The molecular nature of lead-induced mutations was examined in this study to more thoroughly understand lead mutagenesis. Chinese hamster ovary K1 cells were exposed to 0.5-3 mM lead acetate for 24 h. The median lethal dose (LD50) value was 1.5 mM, and the hypoxanthine guanine phosphoribosyltransferase (HPRT) mutant frequency increased linearly as lead concentrations were raised from 0.5 to 1.5 mM. We also amplified the HPRT cDNAs of 56 independent lead-induced mutants by reverse transcriptase-polymerase chain reaction (PCR). Forty-two mutant cDNAs were successfully amplified: 36 mutants had transcripts of normal or slightly smaller than normal size, and six mutants had large deletions. The other 14 mutants whose HPRT cDNA could not be amplified were subjected to genomic-DNA PCR analysis. All of those mutants had one or more exons missing from their genomic HPRT DNA. DNA sequencing of mutant cDNAs showed that 22 had single-base substitutions, four had small alterations, 10 had single-exon deletions, and six were missing two or three exons. Furthermore, DNA sequencing of the HPRT intron-exon boundaries in eight splice mutants revealed that all of them had single-base substitutions in their genomic DNA. G.C base substitutions occurred 3.3-fold more frequently than A.T base substitutions. Similar frequencies were observed for G.C-->A.T, G.C-->T.A, and G.C-->C.G mutations. These results suggest that G.C base pairs may be the primary target sites for lead mutagenesis.
Animals↗
PTEN mutation spectrum and genotype-phenotype correlations in Bannayan-Riley-Ruvalcaba syndrome suggest a single entity with Cowden syndrome.
Germline mutations in the tumour suppressor gene PTEN have been implicated in two hamartoma syndromes that exhibit some clinical overlap, Cowden syndrome (CS) and Bannayan-Riley-Ruvalcaba syndrome (BRR). PTEN maps to 10q23 and encodes a dual specificity phosphatase, a substrate of which is phosphatidylinositol 3,4,5-triphosphate, a phospholipid in the phosphatidylinositol 3-kinase pathway. CS is characterized by multiple hamartomas and an increased risk of benign and malignant disease of the breast, thyroid and central nervous system, whilst the presence of cancer has not been formally documented in BRR. The partial clinical overlap in these two syndromes is exemplified by the hallmark features of BRR: macrocephaly and multiple lipomas, the latter of which occur in a minority of individuals with CS. Additional features observed in BRR, which may also occur in a minority of CS patients, include Hashimoto's thyroiditis, vascular malformations and mental retardation. Pigmented macules of the glans penis, delayed motor development and neonatal or infant onset are noted only in BRR. In this study, constitutive DNA samples from 43 BRR individuals comprising 16 sporadic and 27 familial cases, 11 of which were families with both CS and BRR, were screened for PTEN mutations. Mutations were identified in 26 of 43 (60%) BRR cases. Genotype-phenotype analyses within the BRR group suggested a number of correlations, including the association of PTEN mutation and cancer or breast fibroadenoma in any given CS, BRR or BRR/CS overlap family ( P = 0.014), and, in particular, truncating mutations were associated with the presence of cancer and breast fibroadenoma in a given family ( P = 0.024). Additionally, the presence of lipomas was correlated with the presence of PTEN mutation in BRR patients ( P = 0.028). In contrast to a prior report, no significant difference in mutation status was found in familial versus sporadic cases of BRR ( P = 0.113). Comparisons between BRR and a previously studied group of 37 CS families suggested an increased likelihood of identifying a germline PTEN mutation in families with either CS alone or both CS and BRR when compared with BRR alone ( P = 0.002). Among CS, BRR and BRR/CS overlap families that are PTEN mutation positive, the mutation spectra appear similar. Thus, PTEN mutation-positive CS and BRR may be different presentations of a single syndrome and, hence, both should receive equal attention with respect to cancer surveillance.
Abnormalities, Multiple↗
p53 mutation spectrum in relation to GSTM1, CYP1A1 and CYP2E1 in surgically treated patients with non-small cell lung cancer.
p53 mutation status was analysed in relation to DNA polymorphisms of GSTM1, CYP1A1 and CYP2E1 from 105 surgically resected non-small cell lung cancer cases. Demographic factors, smoking, occupation, family history, tumour histology, grade and stage were taken into account. p53 mutations, detected either directly by DNA sequencing (P = 0.04, adjusted for smoking) or indirectly by immunostaining (P = 0.06), were overrepresented among CYP1A1 variants. Mutations in exon 8 and transitions at CpG sites in the p53 gene were favoured in this subset. There was no relation between the individual gene polymorphisms or p53 mutations and disease-free survival by Kaplan-Meier analysis. The finding of excess CYP1A1 heterozygotes in individuals with p53 mutations after adjustment for smoking suggests that CYP1A1 activation contributes to lung cancer via p53 inactivation.
Carcinoma, Non-Small-Cell Lung↗
Alteration of cadmium-induced mutational spectrum by catalase depletion in Chinese hamster ovary-K1 cells.
Previously, we have demonstrated that cadmium acetate significantly induces hprt mutation frequency in Chinese hamster ovary (CHO)-K1 and that 3-amino-1,2,4-triazole (3AT), a catalase inhibitor, potentiates the mutagenicity of cadmium [Chem. Res. Toxicol. 9 (1996) 1360-1367]. In this study, we investigate the role of intracellular peroxide in the molecular nature of mutations induced by cadmium. Using 2',7'-dichlorofluorescin diacetate and fluorescence spectrophotometry, we have shown that cadmium dose-dependently increased the amounts of intracellular peroxide and the levels were significantly enhanced by 3AT. Furthermore, we have characterized and compared the hprt mutation spectra in 6-thioguanine-resistant mutants derived from CHO-K1 cells exposed to 4 microM of cadmium acetate for 4h in the absence and presence of 3AT. The mutation frequency induced by cadmium and cadmium plus 3AT was 11- and 16-fold higher than that observed in untreated populations (2.2 x 10(-6)), respectively. A total of 40 and 51 independent hprt mutants were isolated from cadmium and cadmium plus 3AT treatments for mRNA-polymerase chain reaction (PCR), genomic DNA-PCR and DNA sequencing analyses. 3AT co-administration significantly enhanced the frequency of deletions induced by cadmium. Cadmium induced more transversions than transitions. In contrast, 3AT co-administration increased the frequency of GC-->AT transitions and decreased the frequencies of TA-->AT and TA-->GC transversions. Together, the results suggest that intracellular catalase is important to prevent the formation of oxidative DNA damage as well as deletions and GC-->AT transitions upon cadmium exposure.
Acetates↗
Mutational spectrum of beta-catenin, AXIN1, and AXIN2 in hepatocellular carcinomas and hepatoblastomas.
Activation of Wnt signaling through beta-catenin mutations contributes to the development of hepatocellular carcinoma (HCC) and hepatoblastoma (HB). To explore the contribution of additional Wnt pathway molecules to hepatocarcinogenesis, we examined beta-catenin, AXIN1 and AXIN2 mutations in 73 HCCs and 27 HBs. beta-catenin mutations were detected in 19.2% (14 out of 73) HCCs and 70.4% (19 out of 27) HBs. beta-catenin mutations in HCCs were primarily point mutations, whereas more than half of the HBs had deletions. AXIN1 mutations occurred in seven (9.6%) HCCs and two (7.4%) HBs. The AXIN1 mutations included seven missense mutations, a 1 bp deletion, and a 12 bp insertion. The predominance of missense mutations found in the AXIN1 gene is different from the small deletions or nonsense mutations described previously. Loss of heterozygosity at the AXIN1 locus was present in four of five informative HCCs with AXIN1 mutations, suggesting a tumor suppressor function of this gene. AXIN2 mutations were found in two (2.7%) HCCs but not in HBs. Two HCCs had both AXIN1 and beta-catenin mutations, and one HCC had both AXIN2 and beta-catenin mutations. About half the HCCs with AXIN1 or AXIN2 mutations showed beta-catenin accumulation in the nucleus, cytoplasm or membrane. Overall, these data indicate that besides the approximately 20% of HCCs and 80% of HBs with beta-catenin mutations contributing to hepatocarcinogenesis, AXIN1 and AXIN2 mutations appear to be important in an additional 10% of HCCs and HBs.
Amino Acid Sequence↗
Base transitions dominate the mutational spectrum of a transgenic reporter gene in MSH2 deficient mice.
Tumors derived from individuals with hereditary nonpolyposis colorectal cancer syndrome frequently demonstrate mutations in both alleles of hMSH2, a key gene in DNA mismatch repair (MMR). Sporadic tumors also frequently exhibit MMR deficiency. In keeping with the role of MMR in the maintenance of genome integrity, mice deficient in MSH2 via gene targeting demonstrate a high incidence of thymic lymphomas and small intestinal adenocarcinomas. To investigate the effects of MSH2 deficiency in normal tissues, mice containing a retrievable transgenic lacI reporter gene for mutation detection were crossed with MSH2-/- mice. Mice homozygous for MSH2 deficiency revealed 4.8, 11.0 and 15.2-fold elevations in spontaneous mutation frequency in DNA obtained from brain, small intestine, and thymus, respectively, as compared to heterozygous or wild-type mice. Mutations most frequently recovered from MSH2-/- mice were single base substitutions (77%), particularly base transitions (64%). Frameshifts occurred less frequently (19%) and fell within very short (3-5 bp) mononucleotide runs. Thus the number of key growth control genes potentially impacted by MMR deficiency extends beyond those containing repetitive sequences. These results highlight the capacity for MSH2 deficiency to serve as a potent driving force during the multi-step evolution of tumors.
Animals↗
Mutational spectrum of the TSC1 gene in a cohort of 225 tuberous sclerosis complex patients: no evidence for genotype-phenotype correlation.
Tuberous sclerosis complex is an inherited tumour suppressor syndrome, caused by a mutation in either the TSC1 or TSC2 gene. The disease is characterised by a broad phenotypic spectrum that can include seizures, mental retardation, renal dysfunction, and dermatological abnormalities. The TSC1 gene was recently identified and has 23 exons, spanning 45 kb of genomic DNA, and encoding an 8.6 kb mRNA. After screening all 21 coding exons in our collection of 225 unrelated patients, only 29 small mutations were detected, suggesting that TSC1 mutations are under-represented among TSC patients. Almost all TSC1 mutations were small changes leading to a truncated protein, except for a splice site mutation and two in frame deletions in exon 7 and exon 15. No clear difference was observed in the clinical phenotype of patients with an in frame deletion or a frameshift or nonsense mutation. We found the disease causing mutation in 13% of our unrelated set of TSC patients, with more than half of the mutations clustered in exons 15 and 17, and no obvious under-representation of mutations among sporadic cases. In conclusion, we find no support for a genotype-phenotype correlation for the group of TSC1 patients compared to the overall population of TSC patients.
Adolescent↗
The mutation spectrum of the facilitative glucose transporter gene SLC2A2 (GLUT2) in patients with Fanconi-Bickel syndrome.
We report a total of 23 novel mutations of the SLC2A2 ( GLUT2) gene in 49 patients with a clinical diagnosis of Fanconi-Bickel syndrome (FBS). Molecular genetic analysis has now been performed in more than 50% of the 109 FBS cases from 88 families that we have been able to locate world-wide since the original report in 1949. In these 49 patients, 33 different SLC2A2 mutations (9 missense, 7 nonsense, 10 frameshift, 7 splice-site) have been detected. Thus, our results confirm that mutations of SLC2A2 are the basic defect in patients with FBS. Mutations of SLC2A2 were detected in historical FBS patients in whom some of the characteristic clinical features (hepatorenal glycogen accumulation, glucose and galactose intolerance, fasting hypoglycemia, a characteristic tubular nephropathy) and the effect of therapy were described for the first time. Mutations were also found in patients with atypical clinical signs such as intestinal malabsorption, failure to thrive, the absence of hepatomegaly, or renal hyperfiltration. No single prevalent SLC2A2 mutation was responsible for a significant number of cases. In a high percentage (74%) of FBS patients, the mutation is homozygous, so we conclude that the prevalence of SLC2A2 mutations is relatively low in most populations. No mutational hot spots within SLC2A2 or even within homologous sequences among the genes for facilitative glucose transporters were detected.
Alternative Splicing↗
Implications of p53 mutation spectrum for cancer etiology in gastric cancers of various histologic types from a high-risk area of central Italy.
Examination of p53 mutation spectra may provide clues to molecular mechanisms involved in different histologic types of gastric cancer. A total of 105 gastric cancer cases classified according to the Laurén's system were selected from a high-risk area around Florence, Italy. Exons 5-8 of the p53 gene were examined for mutations by the polymerase chain reaction-single strand conformation polymorphism technique and DNA sequencing, using DNA from formalin-fixed paraffin-embedded tissues. Mutation frequency was similar in intestinal-type (12/28) and unclassified tumors (9/18), but was significantly lower in diffuse cancers (12/57, P < 0.05). A similar frequency of p53 mutations was observed among tumor stages in both intestinal-type and unclassified cancers, but in diffuse tumors mutations tended to be associated with invasion beyond the muscularis propria. When base changes were considered, G:C-->A:T transitions at CpG sites were the most common mutations for all the three tumor types with 6 of 11 (55%) in intestinal type, 8 of 12 (67%) in diffuse type, and 5 of 8 (63 %) in unclassified tumors. Frequent p53 mutations in both intestinal-type and unclassified tumors support the hypothesis that unclassified tumors represent variants of the intestinal type and suggest that unclassified tumors, like the intestinal type, may also associate with environmental exposures. The predominance of G:C-->A:T transitions at CpG sites, which are associated with methyltransferase-induced DNA methylation at carbon 5 of cytosine, in all three tumor types suggests that the status of DNA methylation may be the major determinant for p53 mutations and may be also equally important in gastric carcinogenesis regardless of histology.
Adult↗
Mutational spectrum of COH1 and clinical heterogeneity in Cohen syndrome.
Cohen syndrome (CS) is an autosomal recessive disorder with variability in the clinical manifestations, characterised by mental retardation, postnatal microcephaly, facial dysmorphism, pigmentary retinopathy, myopia, and intermittent neutropenia. Mutations in the gene COH1 have been found in an ethnically diverse series of patients. Brief clinical descriptions of 24 patients with CS are provided. The patients were from 16 families of different ethnic backgrounds and between 2.5 and 60 years of age at assessment. DNA samples from all patients were analysed for mutations in COH1 by direct sequencing. Splice site mutations were characterised using reverse transcriptase PCR analysis from total RNA samples. In this series, we detected 25 different COH1 mutations; 19 of these were novel, including 9 nonsense mutations, 8 frameshift mutations, 4 verified splice site mutations, 3 larger in frame deletions, and 1 missense mutation. We observed marked variability of developmental and growth parameters. The typical facial gestalt was seen in 23/24 patients. Early onset progressive myopia was present in all the patients older than 5 years. Widespread pigmentary retinopathy was found in 12/14 patients assessed over 5 years of age. We present evidence for extended allelic heterogeneity of CS, with the vast majority of mutations leading to premature termination codons in COH1. Our data confirm the broad clinical spectrum of CS with some patients lacking even the characteristic facial gestalt and pigmentary retinopathy at school age.
Abnormalities, Multiple↗