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PubMed2003

Gene mutations in advanced colonic polyps: potential marker selection for stool-based mutated human DNA assays for colon cancer screening.

The detection and removal of advanced colonic polyps (ACPs) can help prevent the development of colorectal cancer. A set of DNA mutations known to be associated with colorectal carcinoma was tested against resected ACPs to determine the set s potential utility as a marker panel for ACPs. A sensitive mutation marker panel could be used by stool-based assays that look for mutated human DNA to detect the presence of ACPs. DNA from 32 ACPs = 1.0 cm in diameter was amplified and tested for 19 colorectal cancer associated DNA mutations and for deletions in BAT-26 (microsatellite instability). One or more mutations were identified by microsequencing in 28 of the 32 ACPs (88%). Mutations were identified in k-ras (59%), APC (33%), and p53 (22%). BAT-26 mutation, a marker for microsatellite instability, was not identified. Stool DNA based assays that can identify these mutations may significantly increase the identification of patients with potentially premalignant ACPs for evaluation and treatment by colonoscopy.

Adult↗
PubMed1999

Strong similarities of the FMR1 mutation in multiple tissues: postmortem studies of a male with a full mutation and a male carrier of a premutation.

Studies of the FMR1 mutation in multiple tissues are important to further our understanding of CGG repeat expansion in development and of the frequency and possible clinical significance of inter-tissue heterogeneity in fragile X syndrome. With some exceptions, most cases reported have shown strong similarity of the mutation size and methylation status between tissues. However, there have been only a few studies of multiple tissues including regions of the brain. We report on two postmortem studies of multiple tissues, one of a male with a full mutation (fully methylated) and one of a male carrier of a premutation. The male with the full mutation (TH) had a typical presentation of fragile X syndrome, including mild mental retardation. He had a methylated full mutation of two predominant sizes in all 12 tissues analyzed, including three regions of the brain. The male carrier of a premutation (GC) was clinically unaffected, and the mutation was the same size in all 14 tissues examined including seven regions of the brain. Therefore, both cases demonstrated lack of inter-tissue heterogeneity, suggesting strong somatic stability after the period of expansion to the observed mutation size(s). Also, both cases showed consistency between clinical phenotype and mutation characteristics in the brain.

Adult↗
PubMed1999

[Detection of R277Q mutation of SRD5alpha2 gene by amplification refractory mutation system].

OBJECTIVE: To set up a simple method for identifying the mutation of R227Q of SRD5alpha2 gene which is one of the most common mutations in congenital hypospadias in China. METHODS: The amplification refractory mutation system(ARMS) was employed in detecting the SRD5alpha2 gene R227Q mutation in congenital hypospadias confirmed by PCR-SSCP and DNA sequencing. RESULTS: The ARMS was successfully applied to the detection of the R227Q mutation of SRD5alpha2 gene. Three out of 23 congenital hypospadias were positive for R227Q mutation. The mutations determined by ARMS were in full agreement with those obtained by the DNA sequencing. CONCLUSION: This is a simple, rapid and accurate method. It can be used for detecting the SRD5alpha2 gene R227Q mutation in congenital hypospadias and male pseudohermaphroditism.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed2000

Factor V Leiden mutation, prothrombin gene mutation, and deficiencies in coagulation inhibitors associated with Budd-Chiari syndrome and portal vein thrombosis: results of a case-control study.

In a collaborative multicenter case-control study, we investigated the effect of factor V Leiden mutation, prothrombin gene mutation, and inherited deficiencies of protein C, protein S, and antithrombin on the risk of Budd-Chiari syndrome (BCS) and portal vein thrombosis (PVT). We compared 43 BCS patients and 92 PVT patients with 474 population-based controls. The relative risk of BCS was 11.3 (95% CI 4.8-26.5) for individuals with factor V Leiden mutation, 2.1(95% CI 0.4-9.6) for those with prothrombin gene mutation, and 6.8 (95% CI 1.9-24.4) for those with protein C deficiency. The relative risk of PVT was 2.7 (95% CI 1.1-6.9) for individuals with factor V Leiden mutation, 1.4 (95% CI 0.4-5.2) for those with prothrombin gene mutation, and 4.6 (95% CI 1.5-14.1) for those with protein C deficiency. The relative risk of BCS or PVT was not increased in the presence of inherited protein S or antithrombin deficiency. Concurrence of either acquired or inherited thrombotic risk factors was observed in 26% of the BCS patients and 37% of the PVT patients. We conclude that factor V Leiden mutation and hereditary protein C deficiency appear to be important risk factors for BCS and PVT. Although the prevalence of the prothrombin gene mutation was increased, it was not found to be a significant risk factor for BCS and PVT. The coexistence of thrombogenic risk factors in many patients indicates that BCS and PVT can be the result of a combined effect of different pathogenetic mechanisms.

Adult↗
PubMed2001

Double-gradient denaturing gradient gel electrophoresis assay for identification of L-ferritin iron-responsive element mutations responsible for hereditary hyperferritinemia-cataract syndrome: identification of the new mutation C14G.

BACKGROUND: Hereditary hyperferritinemia-cataract syndrome is an autosomic dominant disorder caused by heterogeneous mutations on the iron-responsive element (IRE) of ferritin L-chain mRNA. The mutations described to date were identified by direct sequencing of DNA from probands with hyperferritinemia often associated to bilateral cataracts. A direct genetic approach on a large population is useful to recognize polymorphisms in the DNA region and the prevalence of mutations associated with minor increases in serum ferritin and subclinical cataracts. We developed a rapid DNA scanning technique to detect mutations in a single electrophoretic analysis. METHODS: The double-gradient denaturing gradient gel electrophoresis (DG-DGGE) method consisted of PCR amplification of the target genomic DNA with GC-clamped oligonucleotides. The sequence encoded the 5' untranslated flanking region of ferritin L-chain mRNA, which includes an IRE stem-loop structure. The product was subjected to DG-DGGE (8.5-15% polyacrylamide and 50-95% denaturant) to separate the homo- and heteroduplexes. RESULTS: The method clearly identified all eight accessible mutations, including C-G transversions, which are the most difficult to detect. The method was applied to scan DNA samples from 50 healthy subjects and from 230 subjects with serum ferritin >400 microg/L. The new mutation G14C was identified. CONCLUSIONS: The DG-DGGE method detects all the mutations in the L-ferritin IRE sequence, is rapid and economical, and can be applied to scan large populations. The first population study indicated that the mutations are rare and may involve regions of the IRE structure not yet characterized.

Base Sequence↗
PubMed1992

DNA mutation associated with the human butyrylcholinesterase K-variant and its linkage to the atypical variant mutation and other polymorphic sites.

Genomic DNA from two families exhibiting the K-variant phenotype of serum butyrylcholinesterase was amplified by PCR and sequenced to determine the molecular basis of this variant. The K-variant phenotype was found to be associated with a DNA transition from guanine to adenine at nucleotide 1615, which caused an amino acid change from alanine 539 to threonine (GCA----ACA; Ala539----Thr). There was a 30% reduction of serum butyrylcholinesterase activity associated with this mutation. Amplification and sequencing of DNA from a random sample of 47 unrelated people gave a frequency of .128 for the K-variant allele. Thus, 1 person in 63 should be homozygous for the K-variant, making the K-variant the most common butyrylcholinesterase variant. The K-variant mutation was also found to be present in 17 (89%) of 19 butyrylcholinesterase genes containing the point mutation which causes the atypical phenotype of butyrylcholinesterase (GAT----GGT; Asp70----Gly). The presence of the K-variant in the same molecule as the atypical variant does not contribute to the qualitative change in the atypical enzyme, but it most likely accounts for the approximately one-third reduction in Vmax of butyrylcholinesterase activity in atypical serum. Two additional point mutations located in noncoding regions of the gene were also observed to be in linkage disequilibrium with the K-variant mutation. As many as four different point mutations have been identified within a single butyrylcholinesterase gene. Inhibition tests of the enzyme in plasma are usually used to distinguish the K-variant from the usual enzyme when the former is present with the heterozygous atypical variant (AK phenotype vs. UA phenotype). Inhibition tests were performed on plasma enzyme from the four possible genotypic combinations of the heterozygous atypical mutation with or without the K-variant mutation on either allele; we found that the AK phenotype was caused by three genotypes (A/K, AK/K, and U/A) and that the UA phenotype was caused by two genotypes (U/A and U/AK).

Amino Acid Sequence↗
PubMed1992

Mutational activation of the N-ras oncogene assessed in primary clonogenic culture of acute myeloid leukemia (AML): implications for the role of N-ras mutation in AML pathogenesis.

The number of steps involved in the pathogenesis of acute myeloid leukemia (AML) is unclear. The initiating event would be expected to exist in all leukemic cells, but subsequent events may be subclonal. If several genetic events occur, they may cooperate within the same cell or be alternatively acquired by different subclones. These possibilities cannot be adequately analyzed in DNA prepared directly from patient specimens. In this study, N-ras mutations demonstrable in DNA prepared from peripheral blood of 10 patients with AML were examined in primary in vitro colonies (AML-colony-forming units [CFU]) grown from these patients. Both colonies containing the mutant gene and colonies containing normal allele only were obtained from each patient. The proportion of colonies containing no mutant allele varied among patients (5% to 57%). A subset of mutation containing colonies appeared to have lost the normal allele in nine of 10 AML cases analyzed. In the four cases with two N-ras mutations, the two mutations were found to exist in different subclones. In these cases, macroscopic colonies (AML-MCFU) were also obtained using an assay system designed to select for earlier clonogenic cells than in the AML-CFU assay. The N12cys mutation in AML10 was found in the CFU, but not in the MCFU, and the N12asp mutation in AML43 was found in the MCFU, but not in the CFU. These results suggest that N-ras mutation is a postinitiation event in AML that contributes to the outgrowth of more malignant subclones. Where two mutations are found in a case of AML, they appear to have been acquired by separate subclones, which may show different degrees of differentiation.

Base Sequence↗
PubMed1991

Molecular characterization of two galactosemia mutations: correlation of mutations with highly conserved domains in galactose-1-phosphate uridyl transferase.

Galactosemia is an autosomal recessive disorder of human galactose metabolism caused by deficiency of the enzyme galactose-1-phosphate uridyl transferase (GALT). The molecular basis of this disorder is at present not well understood. We report here two missense mutations which result in low or undetectable enzymatic activity. First, we identified at nucleotide 591 a transition which substitutes glutamine 188 by arginine. The mutated glutamine is not only highly conserved in evolution (conserved also in Escherichia coli and Saccharomyces cerevisiae), but is also two amino acid residues downstream from the active site histidine-proline-histidine triad and results in about 10% of normal enzymatic activity. The arginine 188 mutation is the most common galactosemia mutation characterized to date. It accounts for one-fourth of the galactosemia alleles studied. Second, we report the substitution of arginine 333 by tryptophan, caused by a transition at nucleotide 1025. The area surrounding this missense mutation is the most highly conserved domain in the homologous enzymes from E. coli, yeast, and humans, and this mutation results in undetectable enzymatic activity, suggesting that this is a severe mutation. This second mutation appears to be rare, since it was found only in the patient we sequenced. Our data provide further evidence for the heterogeneity of galactosemia at the molecular level, heterogeneity which might be related to the variable clinical outcome observed in this disorder.

Amino Acid Sequence↗
PubMed1991

Mutations induced by ionizing radiation in a plasmid replicated in human cells. II. Sequence analysis of alpha-particle-induced point mutations.

The human shuttle plasmid pZ189, containing the Escherichia coli supF gene as the mutational target, was irradiated in vitro with 210Po alpha particles and transfected into human lymphoblastoid cells. Plasmids which were replicated in human cells were recovered and those containing mutant supF genes were isolated by phenotypic screening in E. coli. The mutations were characterized by sequencing the tRNA gene. The mutant frequency increased linearly with the alpha-particle dose and, at 259 Gy, it was 16 times (0.29%) that observed in unirradiated controls (0.018%). The distribution of alpha-particle-induced point mutations was highly nonrandom and similar to that observed in the unirradiated or X-irradiated plasmid DNAs. The majority of the mutations were G.C----A.T transitions and occurred selectively at most 5'-TC (3'-AG) and 5'-CC (3'-GG) sequences. For the unirradiated control DNA, these mutations at C's (G's) were preferentially located in the nontranscribed strand, similar to the observation previously made for mutations in X-irradiated DNA. Such a strand bias was not observed for mutations in the alpha-particle-irradiated DNA. The data suggest that, although similar types of point mutations are induced in unirradiated, X-irradiated, and alpha-particle-irradiated DNAs, the mechanisms of their induction and the exact nature of the lesions involved may be quite different.

Alpha Particles↗
PubMed1990

The BALB/c secondary response to the Sb site of influenza virus hemagglutinin. Nonrandom silent mutation and unequal numbers of VH and Vk mutations.

We have determined the nucleotide sequences of the expressed VH and Vk genes from 13 secondary (2 degrees) hemagglutinin (HA) (Sb) specific hybridomas derived from a single mouse. These antibodies share an Id, H37-68 (68Id) that dominates the 2 degrees HA(Sb) response in this mouse, but is rare or absent from 2 degrees responses of other mice. We find that these antibodies derive from five clones. The H chains of these antibodies are encoded by a single VH gene joined to a variety of DH and JH genes. The length of complementarity-determining region (CDR) 3 and sequence of the D-J junction are restricted, suggesting selection on CDR3 of the H chain. The L chains are more diverse. In the presented examples, they are encoded by the Vk21C and Vk21E genes and a Vk9 gene, and are joined to Jk1, 2, or 4. Each antibody is extensively mutated. The nature and distribution of the mutations suggests that 68Id-producing cells have been selected by Ag, although there are differences regarding the domain (VH, Vk, or both) in which mutations were selected. The implications of these findings on the idiosyncratic nature of the 68Id antibody response to HA(Sb) are discussed. There are two unusual characteristics regarding somatic mutation in these hybridomas. Whereas the expressed VH and Vk21 genes appear to have accumulated mutations at a high rate (1 to 1.5 x 10(-3)/base pairs/division, the expressed Vk9 genes appear to have accumulated mutations at a 5 to 15-fold lower rate than the expressed VH genes in the same cells. There is also a surprisingly high number of parallel silent somatic mutations in the VH genes, of which all but one are clustered to a 28-bp region in framework region 2 and CDR 2-encoding segments. The probability that this could have occurred by a random mutational process is essentially zero.

Amino Acid Sequence↗
PubMed1988

Nonsense and missense mutations in hemophilia A: estimate of the relative mutation rate at CG dinucleotides.

Hemophilia A is an X-linked disease of coagulation caused by deficiency of factor VIII. Using cloned cDNA and synthetic oligonucleotide probes, we have now screened 240 patients and found CG-to-TG transitions in an exon in nine. We have previously reported four of these patients; and here we report the remaining five, all of whom were severely affected. In one patient a TaqI site was lost in exon 23, and in the other four it was lost in exon 24. The novel exon 23 mutation is a CG-to-TG substitution at the codon for amino acid residue 2166, producing a nonsense codon in place of the normal codon for arginine. Similarly, the exon 24 mutations are also generated by CG-to-TG transitions, either on the sense strand producing nonsense mutations or on the antisense strand producing missense mutations (Arg to Gln) at position 2228. The novel missense mutations are the first such mutations observed in association with severe hemophilia A. These results provide further evidence that recurrent mutations are not uncommon in hemophilia A, and they also allow us to estimate that the extent of hypermutability of CG dinucleotides is 10-20 times greater than the average mutation rate for hemophilia A.

Adolescent↗
PubMed1995

Mutations in the X-linked E1 alpha subunit of pyruvate dehydrogenase: exon skipping, insertion of duplicate sequence, and missense mutations leading to the deficiency of the pyruvate dehydrogenase complex.

Human pyruvate dehydrogenase (PDH)-complex deficiency is an inborn error of metabolism that is extremely heterogeneous in its presentation and clinical course. In a study of 14 patients (7 females and 7 males), we have found a mutation in the coding region of the E1 alpha gene in all 14 patients. Two female patients had the same 7-bp deletion at nt 927; another female patient had a 3-bp deletion at nt 931. Another female patient was found to have a deletion of exon 6 in her cDNA. Two other female patients were found to have insertions, one of 13 bp at nt 981 and one of 46 bp at nucleotide 1078. Two male patients were found to have a 4-bp insertion at nucleotide 1163. The remaining six patients all had missense mutations. A male patient and a female patient both had an A1133G mutation. The other missense mutations were C214T, C615A, and C787G (two patients). Five of these mutations are novel mutations, five have been previously reported in other patients, and two were published observations in other patients in an E1 alpha-mutation summary. In the four cases where parent DNA was available, only one mother was found to be a carrier of the same mutation as her child.

Base Sequence↗
PubMed1995

Novel inherited mutations and variable expressivity of BRCA1 alleles, including the founder mutation 185delAG in Ashkenazi Jewish families.

Thirty-seven families with four or more cases of breast cancer or breast and ovarian cancer were analyzed for mutations in BRCA1. Twelve different germ-line mutations, four novel and eight previously observed, were detected in 16 families. Five families of Ashkenazi Jewish descent carried the 185delAG mutation and shared the same haplotype at eight polymorphic markers spanning approximately 850 kb at BRCA1. Expressivity of 185delAG in these families varied, from early-onset breast cancer without ovarian cancer. Mutation 4184delTCAA occurred independently in two families. In one family, penetrance was complete, with females developing early-onset breast cancer or ovarian cancer and the male carrier developing prostatic cancer, whereas, in the other family, penetrance was incomplete and only breast cancer occurred, diagnosed at ages 38-81 years. Two novel nonsense mutations led to the loss of mutant BRCA1 transcript in families with 10 and 6 cases of early-onset breast cancer and ovarian cancer. A 665-nt segment of the BRCA1 3'-UTR and 1.3 kb of genomic sequence including the putative promoter region were invariant by single-strand conformation analysis in 13 families without coding-sequence mutations. Overall in our series, BRCA1 mutations have been detected in 26 families: 16 with positive BRCA1 lod scores, 7 with negative lod scores (reflecting multiple sporadic breast cancers), and 3 not tested for linkage. Three other families have positive lod scores for linkage to BRCA2, but 13 families without detected BRCA1 mutations have negative lod scores for both BRCA1 and BRCA2.

Alleles↗
PubMed1996

Germline and somatic mutations in an oncogene: RET mutations in inherited medullary thyroid carcinoma.

Inherited cancer syndromes predispose an individual to development of specific tumors. Somatic and germline mutations in the same tumor suppressor gene, as described in Knudson's two-mutation model, are well recognized. Inherited mutations in the RET proto-oncogene, which encodes a receptor tyrosine kinase, predispose individuals to the multiple endocrine neoplasia type 2 (MEN 2) cancer syndromes. The major component tumor of these syndromes is medullary thyroid carcinoma (MTC). To date, somatic mutations in RET have not been identified in tumors from individuals with MEN 2, although they have been well documented in sporadic MEN 2-related tumors. We have identified, among 16 MEN 2 cases with well-defined RET germline mutations, a somatic missense mutation at codon 918 of RET in 3 of 15 MTCs and in a sample with hyperplastic C-cells (presumed precursor to hereditary MTC). We suggest that the presence of a somatic mutation, in addition to the preexisting germline mutation in hereditary MTCs, may contribute to tumorigenesis in vivo.

Carcinoma, Medullary↗
PubMed1996

Two distinct origins of a common BRCA1 mutation in breast-ovarian cancer families: a genetic study of 15 185delAG-mutation kindreds.

We screened 163 women from breast-ovarian cancer-prone families, as well as 178 individuals affected with breast and/or ovarian cancer but unselected for family history, for germ-line mutations in exon 2 of BRCA1, by SSCP analysis and direct sequencing. A total of 25 mutations were detected. Thirteen of 64 Jewish Ashkenazi women and 2 non-Jewish individuals were found to possess the 185delAG mutation. Haplotype data for all 15 individuals, with markers intragenic to BRCA1, suggest that the Jewish Ashkenazi individuals share a common ancestry that is distinct from the lineage shared by the other two women. These data provide the first evidence of two distinct lines of transmission for the 185delAG mutation, only one of which has its origins in the Jewish Ashkenazi population. Our screening also uncovered 10 affected individuals with an 11-bp deletion at nucleotide 188 of BRCA1 (188del11), 4 of whom are Ashkenazi Jews. This is only the third reported mutation detected within the Jewish Ashkenazi population and may represent the second most common alteration in BRCA1 found in Ashkenazi Jews in the United States. The observed overrepresentation of specific mutations within a subgroup of the general population may eventually contribute to the development of inexpensive and routine tests for BRCA1 mutations, as well as to the elucidation of other contributory factors (e.g., diet, environment, and chemical exposures) that may play a key role in cancer initiation and development. The implications of the mutational data, as well as the role that founder effect, demographic history, and penetrance play in the resulting observed phenomena, are discussed.

Adult↗
PubMed1997

A recurrent laminin 5 mutation in British patients with lethal (Herlitz) junctional epidermolysis bullosa: evidence for a mutational hotspot rather than propagation of an ancestral allele.

The three genes (LAMA3, LAB3 and LAMC2) that encode the anchoring filament protein, laminin 5, may all harbour pathogenetic mutations in the autosomal recessive blistering skin disorder, junctional epidermolysis bullosa (JEB). Recently, one particular mutation, R635X in the LAMB3 gene, has been found to account for approximately 40% of all JEB laminin 5 mutations (Kivirikko et al., Hum Mol Genet 1996; 5: 231-7). In this study, we assessed the frequency of this mutation in 12 British patients with lethal (Herlitz) JEB using PCR amplification of genomic DNA and restriction endonuclease digestion. The mutation R635X was fond in seven of 24 (29%) mutant alleles, confirming its relative frequency within the British gene pool. In addition, haplotype analysis using intragenic polymorphisms showed that the mutation arose on at least four different haplotype backgrounds, suggesting it represents a mutational hotspot rather than propagation of a common British ancestral allele. These findings support the hypermutable nature of this CpG dinucleotide and have implications in screening for laminin 5 gene mutations in British and other patients with JEB.

Alleles↗
PubMed1999

A rapid screening for steroid 21-hydroxylase mutations in patients with congenital adrenal hyperplasia. Mutations in brief no. 247. Online.

Steroid 21-hydroxylase deficiency is the major cause of congenital adrenal hyperplasia (CAH). CAH due to 21-hydroxylase deficiency is divided into three classes: salt-wasting (classical), non-classical and simple virilizing, reflecting different degrees of clinical severity. Using polymerase chain reaction (PCR) and allele-specific oligonucleotide hybridisation (ASO), we screened the DNA of 62 Caucasian CAH families (heterozygous parents and children) for 14 different and frequently-found CYP21-mutations (HGMD). Of the 62 patients (21 males, 41 females), 26 females and 11 males had the classical or salt-wasting form, 3 females and 1 male had the non-classical form and 14 females and 7 males had simple virilizing CAH. More than 60% of the patients were compound-heterozygous. We found the mutations on 110 alleles (out of 124 alleles). There were 30 CYP21 gene deletions/conversions, 3 substitutions (P30L) in exon 1, 30 splice mutations (c.93-13A/C>G) in intron 2, 26 point mutations (I172N) in exon 4, one cluster of mutations (I236N, V237E, M239K) in exon 6, 8 mutations (V281L and 1760-1761insT) in exon 7, and 8 nonsense (Q318X) and 4 missense (R356W) mutations in exon 8. Our study supports the case for using this rapid technique for CAH-family screening as long as alleles from both affected patients and parents are screened in parallel.

Adrenal Hyperplasia, Congenital↗
PubMed2001

SOS mutator DNA polymerase IV functions in adaptive mutation and not adaptive amplification.

Adaptive point mutation and amplification are induced responses to environmental stress, promoting genetic changes that can enhance survival. A specialized adaptive mutation mechanism has been documented in one Escherichia coli assay, but its enzymatic basis remained unclear. We report that the SOS-inducible, error-prone DNA polymerase (pol) IV, encoded by dinB, is required for adaptive point mutation in the E. coli lac operon. A nonpolar dinB mutation reduces adaptive mutation frequencies by 85% but does not affect adaptive amplification, growth-dependent mutation, or survival after oxidative or UV damage. We show that pol IV, together with the major replicase, pol III, can account for all adaptive point mutations at lac. The results identify a role for pol IV in inducible genetic change.

Adaptation, Physiological↗