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At least 1,207 records · Page 67Linked to original sources
PubMed1997

Mutation analysis of the BRCA2 gene in breast/ovarian cancer Spanish families: identification of two new mutations.

The recently isolated gene BRCA2 is responsible for about 45% of familial breast cancer and the majority of male breast cancer families. We have screened 12 high risk breast/ovarian Spanish families for mutations in BRCA2, using SSCP followed by direct sequencing. We have found mutations in four of our 12 families (33.3%), including two with male breast cancer. Three of the mutations were frameshift and one was a missense. Two of the mutations have been previously published and two are new mutations.

Adult↗
PubMed2002

High-throughput screening for GJB2 mutations--its clinical application to genetic testing in prelingual deafness screening for GJB2 mutations.

OBJECTIVES: Mutations in connexin26 (GJB2) are one of the most frequent causes of prelingual hearing impairment. Several different types of one-base deletions in exon2 were the most common type of GJB2 mutation regardless of ethnicity, including 35delG in American-European populations, 235delC in Japanese population and 167delT in Ashkenazi Jewish population. Various types of one-base substitutions were also considered to be causative mutations of GJB2 associated hearing impairment. This article describes a rapid and high-throughput screening procedure for the detection of one-base deletion/substitution in GJB2 with less invasive sampling procedure in the implication for the clinical application. METHODS: 53 hearing-impaired children and 50 healthy controls were admitted to take part in this study program. DNA samples obtained from buccal swab were used to amplify the exon2 of GJB2, and single run with an automated sequencer was used to identify the one-base deletion. Single-base substitutions were also screened by primer-extension procedure with dye terminators. The presence of both types of mutations was confirmed by direct sequence of the GJB2 exon2. RESULTS: Two of 50 controls (4%) included one-base deletion in GJB2 as heterozygote. 14 of 53 hearing impaired cases (26.4%) contained deletion in GJB2 either as homozygote (five cases) or heterozygote (nine cases) form. Sequencing analysis of whole exon2 of GJB2 identified all these deletions as 235delC. Primer-extension analysis revealed additional mutations with single base substitutions in three cases with compound heterozygote with 235delC. CONCLUSIONS: Rapid screening procedure of GJB2 can be potentially useful for the identification of prelingual deafness.

Chromosome Deletion↗
PubMed2002

Atypical muscle pathology and a survey of cis-mutations in deaf patients harboring a 1555 A-to-G point mutation in the mitochondrial ribosomal RNA gene.

We investigated three families with maternally inherited deafness associated with a 1555 A-to-G substitution in the 12S ribosomal RNA gene. Probands in these families developed deafness following streptomycin treatment, whereas several family members who did not receive aminoglycoside showed onset of deafness in middle age. One proband had a non-synonymous A14062G mutation in the ND5 gene and the other had a non-synonymous G15221A mutation in the cytochrome b gene and a T1391C mutation in the 12S ribosomal RNA gene, whose importance in disease expression remains to be clarified. Two muscle biopsies from the patients with and without streptomycin treatment, showed similar findings; a moth-eaten appearance with decreased cytochrome c oxidase activity and abnormal mitochondrial morphology. These findings suggest that even without exposure to aminoglycoside the A1555G mutation may impair mitochondrial function and that the mitochondrial abnormalities associated with the A1555G mutation may be expressed in tissues other than those of the auditory system.

Adult↗
PubMed1992

Missense glucokinase mutation in maturity-onset diabetes of the young and mutation screening in late-onset diabetes.

We describe a codon 299 mutation in the glucokinase gene in a British pedigree with maturity-onset diabetes of the young (MODY) resulting in a substitution of glycine to arginine. One out of fifty patients diagnosed with classical late-onset type 2 diabetes mellitus was also found to have this mutation. All nine relatives of this patient who have inherited the mutation have type 2 diabetes, although six others without the mutation are also present with diabetes. The discovery that glucokinase mutations can cause MODY and was also found in ten affected members of a pedigree with type 2 diabetes in which MODY had not previously been considered indicates that diagnosis based on molecular pathology will be helpful in understanding the aetiology of type 2 diabetes.

Adolescent↗
PubMed2002

Mutations in coagulation factor XIII A gene in three Turkish patients: two novel mutations and a known insertion.

Molecular analysis of factor XIII A gene on three unrelated Turkish families identified two novel and one known mutations. One novel mutation is a substitution of cytidine by guanine at codon 541 in exon 12, beta barrel 1 domain of the coagulation factor XIII A subunit gene resulting in the conversion of asparagine to lysine. The mutation alters the restriction site of the enzyme MboII. The second novel mutation, a 4 bp (-CAAA) deletion located in a direct repetitive sequence (CAAACAAA) between codons 466-469, results in premature termination of translation at codon 474. The third mutation is a previously reported single nucleotide (cytidine) insertion at codon 400 in exon 9 of the factor XIII gene.

Child↗
PubMed2006

Mutation and genomic deletion status of ataxia telangiectasia mutated (ATM) and p53 confer specific gene expression profiles in mantle cell lymphoma.

Although mantle cell lymphoma (MCL) frequently harbors inactivated ataxia telangiectasia mutated (ATM) and p53 alleles, little is known about the molecular phenotypes caused by these genetic changes. We identified point mutations and genomic deletions in these genes in a series of cyclin D1-positive MCL cases and correlated genotype with gene expression profiles and overall survival. Mutated and/or deleted ATM and p53 alleles were found in 56% (40/72) and 26% (21/82) of the cases examined, respectively. Although MCL patients with inactive p53 alleles showed a significant reduction in median overall survival, aberrant ATM status did not predict for survival. Nevertheless, specific gene expression signatures indicative of the mutation and genomic deletion status of each gene were identified that were different from wild-type cases. These signatures were comprised of a select group of genes related to apoptosis, stress responses, and cell cycle regulation that are relevant to ATM or p53 function. Importantly, we found the molecular signatures are different between cases with mutations and deletions, because the latter are characterized by loss of genes colocalized in the same chromosome region of ATM or p53. This information on molecular phenotypes may provide new areas of investigation for ATM function or may be exploited by designing specific therapies for MCL cases with p53 aberrations.

Apoptosis↗
PubMed2006

Genetic heterogeneity of granulocytes for the JAK2 V617F mutation in essential thrombocythaemia: implications for mutation detection in peripheral blood.

AIMS: The molecular pathogenesis of essential thrombocythaemia (ET) is heterogeneous. We aimed to determine the relative sensitivity of four separate molecular assays used to detect the presence of the JAK2 V617F mutation in peripheral blood from patients with essential thrombocythaemia and related myeloproliferative disorders. METHODS: Purified granulocytes from 60 patients were analysed for the presence of the JAK2 V617F mutation by direct sequencing, denaturing high-performance liquid chromatography (DHPLC), allele-specific polymerase chain reaction (PCR) and allele-specific enrichment. Clinical data were collected for all patients and correlated with assay results. RESULTS: Direct sequencing and DHPLC were relatively insensitive assays for mutation detection, together identifying only 53% of the JAK2 V617F positive cases of ET. Allele-specific PCR and allele-specific enrichment were significantly more sensitive assays and were able to identify additional ET patients that were positive for the JAK2 V617F mutation in only a minority of circulating granulocytes. Enrichment for the mutation was demonstrated in blood platelets from two of these patients. CONCLUSIONS: The observed biological difference in circulating granulocyte involvement by the JAK2 V617F clone necessitates a sensitive molecular assay for the diagnostic investigation of thrombocytosis.

Adult↗
PubMed1997

Characterization of alpha1(IV) collagen mutations in Caenorhabditis elegans and the effects of alpha1 and alpha2(IV) mutations on type IV collagen distribution.

Type IV collagen is a major component of basement membranes. We have characterized 11 mutations in emb-9, the alpha1(IV) collagen gene of Caenorhabditis elegans, that result in a spectrum of phenotypes. Five are substitutions of glycines in the Gly-X-Y domain and cause semidominant, temperature-sensitive lethality at the twofold stage of embryogenesis. One is a glycine substitution that causes recessive, non-temperature-sensitive larval lethality. Three putative null alleles, two nonsense mutations and a deletion, all cause recessive, non-temperature-sensitive lethality at the threefold stage of embryogenesis. The less severe null phenotype indicates that glycine substitution containing mutant chains dominantly interfere with the function of other molecules. The emb-9 null mutants do not stain with anti-EMB-9 antisera and show intracellular accumulation of the alpha2(IV) chain, LET-2, indicating that LET-2 assembly and/or secretion requires EMB-9. Glycine substitutions in either EMB-9 or LET-2 cause intracellular accumulation of both chains. The degree of intracellular accumulation differs depending on the allele and temperature and correlates with the severity of the phenotype. Temperature sensitivity appears to result from reduced assembly/secretion of type IV collagen, not defective function in the basement membrane. Because the dominant interference of glycine substitution mutations is maximal when type IV collagen secretion is totally blocked, this interference appears to occur intracellularly, rather than in the basement membrane. We suggest that the nature of dominant interference caused by mutations in type IV collagen is different than that caused by mutations in fibrillar collagens.

Alleles↗
PubMed1999

Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes.

Stickler and Marshall syndromes are dominantly inherited chondrodysplasias characterized by midfacial hypoplasia, high myopia, and sensorineural-hearing deficit. Since the characteristics of these syndromes overlap, it has been argued whether they are distinct entities or different manifestations of a single syndrome. Several mutations causing Stickler syndrome have been found in the COL2A1 gene, and one mutation causing Stickler syndrome and one causing Marshall syndrome have been detected in the COL11A1 gene. We characterize here the genomic structure of the COL11A1 gene. Screening of patients with Stickler, Stickler-like, or Marshall syndrome pointed to 23 novel mutations. Genotypic-phenotypic comparison revealed an association between the Marshall syndrome phenotype and splicing mutations of 54-bp exons in the C-terminal region of the COL11A1 gene. Null-allele mutations in the COL2A1 gene led to a typical phenotype of Stickler syndrome. Some patients, however, presented with phenotypes of both Marshall and Stickler syndromes.

Abnormalities, Multiple↗
PubMed2000

Delineation of the spectrum of Wilson disease mutations in the Greek population and the identification of six novel mutations.

In this study, we report the further results of an ongoing project on the delineation of the spectrum of mutations on the ATP7B gene in Wilson disease (WD) patients of Greek origin. We have analyzed 24 additional families and detected 16 mutations (five frameshifts, two splice site, two nonsense, and seven missense), of which six are novel. On adding these results to the ones already published by us, we conclude that WD shows a marked allelic heterogeneity in the Greek population. Of the total number of mutations so far detected, the most common eight account for the molecular defect in 72.8% of the WD chromosomes. The most frequent mutation is the His0169Gln, which has a frequency of 28.5%, similar to those reported in North European populations. Using these data, an efficient strategy of mutation screening for WD is possible in this population, thus improving the possibility of preclinical diagnosis.

Adenosine Triphosphatases↗
PubMedDate not supplied

Mutation analysis and genetic service: the construction and use of national confidential databases of mutations and pedigrees.

The development of rapid mutation screening procedures allows the detection of mutations in large populations. This is particularly useful for inherited diseases of high mutational heterogeneity, such as haemophilia A and B, because the analysis of the very many different natural mutants clearly defines the features that are important to the function of the relevant gene and gene product. Furthermore, the characterization of the mutation in an index person from each affected family may lead to the construction of confidential databases of mutations and pedigrees that allow optimization of genetic service. We report how, motivated by the aforementioned concepts, we have planned and introduced in the UK a national strategy to optimize genetic service in both haemophilias and, in particular, we describe the principles that have guided us.

DNA Mutational Analysis↗
PubMed1994

Mutation analysis of the Bruton's tyrosine kinase gene in X-linked agammaglobulinemia: identification of a mutation which affects the same codon as is altered in immunodeficient xid mice.

X-linked agammaglobulinemia (XLA) is an inherited immunodeficiency disease in man, reflecting an arrest in differentiation of pre-B cells to mature B cell stages. The gene defective in XLA has been identified as a cytoplasmic protein tyrosine kinase, named btk (Bruton's tyrosine kinase). Here we report the characterization of mutations in the btk gene of five unrelated XLA families. Amplified products were generated from cDNA, cloned and sequenced. Three single point mutations and two small insertions were identified. One of the point mutations and the two insertions created stop codons that would lead to truncated btk proteins. In one XLA patient we found a single basepair substitution that altered the highly conserved Arg288 within the SH2 domain and would therefore abrogate interactions with substrate phosphotyrosines. In another XLA patient a single basepair substitution was observed that altered the conserved Arg28 residue in the N-terminal unique region of unknown function. This residue is also mutated in the xid mouse, which has a different, less severe, B cell deficiency. We conclude that a similar mutation in the btk gene leads in man to an almost complete arrest at an early stage of B cell differentiation, but in the mouse to only limited B cell abnormalities.

Agammaglobulinaemia Tyrosine Kinase↗
PubMedDate not supplied

Use of MALDI-TOF mass spectrometry in a 51-mutation test for cystic fibrosis: evidence that 3199del6 is a disease-causing mutation.

PURPOSE: We developed a 51-mutation extended cystic fibrosis (CF) panel that incorporates the 25 previously recommended CFTR mutations, plus 26 additional mutations including 3199del6, which was associated with I148T. METHODS: This assay utilizes an integrated matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry system. RESULTS: CF testing was performed on over 5,000 individuals, including a 3-year-old Hispanic-American patient with a compound heterozygous G542X/3199del6 genotype. He is negative for I148T, or other mutations assessed by CFTR gene sequencing. CONCLUSION: These results demonstrate the successful implementation of MALDI-TOF mass spectrometry in CF clinical testing, and establish 3199del6 as a disease-causing CF mutation.

Child, Preschool↗
PubMed2006

Dominant dystrophic epidermolysis bullosa caused by a novel G2037R mutation and by a known G2028R mutation in the type VII collagen gene (COL7A1).

An autosomal dystrophic epidermolysis bullosa (DDEB) is a hereditary mechanobullous disease characterized by blistering of the skin and the mucous membrane. DDEB is caused by a heterozygous mutation in the COL7A1 gene encoding type VII collagen, the major component of anchoring fibrils, and phenotypically classified into several types. We experienced two boys with DDEB and examined the mutation analyses of the COL7A1 genes of the two patients and their fathers to clarify the relationship between the genotypes and phenotypes, that is, the mutation sites of COL7A1 gene and the clinical types of DDEB. The case 1 and 2 patients and their fathers revealed a heterozygous nucleotide G to A transition at position 6109 and 6082 in 73 exon of COL7A1, which resulted in a glycine to arginine substitution (G2037R and G2028R), respectively. G2037R found in the case 1 patient was a novel mutation. There was no clear relationship recognized between the two mutation sites in the COL7A1 gene and the clinical variations.

Arginine↗
PubMed1999

Two germline missense mutations at codons 804 and 806 of the RET proto-oncogene in the same allele in a patient with multiple endocrine neoplasia type 2B without codon 918 mutation.

Multiple endocrine neoplasia (MEN) type 2B is a clinically distinct entity among the autosomal dominant MEN 2 syndromes. Most patients with MEN 2B carry a germline mutation (M918T) of the RET proto-oncogene, while a few carry A883F. We examined a patient with MEN 2B, but without M918T or A883F, and her relatives. Here, we report the presence in this patient of 2 germline mutations, V804M and Y806C in the same allele. While the novel Y806C was inherited from her father, its carriers (her father and brother) was not affected by MEN 2. In contrast, V804M was a de novo mutation, that has been reported in patients with familial medullary thyroid carcinoma. Combinations of mutations of the RET proto-oncogene may cause oncogenic activities different from those of single mutations.

Base Sequence↗
PubMed1997

Somatic frameshift mutations in the BAX gene in colon cancers of the microsatellite mutator phenotype.

Cancers of the microsatellite mutator phenotype (MMP) show exaggerated genomic instability at simple repeat sequences. More than 50 percent (21 out of 41) of human MMP+ colon adenocarcinomas examined were found to have frameshift mutations in a tract of eight deoxyguanosines [(G)8] within BAX, a gene that promotes apoptosis. These mutations were absent in MMP- tumors and were significantly less frequent in (G)8 repeats from other genes. Frameshift mutations were present in both BAX alleles in some MMP+ colon tumor cell lines and in primary tumors. These results suggest that inactivating BAX mutations are selected for during the progression of colorectal MMP+ tumors and that the wild-type BAX gene plays a suppressor role in a p53-independent pathway for colorectal carcinogenesis.

Adenocarcinoma↗
PubMed1991

Multiple dispersed spontaneous mutations: a novel pathway of mutation in a malignant human cell line.

We analyzed the nature of spontaneous mutations at the autosomal locus coding for adenine phosphoribosyltransferase in the human colorectal carcinoma cell line SW620 to establish whether distinctive mutational pathways exist that might underlie the more complex genome rearrangements arising in tumor cells. Point mutations occur at a low rate in aprt hemizygotes derived from SW620, largely as a result of base substitutions at G.C base pairs to yield transversions and transitions. However, a novel pathway is evident in the form of multiple dispersed mutations in which two errors, separated by as much as 1,800 bp, fall in the same mutant gene. Such mutations could be the result of error-prone DNA synthesis occurring during normal replication or during long-patch excision-repair of spontaneously arising DNA lesions. This process could also contribute to the chromosomal instability evident in these tumor cells.

Adenine Phosphoribosyltransferase↗
PubMed1997

Mutation and haplotype analysis of phenylalanine hydroxylase alleles in classical PKU patients from the Czech Republic: identification of four novel mutations.

Mutations, haplotypes, and other polymorphic markers in the phenylalanine hydroxylase (PAH) gene were analysed in 133 unrelated Czech families with classical phenylketonuria (PKU). Almost 95% of all mutant alleles were identified, using a combination of PCR and restriction analysis, denaturing gradient gel electrophoresis (DGGE), and sequencing. A total of 30 different mutations, 16 various RFLP/VNTR haplotypes, and four polymorphisms were detected on 266 independent mutant chromosomes. The most common molecular defect observed in the Czech population was R408W (54.9%). Each of the other 29 mutations was present in no more than 5% of alleles and 13 mutations were found in only one PKU allele each (0.4%). Four novel mutations G239A, R270fsdel5bp, A342P, and IVS11nt-8g-->a were identified. In 14 (5.1%) alleles, linked to four different RFLP/VNTR haplotypes, the sequence alterations still remain unknown. Our results confirm that PKU is a heterogeneous disorder at the molecular level. Since there is evidence for the gene flow coming from northern, western, and southern parts of Europe into our Slavic population, it is clear that human migration has been the most important factor in the spread of PKU alleles in Europe.

Alleles↗