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PubMed2004

CD4(+) T-cell recognition of mutated B-RAF in melanoma patients harboring the V599E mutation.

The potential of antigen-directed cancer immunotherapy has not been fully realized, perhaps because many commonly targeted tumor associated proteins are not essential to maintaining the malignant cell phenotype. A constitutively activating mutation in the signaling molecule BRAF is expressed frequently in melanomas and may play an important role in the biology of this disease. A 29-mer B-Raf peptide incorporating the V599E mutation was used for in vitro stimulation of lymphocytes derived from melanoma patients, generating MHC class II-restricted CD4(+) T cells specific for this peptide as well as for melanoma cells expressing B-Raf V599E. Mutated B-Raf exemplifies targets that may be ideal for immunotherapy.

Alleles↗
PubMed1995

Complete spectrum of PAH mutations in Tataria: presence of Slavic, Turkic and Scandinavian mutations.

Phenylketonuria (PKU) is an autosomal recessive disorder associated with a deficiency of hepatic phenylalanine hydroxylase (PAH). Although the molecular lesions present in the PAH genes of PKU patients have previously been determined in several Slavic populations, little is known regarding the molecular basis of PKU in the non-Slavic populations of the former Soviet Union. Guthrie card samples from twenty-one classical PKU patients residing in the Tatarian Republic were examined by a combination of denaturing gradient gel electrophoresis and direct sequence analysis. Twelve patients were of Tatarian ancestry, five were of Russian ancestry, and four were of mixed Tatarian and Russian ancestry. Two of the Tatarian patients were related, sharing one mutant allele. The single major allele identified in this study was R408W/RFLP haplotype 2/VNTR 3, which was present on 11/14 or 78.6% of all mutant chromosomes of Slavic origin, but on only 10/27 or 37.0% of mutant chromosomes of Tatarian origin. This result suggests that this allele was introduced into central Asian populations during the eastward expansion of Slavs across the Eurasian landmass. A significant influence of Turkic peoples on Tatars can be inferred from the presence of R261Q. IVS10nt546g --> a, L48S, IVS2nt5g --> c and P281L, all of which are relatively common among Turks or have been observed in Mediterranean populations. Together, these alleles are present on 11/27 or 40.7% of all mutant chromosomes in ethnic Tatars. Surprisingly, the common Scandinavian mutation IVS12ntlg --> a was also present in Tataria, as was the delta agE221D222fs mutation found previously only in Denmark. Thus, some direct or indirect gene flow from Scandinavian into Tataria seems evident. Finally, the complete absence of PAH mutations previously observed in Oriental populations suggests that there was little gene flow into Tataria from Eastern Asia.

Alleles↗
PubMed1985

Mutational resistance as the mechanism of acquired drug resistance to aminoglycosides and antibacterial agents in Mycobacterium fortuitum and Mycobacterium chelonei. Evidence is based on plasmid analysis, mutational frequencies, and aminoglycoside-modifying enzyme assays.

Possible mechanisms of drug resistance of Mycobacterium fortuitum and Mycobacterium chelonei to antibacterial agents were investigated. Single-step mutational frequencies were low (generally less than or equal to 10(-7] for cefoxitin, doxycycline, erythromycin, and sulfamethoxazole and relatively high (10(-4) to 10(-7] for kanamycin and amikacin. Aminoglycoside-susceptible strains of both species contained an aminoglycoside acetyltransferase (3)-III or IV. No additional enzymes were seen with laboratory or clinically acquired aminoglycoside resistance. Plasmids of several sizes were present in some susceptible isolates of both species, but acquired resistance was not associated with a change in the apparent size or number of these plasmids. Isolates with acquired resistance to amikacin were resistant to the other 2-deoxystreptamine aminoglycosides but showed little or no change in minimal inhibitory concentrations to streptomycin, suggesting either a difference in cellular uptake between the 2 groups of drugs or, more likely, different binding sites on the ribosome. In 59 patients treated with 63 courses of therapy with a single agent for 1 month or longer, the development of resistance was observed only twice (3%). Both isolates had high mutational frequencies (10(-4) and 10(-5]. These studies support mutational resistance as the mechanism of acquired resistance to antibacterial agents in M. fortuitum and M. chelonei.

Adolescent↗
PubMed1997

Germline dinucleotide mutation in codon 883 of the RET proto-oncogene in multiple endocrine neoplasia type 2B without codon 918 mutation.

The autosomal dominant multiple endocrine neoplasia type 2 syndromes (MEN 2) comprise three clinically distinct entities, MEN 2A, familial medullary thyroid carcinoma and MEN 2B, which share a common clinical feature: medullary thyroid carcinoma (MTC). MEN 2B is considered to have the most aggressive form of MTC. Therefore, early detection of MEN 2B in order to prevent potentially lethal MTC is important. More than 95% of all MEN 2B cases are caused by germline mutation at codon 918 (M918T) in exon 16 of the RET proto-oncogene. In this study, we demonstrate the presence of germline codon 883 mutation (A883F) in 2 of 3 unrelated MEN 2B cases without codon 918 mutation. Our data demonstrate a novel etiologic event which may have roles in predisposition to MEN 2B when present in the germline and in the pathogenesis of sporadic MTC when somatic.

Alanine↗
PubMed2002

GNE mutations in an American family with quadriceps-sparing IBM and lack of mutations in s-IBM.

Analysis for GNE mutations was performed in an American, non-Iranian Jewish, family with quadriceps-sparing inclusion body myopathy (QS-IBM) and in 11 patients with sporadic IBM (s-IBM). Two novel nonallosteric site missense mutations were found in the QS-IBM kinship. No mutations were identified in s-IBM patients. After 8 years of follow-up and severe disease progression, the quadriceps muscle in the QS-IBM patient remains strong despite subclinical involvement documented with repeat MRI and muscle biopsy.

Adult↗
PubMed2003

Mutations in mákos, a Drosophila gene encoding the Cdc27 subunit of the anaphase promoting complex, enhance centrosomal defects in polo and are suppressed by mutations in twins/aar, which encodes a regulatory subunit of PP2A.

The gene mákos (mks) encodes the Drosophila counterpart of the Cdc27 subunit of the anaphase promoting complex (APC/C). Neuroblasts from third-larval-instar mks mutants arrest mitosis in a metaphase-like state but show some separation of sister chromatids. In contrast to metaphase-checkpoint-arrested cells, such mutant neuroblasts contain elevated levels not only of cyclin B but also of cyclin A. Mutations in mks enhance the reduced ability of hypomorphic polo mutant alleles to recruit and/or maintain the centrosomal antigens gamma-tubulin and CP190 at the spindle poles. Absence of the MPM2 epitope from the spindle poles in such double mutants suggests Polo kinase is not fully activated at this location. Thus, it appears that spindle pole functions of Polo kinase require the degradation of early mitotic targets of the APC/C, such as cyclin A, or other specific proteins. The metaphase-like arrest of mks mutants cannot be overcome by mutations in the spindle integrity checkpoint gene bub1, confirming this surveillance pathway has to operate through the APC/C. However, mutations in the twins/aar gene, which encodes the 55kDa regulatory subunit of PP2A, do suppress the mks metaphase arrest and so permit an alternative means of initiating anaphase. Thus the APC/C might normally be required to inactivate wild-type twins/aar gene product.

Anaphase↗
PubMed2004

Congenital adrenal hypoplasia and male pseudohermaphroditism due to DAX1 mutation, SF1 mutation or neither: a patient report.

A 15 year-old African American phenotypic female with congenital adrenal hypoplasia and intra-abdominal testes is described; she received cortisone acetate, 9alpha-Florinef, Premarin and Provera for maintenance therapy. Evaluation for DAX1, SF1 mutations using Southern blotting, PCR, PCR amplification, coding sequences, and splice site analyses have not detected any genetic abnormalities. While only 30% of the reported DAX1 mutation defects have been identified by a variety of genetic laboratory techniques, it remains probable that this unusual patient has either a DAX1 or SF1 mutation defect. A Wnt-4 defect was not evaluated.

Adolescent↗
PubMed1999

Multiple endocrine neoplasia type 2A with the identical somatic mutation in medullary thyroid carcinoma and pheochromocytoma without germline mutation at the corresponding site in the RET proto-oncogene.

A germline mutation either in exon 10 or 11 of the RET proto-oncogene is found in the majority of patients with multiple endocrine neoplasia type 2A (MEN 2A). A 41-year-old female patient was referred for further evaluation of incidentally discovered right adrenal tumor. She had bilateral adrenal pheochromocytomas and medullary thyroid carcinomas detected by endocrinological and radiological examination, and diagnosed as MEN 2A. Molecular genetic testing of the RET exons 10 and 11 exhibited the identical somatic missense mutation at codon 634 in both tumors but did not confirm germline mutations in the corresponding sites. Possible mechanisms for tumorigenesis in this patient are discussed.

Adrenal Gland Neoplasms↗
PubMed1986

The tip-E mutation of Drosophila decreases saxitoxin binding and interacts with other mutations affecting nerve membrane excitability.

A recessive temperature-sensitive paralytic mutation, tip-E, is associated with reduced binding of [3H]saxitoxin to voltage-sensitive sodium channels in membranes from adult Drosophila heads. There is a decrease of 30-40% in the number of [3H]saxitoxin-binding sites per mg protein (Bmax), but the dissociation constant (Kd) for [3H]saxitoxin binding is normal in the remaining population of binding sites. This decrease is not due to a general hypotrophy of neural tissue since the number of alpha-bungarotoxin binding sites is normal in tip-E mutants. Although saxitoxin binding is reduced in vitro, pharmacological experiments suggest that tip-E mutants have close to the wild-type number of sodium channels in vivo. This suggestion is supported by the observation that at permissive temperatures tip-E only marginally suppresses a mutation which causes enhanced membrane excitability. However, even at permissive temperatures tip-E interacts synergistically with mutations that decrease membrane excitability. In this case, the double mutants exhibit reduced viability and/or longevity. We postulate that either the structure of sodium channels or their microenvironment is altered in tip-E mutants resulting in an increased liability of binding sites in vitro.

Amphibian Proteins↗
PubMed2003

Mutations in putative mutator genes of Mycobacterium tuberculosis strains of the W-Beijing family.

Alterations in genes involved in the repair of DNA mutations (mut genes) result in an increased mutation frequency and better adaptability of the bacterium to stressful conditions. W-Beijing genotype strains displayed unique missense alterations in three putative mut genes, including two of the mutT type (Rv3908 and mutT2) and ogt. These polymorphisms were found to be characteristic and unique to W-Beijing phylogenetic lineage. Analysis of the mut genes in 55 representative W-Beijing isolates suggests a sequential acquisition of the mutations, elucidating a plausible pathway of the molecular evolution of this clonal family. The acquisition of mut genes may explain in part the ability of the isolates of W-Beijing type to rapidly adapt to their environment.

Amino Acid Sequence↗
PubMed1999

Increased occurrence of cleft lip in glycogen storage disease type II (GSDII): exclusion of a contiguous gene syndrome in two patients by presence of intragenic mutations including a novel nonsense mutation Gln58Stop.

Genetic deficiency of lysosomal acid alpha-glucosidase (acid maltase) results in the autosomal recessive disorder glycogen storage disease type II (GSDII) in which intralysosomal accumulation of glycogen primarily affects function of skeletal and cardiac muscle. During an earlier review we noted 3 in 100 cases of GSDII with incidental description of cleft lip. In addition, we identified 2 of 35 GSDII patients referred to us for molecular studies with co-occurence of cleft lip, considerably greater than the estimated frequency of nonsyndromic cleft lip with or without cleft palate of 1 in 700 to 1,000. Because several lines of evidence support a minor cleft lip/palate (Cl/P) locus on chromosome 17q close to the locus for GSDII, we defined the molecular basis for the GSDII in these two patients to determine if they represented a contiguous gene syndrome. Patient I (of Dutch descent) was homozygous and the parents heterozygous for an intragenic deletion of exon 18 (deltaex18), common in Dutch patients. Patient II was heterozygous for delta525T, a mutation also common in Dutch patients and a novel nonsense mutation (172 [corrected] C-->T; Gln58Stop) in exon 2, the first coding exon. The mother was heterozygous for the delta525T and the father for the 172 [corrected] C-->T; Gln58Stop. The finding that both patients carried intragenic mutations eliminates a contiguous gene syndrome. Whereas the presence of cleft lip/cleft palate in a patient with GSDII could be coincidental, these co-occurences could represent a modifying action of acid alpha-glucosidase deficiency on unlinked or linked genes that result in increased susceptibility for cleft lip.

Base Sequence↗
PubMed1998

Noval mutation (Y184C) in exon 4 of the beta-sarcoglycan gene identified in a Portuguese patient. Mutations in brief no. 177. Online.

We report a novel beta-sarcoglycan gene mutation identified in a 21-year-old Portuguese male with a progressive myopathy of intermediate severity, who had been misdiagnosed as Becker Muscular Dystrophy (BMD) based on clinical observations and muscle immunocytochemical anaylsis with dystrophin antibodies only. Since no detectable deletions or duplications were found in the dystrophin gene, we screened for mutations in the sarcoglycan genes by PCR-SSCP. The patient's sample showed a band of increased mobility in exon 4 of the beta-sarcoglycan gene which, upon sequencing, was found to represent a homozygous A-->G transversion at nucleotide 551, resulting in a tyrosine to cysteine substitution at position 184 (Y184C). Carrier status was ascertained in both parents and a sister. These aberrant conformers were not detected in 85 unrelated control individuals screened by PCR-SSCP analysis. All seven beta-sarcoglycan mutations reported to date are associated with a severe phenotype and occur in exons 3 and 4, which correspond to the immediate extracellular domain of the protein. This region contains five conserved cysteine residues. In our patient, the presence of an extra cysteine residue could interefere with intra- and/or inter-molecular disulphide bond formation. The intermediate phenotype could perhaps result from the assembly of both normal and abnormal complexes, depending on the formation of the disulphide bonds.

Adult↗
PubMed1998

A common beta ig-h3 gene mutation (delta f540) in a large cohort of Sardinian Reis Bücklers corneal dystrophy patients. Mutations in brief no. 180. Online.

Reis-Bücklers' corneal dystrophy (RBCD) is a relatively rare autosomal dominant disease originating in the Bowman's membrane, which causes severe visual impairment. Recently RBCD, together with lattice corneal dystrophy type I (LCDI), granular corneal dystrophy (CDGG1) and Avellino stromal dystrophy (ASD), all mapped on 5q31, were found to be associated to four different mutations in the beta ig-h3 gene which codify for kerato-epithelin. We identified several cases of RBCD in Sardinia. We reconstructed through genealogical search two eight generation-families, originating from the same village (Arbus), indicating a common ancestor for RBCD in Sardinia. Linkage studies on these families confirmed the association of the disease with the 5q31 region. Sequence analysis of beta ig-h3 gene revealed a trinucleotide deletion in exon 12, corresponding to the loss of F540 in the protein sequence (delta F540). Our data describe a new mutation in the beta ig-h3 gene causing RBCD. This dominant negative mutation is located in the fourth internal repeat of kerato-epithelin which is a protein domain highly conserved across species. This suggests the basic role of this domain in maintaining the proper kerato-epithelin structure which when altered can cause the typical precipitates in the RBCD cornea.

Chromosomes, Human, Pair 5↗
PubMed1998

Two novel mutations consisting in minor gene rearrangements in the human low density lipoprotein receptor gene in Italian patients affected by familial hypercholesterolemia. Mutations in brief no. 194. Online.

Mutations in the low density lipoprotein (LDL)-receptor gene cause familial hypercholesterolemia (FH), an autosomal dominant disease associated to an increased risk of premature atherosclerosis. We describe two novel mutations found in Italian families and consisting in minor gene rearrangements. The first one (FH-Pisa) is a tetranucleotide insertion occurring in exon 8, which causes a frameshift and a premature stop codon. The second one (FH-Chieti3) occurs at the 3'-end of exon 4 and consists in a trinucleotide deletion replaced by a six-base insertion, so that the reading frame is maintained with a glutamic acid-to-cysteine substitution at codon 207 and the insertion of a lysine at codon 208. Both mutations occur in regions of the LDL-receptor gene which can be considered hotspots for minor rearrangements.

Amino Acid Substitution↗
PubMed1998

Mutation in the nerve-specific 5'non-coding region of Cx32 gene and absence of specific mRNA in a CMTX1 Italian family. Mutations in brief no. 195. Online.

Charcot-Marie-Tooth type I demyelinating neuropathies are genetically heterogeneous disorders (chrmosome 17,1,X). There are at least three genes on X chromosome, the more frequently involved being Cx32 in Xq13.1. Cx32 encodes for connexin-32, a gap junction protein of 283 aminoacids. We report the results of molecular studies in a CMTX1 Italian family, in which the mutation, found in the 5'-UTR, resulted in an abnormal mRNA connexin-32 expression. Mutations in PMP22 and P0 genes were also excluded in this family. Cx32 gene analysis carried out by PCR-SSCP on family members genomic DNAs, running a 321 bp fragment spanning the TATA box, the trasciptional start site, and the non coding exon 1b, revealed a shift correlated with a transition from C to T at position 40 of exon 1b of the 12 affected members, while was not found in the controls. Then the RT PCR-SSCP on cDNA from two peripheral nerve biopsies of two heterozygous females of the family were sequenced showing only the wild-type alleles and suggesting that mutated mRNAs were too unstable to be detected. The result also suggests a regulating role of the 5'-UTR of Cx32 mRNA.

5' Untranslated Regions↗
PubMed1998

A novel mutation of the down-regulated in adenoma gene in a Japanese case with congential chloride diarrhea. Mutations in brief no. 198. Online.

Congenital chloride diarrhea (CLD) is an autosomal recessive disease characterized by excretion of watery stool with a high chloride content. Pathogenesis of CLD is a deficient absorption of chloride in exchange for bicarbonate in the ileum and the colon. In 1996, it was reported that 36 patients with CLD had mutations in the down-regulated in adenoma (DRA) gene; 32 Finnish patients had a three base deletion (951delGGT), 2 Polish patients had a one base mutation (371AtoT) and 2 Polish patients had a one base deletion (344delT). In this study we analyzed the DRA gene in a Japanese boy patient with CLD and in members of his family. The patient was found to have a two base deletion (TT) at nucleotide 1526-1527 within codon 509 which results in a frameshift leading to a permature stopping at codon 517. The patient was homozygous for the deletion, his parents and brother were heterozygous, and his sister was normal. This is the first case of CLD identified to carry a mutation of the DRA gene in Asia.

Adenoma↗
PubMed2000

A 1063G-->A mutation in exon 12 of glycoprotein (GP)IIb associated with a thrombasthenic phenotype: mutation analysis of [324E]GPIIb.

We report the molecular, genetic and functional analysis of a case of thrombasthenic phenotype. The proband showed absence of platelet glycoprotein (GP)IIb and very low content of GPIIIa, and both his parents showed a marked reduction in the levels of platelet GPIIb-IIIa. Single-stranded conformational polymorphism-polymerase chain reaction (SSCP-PCR) analysis and direct sequencing of PCR-amplified GPIIb exon-12 revealed the presence of a G-->A transition at position 1063 with the expected substitution of glutamate 324 with lysine (K). This mutation did not alter the level of GPIIb mRNA. Co-expression of normal or mutant [324K] GPIIb with normal human GPIIIa in Chinese hamster ovary (CHO) cells failed to show surface exposure of [324K]GPIIb-IIIa complexes. Pulse-chase and immunoprecipitation analysis demonstrated that [324K]GPIIb cDNA was translated into proGPIIb, but neither mutant GPIIb heavy chain (GPIIbH) nor [324K]GPIIb-GPIIIa complexes were detected, suggesting that this mutation is the underlying molecular basis for the thrombasthenic phenotype. Mutation analysis demonstrated that 324E of GPIIb could be replaced by other negatively charged or polar amino acids (AAs) without impairing the surface expression of GPIIb-IIIa. However, substitution of 324E of GPIIb for a positively charged AA other than K prevented the expression of GPIIb-IIIa complexes. These observations suggest that a domain encompassing 324E of GPIIb is essential for heterodimerization with GPIIIa and its substitution for a positively charged residue precludes normal subunit association.

Animals↗