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Results for “genetic mutation”

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At least 109 records · Page 6Linked to original sources
PubMed1999

Congenital adrenal hyperplasia (21-hydroxylase deficiency) without demonstrable genetic mutations.

Congenital adrenal hyperplasia (CAH) owing to 21-hydroxylase deficiency (21-OHD) is the most common inherited defect of adrenal steroid biosynthesis. At least 36 mutations in the CYP21 gene, which is mapped to chromosome 6p21.3, have been described. We performed genetic analysis of the CYP21 gene in a patient with classic 21-OHD CAH and her family. The entire exonic coding regions and intronic regions, as well as the -1 kb 5' upstream promoter region, were thoroughly sequenced and analyzed. Despite extensive sequencing, no mutation was found in this 3.7 kb area. The 11beta-hydroxylase defect, closely mimicking the clinical and biochemical phenotype of classic 21-OHD, was excluded by directly sequencing 2.6 kb covering the entire coding of the CYP11B1 gene. Herein we describe a phenotypically and hormonally affected patient with classic simple virilizing 21-OHD CAH who lacks a mutation in the entire CYP21 gene and coding region of the CYP11B1 gene.

Adrenal Hyperplasia, Congenital↗
PubMed2006

Dissociation of food and opiate preference by a genetic mutation in zebrafish.

Both natural rewards and addictive substances have the ability to reinforce behaviors. It has been unclear whether identical neural pathways mediate the actions of both. In addition, little is known about these behaviors and the underlying neural mechanisms in a genetically tractable vertebrate, the zebrafish Danio rerio. Using a conditioned place preference paradigm, we demonstrate that wildtype zebrafish exhibit a robust preference for food as well as the opiate drug morphine that can be blocked by the opioid receptor antagonist naloxone. Moreover, we show that the too few mutant, which disrupts a conserved zinc finger-containing gene and exhibits a reduction of selective groups of dopaminergic and serotonergic neurons in the basal diencephalon, displays normal food preference but shows no preference for morphine. Pretreatment with dopamine receptor antagonists abolishes morphine preference in the wildtype. These studies demonstrate that zebrafish display measurable preference behavior for reward and show that the preference for natural reward and addictive drug is dissociable by a single-gene mutation that alters subregions of brain monoamine neurotransmitter systems. Future genetic analysis in zebrafish shall uncover further molecular and cellular mechanisms underlying the formation and function of neural circuitry that regulate opiate and food preference behavior.

Analysis of Variance↗
PubMed1980

Second-site rho mutation: genetic linkage and polyC-dependent ATPase.

Rho has been purified to homogeneity from Escherichia coli double mutant rho-115 sur-38 cells, and from rho6 and rho-115 cells. The sur-38 mutation suppresses the original rho-115 phenotype. We observe that the polyC-dependent ATPases of these three rho preparations have the same specific activities. However, the ATPase of rho from the double rho-115 sur-38 mutant is extremely heat labile, while that from rho-115 shows a heat lability intermediate between the wild type and the double mutant. Transduction analysis suggests that sur-38 is closely linked to rho-115 in the order ilv--sur-38--rho-115--metE. These data are consistent with the model that the sur-38 mutation affects the structural gene for rho.

Adenosine Triphosphatases↗
PubMed2004

Short- and long-term impact of receiving genetic mutation results in women at increased risk for hereditary breast cancer.

Forty-seven unaffected women from high-risk breast cancer families who had received results for hereditary breast/ovarian predisposition genes between 1 month and 5 years ago were interviewed regarding their experiences. Women responded to open-ended questions. The initial emotional turmoil reported by most was generally short lived. However, the impact of genetic testing went beyond the individual to the extended family and social context, particularly in the short-term. A common theme was the difficulty associated with divulging a result to family members, who were also adjusting to their own result. The majority of carriers reported advantages that were both physical (options for surveillance programs and prophylactic surgery) and emotional (reduced uncertainty, increased awareness of options and knowledge about risk, preparation time). Most carriers reported no change in lifestyle although some reported discovering their mutation status as a positive life-changing experience. Implications for genetic counseling and further research are discussed.

Adaptation, Psychological↗
PubMed2001

Positional dissociation between the genetic mutation responsible for pseudohypoparathyroidism type Ib and the associated methylation defect at exon A/B: evidence for a long-range regulatory element within the imprinted GNAS1 locus.

Pseudohypoparathyroidism type Ib (PHP-Ib) is a paternally imprinted disorder which maps to a region on chromosome 20q13.3 that comprises GNAS1 at its telomeric boundary. Exon A/B of this gene was recently shown to display a loss of methylation in several PHP-Ib patients. In nine unrelated PHP-Ib kindreds, in whom haplotype analysis and mode of inheritance provided no evidence against linkage to this chromosomal region, we confirmed lack of exon A/B methylation for affected individuals, while unaffected carriers showed no epigenetic abnormality at this locus. However, affected individuals in one kindred (Y2) displayed additional methylation defects involving exons NESP55, AS and XL, and unaffected carriers in this family showed an abnormal methylation at exon NESP55, but not at other exons. Taken together, current evidence thus suggests that distinct mutations within or close to GNAS1 can lead to PHP-Ib and the associated epigenetic changes. To further delineate the telomeric boundary of the PHP-Ib locus, the previously reported kindred F, in which patient F-V/51 is recombinant within GNAS1, was investigated with several new markers and direct nucleotide sequence analysis. These studies revealed that F-V/51 remains recombinant at a single nucleotide polymorphism (SNP) located 1.2 kb upstream of XL. No heterozygous mutation was identified between exon XL and an SNP approximately 8 kb upstream of NESP55, where this affected individual becomes linked, suggesting that the genetic defect responsible for parathyroid hormone resistance in kindred F, and probably other PHP-Ib patients, is located >or=56 kb centromeric of the abnormally methylated exon A/B. A region upstream of the known coding exons of GNAS1 is therefore predicted to exert, presumably through imprinting of exon A/B, long-range effects on G(s)alpha expression.

Chromosome Mapping↗
PubMed1999

Genetic mutations as a cause of hyperinsulinemic hypoglycemia in children.

Hyperinsulinemic hypoglycemia in children is associated with unregulated secretion of insulin and hypoglycemia, a condition that is now known to be genetically diverse. This article reviews recent progress that has elucidated several beta-cell molecular defects responsible for the pathogenesis of this disorder.

Child↗
PubMed1991

Analysis of genetic mutations in human lactate dehydrogenase-A(M) deficiency using DNA conformation polymorphism in combination with polyacrylamide gradient gel and silver staining.

Human lactate dehydrogenase (LDH)-A mutant gene was analyzed by polymerase chain reaction - DNA conformation polymorphism (DCP). We used polyacrylamide gradient gel and silver staining procedures for DCP analysis and observed abnormal migration patterns in individuals heterozygous for LDH-A deficiency. Further sequence determination of the mutant alleles consistently resulted in detection of base substitutions, a G to T transversion at codon 328 (GAG----TAG), and synonymous substitutions at codon 115, 160 and 172. Such mutations were easily detectable using the DCP technique. The DCP technique using the polyacrylamide gradient gel and silver staining method seems likely to be useful for the rapid screening of mutations and for further genotype detection.

Amino Acid Sequence↗
PubMed2001

Genetic mutations in certain head and neck conditions of interest to the dentist.

This article identifies certain syndromes of the head and neck, which a dentist may see in clinical practice, and relates these syndromes to their sites of mutation on involved genes. This paper is timely with the near completion of the Human Genome Project, the mapping of the entire human genetic material. Knowing the site of the genetic lesion is important in helping clinicians understand the genetic basis for these conditions, and may help in our future understanding of remedies and treatments.

Amelogenesis Imperfecta↗
PubMed2006

Genetic mutation analysis by CE with LIF detection using inverse-flow derivatization of DNA fragments.

Inverse-flow derivatization is a novel approach to obtain fluorescent DNA derivatives in DNA analysis based on CE with LIF detection. In the present work, we want to explore the feasibility of the application of this method into the mutation detection based on constant denaturant capillary electrophoresis (CDCE) and SSCP analysis. The DNA fragments were first amplified by PCR using a pair of common primers without fluorescent label, and then the mutations were determined by CDCE or SSCP analysis based on CE-LIF with inverse-flow derivatization of DNA fragments. The experimental conditions were investigated systematically, and different labeling modes including inverse-flow derivatization, on-column derivatization and fluorescent labeled primer technique were compared. The inverse-flow derivatization was successfully used in the detection of C677T mutation in the methylenetetrahydrofolate reductase gene by CDCE or SSCP analysis. Our preliminary results demonstrate that inverse-flow derivatization is very simple, inexpensive and sensitive and well suitable for the genetic analysis in clinical diagnosis.

DNA↗
PubMed2001

Altered expression of beta-catenin without genetic mutation in intrahepatic cholangiocarcinoma.

beta-catenin which has a role in E-cadherin mediated cell-to-cell adhesion, and is also involved in Wnt signaling pathways as a downstream signaling molecule accumulating in the cytoplasm and nucleus constitutively activates Tcf/LEF-associated transcription of oncogenic genes. We examined the expression pattern and the genetic alteration of beta-catenin to determine the role of beta-catenin in cancer formation and/or progression in intrahepatic cholangiocarcinoma (ICC). beta-catenin expression was immunohistochemically examined in 71 surgically resected ICC samples, and correlation between the expression pattern and clinicopathologic factors was investigated. Mutation analysis of beta-catenin exon 3, which included the responsible element for Wnt signaling was done in 55 samples, using PCR-SSCP and direct sequence methods. Immunohistochemical analysis revealed the reduced membranous expression of beta-catenin in 58 (82%) ICCs and aberrant nuclear expression in 11 (15%) ICCs. The membranous expression was preserved in 62% of the papillary adenocarcinomas, and was frequently reduced in tumors with a poorer histological differentiation (84%), with a significant difference (P =.01). Genetic analysis showed that none of the 55 ICCs examined carried mutations in beta-catenin exon 3. The present study indicates that reduced membranous expression of beta-catenin is associated with non-papillary ICCs which have a more malignant behavior, and that nuclear translocation of beta-catenin results in oncogenic events. Mutations in beta-catenin exon 3 do not appear to be responsible for nuclear translocation of beta-catenin in ICCs.

Aged↗
PubMed2002

Genetic mutation and early onset of T-cell leukemia in pediatric patients infected at birth with HTLV-I.

T-cell leukemia/lymphoma (T-c LL) associated with prior infection with HTLV-I is rarely described in children. We present herein, the clinical, morphological, and virologic features of T-c LL, which occurred in eight pediatric cases with similar features of ATLL described in adults. There were three girls and five boys with age ranging from 2 to 18 years. Lymphoadenopathy, hepatosplenomegaly and marked skin lesions were presented in all cases. Five patients had hypercalcemia. The diagnostic criteria of T-c LL were based on both morphological and immunophenotypical analyses characterized by T-cell markers positively. Seven cases were cCD3+, CD4/CD25+, whereas CD1a and TdT were negative in all cases tested. HTLV-I antibodies were detected in all cases. HTLV-I provirus integration of at least one provirus was seen in all cases tested by molecular analysis. Mother-to-child transmission of HTLV-I was demonstrated in six cases. Interestingly, a homozygous deletion in p16 gene locus was observed in all four cases studied, while exons 7 and 8 of p53 were deleted in one child. The deletion of the p16(INK4A)/p14(ARF) or mutation of p53, key regulatory protein of cell cycle checkpoint in G1/S progression, found in five of the eight pediatric patients suggests that in these cases genetic lesions associated with HTLV-I infection may predispose for an early onset of leukemia.

Adolescent↗
PubMed1993

Genetic mutations in ten unrelated American patients with symptomatic type 1 protein C deficiency.

Symptomatic patients with Type 1 protein C deficiency and venous thrombosis were analysed for defects in this gene using polymerase chain reaction amplification and direct sequencing of all nine exons. Ten different heterozygous point mutations were detected in 19 patients from eleven American families. Seven represent novel mutations. Two of these were found in the TATA box or near the transcription initiation site and presumably lead to loss of transcription, and seven missense mutations were found including G103R, P168L, R169W, I201T, P279L, T298M, and C384Y. These may lead to abnormal folding or thermodynamic instability of the protein C molecule, potentially causing abnormal secretion or rapid clearance from the circulation. Two other protein C mutations, a nonsense mutation at codon Trp-145 and a deletion inducing a frameshift at codon 364 resulting in premature termination at codon 378, likely lead to unstable products. The previously published R169W mutation resulted in a Type 1 deficiency. The data show that diverse molecular defects result in similar phenotypes and emphasize that a wide variety of mutations are responsible for Type 1 protein C deficiency in the American setting of a diverse population.

Adult↗
PubMed2006

Dissecting natural killer cell activation pathways through analysis of genetic mutations in human and mouse.

Natural killer (NK) cell cytotoxicity is mediated by multiple germ line-encoded activating receptors that recognize specific ligands expressed by tumor cells and virally infected cells. These activating receptors are opposed by NK inhibitory receptors, which recognize major histocompatibility complex class I molecules on potential targets, raising the threshold for NK cell activation. Once an abnormal cell has been detected, NK cells are the sentinel source of cytolytic mediators, such as granzymes and perforins, as well as interferon-gamma, which can polarize the immune response to a T-helper 1 cell type. Activation signals are transmitted by adhesion-dependent pathways, immunoreceptor tyrosine-based activation motif (ITAM)-dependent pathways, DAP10 ITAM-independent pathways, and by signaling through immunoreceptor tyrosine-based switch motifs. These pathways activate downstream signaling partners to trigger NK cell cytotoxicity. Some of these downstream molecules are unique to the various pathways, and some of these molecules are shared. Because of the complexity of signals involved in NK cell-target cell interaction, the generation of mice with targeted mutations in signaling molecules involved in adhesion, activation, or inhibition is essential for a precise dissection of the mechanisms regulating NK cell effector functions. Here we review recent advances in the genetic analysis of the signaling pathways that mediate NK cell killing.

Animals↗
PubMed2000

Prevalence of genetic mutations that predispose to thrombophilia in a Greek Cypriot population.

Several hereditary disorders, particularly those affecting the physiological anticoagulation systems, have been well established as risk factors for venous thromboembolism. In the present study, we investigated the prevalence of the following thrombogenic mutations in a Greek-Cypriot population: the G1691 factor V Leiden mutation, the G20210A mutation in the prothrombin gene, and the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR). All three variants have been documented to be significant risk factors for various cardiovascular conditions. Ninety unrelated subjects were screened. For the Leiden mutation, 11 subjects (12.2%) were heterozygous and one (1.1%) was homozygous. Seven subjects (7.8%) were heterozygous for the G20210A variant in prothrombin; no homozygotes were identified. The C677T mutation in MTHFR was found in 40 individuals in the heterozygous state (44.4%), and in 16 individuals in the homozygous state (17.8%). These data demonstrate that Greek-Cypriots have an increased frequency of thrombogenic mutations, and suggest that screening for these mutations should be seriously considered, especially when surgery or pregnancy is planned. This is the first study for the frequency of mutations in risk factors that predispose to thrombophilia on the island of Cyprus.

Cyprus↗