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At least 793 records · Page 44Linked to original sources
PubMed1993

Thyroglobulin gene point mutation associated with non-endemic simple goitre.

Simple goitre is defined as an enlargement of the thyroid gland that is not the result of an inflammatory or neoplastic process and is not associated with thyrotoxicosis or myxoedema; the cause is unknown in most cases. Structural or regulatory defects in the proteins involved in thyroid metabolism might be involved in the functional abnormality that brings about the disorder. We have found a mutation within exon 10 of the thyroglobulin gene in 25 of 56 members of three families affected by simple goitre; 14 of the gene carriers had the disorder. DNA sequencing showed a mis-sense mutation within thyroglobulin gene exon 10, resulting in a glutamine to histidine substitution. Thus, some cases of non-endemic simple goitre are associated with a mutation at the thyroglobulin locus.

Adult↗
PubMed2006

Identification of a novel inactivating R465Q mutation of the calcium-sensing receptor.

In this study, we describe a 52-year-old woman, who was diagnosed with familial benign hypocalciuric hypercalcemia (FBHH), a condition characterized by hypercalcemia, low urinary calcium excretion, and normal parathyroid hormone PTH levels, resulting from inactivating mutations of the calcium-sensing receptor (CaSR). In order to identify and characterize the underlying mutation in the CASR gene, direct sequence analysis of CASR exons 2-7 was performed, and functional activity was examined by transient transfection of human embryonic kidney (HEK-293) cells with wild-type and mutant CaSRs, followed by intracellular calcium measurement using fluorometry, and Western blot analysis. Sequence analysis demonstrated, in addition to the already described A986S polymorphism, a novel heterozygous G--> A substitution in CASR exon 5 that causes an arginine to glutamine substitution at codon 465 (R465Q). Functional analysis showed a rightward shift of the dose-response curve with a significant increase of the EC50 from 5.4 mM of the CaSR carrying the A986S polymorphism alone to 11.3 mM of the CaSR carrying the R465Q mutation in the presence of the A986S polymorphism. Western blot analysis of membrane protein revealed an even higher expression level of the R465Q mutant protein compared to wild-type CaSR. In conclusion, we identified a novel heterozygous loss-of-function R465Q mutation of the CASR gene, which is characterized by a blunted response to calcium stimulation, thereby causing FBHH.

Blotting, Western↗
PubMed1999

Will genetic testing for predisposition for disease result in fatalism? A qualitative study of parents responses to neonatal screening for familial hypercholesterolaemia.

OBJECTIVE: to describe parents' perceptions of familial hypercholesterolaemia (FH), an inherited predisposition to heart disease, following population-based neonatal screening. DESIGN: a qualitative analysis of semi-structured interviews with the parents of 24 children who had received a positive screening test result informing them that their child was at-risk for having FH. RESULTS: responses to screening seemed to vary according to perceptions of the underlying cause of the positive screening test result. When parents perceived the test as detecting raised cholesterol the condition was perceived as familiar, dietary in origin, controllable and less threatening. When the test was seen as detecting a genetic problem, the condition was perceived as uncontrollable and, hence, more threatening. CONCLUSION: these pilot data raise questions about the extent to which assessing disease risks by DNA analysis may result in a sense of fatalism, adversely affecting motivation to change behaviour and to reduce risks.

Adult↗
PubMed2000

Mutation analysis of BRCA1 and BRCA2 cancer predisposition genes in radiation hypersensitive cancer patients.

PURPOSE: The dose intensity of radiotherapy (RT) used in cancer treatment is limited in rare individuals who display severe normal tissue reactions after standard RT treatments. Novel predictive assays are required to identify these individuals prior to treatment. The mechanisms responsible for such reactions are unknown, but may involve dysfunction of genes involved in the sensing and response of cells to DNA damage. The breast cancer susceptibility genes BRCA1 and BRCA2 are implicated in DNA damage repair and the control of genome stability. The purpose of this study was to determine if clinical radiation hypersensitivity is related to mutations of the BRCA1 and BRCA2 genes. Such information is of potential use in the clinical management of BRCA mutation carriers and their families. METHODS AND MATERIALS: Twenty-two cancer patients who developed severe normal tissue reactions after RT were screened for mutations of BRCA1 and BRCA2, using various methods including protein truncation testing, direct DNA sequencing, and a PCR-based BRCA1 exon 13 duplication test. RESULTS: No mutations were detected in the 22 patients tested, despite screening for the majority of commonly described types of mutations of BRCA1 and BRCA2. CONCLUSION: These early results suggest that genes other than BRCA1 and BRCA2 probably account for most cases of clinical radiation hypersensitivity, and that screening for mutations of BRCA1 and BRCA2 is unlikely to be useful in predicting response to radiotherapy. However, it has not been excluded that some BRCA1 or BRCA2 heterozygotes might experience unexpected RT toxicity; further BRCA mutation screening on radiation sensitive individuals is warranted.

BRCA2 Protein↗
PubMed1999

Structure of the 13-fold symmetric portal protein of bacteriophage SPP1.

We have determined the three-dimensional structure of bacteriophage SPP1 portal protein (gp6) using electron microscopy at liquid-helium temperatures and angular reconstitution. The 13-fold symmetric gp6 oligomer is a turbine-shaped structure with three distinct regions: a conical stem with a central channel; the turbine wings region; and a fringe of small 'tentacles' at the end of the channel exposed to the viral head interior. The tentacle region appears flexible and may be associated with a particular function - sensing when the correct amount of DNA has been packaged. The three-dimensional structure of the gp6 SizA mutant, which packages a smaller chromosome, reveals significant differences in that region.

Bacillus Phages↗
PubMed2000

Somatic mutations of Fas (Apo-1/CD95) gene in cutaneous squamous cell carcinoma arising from a burn scar.

Fas (Apo-1/CD95) is a cell-surface receptor involved in cell death signaling, and recent reports have suggested that defects within the Fas receptor pathway such as Fas mutation play an important part in the development and progression of human tumors. Burn scar-related squamous cell carcinoma of skin is a unique subtype of cutaneous squamous cell carcinoma, and tends to be more aggressive in nature than conventional squamous cell carcinoma. The molecular mechanisms underlying the development and progression of burn scar-related squamous cell carcinoma, however, are not clear. In this study, we analyzed the entire coding region and all splice sites of the Fas gene for the detection of the somatic mutations in a series of 50 conventional squamous cell carcinomas and 21 burn scar-related squamous cell carcinomas by polymerase chain reaction, single strand conformation polymorphism, and DNA sequencing. We detected mis-sense mutations in three of 21 burn scar-related squamous cell carcinomas (14.3%), whereas no mutation was detected in 50 conventional squamous cell carcinomas. Of the three Fas mutations detected in the burn scar-related squamous cell carcinomas, one was found in Fas ligand-binding domain, another one was identified in the death domain known to be involved in the transduction of an apoptotic signal, and the other one was found in the transmembrane domain. Our data show that some burn scar-related squamous cell carcinomas have Fas gene mutations in important regions for the apoptosis function and suggest that these mutations might be involved in the pathogenesis of burn scar-related squamous cell carcinomas. In addition, our results provide an important clue to understanding the difference between burn scar-related squamous cell carcinoma and conventional squamous cell carcinoma at the molecular level.

Adolescent↗
PubMed2003

[Biologic therapy of inflammatory bowel disease].

Biological therapies in inflammatory bowel disease reflect the exponential advancement in understanding the human intestinal immune system and particularly the biology of intestinal inflammation during the past decade. The better understanding of the mechanisms of inflammatory bowel disease has evolved from desriptive clinical data and genetically engineered animal models. It led to great interest in the evaluation of a variety of new therapeutic agents with novel actions. This review will discuss the mechanisms of biologicals (antibodies against pro-inflammatory cytokines, T cell antibodies, anti-inflammtory cytokines, adhesion molecule blockers, growth factors, hormones, colony stimulating factors, fusion proteins, anti-sense oligonucleotides, trefoil peptides, immunostimulatory [ISS] DNA) used in the treatment of inflammatory bowel disease and summarizes the available data on established biologic therapies as well as investigational agents and briefly touch on probiotics. Based on the data discussed, it seems that biologicals will play an important role in managing inflammatory bowel disease in the near future.

Animals↗
PubMed2000

Cloning and function of rabbit peroxisome proliferator-activated receptor delta/beta in mature osteoclasts.

Osteoclasts modulate bone resorption under physiological and pathological conditions. Previously, we showed that both estrogens and retinoids regulated osteoclastic bone resorption and postulated that such regulation was directly mediated through their cognate receptors expressed in mature osteoclasts. In this study, we searched for expression of other members of the nuclear hormone receptor superfamily in osteoclasts. Using the low stringency homologous hybridization method, we isolated the peroxisome proliferator-activated receptor delta/beta (PPARdelta/beta) cDNA from mature rabbit osteoclasts. Northern blot analysis showed that PPARdelta/beta mRNA was highly expressed in highly enriched rabbit osteoclasts. Carbaprostacyclin, a prostacyclin analogue known to be a ligand for PPARdelta/beta, significantly induced both bone-resorbing activities of isolated mature rabbit osteoclasts and mRNA expression of the cathepsin K, carbonic anhydrase type II, and tartrate-resistant acid phosphatase genes in these cells. Moreover, the carbaprostacyclin-induced bone resorption was completely blocked by an antisense phosphothiorate oligodeoxynucleotide of PPARdelta/beta but not by the sense phosphothiorate oligodeoxynucleotide of the same DNA sequence. Our results suggest that PPARdelta/beta may be involved in direct modulation of osteoclastic bone resorption.

Acid Phosphatase↗
PubMed2000

UV damage causes uncontrolled DNA breakage in cells from patients with combined features of XP-D and Cockayne syndrome.

Nucleotide excision repair (NER) removes damage from DNA in a tightly regulated multiprotein process. Defects in NER result in three different human disorders, xeroderma pigmentosum (XP), trichothiodystrophy (TTD) and Cockayne syndrome (CS). Two cases with the combined features of XP and CS have been assigned to the XP-D complementation group. Despite their extreme UV sensitivity, these cells appeared to incise their DNA as efficiently as normal cells in response to UV damage. These incisions were, however, uncoupled from the rest of the repair process. Using cell-free extracts, we were unable to detect any incision activity in the neighbourhood of the damage. When irradiated plasmids were introduced into unirradiated XP-D/CS cells, the ectopically introduced damage triggered the induction of breaks in the undamaged genomic DNA. XP-D/CS cells thus have a unique response to sensing UV damage, which results in the introduction of breaks into the DNA at sites distant from the damage. We propose that it is these spurious breaks that are responsible for the extreme UV sensitivity of these cells.

Base Pairing↗
PubMed1997

Hypercalcemia in children: an overview.

Hypercalcemia occurs in children of all ages. A serum calcium level over 15 mg/dL can be life-threatening. The association between familial hypocalciuric hypercalcemia (FHH) and neonatal severe hyperparathyroidism (NHPT) has been discussed. FHH is characterized by a high serum calcium concentration, relatively low urine calcium excretion, and an inappropriately normal parathyroid hormone (PTH) concentration. On the other hand, NHPT is a rare disease characterized by markedly increased serum calcium (15 mg/dL) and PTH concentrations, and is fatal without parathyroidectomy early in life. Recently, a complementary DNA encoding an extracellular calcium-sensing receptor has been isolated. Furthermore, three mutations in the receptor gene in FHH and NHPT individuals have been described. Thus, heterozygotes and homozygotes of FHH may have an intermittent hypercalcemia and NHPT, respectively. Vitamin D-related hypercalcemia, and vitamin D intoxication and immobilization are also discussed.

Calcium-Binding Proteins↗
PubMed1999

The Yersinia enterocolitica pYV virulence plasmid contains multiple intrinsic DNA bends which melt at 37 degrees C.

Temperature has a pleiotropic effect on Yersinia enterocolitica gene expression. Temperature-dependent phenotypes include the switching between two type III protein secretion systems, flagellum biosynthesis (</=30 degrees C) and virulence plasmid-encoded Yop secretion (37 degrees C). The mechanism by which temperature exerts this change in genetic programming is unclear; however, altered gene expression by temperature-dependent changes in DNA topology has been implicated. Here, we present evidence that the Y. enterocolitica virulence plasmid, pYV, undergoes a conformational transition between 30 and 37 degrees C. Using a simplified two-dimensional, single-gel assay, we show that pYV contains multiple regions of intrinsic curvature, including virF, the positive activator of virulence genes. These bends are detectable at 30 degrees C but melt at 37 degrees C, the temperature at which the cells undergo phenotypic switching. We also show that pACYC184, a plasmid used as a reporter of temperature-induced changes in DNA supercoiling, has a single region of intrinsic bending detected by our assay. Topoisomers of pACYC184, with and without this bend, isolated from Y. enterocolitica were resolved by using chloroquine gels. The single bend has a dramatic influence on temperature-dependent DNA supercoiling. These data suggest that the Y. enterocolitica pYV plasmid may undergo a conformational change at the host temperature due to melting of DNA bends followed by compensatory adjustments in superhelical density. Hence, changes in DNA topology may be the temperature-sensing mechanism for virulence gene expression in Y. enterocolitica and other enteric pathogens.

Chloroquine↗
PubMed1996

Localization of the expression of complement component 3 in the human endometrium by in situ hybridization.

C3 production by the human endometrium has been previously described. The objective of the current study was to localize the site of expression and regulation of the third component of complement, C3, in the endometrium. Eight secretory and eight proliferative archival endometrial samples from hysterectomy and endometrial biopsy specimens were used for in situ hybridization analysis. This analysis was performed with a radiolabeled riboprobe synthesized from a 736-bp template representing sequence 1944-2680 of the human C3 complementary DNA. Duplicate sections were hybridized with sense and antisense riboprobes. Resultant autoradiograms were analyzed qualitatively by light- and darkfield microscopy. In proliferative endometrium, minimal expression of C3 was observed and was limited to a few stromal patches and glands throughout the section. In the secretory samples, prominent C3 expression was observed in both the glands and stroma of the basalis layer. Endometrial lymphocytes did not express C3. Endometrial stromal and glandular cells express the C3 gene. Endometrial lymphocytes did not express C3, but other nondistinct lymphoid elements scattered in the stroma may be expressing C3. There was a visibly more intense expression of C3 in the basalis layer of the secretory endometrium than in proliferative endometrium. The spatial and temporal pattern of C3 expression may have implications in normal menstrual physiology and in the immunological response of the endometrium to the invading trophoblast during placentation.

Adult↗
PubMed2004

Autosomal dominant hypocalcemia in monozygotic twins caused by a de novo germline mutation near the amino-terminus of the human calcium receptor.

UNLABELLED: To define the molecular pathogenesis of severe postnatal hypocalcemia in monozygotic twin sisters, we sequenced their CaR gene and identified a missense mutation, K29E. Expression of the mutant receptor in vitro showed a marked increase in Ca2+ sensitivity explaining the observed phenotype. Additional mutagenesis studies lead us to speculate concerning a novel mechanism whereby the K29E mutation may lead to receptor activation. INTRODUCTION: Activating mutations of the Ca(2+)-sensing receptor (CaR) gene have been identified in subjects with autosomal dominant hypocalcemia. Study of such mutations has provided insight into the mechanism of activation of the CaR. MATERIALS AND METHODS: We performed biochemical and molecular genetic studies on monozygotic twin sisters who presented with early postnatal hypocalcemia and on their unaffected sister and parents. Functional characterization of mutant CaRs transfected in HEK-293 cells included immunoblots to monitor protein expression and Ca2+ stimulation of phosphoinositide hydrolysis to measure Ca2+ sensitivity. RESULTS: We identified a K29E missense mutation in the twin sisters but not in their parents or unaffected sister. The K29E mutant CaR showed a marked increase in Ca2+ sensitivity, including when it was co-transfected with wildtype CaR cDNA, consistent with a dominant effect. Substitution of K29 by aspartate equivalently increased CaR sensitivity, whereas conservative substitution by arginine did not. CONCLUSIONS: Severe postnatal hypocalcemia in the twin sisters was caused by a de novo germline activating mutation. In a model of the Venus flytrap-like domain of the extracellular amino-terminus of the CaR, K29 is located close to a peptide loop, "loop 2," that forms part of the dimer interface and is the site of 10 of the previously reported naturally occurring activating CaR mutations. We speculate that K29E increases Ca2+ sensitivity of the CaR by disrupting a salt bridge between K29 and an acidic residue in loop 2 and thereby changes the normal structure of loop 2 that maintains the CaR in its inactive conformation.

Amino Acid Sequence↗
PubMed2003

A novel mutation in the calcium-sensing receptor responsible for autosomal dominant hypocalcemia in a family with two uncommon parathyroid hormone polymorphisms.

A novel missense activating mutation in the extracellular calcium-sensing receptor (CaSR) is reported in this work. It was identified in three related subjects with the phenotypic features of autosomal dominant hypocalcemia (ADH). The proband, a 27-year-old woman, diagnosed as having hypoparathyroidism at 7 years of age and a history of seizures, showed the highest penetrance of the mutation. The remaining two affected members presented asymptomatic chronic hypocalcemia despite severe hypoparathyroidism associated with high levels of serum phosphate and calcium urinary excretion. The missense mutation (Glu(604)Lys) affected an amino acid residue in the C terminus of the cysteine-rich domain of the extracellular amino-terminal domain, which seems to be required for the coupling of ligand binding to the activation of intracellular signaling pathways. This genetic change cosegregated with hypocalcemia in all the individuals where the mutation was found. As parathyroid hormone (PTH) secretion is the regulatory target of the CaSR, polymorphism analysis of the PTH gene was carried out. PTH polymorphisms were analyzed in the kindred studied. Affected members for the Glu(604)Lys CaSR mutation which also carried the uncommon PTH alleles showed higher penetrance of the mutation, with more severe autosomal dominant hypocalcemia. These results suggested that the PTH gene could act as a modifier locus of ADH, affecting the penetrance of the activating CaSR mutation described.

Adolescent↗
PubMed2001

S-Phase arrest by nucleoside analogues and abrogation of survival without cell cycle progression by 7-hydroxystaurosporine.

The mechanisms of resistance to nucleoside analogues established in preclinical models are rarely found in primary tumors resistant to therapy with these agents. We tested the hypothesis that cells sense sublethal incorporation of analogues into DNA during replication and react by arresting further DNA synthesis and cell cycle progression. After removal of drug, cells may be able to repair damaged DNA and continue proliferation, thus escaping nucleoside analogue toxicity. As a corollary, we evaluated whether dysregulation of this mechanism causes cell death. Using gemcitabine as a model of S-phase-specific nucleoside analogues in human acute myelogenous leukemia ML-1 cells, we found that DNA synthesis decreased, cells arrested in S-phase transit, and 60-70% of the population accumulated in S-phase in response to cytostatic conditions. Proliferation continued after washing the cells into drug-free medium. S-phase-arrested cells were then treated with otherwise nontoxic concentrations of UCN-01, which caused rapid onset of apoptosis without cell cycle progression specifically in cells with an S-phase DNA content. Thus, S-phase arrest by nucleoside analogues sensitizes cells to UCN-01, which appears to activate signaling for death mechanisms and/or inhibit survival pathways. These results differ from those in cells arrested at the G2 checkpoint, in which UCN-01 abrogates cell cycle arrest, permitting cells to progress in the cell cycle before apoptosis.

Alkaloids↗
PubMed1990

Genetic analysis of cancer in families.

Cancer is genetic, in the sense that it is caused by DNA alterations at the cellular level. On the other hand, the most important risk factors for the common cancers are environmental: cigarette smoking, environmental pollution, occupational exposures, poor diet, and so on. These two observations are not in conflict: the DNA alterations that lead to cancer are very likely to be caused by environmental mutagens. It would be valuable to know exactly what genes are altered to cause a specific cancer, because the effects of these alterations might then be reversible before cancer has a chance to develop. A key to identifying these cancer genes may lie with rare families at extremely high risk of a specific cancer. Unlike most cancer patients, members of these families may inherit an alteration that confers increased susceptibility to cancer. In these rare instances, cancer is a genetic disease at the level of the family, as well as at the level of the cell. Therefore, in these families, genes predisposing to cancer can be mapped in the same way as genes for purely genetic diseases like sickle cell anaemia, cystic fibrosis, and Huntington's disease. The hypothesis that underlies the mapping of cancer genes in families is that the genes inherited in altered form in these rare families are the same genes that are altered in somatic cells of individuals without a remarkable family history of cancer. This hypothesis has proved correct for retinoblastoma. Genes responsible for other rare cancers have been mapped in families as well: neurofibromatosis, multiple endocrine neoplasia, Wilms' tumour, and colon cancer following familial adenomatous polyps, among others. Genes responsible for common cancers are also being defined by genetic analysis, most notably breast cancer and colon cancer. This review summarizes why, how, and what genetic analysis of families can reveal about human cancers.

Chromosome Mapping↗