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S Bevan

Publications and source records attributed to S Bevan.

At least 19 recordsLinked to original sources
PubMed2003

Germline mutations in fumarate hydratase (FH) do not predispose to prostate cancer.

Inherited susceptibility to prostate cancer has been linked to a number of chromosomal regions, however no genes have been unequivocally shown to underlie reported linkages. The putative gene localised to chromosome 1q42-q43, has been designated PCaP. We have recently shown that germline mutations in the fumarate hydratase (FH) gene located on 1q43 cause smooth muscle tumours and renal cell carcinoma. It is conceivable that germline FH mutations might confer an increased risk of prostate cancer and underlie linkage of prostate cancer to PCaP. To examine this proposition we have analysed the entire coding region of FH in 160 prostate cancer cases in 77 multiple case families. No pathogenic mutations in FH were identified in any of the cases. This data makes it highly unlikely that mutations in FH confer susceptibility to prostate cancer.

Aged↗
PubMed2002

CHEK2 variants in susceptibility to breast cancer and evidence of retention of the wild type allele in tumours.

We have recently shown that the CHEK2*1100delC mutation acts as a low penetrance breast cancer susceptibility allele. To investigate if other CHEK2 variants confer an increased risk of breast cancer, we have screened an affected individual with breast cancer from 68 breast cancer families. Five of these individuals were found to harbour germline variants in CHEK2. Three carried the 1100delC variant (4%). One of these three individuals also carried the missense variant, Arg180His. In the other two individuals, missense variants, Arg117Gly and Arg137Gln, were identified. These two missense variants reside within the Forkhead-associated domain of CHEK2, which is important for the function of the expressed protein. None of these missense variants were present in 300 healthy controls. Microdissected tumours with a germline mutation showed loss of the mutant allele suggesting a mechanism for tumorigenesis other than a loss of the wild type allele. This study provides further evidence that sequence variation in CHEK2 is associated with an increased risk of breast cancer, and implies that tumorigenesis in association with CHEK2 mutations does not involve loss of the wild type allele.

Adult↗
PubMed2002

Low frequency of somatic mutations in the FH/multiple cutaneous leiomyomatosis gene in sporadic leiomyosarcomas and uterine leiomyomas.

Germline mutations in the fumarate hydratase gene at 1q43 predispose to dominantly inherited skin and uterine leiomyomata and leiomyosarcomas. The enzyme, which is a component of the tricarboxylic acid cycle, acts as a tumour suppressor. To evaluate fumarate hydratase in respective sporadic tumours, we analysed a series of 26 leiomyosarcomas and 129 uterine leiomyomas (from 21 patients) for somatic mutations in fumarate hydratase and allelic imbalance around 1q43. None of the 26 leiomyosarcomas harboured somatic mutations in fumarate hydratase. Fifty per cent of leiomysarcomas tested showed evidence of allelic imbalance at 1q, but this was not confined to the vicinity of fumarate hydratase. Only 5% (seven out of 129) of the leiomyomas showed allele imbalance at 1q42-q43 and no somatic mutations in fumarate hydratase were observed. Our findings indicate that mutations in fumarate hydratase do not play a major role in the development of sporadic leiomyosarcomas or uterine leiomyomas

Adult↗
PubMed2002

Characterisation of the calcium responses to histamine in capsaicin-sensitive and capsaicin-insensitive sensory neurones.

Adult rat sensory neurones were maintained in short-term tissue culture and their response to histamine was studied by monitoring changes in intracellular [Ca(2+)] with Fura-2. The proportion of histamine-sensitive neurones increased as the concentration increased from 10 microM to 10 mM. The fraction of responding cells did not change significantly over the first week in culture. About 60% of histamine-sensitive cells were insensitive to capsaicin and these cells tended to be of small diameter. The integrated calcium response to histamine was greatest at 100 microM when the response consisted of two phases: an initial short-lasting transient followed by a sustained plateau that was dependent on extracellular calcium. This response was blocked by the histamine H(1) receptor antagonist mepyramine but not by cimetidine or thioperamide which block H(2) and H(3) receptors, respectively. Moreover, application of histamine increased the intracellular concentration of inositol 1,4,5-trisphosphate -- an effect blocked by mepyramine. These data show that the response is mediated by H(1) receptors. The phospholipase C inhibitor U73122 blocked the response to 100 microM histamine and significantly reduced the fraction of cells responding to 1 mM and 10 mM histamine as did removal of extracellular calcium. A combination of U73122 and calcium-free medium abolished all responses to histamine. These data suggest that in addition to activating phospholipase C, high concentrations of histamine gate an influx of calcium that is independent of store depletion. The implications of these results for the transduction of pruritic stimuli is discussed.

Animals↗
PubMed2002

Cannabinoid 1 receptors are expressed by nerve growth factor- and glial cell-derived neurotrophic factor-responsive primary sensory neurones.

Expression of the cannabinoid 1 (CB1) receptor and its regulation were studied in the different nociceptive and non-nociceptive sub-populations of cultured primary sensory neurones of adult rats. Bandairaea simplicifolia isolectin B4 (IB4) binding and calcitonin gene-related peptide (CGRP) immunostaining were used to distinguish between the glial cell-derived neurotrophic factor (GDNF)- and nerve growth factor (NGF)-responsive nociceptive and the non-nociceptive primary sensory neurones while a specific CB1 receptor antibody was used to study the expression of the CB1 receptor protein. About half of the total number of primary sensory neurones (47+/-3.2%) cultured for 1 day in the presence of both neurotrophic factors (50 ng/ml each) showed CB1 receptor-like immunostaining, whereas 21.8+/-3.3% and 32.7+/-5.6% of the neurones showed CGRP-like immunopositivity and IB4 binding, respectively. A proportion of the CB1 receptor-like immunopositive neurones was immunostained for CGRP (31.7+/-5%) and IB4 (48.2%+/-7.5), with a minimal (1%) co-expression of CGRP and IB4 binding. About a fifth of the CB1 receptor-like immunopositive neurones did not show either CGRP-like immunostaining or IB4 binding. To find out whether CB1 receptor expression in nociceptive primary sensory neurones is regulated by GDNF or NGF, cultures were grown in the presence or absence of the neurotrophic factors for 7 days. Vanilloid receptor 1 (VR1) immunostaining was used as a control marker to monitor the effect of the neurotrophins. In cultures maintained in the presence of both factors (50 ng/ml each) 51+/-2.6% and 42.4+/-1.2% of the cells showed CB1 receptor-like and VR1-like immunostaining, respectively. In cultures grown for 7 days in the absence of either of the neurotrophic factors the relative number of VR1-like immunopositive cells decreased to 13.4+/-2.7%, whereas the relative number of CB1 receptor-like immunopositive neurones was unchanged (50.6+/-1.1%). Our data suggest that the CB1 receptor is expressed in all of the three major sub-populations of primary sensory neurones and that the CB1 receptor expression is not regulated by either NGF or GDNF.

Animals↗
PubMed2002

Mutational analysis of CD28 in coeliac disease.

BACKGROUND: Coeliac disease shows a strong genetic predisposition involving HLA-DQ2 and non-HLA components. The CD28 cell surface molecule, encoded by CD28, represents a potential candidate coeliac disease susceptibility gene. Furthermore, some studies have demonstrated linkage to the CD28/CTLA4 gene region. To investigate whether germline mutations in CD28 contribute to coeliac disease susceptibility, we have carried out a comprehensive analysis of the gene in Swedish patients with biopsy-proven disease. METHODS: Blood samples were collected from 52 children with biopsy proven coeliac disease attending one Swedish centre. DNA was extracted from lymphocytes and all exons and intron-exon boundaries of CD28 were screened for mutations. Analysis of CD28 was undertaken by a combination of conformation specific gel electrophoresis and direct sequencing. RESULTS: Three sequence variants were identified: a synonymous G-->4A substitution at position 3 of codon 35 encoding alanine, a synonymous G-->A substitution at position 3 of codon 70 encoding glycine, and a T-->C substitution at nucleotide +17 of intron 3. No pathogenic variants were detected. CONCLUSIONS: There is no evidence from this study that mutations in CD28, which lead to an altered protein, contribute to coeliac disease susceptibility.

Adolescent↗
PubMed2002

Analysis of the CTLA4 gene in Swedish coeliac disease patients.

BACKGROUND: A genetic susceptibility to coeliac disease is well established, involving HLA and non-HLA components. CTLA4 is an important regulator of T-cell function and some studies have suggested that sequence variation in the gene might be a determinant of disease susceptibility, although the evidence is conflicting. METHODS: Sixty-two children with biopsy-proven coeliac disease attending a single centre in Sweden were studied. All were genotyped for presence of the HLA-DQA1*0501, B 1*0201 alleles. Those who carried the HLA-DQ heterodimer (58/62) were genotyped for the +49 (A/G) exon I polymorphism. The transmission disequilibrium test (TDT) was used to test for association between coeliac disease and the A allele. The entire CTLA4 gene was screened for other sequence variants using a combination of conformation-sensitive gel electrophoresis and direct sequencing. RESULTS: A significant association between the exon I polymorphism and coeliac disease was observed (P = 0.02). No other sequence variants in CTLA4 were detected. CONCLUSIONS: This study provides further evidence that variation in CTLA4 is a determinant of coeliac disease susceptibility. If not mediated through the +49 (A/G) dimorphism directly, then the effect is likely to be mediated through linkage disequilibrium.

Abatacept↗
PubMed2001

CDX2 mutations do not account for juvenile polyposis or Peutz-Jeghers syndrome and occur infrequently in sporadic colorectal cancers.

Peutz-Jeghers syndrome (PJS) and juvenile polyposis (JPS) are both characterized by the presence of hamartomatous polyps and increased risk of malignancy in the gastrointestinal tract. Mutations of the LKB1 and SMAD4 genes have been shown recently to cause a number of PJS and JPS cases respectively, but there remains considerable uncharacterized genetic heterogeneity in these syndromes, particularly JPS. The mouse homologue of CDX2 has been shown to give rise to a phenotype which includes hamartomatous-like polyps in the colon and is therefore a good candidate for JPS and PJS cases which are not accounted for by the SMAD4 and LKB1 genes. By analogy with SMAD4, CDX2 is also a candidate for somatic mutation in sporadic colorectal cancer. We have screened 37 JPS families/cases without known SMAD4 mutations, 10 Peutz-Jeghers cases without known LKB1 mutations and 49 sporadic colorectal cancers for mutations in CDX2. Although polymorphic variants and rare variants of unlikely significance were detected, no pathogenic CDX2 mutations were found in any case of JPS or PJS, or in any of the sporadic cancers.

AMP-Activated Protein Kinase Kinases↗
PubMed2001

Localization of a gene (MCUL1) for multiple cutaneous leiomyomata and uterine fibroids to chromosome 1q42.3-q43.

Dominant transmission of multiple uterine and cutaneous smooth-muscle tumors is seen in the disorder multiple leiomyomatosis (ML). We undertook a genomewide screen of 11 families segregating ML and found evidence for linkage to chromosome 1q42.3-q43 (maximum multipoint LOD score 5.40). Haplotype construction and analysis of recombinations permitted the minimal interval containing the locus, which we have designated "MCUL1," to be refined to an approximately 14-cM region flanked by markers D1S517 and D1S2842. Allelic-loss studies of tumors indicated that MCUL1 may act as a tumor suppressor. Identification of MCUL1 should have wide interest, since this gene may harbor low-penetrance variants predisposing to the common form of uterine fibroids and/or may undergo somatic mutation in sporadic leiomyomata.

Chromosome Mapping↗
PubMed2001

Comprehensive analysis of SMAD4 mutations and protein expression in juvenile polyposis: evidence for a distinct genetic pathway and polyp morphology in SMAD4 mutation carriers.

Juvenile polyposis syndrome (JPS; OMIM 174900) is a rare disorder which is characterized by the presence of hamartomatous polyps throughout the gastrointestinal tract and an increased risk of gastrointestinal malignancy. Mutations of the SMAD4 gene on chromosome 18q21.1 have been shown to cause a subset of JPS cases, with estimates ranging from 20% to >50%. Characterization of the genes that cause the remainder of JPS cases relies on the certainty that SMAD4 is not the causative gene. We have undertaken a comprehensive analysis of germline SMAD4 mutations in a cohort of JPS patients to define the spectrum of mutations that cause JPS. We have analyzed a series of polyps from these patients for SMAD4 protein expression. We have also performed a blinded assessment of polyp material to look for morphological differences between polyps from patients with and without a germline SMAD4 mutation. The results indicate that almost all germline SMAD4 mutations are readily detectable by screening genomic DNA using polymerase chain reaction-based methods; SMAD4 can be excluded as the causative gene in the majority of our JPS cohort. Loss of SMAD4 expression occurs in most polyps from SMAD4 mutation carriers, even those with missense germline mutations. SMAD4 loss in polyps is, however, not a feature of cases that are not caused by SMAD4 mutations, indicating that these polyps develop along a SMAD4-independent pathway. The morphology of polyps from SMAD4 mutation carriers is subtly different from other JPS polyps, notably including a more prominent epithelial component in the former.

Amino Acid Sequence↗
PubMed2001

Demonstration of epidermal transfer from a polymer membrane using genetically marked porcine keratinocytes.

The culture of keratinocytes on flexible membranes has been proposed as a means to simplify, accelerate and improve the efficiency with which proliferating cells are delivered to full thickness or non-healing skin defects. However, there have been no studies that monitor the transfer of cells from such membranes to the wound bed. We have used a porcine model of lacZ gene marked cultured autologous keratinocyte grafting to demonstrate unambiguously the transfer of cultured cells to cutaneous wounds from the EpiGen polymer membrane developed by Smith & Nephew Group plc. Full thickness wounds enclosed within rigid chambers were first grafted with autologous de-epidermalised dermis (DED). Keratinocytes were cultured on EpiGen membranes and applied to the wound beds 7 days after the DED grafts. Epidermal remnants persist within the DED and the resultant epidermis is therefore, a mixture of wound regeneration and delivered cultured cells. Unequivocal evidence for keratinocyte transfer from the membrane was obtained through the observed macroscopic surface staining for lacZ transduced cells and lacZ positive cells detected in sections through deeper layers of epidermal tissue. This method offers a general approach for evaluating the efficiency of keratinocyte delivery using upside-down flexible membrane transfer.

Animals↗
PubMed2001

The effects of pH on the interaction between capsaicin and the vanilloid receptor in rat dorsal root ganglia neurons.

1. The vanilloid receptor of sensory neurons is a polymodal nociceptor sensitive to capsaicin, protons, heat and anandamide. Although it is known that interaction occurs between these different mediators the mechanism by which this occurs is poorly understood. In this study capsaicin elicited currents were recorded from vanilloid receptors found in adult rat isolated dorsal root ganglia (DRG) neurons under conditions of varying pH and the mechanism whereby protons can modulate this capsaicin response investigated. 2. Under whole-cell voltage clamp, modulating extracellular pH shifted the position of the capsaicin log(concentration)-response curve. Acidification from pH 9.0 to pH 5.5 lowered the EC50 values from 1150+/-250 nM to 5+/-2 nM with coincident change in the mean apparent slope factor from 2.3+/-0.3 to 0.9+/-0.2 and no change in maximal response. 3. The magnitude of the potentiation seen on reducing extracellular pH was not significantly affected by changes in extracellular calcium and magnesium concentration. 4. The response to capsaicin was not potentiated by a reduction in intracellular pH suggesting a site of action more accessible from the extracellular than the intracellular side of the membrane. 5. Potentiation by low pH was voltage independent indicating a site of action outside the membrane electric field. 6. At the single channel level, reducing extracellular pH increased channel open probability but had no significant effect on single channel conductance or open time. 7. These results are consistent with a model in which, on reducing extracellular pH, the vanilloid receptor in rat DRG neurons, changes from a state with low affinity for capsaicin to one with high affinity, coincident with a loss of cooperativity. This effect, presumed to be proton mediated, appears to involve one or more sites with pK(a) value 7.4-7.9, outside the membrane electrical field on an extracellularly exposed region of the receptor protein.

Animals↗
PubMed2001

Pharmacological differences between the human and rat vanilloid receptor 1 (VR1).

Vanilloid receptors (VR1) were cloned from human and rat dorsal root ganglion libraries and expressed in Xenopus oocytes or Chinese Hamster Ovary (CHO) cells. Both rat and human VR1 formed ligand gated channels that were activated by capsaicin with similar EC(50) values. Capsaicin had a lower potency on both channels, when measured electrophysiologically in oocytes compared to CHO cells (oocytes: rat=1.90+/-0.20 microM; human=1.90+/-0.30 microM: CHO cells: rat=0.20+/-0.06 microM; human=0.19+/-0.08 microM). In CHO cell lines co-expressing either rat or human VR1 and the calcium sensitive, luminescent protein, aequorin, the EC(50) values for capsaicin-induced responses were similar in both cell lines (rat=0.35+/-0.06 microM, human=0.53+/-0.03 microM). The threshold for activation by acidic solutions was lower for human VR1 channels than that for rat VR1 (EC(50) pH 5.49+/-0.04 and pH 5.78+/-0.09, respectively). The threshold for heat activation was identical (42 degrees C) for rat and human VR1. PPAHV was an agonist at rat VR1 (EC(50) between 3 and 10 microM) but was virtually inactive at the human VR1 (EC(50)>10 microM). Capsazepine and ruthenium red were both more potent at blocking the capsaicin response of human VR1 than rat VR1. Capsazepine blocked the human but not the rat VR1 response to low pH. Capsazepine was also more effective at inhibiting the noxious heat response of human than of rat VR1.

Amino Acid Sequence↗
PubMed2001

VR1 protein expression increases in undamaged DRG neurons after partial nerve injury.

Changes in phenotype or connectivity of primary afferent neurons following peripheral nerve injury may contribute to the hyperalgesia and allodynia associated with neuropathic pain conditions. Although earlier studies using partial nerve injury models have focused on the role of damaged fibres in the generation of ectopic discharges and pain, it is now thought that remaining undamaged fibres may be equally important. We have examined the expression of the sensory neuron-specific cation channel Vanilloid Receptor 1 (VR1), an important transducer of noxious stimuli, in three models of nerve injury in the rat, using anatomical separation or fluorescent retrograde tracers to identify damaged or undamaged sensory neurons. After total or partial sciatic nerve transection, or spinal nerve ligation, VR1-immunoreactivity (IR) was significantly reduced in the somata of all damaged dorsal root ganglion (DRG) neuronal profiles, compared to controls. However, after partial transection or spinal nerve ligation, VR1 expression was greater in the undamaged DRG somata than in controls. Unexpectedly, after L5 spinal nerve ligation, VR1-IR of the A-fibre somata increased approximately 3-fold in the uninjured L4 DRG compared to controls; a much greater increase than seen in the somata with C-fibres. Furthermore, we found that VR1-IR persisted in the transected sciatic nerve proximal to the lesion, despite its down-regulation in the damaged neuronal somata. This persistence in the nerve proximal to the lesion after nerve section, together with increased VR1 in DRG neurons left undamaged after partial nerve injury, may be crucial to the development or maintenance of neuropathic pain.

Animals↗
PubMed2001

Germline mutations in TGM2 do not contribute to coeliac disease susceptibility in the Swedish population.

OBJECTIVE: Coeliac disease (CD) shows a strong genetic predisposition involving HLA-DQ2 and non-HLA components. Tissue transglutaminase, encoded by TGM2, occupies a central role in the CD pathogenesis, necessary for the deamidation of specific glutamine residues of alpha-gliadin creating a T-cell epitope that binds with increased affinity to DQ2. To investigate whether germline mutations in TGM2 contribute to disease susceptibility we have carried out a comprehensive analysis of the gene in 52 patients with CD. DESIGN: Blood samples were collected from 52 children with biopsy proven CD attending one Swedish centre. DNA was extracted from lymphocytes and all exons and intron-exon boundaries of the TGM2 gene and the alternatively spliced form of the gene were screened for mutations. METHODS: Mutational analysis was undertaken by a combination of conformational specific gel electrophoresis and direct sequencing. RESULTS: Three novel polymorphisms were identified but no pathogenic mutations were detected. CONCLUSIONS: There is no evidence from this study that mutations in TGM2, which lead to an altered protein, contribute to CD susceptibility.

Adolescent↗
PubMed2001

A comprehensive analysis of MNG1, TCO1, fPTC, PTEN, TSHR, and TRKA in familial nonmedullary thyroid cancer: confirmation of linkage to TCO1.

About 5% of nonmedullary thyroid cancer is familial. These familial nonmedullary thyroid cancer cases are characterized by an earlier age of onset, more aggressive phenotype, and in some families a high propensity to benign thyroid disease. Little is known about the genes conferring predisposition to nonmedullary thyroid cancer. Three loci have been identified through genetic linkage: MNG1 on 14q32, TCO1 on 19p13.2, and fPTC on 1p21. In addition to these putative genes, a number of loci represent candidate familial nonmedullary thyroid cancer predisposition genes by virtue of their involvement in sporadic disease (TRKA), their role in benign disease (TSHR), and because they underlie syndromes with a risk of nonmedullary thyroid cancer (PTEN). To evaluate the roles of MNG1, TCO1, fPTC, PTEN, TSHR, and TRKA in familial nonmedullary thyroid cancer, we have carried out a comprehensive mutation and linkage analysis of these genes in 22 families. One family was linked to chromosome 19q13.2, confirming that TCO1 underlies a subset of familial nonmedullary thyroid cancer. None of the families was linked to MNG1 or fPTC, and there was no evidence to support the roles of PTEN, TSHR, or TRKA. Familial nonmedullary thyroid cancer is an emerging clinical phenotype that is genetically heterogeneous, and none of the currently identified genes accounts for the majority of families.

Adult↗