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At least 1,081 records · Page 60Linked to original sources
PubMed2005

[Gene diagnosis of X-linked agammaglobulinemia].

OBJECTIVE: X-linked agammaglobulinemia (XLA) is the most common disorder among primary immunodeficiency diseases, which is caused by mutations in the cytoplasmic Bruton's tyrosine kinase (BTK) gene, characterized by lack of mature, circulating B lymphocytes, hypogammaglobulinemia, and recurrent bacterial infections. Mutations in BTK are highly diverse. In this study, genetic analysis was performed on BTK to realize the feature of gene mutation of XLA in Mainland of China. METHODS: Seven patients from 7 different families were enrolled in the analysis. RT-PCR was employed to reverse transcript total RNA and 8 couples of primers were designed for PCR. PCR products were sequenced and the mutation sites were identified. RESULTS: Seven completely different mutations were identified in the 7 patients. All the 7 mutations located at BTK coding region. Three of the 7 mutations were located in pleckstrin homology functional area, 2 mutations located in BTK area, and in other 2 cases at Src homology 2 and Src homology 3 regions, respectively. The mutations in 2 of 7 cases were in exon 18, and the others were in exon 2, 5, 6, 8 and 10, respectively. The types of mutation included 3 missense (L11P, I590F and Y591S), two nonsense (W281X, and Q234X) mutations resulting in premature stop codons. A 10-base pair nucleotides duplicated insertion located between the nucleotide 596 and 597 resulting in frameshift, and a 8 base pair deletion at the nucleotide position 472 resulting in frameshift. Four of the 7 mutations are novel mutation types and have not been reported. Four of 7 mothers were analyzed, 3 of them were carrier and 1 was normal. CONCLUSION: The patients enrolled in this study had classical clinical features of XLA. All the 7 identified mutations located at BTK coding region and 4 of them were novel mutations. Genetic analysis can be used for diagnosis of XLA and distinguish it from other hypogammaglobulinemia.

Adolescent↗
PubMed2004

[Analysis of c-kit gene mutations in gastrointestinal stromal tumors].

OBJECTIVE: To define the frequency and spectrum of c-kit gene mutations in gastrointestinal stromal tumors (GIST). METHODS: Fifty two cases of GIST and 28 cases of other tumors were examined for mutations in exon 11, 9 and 13 of c-kit gene using PCR amplification and DNA sequencing. RESULTS: Fourteen out of 25 malignant GIST (56%), while 2 of 27 benign and borderline GIST (7.4%) revealed mutations in exon 11 of c-kit gene (P < 0.01). Most of the mutations consisted of in-frame deletion or replication from 3 to 48 bp in heterozygous and homozygous fashions, but none of the mutations disrupted the downstream reading frame of the gene. Point mutation and deletion concentrated at 550 - 570 codons but replication clustered within 570 - 585 codons. The mutation pattern in recurrence tissues was the same as the primary ones. Normal tissues adjacent to GIST with or without c-kit gene mutations showed wild type c-kit gene sequence. No mutation was found in exon 9 and 13. Neither c-kit gene expression nor gene mutations was found in 3 leiomyomas, 8 leiomyosarcomas, 2 schwannomas, 2 intra-abdomenal fibromitoses and 8 adenocarcinomas. CONCLUSION: The mutations in exon 11 of c-kit gene might partially represent one of the molecular mechanisms of GIST. It can be used as a marker for distinguishing benignancy and malignancy of GIST. The mutations did not involve the reading frame. Except for long frame deletion, most mutations also did not affect protein expression. Mutation of c-kit gene in GIST provides a new genotypic marker to distinguish GIST from authentic leiomyomas, leiomyosarcomas, schwannomas and etc.

Base Sequence↗
PubMed1993

Linkage disequilibrium between the fragile X mutation and two closely linked CA repeats suggests that fragile X chromosomes are derived from a small number of founder chromosomes.

In order to investigate the origin of mutations responsible for the fragile X syndrome, two polymorphic CA repeats, one at 10 kb (FRAXAC2) and the other at 150 kb (DXS548) from the mutation target, were analyzed in normal and fragile X chromosomes. Contrary to observations made in myotonic dystrophy, fragile X mutations were not strongly associated with a single allele at the marker loci. However, significant differences in allelic and haplotypic distributions were observed between normal and fragile X chromosomes, indicating that a limited number of primary events may have been at the origin of most present-day fragile X chromosomes in Caucasian populations. We propose a putative scheme with six founder chromosomes from which most of the observed fragile X-linked haplotypes can be derived directly or by a single event at one of the marker loci, either a change of one repeat unit or a recombination between DXS548 and the mutation target. Such founder chromosomes may have carried a number of CGG repeats in an upper-normal range, from which recurrent multistep expansion mutations have arisen.

Alleles↗
PubMed2003

Recurrent vomiting and ethylmalonic aciduria associated with rare mutations of the short-chain acyl-CoA dehydrogenase gene.

We report identification of short-chain acyl-CoA dehydrogenase (SCAD) deficiency in a 12-year-old boy who suffered from recurrent attacks of vomiting once or twice a year from infancy. Growth and development were normal and there were no muscular symptoms. Metabolic screening was performed during a hospitalization at 8 years of age and revealed an increased excretion of ethylmalonic acid (EMA; 45-80 mmol/mol creatinine, normal 0.2-6.6), suggesting a degradation defect of short-chain fatty acids. An increased n-butyrylcarnitine was found in freshly collected serum (0.9 micromol/L; normal <0.4) but not in dry blood spots. Neither of the frequent SCAD gene variants 625G>A and 511C>T was present, but direct sequencing of the promoter and coding regions of the SCAD gene revealed that the patient had mutations on both alleles: 417G>C (Trpl15Cys) and 1095G>T (Gln341His). Neither mutation has been described before in compound heterozygosity or homozygosity. Enzymatic investigations subsequently confirmed a defect of SCAD in both fibroblasts and muscle extracts. Furthermore, expression studies of both mutations demonstrated impaired enzyme function or structure. To our knowledge, this case is the first description of a patient with proven SCAD deficiency presenting with recurrent emesis but without other symptoms, and emphasizes the wide clinical phenotype of this disorder.

Alleles↗
PubMed2006

Novel FGFR3 mutations creating cysteine residues in the extracellular domain of the receptor cause achondroplasia or severe forms of hypochondroplasia.

Achondroplasia (ACH) and hypochondroplasia (HCH) are two autosomal-dominant skeletal disorders caused by recurrent missense FGFR3 mutations in the transmembrane (TM) and tyrosine kinase 1 (TK1) domains of the receptor. Although 98% of ACH cases are accounted for by a single G380R substitution in the TM, a common mutation (N540K) in the TK1 region is detected in only 60-65% of HCH cases. The aim of this study was to determine whether the frequency of mutations in patients with HCH was the result of incomplete mutation screening or genetic heterogeneity. Eighteen exons of the FGFR3 gene were entirely sequenced in a cohort of 25 HCH and one ACH patients in whom common mutations had been excluded. Seven novel missense FGFR3 mutations were identified, one causing ACH and six resulting in HCH. Six of these substitutions were located in the extracellular region and four of them creating additional cysteine residues, were associated with severe phenotypes. No mutations were detected in 19 clinically diagnosed HCH patients. Our results demonstrate that the spectrum of FGFR3 mutations causing short-limb dwarfism is wider than originally recognised and emphasise the requirement for complete screening of the FGFR3 gene if appropriate genetic counselling is to be offered to patients with HCH or ACH lacking the most common mutations and their families.

Achondroplasia↗
PubMed2001

Relevance of Ki-67 antigen expression and K-ras mutation in colorectal liver metastases.

AIMS: The liver is a frequent site of metastases from colorectal cancer. While these lesions are potentially amenable to surgical resection, they are usually very aggressive, and recurrence is frequent. Mutations of the proto-oncogene K- ras are thought to impart a strong growth signal to tumour cells and are closely associated with the development of malignancies of the colon and rectum. Hepatic metastases from colorectal cancer have notably elevated proliferative rates. The present study was performed to investigate the relationship between proliferation or K- ras mutation and prognosis following curative resection of colorectal liver metastases. METHODS: Colorectal liver metastases from 41 patients undergoing curative hepatic resection were examined for proliferation status and presence of K- ras mutations. The proliferative activity was assessed by Ki-67 immunohistochemistry. DNA from the same tissue samples was screened for point mutations in codon 12 of the K- ras gene using a novel microplate-based allelic-specific hybridization assay. Ki-67 scores and K- ras status were then related with patient survival as determined through retrospective analysis. RESULTS: Median survival was 40 months. Patients with high Ki-67 scores (> or = 50%) had significantly shorter median survival compared with those with low scores (30 vs 44 months, log-rank P=0.02). A high Ki-67 score was an independent negative prognostic factor by multivariate regression analysis (relative risk=3.04, P=0.036). K- ras point mutations were detected in 6/41 patients (15%), but mutational status did not correlate with Ki-67 score or survival. CONCLUSIONS: These findings suggest that the tumour proliferative index is a useful predictor of aggressive tumour behaviour and an indicator of patient survival. The presence of K- ras mutations does not appear to correlate with tumour proliferation status or patient survival.

Adult↗
PubMedDate not supplied

p53 protein expression in human breast carcinoma: lack of prognostic potential for recurrence of the disease.

Mutations of the p53 gene are now known to be one of the most commonly detected genetic defects among human cancers. Because of its stability, the mutant p53 protein can be detected by immunohistochemical methods. Overexpression of the mutant p53 protein has been suggested as a prognostic indicator for the recurrence of breast cancer. Using a monoclonal antibody to p53, formalin-fixed, paraffin embedded breast cancer tissues retrieved from up to 10 years storage in the archival files were processed for staining. A total of 125 cases was examined p53 overexpression was identified by brown nuclear staining. Clinical parameters studied included estrogen and progesterone receptors, tumor size, nodal status, obesity, stage, and histopathological grade. The only significant association seen for p53 overexpression was with negative estrogen and progesterone receptors. All other clinical parameters studied were independent of p53 overexpression. Thus, p53 overexpression does not appear to be a useful prognostic indicator for recurrence and survival in human breast cancer.

Adult↗
PubMed1995

Factor V Leiden and risks of recurrent idiopathic venous thromboembolism.

BACKGROUND: Whether Leiden mutation in the gene coding for coagulation factor V is associated with recurrent idiopathic venous thromboembolism (VTE) is unknown, but such data are necessary to evaluate the merits of genetic screening in secondary prevention of thromboembolic disease. METHODS AND RESULTS: Among 14,916 apparently healthy men who provided DNA samples and were followed in the Physicians' Health Study through August 1994, 77 suffered an idiopathic VTE. These 77 men were followed for an additional average period of 68.3 months, during which time 11 (14.3%) suffered a recurrent idiopathic VTE. Factor V Leiden status was assessed in these men, and incidence rates of recurrence were calculated by genotype. All recurrent events occurred after cessation of anticoagulation. Seven recurrences occurred among 63 genetically unaffected subjects (11.1%; incidence rate, 1.82 per 100 person-years), while four occurred among those 14 heterozygous for factor V Leiden (28.6%; incidence rate, 7.46 per 100 person-years). Thus, factor V Leiden was associated with a fourfold to fivefold increase in risk of recurrent VTE (crude relative risk, 4.1; P = .04; age- and smoking-adjusted relative risk, 4.7; P = .047). There was no difference in mean time between index and recurrent events by genotype. Among heterozygous men, 76% of recurrent events were attributable to mutation. CONCLUSIONS: In prospective evaluation of 77 men with a history of idiopathic VTE, factor V Leiden was associated with a fourfold to fivefold increased risk of recurrent thrombosis. These data raise the possibility that patients with VTE affected by factor V Leiden may require more prolonged anticoagulation to prevent recurrent disease compared with those without mutation.

Adult↗
PubMed2005

Functional analysis of a new splice site mutation, c.605-3C>A, in the cystinuria gene SLC7A9 leading to exon skipping.

Cystinuria is a hereditary disorder of cystine and dibasic amino acid transport across the luminal membrane of renal tubules and intestine, resulting in recurrent nephrolithiasis. While mutations in the SLC3A1 gene cause type I cystinuria, patients with non-type I cystinuria carry mutations in the SLC7A9 gene. Up to now, more than 80 mutations in SLC3A1 and 50 in SLC7A9 have been reported in the literature. While deletions, duplications, and truncating mutations can often unambiguously classified to be pathogenic, the functional relevance of base pair substitutions is often difficult to predict. To determine the functional relevance of a new splice site mutation in intron 5 of SLC7A9, c.605-3C>A, we transfected COS7 cells with expression constructs containing the wild-type and mutant allele, respectively. cDNAs derived from the resulting SLC7A9 mRNAs were sequenced. By this approach we could demonstrate that the mutant allele c.605-3A causes exon skipping and therefore represents a splice site mutation. To the best of our knowledge, this is the first splice site mutation in a cystinuria gene with a proven functional consequence.

Amino Acid Transport Systems, Basic↗
PubMed1998

p53 protein accumulation predicts poor response to tamoxifen therapy of patients with recurrent breast cancer.

PURPOSE: Mutations of the p53 gene are frequently observed in primary breast cancer and accumulation of p53 protein has been used as a surrogate marker of p53 inactivation. Previous studies have shown that p53 accumulation is related to poor prognosis in primary breast cancer. We studied whether p53 protein accumulation is a predictive factor for response to tamoxifen treatment in patients with recurrent breast cancer. PATIENTS AND METHODS: Levels of p53, estrogen receptor (ER), progesterone receptor (PgR), and urokinase-type plasminogen activator (uPA) were assayed in cytosolic extracts derived from primary tumors of 401 tamoxifen-naive patients who developed recurrent disease. All patients in the study received tamoxifen therapy upon relapse (median follow-up, 69 months). Association of tested factors with response to tamoxifen treatment was studied by logistic regression analysis, and with survival after the start of treatment by Cox univariate and multivariate regression analysis. RESULTS: p53 levels (median, 0.23 ng/mg protein) were not related to ER or PgR levels, but positively correlated with uPA (P < .0001). In a test for trend, we observed an association of p53 protein levels with response to tamoxifen therapy. When dichotomized (at the median value), 42% in the p53-high versus 56% in the p53-low group showed a response. In multivariate analysis, including patient and tumor characteristics, p53 accumulation retained significance with the rate of response (odds ratio [OR], 0.48; 95% confidence interval [CI], 0.31 to 0.74; P < .001). Also in multivariate analysis, reduced survival after the start of tamoxifen therapy was observed in the p53-high group (relative hazards rate [RHR], 1.56, 95% CI, 1.17 to 2.10; P = .002). A statistically significant association between p53 levels and decreased tamoxifen response was seen only in the subset of patients whose tumors expressed low levels of ER or PgR (<75 fmol/mg protein). CONCLUSION: Measurement of primary tumor p53 levels may be effective in predicting response to tamoxifen therapy in recurrent breast disease. However, more confirming studies on the association between p53 protein accumulation and response to antiestrogen therapy are needed before tumor p53 levels can be used in routine clinical practice.

Adult↗
PubMed2004

Allelic genes of blood group antigens: a source of human mutations and cSNPs documented in the Blood Group Antigen Gene Mutation Database.

In this report, we analyze data assembled in the Blood Group Antigen Gene Mutation Database (www.bioc.aecom.yu.edu/bgmut/index.htm), which describes sequence information on human genes associated with expression of the various serologically-determined blood group phenotypes. The database documents 38 genetic loci and a total of 624 alleles that together encode a large repertoire of proteins and constitute 27 serologically-defined blood group systems. Analysis of sequence variation patterns across alleles of a number of genes is focused on their molecular profiles, including mutational sites and recurrence, patterns of gene rearrangements in duplicated gene families, correlation of predicted location of epitopes in extracellular loops with sites of alterations, and effects of mutations on protein expression. That information, and the relative ease of identifying individuals bearing variant alleles, has led to the proposal that genes encoding blood group antigens are an important and unique resource for studies of human DNA variation. Another focus is on mutations in regions that encode the antigenic epitopes and on their occurrence in world populations. These mutations may be viewed as coding single nucleotide polymorphisms (cSNPs). We propose that one group of these cSNPs, which are known to occur with significant frequency in all world populations, could serve as well-validated genetic markers. In addition, specific mutations in a number of "low incidence" and rare alleles could serve as cSNPs specific for a given population. The allelic frequencies of these mutations and knowledge of their world-wide occurrence add a valuable dataset to the existing cSNP pools documented in SNP databases.

Alleles↗
PubMed2006

Analysis of RNA splicing defects in PITX2 mutants supports a gene dosage model of Axenfeld-Rieger syndrome.

BACKGROUND: Axenfeld-Rieger syndrome (ARS) is associated with mutations in the PITX2 gene that encodes a homeobox transcription factor. Several intronic PITX2 mutations have been reported in Axenfeld-Rieger patients but their effects on gene expression have not been tested. METHODS: We present two new families with recurrent PITX2 intronic mutations and use PITX2c minigenes and transfected cells to address the hypothesis that intronic mutations effect RNA splicing. Three PITX2 mutations have been analyzed: a G>T mutation within the AG 3' splice site (ss) junction associated with exon 4 (IVS4-1G>T), a G>C mutation at position +5 of the 5' (ss) of exon 4 (IVS4+5G>C), and a previously reported A>G substitution at position -11 of 3'ss of exon 5 (IVS5-11A>G). RESULTS: Mutation IVS4+5G>C showed 71% retention of the intron between exons 4 and 5, and poorly expressed protein. Wild-type protein levels were proportionally expressed from correctly spliced mRNA. The G>T mutation within the exon 4 AG 3'ss junction shifted splicing exclusively to a new AG and resulted in a severely truncated, poorly expressed protein. Finally, the A>G substitution at position -11 of the 3'ss of exon 5 shifted splicing exclusively to a newly created upstream AG and resulted in generation of a protein with a truncated homeodomain. CONCLUSION: This is the first direct evidence to support aberrant RNA splicing as the mechanism underlying the disorder in some patients and suggests that the magnitude of the splicing defect may contribute to the variability of ARS phenotypes, in support of a gene dosage model of Axenfeld-Rieger syndrome.

Abnormalities, Multiple↗
PubMed1998

Long-term, low-dose warfarin among venous thrombosis patients with and without factor V Leiden mutation: rationale and design for the Prevention of Recurrent Venous Thromboembolism (PREVENT) trial.

Standard therapy for patients with deep venous thrombosis and pulmonary embolism typically includes anticoagulation for a 3-6 month period with full dose warfarin. However, patients following this regimen experience high rates of recurrent thrombosis, re-hospitalization and mortality in the years immediately following cessation of anticoagulation. This is true for patients at average risk of disease recurrence, and for patients at elevated risk due to the presence of inherited defects of anticoagulation such as factor V Leiden mutation. Unfortunately, no clinical regimen currently available has proven to have sufficient benefit to support long-term prophylaxis. In particular, full dose warfarin is associated with substantially increased risks of hemorrhage when used on a long term basis. In contrast, while targeted low-dose warfarin (INR 1.5-2.0) is safe for long-term therapy, the efficacy of this approach in the prevention of recurrent venous thromboembolic disease has remained untested. The Prevention of Recurrent Venous Thromboembolism (PREVENT) trial will evaluate the efficacy of prolonged treatment with low-dose warfarin in the secondary prevention of venous thromboembolism (VTE). Patients with a history of documented idiopathic venous thrombosis who have completed a standard course of anticoagulation therapy will be enrolled in a randomized, double-blind, placebo-controlled trial comparing usual care plus targeted low-dose warfarin to usual care plus placebo for a period of up to 4 years. Trial endpoints will include recurrent VTE, major bleeding episodes and all-cause mortality in the total patient population and separately in those patients with factor V Leiden. The potential clinical impact of the PREVENT trial is broad since a positive finding would strongly support chronic low-intensity anticoagulation among patients with venous thrombosis who are at risk for recurrence following cessation of standard outpatient anticoagulation.

Adult↗
PubMed2001

Inhibiting mutations in the transforming growth factor beta type 2 receptor in recurrent human breast cancer.

Members of the transforming growth factor beta (TGF-beta) family are potent inhibitors of the growth of many epithelial cell types. Transmembrane signaling by TGF-beta occurs via a complex of the serine/threonine kinases TGF-beta type 1 receptor and TGF-beta type 2 receptor (TGFBR2), and inactivating mutations in the latter have recently been detected in some primary tumors and in several types of tumor-derived cell lines. The most common mutations that have been identified in TGFBR2 are frameshifts in a repetitive polyadenine region in replication error-positive colorectal carcinomas that result in a truncated protein and absence of receptor expression at the cell surface. A number of point mutations in the highly conserved serine/threonine kinase domain of TGFBR2 have also been reported, some of which have been correlated with either loss of trans-phosphorylation of TGF-beta type 1 receptor or constitutive activation of trans-phosphorylation. No TGFBR2 mutations have been reported in human breast tumors, but anomalous expression of TGF-beta in breast carcinomas suggests that TGF-beta signaling may be defective. We have therefore systematically examined unmatched sets of 17 primary and 17 recurrent breast tumor samples for mutations in TGFBR2, restricted to those regions of the gene in which mutations have previously been reported. None of the previously reported mutations was detected, but four novel mutations (V387M, N435S, V447A, and L452M) were found in the kinase domain in recurrent tumors. No mutations were detected in primary tumors. TGF-beta signaling was significantly inhibited by each of the N435S, V447A, and L452M mutations.

Animals↗
PubMed2003

Recurrent familial hypocalcemia due to germline mosaicism for an activating mutation of the calcium-sensing receptor gene.

De novo activating mutations in the calcium-sensing receptor (CASR) gene are a common cause of sporadic isolated hypoparathyroidism. Here, we describe a family in which two affected siblings were found to be heterozygous for a novel F788L mutation in the fifth transmembrane domain encoded by exon 7 of the CASR. Both parents and the third sibling were clinically unaffected and genotypically normal by direct sequencing of their leukocyte exon 7 PCR amplicons. However, the mother was revealed to be a mosaic for the mutation by sequence analysis of multiple subclones as well as denaturing HPLC of the CASR exon 7 leukocyte PCR product. A functional analysis of the mutation was performed by transiently transfecting wild-type and mutant CASRs tagged with a c-Myc epitope in human embryonic kidney (HEK293) cells. The mutant CASR was expressed at a similar level as the wild type. The F788L mutant produced a significant shift to the left relative to the wild-type CASR in the MAPK response to increasing extracellular calcium concentrations. This is the first report of mosaicism for an activating CASR mutation and suggests that care should be exercised in counseling for risks of recurrence in a situation where a de novo mutation appears likely.

Adolescent↗
PubMed2000

[Prognostic factors of breast cancer]

OBJECTIVES: Characterization of breast cancers by various tumour markers which are appropriate for the identification of high risk groups. Markers related to the metastasis cascade and tumour recurrence have been investigated. MATERIALS AND METHODS: RT-PCR was used to determine the expression of cytokeratin 20 in the bone marrow and sentinel lymph node of breast cancer patients (n=45). The expression of HER2, Cadherin E, Cyclin D, Bcl2 and Bax has been evaluated by Western blot (n=744 invasive ductal carcinomas and 117 invasive lobular carcinomas, 124 recurrent breast cancers). Mutations of p53, APC and beta Catenin genes were detected by PCR-SSCP method. RESULTS: Expression of cytokeratin 20 was found in 30% of the bone marrow samples indicating the presence of micrometastasis. The level of Cyclin D, HER2 and Bcl2 is elevated four-fold in the recurrent breast cancers. The metastasis of invasive ductal carcinomas is accompained by high frequency of p53 mutations (24%) and APC mutations (18%). The invasive lobular carcinomas could be characterized with low frequency of p53 mutation (3%), low level of Cadherin E and high level of catenin beta. CONCLUSIONS: Identification of micrometastasis can promote the development of therapeutic strategy. Evaluation of HER2 level and determination of p53 mutations contribute to the identification of high risk patients. Our results suggest that the progression of invasive ductal carcinomas depends on the APC mutations, while metastasis of invasive lobular carcinomas depends on beta catenin mutations.

Journal Article↗