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1.
Cancer Res ; 80(17): 3593-3605, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32641407

RESUMO

BRCA2 is a clinically actionable gene implicated in breast and ovarian cancer predisposition that has become a high priority target for improving the classification of variants of unknown significance (VUS). Among all BRCA2 VUS, those causing partial/leaky splicing defects are the most challenging to classify because the minimal level of full-length (FL) transcripts required for normal function remains to be established. Here, we explored BRCA2 exon 3 (BRCA2e3) as a model for calibrating variant-induced spliceogenicity and estimating thresholds for BRCA2 haploinsufficiency. In silico predictions, minigene splicing assays, patients' RNA analyses, a mouse embryonic stem cell (mESC) complementation assay and retrieval of patient-related information were combined to determine the minimal requirement of FL BRCA2 transcripts. Of 100 BRCA2e3 variants tested in the minigene assay, 64 were found to be spliceogenic, causing mild to severe RNA defects. Splicing defects were also confirmed in patients' RNA when available. Analysis of a neutral leaky variant (c.231T>G) showed that a reduction of approximately 60% of FL BRCA2 transcripts from a mutant allele does not cause any increase in cancer risk. Moreover, data obtained from mESCs suggest that variants causing a decline in FL BRCA2 with approximately 30% of wild-type are not pathogenic, given that mESCs are fully viable and resistant to DNA-damaging agents in those conditions. In contrast, mESCs producing lower relative amounts of FL BRCA2 exhibited either null or hypomorphic phenotypes. Overall, our findings are likely to have broader implications on the interpretation of BRCA2 variants affecting the splicing pattern of other essential exons. SIGNIFICANCE: These findings demonstrate that BRCA2 tumor suppressor function tolerates substantial reduction in full-length transcripts, helping to determine the pathogenicity of BRCA2 leaky splicing variants, some of which may not increase cancer risk.

2.
Cancer Res ; 80(7): 1374-1386, 2020 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-32046981

RESUMO

Germline nonsense and canonical splice site variants identified in disease-causing genes are generally considered as loss-of-function (LoF) alleles and classified as pathogenic. However, a fraction of such variants could maintain function through their impact on RNA splicing. To test this hypothesis, we used the alternatively spliced BRCA2 exon 12 (E12) as a model system because its in-frame skipping leads to a potentially functional protein. All E12 variants corresponding to putative LoF variants or predicted to alter splicing (n = 40) were selected from human variation databases and characterized for their impact on splicing in minigene assays and, when available, in patient lymphoblastoid cell lines. Moreover, a selection of variants was analyzed in a mouse embryonic stem cell-based functional assay. Using these complementary approaches, we demonstrate that a subset of variants, including nonsense variants, induced in-frame E12 skipping through the modification of splice sites or regulatory elements and, consequently, led to an internally deleted but partially functional protein. These data provide evidence, for the first time in a cancer-predisposition gene, that certain presumed null variants can retain function due to their impact on splicing. Further studies are required to estimate cancer risk associated with these hypomorphic variants. More generally, our findings highlight the need to exercise caution in the interpretation of putative LoF variants susceptible to induce in-frame splicing modifications. SIGNIFICANCE: This study presents evidence that certain presumed loss-of-function variants in a cancer predisposition gene can retain function due to their direct impact on RNA splicing.


Assuntos
Processamento Alternativo , Proteína BRCA2/genética , Predisposição Genética para Doença , Síndrome Hereditária de Câncer de Mama e Ovário/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Linhagem Celular Tumoral , Células-Tronco Embrionárias , Éxons/genética , Feminino , Humanos , Mutação com Perda de Função , Masculino , Camundongos , Pessoa de Meia-Idade , Linhagem , Polimorfismo de Nucleotídeo Único , Proteínas Recombinantes/genética
3.
BMC Genomics ; 21(1): 86, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31992191

RESUMO

BACKGROUND: Branch points (BPs) map within short motifs upstream of acceptor splice sites (3'ss) and are essential for splicing of pre-mature mRNA. Several BP-dedicated bioinformatics tools, including HSF, SVM-BPfinder, BPP, Branchpointer, LaBranchoR and RNABPS were developed during the last decade. Here, we evaluated their capability to detect the position of BPs, and also to predict the impact on splicing of variants occurring upstream of 3'ss. RESULTS: We used a large set of constitutive and alternative human 3'ss collected from Ensembl (n = 264,787 3'ss) and from in-house RNAseq experiments (n = 51,986 3'ss). We also gathered an unprecedented collection of functional splicing data for 120 variants (62 unpublished) occurring in BP areas of disease-causing genes. Branchpointer showed the best performance to detect the relevant BPs upstream of constitutive and alternative 3'ss (99.48 and 65.84% accuracies, respectively). For variants occurring in a BP area, BPP emerged as having the best performance to predict effects on mRNA splicing, with an accuracy of 89.17%. CONCLUSIONS: Our investigations revealed that Branchpointer was optimal to detect BPs upstream of 3'ss, and that BPP was most relevant to predict splicing alteration due to variants in the BP area.


Assuntos
Íntrons , Precursores de RNA , Sítios de Splice de RNA , Processamento de RNA , Processamento Alternativo , Biologia Computacional/métodos , Humanos , Motivos de Nucleotídeos , Matrizes de Pontuação de Posição Específica , Processamento Pós-Transcricional do RNA , Curva ROC , Reprodutibilidade dos Testes
5.
Hum Mutat ; 40(9): 1557-1578, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31131967

RESUMO

The multifactorial likelihood analysis method has demonstrated utility for quantitative assessment of variant pathogenicity for multiple cancer syndrome genes. Independent data types currently incorporated in the model for assessing BRCA1 and BRCA2 variants include clinically calibrated prior probability of pathogenicity based on variant location and bioinformatic prediction of variant effect, co-segregation, family cancer history profile, co-occurrence with a pathogenic variant in the same gene, breast tumor pathology, and case-control information. Research and clinical data for multifactorial likelihood analysis were collated for 1,395 BRCA1/2 predominantly intronic and missense variants, enabling classification based on posterior probability of pathogenicity for 734 variants: 447 variants were classified as (likely) benign, and 94 as (likely) pathogenic; and 248 classifications were new or considerably altered relative to ClinVar submissions. Classifications were compared with information not yet included in the likelihood model, and evidence strengths aligned to those recommended for ACMG/AMP classification codes. Altered mRNA splicing or function relative to known nonpathogenic variant controls were moderately to strongly predictive of variant pathogenicity. Variant absence in population datasets provided supporting evidence for variant pathogenicity. These findings have direct relevance for BRCA1 and BRCA2 variant evaluation, and justify the need for gene-specific calibration of evidence types used for variant classification.


Assuntos
Proteína BRCA1/genética , Proteína BRCA2/genética , Biologia Computacional/métodos , Mutação de Sentido Incorreto , Neoplasias/diagnóstico , Processamento Alternativo , Detecção Precoce de Câncer , Feminino , Predisposição Genética para Doença , Humanos , Funções Verossimilhança , Masculino , Herança Multifatorial , Neoplasias/genética
7.
Nucleic Acids Res ; 46(15): 7913-7923, 2018 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-29750258

RESUMO

Variant interpretation is the key issue in molecular diagnosis. Spliceogenic variants exemplify this issue as each nucleotide variant can be deleterious via disruption or creation of splice site consensus sequences. Consequently, reliable in silico prediction of variant spliceogenicity would be a major improvement. Thanks to an international effort, a set of 395 variants studied at the mRNA level and occurring in 5' and 3' consensus regions (defined as the 11 and 14 bases surrounding the exon/intron junction, respectively) was collected for 11 different genes, including BRCA1, BRCA2, CFTR and RHD, and used to train and validate a new prediction protocol named Splicing Prediction in Consensus Elements (SPiCE). SPiCE combines in silico predictions from SpliceSiteFinder-like and MaxEntScan and uses logistic regression to define optimal decision thresholds. It revealed an unprecedented sensitivity and specificity of 99.5 and 95.2%, respectively, and the impact on splicing was correctly predicted for 98.8% of variants. We therefore propose SPiCE as the new tool for predicting variant spliceogenicity. It could be easily implemented in any diagnostic laboratory as a routine decision making tool to help geneticists to face the deluge of variants in the next-generation sequencing era. SPiCE is accessible at (https://sourceforge.net/projects/spicev2-1/).


Assuntos
Biologia Computacional/métodos , Simulação por Computador , Variação Genética , Sítios de Splice de RNA/genética , Processamento de RNA , Proteína BRCA1/genética , Proteína BRCA2/genética , Neoplasias da Mama/diagnóstico , Neoplasias da Mama/genética , Feminino , Humanos , Cooperação Internacional , Internet , Neoplasias Ovarianas/diagnóstico , Neoplasias Ovarianas/genética , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
8.
Eur J Hum Genet ; 25(10): 1147-1154, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28905878

RESUMO

Interpretation of variants of unknown significance (VUS) is a major challenge for laboratories performing molecular diagnosis of hereditary breast and ovarian cancer (HBOC), especially considering that many genes are now known to be involved in this syndrome. One important way these VUS can have a functional impact is through their effects on RNA splicing. Here we present a custom RNA-Seq assay plus bioinformatics and biostatistics pipeline to analyse specifically alternative and abnormal splicing junctions in 11 targeted HBOC genes. Our pipeline identified 14 new alternative splices in BRCA1 and BRCA2 in addition to detecting the majority of known alternative spliced transcripts therein. We provide here the first global splicing pattern analysis for the other nine genes, which will enable a comprehensive interpretation of splicing defects caused by VUS in HBOC. Previously known splicing alterations were consistently detected, occasionally with a more complex splicing pattern than expected. We also found that splicing in the 11 genes is similar in blood and breast tissue, supporting the utility and simplicity of blood splicing assays. Our pipeline is ready to be integrated into standard molecular diagnosis for HBOC, but it could equally be adapted for an integrative analysis of any multigene disorder.


Assuntos
Processamento Alternativo , Neoplasias da Mama/genética , Testes Genéticos/métodos , Neoplasias Ovarianas/genética , Análise de Sequência de RNA/métodos , Proteína BRCA1/genética , Proteína BRCA2/genética , Neoplasias da Mama/diagnóstico , Feminino , Genoma Humano , Humanos , Neoplasias Ovarianas/diagnóstico
9.
Int J Cancer ; 138(4): 891-900, 2016 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-26317927

RESUMO

Therapeutic strategies targeting Homologous Recombination Deficiency (HRD) in breast cancer requires patient stratification. The LST (Large-scale State Transitions) genomic signature previously validated for triple-negative breast carcinomas (TNBC) was evaluated as biomarker of HRD in luminal (hormone receptor positive) and HER2-overexpressing (HER2+) tumors. The LST genomic signature related to the number of large-scale chromosomal breakpoints in SNP-array tumor profile was applied to identify HRD in in-house and TCGA sets of breast tumors, in which the status of BRCA1/2 and other genes was also investigated. In the in-house dataset, HRD was predicted in 5% (20/385) of sporadic tumors luminal or HER2+ by the LST genomic signature and the inactivation of BRCA1, BRCA2 or RAD51C confirmed this prediction in 75% (12/16) of the tested cases. In 14% (6/43) of tumors occurring in BRCA1/2 mutant carriers, the corresponding wild-type allele was retained emphasizing the importance of determining the tumor status. In the TCGA luminal and HER2+ subtypes HRD incidence was estimated at 5% (18/329, 95%CI: 5-8%) and 2% (1/59, 95%CI: 2-9%), respectively. In TNBC cisplatin-based neo-adjuvant clinical trials, HRD is shown to be a necessary condition for cisplatin sensitivity. This analysis demonstrates the high performance of the LST genomic signature for HRD detection in breast cancers, which suggests its potential as a biomarker for genetic testing and patient stratification for clinical trials evaluating platinum salts and PARP inhibitors.


Assuntos
Biomarcadores Tumorais/genética , Neoplasias da Mama/genética , Carcinoma/genética , Reparo de DNA por Recombinação/genética , Transcriptoma/genética , Neoplasias da Mama/patologia , Carcinoma/patologia , Quebra Cromossômica , Feminino , Genes BRCA2 , Humanos , Análise de Sequência com Séries de Oligonucleotídeos , Receptor ErbB-2/genética
10.
BMC Cancer ; 13: 484, 2013 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-24139550

RESUMO

BACKGROUND: Most currently known breast cancer predisposition genes play a role in DNA repair by homologous recombination. Recent studies conducted on RAD51 paralogs, involved in the same DNA repair pathway, have identified rare germline mutations conferring breast and/or ovarian cancer predisposition in the RAD51C, RAD51D and XRCC2 genes. The present study analysed the five RAD51 paralogs (RAD51B, RAD51C, RAD51D, XRCC2, XRCC3) to estimate their contribution to breast and ovarian cancer predisposition. METHODS: The study was conducted on 142 unrelated patients with breast and/or ovarian cancer either with early onset or with a breast/ovarian cancer family history. Patients were referred to a French family cancer clinic and had been previously tested negative for a BRCA1/2 mutation. Coding sequences of the five genes were analysed by EMMA (Enhanced Mismatch Mutation Analysis). Detected variants were characterized by Sanger sequencing analysis. RESULTS: Three splicing mutations and two likely deleterious missense variants were identified: RAD51B c.452 + 3A > G, RAD51C c.706-2A > G, RAD51C c.1026 + 5_1026 + 7del, RAD51B c.475C > T/p.Arg159Cys and XRCC3 c.448C > T/p.Arg150Cys. No RAD51D and XRCC2 gene mutations were detected. These mutations and variants were detected in families with both breast and ovarian cancers, except for the RAD51B c.475C > T/p.Arg159Cys variant that occurred in a family with 3 breast cancer cases. CONCLUSIONS: This study identified the first RAD51B mutation in a breast and ovarian cancer family and is the first report of XRCC3 mutation analysis in breast and ovarian cancer. It confirms that RAD51 paralog mutations confer breast and ovarian cancer predisposition and are rare events. In view of the low frequency of RAD51 paralog mutations, international collaboration of family cancer clinics will be required to more accurately estimate their penetrance and establish clinical guidelines in carrier individuals.


Assuntos
Neoplasias da Mama/genética , Proteínas de Ligação a DNA/genética , Predisposição Genética para Doença , Mutação em Linhagem Germinativa , Neoplasias da Mama/metabolismo , Análise Mutacional de DNA , Proteínas de Ligação a DNA/metabolismo , Éxons , Feminino , Síndrome Hereditária de Câncer de Mama e Ovário/genética , Síndrome Hereditária de Câncer de Mama e Ovário/metabolismo , Humanos , Imuno-Histoquímica , Linhagem , Processamento de RNA
11.
Int J Cancer ; 133(12): 2834-42, 2013 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-23754601

RESUMO

BRCA2 is the major high-penetrance predisposition gene for luminal (estrogen receptor [ER] positive) breast cancers. However, many BRCA2 mutant carriers lack family history of breast/ovarian cancers and do not benefit from genetic testing. Specific genomic features associated with BRCA2 inactivation in tumors could help identify patients for whom a genetic test for BRCA2 may be proposed. A series of ER-positive invasive ductal carcinomas (IDCs) including 30 carriers of BRCA2 mutations and 215 control cases was studied by single-nucleotide polymorphism (SNP) arrays. Cases and controls were stratified by grade and HER2 status. Independently, 7 BRCA2 and 51 control cases were used for validation. Absolute copy number and Loss of heterozygosity (LOH) profiles were obtained from SNP arrays by the genome alteration print (GAP) method. BRCA2 tumors were observed to display a discriminatively greater number of chromosomal breaks calculated after filtering out and smoothing <3 Mb variations. This argues for a BRCA2-associated genomic instability responsible for long-segment aberrations. Co-occurrence of two genomic features-LOH of 13q13 and 14q32-was found to predict BRCA2 status with 90% of sensitivity and 87% of specificity in discovery series of high-grade HER2-negative IDCs and 100% of sensitivity and 88% of specificity in an independent series of 58 IDCs. Estimated positive predictive value was 17.2% (confidence interval: 6.7-33.5) in the whole series. In conclusion, the simplified BRCA2 classifier based on the co-occurrence of LOH at 13q13 and 14q32 could provide an indication to test for BRCA2 mutation in patients with ER-positive IDC.


Assuntos
Neoplasias da Mama/genética , Cromossomos Humanos Par 13 , Cromossomos Humanos Par 14 , Genes BRCA2 , Perda de Heterozigosidade , Neoplasias da Mama/patologia , Aberrações Cromossômicas , Feminino , Humanos , Pessoa de Meia-Idade , Mutação , Ploidias , Polimorfismo de Nucleotídeo Único
12.
Am J Hum Genet ; 92(6): 974-80, 2013 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-23684012

RESUMO

The genetic cause of some familial nonsyndromic renal cell carcinomas (RCC) defined by at least two affected first-degree relatives is unknown. By combining whole-exome sequencing and tumor profiling in a family prone to cases of RCC, we identified a germline BAP1 mutation c.277A>G (p.Thr93Ala) as the probable genetic basis of RCC predisposition. This mutation segregated with all four RCC-affected relatives. Furthermore, BAP1 was found to be inactivated in RCC-affected individuals from this family. No BAP1 mutations were identified in 32 familial cases presenting with only RCC. We then screened for germline BAP1 deleterious mutations in familial aggregations of cancers within the spectrum of the recently described BAP1-associated tumor predisposition syndrome, including uveal melanoma, malignant pleural mesothelioma, and cutaneous melanoma. Among the 11 families that included individuals identified as carrying germline deleterious BAP1 mutations, 6 families presented with 9 RCC-affected individuals, demonstrating a significantly increased risk for RCC. This strongly argues that RCC belongs to the BAP1 syndrome and that BAP1 is a RCC-predisposition gene.


Assuntos
Carcinoma de Células Renais/genética , Mutação em Linhagem Germinativa , Neoplasias Renais/genética , Mutação de Sentido Incorreto , Proteínas Supressoras de Tumor/genética , Ubiquitina Tiolesterase/genética , Adulto , Sequência de Bases , Carcinoma de Células Renais/enzimologia , Carcinoma de Células Renais/patologia , Exoma , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Humanos , Neoplasias Renais/enzimologia , Neoplasias Renais/patologia , Masculino , Pessoa de Meia-Idade , Linhagem , Polimorfismo de Nucleotídeo Único , Análise de Sequência de DNA
13.
Cancer Res ; 72(21): 5454-62, 2012 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-22933060

RESUMO

BRCA1 inactivation is a frequent event in basal-like breast carcinomas (BLC). However, BRCA1 can be inactivated by multiple mechanisms and determining its status is not a trivial issue. As an alternate approach, we profiled 65 BLC cases using single-nucleotide polymorphism arrays to define a signature of BRCA1-associated genomic instability. Large-scale state transitions (LST), defined as chromosomal break between adjacent regions of at least 10 Mb, were found to be a robust indicator of BRCA1 status in this setting. Two major ploidy-specific cutoffs in LST distributions were sufficient to distinguish highly rearranged BLCs with 85% of proven BRCA1-inactivated cases from less rearranged BLCs devoid of proven BRCA1-inactivated cases. The genomic signature we defined was validated in a second independent series of 55 primary BLC cases and 17 BLC-derived tumor cell lines. High numbers of LSTs resembling BRCA1-inactivated BLC were observed in 4 primary BLC cases and 2 BLC cell lines that harbored BRCA2 mutations. Overall, the genomic signature we defined predicted BRCA1/2 inactivation in BLCs with 100% sensitivity and 90% specificity (97% accuracy). This assay may ease the challenge of selecting patients for genetic testing or recruitment to clinical trials of novel emerging therapies that target DNA repair deficiencies in cancer.


Assuntos
Neoplasias da Mama/genética , Carcinoma Ductal de Mama/genética , Genes BRCA1 , Genes BRCA2 , Testes Genéticos/métodos , Instabilidade Genômica , Ploidias , Adenocarcinoma/genética , Adenocarcinoma/patologia , Neoplasias da Mama/patologia , Carcinoma Ductal de Mama/patologia , Feminino , Imunofluorescência , Humanos , Reação em Cadeia da Polimerase , Polimorfismo de Nucleotídeo Único , Sensibilidade e Especificidade
14.
Hum Mutat ; 33(8): 1228-38, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22505045

RESUMO

Assessing the impact of variants of unknown significance (VUS) on splicing is a key issue in molecular diagnosis. This impact can be predicted by in silico tools, but proper evaluation and user guidelines are lacking. To fill this gap, we embarked upon the largest BRCA1 and BRCA2 splice study to date by testing 272 VUSs (327 analyses) within the BRCA splice network of Unicancer. All these VUSs were analyzed by using six tools (splice site prediction by neural network, splice site finder (SSF), MaxEntScan (MES), ESE finder, relative enhancer and silencer classification by unanimous enrichment, and human splicing finder) and the predictions obtained were compared with transcript analysis results. Combining MES and SSF gave 96% sensitivity and 83% specificity for VUSs occurring in the vicinity of consensus splice sites, that is, the surrounding 11 and 14 bases for the 5' and 3' sites, respectively. This study was also an opportunity to define guidelines for transcript analysis along with a tentative classification of splice variants. The guidelines drawn from this large series should be useful for the whole community, particularly in the context of growing sequencing capacities that require robust pipelines for variant interpretation.


Assuntos
Proteína BRCA1/genética , Proteína BRCA2/genética , Patologia Molecular/métodos , Patologia Molecular/normas , Processamento de RNA/genética , Éxons/genética , Feminino , Humanos
15.
Hum Mutat ; 32(3): 325-34, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21120943

RESUMO

The detection of unknown mutations remains a serious challenge and, despite the expected benefits for the patient's health, a large number of genes are not screened on a routine basis. We present the diagnostic application of EMMA (Enhanced Mismatch Mutation Analysis(®) , Fluigent, Paris, France), a novel method based on heteroduplex analysis by capillary electrophoresis using innovative matrices. BRCA1 and BRCA2 were screened for point mutations and large rearrangements in 1,525 unrelated patients (372 for the validation step and 1,153 in routine diagnosis) using a single analytical condition. Seven working days were needed for complete BRCA1/2 screening in 30 patients by one technician (excluding DNA extraction and sequencing). A total of 137 mutations were found, including a BRCA2 duplication of exons 19 and 20, previously missed by Comprehensive BRACAnalysis(®) . The mutation detection rate was 11.9%, which is consistent with patient inclusions. This study therefore suggests that EMMA represents a valuable short-term and midterm option for many diagnostic laboratories looking for an easy, reliable, and affordable strategy, enabling fast and sensitive analysis for a large number of genes.


Assuntos
Proteína BRCA1/genética , Proteína BRCA2/genética , Análise Mutacional de DNA/métodos , Genes BRCA1 , Genes BRCA2 , Testes Genéticos/métodos , Mutação Puntual , Proteína BRCA1/análise , Proteína BRCA2/análise , Neoplasias da Mama/genética , Aberrações Cromossômicas , Análise Custo-Benefício , Análise Mutacional de DNA/economia , DNA Recombinante , Eletroforese Capilar , Feminino , Mutação da Fase de Leitura , Ensaios de Triagem em Larga Escala/métodos , Humanos , Mutação de Sentido Incorreto , Neoplasias Ovarianas/genética
16.
Eur J Hum Genet ; 17(11): 1471-80, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19471317

RESUMO

Nearly one-half of BRCA1 and BRCA2 sequence variations are variants of uncertain significance (VUSs) and are candidates for splice alterations for example, by disrupting/creating splice sites. As out-of-frame splicing defects lead to a marked reduction of the level of the mutant mRNA cleared through nonsense-mediated mRNA decay, a cDNA-based test was developed to show the resulting allelic imbalance (AI). Fifty-four VUSs identified in 53 hereditary breast/ovarian cancer (HBOC) patients without BRCA1/2 mutation were included in the study. Two frequent exonic single-nucleotide polymorphisms on both BRCA1 and BRCA2 were investigated by using a semiquantitative single-nucleotide primer extension approach and the cDNA allelic ratios obtained were corrected using genomic DNA ratios from the same sample. A total of five samples showed AI. Subsequent transcript analyses ruled out the implication of VUS on AI and identified a deletion encompassing BRCA2 exons 12 and 13 in one sample. No sequence abnormality was found in the remaining four samples, suggesting implication of cis- or trans-acting factors in allelic expression regulation that might be disease causative in these HBOC patients. Overall, this study showed that AI screening is a simple way to detect deleterious splicing defects and that a major role for VUSs and deep intronic mutations in splicing anomalies is unlikely in BRCA1/2 genes. Methods to analyze gene expression and identify regulatory elements in BRCA1/2 are now needed to complement standard approaches to mutational analysis.


Assuntos
Desequilíbrio Alélico , Neoplasias da Mama/genética , Genes BRCA1 , Genes BRCA2 , Neoplasias Ovarianas/genética , Processamento de RNA , Feminino , Humanos , Mutação , Elementos Reguladores de Transcrição
17.
Hum Mutat ; 29(7): 975-82, 2008 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-18449911

RESUMO

It appears that all types of genomic nucleotide variations can be deleterious by affecting normal pre-mRNA splicing via disruption/creation of splice site consensus sequences. As it is neither pertinent nor realistic to perform functional testing for all of these variants, it is important to identify those that could lead to a splice defect in order to restrict transcript analyses to the most appropriate cases. Web-based tools designed to provide such predictions are available. We evaluated the performance of six of these tools (Splice Site Prediction by Neural Network [NNSplice], Splice-Site Finder [SSF], MaxEntScan [MES], Automated Splice-Site Analyses [ASSA], Exonic Splicing Enhancer [ESE] Finder, and Relative Enhancer and Silencer Classification by Unanimous Enrichment [RESCUE]-ESE) using 39 unrelated retinoblastoma patients carrying different RB1 variants (31 intronic and eight exonic). These 39 patients were screened for abnormal splicing using puromycin-treated cell lines and the results were compared to the predictions. As expected, 17 variants impacting canonical AG/GT splice sites were correctly predicted as deleterious. A total of 22 variations occurring at loosely defined positions (+/-60 nucleotides from an AG/GT site) led to a splice defect in 19 cases and 16 of them were classified as deleterious by at least one tool (84% sensitivity). In other words, three variants escaped in silico detection and the remaining three were correctly predicted as neutral. Overall our results suggest that a combination of complementary in silico tools is necessary to guide molecular geneticists (balance between the time and cost required by RNA analysis and the risk of missing a deleterious mutation) because the weaknesses of one in silico tool may be overcome by the results of another tool.


Assuntos
Algoritmos , Diagnóstico por Computador , Técnicas de Diagnóstico Molecular , Sítios de Splice de RNA , Tomada de Decisões , Humanos , Proteína do Retinoblastoma/genética
18.
Eur J Hum Genet ; 15(4): 473-7, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17299438

RESUMO

Familial forms of retinoblastoma, an embryonic neoplasm of retinal origin, are caused by constitutional mutations of the RB1 gene. In this paper, we describe a family with retinoblastoma affecting two brothers with no previous family history of cancer. Complete RB1 mutational screening including point mutation and large rearrangement screening failed to demonstrate any mutation. The whole coding sequence was therefore investigated at the cDNA level, demonstrating a 103 bp intronic insertion between exons 23 and 24, leading to subsequent frameshift and premature termination of translation. This intronic exonisation was caused by a deep intronic mutation in intron 23 generating a cryptic 3' splice site. This is the first report of a deep intronic mutation in RB1 and is a proof of concept that some undetected RB1 mutations should be investigated at the cDNA level, particularly in hereditary forms of retinoblastoma.


Assuntos
Éxons , Genes do Retinoblastoma , Íntrons/genética , Mutagênese Insercional , Mutação/genética , Proteína do Retinoblastoma/genética , Retinoblastoma/genética , Sequência de Aminoácidos , Pré-Escolar , Análise Mutacional de DNA , DNA Complementar/genética , Humanos , Masculino , Dados de Sequência Molecular , Polimorfismo Genético , Sítios de Splice de RNA/genética , Processamento de RNA , Neoplasias da Retina/genética
19.
Anal Chem ; 76(16): 4839-48, 2004 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-15307796

RESUMO

We present here a new approach to electrophoretic heteroduplex analysis (EHDA) based on improved matrixes. EHDA is an appealing technique for the detection of unknown point mutations because of its simplicity and high throughput. We present here a new matrix for electrophoretic heteroduplex analysis much more sensitive for insertions, deletions, and substitutions than reported for previous EHDA separations and also superior to DHPLC. This separation matrix is based on a copolymer with a comb architecture, poly(acrylamide-g-polydimethylacrylamide), made of a high molecular weight polyacrylamide backbone grafted with poly(dimethylacrylamide) side chains. The effect of operational parameters on electrophoretic resolution and sensitivity to single-nucleotide mismatches was studied using a collection of samples from patients bearing mutations in the breast cancer predisposition genes BRCA1 and BRCA2. Seventeen fragments (10 mutations), implying mostly substitutions on fragments with sizes ranging from 200 to 600 bp, were analyzed using a single set of separation conditions. A success rate of 94% was achieved with a qualitative analysis in terms of number of peaks, and 100% identification of mutations was obtained with a more quantitative test using peak width analysis. This strong improvement of performance with regard to previous HDA methods is attributed to a composite mechanism of separation, combining steric and chromatographic effects. It opens the route to a significant reduction of development time and operation cost for diagnostic and genomic applications.


Assuntos
Genes BRCA1 , Genes BRCA2 , Ácidos Nucleicos Heteroduplexes/análise , Mutação Puntual , Sequência de Bases , DNA/sangue , DNA/genética , Primers do DNA , Eletroforese Capilar , Humanos , Polimorfismo Conformacional de Fita Simples , Deleção de Sequência
20.
Oncogene ; 23(4): 914-9, 2004 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-14647443

RESUMO

Germ-line mutations of the BRCA1 and BRCA2 genes, when they lead to a truncated protein, confer a high risk of breast and ovarian cancer. However, the role of BRCA1 missense mutations in cancer predisposition is unclear. Functional assays may be very helpful to more clearly define the biological effect of these mutations, and could therefore be useful in clinical practice. A recent study using a Host Cell End-Joining assay showed that a truncating mutation results in impaired fidelity of DSB repair by DNA end-joining. In the present study, we examined the fidelity of DSB repair in four lymphoblastoid cell lines with BRCA1 missense mutations. The fidelity of DNA end-joining was impaired in the four cell lines studied compared to the normal control cell line. The fidelity of end-joining was similar to that of a truncated mutation control cell line for one cell line and slightly higher for the other cell lines.


Assuntos
Dano ao DNA , Reparo do DNA , Genes BRCA1 , Heterozigoto , Mutação de Sentido Incorreto , Linhagem Celular , Humanos
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