RESUMEN

UNLABELLED: Essentials Variants at ABO, von Willebrand Factor (VWF) and 2q12 contribute to the variation in plasma in VWF. We performed a genome-wide association study of plasma VWF propeptide in 3,238 individuals. ABO, VWF and 2q12 loci had weak or no association or linkage with plasma VWFpp levels. VWF associated variants at ABO, VWF and 2q12 loci primarily affect VWF clearance rates. SUMMARY: Background Previous studies identified common variants at the ABO and VWF loci and unknown variants in a chromosome 2q12 linkage interval that contributed to the variation in plasma von Willebrand factor (VWF) levels. Whereas the association with ABO haplotypes can be explained by differential VWF clearance, little is known about the mechanisms underlying the association with VWF single-nucleotide polymorphisms (SNPs) or with variants in the chromosome 2 linkage interval. VWF propeptide (VWFpp) and mature VWF are encoded by the VWF gene and secreted at the same rate, but have different plasma half-lives. Therefore, comparison of VWFpp and VWF association signals can be used to assess whether the variants are primarily affecting synthesis/secretion or clearance. Methods We measured plasma VWFpp levels and performed genome-wide linkage and association studies in 3238 young and healthy individuals for whom VWF levels had been analyzed previously. Results and conclusions Common variants in an intergenic region on chromosome 7q11 were associated with VWFpp levels. We found that ABO serotype-specific SNPs were associated with VWFpp levels in the same direction as for VWF, but with a much lower effect size. Neither the association at VWF nor the linkage on chromosome 2 previously reported for VWF was observed for VWFpp. Taken together, these results suggest that the major genetic factors affecting plasma VWF levels, i.e. variants at ABO, VWF and a locus on chromosome 2, operate primarily through their effects on VWF clearance.

Asunto(s)

Precursores de Proteínas/sangre , Factor de von Willebrand/genética , Factor de von Willebrand/metabolismo , Sistema del Grupo Sanguíneo ABO , Adolescente , Adulto , Mapeo Cromosómico , Cromosomas Humanos Par 2/genética , Femenino , Ligamiento Genético , Variación Genética , Estudio de Asociación del Genoma Completo , Genotipo , Haplotipos , Humanos , Masculino , Fenotipo , Adulto Joven , Enfermedades de von Willebrand/sangre , Enfermedades de von Willebrand/genética

RESUMEN

OBJECTIVE: Women who have low cobalamin (vitamin B(12)) levels are at increased risk for having children with neural tube defects (NTDs). The transcobalamin II receptor (TCblR) mediates uptake of cobalamin into cells. Inherited variants in the TCblR gene as NTD risk factors were evaluated. METHODS: Case-control and family-based tests of association were used to screen common variation in TCblR as genetic risk factors for NTDs in a large Irish group. A confirmatory group of NTD triads was used to test positive findings. RESULTS: 2 tightly linked variants associated with NTDs in a recessive model were found: TCblR rs2336573 (G220R; p(corr)=0.0080, corrected for multiple hypothesis testing) and TCblR rs9426 (p(corr)=0.0279). These variants were also associated with NTDs in a family-based test before multiple test correction (log-linear analysis of a recessive model: rs2336573 (G220R; RR=6.59, p=0.0037) and rs9426 (RR=6.71, p=0.0035)). A copy number variant distal to TCblR and two previously unreported exonic insertion-deletion polymorphisms were described. CONCLUSIONS: TCblR rs2336573 (G220R) and TCblR rs9426 represent a significant risk factor in NTD cases in the Irish population. The homozygous risk genotype was not detected in nearly 1000 controls, indicating that this NTD risk factor may be of low frequency and high penetrance. 9 other variants are in perfect linkage disequilibrium with the associated single nucleotide polymorphisms. Additional work is required to identify the disease-causing variant. Our data suggest that variation in TCblR plays a role in NTD risk and that these variants may modulate cobalamin metabolism.

Asunto(s)

Predisposición Genética a la Enfermedad , Defectos del Tubo Neural/genética , Polimorfismo Genético , Receptores de Superficie Celular/genética , Alelos , Estudios de Casos y Controles , Estudios de Cohortes , Familia , Femenino , Frecuencia de los Genes , Genotipo , Humanos , Irlanda , Masculino , Receptores de Superficie Celular/metabolismo , Factores de Riesgo , Transcobalaminas/metabolismo

RESUMEN

BACKGROUND: Translational research is needed to explore how people will respond to personal genetic susceptibility information related to common health conditions. Maximizing the rigor of this research will require that genetic test results be returned to study participants. Currently, there is no established method that guides the selection of genetic variants to be used in research with these objectives. METHODS AND RESULTS: To address this question, we designed a process to identify gene variants and health conditions to be included in a prototype genetic test for use in a larger research effort, the Multiplex Initiative. The intention of this exploration was to facilitate research that generates individual genetic test results that are returned to study participants. Inclusion criteria were developed as part of a transdisciplinary and iterative process that considered the weight of evidential support for genetic association with common health conditions, the appropriateness of use in human subjects research, and the recommendations of expert peer reviewers. CONCLUSIONS: The selection process was designed to identify gene variants for the limited purpose of translational research and, therefore, should not be seen as producing a valid clinical test. However, this example of an applied selection process may provide guidance for researchers who are designing studies to evaluate the implications of genetic susceptibility testing through the return of personalized genetic information. As the rate of genomic discoveries increases, such research will be essential in steering the translation of this information towards the greatest public health benefit.

Asunto(s)

Pruebas Genéticas/métodos , Investigación Biomédica Traslacional/tendencias , Asesoramiento Genético , Enfermedades Genéticas Congénitas/diagnóstico , Enfermedades Genéticas Congénitas/genética , Predisposición Genética a la Enfermedad , Variación Genética , Genómica , Humanos , Selección de Paciente , Revisión por Pares , Proyectos de Investigación

RESUMEN

While sequence analysis is considered by many to be the most sensitive method of detecting unknown mutations in large genes such as BRCA1, most published estimates of the prevalence of mutations in this gene have been derived from studies that have used other methods of gene analysis. In order to determine the relative sensitivity of techniques that are widely used in research on BRCA1, a set of blinded samples containing 58 distinct mutations were analysed by four separate laboratories. Each used one of the following methods: single strand conformational polymorphism analysis (SSCP), conformation sensitive gel electrophoresis (CSGE), two dimensional gene scanning (TDGS), and denaturing high performance liquid chromatography (DHPLC). Only the laboratory using DHPLC correctly identified each of the mutations. The laboratory using TDGS correctly identified 91% of the mutations but produced three apparent false positive results. The laboratories using SSCP and CSGE detected abnormal migration for 72% and 76% of the mutations, respectively, but subsequently confirmed and reported only 65% and 60% of mutations, respectively. False negatives therefore resulted not only from failure of the techniques to distinguish wild type from mutant, but also from failure to confirm the mutation by sequence analysis as well as from human errors leading to misreporting of results. These findings characterise sources of error in commonly used methods of mutation detection that should be addressed by laboratories using these methods. Based upon sources of error identified in this comparison, it is likely that mutations in BRCA1 and BRCA2 are more prevalent than some studies have previously reported. The findings of this comparison provide a basis for interpreting studies of mutations in susceptibility genes across many inherited cancer syndromes.

Asunto(s)

Frecuencia de los Genes/genética , Genes BRCA1 , Pruebas Genéticas/métodos , Mutación/genética , Cromatografía Líquida de Alta Presión , Análisis Mutacional de ADN/economía , Análisis Mutacional de ADN/métodos , Exones/genética , Genes BRCA2 , Predisposición Genética a la Enfermedad/genética , Pruebas Genéticas/economía , Humanos , Desnaturalización de Ácido Nucleico , Polimorfismo Conformacional Retorcido-Simple , Reproducibilidad de los Resultados , Proyectos de Investigación , Sensibilidad y Especificidad , Método Simple Ciego , Temperatura

RESUMEN

Protein-protein interactions control numerous biological processes. In the case of a protein with no known function, identification of interacting proteins may lend insight into its cellular function. Protein-protein interactions are often detected by yeast two-hybrid screening which is based on a transcriptional read-out. One limitation of this technique is that transcription factors, when used as bait, frequently impair the effectiveness of this screen because they give rise to high levels of false positives. The carboxyl terminus of the breast cancer tumor suppressor gene, BRCA1, contains two BRCT motifs, a motif found in several DNA repair and cell cycle checkpoint proteins. This region of BRCA1 also exhibits an intrinsic transcriptional transactivation activity when bound to DNA as a fusion protein, thereby limiting its use in yeast two-hybrid screen. In order to isolate proteins that interact with this domain of BRCA1, we utilized a Far-Western screen, a method based on direct protein binding. We used recombinant histidine-tagged BRCT as the primary protein probe. We isolated eight cDNAs that bind to the BRCT domain of BRCA1. Further analysis demonstrated that two of the clones encode for proteins that interact directly with the BRCT domain of BRCA1.

Asunto(s)

Proteína BRCA1/metabolismo , Western Blotting/métodos , Pruebas Genéticas/métodos , Unión Proteica , Clonación Molecular , Biblioteca de Genes , Humanos , Fragmentos de Péptidos/genética , Placenta/metabolismo , Estructura Terciaria de Proteína/genética , ARN Mensajero/biosíntesis , Secuencias Repetitivas de Aminoácido/genética , Células Tumorales Cultivadas

RESUMEN

BACKGROUND: Detection of mutations by gel electrophoresis and allele-specific amplification by PCR (AS-PCR) is not easily scaled to accommodate a large number of samples. Alternative electrophoretic formats, such as capillary electrophoresis (CE) and microchip electrophoresis, may provide powerful platforms for simple, fast, automated, and high-throughput mutation detection after allele-specific amplification. METHODS: DNA samples heterozygous for four mutations (185delAG, 5382insC, 3867G-->T, and 6174delT) in BRCA1 and BRCA2, and homozygous for one mutation (5382insC) in BRCA1 and two mutations (16delAA and 822delG) in PTEN were chosen as the model system to evaluate the capillary and microchip electrophoresis methods. To detect each mutation, three primers, of which one was labeled with the fluorescent dye 6-carboxyfluorescein and one was the allele-specific primer (mutation-specific primer), were used to amplify the DNA fragments in the range of 130-320 bp. AS-PCR was combined with heteroduplex (HD) analysis, where the DNA fragments obtained by AS-PCR were analyzed with the conditions developed for CE-based HD analysis (using a fluorocarbon-coated capillary and hydroxyethylcellulose). The CE conditions were transferred into the microchip electrophoresis format. RESULTS: Three genotypes, homozygous wild type, homozygous mutant, and heterozygous mutant, could be identified by CE-based AS-PCR-HD analysis after 10-25 min of analysis time. Using the conditions optimized with CE, we translated the AS-PCR-HD analysis mutation detection method to the microchip electrophoresis format. The detection of three heterozygous mutations (insertion, deletion, and substitution) in BRCA1 could be accomplished in 180 s or less. CONCLUSIONS: It is possible to develop a CE-based method that exploits both AS-PCR and HD analysis for detecting specific mutations. Fast separation and the capacity for automated operation create the potential for developing a powerful electrophoresis-based mutation detection system. Fabrication of multichannel microchip platforms may enable mutation detection with high throughput.

Asunto(s)

Proteína BRCA1/genética , Proteínas de Neoplasias/genética , Factores de Transcripción/genética , Proteína BRCA2 , Electroforesis/métodos , Electroforesis Capilar , Humanos , Mutación , Reacción en Cadena de la Polimerasa/métodos , Células Tumorales Cultivadas

RESUMEN

Alterations in homocysteine, methionine, folate, and/or B12 homeostasis have been associated with neural tube defects, cardiovascular disease, and cancer. Methionine synthase, one of only two mammalian enzymes known to require vitamin B12 as a cofactor, lies at the intersection of these metabolic pathways. This enzyme catalyzes the transfer of a methyl group from 5-methyl-tetrahydrofolate to homocysteine, generating tetrahydrofolate and methionine. Human patients with methionine synthase deficiency exhibit homocysteinemia, homocysteinuria, and hypomethioninemia. They suffer from megaloblastic anemia with or without some degree of neural dysfunction and mental retardation. To better study the pathophysiology of methionine synthase deficiency, we utilized gene-targeting technology to inactivate the methionine synthase gene in mice. On average, heterozygous knockout mice from an outbred background have slightly elevated plasma homocysteine and methionine compared to wild-type mice but seem to be otherwise indistinguishable. Homozygous knockout embryos survive through implantation but die soon thereafter. Nutritional supplementation during pregnancy was unable to rescue embryos that were completely deficient in methionine synthase. Whether any human patients with methionine synthase deficiency have a complete absence of enzyme activity is unclear. These results demonstrate the importance of this enzyme for early development in mice and suggest either that methionine synthase-deficient patients have residual methionine synthase activity or that humans have a compensatory mechanism that is absent in mice.

Asunto(s)

5-Metiltetrahidrofolato-Homocisteína S-Metiltransferasa/deficiencia , 5-Metiltetrahidrofolato-Homocisteína S-Metiltransferasa/genética , 5-Metiltetrahidrofolato-Homocisteína S-Metiltransferasa/metabolismo , Animales , Secuencia de Bases , Enfermedades Cardiovasculares/enzimología , Enfermedades Cardiovasculares/genética , Cartilla de ADN/genética , Desarrollo Embrionario y Fetal/genética , Desarrollo Embrionario y Fetal/fisiología , Femenino , Ácido Fólico/administración & dosificación , Marcación de Gen , Heterocigoto , Homocisteína/sangre , Homocigoto , Humanos , Metionina/sangre , Ratones , Ratones Noqueados , Defectos del Tubo Neural/enzimología , Defectos del Tubo Neural/genética , Embarazo , Factores de Riesgo , Deficiencia de Vitamina B 12/enzimología , Deficiencia de Vitamina B 12/genética

RESUMEN

The efficacy of capillary electrophoresis for detecting DNA mutations via heteroduplex analysis (HDA) is dependent upon both the effective passivition of the capillary surface and the choice of the correct polymer network for sieving. Using HDA with laser-induced fluorescence detection of fluorescently labeled DNA fragments, an effective coating and optimal polymer matrix were sought. Optimized separation conditions were determined through the methodological evaluation of a number of different silanizing reagents, polymeric coatings, and polymer networks for resolving the PCR-amplified DNA fragments associated with five mutations (185delAG, 1294del40, 4446C > G, 5382insC, 5677insA) in the breast cancer susceptibility gene (BRCA1). For capillary coating, allyldimethylchlorosilane, 4-chlorobutyldimethylchlorosilane, (gamma-methacryloxypropyl)trimethoxysilane, chlorodimethyloctylsilane (OCT), and 7-octenyltrimethoxysilane were evaluated as silanizing reagents in combination with poly(vinylprrolidone) (PVP) and polyacrylamide (PA) as the polymeric coat. The HDA results were compared with those obtained using a commercial (FC) coated capillary. Of these, the OCT-PVP combination was found to be most effective. Using this modified capillary, HDA with polymer networks that included hydroxyethylcellulose (HEC), linear polyacrylamide, and PVP showed that a PVP-, PA-, or FC-coated capillary, in combination with HEC as the sieving polymer, could be used effectively to discriminate the mutations in less than 10 min. However, optimal performance was observed with the OCT-PVP-coated capillary and HEC as the polymer network.

Asunto(s)

ADN/química , Electroforesis Capilar/métodos , Análisis Heterodúplex/métodos , Colorantes Fluorescentes , Indicadores y Reactivos , Reacción en Cadena de la Polimerasa , Polímeros , Propiedades de Superficie

RESUMEN

In this report, we explore the potential of capillary and microchip electrophoresis for heteroduplex analysis- (HDA) based mutation detection. Fluorescent dye-labeled primers (6-FAM-tagged) were used to amplify the DNA fragments ranging from 130 to 400 bp. The effects of DNA fragment length, matrix additives, pH, and salt were evaluated for capillary electrophoresis- (CE) and/or microchip electrophoresis-based HDA, using six heterozygous mutations, 185delAG, E1250X (3867GT), R1443G (4446CG), 5382insC, 5677insA in BRCA1, and 6174delT in BRCA2. For this system, the effective fragment size for CE-based HDA was found in the range of 200-300 bp, however, the effective range was 150-260 bp for microchip-based HDA. Sensitivity studies show CE-based HDA could detect a mutated DNA present at only 1%-10% of the total DNA. Discrimination between wild-type and deletion or insertion mutations in BRCA1 and BRCA2 with CE-based HDA could be achieved in <8 min, while the substitution mutations required 14 min of analysis time. For each mutation region, 15 samples were run to confirm the accuracy and reproducibility of the method. Using the method described, two previously reported mutations, E1038G (3232AG, missense) and 4427 C/T (4427CT, polymorphism), were detected in the tested samples and confirmed by DNA sequencing. Translation of the CE-based methodology to the microchip format allowed the analysis time for each mutation to be decreased to 130 sec. Based on the results obtained with this model system, it is possible that CE-based HDA methodologies can be developed and used effectively in genetic testing. The fast separation time and automated operation afforded with CE instrumentation provide a powerful system for screening mutations that include small deletions, insertions, and point mutations. Translation to the microchip platform, especially to a multichannel microchip system, would allow for screening mutations with high throughput.

Asunto(s)

Mutagénesis Insercional/genética , Ácidos Nucleicos Heterodúplex/análisis , Ácidos Nucleicos Heterodúplex/genética , Mutación Puntual/genética , Eliminación de Secuencia/genética , Proteína BRCA2 , Biomarcadores de Tumor/análisis , Biomarcadores de Tumor/genética , Cartilla de ADN , Electroforesis Capilar/instrumentación , Electroforesis Capilar/métodos , Electroforesis Capilar/estadística & datos numéricos , Femenino , Colorantes Fluorescentes , Genes BRCA1 , Marcadores Genéticos/genética , Homocigoto , Humanos , Proteínas de Neoplasias/análisis , Proteínas de Neoplasias/genética , Reacción en Cadena de la Polimerasa , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Factores de Transcripción/análisis , Factores de Transcripción/genética

RESUMEN

The Breast Cancer Information Core (BIC) is an open access, on-line mutation database for breast cancer susceptibility genes. In addition to creating a catalogue of all mutations and polymorphisms in breast cancer susceptibility genes, a principle aim of the BIC is to facilitate the detection and characterization of these genes by providing technical support in the form of mutation detection protocols, primer sequences, and reagent access. Additional information at the site includes a literature review compiled from published studies, links to other internet-based, breast cancer information and research resources, and an interactive discussion forum which enables investigators to post or respond to questions and/or comments on a bulletin board. Hum Mutat 16:123-131, 2000. Published 2000 Wiley-Liss, Inc.

Asunto(s)

Neoplasias de la Mama/genética , Redes de Comunicación de Computadores , Bases de Datos Factuales , Algoritmos , Proteína BRCA1/clasificación , Proteína BRCA1/genética , Proteína BRCA2 , Neoplasias de la Mama/clasificación , Sistemas de Administración de Bases de Datos , Bases de Datos Factuales/estadística & datos numéricos , Bases de Datos Factuales/tendencias , Femenino , Haplotipos , Humanos , Masculino , Mutación/genética , Proteínas de Neoplasias/clasificación , Proteínas de Neoplasias/genética , Neoplasias Ováricas/clasificación , Neoplasias Ováricas/genética , Programas Informáticos , Terminología como Asunto , Factores de Transcripción/clasificación , Factores de Transcripción/genética

RESUMEN

The insulin-like growth factor I receptor (IGF-I-R) has an important role in breast cancer etiology. The receptor is overexpressed by most breast cancers, where it functions as a potent antiapoptotic agent. BRCA1 is a tumor suppressor gene that is mutated in a large fraction of familial breast and ovarian cancers. Cotransfection of Saos-2, MCF7, and CHO cells with IGF-I-R promoter constructs driving luciferase reporter genes, and with a BRCA1 expression vector, suppressed promoter activity in a dose-dependent manner. Functional interactions between BRCA1 and Sp1 in the regulation of the IGF-I-R gene were studied in Schneider cells, a Drosophila cell line which lacks endogenous Sp1. In these cells BRCA1 suppressed 45% of the Sp1-induced trans-activation of the IGF-I-R promoter. These results suggest that BRCA1 is capable of suppressing the IGF-I-R promoter in a number of cell lines, thus resulting in low levels of receptor mRNA and protein. Mutant versions of BRCA1 lacking trans-activational activity can potentially derepress the IGF-I-R promoter. Activation of the overexpressed receptor by locally produced or circulating IGFs may be a crucial step in breast and ovarian cancer progression.

Asunto(s)

Proteína BRCA1/metabolismo , Regiones Promotoras Genéticas , Receptor IGF Tipo 1/metabolismo , Factor de Transcripción Sp1/metabolismo , Animales , Células CHO , Línea Celular , Cricetinae , Drosophila/citología , Regulación de la Expresión Génica , Humanos , Ratones , Unión Proteica , Transfección

RESUMEN

As a result of intensive studies on hereditary breast and ovarian cancers, two breast cancer susceptibility genes, BRCA1 and BRCA2, have been identified. In each gene, a small number of specific mutations have been found at relatively high frequency in certain ethnic populations. The mutations, 185delAG and 5382insC in BRCA1 and 6174delT in BRCA2, have been identified as common mutations in the Ashkenazi Jewish population, with a combined frequency of 2.0 to 2.5%. Women who have one of the above three common mutations are at a high risk of developing breast or ovarian cancer. Consequently, accurate and cost-effective detection of these three mutations may have important implications for risk assessment in susceptible women and men. In this report, we describe a fast and simple capillary electrophoresis (CE)-based method using a polymer network for screening the three common mutations in BRCA1 and BRCA2. Fluorescent dye-labeled primers (6-FAM-tagged) were used to amplify three DNA fragments of 258, 296, and 201 bp for detection of the 185delAG, 5382insC, and 6174delT mutations, respectively. After the PCR products were denatured, a single-strand conformation polymorphism (SSCP) profile could be obtained for each mutation in less than 10 min by CE in a polymer network. We demonstrate the potential provided by translating this assay to the microchip format where the SSCP analysis is complete in 120 s, representing only a fraction of the reduction in analysis time that can be achieved with microchip technology. The speed and simplicity of the SSCP methodology for detection of these mutations make it attractive for use in the clinical diagnostic laboratory.

Asunto(s)

Proteína BRCA1/genética , Marcadores Genéticos/genética , Proteínas de Neoplasias/genética , Factores de Transcripción/genética , Proteína BRCA1/sangre , Proteína BRCA2 , Análisis Mutacional de ADN/métodos , Electroforesis Capilar/métodos , Humanos , Proteínas de Neoplasias/sangre , Análisis de Secuencia por Matrices de Oligonucleótidos/métodos , Reacción en Cadena de la Polimerasa , Polimorfismo Conformacional Retorcido-Simple , Factores de Transcripción/sangre

RESUMEN

The breast cancer predisposing gene, BRCA1, was analyzed for germline mutations in 45 African American families at high-risk for hereditary breast cancer. Patients were considered high-risk if they had a family history of the disease, early onset breast cancer, bilateral breast cancer, or breast and ovarian cancer. The entire BRCA1 coding and flanking intron regions have been examined by single stranded conformation polymorphism analysis followed by sequencing of variant bands. Eleven different BRCA1 germline mutations/variations were identified in 7 patients from the 45 high-risk families. Two pathogenic, protein-truncating mutations were detected in exon 11. A ten base pair tandem duplication, 943ins10, was present in a woman with breast and ovarian cancer whose first-degree relatives had prostate cancer. A four base pair deletion, 3450del4, was detected in a breast cancer patient with five cases of breast cancer in the family; two of the proband's sisters with breast cancer also carried the same mutation. Four amino acid substitutions (Lys1183Arg, Leu1564Pro, Gln1785His, and Glu1794Asp) and four nucleotide substitutions in intron 22 (IVS22+78 C/A, IVS22+67 T/C, IVS22+8 T/A and IVS22+7 T/C) were observed in patients and not in control subjects. One early onset breast cancer patient carried five distinct BRCA1 variations, two amino acid substitutions and three substitutions in intron 22. An amino acid substitution in exon 11, Ser1140Gly, was identified in 3 different unrelated patients and in 6 of 92 control samples. The latter probably represents a benign polymorphism.

Asunto(s)

Población Negra/genética , Neoplasias de la Mama/genética , Genes BRCA1/genética , Mutación , Adulto , Edad de Inicio , Anciano , Anciano de 80 o más Años , Neoplasias de la Mama Masculina/genética , Análisis Mutacional de ADN , Femenino , Humanos , Intrones , Masculino , Persona de Mediana Edad , Neoplasias Ováricas/genética , Linaje , Polimorfismo Genético , Polimorfismo Conformacional Retorcido-Simple , Neoplasias de la Próstata/genética , Factores de Riesgo , Estados Unidos

RESUMEN

Periconceptual folate supplementation has been found to prevent the occurrence of many neural tube defects (NTDs). Consequently, genetic variation in folate metabolism genes is expected to contribute to the risk for neural tube defects. Methionine synthase catalyzes the vitamin B(12)-dependent conversion of homocysteine and 5-methyltetrahydrofolate to methionine and tetrahydrofolate. The observation that homocysteine and vitamin B(12) levels are independent predictors of NTD risk suggested that methionine synthase could be a candidate gene for NTDs. To assess the role of the MS gene in NTDs, we performed high-resolution physical mapping of the MS locus, isolated highly polymorphic markers linked to the MS gene, and tested for an association between specific MS alleles and NTDs. We mapped the MS gene to a position between 909 and 913 cR(10000) on chromosome 1 by radiation hybrid mapping. Polymorphic markers D1S1567 and D1S1568 map to locations no more than 900 and 194 kb from the MS gene, respectively. The segregation of these polymorphic markers was measured in 85 Irish NTD families. No allele of either marker showed a significant association with NTDs using the transmission disequilibrium test. A lack of association was also observed for the D1919G missense mutation within the gene. Our results suggest that inherited variation in the MS gene does not contribute to NTD risk in this population.

Asunto(s)

5-Metiltetrahidrofolato-Homocisteína S-Metiltransferasa/genética , Adulto , Alelos , Niño , Preescolar , Mapeo Cromosómico , Cromosomas Humanos Par 1/genética , Mapeo Contig , ADN/genética , Salud de la Familia , Femenino , Genes/genética , Biblioteca Genómica , Genotipo , Humanos , Células Híbridas , Desequilibrio de Ligamiento , Escala de Lod , Masculino , Repeticiones de Microsatélite , Defectos del Tubo Neural/genética , Lugares Marcados de Secuencia

RESUMEN

Here we report the application of high-density oligonucleotide array (DNA chip)-based analysis to determine the distant history of single nucleotide polymorphisms (SNPs) in current human populations. We analysed orthologues for 397 human SNP sites (identified in CEPH pedigrees from Amish, Venezuelan and Utah populations) from 23 common chimpanzee, 19 pygmy chimpanzee and 11 gorilla genomic DNA samples. From this data we determined 214 proposed ancestral alleles (the sequence found in the last common ancestor of humans and chimpanzees). In a diverse human population set, we found that SNP alleles with higher frequencies were more likely to be ancestral than less frequently occurring alleles. There were, however, exceptions. We also found three shared human/pygmy chimpanzee polymorphisms, all involving CpG dinucleotides, and two shared human/gorilla polymorphisms, one involving a CpG dinucleotide. We demonstrate that microarray-based assays allow rapid comparative sequence analysis of intra- and interspecies genetic variation.

Asunto(s)

Hominidae/genética , Polimorfismo Genético , Alelos , Animales , Fosfatos de Dinucleósidos/química , Fosfatos de Dinucleósidos/genética , Genotipo , Gorilla gorilla/genética , Humanos , Modelos Genéticos , Pan troglodytes/genética , Linaje

RESUMEN

Methionine synthase is one of two key enzymes involved in the removal of the metabolite, homocysteine. Elevated homocysteine levels constitute a risk factor for cardiovascular diseases and for neural tube defects. In cell culture, the activity of methionine synthase is enhanced several-fold by supplementation with its cofactor, B12. The mechanism of this regulation is unknown, although it has been ascribed to a shift from apoenzyme to holoenzyme. Using sensitive assay techniques as well as a combination of Northern and Western analyses, we demonstrate that the effect of B12 on induction of methionine synthase activity is paralleled by an increase in the level of the enzyme. These studies exclude conversion of apoenzyme to holoenzyme as a basis for activation that had been described previously. Since the mRNA levels do not change during the same period that the methionine synthase levels increase, regulation of this protein by its cofactor must be exerted posttranscriptionally.

Asunto(s)

5-Metiltetrahidrofolato-Homocisteína S-Metiltransferasa/metabolismo , Procesamiento Proteico-Postraduccional/efectos de los fármacos , Vitamina B 12/farmacología , Animales , Apoenzimas/metabolismo , Sitios de Unión/genética , Línea Celular , Clonación Molecular , Activación Enzimática/efectos de los fármacos , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Holoenzimas/metabolismo , Homocisteína/metabolismo , Humanos , Cinética , ARN Mensajero/metabolismo

RESUMEN

Germ-line mutations in the BRCA1 tumor-suppressor gene are associated with an increased susceptibility to breast and ovarian cancer. BRCA1 contains a carboxyl-terminal domain (BRCT) that is shared with several other proteins involved in maintaining genome integrity. In an effort to understand the function of BRCA1, we sought to isolate proteins that interact with the BRCT domain. Purified BRCT polypeptide was used as a probe to screen a human placenta cDNA expression library by Far Western analysis. Here we report that BRCA1 interacts in vivo and in vitro with the Rb-binding proteins, RbAp46 and RbAp48, as well as with Rb. Moreover, the BRCT domain associates with the histone deacetylases HDAC1 and HDAC2. These results demonstrate that BRCA1 interacts with components of the histone deacetylase complex, and therefore may explain the involvement of BRCA1 in multiple processes such as transcription, DNA repair, and recombination.

Asunto(s)

Proteína BRCA1/genética , Proteínas Portadoras/genética , Histona Desacetilasas/genética , Proteínas Nucleares/genética , Proteína BRCA1/metabolismo , Proteínas Portadoras/metabolismo , Femenino , Células HeLa , Histona Desacetilasas/metabolismo , Humanos , Proteínas Nucleares/metabolismo , Embarazo , Unión Proteica/genética , Proteína 4 de Unión a Retinoblastoma , Proteína 7 de Unión a Retinoblastoma , Activación Transcripcional

RESUMEN

Three founder mutations in the cancer-associated genes BRCA1 and BRCA2 occur frequently enough among Ashkenazi Jews to warrant consideration of genetic testing outside the setting of high-risk families with multiple cases of breast or ovarian cancer. We estimated the prevalence of these founder mutations in BRCA1 and BRCA2 in the general population of Ashkenazi Jews according to age at testing, personal cancer history, and family cancer history. We compared the results of anonymous genetic testing of blood samples obtained in a survey of >5,000 Jewish participants from the Washington, DC, area with personal and family cancer histories obtained from questionnaires completed by the participants. In all subgroups defined by age and cancer history, fewer mutations were found in this community sample than in clinical series studied to date. For example, 11 (10%) of 109 Jewish women who had been given a diagnosis of breast cancer in their forties carried one of the mutations. The most important predictor of mutation status was a previous diagnosis of breast or ovarian cancer. In men and in women never given a diagnosis of cancer, family history of breast cancer before age 50 years was the strongest predictor. As interest in genetic testing for BRCA1 and BRCA2 in the Jewish community broadens, community-based estimates such as these help guide those seeking and those offering such testing. Even with accurate estimates of the likelihood of carrying a mutation and the likelihood of developing cancer if a mutation is detected, the most vexing clinical problems remain.

Asunto(s)

Genes BRCA1/genética , Predisposición Genética a la Enfermedad/genética , Pruebas Genéticas , Judíos/genética , Mutación/genética , Proteínas de Neoplasias/genética , Factores de Transcripción/genética , Adulto , Factores de Edad , Proteína BRCA2 , Neoplasias de la Mama/diagnóstico , Neoplasias de la Mama/epidemiología , Neoplasias de la Mama/genética , Recolección de Datos , District of Columbia/epidemiología , Salud de la Familia , Femenino , Efecto Fundador , Frecuencia de los Genes/genética , Heterocigoto , Humanos , Masculino , Persona de Mediana Edad , Neoplasias Ováricas/diagnóstico , Neoplasias Ováricas/epidemiología , Neoplasias Ováricas/genética , Prevalencia , Neoplasias de la Próstata/diagnóstico , Neoplasias de la Próstata/epidemiología , Neoplasias de la Próstata/genética , Encuestas y Cuestionarios

RESUMEN

BACKGROUND: Studies of survival following breast and ovarian cancers in BRCA1 and/or BRCA2 mutation carriers have yielded conflicting results. We undertook an analysis of a community-based study of Ashkenazi Jews to investigate the effect of three founder mutations in BRCA1 and BRCA2 on survival among patients with breast or ovarian cancer. METHODS: We collected blood samples and questionnaire data from 5318 Ashkenazi Jewish volunteers. The blood samples were tested for 185delAG (two nucleotide deletion) and 5382insC (single nucleotide insertion) mutations in BRCA1 and the 6174delT (single nucleotide deletion) mutation in BRCA2. To estimate survival differences in the affected relatives according to their BRCA1 and/or BRCA2 mutation carrier status, we devised and applied a novel extension of the kin-cohort method. RESULTS: Fifty mutation carriers reported that 58 of their first-degree relatives had been diagnosed with breast cancer and 10 with ovarian cancer; 907 noncarriers reported 979 first-degree relatives with breast cancer and 116 with ovarian cancer. Kaplan-Meier estimates of median survival after breast cancer were 16 years (95% confidence interval [CI] = 11-40) in the relatives of carriers and 18 years (95% CI = 15-22) in the relatives of noncarriers, a difference that was not statistically significant (two-sided P = .87). There was also no difference in survival times among the 126 first-degree relatives with ovarian cancer. We found no survival difference between patients with breast or ovarian cancer who were inferred carriers of BRCA1 and/or BRCA2 mutations and noncarriers. CONCLUSIONS: Carriers of BRCA1 and BRCA2 mutations appeared to have neither better nor worse survival prognosis.

Asunto(s)

Neoplasias de la Mama/etnología , Neoplasias de la Mama/genética , Neoplasias de la Mama/mortalidad , Genes Supresores de Tumor/genética , Judíos/estadística & datos numéricos , Mutación , Adulto , District of Columbia/epidemiología , Femenino , Genes BRCA1/genética , Humanos , Modelos Lineales , Persona de Mediana Edad , Neoplasias Ováricas/etnología , Neoplasias Ováricas/genética , Neoplasias Ováricas/mortalidad , Análisis de Supervivencia , Tasa de Supervivencia

RESUMEN

A major frontier in medical genetics is the definition of the molecular basis of multifactorial diseases. This is especially relevant in the field of clinical psychiatry where the majority of common disorders display complex inheritance patterns, and are further influenced by environmental interactions. New technologies are needed to help address the pressing needs for discovering and deciphering the nature of such disease-associated genes. One such technology which has emerged within the past 3 years involves hybridization-based nucleic acid array (DNA chip) analysis. This technology has the potential to have a lasting impact on diverse genomic-based applications such as large-scale gene mapping studies, mutational analysis, and global expression level monitoring of all human genes. In this review we will describe the fundamental principles behind nucleic acid array-based assays, while focusing on their applications towards genome-wide DNA and RNA analysis. The current capabilities and limitations of these technologies will be discussed, with a focus on areas where future development will be needed for DNA chip-based assays to achieve their full potential.

Asunto(s)

Enfermedades Genéticas Congénitas/genética , Predisposición Genética a la Enfermedad , Análisis de Secuencia por Matrices de Oligonucleótidos/métodos , Mapeo Cromosómico , Humanos