RESUMO
The identification of mutations in the BRCA1 gene poses difficulties in achieving a screening outcome that satisfies the twin needs of speed and accuracy. These needs must also take into account the patient's family history and the statistical evaluation of the probability of detecting a mutation. Given the above, we present here a hierarchical mutation screening strategy that comprises two tiers: first, multiplex heteroduplex and exon 13 duplication analysis; second, exon amplification and direct sequencing using a 96-well tray format. The advantages of this strategy are two-fold: first, the division of analytical tools in order to achieve low and high-resolution mutation screening, respectively; second, a streamlined sequencing approach that leads to a sensitive and rapid assay that reduces labor costs and handling errors. The success of this approach is shown by the identification of a novel deletion mutation in exon 14 of the BRCA1 gene, which was not detected by the more conventional protein truncation assay due to the small size of the predicted truncated protein.
Assuntos
Genes BRCA1/genética , Testes Genéticos/métodos , Adulto , Neoplasias da Mama/diagnóstico , Neoplasias da Mama/genética , Neoplasias da Mama Masculina/diagnóstico , Neoplasias da Mama Masculina/genética , Análise Mutacional de DNA/métodos , Análise Mutacional de DNA/estatística & dados numéricos , DNA de Neoplasias/genética , Feminino , Análise Heteroduplex , Humanos , Masculino , Pessoa de Meia-Idade , Ácidos Nucleicos Heteroduplexes/genética , Neoplasias Ovarianas/diagnóstico , Neoplasias Ovarianas/genética , Reação em Cadeia da Polimerase , Probabilidade , Medição de RiscoRESUMO
Individuals affected with Fragile X syndrome are usually characterized at the DNA level by the presence of at least 200 CGG repeats in the 5' untranslated region of the FMR1 gene; this number of repeats is defined as a full mutation. Repeats that number 50-200 usually define those with premutations and are termed unaffected carriers. We report here a compound heterozygous female who carried CGG repeats in the FMR1 gene that fall within the premutation and full mutation ranges. The former appears to have been inherited from the father, whereas the latter is an expansion of the premutation carried by the proband's mother. Therefore, the offspring of the proband will carry a significant risk of being affected with Fragile X syndrome, and the paternal uncle and any cousins should be counselled for being at risk for this syndrome.
Assuntos
Síndrome do Cromossomo X Frágil/genética , Proteínas do Tecido Nervoso/genética , Proteínas de Ligação a RNA , Cromossomo X/genética , Análise Mutacional de DNA , Feminino , Proteína do X Frágil da Deficiência Intelectual , Aconselhamento Genético , Predisposição Genética para Doença , Heterozigoto , Humanos , Recém-Nascido , Masculino , Linhagem , Penetrância , Reação em Cadeia da Polimerase , Repetições de TrinucleotídeosRESUMO
We have evaluated the usefulness of denaturing high performance liquid chromatography (dHPLC) for scanning the adenomatous polyposis coli (APC) gene for point mutations, small deletions, and insertions. Our assay consists of 28 sets of primers to amplify the 15 exons of the APC gene. All PCR reactions were amplified simultaneously using the same reaction conditions in a 96-well format and then analyzed by dHPLC, using empirically determined optimum temperatures for partial fragment denaturation. Previously studied DNA specimens from 47 familial adenomatous polyposis (FAP) patients were analyzed by dHPLC and all mutations were correctly identified and confirmed by sequence analysis. This approach identified a single-base substitution in exon 6 and a 2-bp insertion in exon 15 that initially had not been detected by single-strand conformational polymorphism (SSCP) analysis. A novel mutation in exon 15 of the APC gene, 2065delG (codon 689) that had previously been undetected by the protein truncation test (PTT) was also identified by dHPLC. We present our validation studies of dHPLC technology for APC gene analysis in terms of sensitivity and specificity and compare it to current standard scanning technologies including PTT, SSCP, and conformational sensitive gel electrophoresis (CSGE).
Assuntos
Proteína da Polipose Adenomatosa do Colo/genética , Polipose Adenomatosa do Colo/genética , Cromatografia Líquida de Alta Pressão , Éxons/genética , Variação Genética , Humanos , MutaçãoAssuntos
Deleção de Genes , Proteínas do Tecido Nervoso/genética , Proteínas de Ligação a RNA , Deleção de Sequência/genética , Alelos , Sequência de Bases , Western Blotting , Pré-Escolar , Análise Mutacional de DNA , Feminino , Proteína do X Frágil da Deficiência Intelectual , Síndrome do Cromossomo X Frágil/genética , Testes Genéticos , Humanos , Lactente , Recém-Nascido , Masculino , Proteínas do Tecido Nervoso/análise , Proteínas Nucleares/genética , Linhagem , Reação em Cadeia da Polimerase , Transativadores/genética , Repetições de Trinucleotídeos/genéticaRESUMO
Post-mortem investigation of sudden death in young people frequently reveals no overt cause for the death. Full investigation is hampered if tissue or blood is not retained for DNA analysis. We report a post mortem molecular diagnosis of long QT syndrome in a 12-year-old boy diagnosed with epilepsy who died suddenly playing sport. The DNA was extracted from an archived blood spot on his newborn screening ('Guthrie') card, which had been taken from him at 6 days of age. A missense mutation was detected in exon 5 of the KCNQ1 gene; R243C (835C > T), associated with long QT type 1. The same mutation was found in the mother (who now takes effective preventative therapy), but not in the sib who has now been reassured that she is not at risk of sudden death.