RESUMO
For most cases of colorectal cancer that arise without a family history of the disease, it is proposed that an appreciable heritable component of predisposition is the result of contributions from many loci. Although progress has been made in identifying single nucleotide variants associated with colorectal cancer risk, the involvement of low-penetrance copy number variants is relatively unexplored. We have used multiplex amplifiable probe hybridization (MAPH) in a fourfold multiplex (QuadMAPH), positioned at an average resolution of one probe per 2 kb, to screen a total of 1.56 Mb of genomic DNA for copy number variants around the genes APC, AXIN1, BRCA1, BRCA2, CTNNB1, HRAS, MLH1, MSH2, and TP53. Two deletion events were detected, one upstream of MLH1 in a control individual and the other in APC in a colorectal cancer patient, but these do not seem to correspond to copy number polymorphisms with measurably high population frequencies. In summary, by means of our QuadMAPH assay, copy number measurement data were of sufficient resolution and accuracy to detect any copy number variants with high probability. However, this study has demonstrated a very low incidence of deletion and duplication variants within intronic and flanking regions of these nine genes, in both control individuals and colorectal cancer patients.
Assuntos
Neoplasias Colorretais/genética , Dosagem de Genes , Genes Neoplásicos , Variação Genética , Deleção Cromossômica , Cromossomos Humanos Par 3 , DNA/metabolismo , Deleção de Genes , Humanos , Íntrons , Modelos Genéticos , Hibridização de Ácido Nucleico , Reação em Cadeia da Polimerase , Reprodutibilidade dos Testes , RiscoRESUMO
BACKGROUND: Copy number variation (CNV) in the human genome is recognised as a widespread and important source of human genetic variation. Now the challenge is to screen for these CNVs at high resolution in a reliable, accurate and cost-effective way. RESULTS: Multiplex Amplifiable Probe Hybridisation (MAPH) is a sensitive, high-resolution technology appropriate for screening for CNVs in a defined region, for a targeted population. We have developed MAPH to a highly multiplexed format ("QuadMAPH") that allows the user a four-fold increase in the number of loci tested simultaneously. We have used this method to analyse a genomic region of 210 kb, including the MSH2 gene and 120 kb of flanking DNA. We show that the QuadMAPH probes report copy number with equivalent accuracy to simplex MAPH, reliably demonstrating diploid copy number in control samples and accurately detecting deletions in Hereditary Non-Polyposis Colorectal Cancer (HNPCC) samples. CONCLUSION: QuadMAPH is an accurate, high-resolution method that allows targeted screening of large numbers of subjects without the expense of genome-wide approaches. Whilst we have applied this technique to a region of the human genome, it is equally applicable to the genomes of other organisms.
Assuntos
Dosagem de Genes , Genoma Humano , Hibridização de Ácido Nucleico/métodos , Cromossomos Artificiais Bacterianos , Neoplasias Colorretais Hereditárias sem Polipose/genética , Sondas de DNA , Biblioteca Gênica , Humanos , Proteína 2 Homóloga a MutS/genética , Análise de Sequência de DNARESUMO
Mohr-Tranebjaerg syndrome (MTS) is an X-linked disorder characterized by childhood-onset progressive deafness, dystonia, spasticity, mental deterioration, and blindness. It is due to mutations in the deafness/dystonia peptide (DDP1) gene. We describe a sporadic 42-year-old man with MTS presenting with postlingual deafness, adult-onset progressive dystonia with marked arm tremor, mild spasticity of the legs, and visual disturbance due to a novel mutation (g to a transition at the invariant gt of the 5' splice donor site of exon 1) in the DDP1 gene. This case, and a review of previously reported cases, highlights a variety of potential diagnostic pitfalls in this condition.
Assuntos
Blefarospasmo/genética , Distonia/genética , Proteínas de Membrana Transportadoras/genética , Mutação/genética , Síndromes Orofaciodigitais/genética , Sítios de Splice de RNA/genética , Adulto , Blefarospasmo/etiologia , Análise Mutacional de DNA/métodos , Distonia/etiologia , Humanos , Masculino , Proteínas do Complexo de Importação de Proteína Precursora Mitocondrial , Síndromes Orofaciodigitais/complicaçõesRESUMO
OBJECTIVE: A long-surviving thanatophoric dysplasia type I patient to age of 6 years is presented. RESULTS AND CONCLUSIONS: Molecular studies revealed a heterozygous point mutation, S249C in the fibroblast growth factor receptor 3 gene. Most of the clinical course was similar to previous reports, including hearing loss and acanthosis nigricans. Abnormal urinary excretion of dicarboxylic acids and 3-hydroxydicarboxylic acids was observed. We hypothesize that this was a consequence of the FGFR3 mutation.