Familial adenomatous polyposis (FAP) is an autosomal dominant syndrome with almost 100 % risk of colorectal cancer. The typical FAP is characterized by hundreds to thousands of colorectal adenomatous polyps and by extracolonic manifestations, later onset and lower number of polyps in colon is characteristic of an attenuated form (AFAP). We analyzed the APC gene for germline mutations in 90 FAP/AFAP patients. Mutation screening was performed using Denaturing Gradient Gel Electrophoresis. DNA fragments showing an aberrant electrophoretic banding pattern were sequenced. APC-mutation-negative probands were screened for large deletions of the APC gene using multiplex ligation dependent probe amplification. Analysis of mRNA variants followed in probands with possible splicing mutation by PCR amplification of target site flanking exons and sequencing the normal and aberrant products. We identified 30 germline variants among 36 unrelated probands including large deletions. Eleven APC variants detected last two years have not been reported yet. At all, fifteen of them are expected to cause errors in mRNA splicing. Analysis of mRNA in ten of these patients revealed exon skipping in seven cases, exonisation of intron in one of these as well, change of the amount of alternatively spliced product in one case, and no effect was found in three cases. In two of the patients, the biopsy of colon mucosa and polyp enabled us to examine the effect of the mutation on splicing pattern in colon cells directly. The comparison of alternative and standard transcript amount showed similar transcription pattern of exon 14 in control colon mucosa tissue (9 samples) as in 51 blood control samples.

• MeSH
• alternativní sestřih * MeSH
• familiární adenomatózní polypóza genetika   MeSH
• genetická predispozice k nemoci MeSH
• geny APC * MeSH
• kolorektální nádory genetika   MeSH
• lidé MeSH
• mutace MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Česká republika MeSH

BACKGROUND: Germline mutations in the adenomatous polyposis gene (APC) result in familial adenomatous polyposis (FAP). FAP is an autosomal dominantly inherited disorder predisposing to colorectal cancer. Typical FAP is characterized by hundreds to thousands of colorectal adenomatous polyps and by several extracolonic manifestations. An attenuated form of polyposis (AFAP) is characterized by less than 100 adenomas and later onset of the disease. METHODS: Here, we analyzed the APC gene for germline mutations in 59 Czech and 15 Slovak FAP patients. In addition, 50 apparently APC mutation negative Czech probands and 3 probands of Slovak origin were screened for large deletions encompassing the APC gene. Mutation screening was performed using denaturing gradient gel electrophoresis and/or protein truncation test. DNA fragments showing an aberrant electrophoretic banding pattern were sequenced. Screening for large deletions was performed by multiplex ligation dependent probe amplification. The extent of deletions was analyzed using following microsatellite markers: D5S299, D5S82, D5S134 and D5S346. RESULTS: In the set of Czech and Slovak patients, we identified 46 germline mutations among 74 unrelated probands. Total mutation capture is 62,2% including large deletions. Thirty seven mutations were detected in 49 patients presenting a classical FAP phenotype (75,5%) and 9 mutations in 25 patients with attenuated FAP (36%). We report 20 novel germline APC mutations and 3 large deletions (6%) encompassing the whole-gene deletions and/or exon 14 deletion. In the patients with novel mutations, correlations of the mutation localization are discussed in context of the classical and/or attenuated phenotype of the disease. CONCLUSION: The results of the molecular genetic testing are used both in the establishment of the predictive diagnosis and in the clinical management of patients. In some cases this study has also shown the difficulty to classify clinically between the classical and the attenuated form of FAP according to the established criteria. Interfamilial and/or intrafamilial phenotype variability was also confirmed in some cases which did not fit well with predicted genotype-phenotype correlation. All these findings have to be taken into consideration both in the genetic counselling and in the patient care.

• MeSH
• delece genu MeSH
• exony MeSH
• familiární adenomatózní polypóza genetika   MeSH
• fenotyp MeSH
• geny APC * MeSH
• lidé MeSH
• molekulární sekvence - údaje MeSH
• sekvence nukleotidů MeSH
• zárodečné mutace * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Česká republika MeSH
• Slovenská republika MeSH