New mutations in the PKD1 gene in Czech population with autosomal dominant polycystic kidney disease

<p>Abstract</p> <p>Background</p> <p>Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease. The disease is caused by mutations of the <it>PKD1 </it>(affecting roughly 85% of ADPKD patients) and <it>PKD2 </it>(affecting roughly 14% of ADPKD patients) genes, although in several ADPKD families, the <it>PKD1 </it>and/or <it>PKD2 </it>linkage was not found. Mutation analysis of the <it>PKD1 </it>gene is complicated by the presence of highly homologous genomic duplications of the first two thirds of the gene.</p> <p>Methods</p> <p>The direct detection of mutations in the non-duplicated region of the <it>PKD1 </it>gene was performed in 90 unrelated individuals, consisting of 58 patients with end-stage renal failure (manifesting before their 50^thyear of life) and 32 individuals from families where the disease was clearly linked to the <it>PKD1 </it>gene. Mutation screening was performed using denaturing gradient gel electrophoresis (DGGE). DNA fragments showing an aberrant electrophoretic banding pattern were sequenced.</p> <p>Results</p> <p>In the non-duplicated region of the <it>PKD1 </it>gene, 19 different likely pathogenic germline sequence changes were identified in 19 unrelated families/individuals. Fifteen likely pathogenic sequence changes are unique for the Czech population. The following probable mutations were identified: 9 nonsense mutations, 6 likely pathogenic missense mutations, 2 frameshifting mutations, one in-frame deletion and probable splice site mutation. In the non-duplicated region of the <it>PKD1 </it>gene, 16 different polymorphisms or unclassified variants were detected.</p> <p>Conclusion</p> <p>Twenty probable mutations of the <it>PKD1 </it>gene in 90 Czech individuals (fifteen new probable mutations) were detected. The establishment of localization and the type of causal mutations and their genotype phenotype correlation in ADPKD families will improve DNA diagnosis and could help in the assessment of the clinical prognosis of ADPKD patients.</p

Novel APC mutations in Czech and Slovak FAP families: clinical and genetic aspects

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