Genetic heterogeneity in Korean families with autosomal-dominant polycystic kidney disease (ADPKD): the first Asian report

Novel PKD1 Mutations in Patients with Autosomal Dominant Polycystic Kidney Disease

OBJECTIVE

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease. Identifying mutated causative genes can provide diagnostic and prognostic information. In this study, we describe the clinical application of a next generation sequencing (NGS)-based, targeted multi-gene panel test for the genetic diagnosis of patients with ADPKD.

METHODS

We applied genetic analysis on 26 unrelated known or suspected patients with ADPKD. A total of 10 genes related to cystic change of kidney were targeted. Detected variants were classified according to standard guidelines.

RESULTS

We identified 19 variants (detection rate: 73.1%), including PKD1 (n = 18) and PKD2 (n = 1). Of the 18 PKD1 variants, 8 were novel.

CONCLUSION

Multigene panel test can be a comprehensive tool in a clinical setting for genetic diagnosis of ADPKD. It allows us to identify clinically significant novel variants and confirm the diagnosis, and these objectives are difficult to achieve using conventional diagnostic tools.

Heterozygosity analysis of polycystic kidney disease 1 gene microsatellite markers for linkage analysis of autosomal dominant polycystic kidney disease type 1 in the Iranian population

Background:

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic cause of end-stage renal disease. Although imaging techniques are a means of accurate diagnosis when the cysts appear in the third or fourth decades of the patient's life, they are of little value for early diagnosis. Genetic tests are required for preimplantation genetic diagnosis, decision-making for kidney donation to an affected relative. Although mutation of the polycystic kidney disease (PKD1) gene is solely responsible for the most cases of ADPKD, direct genetic testing is limited by the large size of this gene and the presence of many mutations without hot spots. Therefore, indirect diagnosis with linkage analysis using informative microsatellite markers has been suggested.

Materials and Methods:

In this study, we assessed the informativeness of the PKD1 gene markers D16S475, D16S291, and D16S3252 in Iranian population. Using specific primers, fluorescent polymerase chain reaction (PCR) was performed on genomic DNA extracted from fifty unrelated individuals. PCR products were analyzed by the ALFexpress DNA sequencer system, and the number and frequency of alleles were determined to calculate the heterozygosity (HET) and polymorphism information content (PIC) values.

Results:

We found that the HET and PIC values for the D16S475 marker are 0.92 and 0.91, respectively. These two values are 0.82 and 0.80 for D16S291 and 0.50 and 0.47 for D16S3252, respectively.

Conclusion:

Based on this data, D16S475 and D16S291 are highly and D16S3252 is moderately informative for indirect genetic diagnosis of PKD1 mutations in this population.

Association of intracranial aneurysms and meningiomas: a case-control study

OBJECT

The authors aimed to assess whether the prevalence of intracranial aneurysms in patients with intracranial meningiomas was higher than that in a healthy population.

METHODS

The authors performed a hospital-based case-control study of 300 patients with newly diagnosed intracranial meningiomas and 900 age- and sex-matched controls without a history of brain tumors to evaluate any associations between intracranial aneurysms and intracranial meningiomas. Unconditional multivariate logistic regression models were used for case-control comparisons.

RESULTS

Intracranial aneurysms were identified in 23 patients (7.7%) and 24 controls (2.7%; p < 0.001). There was a significant association between intracranial aneurysms and intracranial meningiomas (OR 2.913, 95% CI 1.613–5.261) and hypertension (OR 1.905, 95% CI 1.053–3.446). In a subgroup analysis of the patients with newly diagnosed intracranial meningiomas, there was a significant association between intracranial aneurysms and hypertension (OR 2.876, 95% CI 1.125–7.352) and tumor volume (OR 1.012, 95% CI 1.001–1.024). These patients were also more likely than controls to have other intracranial vascular diseases (p < 0.001), such as isolated occlusion of the intracranial vessels, excluding intracranial aneurysms.

CONCLUSIONS

The prevalence of intracranial aneurysms was higher in patients with intracranial meningiomas. Hypertension and tumor volume appear to be associated with the formation of intracranial aneurysms in these patients.

Identification of novel PKD1 and PKD2 mutations in Korean patients with autosomal dominant polycystic kidney disease

Background

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disorder. It is caused by mutations in the PKD1 and PKD2 genes, and manifests as progressive cyst growth and renal enlargement, resulting in renal failure. Although there have been a few studies on the frequency and spectrum of mutations in PKD1 and PKD2 in Korean patients with ADPKD, only exons 36–46, excluding the duplicated region, were analyzed, which makes it difficult to determine accurate mutation frequencies and mutation spectra.

Methods

We performed sequence analysis of 20 consecutive unrelated ADPKD patients using long-range polymerase chain reaction (PCR) to avoid pseudogene amplification, followed by exon-specific PCR and sequencing of the all exons of these two genes. Multiplex ligation-dependent probe amplification was performed in patients in whom pathogenic mutations in PKD1 or PKD2 were not identified by LR-PCR and direct sequencing to detect large genomic rearrangements.

Results

All patients met the diagnostic criteria of ADPKD, and pathogenic mutations were found in 18 patients (90.0%), comprising 15 mutations in PKD1 and three in PKD2. Among 10 novel mutations, eight mutations were found in the PKD1 gene while two mutations were found in the PKD2 gene. Eight of 14 PKD1 mutations (57.1%) were located in the duplicated region.

Conclusions

This study expands the spectra of mutations in the PKD1 and PKD2 genes and shows that the mutation frequencies of these genes in Korean ADPKD patients are similar to those reported in other ethnicities. Sequence analysis, including analysis of the duplicated region, is essential for molecular diagnosis of ADPKD.

Three novel mutations of the PKD1 gene in Korean patients with autosomal dominant polycystic kidney disease

Mutations at the PKD1 locus account for 85% of cases of the common genetic disorder called autosomal dominant polycystic kidney disease (ADPKD). Screening for mutations of the PKD1 gene is complicated by the genomic structure of the 5'-duplicated region encoding 75% of the gene. To date, more than 90 mutations of the PKD1 gene have been reported in the European and American populations, and relatively little information is available concerning the pattern of mutations present in the Asian populations. We looked for mutations of the PKD1 gene in 51 unrelated Korean ADPKD patients, using polymerase chain reaction (PCR) with primer pairs located in the 3' single-copy region of the PKD1 gene and by single-strand conformation polymorphism (SSCP) analysis. We found three novel mutations, a G to A substitution at nucleotide 11012 (G3601S), a C to A substitution at nucleotide 11312 (Q3701X), and a C to T substitution at nucleotide 12971 (P4254S), and a single polymorphism involving a G to C substitution at nucleotide 11470 (L3753L). These mutations were not found in control individuals, and no other mutations in the 3' single-copy region of the PKD1 gene of patients with these mutations were observed. In particular, P4254S segregated with the disease phenotype. The clinical data of affected individuals from this study, and of previously reported Korean PKD1 mutations, showed that patients with frameshift or nonsense mutations were more prone to develop end-stage renal failure than those with missense mutations. Our findings indicate that many different PKD1 mutations are likely to be responsible for ADPKD in the Korean population, as in the Western population.