Novel and de novo PKD1 mutations identified by multiple restriction fragment-single strand conformation polymorphism (MRF-SSCP)

Genetic Characteristics of Korean Patients with Autosomal Dominant Polycystic Kidney Disease by Targeted Exome Sequencing

Autosomal dominant polycystic kidney disease (ADPKD) is one of the main causes of end-stage renal disease (ESRD). Genetic information is of the utmost importance in understanding pathogenesis of ADPKD. Therefore, this study aimed to demonstrate the genetic characteristics of ADPKD and their effects on renal function in 749 Korean ADPKD subjects from 524 unrelated families. Genetic studies of PKD1/2 were performed using targeted exome sequencing combined with Sanger sequencing in exon 1 of the PKD1 gene and a multiple ligation probe assay. The mutation detection rate was 80.7% (423/524 families, 331 mutations) and 70.7% was novel. PKD1 protein-truncating (PKD1-PT) genotype was associated with younger age at diagnosis, larger kidney volume, lower renal function compared to PKD1 non-truncating and PKD2 genotypes. The PKD1 genotype showed earlier onset of ESRD compared to PKD2 genotype (64.9 vs. 72.9 years old, P < 0.001). In frailty model controlled for age, gender, and familial clustering effect, PKD2 genotype had 0.2 times lower risk for reaching ESRD than PKD1-PT genotype (p = 0.037). In conclusion, our results suggest that genotyping can contribute to selecting rapid progressors for new emerging therapeutic interventions among Koreans.

Identification of PKD1 and PKD2 gene variants in a cohort of 125 Asian Indian patients of ADPKD

Autosomal Dominant Polycystic Kidney Disease (ADPKD) accounts for 2.6% of the patients with chronic kidney disease in India. ADPKD is caused by pathogenic variants in either PKD1 or PKD2 gene. There is no comprehensive genetic data from Indian subcontinent. We aimed to identify the pathogenic variants in the heterogeneous Indian population. PKD1 and PKD2 variants were identified by direct gene sequencing and/or multiplex ligation-dependent probe amplification (MLPA) in 125 unrelated patients of ADPKD. The pathogenic potential of the variants was evaluated computationally and were classified according to ACMG guidelines. Overall 300 variants were observed in PKD1 and PKD2 genes, of which 141 (47%) have been reported previously as benign. The remaining 159 variants were categorized into different classes based on their pathogenicity. Pathogenic variants were observed in 105 (84%) of 125 patients, of which 99 (94.3%) were linked to PKD1 gene and 6 (6.1%) to PKD2 gene. Of 159 variants, 97 were novel variants, of which 43 (44.33%) were pathogenic, and 10 (10.31%) were of uncertain significance. Our data demonstrate the diverse genotypic makeup of single gene disorders in India as compared to the West. These data would be valuable in counseling and further identification of probable donors among the relatives of patients with ADPKD.

Autosomal dominant polycystic kidney disease: comprehensive mutation analysis of PKD1 and PKD2 in 700 unrelated patients

Autosomal dominant polycystic kidney disease (ADPKD), the most common inherited kidney disorder, is caused by mutations in PKD1 or PKD2. The molecular diagnosis of ADPKD is complicated by extensive allelic heterogeneity and particularly by the presence of six highly homologous sequences of PKD1 exons 1-33. Here, we screened PKD1 and PKD2 for both conventional mutations and gross genomic rearrangements in up to 700 unrelated ADPKD patients--the largest patient cohort to date--by means of direct sequencing, followed by quantitative fluorescent multiplex polymerase chain reaction or array-comparative genomic hybridization. This resulted in the identification of the largest number of new pathogenic mutations (n = 351) in a single publication, expanded the spectrum of known ADPKD pathogenic mutations by 41.8% for PKD1 and by 23.8% for PKD2, and provided new insights into several issues, such as the population-dependent distribution of recurrent mutations compared with founder mutations and the relative paucity of pathogenic missense mutations in the PKD2 gene. Our study, together with others, highlights the importance of developing novel approaches for both mutation detection and functional validation of nondefinite pathogenic mutations to increase the diagnostic value of molecular testing for ADPKD.

High Resolution Melt analysis for mutation screening in PKD1 and PKD2

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disorder. It is characterized by focal development and progressive enlargement of renal cysts leading to end-stage renal disease. PKD1 and PKD2 have been implicated in ADPKD pathogenesis but genetic features and the size of PKD1 make genetic diagnosis tedious.

METHODS

We aim to prove that high resolution melt analysis (HRM), a recent technique in molecular biology, can facilitate molecular diagnosis of ADPKD. We screened for mutations in PKD1 and PKD2 with HRM in 37 unrelated patients with ADPKD.

RESULTS

We identified 440 sequence variants in the 37 patients. One hundred and thirty eight were different. We found 28 pathogenic mutations (25 in PKD1 and 3 in PKD2 ) within 28 different patients, which is a diagnosis rate of 75% consistent with literature mean direct sequencing diagnosis rate. We describe 52 new sequence variants in PKD1 and two in PKD2.

CONCLUSION

HRM analysis is a sensitive and specific method for molecular diagnosis of ADPKD. HRM analysis is also costless and time sparing. Thus, this method is efficient and might be used for mutation pre-screening in ADPKD genes.

Ex vivo hepatic venography for hepatocellular carcinoma in livers explanted for liver transplantation

Background

Hepatocellular carcinoma (HCC) is supposed to have a venous drainage system to a portal vein, which makes intrahepatic metastasis possible. However, the mechanism of extrahepatic recurrence, including the possibility of a direct route to the systemic circulation from the HCC nodules, remains unclear. Therefore, we performed retrograde hepatic venography for HCC in livers that had been explanted for liver transplantation in order to explore the possible direct connection between the hepatic vein and HCC nodules.

Methods

Of 105 living-donor liver transplantations (LDLT) performed up to July, 2009 at the Department of Surgery, Nagasaki University Hospital, dynamic hepatic venography was performed with contrast media under fluoroscopy for the most recent 13 cases with HCC. The presence of a tumor stain for each HCC case was evaluated and compared with the histological findings of HCC.

Results

Hepatic venography revealed a tumor stain in 2 of 13 cases (15%). Neither showed any microscopic tumor invasion of HCC into the hepatic vein. In the other 11 cases, there were 4 microscopic portal venous invasions and 2 microscopic hepatic venous invasions. No patients have shown HCC recurrence in follow-up (median period, 13 months).

Conclusion

Using ex vivo hepatic venography, a direct connection to the hepatic vein from HCC in whole liver was revealed in 2 cases without demonstrated histopathological invasion to hepatic vein for the first time in the literature. The finding suggests that there is direct spillage of HCC cells into the systemic circulation via hepatic vein.

PKD1 and PKD2 mutations in Slovenian families with autosomal dominant polycystic kidney disease

Background

Autosomal dominant polycystic kidney disease (ADPKD) is a genetically heterogeneous disorder caused by mutations in at least two different loci. Prior to performing mutation screening, if DNA samples of sufficient number of family members are available, it is worthwhile to assign the gene involved in disease progression by the genetic linkage analysis.

Methods

We collected samples from 36 Slovene ADPKD families and performed linkage analysis in 16 of them. Linkage was assessed by the use of microsatellite polymorphic markers, four in the case of PKD1 (KG8, AC2.5, CW3 and CW2) and five for PKD2 (D4S1534, D4S2929, D4S1542, D4S1563 and D4S423). Partial PKD1 mutation screening was undertaken by analysing exons 23 and 31–46 and PKD2 .

Results

Lod scores indicated linkage to PKD1 in six families and to PKD2 in two families. One family was linked to none and in seven families linkage to both genes was possible. Partial PKD1 mutation screening was performed in 33 patients (including 20 patients from the families where linkage analysis could not be performed). We analysed PKD2 in 2 patients where lod scores indicated linkage to PKD2 and in 7 families where linkage to both genes was possible. We detected six mutations and eight polymorphisms in PKD1 and one mutation and three polymorphisms in PKD2.

Conclusion

In our study group of ADPKD patients we detected seven mutations: three frameshift, one missense, two nonsense and one putative splicing mutation. Three have been described previously and 4 are novel. Three newly described framesfift mutations in PKD1 seem to be associated with more severe clinical course of ADPKD. Previously described nonsense mutation in PKD2 seems to be associated with cysts in liver and milder clinical course.