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

Abstract

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.

Comprehensive PKD1 and PKD2 Mutation Analysis in Prenatal Autosomal Dominant Polycystic Kidney Disease

“…16,20,21 In addition, the average age at ESRD in the affected relatives in our series is earlier than in a larger cohort of ADPKD patients carrying a PKD1 mutation. 5 In particular, the age at ESRD in affected ancestors carrying a nontruncating mutation was 54.3 years (vs 67.9 years as reported by Cornec-Le Gall and colleagues 5 ).…”

“…Molecular testing of PKD1, PKD2, and HNF1B genes was performed by direct sequencing, followed by quantitative fluorescent multiplex PCR, Multiplex Ligation-Dependent Probe Amplification (MRC-Holland), and array-comparative genomic hybridization, as previously described 16 in all but one index patients (as fetal DNA was degraded). When variations were identified, both parents were tested for the variations.…”

“…Finally, no HNF1B mutation was detected in this series. To evaluate the frequency of additional variations in PKD1 in a population of patients affected with classic (with first symptoms in adulthood) ADPKD, we went back to 174 patients of an in-house adult cohort 5,16 for whom the complete exploration of the PKD1 gene was completed. In addition to the polymorphic variants known to be frequent in PKD1 (9.05 per patient on average), we identified other rare variants, not described in the common databases (the Single Nucleotide Polymorphism Database and the Exome Sequencing Project) and predicted to be pathogenic, in only 25 (14.4%) out of these 174 patients, including the patients carrying the three variations previously mentioned (Supplemental Table 3).…”

Whole-genome sequencing overcomes pseudogene homology to diagnose autosomal dominant polycystic kidney disease

“…1,5,6 This technique has a diagnostic rate of approximately 90% in well-phenotyped trial cohorts and 40-60% in the commercial reference laboratory. [7][8][9] The technique is labour intensive and thus expensive. More recently, targeted massively parallel sequencing (MPS) has been used to sequence PKD1 and PKD2.…”

The Mutation, a Key Determinant of Phenotype in ADPKD

“…8 A number of other likely hypomorphic PKD1 and PKD2 alleles found alone, in homozygosity or as a compound heterozygote have been identified in mild or early onset ADPKD cases. [9][10][11] The study by Audrézet et al 12 and the related PKD1 genotype/phenotype study of Cornec-Le Gall et al 13 in this issue of JASN describe the largest ADPKD mutation screening with correlation to phenotype yet described, involving patients from the Brittany region of France. The original screen found definite or likely mutations in 627 of 700 families (approximately 90%), with 83.8% and 16.2% of mutation characterized cases being PKD1 and PKD2, respectively; 388 and 54 different PKD1 and PKD2 mutations were described, respectively.…”