A comprehensive search for mutations in the PKD1 and PKD2 in Japanese subjects with autosomal dominant polycystic kidney disease

To elucidate the genotypic and phenotypic characteristics of autosomal dominant polycystic kidney disease (ADPKD) in Japanese populations, we performed a comprehensive search for mutations in PKD1 and PKD2 in 180 Japanese ADPKD patients from 161 unrelated families. We identified 112 (89 PKD1 and 23 PKD2) mutations within 135 families. Patients with PKD2 mutations account for 23.6% of all Japanese ADPKD families in this study. Seventy‐five out of the 112 mutations have not been reported previously. The estimated glomerular filtration rate (eGFR) decline was significantly faster in patients with PKD1 mutations than in those with PKD2 mutations (?3.25 and ?2.08 ml min^?1 year^?1 for PKD1 and PKD2, respectively, p < 0.01). These results indicate that mutations within PKD1 and PKD2 can be linked to most of the cases of Japanese ADPKD, and the renal function decline was faster in patients with PKD1 mutations than in those with PKD2 mutations also in the Japanese ADPKD. We also found that PKD2 mutations were more frequent in Japanese ADPKD than that in European or American ADPKD.     

Mutation analysis in PKD1 of Japanese autosomal dominant polycystic kidney disease patients

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic renal disorder (incidence, 1:1,000). The mutation of PKD1 is thought to account for 85% of ADPKD. Although a considerable number of studies on PKD1 mutation have been published recently, most of them concern Caucasian ADPKD patients. In the present study, we examined PKD1 mutations in Japanese ADPKD patients. Long-range polymerase chain reaction (LR-PCR) with PKD1-specific primers followed by nested PCR was used to analyze the duplicated region of PKD1. Six novel chain-terminating mutations were detected: three nonsense mutations (Q2014X transition in exon 15, Q2969X in exon 24, and E2810X in exon 23), two deletions (2132del29 in exon10 and 7024delAC in exon 15), and one splicing mutation (IVS21-2delAG). There was also one nonconservative missense mutation (T2083I). Two other potentially pathogenic missense mutations (G2814R and L2816P) were on the downstream site of one nonsense mutation. These three mutations and a following polymorphism (8662C>T) were probably the result of gene conversion from one of the homologous genes to PKD1. Six other polymorphisms were found. Most PKD1 mutations in Japanese ADPKD patients were novel and definitely pathogenic. One pedigree did not link to either PKD1 or PKD2.     

Mutations of the PKD1 gene among Japanese autosomal dominant polycystic kidney disease patients, including one heterozygous mutation identified in members of the same family

More than 80 mutations of the PKD1 gene have been reported, mostly in patients from Western Europe. New techniques are being used to detect an increasing number of mutations, even in the homologous region of the PKD1 gene. Polymerase chain reaction–single-strand conformation polymorphism (PCR-SSCP) or denaturing high-performance liquid chromatography (DHPLC) analyses were performed in the present study to screen mutations from exon 23 to exon 46 in the PKD1 gene and in the entire PKD2 gene. When an abnormal pattern was found in PCR-SSCP or DHPLC, the PCR products were directly sequenced. Four mutations were identified in the PKD1 gene: a missense mutation (C47413T causing T3509M in exon 35), a splicing mutation (del 20 bp in 75 bp of intron 43), and two nonsense mutations (C48566A causing C3693X in exon 38, and C51237T causing Q4124X in exon 45). The nonsense mutation Q4124X existed in only two of three affected sib members in family K68. The pattern of the restriction enzyme digest and the haplotype analysis confirmed the presence of a heterozygous mutation in the family. Fifteen single nucleotide polymorphisms were identified in this study. Two of them (C50439A and C51659T) can be used as intragenic polymorphic markers. Received: April 21, 2001 / Accepted: June 11, 2001     

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.     

PKD2 gene mutation analysis in Korean autosomal dominant polycystic kidney disease patients using two-dimensional gene scanning

Autosomal dominant polycystic kidney disease (ADPKD) is genetically heterogeneous and is caused by mutations in the PKD1 or PKD2 genes. ADPKD caused by PKD2 mutations is characterized by a longer survival and a later onset of end-stage renal disease than ADPKD caused by PKD1 mutations. PKD2 encodes a 2.9-kb messenger RNA and is derived from 15 exons. Two-dimensional gene scanning (TDGS) is more efficient in detecting mutations in genes such as PKD2 because it can scan the whole coding regions simultaneously. In order to determine the prevalence of Korean PKD2 patients, all the coding sequences of PKD2 were screened using TDGS and direct sequencing in 46 randomly selected ADPKD patients (group 1). Another 45 ADPKD patients (group 2), who were presumed to be PKD2 patients, were screened in order to identify the type of mutation in the Korean PKD2 patients. Eight novel different mutations and three known mutations in the PKD2 gene were detected in 17 patients: 6 patients (13.0%) in group 1 and 11 patients (24.4%) in group 2. Considering the sensitivity of TDGS, the prevalence of PKD2 in Korean population might be greater than 18.6%. Both known and novel mutations were identified by TDGS in Korean PKD2 patients. Overall, these results showed that TDGS might be useful for diagnosing PKD2.     

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.     

Autosomal dominant polycystic kidney disease caused by somatic and germline mosaicism

Autosomal dominant polycystic kidney disease (ADPKD) is a heterogeneous genetic disorder caused by loss of function mutations of PKD1 or PKD2 genes. Although PKD1 is highly polymorphic and the new mutation rate is relatively high, the role of mosaicism is incompletely defined. Herein, we describe the molecular analysis of ADPKD in a 19‐year‐old female proband and her father. The proband had a PKD1 truncation mutation c.10745dupC (p.Val3584ArgfsX43), which was absent in paternal peripheral blood lymphocytes (PBL). However, very low quantities of this mutation were detected in the father's sperm DNA, but not in DNA from his buccal cells or urine sediment. Next generation sequencing (NGS) analysis determined the level of this mutation in the father's PBL, buccal cells and sperm to be ～3%, 4.5% and 10%, respectively, consistent with somatic and germline mosaicism. The PKD1 mutation in ～10% of her father's sperm indicates that it probably occurred early in embryogenesis. In ADPKD cases where a de novo mutation is suspected because of negative PKD gene testing of PBL, additional evaluation with more sensitive methods (e.g. NGS) of the proband PBL and paternal sperm can enhance detection of mosaicism and facilitate genetic counseling.     

Apparent normalisation of fetal renal size in autosomal dominant polycystic kidney disease (PKD1)

We present a family with adult onset autosomal dominant polycystic kidney disease (ADPKD) in two generations, linked to the PKD1 locus and with paternal transmission to the fetus. The fetus carried the PKD1 haplotype and was, therefore a gene carrier. Progressive hyperechogenic renal enlargement, but no cysts, was documented by serial fetal ultrasounds at 21, 23 and 34 weeks of gestation. Surprisingly, the newborn renal scan showed normal sized kidneys with apparently normal corticomedullary differentiation. However, at 11 months of age, the evolution of cysts in one kidney, and then in the other kidney at 20 months, was documented by ultrasound in the absence of clinical symptoms or signs. The observed normalisation of fetal renal ultrasound appearances at birth has not previously been described in fetuses presenting with PKD1.     

PKDB: Polycystic Kidney Disease Mutation Database--a gene variant database for autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) arises from mutations in the PKD1 and PKD2 genes. The Polycystic Kidney Disease Mutation Database (PKDB) is an internet-accessible relational database containing comprehensive information about germline and somatic disease-causing variants within these two genes, as well as polymorphisms and variants of indeterminate pathogenicity. The PKDB database structure incorporates an interface between these gene variant data and any associated patient clinical data. An initiative of the Polycystic Kidney Disease Foundation, PKDB is a publicly accessible database that aims to streamline the evaluation of PKD1 and PKD2 gene variants detected in samples from those with ADPKD, as well as to assist ongoing clinical and molecular research in the field. As the accurate reporting of nucleotide variants is essential for ensuring the quality of data within PKDB, a mutation checker has been mounted on the PKDB server allowing contributors to assess the accuracy of their PKD1 and PKD2 variant reports. Researchers and clinicians may submit their PKD1/PKD2 gene variants and any associated deidentified clinical data via standardized downloadable data entry forms accessible through the PKDB site. PKDB has been launched with the full details of PKD1 and PKD2 gene variant reports published in 73 peer-reviewed articles. Through a series of user-friendly advanced search facilities, users are able to query the database as required. The PKDB server is accessible at http://pkdb.mayo.edu.     

常染色体显性成人多囊肾病两家系PKD1、PKD2基因的突变鉴定

目的 鉴定两个常染色体显性成人多囊肾病家系的致病突变.方法 采用酚氯仿法提取家系成员及无亲缘关系的100名健康对照个体的外周血白细胞DNA,PCR扩增先证者致病基因PKD1、PKD2的所有外显子序列及其侧翼内含子剪切区域,直接测序确定DNA序列的变异.通过家系和正常对照的比较分析,对检测到的变异是否与疾病相关进行了初步探讨.结果 在两个家系中共检测到5个序列变异:PKD1:c.2469G＞A,PKD1:c.5014_5015 delAG,PKD1:c.10529C＞T,PKD2:c.568G＞A和PKD2:c.2020-1_2020 delAG.其中PKD1:c.2469G＞A和PKD2:c.2020-1_2020 delAG为新发现的变异.此外,检测到的移码突变和剪切突变未见于家系中健康成员及无亲缘关系的正常对照.结论 PKD1:c.5014_5015 delAG和PKD2:c.2020-1_2020 delAG分别为家系A和B的致病突变,且PKD2:c.2020-1_2020 delAG为先证者新发生的突变.     

Caffeine intake by patients with autosomal dominant polycystic kidney disease

Because caffeine may induce cyst and kidney enlargement in autosomal dominant polycystic kidney disease (ADPKD), we evaluated caffeine intake and renal volume using renal ultrasound in ADPKD patients. Caffeine intake was estimated by the average of 24-h dietary recalls obtained on 3 nonconsecutive days in 102 ADPKD patients (68 females, 34 males; 39 ± 12 years) and compared to that of 102 healthy volunteers (74 females, 28 males; 38 ± 14 years). The awareness of the need for caffeine restriction was assessed. Clinical and laboratory data were obtained from the medical records of the patients. Mean caffeine intake was significantly lower in ADPKD patients versus controls (86 vs 134 mg/day), and 63% of the ADPKD patients had been previously aware of caffeine restriction. Caffeine intake did not correlate with renal volume in ADPKD patients. There were no significant differences between the renal volumes of patients in the highest and lowest tertiles of caffeine consumption. Finally, age-adjusted multiple linear regression revealed that renal volume was associated with hypertension, chronic kidney disease stage 3 and the time since diagnosis, but not with caffeine intake. The present small cross-sectional study indicated a low level of caffeine consumption by ADPKD patients when compared to healthy volunteers, which was most likely due to prior awareness of the need for caffeine restriction. Within the range of caffeine intake observed by ADPKD patients in this study (0-471 mg/day), the renal volume was not directly associated with caffeine intake.     

Coexistence of autosomal dominant polycystic kidney disease type 1 and hereditary renal hypouricemia type 2: A model of early-onset and fast cyst progression

Autosomal dominant polycystic kidney disease (ADPKD) is a heterogeneous inherited disease characterized by renal and extrarenal manifestations with progressive fluid-filled cyst development leading to end-stage renal disease. The rate of disease progression in ADPKD exhibits high inter- and intrafamilial variability suggesting involvement of modifier genes and/or environmental factors. Renal hypouricemia (RHUC) is an inherited disorder characterized by impaired tubular uric acid transport with severe complications, such as acute kidney injury and chronic kidney disease (CKD). However, the two disorders have distinct and well-delineated genetic, biochemical, and clinical findings. Only a few cases of coexistence of ADPKD and RHUC (type 1) in a single individual have been reported. We report a family with two members: an ADPKD 24-year-old female which presented bilateral renal cysts in utero and hypouricemia since age 5, and her mother with isolated hypouricemia. Next-generation sequencing identified two mutations in two genes PKD1 and SLC2A9 in this patient and one isolated SLC2A9 mutation in her mother, showing RHUC type 2, associated to CKD. The coexistence of these two disorders provides evidence of SLC2A9 variant could act as a modifier change, with synergistic actions, that could promote cystogenesis and rapid ADPKD progression. This is the first case of coexistence of PKD1 and SLC2A9 mutations treated with tolvaptan.     

一个可能与PKD2基因连锁的常染色体显性多囊肾病家系

目的 研究常染色体显性多囊肾病（autosomal dominant polycystic kidney disease,ADPKD）在中国人中的遗传异质性。方法 采用聚合酶链反应 （polymerase chain reaction, PCR）、非变性聚丙烯酰胺凝胶电泳,检测了1个ADPKD家系各成员中与PKD1基因连锁的4种和与PKD2连锁的4种微卫星标记的基因分型。然后以软件辅助构建单倍型,并推测疾病单倍型。结果 发现该ADPKD家系中,与PKD1紧密连锁的4个微卫星KG8、SM6、CW4和CW2是有信息的;与PKD2基因紧密连锁的3种微卫星DNAIMS1563、D4S414和D4S423是有信息的。推定的单倍型提示,在这个家系中疾病可能与PKD2连锁,而不与PKD1连锁。结论 在此家系中,受累成员间存在表型异质性,并且有一个早发的儿童患者。与PKD2连锁的家系较少,这个家系的报道表明中国人中存在ADPKD的遗传异质性,PKD2的异常也可能会引起中国人ADPKD的发生。另外,发现有遗传早现现象存在,且疾病通过母亲传递。这提示在与PKD1不连锁的家系中后代可能早发病。     

Mutational analysis of PKD1 gene in a Chinese family with autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary disease and common renal disease. Mutations of PKD genes are responsible for this disease. We analyzed a large Chinese family with ADPKD using Sanger sequencing to identify the mutation responsible for this disease. The family comprised 27 individuals including 10 ADPKD patients. These ADPKD patients had severe renal disease and most of them died very young. We analyzed 6 survival patients gene and found they all had C10529T mutation in exon 35 of PKD1 gene. We did not found gene mutation in any unaffected relatives or 300 unrelated controls. These findings suggested that the C10529T mutation in PKD1 gene might be the pathogenic mutation responsible for the disease in this family.     

Echocardiographic findings in autosomal dominant polycystic kidney disease

Echocardiography, including Doppler analysis, was performed to assess the prevalence of cardiac abnormalities in 163 patients with autosomal dominant polycystic kidney disease, 130 unaffected family members, and 100 control subjects. In these three groups, the prevalence of mitral-valve prolapse was 26, 14, and 2 percent, respectively (P less than 0.0005). A higher prevalence of mitral incompetence (31, 14, and 9 percent, respectively; P less than 0.005), aortic incompetence (8, 3, and 1 percent, respectively; P less than 0.05), tricuspid incompetence (15, 7, and 4 percent, respectively; P less than 0.02), and tricuspid-valve prolapse (6, 2, and 0 percent, respectively; P less than 0.02) was also found in the patients with polycystic kidney disease. These findings reflect the systemic nature of polycystic kidney disease and support the hypothesis that the disorder involves a defect in the extracellular matrix and the cardiac abnormalities are an expression of that defect.     

Linkage heterogeneity of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease has been shown to be closely linked to the alpha-hemoglobin complex on the short arm of chromosome 16. We describe a five-generation kindred, descendants of Sicilian immigrants, in which the disease occurs but without linkage to the alpha-hemoglobin complex. DNA probes were used in genetic-linkage studies on blood samples from 163 family members, of whom 71 were affected by or at risk for autosomal dominant polycystic kidney disease. Diagnoses were confirmed by ultrasound examination. In this family the frequency of recombination between the alpha-hemoglobin complex and the region previously shown to contain the mutation causing polycystic kidney disease exceeded 24 percent, indicating a mutation at a different locus. The clinical findings in this family were indistinguishable from those in other families with polycystic kidney disease. We conclude that there is a second gene for autosomal dominant polycystic kidney disease. This apparent heterogeneity means that prenatal and presymptomatic diagnosis must be approached with caution until a method is found to distinguish between the two forms of the disease.