Mutation detection of PKD1 identifies a novel mutation common to three families with aneurysms and/or very-early-onset disease

Endovascular Management of Renal Artery Pseudoaneurysm in Autosomal Dominant Polycystic Kidney Disease: A Case Report

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common hereditary kidney diseases. In addition to renal involvement, vascular complications including intracranial arterial, aortic aneurysms and dissections are common in these patients. We report the case of a 35-year-old male patient with ADPKD who presented with hematuria and was diagnosed with two intrarenal arterial pseudoaneurysms. Endovascular embolization using coils was performed to resolve these symptoms. Vascular complications are often encountered in patients with ADPKD; hence, sufficient clinical suspicion and timely diagnosis can help manage the disease. The most common causes of hematuria in ADPKD patients are cyst hemorrhage or infection; however, vascular aneurysms should also be considered a possibility.

Vascular Complications in Autosomal Dominant Polycystic Kidney Disease: Perspectives, Paradigms, and Current State of Play

Autosomal dominant polycystic kidney disease (ADPKD) is the leading cause of inherited kidney disease with significant contributions to CKD and end-stage kidney disease. The underlying polycystin proteins (PC1 and PC2) have widespread tissue expression and complex functional roles making ADPKD a systemic disease. Vascular complications, particularly intracranial aneurysms (ICA) are the most feared due to their potential for devastating neurological complications and sudden death. Intracranial aneurysms occur in 8-12% of all patients with ADPKD, but the risk is intensified 4-5-fold in those with a positive family history. The basis for this genetic risk is not well understood and could conceivably be due to features of the germline mutation with a significant contribution of other genetic modifiers and/or environmental factors. Here we review what is known about the natural history and genetics of unruptured ICA in ADPKD including the prevalence and risk factors for aneurysm formation and subarachnoid hemorrhage. We discuss two alternative screening strategies and recommend a practical algorithm that targets those at highest risk for ICA with a positive family history for screening.

Mutation Analysis of Autosomal-Dominant Polycystic Kidney Disease Patients

Autosomal-dominant polycystic kidney disease (ADPKD) is characterized by bilateral kidney cysts that ultimately lead to end-stage kidney disease. While the major causative genes of ADPKD are PKD1 and PKD2, other genes are also thought to be involved. Fifty ADPKD patients were analyzed by exome sequencing or multiplex ligation-dependent probe amplification (MLPA), followed by long polymerase chain reaction and Sanger sequencing. Variants in PKD1 or PKD2 or GANAB were detected in 35 patients (70%). Exome sequencing identified 24, 7, and 1 variants in PKD1, PKD2, and GANAB, respectively, in 30 patients. MLPA analyses identified large deletions in PKD1 in three patients and PKD2 in two patients. We searched 90 cyst-associated genes in 15 patients who were negative by exome sequencing and MLPA analyses, and identified 17 rare variants. Four of them were considered "likely pathogenic" or "pathogenic" variants according to the American College of Medical Genetics and Genomics guidelines. Of the 11 patients without a family history, four, two, and four variants were found in PKD1, PKD2, and other genes, respectively, while no causative gene was identified in one patient. While the pathogenicity of each variant in these genes should be carefully assessed, a comprehensive genetic analysis may be useful in cases of atypical ADPKD.

Diagnosis and Risk Factors for Intracranial Aneurysms in Autosomal Polycystic Kidney Disease: A cross-sectional study from the Genkyst Cohort

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is associated with an increased risk for developing intracranial aneurysms (IAs). We aimed to evaluate the frequency of diagnosis of IAs in the cross-sectional, population-based, Genkyst cohort, to describe ADPKD-associated IAs and to analyze the risk factors associated with the occurrence of IAs in ADPKD patients.

METHODS

Cross-sectional study performed in 26 nephrology centers from the Western part of France. All patients underwent genetic testing for PKD1/PKD2 and other cystogenes.

RESULTS

Among the 2449 Genkyst participants, 114 (4.65%) had a previous diagnosis of ruptured or unruptured IAs at inclusion, and ∼47% of them had a positive familial history for IAs. Most aneurysms were small and saccular and located in the anterior circulation; 26.3% of the patients had multiple IAs. The cumulative probabilities of a previous diagnosis of IAs were 3.9, 6.2 and 8.1% at 50, 60 and 70 y, respectively. While this risk appeared to be similar in male and female individuals <50 y, after that age, the risk continued to increase more markedly in female patients, reaching 10.8% vs 5.4% at 70 y. The diagnosis rate of IAs was more than twofold higher in PKD1 compared to PKD2 with no influence of PKD1 mutation type or location. In multivariate analysis, female sex, hypertension <35 y, smoking and PKD1 genotype were associated with an increased risk for diagnosis of IAs.

CONCLUSIONS

This study presents epidemiological data reflecting real-life clinical practice. The increased risk for IAs in postmenopausal women suggests a possible protective role of estrogen.

Identification of missense and synonymous variants in Iranian patients suffering from autosomal dominant polycystic kidney disease

Background

Autosomal dominant polycystic kidney disease (ADPKD), the predominant type of inherited kidney disorder, occurs due to PKD1 and PKD2 gene mutations. ADPKD diagnosis is made primarily by kidney imaging. However, molecular genetic analysis is required to confirm the diagnosis. It is critical to perform a molecular genetic analysis when the imaging diagnosis is uncertain, particularly in simplex cases (i.e. a single occurrence in a family), in people with remarkably mild symptoms, or in individuals with atypical presentations. The main aim of this study is to determine the frequency of PKD1 gene mutations in Iranian patients with ADPKD diagnosis.

Methods

Genomic DNA was extracted from blood samples from 22 ADPKD patients, who were referred to the Qaem Hospital in Mashhad, Iran. By using appropriate primers, 16 end exons of PKD1 gene that are regional hotspots, were replicated with PCR. Then, PCR products were subjected to DNA directional Sanger sequencing.

Results

The DNA sequencing in the patients has shown that exons 35, 36 and 37 were non- polymorphic, and that most mutations had occurred in exons 44 and 45. In two patients, an exon-intron boundary mutation had occurred in intron 44. Most of the variants were missense and synonymous types.

Conclusion

In the present study, we have shown the occurrence of nine novel missense or synonymous variants in PKD1 gene. These data could contribute to an improved diagnostic and genetic counseling in clinical settings.

Mutational screening of PKD1 and PKD2 in Indian ADPKD patients identified 95 genetic variants

BACKGROUND

Mutation screening of autosomal dominant polycystic kidney disease (ADPKD) cases imply the major involvement of PKD1 mutations in 85% of patients while rest of the cases harbor mutation in PKD2, DNAJB11 and GANAB. This essentially indicates that individual's genotype holds the key for disease susceptibility and its severity.

METHODS

For finding genetic variability underlying the disease pathophysiology, 84 Indian ADPKD cases, 31 family members (12 susceptible) and 122 age matched control were screened for PKD1 and PKD2 using Sanger sequencing, PCR-RFLP and ARMS-PCR.

RESULTS

Genetic screening of Indian ADPKD cases revealed total 67 variants in PKD1 and 28 variants in PKD2. Among the identified variants in PKD1 and PKD2 genes, 35.79% were novel variants and 64.2% recurrent. Further, subcategorization of PKD1 variants showed 14 truncation/frameshift, 21 nonsynonymous, 25 synonymous and 7 intronic variants. Moreover, we observed 40 families with PKD1 pathogenic variants, 7 families with PKD2 pathogenic variants, 9 families with PKD1 & PKD2 pathogenic variants, and 26 families with PKD1/PKD2/PKD1-PKD2 non-pathogenic genetic variants.

CONCLUSION

Present study represented genetic background of Indian ADPKD cases which will be helpful in disease management as well as finding the genetically matched donor for kidney transplant.

28 novel mutations identified from 33 Chinese patients with cilia-related kidney disorders

BACKGROUND

Cilia play an important role in cellular signaling pathways. Defective ciliary function causes a variety of disorders involve retina, skeleton, liver, kidney or others. Cilia-related kidney disorders are characterized by cystic renal disease, nephronophthisis and renal failure in general.

METHODS

In this study, we collected 33 families clinically suspected of cilia-related kidney disorders. Capture-based next-generation sequencing (NGS) of 88 related genes, Sanger sequencing, pedigree analysis and functional study were performed to analyze their genetic cause.

RESULTS

40 mutations in PKD1, PKD2, PKHD1, DYNC2H1 and TMEM67 genes were identified from 27 of 33 affected families. 70% (28/40) of the mutations were first found in patients. We reported a very early-onset autosomal dominant polycystic kidney disease (ADPKD) family caused by a novel heterozygous PKD1 mutation; another fetus with DYNC2H1 compound heterozygous missense mutations showed mainly kidney dysplasia instead of skeletal abnormalities; and a novel PKD1 mutation, c.12445-3C > G, was confirmed to cause two wrong splicing modes. As for previously reported mutations, such as PKD1, c.6395 T > G (p.F2132C) and c.6868G > T (p.D2290Y), we had new and different findings.

CONCLUSION

The findings provided new references for genotype-phenotype analyses and broadened the mutation spectrum of detected genes, which were significantly valuable for prenatal diagnosis and genetic counseling.

Identifying gene mutations of Chinese patients with polycystic kidney disease through targeted next-generation sequencing technology

BACKGROUND

Polycystic kidney disease (PKD) is the most common hereditary kidney disease. The main mutational genes causing autosomal dominant polycystic kidney disease (ADPKD) are PKD1 and PKD2 as well as some rare pathogenic genes. Unilateral PKD is rare in clinics, and its association with gene mutations is unclear.

METHODS

Targeted next-generation sequencing (NGS) was performed to detect the renal ciliopathy-associated genes (targeted NGS panel including 63 genes) in PKD patients.

RESULTS

Forty-eight PKD1 and PKD2 mutation sites were detected in 44 bilateral PKD patients, of which 48 were PKD1 mutation sites (87.5%) and six were PKD2 mutation sites (12.5%). All of which exhibited typical ADPKD. Furthermore, we detected HNF1B heterozygous mutations in three families. Although these three patients showed HNF1B heterozygous mutations, their clinical characteristics differed and showed phenotypic heterogeneity.

CONCLUSIONS

Targeted NGS panel was helpful in detecting typical ADPKD patients and even in non-typical PKD patients. Macromutation in HNF1B may lead to bilateral PKD. The 16 novel PKD gene mutation sites and two novel PKD2 gene mutation sites discovered in this study have some significance in genetic counseling for ADPKD patients, and increase the number of studied families and expand the mutation database of ADPKD.

Mutation analyses by next-generation sequencing and multiplex ligation-dependent probe amplification in Japanese autosomal dominant polycystic kidney disease patients

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD), one of the most common hereditary kidney diseases, causes gradual growth of cysts in the kidneys, leading to renal failure. Owing to the advanced technology of next-generation sequencing (NGS), genetic analyses of the causative genes PKD1 and PKD2 have been improved.

METHODS

We performed genetic analyses of 111 Japanese ADPKD patients using hybridization-based NGS and long-range (LR)-PCR-based NGS. Additionally, genetic analyses in exon 1 of PKD1 using Sanger sequencing because of an extremely low coverage of NGS and those using multiplex ligation-dependent probe amplification (MLPA) were performed.

RESULTS

The detection rate using NGS for 111 patients was 86.5%. One mutation in exon 1 of PKD1 and five deletions detected by MLPA were identified. When combined, the total detection rate was 91.9%.

CONCLUSION

Although NGS is useful, we propose the addition of Sanger sequencing for exon 1 of PKD1 and MLPA as indispensable for identifying mutations not detected by NGS.

Identification of novel mutations and risk assessment of Han Chinese patients with autosomal dominant polycystic kidney disease

AIM

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease in humans and is caused by mutations in the PKD1 or PKD2 gene. ADPKD is heterogeneous with regard to locus and allele heterogeneity and phenotypic variability.

METHODS

Using targeted capture associated with next generation sequencing (NGS), we performed a mutational analysis of Han Chinese patients with ADPKD from 62 unrelated families. Multivariate Cox proportional hazard modelling of their different clinical characteristics and mutation classes was performed.

RESULTS

The detection rate for a PKD1 and PKD2 mutation in the Chinese ADPKD patients was 95.2% (59/62). We identified pathogenic mutations in 64.4% (38/59) of patients, including 32PKD1 mutations (15 nonsense mutations, 15 frameshift mutation, one splice mutation, and one large deletion) and six PKD2 mutations (three nonsense mutations and three frameshift mutations). Of the pathogenic variants we identified, 50% (19/38) were novel variants and 50% (19/38) were known variants. Patients with PKD2 mutations had milder and indistinguishable phenotypes. Significant phenotypic differences were observed among the various types of PKD1 mutations.

CONCLUSION

Our results show that targeted capture associated with next-generation sequencing is an effective strategy for genetically testing ADPKD patients. This mutation analysis of ADPKD in Han Chinese extends our understanding of the genetic diversity of different ethnic groups, enriches the mutation database, and contributes to the genetic counselling of ADPKD patients.

Identification of Three Novel Frameshift Mutations in the PKD1 Gene in Iranian Families with Autosomal Dominant Polycystic Kidney Disease Using Efficient Targeted Next-Generation Sequencing

BACKGROUND/AIMS

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited cystic kidney diseases caused by mutations in two large multi-exon genes, PKD1 and PKD2. High allelic heterogeneity and duplication of PKD1 exons 1-32 as six pseudo genes on chromosome 16 complicate molecular analysis of this disease.

METHODS

We applied targeted next-generation sequencing (NGS) in 9 non-consanguineous unrelated Iranian families with ADPKD to identify the genes hosting disease-causing mutations. This approach was confirmed by Sanger sequencing.

RESULTS

Here, we determined three different novel frameshift mutations and four previously reported nonsense mutations in the PKD1 gene encoding polycystin1 in heterozygotes.

CONCLUSION

This study demonstrates the effectiveness of NGS in significantly reducing the cost and time for simultaneous sequence analysis of PKD1 and PKD2, simplifying the genetic diagnostics of ADPKD. Although a probable correlation between the mutation types and phenotypic outcome is possible, however for more extensive studies in future, the consideration of renal hypouricemia (RHUC) and PKD1 coexistence may be helpful. The novel frameshift mutations reported by this study are p. Q1997X, P. D73X and p. V336X.

Flow Diverter Treatment of Tandem Intracranial Aneurysms

OBJECTIVE

To assess technical success and clinical and imaging outcomes of flow diversion (FD) treatment of multiple, tandem intracranial aneurysms.

METHODS

Retrospective analysis was performed of patients treated with FD for tandem intracranial aneurysms.

RESULTS

Twenty female patients with a mean (±SD) age of 60 (±12) years were included. One patient was treated after subarachnoid hemorrhage. In 22 separate procedures, 47 aneurysms, all located in the intracranial internal carotid artery, were treated. In 3 cases, treatment was performed for aneurysm recurrence after previous endovascular treatment. All aneurysms were successfully treated in 1 session. A single stent was used in most (82%) cases, with no adjunctive coiling. There were no intraprocedural complications. Three patients experienced mild, transient neurologic symptoms after the procedure with no long-term neurologic deficits. Follow-up imaging with digital subtraction angiography and/or contrast-enhanced magnetic resonance angiography was available in 18/20 (90%) patients at an average (±SD) of 18.8 (±11.2) months. Of 40 aneurysms with follow-up imaging, 34 (85%) were completely occluded. Clinical follow-up, available in 20/20 (100%) patients, showed that 19/20 (95%) achieved a modified Rankin Scale score of 0-2. There were no cases of aneurysm rupture after treatment, and no patients required retreatment at last available follow-up.

CONCLUSIONS

FD appears technically feasible, safe, and effective for treatment of tandem intracranial aneurysms, with potential advantages over traditional endovascular or surgical treatment modalities. Larger studies are needed to confirm these findings.

Vascular complications in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease. Relentless cyst growth substantially enlarges both kidneys and culminates in renal failure. Patients with ADPKD also have vascular abnormalities; intracranial aneurysms (IAs) are found in ∼10% of asymptomatic patients during screening and in up to 25% of those with a family history of IA or subarachnoid haemorrhage. As the genes responsible for ADPKD—PKD1 and PKD2—have complex integrative roles in mechanotransduction and intracellular calcium signalling, the molecular basis of IA formation might involve focal haemodynamic conditions exacerbated by hypertension and altered flow sensing. IA rupture results in substantial mortality, morbidity and poor long-term outcomes. In this Review, we focus mainly on strategies for screening, diagnosis and treatment of IAs in patients with ADPKD. Other vascular aneurysms and anomalies—including aneurysms of the aorta and coronary arteries, cervicocephalic and thoracic aortic dissections, aortic root dilatation and cerebral dolichoectasia—are less common in this population, and the available data are insufficient to recommend screening strategies. Treatment decisions should be made with expert consultation and be based on a risk-benefit analysis that takes into account aneurysm location and morphology as well as patient age and comorbidities.

Endovascular management of adjacent tandem intracranial aneurysms: utilization of stent-assisted coiling and flow diversion

BACKGROUND

Tandem intracranial aneurysms are aneurysms located along a single intracranial vessel. Adjacent tandem aneurysms arise within the same vascular segment and their presence often suggests diffuse parent vessel anomaly. Endovascular management of these rare lesions has not been well studied. In this retrospective observational study, we describe our experience treating adjacent tandem intracranial aneurysms with endovascular embolization.

METHODS

We retrospectively reviewed records of patients with these lesions who underwent endovascular treatment between 2008 and 2013.

RESULTS

Thirteen patients (mean age 60.8 years; 12 women) with 28 adjacent tandem aneurysms were treated during the study timeframe. Aneurysms were located along the clinoidal, ophthalmic, and communicating segments of the internal carotid artery in 12 patients and at the basilar apex in one patient. Average size was 8.4 mm. Six patients (12 aneurysms) were treated by flow diversion via the Pipeline embolization device (PED) and seven (16 aneurysms) by stent-assisted coiling, with coils successfully placed in 11 aneurysms. Clinical follow-up was available for an average of 26.1 months; postprocedural angiography was performed for 12 patients. Complete occlusion was achieved in nine of ten (90 %) PED-treated aneurysms and eight of 11 (72.7 %) treated by stent-assisted coiling (p = 0.44). Two patients treated by stent-assisted coiling required re-coiling for aneurysm recanalization. Overall, modified Rankin scale scores were 0-1 for 12 patients and 3 for one patient.

CONCLUSIONS

Adjacent tandem intracranial aneurysms can be safely and effectively treated by either stent-assisted coiling or flow diversion. We prefer PED flow diversion due to better parent vessel reconstruction and lower recanalization risk.

A Pkd1-Fbn1 genetic interaction implicates TGF-β signaling in the pathogenesis of vascular complications in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a common cause of renal failure that is due to mutations in two genes, PKD1 and PKD2. Vascular complications, including aneurysms, are a well recognized feature of ADPKD, and a subgroup of families exhibits traits reminiscent of Marfan syndrome (MFS). MFS is caused by mutations in fibrillin-1 (FBN1), which encodes an extracellular matrix protein with homology to latent TGF-β binding proteins. It was recently demonstrated that fibrillin-1 deficiency is associated with upregulation of TGF-β signaling. We investigated the overlap between ADPKD and MFS by breeding mice with targeted mutations in Pkd1 and Fbn1. Double heterozygotes displayed an exacerbation of the typical Fbn1 heterozygous aortic phenotype. We show that the basis of this genetic interaction results from further upregulation of TGF-β signaling caused by Pkd1 haploinsufficiency. In addition, we demonstrate that loss of PKD1 alone is sufficient to induce a heightened responsiveness to TGF-β. Our data link the interaction of two important diseases to a fundamental signaling pathway.

Epidemiology and genetics of intracranial aneurysms

Intracranial aneurysms are acquired lesions (5-10% of the population), a fraction of which rupture leading to subarachnoid hemorrhage with devastating consequences. Until now, the exact etiology of intracranial aneurysms formation remains unclear. The low incidence of subarachnoid hemorrhage in comparison with the prevalence of unruptured IAs suggests that the vast majority of intracranial aneurysms do not rupture and that identifying those at highest risk is important in defining the optimal management. The most important factors predicting rupture are aneurysm size and site. In addition to ambiental factors (smoking, excessive alcohol consumption and hypertension), epidemiological studies have demonstrated a familiar influence contributing to the pathogenesis of intracranial aneurysms, with increased frequency in first- and second-degree relatives of people with subarachnoid hemorrhage. In comparison to sporadic aneurysms, familial aneurysms tend to be larger, more often located at the middle cerebral artery, and more likely to be multiple. Other than familiar occurrence, there are several heritable conditions associated with intracranial aneurysm formation, including autosomal dominant polycystic kidney disease, neurofibromatosis type I, Marfan syndrome, multiple endocrine neoplasia type I, pseudoxanthoma elasticum, hereditary hemorrhagic telangiectasia, and Ehlers-Danlos syndrome type II and IV. The familial occurrence and the association with heritable conditions indicate that genetic factors may play a role in the development of intracranial aneurysms. Genome-wide linkage studies in families and sib pairs with intracranial aneurysms have identified several loci on chromosomes showing suggestive evidence of linkage, particularly on chromosomes 1p34.3-p36.13, 7q11, 19q13.3, and Xp22. For the loci on 1p34.3-p36.13 and 7q11, a moderate positive association with positional candidate genes has been demonstrated (perlecan gene, elastin gene, collagen type 1 A2 gene). Moreover, 3 of the polymorphisms analyzed in 2 genes (endothelial nitric oxide synthase T786C, interleukin-6 G572C, and interleukin-6 G174C) were found to be significantly associated with ruptured/unruptured aneurysms: the endothelial nitric oxide synthase gene single-nucleotide polymorphisms increased the risk, while IL-6 G174C seemed protective. More recently, two genomic loci (endothelin receptor A and cyclin-dependent kinase inhibitor 2BAS) have been found to be significantly associated with intracranial aneurysms in the Japanese population; endothelin-1 is a potent vasoconstrictor produced by the endothelial cells. Until now, there are no diagnostic tests for specific genetic risk factors to identify patients who are at a high risk of developing intracranial aneurysms. Knowledge of the genetic determinants may be useful in order to allow clues on stopping aneurysm formation and obtain diagnostic tools for identifying individuals at increased risk. Further multicenter studies have to be carried out.

The genetics of vascular complications in autosomal dominant polycystic kidney disease (ADPKD)

The most important extra-renal manifestation of autosomal dominant polycystic kidney disease (ADPKD) in terms of debilitating injury and premature death is the development of intracranial aneurysms (IAs) and other vascular complications, resulting in subarachnoid hemorrhage (SAH). IAs are found at a rate approximately five times higher in ADPKD patients than in the general population and in patients with a family history of SAH/IAs the frequency is elevated further three to five times, indicating the importance of genetic factors in its etiology. Expression of the ADPKD gene products, polycystin-1 (PKD1) and polycystin-2 (PKD2), in vascular smooth muscle and the endothelium, and evidence that reduced levels of these proteins leads to IA development in mouse models, suggests a direct role of these proteins in the vascular disease. PKD1 and PKD2 patients seem equally likely to develop IAs, while patients with mutations to the 5' half of PKD1 may more likely have vascular complications. Genome wide association and candidate studies of multiplex families with IAs without ADPKD have identified a number of genes/proteins that may be risk factors for the development of IAs. These candidate proteins largely have roles in the maintenance and remodeling of the arterial wall of small brain arteries. The development of the genetic methodologies of massively parallel sequencing mean it is now possible to test these and other candidates in ADPKD families with multiplex and singleton IA cases. Identifying strong modifiers of this phenotype will be important for prioritizing patients for presymptomatic screening and interventions.

Identification of novel mutations in Chinese Hans with autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited renal disease with an incidence of 1 in 400 to 1000. The disease is genetically heterogeneous, with two genes identified: PKD1 (16p13.3) and PKD2 (4q21). Molecular diagnosis of the disease in at-risk individuals is complicated due to the structural complexity of PKD1 gene and the high diversity of the mutations. This study is the first systematic ADPKD mutation analysis of both PKD1 and PKD2 genes in Chinese patients using denaturing high-performance liquid chromatography (DHPLC).

METHODS

Both PKD1 and PKD2 genes were mutation screened in each proband from 65 families using DHPLC followed by DNA sequencing. Novel variations found in the probands were checked in their family members available and 100 unrelated normal controls. Then the pathogenic potential of the variations of unknown significance was examined by evolutionary comparison, effects of amino acid substitutions on protein structure, and effects of splice site alterations using online mutation prediction resources.

RESULTS

A total of 92 variations were identified, including 27 reported previously. Definitely pathogenic mutations (ten frameshift, ten nonsense, two splicing defects and one duplication) were identified in 28 families, and probably pathogenic mutations were found in an additional six families, giving a total detection level of 52.3% (34/65). About 69% (20/29) of the mutations are first reported with a recurrent mutation rate of 31%.

CONCLUSIONS

Mutation study of PKD1 and PKD2 genes in Chinese Hans with ADPKD may contribute to a better understanding of the genetic diversity between different ethnic groups and enrich the mutation database. Besides, evaluating the pathogenic potential of novel variations should also facilitate the clinical diagnosis and genetic counseling of the disease.

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.

[Cystic and hyperechogenic kidneys in children]

Thanks to prenatal ultrasound scan, cystic kidneys, as well as obstructive uropathies, are the most frequent renal anomalies identified during pregnancy. They should be recognized because of genetic and clinical implications. The most frequent are autosomal dominant and recessive polycystic kidney diseases, followed by renal developmental anomalies linked to TCF2 gene. Renal cysts are also observed in other hereditary diseases or multiple malformation syndromes (tuberosis sclerosis, Meckel-Grubber syndrome, Oro-facial digital type 1 syndrome...). The diagnosis is based on a sonographic and morphological analysis of renal abnormalities, on the search for family histories and extra-renal manifestations. A better classification of these patients allows tailor-made follow-up and care improvement.

Molecular advances in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic disease (ADPKD) is the most common form of inherited kidney disease that results in renal failure. The understanding of the pathogenesis of ADPKD has advanced significantly since the discovery of the 2 causative genes, PKD1 and PKD2. Dominantly inherited gene mutations followed by somatic second-hit mutations inactivating the normal copy of the respective gene result in renal tubular cyst formation that deforms the kidney and eventually impairs its function. The respective gene products, polycystin-1 and polycystin-2, work together in a common cellular pathway. Polycystin-1, a large receptor molecule, forms a receptor-channel complex with polycystin-2, which is a cation channel belonging to the TRP family. Both polycystin proteins have been localized to the primary cilium, a nonmotile microtubule-based structure that extends from the apical membrane of tubular cells into the lumen. Here we discuss recent insights in the pathogenesis of ADPKD including the genetics of ADPKD, the properties of the respective polycystin proteins, the role of cilia, and some cell-signaling pathways that have been implicated in the pathways related to PKD1 and PKD2.

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

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease. The disease is caused by mutations of the PKD1 (affecting roughly 85% of ADPKD patients) and PKD2 (affecting roughly 14% of ADPKD patients) genes, although in several ADPKD families, the PKD1 and/or PKD2 linkage was not found. Mutation analysis of the PKD1 gene is complicated by the presence of highly homologous genomic duplications of the first two thirds of the gene.

METHODS

The direct detection of mutations in the non-duplicated region of the PKD1 gene was performed in 90 unrelated individuals, consisting of 58 patients with end-stage renal failure (manifesting before their 50th year of life) and 32 individuals from families where the disease was clearly linked to the PKD1 gene. Mutation screening was performed using denaturing gradient gel electrophoresis (DGGE). DNA fragments showing an aberrant electrophoretic banding pattern were sequenced.

RESULTS

In the non-duplicated region of the PKD1 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 PKD1 gene, 16 different polymorphisms or unclassified variants were detected.

CONCLUSION

Twenty probable mutations of the PKD1 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.

The Influence of G‐Protein β3‐Subunit Gene and Endothelial Nitric Oxide Synthase Gene in Exon 7 Polymorphisms on Progression of Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

A significant phenotypical variability is observed in autosomal dominant polycystic kidney disease (ADPKD). The variability cannot be fully explained by the genetic heterogeneity of the disease. We examined the influence of G-protein beta3-subunit C825T polymorphism and endothelial nitric oxide synthase Glu298Asp polymorphism on the progression of ADPKD towards end stage renal failure (ESRF).

METHODS

306 ADPKD patients (pts) were analyzed; 261 pts (136 males, 125 females) with ESRF, with subgroup of 73 pts (44 males, 29 females) with ESRF before 45 years (rapid progressors), 46 pts (20 males, 26 females) with ESRF later than in 63 years (slow progressors) and 45 ADPKD pts (17 males, 28 females) in mean age 51 years with serum creatinine under 110 micromol/L (slow progressors) and 100 genetically unrelated healthy Czech subjects. DNA samples from collected blood were genotyped for G-protein beta3-subunit C825T genotype in exon 10 and for endothelial nitric oxide synthase Glu298Asp genotype in exon 7.

RESULTS

The G-protein beta3-subunit C825T genotype exhibited no significant differences among the groups of slow progressors (6.6% (6/91) TT, 54.9% (50/91) CT, 38.8% (35/91) CC), rapid progressors (9.6% (7/73) TT, 46.6% (34/73) CT, 43.8% (32/73) CC), ADPKD group with ESRF between 40-63 years (9.2% (13/142) TT, 50% (71/142) CT, 40.8% (58/142) CC) and control group (12% TT, 44% CT, 44% CC). When comparing the ages of ESRF of all patients with ESRF, we did not find significant differences in the ages: males TT--51.7+/-8.8 years, CT--51.9+/-10.3 years, CC--49.7+/-10.2 years and females TT--56+/-9.9 years, CT--53.2+/-8.5 years, CC--53.9+/-8.7 years. The endothelial nitric oxide synthase Glu298Asp and Asp29Asp genotypes were significantly more frequent in rapid progressors (9.6% (7/73) Asp/Asp, 39.7% (29/73) Asp/Glu, 50.7% (37/73) Glu/Glu) and in ADPKD group with ESRF between 40-63 years (11.3% (16/142) Asp/Asp, 41.5% (59/142) Asp/Glu, 47.2% (67/142) Glu/Glu) in comparison with slow progressors (8.8% (8/91) Asp/Asp, 24.2% (22/91) Asp/Glu, 67.0% (61/91) Glu/Glu) and with control group (8% Asp/Asp, 32% Asp/Glu, 60% Glu/Glu) (Chi-square test, p<0.05). Comparing the ages of ESRF of all patients with ESRF, we did not find significant differences in the ages in males with Asp/Asp--54.9+/-10.4 years, Asp/Glu--50.2+/-9.4 years, Glu/Glu--51.0+/-10.4 years. We found out in homozygous Asp/Asp females significantly earlier onset of ESRF (49.2+/-5.6 years) in comparison with heterozygous females (53.3+/-7.2 years) and with Glu/Glu homozygous females (54.8+/-9.7 years) (t-test, p<0.05).

CONCLUSION

We excluded the significance of G-protein beta3-subunit C825T polymorphism on the progression of ADPKD. We established the negative prognostic value of the carriers of Asp variant of eNOS polymorphism. Finding of new modifiers could have in future clinical consequences for ADPKD patients.

Incompletely penetrant PKD1 alleles suggest a role for gene dosage in cyst initiation in polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) caused by mutations in PKD1 is significantly more severe than PKD2. Typically, ADPKD presents in adulthood but is rarely diagnosed in utero with enlarged, echogenic kidneys. Somatic mutations are thought crucial for cyst development, but gene dosage is also important since animal models with hypomorphic alleles develop cysts, but are viable as homozygotes. We screened for mutations in PKD1 and PKD2 in two consanguineous families and found PKD1 missense variants predicted to be pathogenic. In one family, two siblings homozygous for R3277C developed end stage renal disease at ages 75 and 62 years, while six heterozygotes had few cysts. In the other family, the father and two children with moderate to severe disease were homozygous for N3188S. In both families homozygous disease was associated with small cysts of relatively uniform size while marked cyst heterogeneity is typical of ADPKD. In another family, one patient diagnosed in childhood was found to be a compound heterozygote for the PKD1 variants R3105W and R2765C. All three families had evidence of developmental defects of the collecting system. Three additional ADPKD families with in utero onset had a truncating mutation in trans with either R3277C or R2765C. These cases suggest the presence of incompletely penetrant PKD1 alleles. The alleles alone may result in mild cystic disease; two such alleles cause typical to severe disease; and, in combination with an inactivating allele, are associated with early onset disease. Our study indicates that the dosage of functional PKD1 protein may be critical for cyst initiation.

Presence of de novo mutations in autosomal dominant polycystic kidney disease patients without family history

BACKGROUND

At the University of Colorado Health Sciences Center, on detailed questioning, approximately 10% of patients with autosomal dominant polycystic kidney disease (ADPKD) gave no family history of ADPKD. There are several explanations for this observation, including occurrence of a de novo pathogenic sequence variant or extreme phenotypic variability. To confirm de novo sequence variants, we have undertaken clinical and genetic screening of affected offspring and their parents.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

24 patients with a well-documented ADPKD phenotype and no family history of polycystic kidney disease (PKD) and both parents of each patient.

OUTCOME

Presence or absence of PKD1 or PKD2 pathogenic sequence variants in parents of affected offspring.

MEASUREMENTS

Abdominal ultrasound of affected offspring and their parents for ADPKD diagnosis. Parentage testing by genotyping. Complete screening of PKD1 and PKD2 genes by using genomic DNA from affected offspring; analysis of genomic DNA from both parents to confirm the absence or presence of all DNA variants found.

RESULTS

A positive diagnosis of ADPKD by means of ultrasound or genetic screening was made in 1 parent of 4 patients (17%). No PKD1 or PKD2 pathogenic sequence variants were identified in 10 patients (42%), whereas possible pathological DNA variants were identified in 4 patients (17%) and 1 of their respective parents. Parentage was confirmed in the remaining 6 patients (25%), and de novo sequence variants were documented.

LIMITATIONS

Size of patient group. No direct examination of RNA.

CONCLUSION

Causes other than de novo pathogenic sequence variants may explain the negative family history of ADPKD in certain families.

Molecular Genetics of Human Intracranial Aneurysms

Intracranial aneurysms (IAs) are the dilatations of blood vessels in the brain and pose potential risk of rupture leading to subarachnoid hemorrhage. Although the genetic basis of IAs is poorly understood, it is well-known that genetic factors play an important part in the pathogenesis of IAs. Therefore, the identifying susceptible genetic variants might lead to the understanding of the mechanism of formation and rupture of IAs and might also lead to the development of a pharmacological therapy. To elucidate the molecular pathogenesis of diseases has become a crucial step in the development of new treatment strategies. Although extensive genetic research and its potential implications for future prevention of this often fatal condition are urgently needed, efforts to elucidate the susceptibility loci of IAs are hindered by the issues bewildering the most common and complex genetic disorders, such as low penetrance, late onset, and uncertain modes of inheritance. These efforts are further complicated by the fact that many IA lesions remain asymptomatic or go undiagnosed. In this review, we present and discuss the current status of genetic studies of IAs and we recommend comprehensive genome-wide association studies to identify genetic loci that underlie this complex disease.

Advances in management of polycystic liver disease

The focus of this review is polycystic liver disease, a genetic disorder characterized by multiple macroscopic liver cysts that initially bud from biliary epithelium but subsequently lack communication with the biliary tree. There are two main clinical presentations: polycystic liver associated with autosomal dominant polycystic kidney disease and isolated polycystic liver disease. Both of these forms of polycystic liver disease exhibit an autosomal dominant pattern of inheritance. Clinical manifestations of polycystic liver disease are related to either mass effect of the volume of hepatic cysts or to complications arising within the cysts. Polycystic liver disease rarely progresses to hepatic failure or clinical complications of portal hypertension. Management is directed at counseling patients and families, treating complications and reducing cyst load by surgical techniques: cyst fenestration, hepatic resection or, rarely, hepatic transplantation. Recent research suggests that blockade of cyst secretion or inhibition of epithelial cells might be useful in halting progression of disease--these observations are discussed in this review.

Management of polycystic liver disease

The adult forms of polycystic liver disease are characterized by autosomal dominant inheritance and numerous hepatic cysts, with or without renal involvement. Mutations in two distinct genes predispose to renal and liver cysts (PKD1 and PKD2), and mutations in two different genes yield isolated liver cysts (PRKCSH and SEC63). Mutations at certain loci of PKD1 may predispose to more severe renal cystic disease or cerebral aneurysms. Risk factors for severe hepatic cystic disease include aging, female sex, pregnancy, use of exogenous female steroid hormones, degree of renal cystic disease, or severity of renal dysfunction (in patients with mutations in PKD1 or PKD2). Although liver failure or complications of advanced liver disease is rare, some patients develop massive hepatic cystic disease and become clinically symptomatic. There is no effective medical therapy. Treatment options include cyst aspiration and sclerosis, open or laparoscopic cyst fenestration, hepatic resection, and liver transplantation.

Evaluating the clinical utility of a molecular genetic test for polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is estimated to affect 1/600-1/1000 individuals worldwide. The disease is characterized by age dependent renal cyst formation that results in kidney failure during adulthood. Although ultrasound imaging may be an adequate diagnostic tool in at risk individuals older than 30, this modality may not be sufficiently sensitive in younger individuals or for those from PKD2 families who have milder disease. DNA based assays may be indicated in certain clinical situations where imaging cannot provide a definitive clinical diagnosis. The goal of this study was to evaluate the utility of direct DNA analysis in a test sample of 82 individuals who were judged to have polycystic kidney disease by standard clinical criteria. The samples were analyzed using a commercially available assay that employs sequencing of both genes responsible for the disorder. Definite disease causing mutations were identified in 34 (approximately 42%) study participants. An additional 30 (approximately 37%) subjects had either in frame insertions/deletions, non-canonical splice site alterations or a combination of missense changes that were also judged likely to be pathogenic. We noted striking sequence variability in the PKD1 gene, with a mean of 13.1 variants per participant (range 0-60). Our results and analysis highlight the complexity of assessing the pathogenicity of missense variants particularly when individuals have multiple amino acid substitutions. We conclude that a significant fraction of ADPKD mutations are caused by amino acid substitutions that need to be interpreted carefully when utilized in clinical decision-making.

Cardiovascular polycystins: insights from autosomal dominant polycystic kidney disease and transgenic animal models

Mutations in the PKD1 and PKD2 polycystin genes are responsible for autosomal dominant polycystic kidney disease (ADPKD), one of the most prevalent genetic kidney disorders. ADPKD is a multisystem disease characterized by the formation of numerous fluid-filled cysts in the kidneys, the pancreas, and the liver. Moreover, major cardiovascular manifestations are common complications in ADPKD. Intracranial aneurysms and arterial hypertension are among the leading causes of mortality in this disease. In the present review, we summarize our current understanding of the role of polycystins in the development, maintenance, and function of the cardiovascular system.

Genetics Of Intracranial Aneurysms

Despite advances in the treatment of intracranial aneurysms (IA) in recent years, the overall outcome of patients with aneurysmal subarachnoid hemorrhage has shown only modest improvement. Given this poor prognosis, diagnosis of IA before rupture is of paramount importance. Currently, there are no reliable methods other than screening imaging studies of high-risk individuals to diagnose asymptomatic patients. Multiple levels of evidence suggest that environmental factors acting in concert with genetic susceptibilities lead to the formation, growth, and rupture of aneurysms in these patients. Epidemiological studies have already identified aneurysm-specific risk factors such as size and location, as well as patient-specific risk factors, such as age, sex, and presence of medical comorbidities, such as hypertension. In addition, exposure to certain environmental factors such as smoking have been shown to be important in the formation of IA. Furthermore, substantial evidence proves that certain loci contribute genetically to IA pathogenesis. Genome-wide linkage studies using relative pairs or rare families that are affected with the Mendelian forms of IA have already shown genetic heterogeneity of IA, suggesting that multiple genes, alone or in combination, are important in the disease pathophysiology. The linkage results, along with association studies, will ultimately lead to the identification of IA susceptibility genes. Identification of the genes important in IA pathogenesis will not only provide novel insights into the primary determinants of IA, but will also result in new opportunities for early diagnosis in the preclinical setting. Ultimately, novel therapeutic strategies based on biology will be developed, which will target these newly elucidated genetic susceptibilities.

The genetics of intracranial aneurysms

The rupture of an intracranial aneurysm (IA) leads to a subarachnoid hemorrhage, a sudden onset disease that can lead to severe disability and death. Several risk factors such as smoking, hypertension and excessive alcohol intake are associated with subarachnoid hemorrhage. IAs, ruptured or unruptured, can be treated either surgically via a craniotomy (through an opening in the skull) or endovascularly by placing coils through a catheter in the femoral artery. Even though the etiology of IA formation is mostly unknown, several studies support a certain role of genetic factors. In reports so far, genome-wide linkage studies suggest several susceptibility loci that may contain one or more predisposing genes. Studies of several candidate genes report association with IAs. To date, no single gene has been identified as responsible for IA formation or rupture. The identification of susceptible genes may lead to the understanding of the mechanism of formation and rupture and possibly lead to the development of a pharmacological therapy.

Introduction: Non-atherosclerotic cerebrovascular disorders

Non-atherosclerotic cerebrovascular disorders are considered to occur less frequently than those caused by embolic or thrombotic disease. Such sporadic disorders resulting from direct effects on the cerebral or peripheral vasculature include hypertensive small vessel disease, vascular inflammatory conditions, aneurysms and arteriovenous malformations. Remarkably, some of these are also inherited in an autosomal dominant manner and appear to entail degeneration or abnormal differentiation of blood vessel wall elements such as smooth muscle, endothelial cells, pericytes and the perivascular nerve plexus. Two intensively investigated examples of these include the cerebral amyloid angiopathies and distinct primary arteriopathies such as CADASIL. The identification of novel genes associated with the hereditary forms of cerebrovascular disorders has been invaluable to understanding of the pathogenesis and management of sporadic disease.

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.

Autosomal-dominant polycystic kidney disease in infancy and childhood: progression and outcome

BACKGROUND

The natural history of autosomal-dominant polycystic kidney disease (ADPKD) has not been well described in children and infants.

METHODS

The present study analyzed the characteristics of 46 ADPKD children diagnosed before 18 months of life (VEO) and 153 children diagnosed between 18 months of age and 18 years of age (non-VEO).

RESULTS

VEO children had more cysts and larger renal volumes than non-VEO children when adjusted for age. In both VEO and non-VEO children, the presence of signs or symptoms at the time of diagnosis as well as the presence of hematuria or proteinuria at the study visit were associated with larger renal volumes. Children diagnosed early (VEO) or diagnosed due to signs or symptoms were also more likely to have high blood pressure. Two VEO children and no non-VEO children reached end-stage renal disease during follow-up.

CONCLUSION

In contrast to many published case reports suggesting the occurrence of early end-stage renal disease in VEO children, the results of the present study were much more optimistic. Over 90% of the VEO children maintained preserved renal function well into childhood.

Modifier genes play a significant role in the phenotypic expression of PKD111See Editorial by Pei, p. 1630

BACKGROUND

Polycystic kidney disease type 1 (PKD1) is characterized by extreme variation in the severity and progression of renal and extrarenal phenotypes. There are significant familial phenotype differences; but it is not clear if this is due to differences in PKD1 mutations, differences in genetic background, or both.

METHODS

A total of 315 affected relatives (83 PKD1 families) without end-stage renal disease (ESRD) were evaluated for disease markers, including renal volume, creatinine clearance, proteinuria, liver cysts, and hypertension. Of these patients, 19% progressed to ESRD within 1 to 10 years after the initial examination. Nested analysis of variance was used to investigate interfamilial and intrafamilial differences in these phenotypes. Heritability analyses were used to estimate the effect of the genetic background on phenotypic variability. The age of onset of ESRD was also analyzed with an additional 389 family members from the same PKD1 families without clinical evaluation but with data on age of onset of ESRD (or age without ESRD).

RESULTS

There were significant phenotype differences between patients with the same mutation and different genetic backgrounds. The phenotypic variation between patients with different mutations and different genetic backgrounds was not significantly greater than the variation between patients with the same mutation and different genetic backgrounds. However, when the 389 family members were included, both the mutation and modifier genes had significant effects on the age of onset of ESRD. Inherited differences in genetic background were estimated to account for 18% to 59% of the phenotypic variability in PKD1 disease markers in patients prior to ESRD and in the subsequent progression to ESRD (43% heritability) in the 315 patients who were clinically evaluated.

CONCLUSION

Modifier loci in the genetic background are important factors in inter- and intrafamilial variability in the phenotypic expression of PKD1. The extreme intrafamilial phenotype differences are consistent with the hypothesis that one or a few modifier genes have a major effect on the progression and severity of PKD1.

Mutation analysis of autosomal dominant polycystic kidney disease genes in Han Chinese

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in two genes, PKD1 and PKD2. The complexity of these genes, particularly PKD1, has complicated genetic screening, though recent advances have provided new opportunities for amplifying these genes. In the Han Chinese population, no complete mutational analysis has previously been conducted across the entire span of PKD1 and PKD2. Here, we used single-strand conformation polymorphism (SSCP) analysis to screen the entire coding sequence of PKD1 and PKD2 in 85 healthy controls and 72 Han Chinese from 24 ADPKD pedigrees. In addition to 11 normal variants, we identified 17 mutations (12 in PKD1 and 5 in PKD2), 15 of which were novel ones (11 for PKD1 and 4 for PKD2). We did not identify any seeming mutational hot spots in PKD1 and PKD2. Notably, we found several disease-associated C-T or G-A mutations that led to charge or hydrophobicity changes in the corresponding amino acids. This suggests that the mutations cause conformational alterations in the PKD1 and PKD2 protein products that may impact the normal protein functions. Our study is the first report of screenable mutations in the full-length PKD1 and PKD2 genes of the Han Chinese, and also offers a benchmark for comparisons between Caucasian and Han ADPKD pedigrees and patients.

Polycystic disease of the liver

Autosomal dominant polycystic disease is genetically heterogeneous with mutations in two distinct genes predisposing to the combination of renal and liver cysts (AD-PKD1 and AD-PKD2) and mutations in a third gene yielding isolated liver cysts (the polycystic liver disease gene). Transcription and translation of the PKD1 gene produces polycystin-1, an integral membrane protein that may serve as an extracellular receptor. Mutations occur throughout the PKD1 gene, but more severe disease is associated with N-terminal mutations. The PKD2 gene product, polycystin-2, is an integral membrane protein with molecular characteristics of a calcium-permeant cation channel. Mutations occur throughout the PKD2 gene, and severity of disease may vary with site of mutation in PKD2 and the functional consequence on the resultant polycystin-2 protein. Polycystic liver disease is genetically linked to protein kinase C substrate 80K-H (PRKCSH). The PRKCSH gene encodes hepatocystin, a protein that moderates glycosylation and fibroblast growth factor receptor signaling. More prominent in women, hepatic cysts emerge after the onset of puberty and dramatically increase in number and size through the child-bearing years of early and middle adult life. Although liver failure or complications of advanced liver disease are rare, some patients develop massive hepatic cystic disease and become clinically symptomatic. There is no effective medical therapy. Interventional and surgical options include cyst aspiration and sclerosis, open or laparoscopic cyst fenestration, hepatic resection, and liver transplantation.

Polycystic disease of the liver

Autosomal dominant polycystic disease is genetically heterogeneous with mutations in two distinct genes predisposing to the combination of renal and liver cysts (AD-PKD1 and AD-PKD2) and mutations in a third gene yielding isolated liver cysts (the polycystic liver disease gene). Transcription and translation of the PKD1 gene produces polycystin-1, an integral membrane protein that may serve as an extracellular receptor. Mutations occur throughout the PKD1 gene, but more severe disease is associated with N-terminal mutations. The PKD2 gene product, polycystin-2, is an integral membrane protein with molecular characteristics of a calcium-permeant cation channel. Mutations occur throughout the PKD2 gene, and severity of disease may vary with site of mutation in PKD2 and the functional consequence on the resultant polycystin-2 protein. Polycystic liver disease is genetically linked to protein kinase C substrate 80K-H (PRKCSH). The PRKCSH gene encodes hepatocystin, a protein that moderates glycosylation and fibroblast growth factor receptor signaling. More prominent in women, hepatic cysts emerge after the onset of puberty and dramatically increase in number and size through the child-bearing years of early and middle adult life. Although liver failure or complications of advanced liver disease are rare, some patients develop massive hepatic cystic disease and become clinically symptomatic. There is no effective medical therapy. Interventional and surgical options include cyst aspiration and sclerosis, open or laparoscopic cyst fenestration, hepatic resection, and liver transplantation.

Genome-wide linkage in a large Dutch consanguineous family maps a locus for intracranial aneurysms to chromosome 2p13

BACKGROUND AND PURPOSE

Familial occurrence of intracranial aneurysms suggests a genetic factor in the development of these aneurysms. In this study, we present the identification of a susceptibility locus for the development of intracranial aneurysms detected by a genome-wide linkage approach in a large consanguineous pedigree.

METHODS

Patients with clinical signs and symptoms of intracranial aneurysms, confirmed by radiological, surgical, or postmortem investigations, were included in the study. Magnetic resonance angiography was used to detect asymptomatic aneurysms in relatives.

RESULTS

Seven out of 20 siblings had an intracranial aneurysm. Genome-wide multipoint linkage analysis showed a significant logarithm of the odds score of 3.55.

CONCLUSIONS

In a large consanguineous pedigree intracranial aneurysms are linked to chromosome 2p13 in a region between markers D2S2206 and D2S2977.

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

Background

We have previously developed a long RT-PCR method for selective amplification of full-length PKD1 transcripts (13.6 kb) and a long-range PCR for amplification in the reiterated region (18 kb) covering exons 14 and 34 of the PKD1 gene. These have provided us with an opportunity to study PKD1 mutations especially in its reiterated region which is difficult to examine. In this report, we have further developed the method of multiple restriction fragment-single strand conformation polymorphism (MRF-SSCP) for analysis of PKD1 mutations in the patients with autosomal dominant polycystic kidney disease (ADPKD). Novel and de novo PKD1 mutations are identified and reported.

Methods

Full-length PKD1 cDNA isolated from the patients with ADPKD was fractionated into nine overlapping segments by nested-PCR. Each segment was digested with sets of combined restriction endonucleases before the SSCP analysis. The fragments with aberrant migration were mapped, isolated, and sequenced. The presence of mutation was confirmed by the long-range genomic DNA amplification in the PKD1 region, sequencing, direct mutation detection, and segregation analysis in the affected family.

Results

Five PKD1 mutations identified are two frameshift mutations caused by two di-nucleotide (c. 5225_5226delAG and c.9451_9452delAT) deletions, a nonsense (Q1828X, c.5693C>T) mutation, a splicing defect attributable to 31 nucleotide deletion (g.33184_33214del31), and an in-frame deletion (L3287del, c.10070_10072delCTC). All mutations occurred within the reiterated region of the gene involving exons 15, 26, 15, 19 and 29, respectively. Three mutations (one frameshift, splicing defect, and in-frame deletion) are novel and two (one frameshift and nonsense) known. In addition, two mutations (nonsense and splicing defect) are possibly de novo.

Conclusion

The MRF-SSCP method has been developed to analyze PCR products generated by the long RT-PCR and nested-PCR technique for screening PKD1 mutations in the full-length cDNA. Five mutations identified were all in the reiterated region of this gene, three of which were novel. The presence of de novo PKD1 mutations indicates that this gene is prone to mutations.

Influence of the alpha-adducin and ACE gene polymorphism on the progression of autosomal-dominant polycystic kidney disease

BACKGROUND

A significant phenotypical variability is observed in autosomal dominant polycystic kidney disease (ADPKD). The variability can not be fully explained by the genetic heterogeneity of the disease. We examined the influence of the ACE I/D polymorphism, adducin Trp460Gly polymorphism and the association of both polymorphisms on the progression of ADPKD towards end-stage renal failure (ESRF).

METHODS

320 ADPKD patients (pts) were analyzed, 220 pts (113 males, 107 females) with ESRF before 63 years of age, with a subgroup (rapid progressors) of 20 pts (12 males, 8 females) with ESRF before 40 years of age, 52 pts (23 males, 29 females) with ESRF later than 63 years of age (slow progressors), 48 ADPKD pts (18 males, 30 females) with mean age +/-50 years with serum creatinine <110 micromol/l (slow progressors) and 200 genetically unrelated healthy Czech subjects. DNA samples from collected blood were genotyped for the ACE I/D polymorphism and the Trp460Gly of alpha-adducin gene polymorphism.

RESULTS

The alpha-adducin genotypes showed no differences among the groups of slow progressors (74% Gly/Gly, 22.9% Gly/Trp and 3.1% Trp/Trp), pts with ESRF before 63 years of age (67.7% Gly/Gly, 30.5% Gly/Trp and 1.8% Trp/Trp) and rapid progressors (75% Gly/Gly, 25% Gly/Trp). The ACE genotypes did not differ among the groups of slow progressors (27.1% I/I, 44.8% I/D and 28.1% D/D), pts with ESRF before 63 years of age (23.6% I/I, 51.4% I/D and 25% D/D) and rapid progressors (20% I/I, 55% I/D and 25% D/D). The distribution did not differ from the control group. The ages of ESRF according to different genotypes did not significantly differ. We observed a significant tendency to better prognosis in Trp allele carriers for I/I genotype in comparison with Gly/Gly homozygous subjects.

CONCLUSION

The ACE and alpha-adducin polymorphisms do not play a significant role in the progression of ADPKD to ESRF.

Familial association of basilar bifurcation aneurysm and moyamoya disease--four case reports

Four patients presented with familial intracranial aneurysms and familial moyamoya disease, including one patient with both familial intracranial aneurysm and moyamoya disease. Basilar bifurcation aneurysms were present in two patients, moyamoya disease in one, and both basilar bifurcation aneurysm and moyamoya disease in one. These events are most likely to arise from different genetic abnormalities associated with basilar bifurcation aneurysm and moyamoya disease.

Association of mutation position in polycystic kidney disease 1 (PKD1) gene and development of a vascular phenotype

BACKGROUND

Patients with autosomal dominant polycystic kidney disease (ADPKD) are at risk of developing intracranial aneurysms, and subarachnoid haemorrhage is a major cause of death and disability. Familial clustering of intracranial aneurysms suggests that genetic factors are important in the aetiology. We tested whether the germline mutation predisposes to this vascular phenotype.

METHODS

DNA samples from patients with ADPKD and vascular complications were screened for mutations throughout the PKD1 and PKD2 genes. Comparisons were made between the PKD1 and PKD2 populations and with a control PKD1 cohort (without the vascular phenotype).

FINDINGS

Mutations were characterised in 58 ADPKD families with vascular complications; 51 were PKD1 (88%) and seven PKD2 (12%). The median position of the PKD1 mutation was significantly further 59 in the vascular population than in the 87 control pedigrees (aminoacid position 2163 vs 2773, p=0.0034). Subsets of the vascular population with aneurysmal rupture, early rupture, or families with more than one vascular case had median mutation locations further 59 (aminoacid position 1811, p=0.0018; 1671, p=0.0052; and 1587, p=0.0003).

INTERPRETATION

Patients with PKD2, as well as those with PKD1, are at risk of intracranial aneurysm. The position of the mutation in PKD1 is predictive for development of intracranial aneurysms (59 mutations are more commonly associated with vascular disease) and is therefore of prognostic importance. Since the PKD1 phenotype is associated with mutation position, the disease is not simply due to loss of all disease allele products.

Ultrastructural connective tissue aberrations in patients with intracranial aneurysms

BACKGROUND AND PURPOSE

An unknown connective tissue defect might predispose for the development and rupture of intracranial aneurysms in some patients. This study of connective tissue samples of a series of patients with intracranial aneurysms investigates the morphology of the extracellular matrix with methods that are currently used in the routine diagnosis of inherited connective tissue disorders.

METHODS

Skin biopsies from 21 patients with intracranial aneurysms, many with multiple aneurysms, were studied by electron microscopy. None of the patients included in this study showed clinical signs of a known connective tissue disorder.

RESULTS

In 7 patients (33%), we observed repetitive aberrations in the morphology of collagen fibrils and elastic fibers of the reticular dermis. The observed ultrastructural findings were somewhat similar to those typically observed in patients with Ehlers-Danlos syndrome (EDS) and in a subgroup of patients with spontaneous cervical artery dissections. The patterns of abnormalities fell into 2 classes: 4 patients displayed abnormalities that resembled those found in patients with EDS type III, and the electron microscopic findings in the skin biopsies from 3 patients resembled those of EDS type IV patients. The sequence of the COL3A1 gene from the patients with EDS type IV-like alterations of the connective tissue morphology was analyzed. No mutation was detected.

CONCLUSIONS

Connective tissue alterations were found in skin biopsies from a minority of patients with intracranial aneurysms. Electron microscopic investigation of skin biopsies from patients and their relatives might become valuable for clinical diagnostics, identification of persons at risk, and basic studies of the pathogenesis of this vascular disease.

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.

A complete mutation screen of the ADPKD genes by DHPLC

BACKGROUND

Genetic analysis is a useful diagnostic tool in autosomal dominant polycystic kidney disease (ADPKD), especially when imaging results are equivocal. However, molecular diagnostics by direct mutation screening has proved difficult in this disorder due to genetic and allelic heterogeneity and complexity of the major locus, PKD1.

METHODS

A protocol was developed to specifically amplify the exons of PKD1 and PKD2 from genomic DNA as 150 to 450 bp amplicons. These fragments were analyzed by the technique of denaturing high-performance liquid chromatography (DHPLC) using a Wave Fragment Analysis System (Transgenomics) to detect base-pair changes throughout both genes. DHPLC-detected changes were characterized by sequencing.

RESULTS

Cost effective and sensitive mutation screening of the entire coding regions of PKD1 and PKD2 by DHPLC was optimized. All base-pair mutations to these genes that we previously characterized were detected as an altered DHPLC profile. To assess this method for routine diagnostic use, samples from a cohort of 45 genetically uncharacterized ADPKD patients were analyzed. Twenty-nine definite mutations were detected, 26 PKD1, 3 PKD2 and a further five possible missense mutations were characterized leading to a maximal detection rate of 76%. A high level of polymorphism of PKD1 also was detected, with 71 different changes defined. The reproducibility of the DHPLC profile enabled the recognition of many common polymorphisms without the necessity for re-sequencing.

CONCLUSIONS

DHPLC has been demonstrated to be an efficient and effective means for gene-based molecular diagnosis of ADPKD. Differentiating missense mutations and polymorphisms remains a challenge, but family-based segregation analysis is helpful.

The position of the polycystic kidney disease 1 (PKD1) gene mutation correlates with the severity of renal disease

The severity of renal cystic disease in the major form of autosomal dominant polycystic kidney disease (PKD1) is highly variable. Clinical data was analyzed from 324 mutation-characterized PKD1 patients (80 families) to document factors associated with the renal outcome. The mean age to end-stage renal disease (ESRD) was 54 yr, with no significant difference between men and women and no association with the angiotensin-converting enzyme polymorphism. Considerable intrafamilial variability was observed, reflecting the influences of genetic modifiers and environmental factors. However, significant differences in outcome were also found among families, with rare examples of unusually late-onset PKD1. Possible phenotype/genotype correlations were evaluated by estimating the effects of covariants on the time to ESRD using proportional hazards models. In the total population, the location of the mutation (in relation to the median position; nucleotide 7812), but not the type, was associated with the age at onset of ESRD. Patients with mutations in the 5' region had significantly more severe disease than the 3' group; median time to ESRD was 53 and 56 yr, respectively (P = 0.025), with less than half the chance of adequate renal function at 60 yr (18.9% and 39.7%, respectively). This study has shown that the position of the PKD1 mutation is significantly associated with earlier ESRD and questions whether PKD1 mutations simply inactivate all products of the gene.