Regional localization of the autosomal dominant polycystic kidney disease locus

The localization of the autosomal dominant polycystic kidney disease locus (PKD1) within an array of anonymous polymorphic DNA sequences on chromosome 16 band p13 was determined by multipoint mapping. Nine polymorphic DNA markers, including two hypervariable sequences, were used to study 19 PKD1 and 21 reference families. PKD1 was found to lie proximal to the 3' and 5' hypervariable regions of alpha-globin and distal to the anonymous sequence CRI-0327. Somatic cell hybrid mapping places PKD1 within the region 16p13.11-16pter. The availability of an array of linked markers which bracket the PKD1 locus provides a framework for further attempts to identify the PKD1 gene and offers an improved method of presymptomatic diagnosis of the disease.     

Feline polycystic kidney disease is linked to the PKD1 region

Autosomal dominant polycystic kidney disease (ADPKD) is a commonly inherited disorder (1/1000) in humans characterized by fluid-filled cysts in the kidneys. Defects in the PKD genes, PKD1 and PKD2, cause 85% and 15% of human ADPKD cases, respectively. Mutations in the PKHD1 gene cause autosomal recessive PKD (ARPKD). Mutations in several genes, including Nek8, cause PKD in mice. Although PKD affects 38% of Persian cats worldwide, making it the most prominent inherited feline disease, a causative gene has not been identified. Feline PKD is an autosomal dominant disease with clinical presentations similar to human ADPKD. Forty-three microsatellites were chosen from the feline genetic maps based on known homology with human chromosomal regions containing the PKD1, PKD2, PKHD1, and Nek8 genes. Linkage analysis using seven Persian cat pedigrees segregating for PKD has shown significant linkage and no recombinants (Z=5.83, =0) between the PKD disease phenotype and marker FCA476, which is within 10 cR of the feline PKD1 gene on Chromosome E3. This suggests that the PKD1 gene or another gene within this region may cause feline PKD. Further investigation into the cause of PKD will be valuable for feline health and provide insights into human ADPKD.     

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

The gene for the most common form of autosomal dominant polycystic kidney disease (ADPKD), PKD1, has recently been characterized and shown to encode an integral membrane protein, polycystin-1, which is involved in cell-cell and cell-matrix interactions. Until now, approximately 30 mutations of the 3' single copy region of the PKD1 gene have been reported in European and American populations. However, there is no report of mutations in Asian populations. Using the polymerase chain reaction and single-strand conformation polymorphism (SSCP) analysis, 91 Korean patients with ADPKD were screened for mutation in the 3' single copy region of the PKD1 gene. As a result, we have identified and characterized six mutations: three frameshift mutations (11548del8bp, 11674insG and 12722delT), a nonsense mutation (Q4010X), and two missense mutations (R3752W and D3814N). Five mutations except for Q4010X are reported here for the first time. Our findings also indicate that many different mutations are likely to be responsible for ADPKD in the Korean population. The detection of additional disease-causing PKD1 mutations will help in identifying the location of the important functional regions of polycystin-1 and help us to better understand the pathophysiology of ADPKD.     

Epigenetics and autosomal dominant polycystic kidney disease

The roles of epigenetic modulation of gene expression and protein functions in autosomal dominant polycystic kidney disease (ADPKD) have recently become the focus of scientific investigation. Evidence generated to date indicates that one of the epigenetic modifiers, histone deacetylases (HDACs), are important regulators of ADPKD. HDACs are involved in regulating the expression of the Pkd1 gene and are the target of fluid flow-induced calcium signal in kidney epithelial cells. Pharmacological inhibition of HDAC activity has been found to reduce the progression of cyst formation and slow the decline of kidney function in Pkd1 conditional knockout mice and Pkd2 knockout mice, respectively, implicating the potential clinical application of HDAC inhibitors on ADPKD. Since the expression of HDAC6 is upregulated in cystic epithelial cells, the potential roles of HDAC6 in regulating cilia resorption and epidermal growth factor receptor (EGFR) trafficking through deacetylating α-tubulin and regulating Wnt signaling through deacetylating β-catenin are also discussed. This article is part of a Special Issue entitled: Polycystic Kidney Disease.     

Probe,VK5B,is located in the same interval as the autosomal dominant adult polycystic kidney disease locus,PKD1

Summary The polymorphic DNA probe VK5B (D16S94) was mapped by genetic linkage in families from the Centre d'Etude de Polymorphisme Humain (CEPH) as being in the same interval as the autosomal dominant adult polycystic kidney disease locus (PKD1). The maximum likelihood estimate of the genetic location of VK5B using multipoint linkage analysis was 9.6cM proximal to {ie286-01} (D16S85) and 5.4cM distal to CRI-0327 (D16S63), in males. The VK5B probe may be useful in PKD1 families for prenatal and presymptomatic diagnosis of the disease. Additional typing of PKD1 families is required to determine whether the location of VK5B is distal or proximal to (PKD1).     

TRPP2 and autosomal dominant polycystic kidney disease

Mutations in TRPP2 (polycystin-2) cause autosomal dominant polycystic kidney disease (ADPKD), a common genetic disorder characterized by progressive development of fluid-filled cysts in the kidney and other organs. TRPP2 is a Ca(2+)-permeable nonselective cation channel that displays an amazing functional versatility at the cellular level. It has been implicated in the regulation of diverse physiological functions including mechanosensation, cell proliferation, polarity, and apoptosis. TRPP2 localizes to different subcellular compartments, such as the endoplasmic reticulum (ER), the plasma membrane and the primary cilium. The channel appears to have distinct functions in different subcellular compartments. This functional compartmentalization is thought to contribute to the observed versatility and specificity of TRPP2-mediated Ca(2+) signaling. In the primary cilium, TRPP2 has been suggested to function as a mechanosensitive channel that detects fluid flow in the renal tubule lumen, supporting the proposed role of the primary cilium as the unifying pathogenic concept for cystic kidney disease. This review summarizes the known and emerging functions of TRPP2, focusing on the question of how channel function translates into complex morphogenetic programs regulating tubular structure.     

Autosomal recessive polycystic kidney disease does not map to the second gene locus for autosomal dominant polycystic kidney disease on chromosome 4

Linkage analysis in 19 families with autosomal recessive polycystic kidney disease (ARPKD) has shown that ARPKD is not linked to the recently assigned second gene locus for autosomal dominant polycystic kidney disease (ADPKD) on chromosome 4q (PKD2). Thus, there is strong evidence that ADPKD and ARPKD have different gene loci.     

Molecular pathogenesis of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is one of the commonest inherited human disorders yet remains relatively unknown to the wider medical, scientific and public audience. ADPKD is characterised by the development of bilateral enlarged kidneys containing multiple fluid-filled cysts and is a leading cause of end-stage renal failure (ESRF). ADPKD is caused by mutations in two genes: PKD1 and PKD2. The protein products of the PKD genes, polycystin-1 and polycystin-2, form a calcium-regulated, calcium-permeable ion channel. The polycystin complex is implicated in regulation of the cell cycle via multiple signal transduction pathways as well as the mechanosensory function of the renal primary cilium, an enigmatic cellular organelle whose role in normal physiology is still poorly understood. Defects in cilial function are now documented in several other human diseases including autosomal recessive polycystic kidney disease, nephronophthisis, Bardet-Biedl syndrome and many animal models of polycystic kidney disease. Therapeutic trials in these animal models of polycystic kidney disease have identified several promising drugs that ameliorate disease severity. However, elucidation of the function of the polycystins and the primary cilium will have a major impact on our understanding of renal cystic diseases and will create exciting new opportunities for the design of disease-specific therapies.     

Novel stop and frameshifting mutations in the autosomal dominant polycystic kidney disease 2 (PKD2) gene

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most frequent inherited disorders. The majority of cases are due to mutation of the PKD1 gene, on 16p13.3, while in most of the remainder the disease maps to the PKD2 locus, at chromosome 4q21-q23. Recently, the PKD2 gene has been positionally cloned and three nonsense mutations within the coding sequence of the gene identified. Here we report a systematic mutation screening of all 15 exons of the PKD2 gene in chromosome 4-linked ADPKD families, using heteroduplex and SSCP analyses. We have identified and characterized seven novel mutations, with a detection rate of approximately 90% in the population studied. All of the mutations result in the premature stop of translation: four nonsense changes and three deletions. The deletions are all frameshifting, of four T nucleotides in one case and one G nucleotide in the other two. All mutations are unique and are distributed throughout the gene without evidence of clustering. Comparison of specific mutations with the clinical profile in ADPKD2 families shows no clear correlation. Received: 5 April 1997 / Accepted: 31 July 1997     

Bilineal disease and trans-heterozygotes in autosomal dominant polycystic kidney disease

In searching for a putative third gene for autosomal dominant polycystic kidney disease (ADPKD), we studied the genetic inheritance of a large family (NFL10) previously excluded from linkage to both the PKD1 locus and the PKD2 locus. We screened 48 members of the NFL10 pedigree, by ultrasonography, and genotyped them, with informative markers, at both the PKD1 locus and the PKD2 locus. Twenty-eight of 48 individuals assessed were affected with ADPKD. Inspection of the haplotypes of these individuals suggested the possibility of bilineal disease from independently segregating PKD1 and PKD2 mutations. Using single-stranded conformational analysis, we screened for and found a PKD2 mutation (i.e., 2152delA; L736X) in 12 affected pedigree members. Additionally, when the disease status of these individuals was coded as "unknown" in linkage analysis, we also found, with markers at the PKD1 locus, significant LOD scores (i.e., >3.0). These findings strongly support the presence of a PKD1 mutation in 15 other affected pedigree members, who lack the PKD2 mutation. Two additional affected individuals had trans-heterozygous mutations involving both genes, and they had renal disease that was more severe than that in affected individuals who had either mutation alone. This is the first documentation of bilineal disease in ADPKD. In humans, trans-heterozygous mutations involving both PKD1 and PKD2 are not necessarily embryonically lethal. However, the disease associated with the presence of both mutations appears to be more severe than the disease associated with either mutation alone. The presence of bilineal disease as a confounder needs to be considered seriously in the search for the elusive PKD3 locus.     

Renal concentrating capacity is linked to blood pressure in children with autosomal dominant polycystic kidney disease

Impaired glomerular filtration rate (GFR) is a risk factor for the development of hypertension in patients with autosomal dominant polycystic kidney disease (ADPKD). However, markers of tubular function were not tested whether they are linked to hypertension or blood pressure (BP) level. The aim of our study was to investigate the relationship between renal concentrating capacity and BP in children with ADPKD. Fifty-three children (mean age 11.8+/-4.4 years) were investigated. Standardized renal concentrating capacity test was performed after nasal drop application of desmopressin, BP was measured by ambulatory BP monitoring (ABPM). Renal concentrating capacity was decreased in 58 % of children. The prevalence of hypertension was significantly higher in children with decreased renal concentrating capacity (35 %) than in children with normal renal concentrating capacity (5 %) (p<0.05). Significant negative correlations were found between renal concentrating capacity, ambulatory BP and number of renal cysts (r = -0.29 to -0.39, p<0.05 to p<0.01). In conclusion, the concentrating capacity is decreased in about half of the patients and is linked to BP. Decreased renal concentrating capacity should be considered.     

Refining the localization of the PKD2 locus on chromosome 4q by linkage analysis in Spanish families with autosomal dominant polycystic kidney disease type 2.

Autosomal dominant polycystic kidney disease (ADPKD) is a genetically heterogeneous disorder. At least two distinct forms of ADPKD are now well defined. In approximately 86% of affected European families, a gene defect localized to 16p13.3 was responsible for ADPKD, while a second locus has been recently localized to 4q13-q23 as candidate for the disease in the remaining families. We present confirmation of linkage to microsatellite markers on chromosome 4q in eight Spanish families with ADPKD, in which the disease was not linked to 16p13.3. By linkage analysis with marker D4S423, a maximum lod score of 9.03 at a recombination fraction of .00 was obtained. Multipoint linkage analysis, as well as a study of recombinant haplotypes, placed the PKD2 locus between D4S1542 and D4S1563, thereby defining a genetic interval of approximately 1 cM. The refined map will serve as a genetic framework for additional genetic and physical mapping of the region and will improve the accuracy of presymptomatic diagnosis of PKD2.     

A long-range restriction map between the alpha-globin complex and a marker closely linked to the polycystic kidney disease 1 (PKD1) locus

Two polymorphic loci and two additional probes that map close to CMM65, which is tightly linked to the polycystic kidney disease 1 (PKD1) locus in chromosome band 16p13.3, are described. These new probes were isolated from a library that was enriched by preparative pulsed-field gel electrophoresis (PFGE) for sequences from a 320-kb NotI fragment that includes CMM65. Through the use of a panel of somatic cell hybrids and PFGE, the new polymorphic loci, PNL56S and NKISP1, were localized within 60 kb and approximately 250 kb distal to CMM65, respectively. A long-range restriction map linking these new probes and the distal markers EKMDA2, CMM103, and alpha-globin was constructed. These latter probes have been localized to regions approximately 900 kb, 1.2 Mb, and 1.9 Mb distal to CMM65, respectively. The entire region was found to be unusually rich in CpG dinucleotides. The new polymorphic probes and the long-range map will aid both the search for the PKD1 locus and the detailed characterization of this distal region of 16p.     

A spectrum of mutations in the second gene for autosomal dominant polycystic kidney disease (PKD2).

Recently the second gene for autosomal dominant polycystic kidney disease (ADPKD), located on chromosome 4q21-q22, has been cloned and characterized. The gene encodes an integral membrane protein, polycystin-2, that shows amino acid similarity to the PKD1 gene product and to the family of voltage-activated calcium (and sodium) channels. We have systematically screened the gene for mutations by single-strand conformation-polymorphism analysis in 35 families with the second type of ADPKD and have identified 20 mutations. So far, most mutations found seem to be unique and occur throughout the gene, without any evidence of clustering. In addition to small deletions, insertions, and substitutions leading to premature translation stops, one amino acid substitution and five possible splice-site mutations have been found. These findings suggest that the first step toward cyst formation in PKD2 patients is the loss of one functional copy of polycystin-2.     

Urine proteome of autosomal dominant polycystic kidney disease patients

Background

Autosomal dominant polycystic kidney disease (ADPKD) is responsible for 10% of cases of the end stage renal disease. Early diagnosis, especially of potential fast progressors would be of benefit for efficient planning of therapy. Urine excreted proteome has become a promising field of the search for marker patterns of renal diseases including ADPKD. Up to now however, only the low molecular weight fraction of ADPKD proteomic fingerprint was studied. The aim of our study was to characterize the higher molecular weight fraction of urinary proteome of ADPKD population in comparison to healthy controls as a part of a general effort aiming at exhaustive characterization of human urine proteome in health and disease, preceding establishment of clinically useful disease marker panel.

Results

We have analyzed the protein composition of urine retentate (>10 kDa cutoff) from 30 ADPKD patients and an appropriate healthy control group by means of a gel-free relative quantitation of a set of more than 1400 proteins. We have identified an ADPKD-characteristic footprint of 155 proteins significantly up- or downrepresented in the urine of ADPKD patients. We have found changes in proteins of complement system, apolipoproteins, serpins, several growth factors in addition to known collagens and extracellular matrix components. For a subset of these proteins we have confirmed the results using an alternative analytical technique.

Conclusions

Obtained results provide basis for further characterization of pathomechanism underlying the observed differences and establishing the proteomic prognostic marker panel.     

Fine genetic localization of the gene for autosomal dominant polycystic kidney disease (PKD1) with respect to physically mapped markers.

PKD1, the gene for the chromosome 16-linked form of autosomal dominant polycystic kidney disease, has previously been genetically mapped to an interval bounded by the polymorphic loci Fr3-42/EKMDA2 distally and O327hb/O90a proximally. More recently, 26.6PROX was identified as the closest proximal flanking locus. We set out to refine the localization of PKD1 by identifying a series of single recombinant events between the flanking markers Fr3-42/EKMDA2 and O327hb/O90a and analyzing them with a new set of polymorphic loci that have been physically mapped within the PKD1 interval. We identified 11 such crossovers in eight families; 6 of these fell into the interval between GGG1 and 26.6PROX, a distance of less than 750 kb. Three of these crossovers placed PKD1 proximal to GGG1 and two crossovers placed PKD1 distal to 26.6PROX. Both of the latter also placed PKD1 telomeric to a locus 92.6SH1.0, which lies 200-250 kb distal to 26.6PROX. The sixth recombinant, however, placed the disease mutation proximal to the locus 92.6SH1.0. Several possible explanations for these observations are discussed. An intensive study to locate deletions, insertions, and other chromosomal rearrangements associated with PKD1 mutations failed to detect any such abnormalities. Thus we have defined, in genetic and physical terms, the segment of 16p13.3 where PKD1 resides and conclude that a gene-by-gene analysis of the region will be necessary to identify the mutation(s).     

DNA microsatellite analysis in families with autosomal dominant polycystic kidney disease (ADPKD): the first Polish study

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited renal disorders with genetic heterogeneity. Mutations of two known genes are responsible for this disease: PKD1 at 16p13.3 and PKD2 at 4q21-23. A majority of cases (85%) are caused by mutations in PKD1. Because direct mutation screening remains complex, we describe here the application of an efficient approach to studies based on highly informative dinucleotide and tetranucleotide repeats flanking genes PKD1 and PKD2. METHODS: For this study a series of microsatellites closely linked to locus PKD1 (D16S291, D16S663, D16S665, D16S283, D16S407, D16S475) and to locus PKD2 (D4S1563, D4S2929, D4S414, D4S1534, D4S423) were selected. Short (81-242 bp) DNA fragments containing the tandem repeats were amplified by polymerase chain reaction (PCR). The number of repeat units of microsatelite markers was determined by fluorescent capillary electrophoresis. RESULTS: DNA microsatellite analysis was performed in 25 Polish ADPKD families and established the type of disease (21 families PKD1-type, 1 family PKD2-type). CONCLUSIONS: While a disease-causing mutation in the PKD1 and PKD2 genes cannot be identified, DNA microsatellite analysis provided an early diagnosis and may be considered in ADPKD families.