Polycystin-2 Mediated Calcium Signalling in the Dictyostelium Model for Autosomal Dominant Polycystic Kidney Disease.

Autosomal dominant polycystic kidney disease (ADPKD) occurs when the proteins Polycystin-1 (PC1, PKD1) and Polycystin-2 (PC2, PKD2) contain mutations. PC1 is a large membrane receptor that can interact and form a complex with the calcium-permeable cation channel PC2. This complex localizes to the plasma membrane, primary cilia and ER. Dysregulated calcium signalling and consequential alterations in downstream signalling pathways in ADPKD are linked to cyst formation and expansion; however, it is not completely understood how PC1 and PC2 regulate calcium signalling. We have studied Polycystin-2 mediated calcium signalling in the model organism Dictyostelium discoideum by overexpressing and knocking down the expression of the endogenous Polycystin-2 homologue, Polycystin-2. Chemoattractant-stimulated cytosolic calcium response magnitudes increased and decreased in overexpression and knockdown strains, respectively, and analysis of the response kinetics indicates that Polycystin-2 is a significant contributor to the control of Ca2+ responses. Furthermore, basal cytosolic calcium levels were reduced in Polycystin-2 knockdown transformants. These alterations in Ca2+ signalling also impacted other downstream Ca2+-sensitive processes including growth rates, endocytosis, stalk cell differentiation and spore viability, indicating that Dictyostelium is a useful model to study Polycystin-2 mediated calcium signalling.

A de novo PKD1 mutation in a Chinese family with autosomal dominant polycystic kidney disease.

BACKGROUND: PKD1, which has a relatively high mutation rate, is highly polymorphic, and the role of PKD1 is incompletely defined. In the current study, in order to determine the molecular etiology of a family with autosomal dominant polycystic kidney disease, the pathogenicity of an frameshift mutation in the PKD1 gene, c.9484delC, was evaluated. METHODS: The family clinical data were collected. Whole exome sequencing analysis determined the level of this mutation in the proband's PKD1, and Sanger sequencing and bioinformatics analysis were performed. SIFT, Polyphen2, and MutationTaster were used to evaluate the conservation of the gene and pathogenicity of the identified mutations. SWISS-MODEL was used to predict and map the protein structure of PKD1 and mutant neonate proteins. RESULTS: A novel c.9484delC (p.Arg3162Alafs*154) mutation of the PKD1 gene was identified by whole exome sequencing in the proband, which was confirmed by Sanger sequencing in his sister (II7). The same mutation was not detected in the healthy pedigree members. Random screening of 100 normal and end-stage renal disease patients did not identify the c.9484delC mutation. Bioinformatics analysis suggested that the mutation caused the 3162 nd amino acid substitution of arginine by alanine and a shift in the termination codon. As a result, the protein sequence was shortened from 4302 amino acids to 3314 amino acids, the protein structure was greatly changed, and the PLAT/LH2 domain was destroyed. Clustal analysis indicated that the altered amino acids were highly conserved in mammals. CONCLUSION: A novel mutation in the PKD1 gene has been identified in an affected Chinese family. The mutation is probably responsible for a range of clinical manifestations for which reliable prenatal diagnosis and genetic counseling may be provided.

The Link between Autosomal Dominant Polycystic Kidney Disease and Chromosomal Instability: Exploring the Relationship.

In autosomal dominant polycystic kidney disease (ADPKD) with germline mutations in a PKD1 or PKD2 gene, innumerable cysts develop from tubules, and renal function deteriorates. Second-hit somatic mutations and renal tubular epithelial (RTE) cell death are crucial features of cyst initiation and disease progression. Here, we use established RTE lines and primary ADPKD cells with disease-associated PKD1 mutations to investigate genomic instability and DNA damage responses. We found that ADPKD cells suffer severe chromosome breakage, aneuploidy, heightened susceptibility to DNA damage, and delayed checkpoint activation. Immunohistochemical analyses of human kidneys corroborated observations in cultured cells. DNA damage sensors (ATM/ATR) were activated but did not localize at nuclear sites of damaged DNA and did not properly activate downstream transducers (CHK1/CHK2). ADPKD cells also had the ability to transform, as they achieved high saturation density and formed colonies in soft agar. Our studies indicate that defective DNA damage repair pathways and the somatic mutagenesis they cause contribute fundamentally to the pathogenesis of ADPKD. Acquired mutations may alternatively confer proliferative advantages to the clonally expanded cell populations or lead to apoptosis. Further understanding of the molecular details of aberrant DNA damage responses in ADPKD is ongoing and holds promise for targeted therapies.

Leucine-Rich Repeat in Polycystin-1 Suppresses Cystogenesis in a Zebrafish (Danio rerio) Model of Autosomal-Dominant Polycystic Kidney Disease.

Mutations of PKD1 coding for polycystin-1 (PC1) account for most cases of autosomal-dominant polycystic kidney disease (ADPKD). The extracellular region of PC1 contains many evolutionarily conserved domains for ligand interactions. Among these are the leucine-rich repeats (LRRs) in the far N-terminus of PC1. Using zebrafish (Danio rerio) as an in vivo model system, we explored the role of LRRs in the function of PC1. Zebrafish expresses two human PKD1 paralogs, pkd1a and pkd1b. Knockdown of both genes in zebrafish by morpholino antisense oligonucleotides produced phenotypes of dorsal-axis curvature and pronephric cyst formation. We found that overexpression of LRRs suppressed both phenotypes in pkd1-morphant zebrafish. Purified recombinant LRR domain inhibited proliferation of HEK cells in culture and interacted with the heterotrimeric basement membrane protein laminin-511 (α5ß1γ1) in vitro. Mutations of amino acid residues in LRRs structurally predicted to bind laminin-511 disrupted LRR-laminin interaction in vitro and neutralized the ability of LRRs to inhibit cell proliferation and cystogenesis. Our data support the hypothesis that the extracellular region of PC1 plays a role in modulating PC1 interaction with the extracellular matrix and contributes to cystogenesis of PC1 deficiency.

Interleukin-37: a new therapeutic target in autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) has long been considered a genetic renal disorder, but emerging evidence suggests that the immune microenvironment within the kidney plays a pivotal role in disease progression and severity. In recent years, the previously obscure cytokine interleukin-37 has proved a strong inhibitor of innate immunity in multiple disease models. However, its role in ADPKD has not received scrutiny. In a provocative study published in the current issue, Zylberberg et al. show that interleukin-37 activates interferon signaling in renal macrophages, which inhibits ADPKD initiation. This finding identifies interleukin-37 as a potential viable immunomodulatory therapy for ADPKD.

Molecular and structural basis of the dual regulation of the polycystin-2 ion channel by small-molecule ligands.

Mutations in the PKD2 gene, which encodes the polycystin-2 (PC2, also called TRPP2) protein, lead to autosomal dominant polycystic kidney disease (ADPKD). As a member of the transient receptor potential (TRP) channel superfamily, PC2 functions as a non-selective cation channel. The activation and regulation of the PC2 channel are largely unknown, and direct binding of small-molecule ligands to this channel has not been reported. In this work, we found that most known small-molecule agonists of the mucolipin TRP (TRPML) channels inhibit the activity of the PC2_F604P, a gain-of-function mutant of the PC2 channel. However, two of them, ML-SA1 and SF-51, have dual regulatory effects, with low concentration further activating PC2_F604P, and high concentration leading to inactivation of the channel. With two cryo-electron microscopy (cryo-EM) structures, a molecular docking model, and mutagenesis results, we identified two distinct binding sites of ML-SA1 in PC2_F604P that are responsible for activation and inactivation, respectively. These results provide structural and functional insights into how ligands regulate PC2 channel function through unusual mechanisms and may help design compounds that are more efficient and specific in regulating the PC2 channel and potentially also for ADPKD treatment.

Global analysis of urinary extracellular vesicle small RNAs in autosomal dominant polycystic kidney disease.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is the most prevalent monogenic renal disease progressing to end-stage renal disease. There is a pressing need for the identification of early ADPKD biomarkers to enable timely intervention and the development of effective therapeutic approaches. Here, we profiled human urinary extracellular vesicles small RNAs by small RNA sequencing in patients with ADPKD and compared their differential expression considering healthy control individuals to identify dysregulated small RNAs and analyze downstream interaction to gain insight about molecular pathophysiology. METHODS: This is a cross-sectional study where urine samples were collected from a total of 23 PKD1-ADPKD patients and 28 healthy individuals. Urinary extracellular vesicles were purified, and small RNA was isolated and sequenced. Differentially expressed Small RNA were identified and functional enrichment analysis of the critical miRNAs was performed to identify driver genes and affected pathways. RESULTS: miR-320b, miR-320c, miR-146a-5p, miR-199b-3p, miR-671-5p, miR-1246, miR-8485, miR-3656, has_piR_020497, has_piR_020496 and has_piR_016271 were significantly upregulated in ADPKD patient urine extracellular vesicles and miRNA-29c was significantly downregulated. Five 'driver' target genes (FBRS, EDC3, FMNL3, CTNNBIP1 and KMT2A) were identified. CONCLUSIONS: The findings of the present study make significant contributions to the understanding of ADPKD pathogenesis and to the identification of novel biomarkers and potential drug targets aimed at slowing disease progression in ADPKD.

cGAS Activation Accelerates the Progression of Autosomal Dominant Polycystic Kidney Disease.

SIGNIFICANCE STATEMENT: The renal immune infiltrate observed in autosomal polycystic kidney disease contributes to the evolution of the disease. Elucidating the cellular mechanisms underlying the inflammatory response could help devise new therapeutic strategies. Here, we provide evidence for a mechanistic link between the deficiency polycystin-1 and mitochondrial homeostasis and the activation of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)/stimulator of the interferon genes (STING) pathway. Our data identify cGAS as an important mediator of renal cystogenesis and suggest that its inhibition may be useful to slow down the disease progression. BACKGROUND: Immune cells significantly contribute to the progression of autosomal dominant polycystic kidney disease (ADPKD), the most common genetic disorder of the kidney caused by the dysregulation of the Pkd1 or Pkd2 genes. However, the mechanisms triggering the immune cells recruitment and activation are undefined. METHODS: Immortalized murine collecting duct cell lines were used to dissect the molecular mechanism of cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) activation in the context of genotoxic stress induced by Pkd1 ablation. We used conditional Pkd1 and knockout cGas-/- genetic mouse models to confirm the role of cGAS/stimulator of the interferon genes (STING) pathway activation on the course of renal cystogenesis. RESULTS: We show that Pkd1 -deficient renal tubular cells express high levels of cGAS, the main cellular sensor of cytosolic nucleic acid and a potent stimulator of proinflammatory cytokines. Loss of Pkd1 directly affects cGAS expression and nuclear translocation, as well as activation of the cGAS/STING pathway, which is reversed by cGAS knockdown or functional pharmacological inhibition. These events are tightly linked to the loss of mitochondrial structure integrity and genotoxic stress caused by Pkd1 depletion because they can be reverted by the potent antioxidant mitoquinone or by the re-expression of the polycystin-1 carboxyl terminal tail. The genetic inactivation of cGAS in a rapidly progressing ADPKD mouse model significantly reduces cystogenesis and preserves normal organ function. CONCLUSIONS: Our findings indicate that the activation of the cGAS/STING pathway contributes to ADPKD cystogenesis through the control of the immune response associated with the loss of Pkd1 and suggest that targeting this pathway may slow disease progression.

Pkd2 Deficiency in Embryonic Aqp2 + Progenitor Cells Is Sufficient to Cause Severe Polycystic Kidney Disease.

SIGNIFICANCE STATEMENT: Autosomal dominant polycystic kidney disease (ADPKD) is a devastating disorder caused by mutations in polycystin 1 ( PKD1 ) and polycystin 2 ( PKD2 ). Currently, the mechanism for renal cyst formation remains unclear. Here, we provide convincing and conclusive data in mice demonstrating that Pkd2 deletion in embryonic Aqp2 + progenitor cells (AP), but not in neonate or adult Aqp2 + cells, is sufficient to cause severe polycystic kidney disease (PKD) with progressive loss of intercalated cells and complete elimination of α -intercalated cells, accurately recapitulating a newly identified cellular phenotype of patients with ADPKD. Hence, Pkd2 is a new potential regulator critical for balanced AP differentiation into, proliferation, and/or maintenance of various cell types, particularly α -intercalated cells. The Pkd2 conditional knockout mice developed in this study are valuable tools for further studies on collecting duct development and early steps in cyst formation. The finding that Pkd2 loss triggers the loss of intercalated cells is a suitable topic for further mechanistic studies. BACKGROUND: Most cases of autosomal dominant polycystic kidney disease (ADPKD) are caused by mutations in PKD1 or PKD2. Currently, the mechanism for renal cyst formation remains unclear. Aqp2 + progenitor cells (AP) (re)generate ≥5 cell types, including principal cells and intercalated cells in the late distal convoluted tubules (DCT2), connecting tubules, and collecting ducts. METHODS: Here, we tested whether Pkd2 deletion in AP and their derivatives at different developmental stages is sufficient to induce PKD. Aqp2Cre Pkd2f/f ( Pkd2AC ) mice were generated to disrupt Pkd2 in embryonic AP. Aqp2ECE/+Pkd2f/f ( Pkd2ECE ) mice were tamoxifen-inducted at P1 or P60 to inactivate Pkd2 in neonate or adult AP and their derivatives, respectively. All induced mice were sacrificed at P300. Immunofluorescence staining was performed to categorize and quantify cyst-lining cell types. Four other PKD mouse models and patients with ADPKD were similarly analyzed. RESULTS: Pkd2 was highly expressed in all connecting tubules/collecting duct cell types and weakly in all other tubular segments. Pkd2AC mice had obvious cysts by P6 and developed severe PKD and died by P17. The kidneys had reduced intercalated cells and increased transitional cells. Transitional cells were negative for principal cell and intercalated cell markers examined. A complete loss of α -intercalated cells occurred by P12. Cysts extended from the distal renal segments to DCT1 and possibly to the loop of Henle, but not to the proximal tubules. The induced Pkd2ECE mice developed mild PKD. Cystic α -intercalated cells were found in the other PKD models. AQP2 + cells were found in cysts of only 13/27 ADPKD samples, which had the same cellular phenotype as Pkd2AC mice. CONCLUSIONS: Hence, Pkd2 deletion in embryonic AP, but unlikely in neonate or adult Aqp2 + cells (principal cells and AP), was sufficient to cause severe PKD with progressive elimination of α -intercalated cells, recapitulating a newly identified cellular phenotype of patients with ADPKD. We proposed that Pkd2 is critical for balanced AP differentiation into, proliferation, and/or maintenance of cystic intercalated cells, particularly α -intercalated cells.

A synthetic agent ameliorates polycystic kidney disease by promoting apoptosis of cystic cells through increased oxidative stress.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic cause of chronic kidney disease and the fourth leading cause of end-stage kidney disease, accounting for over 50% of prevalent cases requiring renal replacement therapy. There is a pressing need for improved therapy for ADPKD. Recent insights into the pathophysiology of ADPKD revealed that cyst cells undergo metabolic changes that up-regulate aerobic glycolysis in lieu of mitochondrial respiration for energy production, a process that ostensibly fuels their increased proliferation. The present work leverages this metabolic disruption as a way to selectively target cyst cells for apoptosis. This small-molecule therapeutic strategy utilizes 11beta-dichloro, a repurposed DNA-damaging anti-tumor agent that induces apoptosis by exacerbating mitochondrial oxidative stress. Here, we demonstrate that 11beta-dichloro is effective in delaying cyst growth and its associated inflammatory and fibrotic events, thus preserving kidney function in perinatal and adult mouse models of ADPKD. In both models, the cyst cells with homozygous inactivation of Pkd1 show enhanced oxidative stress following treatment with 11beta-dichloro and undergo apoptosis. Co-administration of the antioxidant vitamin E negated the therapeutic benefit of 11beta-dichloro in vivo, supporting the conclusion that oxidative stress is a key component of the mechanism of action. As a preclinical development primer, we also synthesized and tested an 11beta-dichloro derivative that cannot directly alkylate DNA, while retaining pro-oxidant features. This derivative nonetheless maintains excellent anti-cystic properties in vivo and emerges as the lead candidate for development.

Novel hits for autosomal dominated polycystic kidney disease (ADPKD) targeting derived by in silico screening on ZINC-15 natural product database.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disorder that leads to growth cysts in the kidney, ultimately resulting in loss of function. Currently, no effective drug therapy can be safely used in the clinic. So, looking for effective therapeutic drugs is urgent for treating ADPKD. Our natural product library was prepared based on the ZINC-15 database. Lipinski's rule of five, drug-likeness, and toxicity screening of the designed library were evaluated. Swiss model online server was used for modeling of GANAB target. Finally, docking-based screening against ADPKD targets was done by MOE 2019 software. The top 14 favorable druglike and non-toxic hits were selected for docking studies. Our results showed that compound-10 (ZINC 6073947) as a sesquiterpene coumarin had more negative binding interaction into the active site of PPARG, OXSR1, GANAB, AVPR2, and PC2 with docking scores of -8.22, -7.52, -6.98, -6.61 and -6.05 kcal/mol, respectively, in comparison to Curcumin, as a natural product that is now in phase 4 clinical trial in ADPKD disease, with an affinity of -8.03, -6.42, -6.82, -5.84 and -5.10 kcal/mol, respectively. Furthermore, seven sesquiterpene coumarins similar to compound 10 were generated and docked. Farnesiferol B (16), compared to compound-10, showed binding affinity of -8.16, -6.4, -7.46, -6.92, and -6.11 kcal/mol against the above targets, respectively. Molecular dynamics, which was done on the compound-10 and 16 (Farnesiferol B) in complex with PPARG, GANAB, and AVPR2, showed more negative binding free-energy than Pioglitazone, Miglitol, and Tolvaptan as FDA-approved drugs for each target, respectively.Communicated by Ramaswamy H. Sarma.

Molecular diagnostic results of a nephropathy gene panel in patients with suspected hereditary kidney disease.

OBJECTIVE: Clinical diagnosis of hereditary kidney disease can be difficult because of its rarity and severe phenotypic variability. Identifying mutated causative genes can provide diagnostic and prognostic information. In this study, we report the clinical application and outcome of a next-generation sequencing-based, targeted multi-gene panel test for the genetic diagnosis of patients with hereditary kidney disease. METHODS: A total of 145 patients evaluated for hereditary kidney disease who underwent a nephropathy panel with 44 different genes were retrospectively reviewed and included in the study. RESULTS: Genetic diagnosis of other hereditary kidney diseases, particularly autosomal dominant polycystic kidney disease, was made in 48% of patients. The nephropathy panel changed the preliminary diagnosis in 6% of patients. The variants in 18 (12%) patients had not been previously reported in the literature. CONCLUSION: This study demonstrates the utility of the nephropathy panel in identifying patients diagnosed with hereditary kidney disease who are referred for genetic testing. A contribution was made to the variant spectrum of genes associated with hereditary kidney disease.

The VUS Challenge in Cystic Kidney Disease: A Case-Based Review.

Genetic testing in nephrology is becoming increasingly important to diagnose patients and to provide appropriate care. This is especially true for autosomal dominant polycystic kidney disease (ADPKD) because this is a common cause of kidney failure and genetically complex. In addition to the major genes, PKD1 and PKD2 , there are at least six minor loci, and phenotypic, and in some cases, genetic overlap with other cystic disorders. Targeted next-generation sequencing, a low-cost, high-throughput technique, has made routine genetic testing viable in nephrology clinics. Appropriate pre- and post-testing genetic counseling is essential to the testing process. Carefully assessing variants is also critical, with the genetic report classifying variants in accordance with American College of Medical Genetics and Genomics guidelines. However, variant of uncertain significance (VUSs) may pose a significant challenge for the ordering clinician. In ADPKD, and particularly within PKD1 , there is high allelic heterogeneity; no single variant is present in more than 2% of families. The Mayo/Polycystic Kidney Disease Foundation variant database, a research tool, is the best current database of PKD1 and PKD2 variants containing over 2300 variants identified in individuals with polycystic kidney disease, but novel variants are often identified. In patients with a high pretest probability of ADPKD on the basis of clinical criteria, but no finding of a pathogenic (P) or likely pathogenic (LP) variant in a cystic kidney gene, additional evaluation of cystic gene VUS can be helpful. In this case-based review, we propose an algorithm for the assessment of such variants in a clinical setting and show how some can be reassigned to a diagnostic grouping. When assessing the relevance of a VUS, we consider both patient/family-specific and allele-related factors using population and variant databases and available prediction tools, as well as genetic expertise. This analysis plus further family studies can aid in making a genetic diagnosis.

Prenatal diagnosis of polycystic kidney caused by biallelic hypomorphic variants in the PKD1 gene.

Heterozygous loss-of-function variants in the PKD1 gene are commonly associated with adult-onset autosomal dominant polycystic kidney disease (ADPKD), where the formation of renal cysts depends on the dosage of the PKD1 gene. Biallelic null PKD1 variants are not viable, but biallelic hypomorphic variants could lead to early-onset PKD. We report a non-consanguineous Chinese family with recurrent fetal polycystic kidney and negative findings in the coding region of the PKHD1 gene or chromosomal microarray analysis. Trio exome analysis revealed compound heterozygous variants of uncertain significance in the PKD1 gene in the index pregnancy: a novel paternally inherited c.7863 + 5G > C and a maternally inherited c.9739C > T, p.(Arg3247Cys). Segregation analysis through long-range PCR followed by nested PCR and Sanger sequencing confirmed another affected fetus had both variants, while the other two normal siblings and the parents carried either variant. Thus, these two variants, both of which were hypomorphic as opposed to null variants, co-segregated with prenatal onset polycystic kidney disease in this family. Functional studies are needed to further determine the impact of these two variants. Our findings highlight the biallelic inheritance of hypomorphic PKD1 variants causing prenatal onset polycystic kidney disease, which provides a better understanding of phenotype-genotype correlation and valuable information for reproductive counseling.

Matrix Metalloproteinase-7 in Urinary Extracellular Vesicles Identifies Rapid Disease Progression in Autosomal Dominant Polycystic Kidney Disease.

SIGNIFICANCE STATEMENT: There is an unmet need for biomarkers of disease progression in autosomal dominant polycystic kidney disease (ADPKD). This study investigated urinary extracellular vesicles (uEVs) as a source of such biomarkers. Proteomic analysis of uEVs identified matrix metalloproteinase 7 (MMP-7) as a biomarker predictive of rapid disease progression. In validation studies, MMP-7 was predictive in uEVs but not in whole urine, possibly because uEVs are primarily secreted by tubular epithelial cells. Indeed, single-nucleus RNA sequencing showed that MMP-7 was especially increased in proximal tubule and thick ascending limb cells, which were further characterized by a profibrotic phenotype. Together, these data suggest that MMP-7 is a biologically plausible and promising uEV biomarker for rapid disease progression in ADPKD. BACKGROUND: In ADPKD, there is an unmet need for early markers of rapid disease progression to facilitate counseling and selection for kidney-protective therapy. Our aim was to identify markers for rapid disease progression in uEVs. METHODS: Six paired case-control groups ( n =10-59/group) of cases with rapid disease progression and controls with stable disease were formed from two independent ADPKD cohorts, with matching by age, sex, total kidney volume, and genetic variant. Candidate uEV biomarkers were identified by mass spectrometry and further analyzed using immunoblotting and an ELISA. Single-nucleus RNA sequencing of healthy and ADPKD tissue was used to identify the cellular origin of the uEV biomarker. RESULTS: In the discovery proteomics experiments, the protein abundance of MMP-7 was significantly higher in uEVs of patients with rapid disease progression compared with stable disease. In the validation groups, a significant >2-fold increase in uEV-MMP-7 in patients with rapid disease progression was confirmed using immunoblotting. By contrast, no significant difference in MMP-7 was found in whole urine using ELISA. Compared with healthy kidney tissue, ADPKD tissue had significantly higher MMP-7 expression in proximal tubule and thick ascending limb cells with a profibrotic phenotype. CONCLUSIONS: Among patients with ADPKD, rapid disease progressors have higher uEV-associated MMP-7. Our findings also suggest that MMP-7 is a biologically plausible biomarker for more rapid disease progression.

Molecular genetic diagnosis of kidney ciliopathies: Lessons from interpreting genomic sequencing data and the requirement for accurate phenotypic data.

INTRODUCTION: Massively parallel sequencing (MPS) techniques have made a major impact on the identification of the genetic basis of inherited kidney diseases such as the ciliopathy autosomal dominant polycystic kidney disease (ADPKD). Great care must be taken when analysing MPS data in isolation from accurate phenotypic information, as this can cause misdiagnosis. METHODS: Here, we describe a family trio, recruited to the Genomics England 100,000 Genomes Project, labelled as having cystic kidney disease, who were genetically unsolved following routine data analysis pipelines. We performed a bespoke reanalysis of Whole Genome Sequencing (WGS) data and coupled this with revised phenotypic data and targeted PCR and Sanger sequencing to provide a precise molecular genetic diagnosis. RESULTS: We detected a heterozygous PKD1 frameshift variant within the WGS data which segregated with the redefined ADPKD phenotypes. An additional heterozygous exon deletion in ALG8 was also found in affected and unaffected individuals, but its precise clinical significance remains unclear. CONCLUSION: This case illustrates that reanalysis of WGS data in unsolved cases of cystic kidney disease is valuable. Clinical phenotypes must be reassessed as these may have been incorrectly recorded and evolve over time. Undertaking additional studies including genotype-phenotype correlation in wider family members provides useful diagnostic information.

Modulating inflammation with interleukin 37 treatment ameliorates murine Autosomal Dominant Polycystic Kidney Disease.

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a leading cause of kidney failure and is associated with substantial morbidity and mortality. Interstitial inflammation is attributed to the action of infiltrating macrophages and is a feature thought to aggravate disease progression. Here, we investigated the therapeutic potential of the anti-inflammatory IL37b cytokine as a treatment for ADPKD using genetic mouse models, demonstrating that transgenic expression of human IL37b reduced collecting duct cyst burden in both early and adult-onset ADPKD rodent models. Moreover, injection of recombinant human IL37b could also reduce cyst burden in early onset ADPKD mice, an observation not associated with increased macrophage number at early stages of cyst formation. Interestingly, transgenic IL37b expression also did not alter macrophage numbers in advanced disease. Whole kidney RNA-seq highlighted an IL37b-mediated upregulation of the interferon signaling pathway and single-cell RNA-seq established that these changes originate at least partly from kidney resident macrophages. We further found that blocking type I interferon signaling in mice expressing IL37b resulted in increased cyst number, confirming this as an important pathway by which IL37b exerts its beneficial effects. Thus, our studies show that IL37b promotes interferon signaling in kidney resident macrophages which suppresses cyst initiation, identifying this protein as a potential therapy for ADPKD.

Cardiovascular Involvement in Patients with Autosomal Dominant Polycystic Kidney Disease: A Review.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease with a prevalence of 1:400 to 1:1,000 in Caucasians. It is caused by mutations in the PKD1 gene located on chromosome 16p13.3 (in about 85% cases) as well as in the PKD2 gene on chromosome 4q13-23. In the Polish population, the disease is associated with PKD1 mutations in 84% of the ADPKD-affected families. PKD1 and PKD2 genes encode the proteins polycystin-1 (PC1) and polycystin-2 (PC2), respectively. The presence of kidney cysts is a characteristic feature in the ADPKD patients. But in the ADPKD patients, cardiovascular abnormalities, such as hypertension (HT) with higher systolic blood pressure (SBP) and diastolic blood pressure (DBP) values, higher left ventricular mass (LVM), intracranial (ICAN) and extracranial aneurysms, and cardiac valve defects, are significantly more common than in the general population. SUMMARY: According to the literature data, both higher LVM and vascular dysfunction already occur in children and young adults with normal renal function and without HT. Moreover, biventricular diastolic dysfunction, endothelial dysfunction, increased carotid intima-media thickness, and impaired coronary flow velocity reserve are present even in young patients with ADPKD who have normal HT and well-preserved renal function. In patients with ADPKD, hypertension has some specific features; in the youngest age group of children, the prevalence of hypertension is greater if their parents suffer from hypertension; in normotensive young ADPKD-diagnosed individuals, ambulant SBP and DBP values were significantly higher than in age- and gender-matched controls; hypertension appears at least 10 years earlier than spontaneous HT in general population. In adults, HT is often diagnosed before any substantial reduction in the GFR, and a lower nocturnal dip in BP in comparison to hypertensives in the general population. PKD1 and PKD2 gene products (PC1 and PC2 proteins) have been shown to assemble at the plasma membrane and to regulate calcium (Ca2+) entry. A defect in Ca2+ binding mediated by mutations in polycystin proteins is a hypothetical factor contributing to left ventricular mass increase. Altered intracellular Ca2+ handling contributes importantly to impaired contractility associated with heart failure. Impairment of intracellular Ca2+ homeostasis and mitochondrial function has been implicated in the development of LVH. KEY MESSAGES: It can be assumed that the cause of LVH in ADPKD patients is the natural course of this disease with developing HT and deteriorating kidney function, which may be influenced by the presence of PKD1- and PKD2-mutated gene products: PC1 and PC2 proteins.

Genetic Spectrum of Polycystic Kidney and Liver Diseases and the Resulting Phenotypes.

Polycystic kidney diseases are a group of monogenically inherited disorders characterized by cyst development in the kidney with defects in primary cilia function central to pathogenesis. Autosomal dominant polycystic kidney disease (ADPKD) has progressive cystogenesis and accounts for 5-10% of kidney failure (KF) patients. There are two major ADPKD genes, PKD1 and PKD2, and seven minor loci. PKD1 accounts for ∼80% of patients and is associated with the most severe disease (KF is typically at 55-65 years); PKD2 accounts for ∼15% of families, with KF typically in the mid-70s. The minor genes are generally associated with milder kidney disease, but for DNAJB11 and ALG5, the age at KF is similar to PKD2. PKD1 and PKD2 have a high level of allelic heterogeneity, with no single pathogenic variant accounting for >2% of patients. Additional genetic complexity includes biallelic disease, sometimes causing very early-onset ADPKD, and mosaicism. Autosomal dominant polycystic liver disease is characterized by severe PLD but limited PKD. The two major genes are PRKCSH and SEC63, while GANAB, ALG8, and PKHD1 can present as ADPKD or autosomal dominant polycystic liver disease. Autosomal recessive polycystic kidney disease typically has an infantile onset, with PKHD1 being the major locus and DZIP1L and CYS1 being minor genes. In addition, there are a range of mainly recessive syndromic ciliopathies with PKD as part of the phenotype. Because of the phenotypic and genic overlap between the diseases, employing a next-generation sequencing panel containing all known PKD and ciliopathy genes is recommended for clinical testing.

Clinical findings, underlying pathogenetic processes and treatment of vascular dysfunction in autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited disorder characterized by the development of fluid-filled cysts in the kidneys. The primary cause of ADPKD is mutations in the PKD1 (polycystic kidney disease 1) or PKD2 (polycystic kidney disease 2) gene. Patients with ADPKD often develop a variety of vascular abnormalities, which have a major impact on the structure and function of the blood vessels and can lead to complications such as hypertension, intracranial aneurysm (ICAN), and atherosclerosis. The progression of ADPKD involves intricate molecular and cellular processes that lead to the development of these vascular abnormalities. Our understanding of these processes remains incomplete, and available treatment options are limited. The aim of this review is to delve into the underlying mechanisms of these vascular abnormalities and to explore potential interventions.