Autosomal Dominant Polycystic Kidney Disease Research Articles

Safety and efficacy of transcatheter arterial embolization in autosomal dominant polycystic kidney patients with gross hematuria: Six case reports

BACKGROUND To retrospectively report the safety and efficacy of renal transcatheter arterial embolization for treating autosomal dominant polycystic kidney disease (ADPKD) patients with gross hematuria. CASE SUMMARY The purpose of this study is to retrospectively report the safety and efficacy of renal transcatheter arterial embolization for treating ADPKD patients with gross hematuria. Materials and methods: During the period from January 2018 to December 2019, renal transcatheter arterial embolization was carried out on 6 patients with polycystic kidneys and gross hematuria. Renal arteriography was performed first, and then we determined the location of the hemorrhage and performed embolization under digital subtraction angiography monitoring. Improvements in routine blood test results, routine urine test results, urine color and postoperative reactions were observed and analyzed. Results: Renal transcatheter arterial embolization was successfully conducted in 6 patients. The indices of 5 patients and the color of gross hematuria improved after surgery compared with before surgery. No severe complication reactions occurred. CONCLUSION For autosomal dominant polycystic kidney syndrome patients with gross hematuria, transcatheter arterial embolization was safe and effective.

Renal Pathology of Ciliopathies.

Renal ciliopathies are a group of genetic disorders that affect the function of the primary cilium in the kidney, as well as other organs. Since primary cilia are important for regulation of cell signaling pathways, ciliary dysfunction results in a range of clinical manifestations, including renal failure, cyst formation, and hypertension. We summarize the current understanding of the pathophysiological and pathological features of renal ciliopathies in childhood, including autosomal dominant and recessive polycystic kidney disease, nephronophthisis, and Bardet-Biedl syndrome, as well as skeletal dysplasia associated renal ciliopathies. The genetic basis of these disorders is now well-established in many cases, with mutations in a large number of cilia-related genes such as PKD1, PKD2, BBS, MKS, and NPHP being responsible for the majority of cases. Renal ciliopathies are broadly characterized by development of interstitial fibrosis and formation of multiple renal cysts which gradually enlarge and replace normal renal tissue, with each condition demonstrating subtle differences in the degree, location, and age-related development of cysts and fibrosis. Presentation varies from prenatal diagnosis of congenital multisystem syndromes to an asymptomatic childhood with development of complications in later adulthood and therefore clinicopathological correlation is important, including increasing use of targeted genetic testing or whole genome sequencing, allowing greater understanding of genetic pathophysiological mechanisms.

Exploring Adiponectin in Autosomal Dominant Kidney Disease: Insight and Implications

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a common monogenic disorder characterized by renal cysts and progressive renal failure. In kidney diseases, adipose tissue undergoes functional changes that have been associated with increased inflammation and insulin resistance mediated by release of adipokines. Adiponectin is involved in various cellular processes, such as energy and inflammatory and oxidative processes. However, it remains to be determined whether adiponectin is involved in the concomitant metabolic dysfunctions present in PKD. In this scenario, we aimed to analyze: (a) PPARγ, ADIPOQ, ADIPOR1 and ADIPOR2 gene variations in 92 ADPKD patients through PCR-Sanger sequencing; and (b) adiponectin levels and its oligomerization state by ELISA and Western Blot. Our results indicated that: (a) 14 patients carried the PPARγ SNP, 29 patients carried the ADIPOQ SNP rs1501299, and 25 patients carried the analyzed ADIPOR1 SNPs. Finally, 82 patients carried ADIPOR2 SNPs; and (b) Adiponectin is statistically lower in ADPKD patients compared to controls, and further statistically lower in ESRD than in non-ESRD patients. An inverse relationship between adiponectin and albumin and between adiponectin and creatinine and a direct relationship between adiponectin and eGFR were found. Interestingly, significantly lower levels of adiponectin were found in patients bearing the ADIPOQ rs1501299 SNP and associated with low levels of eGFR. In conclusion, adiponectin levels and the presence of ADIPOQ rs1501299 genotype are significantly associated with a worse ADPKD phenotype, indicating that both could potentially provide important insights into the disease. Further studies are warranted to understand the pathophysiological role of adiponectin in ADPKD patients.

Visceral Adiposity and Progression of ADPKD: A Cohort Study of Patients From the TEMPO 3:4 Trial

Rationale & ObjectiveBody-mass index (BMI) is an independent predictor of kidney disease progression in individuals with autosomal dominant polycystic kidney disease (ADPKD). Adipocytes do not simply act as a fat reservoir but are active endocrine organs. We hypothesized that greater visceral abdominal adiposity would associate with more rapid kidney growth in ADPKD and influence the efficacy of tolvaptan. Study DesignA retrospective cohort study. Setting & Participants1053 patients enrolled in the TEMPO 3:4 tolvaptan trial with ADPKD and high risk of rapid disease progression. PredictorEstimates of visceral adiposity extracted from coronal plane MRIs using deep learning. OutcomeAnnual change in total kidney volume (TKV) and effect of tolvaptan on kidney growth. Analytical ApproachMultinomial logistic regression and linear mixed models. ResultsIn fully adjusted models, the highest tertile of visceral adiposity was associated with greater odds of annual change in TKV of ≥7% vs. <5% (OR: 4.78 [3.03, 7.47]). The association was stronger in females than males (interaction p<0.01). In linear mixed models with an outcome of % change in TKV per year, tolvaptan efficacy (% change in TKV) was reduced with higher visceral adiposity (three-way interaction of treatment*time*visceral adiposity p=0.002). Visceral adiposity significantly improved classification performance of predicting rapid annual % change in TKV for individuals with a normal BMI (De-Long’s test Z-score: -2.03; p=0.04). Greater visceral adiposity was not associated with estimated glomerular filtration rate (eGFR) slope in the overall cohort; however, visceral adiposity was associated with more rapid decline in eGFR slope (below the median) in females (fully adjusted OR 1.06 [1.01, 1.11] per 10 unit increase in visceral adiposity) but not males (0.98 [0.95, 1.02]). LimitationsRetrospective; rapid progressors; computational demand of deep learning. ConclusionsVisceral adiposity that can be quantified by MRI in the coronal plane using a deep learning segmentation model, independently associates with more rapid kidney growth, and improves classification of rapid progression in individuals with a normal BMI. Tolvaptan efficacy decreases with increasing visceral adiposity.

Novel Potential Therapeutic Targets in Autosomal Dominant Polycystic Kidney Disease from the Perspective of Cell Polarity and Fibrosis.

Autosomal dominant polycystic kidney disease (ADPKD), a congenital genetic disorder, is a notable contributor to the prevalence of chronic kidney disease worldwide. Despite the absence of a complete cure, ongoing research aims for early diagnosis and treatment. Although agents such as tolvaptan and mTOR inhibitors have been utilized, their effectiveness in managing the disease during its initial phase has certain limitations. This review aimed to explore new targets for the early diagnosis and treatment of ADPKD, considering ongoing developments. We particularly focus on cell polarity, which is a key factor that influences the process and pace of cyst formation. In addition, we aimed to identify agents or treatments that can prevent or impede the progression of renal fibrosis, ultimately slowing its trajectory toward end-stage renal disease. Recent advances in slowing ADPKD progression have been examined, and potential therapeutic approaches targeting multiple pathways have been introduced. This comprehensive review discusses innovative strategies to address the challenges of ADPKD and provides valuable insights into potential avenues for its prevention and treatment.

Secondary infertility due to necrospermia in men with autosomal-dominant polycystic kidney disease: a report of two cases.

Autosomal-dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease characterized by the formation of numerous cysts in organs other than the kidneys. Although female patients with ADPKD do not have direct fertility problems, infertility in male patients may arise following the formation of cystic lesions in the lower seminal tract, which impair the function of spermatozoa. Generally, the treatment strategy for necrospermia depends on the severity of sperm viability, and intracytoplasmic sperm injection may be offered to patients with necrospermia. We report two cases of secondary infertility in men with ADPKD. These men experienced an inability to reproduce naturally after the previous birth of a child, suggesting a progressive deterioration of semen quality. Semen analysis showed necrospermia in both patients, and transrectal ultrasound revealed marked dilatation of the seminal vesicles bilaterally. The main cause of secondary infertility in male patients with ADPKD is sperm death resulting from progressive dilatation of seminal vesicles. Further research is needed on the appropriate follow-up schedule for men with ADPKD who desire to reproduce naturally.

Notch3 as a novel therapeutic target for the treatment of ADPKD by regulating cell proliferation and renal cyst development

Autosomal dominant polycystic kidney disease (ADPKD) is a common monogenic kidney disease. Emerging research indicates that the Notch signaling pathway plays an indispensable role in the pathogenesis of numerous kidney diseases, including ADPKD. Herein, we identified that Notch3 but not other Notch receptors was overexpressed in renal tissues from mice with ADPKD and ADPKD patients. Inhibiting Notch3 with γ-secretase inhibitors, which blocks a proteolytic cleavage required for Notch3 activation, or shRNA knockdown of Notch3 significantly delayed renal cyst growth in vitro and in vivo. Subsequent mechanistic study elucidated that the cleaved intracellular domain of Notch3 (N3ICD) and Hes1 could bind to the PTEN promoter, leading to transcriptional inhibition of PTEN. This further activated the downstream PI3K-AKT-mTOR pathway and promoted renal epithelial cell proliferation. Overall, Notch3 was identified as a novel contributor to renal epithelial cell proliferation and cystogenesis in ADPKD. We envision that Notch3 represents a promising target for ADPKD treatment.

Clinical Characteristics and Kidney Outcomes in Chinese Patients with Autosomal Dominant Polycystic Kidney Disease.

The management of autosomal dominant polycystic kidney disease (ADPKD) remains challenging with variable and uncertain genotype-phenotype correlations. The Mayo clinic imaging classification allows a more accurate risk stratification but is limited by the atypical imaging patterns. We aim to assess the clinical characteristics and the morphology of the cystic kidneys in a cohort of Chinese patients with ADPKD. Ninety-eight patients with ADPKD were recruited prospectively from August 2019 to December 2020 in Prince of Wales Hospital, Hong Kong. They were subsequently followed up every 6 months for a minimum of2 years. We reviewed the clinical characteristics and MRI imaging patterns at baseline and the kidney outcome at the end of the follow-up. Atypical imaging patterns included unilateral; segmental; asymmetric; lopsided and bilateral atrophy as defined by the Mayo Imaging Classification. Mean age was 51.5 ± 14.3 years old and the mean eGFR 68.7 ± 27.5 ml/min per 1.73 m2. The ninety-eight patients included 36 males:62 females. Seventy-six patients (77.6%) had a family history. Seventeen of the 98 (17.3%) patients had atypical imaging patterns. Compared to typical cases, atypical cases were older at the time of diagnosis (49.5 ± 16.0 vs 33.0 ± 13.0 years, p<0.001), at the time of starting antihypertensive medications (52.4 ± 14.8 vs 39.7 ± 11.0 years, p=0.001) and less likely to have a positive family history (58.8% vs 81.5%, p=0.042). Patients with atypical patterns showed a lower eGFR decline as compared to those with the typical pattern (-0.86 ± 4.34 vs -3.44 ± 4.07 ml/min per 1.73m2/year, p=0.022). In this cohort of Chinese patients with ADPKD, an atypical imaging pattern was observed in 17% of the cases, associated with later presentation and a milder disease course. Future genotyping studies will help to define the genetic architecture and the basis for the phenotypic spectrum in Chinese ADPKD patients.

Kidney Energetics and Cyst Burden in Autosomal Dominant Polycystic Kidney Disease: A Pilot Study

Rationale & ObjectiveIn this pilot study, we hypothesized that autosomal dominant polycystic kidney disease (ADPKD) is characterized by impaired kidney oxidative metabolism that associates with kidney size and cyst burden. Study DesignCross-sectional study. Setting & ParticipantsTwenty adults with ADPKD (31±6 years of age, 65% women, BMI: 26.8 [22.7, 30.4] kg/m2, eGFR (2021 CKD-EPI Creatinine): 103±18 ml/min/1.73m2, height-adjusted total kidney volume [HtTKV]: 731±370 ml/m, Mayo Classifications: 1B [5%], 1C [42%], 1D [21%], 1E [32%]) and 11 controls in normal weight category (NWC; 25±3 years of age, 45% women, BMI: 22.5 [21.7, 24.2] kg/m2, eGFR: 113±15 ml/min/1.73m2, HtTKV: 159±31 ml/m) at the University of Colorado Anschutz Medical Campus. PredictorsADPKD status (yes/no) and severity (Mayo Classifications). OutcomesHtTKV and cyst burden by MRI, kidney oxidative metabolism and perfusion by 11C-acetate PET/CT, insulin sensitivity by hyperinsulinemic-euglycemic clamps (presented as ratio of M-value of steady state insulin concentration [M/I]). Analytical ApproachChi-square/Fisher’s exact tests used for categorical variables and t-tests/ Mann-Whitney U tests for continuous variables. Pearson correlation used to estimate the relationships between variables. ResultsCompared to NWC, participants with ADPKD exhibited lower mean±SD M/I ratio (0.586±0.205 vs. 0.424±0.171 (mg/kg lean/min) / (μIU/mL), p=0.04), lower median [p25, p75] cortical perfusion (1.93 [1.80, 2.09 vs. 0.68 [0.47, 1.04] mL/min/g, p<0.001) and lower median [p25, p75] total kidney oxidative metabolism (0.17 [0.16,0.19] vs. 0.14 [0.12, 0.15] min-1, p=0.001) in voxel-wise models excluding cysts. HtTKV correlated inversely with cortical perfusion (r:-0.83, p<0.001), total kidney oxidative metabolism (r:-0.61, p<0.001) and M/I (r:-0.41, p=0.03). LimitationsSmall sample size and cross-sectional design. ConclusionAdults with ADPKD and preserved kidney function exhibited impaired renal perfusion and kidney oxidative metabolism across a wide range of cysts and kidney enlargements.

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 etal. 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.

Inhibition of pannexin-1 does not restore electrolyte balance in precystic Pkd1 knockout mice.

Mutations in PKD1 and PKD2 cause autosomal dominant polycystic kidney disease (ADPKD), which is characterized by the formation of fluid-filled cysts in the kidney. In a subset of ADPKD patients, reduced blood calcium (Ca2+) and magnesium (Mg2+) concentrations are observed. As cystic fluid contains increased ATP concentrations and purinergic signaling reduces electrolyte reabsorption, we hypothesized that inhibiting ATP release could normalize blood Ca2+ and Mg2+ levels in ADPKD. Inducible kidney-specific Pkd1 knockout mice (iKsp-Pkd1-/-) exhibit hypocalcemia and hypomagnesemia in a precystic stage and show increased expression of the ATP-release channel pannexin-1. Therefore, we administered the pannexin-1 inhibitor brilliant blue-FCF (BB-FCF) every other day from Day 3 to 28 post-induction of Pkd1 gene inactivation. On Day 29, both serum Ca2+ and Mg2+ concentrations were reduced in iKsp-Pkd1-/- mice, while urinary Ca2+ and Mg2+ excretion was similar between the genotypes. However, serum and urinary levels of Ca2+ and Mg2+ were unaltered by BB-FCF treatment, regardless of genotype. BB-FCF did significantly decrease gene expression of the ion channels Trpm6 and Trpv5 in both control and iKsp-Pkd1-/- mice. Finally, no renoprotective effects of BB-FCF treatment were observed in iKsp-Pkd1-/- mice. Thus, administration of BB-FCF failed to normalize serum Ca2+ and Mg2+ levels.

410 Results of a Survey on How Nephrology Providers Assess Kidney Size for Autosomal Dominant Polycystic Kidney Disease

410 Results of a Survey on How Nephrology Providers Assess Kidney Size for Autosomal Dominant Polycystic Kidney Disease

Feasibility of Water Therapy for Slowing Autosomal Dominant Polycystic Kidney Disease Progression.

In animal models of ADPKD, high water intake (HWI) decreases vasopressin secretion and slows disease progression, but the efficacy of HWI in human ADPKD is uncertain. This exploratory, prospective, crossover study of ADPKD subjects (n=7) evaluated the hypothesis that HWI slows the rate of increase in height-adjusted total kidney volume (ht-TKV; a biomarker for ADPKD progression) and reduces pain. Subjects at high risk of ADPKD progression (i.e., Mayo Imaging Classifications 1C/1D) were evaluated during 6 months of usual water intake (UWI), followed by 12 months of HWI calculated to reduce urine osmolality (Uosm) to < 285 mOsm/kg. Measurements of Uosm, serum copeptin (secreted in equimolar amounts with vasopressin), MRI measurements of htTKV, and pain survey responses were compared between HWI and UWI. During HWI, mean 24-hour Uosm decreased compared to UWI (428 [398-432] mOsm/kg vs. 209 [190-223] mOsm/kg; p=0.01), indicating adherence to the protocol. Decreases during HWI also occurred in levels of serum copeptin (5.8±2.0 pmol/L to 4.2±1.6 pmol/L; p=0.03), annualized rate of increase in ht-TKV (6.8% [5.9 - 8.5] to 4.4% [3.0 - 5.0]; p<0.02), pain occurrence and pain interference during sleep (p<0.01). HWI was well tolerated. HWI in patients at risk of rapid progression of ADPKD slowed the rate of ht-TKV growth and reduced pain. This suggests that suppressing vasopressin levels by HWI provides an effective non-pharmacologic treatment of ADPKD.

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.

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. 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. 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. 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.

End-stage ADPKD with a low-frequency PKD1 mosaic variant accelerated by chemoradiotherapy

Autosomal dominant polycystic kidney disease (ADPKD) is commonly caused by PKD1, and mosaic PKD1 variants result in milder phenotypes. We present the case of a 32 year-old male with chronic active Epstein–Barr virus who underwent bone marrow transplantation with chemoradiotherapy at age 9. Despite a low-frequency mosaic splicing PKD1 variant, he developed severe renal cysts and end-stage renal disease in his 30 s. This case highlights how environmental factors may contribute to the genetic predisposition to ADPKD.

Tacrolimus-Associated Thrombotic Microangiopathy Presenting with Ischemic Colitis After Kidney Transplantation: A Case Report

Calcineurin inhibitors (CNIs) are a significant component of the immunosuppressive regimen after kidney transplantation. By inhibiting cytokine gene transcription, CNIs suppress T cell and T cell-dependent B cell activation. Tacrolimus is preferred in most patients undergoing kidney transplantation. Thrombotic microangiopathy (TMA) is a severe but rare complication of CNIs therapy. TMA defines a specific pathologic lesion of arterioles and capillaries that leads to microvascular thrombosis. A 45-year-old male underwent kidney transplantation five months ago due to autosomal dominant polycystic kidney disease (ADPKD). His triple-maintenance immunosuppressive therapy includes tacrolimus. Abdominal pain and bloody diarrhea occurred in the fifth month of posttransplant. The edematous and erythematous mucosa of the ascending colon was detected on the colonoscopy. The foci of microthrombi inside the vessel lumen in the lamina propria were shown biopsy. The thrombosis or occlusion was excluded with computerized tomography (CT) angiography in abdominal vessels. The fragmented red blood cells and moderate thrombocytopenia were detected on the peripheral blood smear. Eventually, TMA diagnosis was established through laboratory and histological findings. Tacrolimus was suspected as the trigger of the pathological process and promptly switched to the everolimus. Afterward, laboratory abnormalities and clinical symptoms were improved. In this case, we intend to emphasize drug-associated TMA and atypical presentations, such as colonic microvasculature involvement.

Quantitative susceptibility mapping for detection of kidney stones, hemorrhage differentiation, and cyst classification in ADPKD.

The objective is to demonstrate feasibility of quantitative susceptibility mapping (QSM) in autosomal dominant polycystic kidney disease (ADPKD) patients and to compare imaging findings with traditional T1/T2w magnetic resonance imaging (MRI). Thirty-three consecutive patients (11 male, 22 female) diagnosed with ADPKD were initially selected. QSM images were reconstructed from the multiecho gradient echo data and compared to co-registered T2w, T1w, and CT images. Complex cysts were identified and classified into distinct subclasses based on their imaging features. Prevalence of each subclass was estimated. QSM visualized two renal calcifications measuring 9 and 10mm and three pelvic phleboliths measuring 2mm but missed 24 calcifications measuring 1mm or less and 1 larger calcification at the edge of the field of view. A total of 121 complex T1 hyperintense/T2 hypointense renal cysts were detected. 52 (43%) Cysts appeared hyperintense on QSM consistent with hemorrhage; 60 (49%) cysts were isointense with respect to simple cysts and normal kidney parenchyma, while the remaining 9 (7%) were hypointense. The presentation of the latter two complex cyst subtypes is likely indicative of proteinaceous composition without hemorrhage. Our results indicate that QSM of ADPKD kidneys is possible and uniquely suited to detect large renal calculi without ionizing radiation and able to identify properties of complex cysts unattainable with traditional approaches.

Genotype-phenotype of autosomal dominant polycystic kidney disease in Malta

BackgroundAutosomal dominant polycystic kidney disease (ADPKD) is characterized by the development of multiple renal cysts causing kidney enlargement and end-stage renal disease (ESRD) in half the patients by 60 years of age. The aim of the study was to determine the genetic aetiology in Maltese patients clinically diagnosed with ADPKD and correlate the clinical features. MethodsA total of 60 patients over 18 years of age clinically diagnosed with ADPKD were studied using a customized panel of genes that had sufficient evidence of disease diagnosis using next generation sequencing (NGS). The genes studied were PKD1, PKD2, GANAB, DNAJB11, PKHD1 and DZIP1L. Selected variants were confirmed by bidirectional Sanger sequencing with specifically designed primers. Cases where no clinically significant variant was identified by the customized gene panel were then studied by Whole Exome Sequencing (WES). Microsatellite analysis was performed to determine the origin of an identified recurrent variant in the PKD2 gene. Clinical features were studied for statistical correlation with genetic results. ResultsGenetic diagnosis was reached in 49 (82%) of cases studied. Pathogenic/likely pathogenic variants PKD1 and PKD2 gene were found in 25 and in 23 cases respectively. The relative proportion of genetically diagnosed PKD1:PKD2 cases was 42:38. A pathogenic variant in the GANAB gene was identified in 1 (2%) case. A potentially significant heterozygous likely pathogenic variant was identified in PKHD1 in 1 (2%) case. Potentially significant variants of uncertain significance were seen in 4 (7%) cases of the study cohort. No variants in DNAJB11 and DZIP1L were observed. Whole exome sequencing (WES) added the diagnostic yield by 10% over the gene panel analysis. Overall no clinically significant variant was detected in 6 (10%) cases of the study population by a customized gene panel and WES. One recurrent variant the PKD2 c.709+1G > A was observed in 19 (32%) cases. Microsatellite analysis showed that all variant cases shared the same haplotype indicating that their families may have originated from a common ancestor and confirmed it to be a founder variant in the Maltese population.The rate of decline in eGFR was steeper and progression to ESRD was earlier in cases with PKD1 variants when compared to cases with PKD2 variants. Cases segregating truncating variants in PKD1 showed a significantly earlier onset of ESRD and this was significantly worse in cases with frameshift variants. Overall extrarenal manifestations were commoner in cases segregating truncating variants in PKD1. ConclusionsThis study helps to show that a customized gene panel is the first-line method of choice for studying patients with ADPKD followed by WES which increased the detection of variants present in the PKD1 pseudogene region. A founder variant in the PKD2 gene was identified in our Maltese cohort with ADPKD. Phenotype of patients with ADPKD is significantly related to the genotype confirming the important role of molecular investigations in the diagnosis and prognosis of polycystic kidney disease. Moreover, the findings also highlight the variability in the clinical phenotype and indicate that other factors including epigenetic and environmental maybe be important determinants in Autosomal Dominant Polycystic Kidney Disease.

Comprehensive Analysis of PKD1 and PKD2 by Long-Read Sequencing in Autosomal Dominant Polycystic Kidney Disease.

Autosomal dominant polycystic kidney disease (ADPKD) is mainly caused by heterogeneous variants in the PKD1 and PKD2 genes. Genetic analysis of PKD1 has been challenging due to homology with 6 PKD1 pseudogenes and high GC content. A single-tube multiplex long-range-PCR and long-read sequencing-based assay termed "comprehensive analysis of ADPKD" (CAPKD) was developed and evaluated in 170 unrelated patients by comparing to control methods including next-generation sequencing (NGS) and multiplex ligation-dependent probe amplification. CAPKD achieved highly specific analysis of PKD1 with a residual noise ratio of 0.05% for the 6 pseudogenes combined. CAPKD identified PKD1 and PKD2 variants (ranging from variants of uncertain significance to pathogenic) in 160 out of the 170 patients, including 151 single-nucleotide variants (SNVs) and insertion-deletion variants (indels), 6 large deletions, and one large duplication. Compared to NGS, CAPKD additionally identified 2 PKD1 variants (c.78_96dup and c.10729_10732dup). Overall, CAPKD increased the rate of variant detection from 92.9% (158/170) to 94.1% (160/170), and the rate of diagnosis with pathogenic or likely pathogenic variants from 82.4% (140/170) to 83.5% (142/170). CAPKD also directly determined the cis-/trans-configurations in 11 samples with 2 or 3 SNVs/indels, and the breakpoints of 6 large deletions and one large duplication, including 2 breakpoints in the intron 21 AG-repeat of PKD1, which could only be correctly characterized by aligning to T2T-CHM13. CAPKD represents a comprehensive and specific assay toward full characterization of PKD1 and PKD2 variants, and improves the genetic diagnosis for ADPKD.