Search Results (41)

Background/Objectives: Horseshoe kidney is a congenital anomaly characterized by the fusion of the kidneys at the lower pole. Polycystic kidney disease with horseshoe kidney is called polycystic horseshoe kidney. Genetic testing is essential for the diagnosis of polycystic horseshoe kidney disease because it can result from a number of genetic disorders. Fewer than 20 cases of polycystic horseshoe kidney have been reported to date. However, polycystic horseshoe kidney disease was mostly diagnosed via autopsy or radiologic imaging techniques including computed tomography, magnetic resonance imaging, and angiography. Because polycystic kidney disease has various causes, genetic testing is essential for the diagnosis of autosomal dominant polycystic kidney disease (ADPKD) in patients with polycystic horseshoe kidney disease. At present, the diagnosis of ADPKD is made using genetic approaches, including next-generation sequencing. We reported a potentially pathogenic polycystin 1 (PKD1) gene in a patient with ADPKD and horseshoe kidney. Methods: We performed the sequencing of the PKD1 gene and radiological examinations (computed abdominal tomography). Results: Computed abdominal tomography revealed enlarged kidneys with multiple cysts fused at the lower poles, indicating polycystic HSK. The sequencing of the PKD1 gene revealed a heterozygous pathogenic variant c.165_171del (p.Leu56ArgfsTer15), which genetically confirmed the diagnosis of ADPKD. The patient was treated with an angiotensin II receptor blocker. Conclusions: In this case report, we suggest that genetic testing becomes the key approach to the diagnosis of ADPKD with horseshoe kidney. Additionally, this approach offers the benefit of avoiding the possibility of the condition being mistakenly diagnosed or diagnosed late due to its uncommon occurrence and nonspecific symptoms. Full article

Polycystic kidney disease (PKD), a ciliopathy caused primarily by mutations in the Pkd1 and Pkd2 genes, disrupts renal structure and function, leading to progressive renal failure. The primary cilium, a sensory organelle essential for cellular signaling, plays a pivotal role in maintaining renal function. Among its signaling components, G-protein-coupled receptors (GPCRs) within the cilium have gained significant attention for their localized functions and their contribution to PKD pathogenesis. Dysfunction of ciliary GPCR signaling alters key downstream pathways, including mammalian target of rapamycin (mTOR), cyclic adenosine monophosphate (cAMP), and calcium homeostasis, exacerbating cyst formation and disease progression. Additionally, interactions between ciliary GPCRs and PKD-associated proteins, such as Polycystin-1 (PC1) and Polycystin-2 (PC2), underline the complexity of PKD mechanisms. Recent advances highlight GPCRs as promising therapeutic targets for ciliopathies, including PKD. Emerging GPCR modulators and drugs in clinical trials show the potential to restore ciliary signaling and attenuate disease progression. This paper explores the physiological functions of ciliary GPCRs, their mechanistic links to PKD, and the therapeutic implications of targeting these receptors, offering insights into future research directions and therapeutic strategies for PKD. Full article

Background: Polycystin 1 (PC1) and polycystin 2 (PC2) proteins are members of the transient receptor potential (TRP) channels family and are encoded from PKD1 and PKD2 genes, respectively. Until recently, the role of PKD1 and PKD2 has been associated with the pathogenesis of the kidney since mutations in these genes cause autosomal dominant polycystic kidney disease (ADPKD). Recent data implicates polycystins in the pathogenesis of solid tumors. In this aspect, the expression of PKD1 and PKD2 in human astrocytomas is largely unknown. The aim of the present research study was to investigate the expression of PKD1 and PKD2 in astrocytic tumors and correlate it with clinicopathological characteristics such as the grade of malignancy, age, and gender of the patients. Methods: A total of 70 cases—corresponding to 8 grade II (diffuse fibrillary astrocytomas), 12 grade III (anaplastic astrocytomas), and 50 grade IV (glioblastomas multiforme)—were examined. The mRNA expression levels of PKD1 and PKD2 were determined through molecular qRT-PCR analysis using the relative quantification ΔΔCt method and the expression of PC1 and PC2 was detected through immunohistochemistry using the semi-quantitative H-score system. Results: Increased levels of PKD1 and PKD2 in astrocytomas were found compared with that of a normal brain (p < 0.05). Glioblastomas demonstrated the greatest increase in PKD1 and PKD2 expression compared to other grades of malignancy (p < 0.05). The same pattern of expression showed PC1 and PC2 proteins. A significant correlation between PKD1 and PKD2 as well as PC1 and PC2 expressions was found (p < 0.05). Although no association was detected between PC1 or PC2 and Ki67 expression (p > 0.05), a significant correlation between PC1 and p53 immunoexpressions, in grade III and between PC2 and p53 immunoexpressions, in grade II astrocytomas (p < 0.01) has emerged. PC1 expression was correlated with age of the patients (p < 0.05). PKD1 and PKD2 expression were negatively correlated with the prognosis of glioma patients. Conclusions: The results of this study indicate the potential involvement of polycystins in the pathogenesis of astrocytomas. However, further research is required to fully understand the mechanisms that these molecules are implicated. Full article

Polycystic kidney disease (PKD) is the most common hereditary disorder that disrupts renal function and frequently progresses to end-stage renal disease. Recent advances have elucidated the critical role of primary cilia and ciliary ion channels, including transient receptor potential (TRP) channels, cystic fibrosis transmembrane conductance regulator (CFTR), and polycystin channels, in the pathogenesis of PKD. While some channels primarily function as chloride conductance channels (e.g., CFTR), others primarily regulate calcium (Ca⁺²) homeostasis. These ion channels are essential for cellular signaling and maintaining the normal kidney architecture. Dysregulation of these pathways due to genetic mutations in PKD1 and PKD2 leads to disrupted Ca⁺² and cAMP signaling, aberrant fluid secretion, and uncontrolled cellular proliferation, resulting in tubular cystogenesis. Understanding the molecular mechanisms underlying these dysfunctions has opened the door for innovative therapeutic strategies, including TRPV4 activators, CFTR inhibitors, and calcimimetics, to mitigate cyst growth and preserve renal function. This review summarizes the current knowledge on the roles of ciliary ion channels in PKD pathophysiology, highlights therapeutic interventions targeting these channels, and identifies future research directions for improving patient outcomes. Full article

The formation of the embryonic left–right axis is a fundamental process in animals, which subsequently conditions both the shape and the correct positioning of internal organs. During vertebrate early development, a transient structure, known as the left–right organizer, breaks the bilateral symmetry in a manner that is critically dependent on the activity of motile and immotile cilia or asymmetric cell migration. Extensive studies have partially elucidated the molecular pathways that initiate left–right asymmetric patterning and morphogenesis. Wnt/planar cell polarity signaling plays an important role in the biased orientation and rotational motion of motile cilia. The leftward fluid flow generated in the cavity of the left–right organizer is sensed by immotile cilia through complex mechanisms to trigger left-sided calcium signaling and lateralized gene expression pattern. Disrupted asymmetric positioning or impaired structure and function of cilia leads to randomized left–right axis determination, which is closely linked to laterality defects, particularly congenital heart disease. Despite of the formidable progress made in deciphering the critical contribution of cilia to establishing the left–right asymmetry, a strong challenge remains to understand how cilia generate and sense fluid flow to differentially activate gene expression across the left–right axis. This review analyzes mechanisms underlying the asymmetric morphogenesis and function of the left–right organizer in left–right axis formation. It also aims to identify important questions that are open for future investigations. Full article

Spontaneous coronary artery dissection (SCAD) is a spontaneous intimal tear of the coronary artery wall. A factor rarely associated with SCAD is autosomal dominant polycystic kidney disease (ADPKD). Using the PRISMA guidelines, we identified 10 unique cases of SCAD in ADPKD patients reported between 1998 and 2021. Ages ranged from 36 to 59 years, with an average of 44.6 years. The majority of patients were female (80%). Each case was diagnosed with a cardiovascular event: ST-elevation myocardial infarction (STEMI) in 40%, non-ST elevation myocardial infarction (NSTEMI) in 50%, and stable angina in 10%. Conservative management was used in 60% of cases. There is a significant gap in our understanding of the relationship between SCAD and ADPKD. Polycystin complex can lead to structural abnormalities in blood vessels, resulting in vascular leaks and vessel rupture. This suggests that ADPKD patients may have an elevated risk of arteriopathies, including coronary artery dissection. Full article

Cytokinesis, the last step in cell division, separates daughter cells through mechanical force. This is often through the force produced by an actomyosin contractile ring. In fission yeast cells, the ring helps recruit a mechanosensitive ion channel, Pkd2, to the cleavage furrow, whose activation by membrane tension promotes calcium influx and daughter cell separation. However, it is unclear how the activities of Pkd2 may affect the actomyosin ring. Here, through both microscopic and genetic analyses of a hypomorphic pkd2 mutant, we examined the potential role of this essential gene in assembling the contractile ring. The pkd2-81KD mutation significantly increased the counts of the type II myosin heavy chain Myo2 (+18%), its regulatory light chain Rlc1 (+37%) and actin (+100%) molecules in the ring, compared to the wild type. Consistent with a regulatory role of Pkd2 in the ring assembly, we identified a strong negative genetic interaction between pkd2-81KD and the temperature-sensitive mutant myo2-E1. The pkd2-81KD myo2-E1 cells often failed to assemble a complete contractile ring. We conclude that Pkd2 modulates the recruitment of type II myosin and actin to the contractile ring, suggesting a novel calcium-dependent mechanism regulating the actin cytoskeletal structures during cytokinesis. Full article

Polycystic kidney disease (PKD) is characterized by extensive cyst formation and progressive fibrosis. However, the molecular mechanisms whereby the loss/loss-of-function of Polycystin 1 or 2 (PC1/2) provokes fibrosis are largely unknown. The small GTPase RhoA has been recently implicated in cystogenesis, and we identified the RhoA/cytoskeleton/myocardin-related transcription factor (MRTF) pathway as an emerging mediator of epithelium-induced fibrogenesis. Therefore, we hypothesized that MRTF is activated by PC1/2 loss and plays a critical role in the fibrogenic reprogramming of the epithelium. The loss of PC1 or PC2, induced by siRNA in vitro, activated RhoA and caused cytoskeletal remodeling and robust nuclear MRTF translocation and overexpression. These phenomena were also manifested in PKD1 (RC/RC) and PKD2 (WS25/−) mice, with MRTF translocation and overexpression occurring predominantly in dilated tubules and the cyst-lining epithelium, respectively. In epithelial cells, a large cohort of PC1/PC2 downregulation-induced genes was MRTF-dependent, including cytoskeletal, integrin-related, and matricellular/fibrogenic proteins. Epithelial MRTF was necessary for the paracrine priming of the fibroblast–myofibroblast transition. Thus, MRTF acts as a prime inducer of epithelial fibrogenesis in PKD. We propose that RhoA is a common upstream inducer of both histological hallmarks of PKD: cystogenesis and fibrosis. Full article

Bone mechanotransduction is a critical process during skeletal development in embryogenesis and organogenesis. At the same time, the type and level of mechanical loading regulates bone remodeling throughout the adult life. The aberrant mechanosensing of bone cells has been implicated in the development and progression of bone loss disorders, but also in the bone-specific aspect of other clinical entities, such as the tumorigenesis of solid organs. Novel treatment options have come into sight that exploit the mechanosensitivity of osteoblasts, osteocytes, and chondrocytes to achieve efficient bone regeneration. In this regard, runt-related transcription factor 2 (Runx2) has emerged as a chief skeletal-specific molecule of differentiation, which is prominent to induction by mechanical stimuli. Polycystins represent a family of mechanosensitive proteins that interact with Runx2 in mechano-induced signaling cascades and foster the regulation of alternative effectors of mechanotransuction. In the present narrative review, we employed a PubMed search to extract the literature concerning Runx2, polycystins, and their association from 2000 to March 2024. The keywords stated below were used for the article search. We discuss recent advances regarding the implication of Runx2 and polycystins in bone remodeling and regeneration and elaborate on the targeting strategies that may potentially be applied for the treatment of patients with bone loss diseases. Full article

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. Full article

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 (α5β1γ1) 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. Full article

Autosomal-Dominant Polycystic Kidney Disease (ADPKD) is a monogenic disorder initiated by mutations in either PKD1 or PKD2 genes, responsible for encoding polycystin 1 and polycystin 2, respectively. These proteins are primarily located within the primary cilia. The disease follows an inexorable progression, leading most patients to severe renal failure around the age of 50, and extra-renal complications are frequent. A cure for ADPKD remains elusive, but some measures can be employed to manage symptoms and slow cyst growth. Tolvaptan, a vasopressin V2 receptor antagonist, is the only drug that has been proven to attenuate ADPKD progression. Recently, autophagy, a cellular recycling system that facilitates the breakdown and reuse of aged or damaged cellular components, has emerged as a potential contributor to the pathogenesis of ADPKD. However, the precise role of autophagy in ADPKD remains a subject of investigation, displaying a potentially twofold impact. On the one hand, impaired autophagy may promote cyst formation by inducing apoptosis, while on the other hand, excessive autophagy may lead to fibrosis through epithelial to mesenchymal transition. Promising results of autophagy inducers have been observed in preclinical studies. Clinical trials are warranted to thoroughly assess the long-term safety and efficacy of a combination of autophagy inducers with metabolic and/or aquaferetic drugs. This research aims to shed light on the complex involvement of autophagy in ADPKD, explore the regulation of autophagy in disease progression, and highlight the potential of combination therapies as a promising avenue for future investigations. Full article

The PKD1 gene, encoding protein polycystin-1 (PC1), is responsible for 85% of cases of autosomal dominant polycystic kidney disease (ADPKD). PC1 has been shown to be present in urinary exosome−like vesicles (PKD−ELVs) and lowered in individuals with germline PKD1 mutations. A label−free mass spectrometry comparison of urinary PKD−ELVs from normal individuals and those with PKD1 mutations showed that several proteins were reduced to a degree that matched the decrease observed in PC1 levels. Some of these proteins, such as polycystin-2 (PC2), may be present in a higher-order multi-protein assembly with PC1—the polycystin complex (PCC). CU062 (Q9NYP8) is decreased in ADPKD PKD−ELVs and, thus, is a candidate PCC component. CU062 is a small glycoprotein with a signal peptide but no transmembrane domain and can oligomerize with itself and interact with PC1. We investigated the localization of CU062 together with PC1 and PC2 using immunofluorescence (IF). In nonconfluent cells, all three proteins were localized in close proximity to focal adhesions (FAs), retraction fibers (RFs), and RF-associated extracellular vesicles (migrasomes). In confluent cells, primary cilia had PC1/PC2/CU062 + extracellular vesicles adherent to their plasma membrane. In cells exposed to mitochondrion-decoupling agents, we detected the development of novel PC1/CU062 + ring-like structures that entrained swollen mitochondria. In contact-inhibited cells under mitochondrial stress, PC1, PC2, and CU062 were observed on large, apically budding extracellular vesicles, where the proteins formed a reticular network on the membrane. CU062 interacts with PC1 and may have a role in the identification of senescent mitochondria and their extrusion in extracellular vesicles. Full article

Cardiomyopathy is commonly observed in patients with autosomal dominant polycystic kidney disease (ADPKD), even when they have normal renal function and arterial pressure. The role of cardiomyocyte polycystin-1 (PC1) in cardiovascular pathophysiology remains unknown. PC1 is a potential regulator of BIN1 that maintains T-tubule structure, and alterations in BIN1 expression induce cardiac pathologies. We used a cardiomyocyte-specific PC1-silenced (PC1-KO) mouse model to explore the relevance of cardiomyocyte PC1 in the development of heart failure (HF), considering reduced BIN1 expression induced T-tubule remodeling as a potential mechanism. PC1-KO mice exhibited an impairment of cardiac function, as measured by echocardiography, but no signs of HF until 7–9 months of age. Of the PC1-KO mice, 43% died suddenly at 7 months of age, and 100% died after 9 months with dilated cardiomyopathy. Total BIN1 mRNA, protein levels, and its localization in plasma membrane-enriched fractions decreased in PC1-KO mice. Moreover, the BIN1 + 13 isoform decreased while the BIN1 + 13 + 17 isoform was overexpressed in mice without signs of HF. However, BIN1 + 13 + 17 overexpression was not observed in mice with HF. T-tubule remodeling and BIN1 score measured in plasma samples were associated with decreased PC1-BIN1 expression and HF development. Our results show that decreased PC1 expression in cardiomyocytes induces dilated cardiomyopathy associated with diminished BIN1 expression and T-tubule remodeling. In conclusion, positive modulation of BIN1 expression by PC1 suggests a novel pathway that may be relevant to understanding the pathophysiological mechanisms leading to cardiomyopathy in ADPKD patients. Full article

Background: Autosomal dominant polycystic kidney disease (ADPKD) is a condition usually caused by a single gene mutation and manifested by both renal and extrarenal features, eventually leading to end-stage renal disease (ESRD) by the median age of 60 years worldwide. Approximately 89% of ADPKD patients had either PKD1 or PKD2 gene mutations. The majority (85%) of the mutations are in the PKD1 gene, especially in the context of family history. Objectives: This study investigated the genetic basis and the undiscovered genes that are involved in ADPKD development among the Saudi population. Materials and Methods: In this study, 11 patients with chronic kidney disease were enrolled. The diagnosis of ADPKD was based on history and diagnostic images: CT images include enlargement of renal outlines, renal echogenicity, and presence of multiple renal cysts with dilated collecting ducts, loss of corticomedullary differentiation, and changes in GFR and serum creatinine levels. Next-generation whole-exome sequencing was conducted using the Ion Torrent PGM platform. Results: Of the 11 Saudi patients diagnosed with chronic kidney disease (CKD) and ADPKD, the most common heterozygote nonsynonymous variant in the PKD1 gene was exon15: (c.4264G > A). Two missense mutations were identified with a PKD1 (c.1758A > C and c.9774T > G), and one patient had a PKD2 mutation (c.1445T > G). Three detected variants were novel, identified at PKD1 (c.1758A > C), PKD2L2 (c.1364A > T), and TSC2 (deletion of a’a at the 3’UTR, R1680C) genes. Other variants in PKD1L1 (c.3813_381 4delinsTG) and PKD1L2 (c.404C > T) were also detected. The median age of end-stage renal disease for ADPK patients in Saudi Arabia was 30 years. Conclusion: This study reported a common variant in the PKD1 gene in Saudi patients with typical ADPKD. We also reported (to our knowledge) for the first time two novel missense variants in PKD1 and PKD2L2 genes and one indel mutation at the 3’UTR of the TSC2 gene. This study establishes that the reported mutations in the affected genes resulted in ADPKD development in the Saudi population by a median age of 30. Nevertheless, future protein–protein interaction studies to investigate the influence of these mutations on PKD1 and PKD2 functions are required. Furthermore, large-scale population-based studies to verify these findings are recommended. Full article