bims-bicyki Biomed News
on Bicaudal-C1 and interactors in cystic kidney disease
Issue of 2023‒09‒24
twelve papers selected by
Céline Gagnieux, École Polytechnique Fédérale de Lausanne (EPFL)



  1. Physiol Genomics. 2023 Sep 18.
      Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in polycystin genes, Pkd1 and Pkd2, but the underlying pathogenic mechanisms are poorly understood. To identify genes and pathways that operate downstream of polycystin-2 (PC2), a comprehensive gene expression database was created, cataloging changes in the transcriptome immediately following PC2 protein depletion. To explore cyst initiation processes, an immortalized mouse inner medullary collecting duct line was developed with the ability to knock out the Pkd2 gene conditionally. Genome-wide transcriptome profiling was performed using RNA sequencing (RNA-Seq) in the cells immediately after PC2 was depleted and compared to isogenic control cells. Differentially expressed genes were identified, and a bioinformatic analysis pipeline was implemented. Altered expression of candidate cystogenic genes was validated in Pkd2 knockout (KO) mice. The expression of nearly 900 genes changed upon PC2 depletion. Differentially expressed genes were enriched for genes encoding components of the primary cilia, the canonical Wnt pathway, and MAPK signaling. Amongst PC2-dependent ciliary genes, the transcription factor, Glis3, was significantly downregulated. MAPK signaling formed a key node at the epicenter of PC2-dependent signaling networks. Activation of Wnt and MAPK signaling, concomitant with the downregulation of Glis3, was corroborated in Pkd2 KO mice. The data identify a PC2 cilia-to-nucleus signaling axis and dysregulation of the Gli-similar subfamily of transcription factors as a potential initiator of cyst formation in ADPKD. The catalog of PC2-regulated genes should provide a valuable resource for future ADPKD research and new opportunities for drug development.
    Keywords:  Autosomal dominant polycystic kidney disease; Polycystin-2; RNA sequencing; cystogenesis; in vitro cell model
    DOI:  https://doi.org/10.1152/physiolgenomics.00040.2023
  2. Genes Cells. 2023 Sep 18.
      Autosomal dominant polycystic kidney disease (ADPKD) is a renal disorder caused by mutations in the PKD2 gene, which encodes polycystin-2/Pkd2, a transient receptor potential channel. The precise role of Pkd2 in cyst formation remains unclear. The fission yeast Schizosaccharomyces pombe has a putative transient receptor potential channel, Pkd2, which shares similarities with human Pkd2. In this study, truncation analyses of fission yeast Pkd2 were conducted to investigate its localization and function. The results revealed that Pkd2 localizes not only to the plasma membrane but also to the endoplasmic reticulum (ER) in fission yeast. Furthermore, Pkd2 regulates calcium signaling in fission yeast, with the transmembrane domains of Pkd2 being sufficient for these processes. Specifically, the C-terminal region of Pkd2 plays a crucial role in the regulation of calcium signaling. Interestingly, human Pkd2 also localized to the ER and had some impact on calcium signaling in fission yeast. However, human Pkd2 failed to suppress the loss of fission yeast Pkd2. These findings indicate that hPkd2 may not completely substitute for cellular physiology of fission yeast Pkd2. This study provides insights into the localization and functional characteristics of Pkd2 in fission yeast, contributing to our understanding of the pathogenesis of ADPKD.
    Keywords:  ADPKD; calcium signaling; fission yeast; polycystin
    DOI:  https://doi.org/10.1111/gtc.13069
  3. Am J Kidney Dis. 2023 Sep 19. pii: S0272-6386(23)00808-9. [Epub ahead of print]
      A 68-year-old woman with autosomal dominant polycystic kidney disease (ADPKD) on hemodialysis was admitted for progressive dyspnea over 6 months. On chest X-ray, her cardiothoracic ratio (CTR) had increased from 52.2% 6 months prior, to 71%, and echocardiography revealed diffuse pericardial effusion and right ventricular diastolic insufficiency. A resultant pericardial tamponade was thought to be the cause of the patient's dyspnea, so a pericardiocentesis was performed with a total of 2000 mL of fluid removed. However, 21 days later the same amount of pericardial fluid had reaccumulated. A second pericardiocentesis was performed, followed by transcatheter renal artery embolization (TAE). The kidneys, which were hard on palpation before TAE, softened immediately after TAE. After resolution of the pericardial effusion was confirmed, the patient was discharged after 24 days in hospital. Twelve months later, the patient was asymptomatic, the CTR was decreased to 48% on chest X-ray and CT revealed no reaccumulation of pericardial effusion. This case illustrates a potential relationship between enlarged kidneys in ADPKD and pericardial effusion.
    DOI:  https://doi.org/10.1053/j.ajkd.2023.07.016
  4. Clin Pract. 2023 Aug 24. 13(5): 1035-1042
      Tolvaptan, a selective vasopressin V2 receptor antagonist, is the first and only approved specific treatment for Autosomal-Dominant Polycystic Kidney Disease (ADPKD), and is used in current clinical practice. Real clinical data are missing. In this retrospective study, 41 ADPKD patients received tolvaptan for 3 years, from 2018 to 2021. Total kidney volume (TKV) was measured using Magnetic Resonance Imaging, at initiation and at the end of the treatment period. A complete biochemistry/hematology profile and a 24 h urine volume collection were performed monthly for the first 18 months and every 3 months thereafter. At the end of the treatment period, the median (IQR) estimated Glomerular Filtration Rate (e-GFR) was 5.3 (-1.3, 8.7) mL/min higher than the expected e-GFR decline without treatment, while the prediction for End Stage Chronic Kidney Disease (ESKD) had been prolonged by 1 (0, 2) year. Total Kidney Volume did not change significantly (2250 (1357) mL at 3 years of treatment vs. 2180 (1091) mL expected without treatment, p = 0.48). Younger patients with a relatively preserved e-GFR, lower hypertension burden, better familiar renal prognosis and more severe imaging data showed better outcomes. The aquaretic adverse effects of tolvaptan did not affect renal function and electrolyte balance in 51 patients, in a follow-up period of 18 months. Consequently, tolvaptan seems to be effective in preventing progression of ADPKD when administered in a timely manner in patients with better familiar renal history, shorter hypertension duration and worse imaging profile. Increased diuresis does not affect treatment efficacy.
    Keywords:  ADPKD; aquaretic adverse effects; prediction for ESKD; tolvaptan
    DOI:  https://doi.org/10.3390/clinpract13050092
  5. Acta Med Litu. 2022 ;29(2): 211-216
      Autosomal dominant polycystic kidney disease (ADPKD) with concomitant horseshoe kidney is an extremely rare entity. In this case, we report a 45-year-old male patient with ADPKD and a horseshoe kidney who demonstrated hypertension, urological complications, and discomfort symptoms such as pain, breathing difficulties, and abdominal meteorism. After preoperative assessment and planning, the patient underwent nephrectomy. Bilateral nephrectomy without dividing the isthmus was performed successfully. The isthmus, which had complicated vasculature and was full of cysts, remained intact, avoiding severe bleeding and infection. The postoperative course was uneventful. Keeping the isthmus intact in such cases is a challenge for the surgeon. The rarity of polycystic horseshoe kidney in combination with the altered abdominal anatomy requires the proper preoperative strategy in order to avoid intraoperative complications.
    Keywords:  horseshoe; nephrectomy; polycystic kidney
    DOI:  https://doi.org/10.15388/Amed.2022.29.2.7
  6. Clin J Am Soc Nephrol. 2023 Sep 20.
      Autosomal dominant polycystic kidney disease (ADPKD) is a genetic disorder characterized by kidney cyst formation and progressive kidney function loss. Dietary interventions such as caloric restriction, intermittent fasting, and the ketogenic diet have recently emerged as potential strategies to induce metabolic reprogramming and slow ADPKD progression. We review the available evidence supporting the efficacy and safety of these interventions in ADPKD. Dietary interventions show promise in managing ADPKD by improving metabolic health and reducing oxidative stress. However, while preclinical studies have shown favorable outcomes, limited clinical evidence supports their effectiveness. Also, the long-term consequences of these dietary interventions, including their impact on adverse events in ADPKD patients, remain uncertain. To optimize ADPKD management, patients are advised to follow a dietary regimen that aims to achieve or maintain an ideal weight and includes high fluid intake, low sodium, and limited concentrated sweets. Caloric restriction appears particularly beneficial for individuals with overweight or obesity as it promotes weight loss and improves metabolic parameters. Supplementation with curcumin, ginkgolide B, saponins, vitamin E, niacinamide, or triptolide has demonstrated uncertain clinical benefit in ADPKD patients. Notably, beta-hydroxybutyrate (BHB) supplements have shown promise in animal models; however, their safety and efficacy in ADPKD require further evaluation through well-designed clinical trials. Therefore, the use of these supplements is not currently recommended for ADPKD patients. In summary, dietary interventions such as caloric restriction, intermittent fasting, and the ketogenic diet hold promise in ADPKD management by enhancing metabolic health. However, extensive clinical research is necessary to establish their effectiveness and long-term impacts. Adhering to personalized dietary guidelines, including weight management and specific nutritional restrictions, can contribute to optimal ADPKD management. Future research should prioritize well-designed clinical trials to determine the benefits and safety of dietary interventions and supplementation in ADPKD.
    DOI:  https://doi.org/10.2215/CJN.0000000000000326
  7. Proc Natl Acad Sci U S A. 2023 Sep 26. 120(39): e2302801120
      Primary cilia are specialized organelles supporting the development and function of cells and organisms. Intraflagellar transport (IFT) is essential for cilia formation, maintenance, and function. In C. elegans ciliated sensory neurons, IFT interacts with signaling molecules to generate distinct morphological and function features and also to maintain the integrity of cilia. Here, we report an IFT-dependent feedback control on the conserved MAPKKK DLK-1 in the ciliated sensory neurons. DLK proteins are widely known to act in synapse formation, axon regeneration, and degeneration, but their roles in other neuronal compartments are understudied. By forward genetic screening for altered expression of the endogenously tagged DLK-1 we identified multiple ift mutants showing increased DLK-1 accumulation in the defective sensory endings. We show that in response to acute IFT disruption, DLK-1 accumulates rapidly and reversibly. The expression levels of the transcription factor CEBP-1, known to act downstream of DLK-1 in the development and maintenance of synapses and axons, are also increased in the ciliated sensory neurons of ift mutants. Interestingly, the regulation of CEBP-1 expression shows sensory neuron-type dependency on DLK-1. Moreover, in the sensory neuron AWC, which has elaborate cilia morphology, up-regulated CEBP-1 represses DLK-1 at the transcription level, thereby dampening DLK-1 accumulation. Last, the IFT-dependent regulatory loop of DLK-1 and CEBP-1 offers neuroprotection in a cilia degeneration model. These findings uncover a surveillance mechanism in which tight control on the DLK-1 signaling protects cilia integrity in a context-specific manner.
    Keywords:  AWC sensory neuron; CEBP-1 bZIP protein; CHE-10 Rootletin; CHE-3 dynein; cilia degeneration
    DOI:  https://doi.org/10.1073/pnas.2302801120
  8. Life Sci Alliance. 2023 11;pii: e202301947. [Epub ahead of print]6(11):
      The primary cilium undergoes cell cycle-dependent assembly and disassembly. Dysregulated ciliary dynamics are associated with several pathological conditions called ciliopathies. Previous studies showed that the localization of phosphorylated Tctex-1 at Thr94 (T94) at the ciliary base critically regulates ciliary resorption by accelerating actin remodeling and ciliary pocket membrane endocytosis. Here, we show that microtubule-associated serine/threonine kinase family member 4 (MAST4) is localized at the primary cilium. Suppressing MAST4 blocks serum-induced ciliary resorption, and overexpressing MAST4 accelerates ciliary resorption. Tctex-1 binds to the kinase domain of MAST4, in which the R503 and D504 residues are key to MAST4-mediated ciliary resorption. The ciliary resorption and the ciliary base localization of phospho-(T94)Tctex-1 are blocked by the knockdown of MAST4 or the expression of the catalytic-inactive site-directed MAST4 mutants. Moreover, MAST4 is required for Cdc42 activation and Rab5-mediated periciliary membrane endocytosis during ciliary resorption. These results support that MAST4 is a novel kinase that regulates ciliary resorption by modulating the ciliary base localization of phospho-(T94)Tctex-1. MAST4 is a potential new target for treating ciliopathies causally by ciliary resorption defects.
    DOI:  https://doi.org/10.26508/lsa.202301947
  9. Front Physiol. 2023 ;14 1266718
      
    Keywords:  EPAC; PDEs; PKA; PKD; ciliopathy; compartmentalization; polycystic kidney disease; soluble adenylyl cyclase
    DOI:  https://doi.org/10.3389/fphys.2023.1266718
  10. Elife. 2023 Sep 22. pii: RP86689. [Epub ahead of print]12
      The primary cilium plays important roles in regulating cell differentiation, signal transduction, and tissue organization. Dysfunction of the primary cilium can lead to ciliopathies and cancer. The formation and organization of the primary cilium are highly associated with cell polarity proteins, such as the apical polarity protein CRB3. However, the molecular mechanisms by which CRB3 regulates ciliogenesis and the location of CRB3 remain unknown. Here, we show that CRB3, as a navigator, regulates vesicle trafficking in γ-tubulin ring complex (γTuRC) assembly during ciliogenesis and cilium-related Hh and Wnt signaling pathways in tumorigenesis. Crb3 knockout mice display severe defects of the primary cilium in the mammary ductal lumen and renal tubule, while mammary epithelial-specific Crb3 knockout mice exhibit the promotion of ductal epithelial hyperplasia and tumorigenesis. CRB3 is essential for lumen formation and ciliary assembly in the mammary epithelium. We demonstrate that CRB3 localizes to the basal body and that CRB3 trafficking is mediated by Rab11-positive endosomes. Significantly, CRB3 interacts with Rab11 to navigate GCP6/Rab11 trafficking vesicles to CEP290, resulting in intact γTuRC assembly. In addition, CRB3-depleted cells are unresponsive to the activation of the Hh signaling pathway, while CRB3 regulates the Wnt signaling pathway. Therefore, our studies reveal the molecular mechanisms by which CRB3 recognizes Rab11-positive endosomes to facilitate ciliogenesis and regulates cilium-related signaling pathways in tumorigenesis.
    Keywords:  CRB3; Rab11-positive endosome; breast cancer; cell biology; human; mouse; polarity protein; primary cilium; γ-TuRC assembly
    DOI:  https://doi.org/10.7554/eLife.86689
  11. Biomaterials. 2023 Sep 13. pii: S0142-9612(23)00337-X. [Epub ahead of print]302 122329
      Although rapamycin is a very effective drug for rodents with polycystic kidney disease (PKD), it is not encouraging in the clinical trials due to the suboptimal dosages compelled by the off-target side effects. We here report the generation, characterization, specificity, functionality, pharmacokinetic, pharmacodynamic and toxicology profiles of novel polycystic kidney-specific-targeting nanoparticles (NPs). We formulated folate-conjugated PLGA-PEG NPs, which can be loaded with multiple drugs, including rapamycin (an mTOR inhibitor) and antioxidant 4-hydroxy-TEMPO (a nephroprotective agent). The NPs increased the efficacy, potency and tolerability of rapamycin resulting in an increased survival rate and improved kidney function by decreasing side effects and reducing biodistribution to other organs in PKD mice. The daily administration of rapamycin-alone (1 mg/kg/day) could now be achieved with a weekly injection of NPs containing rapamycin (379 μg/kg/week). This polycystic kidney-targeting nanotechnology, for the first time, integrated advances in the use of 1) nanoparticles as a delivery cargo, 2) folate for targeting, 3) near-infrared Cy5-fluorophore for in vitro and in vivo live imaging, 4) rapamycin as a pharmacological therapy, and 5) TEMPO as a combinational therapy. The slow sustained-release of rapamycin by polycystic kidney-targeting NPs demonstrates a new era of nanomedicine in treatment for chronic kidney diseases at clinically relevant doses.
    Keywords:  4-Hydroxy-[2,2,6,6-tetramethylpiperidin-1-yl]oxidanyl; Antioxidant; Folate-conjugated nanoparticles; Polycystic kidney; Rapamycin
    DOI:  https://doi.org/10.1016/j.biomaterials.2023.122329
  12. Front Genet. 2023 ;14 1252873
      Background: Meckel Syndrome (MKS, OMIM #249000) is a rare and fatal autosomal recessive ciliopathy with high clinical and genetic heterogeneity. MKS shows complex allelism with other related ciliopathies such as Joubert Syndrome (JBTS, OMIM #213300). In MKS, the formation and function of the primary cilium is defective, resulting in a multisystem disorder including occipital encephalocele, polycystic kidneys, postaxial polydactyly, liver fibrosis, central nervous system malformations and genital anomalies. This study aimed to analyze the genotype of MKS patients and investigate the correlation between genotype and phenotype. Methods: A nonconsanguineous couple who conceived four times with a fetus affected by multiorgan dysfunction and intrauterine fetal death was studied. Whole exome sequencing (WES) was performed in the proband to identify the potentially pathogenic variant. Sanger sequencing was performed in family members. In silico tools were used to analyse the pathogenicity of the identified variants. cDNA TA-cloning sequencing was performed to validate the effects of intronic variants on mRNA splicing. Quantitative real-time PCR was performed to investigate the effect of the variants on gene expression. Immunofluorescence was performed to observe pathological changes of the primary cilium in kidney tissue from the proband. Results: Two splice site variants of TMEM231 (NM_001077418.2, c.583-1G>C and c.583-2_588delinsTCCTCCC) were identified in the proband, and the two variants have not been previously reported. The parents were confirmed as carriers. The two variants were predicted to be pathogenic by in silico tools and were classified as pathogenic/likely pathogenic variants according to the American College of Medical Genetics and Genomics guideline. cDNA TA cloning analysis showed that both splice site variants caused a deletion of exon 5. RT-PCR revealed that the expression of TMEM231 was significantly decreased and immunofluorescence showed that the primary cilium was almost absent in the proband's kidney tissue. Conclusion: We reported the clinical, genetic, molecular and histochemical characterisation of a family affected by MKS. Our findings not only extended the mutation spectrum of the TMEM231 gene, but also revealed for the first time the pathological aetiology of primary cilia in humans and provide a basis for genetic counselling of the parents to their offspring.
    Keywords:  Meckel Syndrome; TMEM231 gene; alternative transcription; primary cilia; splicing mutation; whole exome sequencing
    DOI:  https://doi.org/10.3389/fgene.2023.1252873