bims-bicyki Biomed News
on Bicaudal-C1 and interactors in cystic kidney disease
Issue of 2021‒05‒09
sixteen papers selected by
Céline Gagnieux
École Polytechnique Fédérale de Lausanne (EPFL)

  1. Biochem Soc Trans. 2021 May 07. pii: BST20200791. [Epub ahead of print]
      Renal ciliopathies are a heterogenous group of inherited disorders leading to an array of phenotypes that include cystic kidney disease and renal interstitial fibrosis leading to progressive chronic kidney disease and end-stage kidney disease. The renal tubules are lined with epithelial cells that possess primary cilia that project into the lumen and act as sensory and signalling organelles. Mutations in genes encoding ciliary proteins involved in the structure and function of primary cilia cause ciliopathy syndromes and affect many organ systems including the kidney. Recognised disease phenotypes associated with primary ciliopathies that have a strong renal component include autosomal dominant and recessive polycystic kidney disease and their various mimics, including atypical polycystic kidney disease and nephronophthisis. The molecular investigation of inherited renal ciliopathies often allows a precise diagnosis to be reached where renal histology and other investigations have been unhelpful and can help in determining kidney prognosis. With increasing molecular insights, it is now apparent that renal ciliopathies form a continuum of clinical phenotypes with disease entities that have been classically described as dominant or recessive at both extremes of the spectrum. Gene-dosage effects, hypomorphic alleles, modifier genes and digenic inheritance further contribute to the genetic complexity of these disorders. This review will focus on recent molecular genetic advances in the renal ciliopathy field with a focus on cystic kidney disease phenotypes and the genotypes that lead to them. We discuss recent novel insights into underlying disease mechanisms of renal ciliopathies that might be amenable to therapeutic intervention.
    Keywords:  atypical cystic kidney disease; autosomal dominant polycystic kidney disease; cilia; cystic kidney disease; nephronophthisis
  2. J Nephrol. 2021 May 08.
      BACKGROUND: Genetic testing of patients with inherited kidney diseases has emerged as a tool of clinical utility by improving the patients' diagnosis, prognosis, surveillance and therapy.METHODS: The present study applied a Next Generation Sequencing (NGS)-based panel, named NephroPlex, testing 115 genes causing renal diseases, to 119 individuals, including 107 probands and 12 relatives. Thirty-five (poly)cystic and 72 non (poly)cystic individuals were enrolled. The latter subgroup of patients included Bardet-Biedl syndrome (BBS) patients, as major components.
    RESULTS: Disease-causing mutations were identified in 51.5 and 40% of polycystic and non-polycystic individuals, respectively. Autosomal dominant polycystic kidney disease (ADPKD) patients with truncating PKD1 variants showed a trend towards a greater slope of the age-estimated glomerular filtration rate (eGFR) regression line than patients with (i) missense variants, (ii) any PKD2 mutations and (iii) no detected mutations, according to previous findings. The analysis of BBS individuals showed a similar frequency of BBS4,9,10 and 12 mutations. Of note, all BBS4-mutated patients harbored the novel c.332+1G>GTT variant, which was absent in public databases, however, in our internal database, an additional heterozygote carrier was found. All BBS4-mutated individuals originated from the same geographical area encompassing the coastal provinces of Naples.
    DISCUSSION: In conclusion, these findings indicate the potential for a genetic panel to provide useful information at both clinical and epidemiological levels.
    Keywords:  ADPKD; Bardet-Biedl syndrome; Gene-panel; Inherited kidney disease; NGS
  3. Cell. 2021 Apr 27. pii: S0092-8674(21)00437-2. [Epub ahead of print]
      Hedgehog pathway components and select G protein-coupled receptors (GPCRs) localize to the primary cilium, an organelle specialized for signal transduction. We investigated whether cells distinguish between ciliary and extraciliary GPCR signaling. To test whether ciliary and extraciliary cyclic AMP (cAMP) convey different information, we engineered optogenetic and chemogenetic tools to control the subcellular site of cAMP generation. Generating equal amounts of ciliary and cytoplasmic cAMP in zebrafish and mammalian cells revealed that ciliary cAMP, but not cytoplasmic cAMP, inhibited Hedgehog signaling. Modeling suggested that the distinct geometries of the cilium and cell body differentially activate local effectors. The search for effectors identified a ciliary pool of protein kinase A (PKA). Blocking the function of ciliary PKA, but not extraciliary PKA, activated Hedgehog signal transduction and reversed the effects of ciliary cAMP. Therefore, cells distinguish ciliary and extraciliary cAMP using functionally and spatially distinct pools of PKA, and different subcellular pools of cAMP convey different information.
    Keywords:  G protein-coupled receptor; Hedgehog signaling; cAMP; chemogenetics; development; optogenetics; primary cilia; protein kinase A; signal transduction
  4. J Clin Invest. 2021 May 03. pii: 142064. [Epub ahead of print]131(9):
      The melanocortin 4 receptor (MC4R) plays a critical role in the long-term regulation of energy homeostasis, and mutations in the MC4R are the most common cause of monogenic obesity. However, the precise molecular and cellular mechanisms underlying the maintenance of energy balance within MC4R-expressing neurons are unknown. We recently reported that the MC4R localizes to the primary cilium, a cellular organelle that allows for partitioning of incoming cellular signals, raising the question of whether the MC4R functions in this organelle. Here, using mouse genetic approaches, we found that cilia were required specifically on MC4R-expressing neurons for the control of energy homeostasis. Moreover, these cilia were critical for pharmacological activators of the MC4R to exert an anorexigenic effect. The MC4R is expressed in multiple brain regions. Using targeted deletion of primary cilia, we found that cilia in the paraventricular nucleus of the hypothalamus (PVN) were essential to restrict food intake. MC4R activation increased adenylyl cyclase (AC) activity. As with the removal of cilia, inhibition of AC activity in the cilia of MC4R-expressing neurons of the PVN caused hyperphagia and obesity. Thus, the MC4R signaled via PVN neuron cilia to control food intake and body weight. We propose that defects in ciliary localization of the MC4R cause obesity in human inherited obesity syndromes and ciliopathies.
    Keywords:  Endocrinology; G protein–coupled receptors; Melanocortin; Metabolism; Obesity
  5. Kidney Int. 2021 Apr 30. pii: S0085-2538(21)00459-2. [Epub ahead of print]
      Autosomal recessive polycystic kidney disease (ARPKD) is a severe disease of early childhood that is clinically characterized by fibrocystic changes of the kidneys and the liver. The main cause of ARPKD are variants in the PKHD1 gene encoding the large transmembrane protein fibrocystin. The mechanisms underlying the observed clinical heterogeneity in ARPKD remain incompletely understood, partly due to the fact that genotype-phenotype correlations have been limited to the association of biallelic null variants in PKHD1 with the most severe phenotypes. In this observational study we analyzed a deep clinical dataset of 304 patients with ARPKD from two independent cohorts and identified novel genotype-phenotype correlations during childhood and adolescence. Biallelic null variants frequently show severe courses. Additionally, our data suggest that the affected region in PKHD1 is important in determining the phenotype. Patients with two missense variants affecting amino acids 709-1837 of fibrocystin or a missense variant in this region and a null variant less frequently developed chronic kidney failure and patients with missense variants affecting amino acids 1838-2624 showed better hepatic outcome. Variants affecting amino acids 2625-4074 of fibrocystin were associated with poorer hepatic outcome. Thus, our data expand the understanding of genotype-phenotype correlations in pediatric ARPKD patients and can lay the foundation for more precise and personalized counselling and treatment approaches.
    Keywords:  PKD; cilia; ciliopathies; fibrocystic hepatorenal disease; fibrocystin; polycystic kidney disease
  6. J Neurosci. 2021 May 07. pii: JN-RM-2456-20. [Epub ahead of print]
      Axon regeneration is an evolutionarily conserved process essential for restoring the function of damaged neurons. In Caenorhabditis elegans hermaphrodites, initiation of axon regeneration is regulated by the RhoA GTPase-ROCK (Rho-associated coiled-coil kinase)-regulatory non-muscle myosin light-chain phosphorylation signaling pathway. However, the upstream mechanism that activates the RhoA pathway remains unknown. Here, we show that axon injury activates TLN-1/talin via the cAMP-Epac (exchange protein directly activated by cAMP)-Rap GTPase cascade and that TLN-1 induces multiple downstream events, one of which is integrin inside-out activation, leading to the activation of the RhoA-ROCK signaling pathway. We found that the non-receptor tyrosine kinase Src, a key mediator of integrin signaling, activates the Rho guanine nucleotide exchange factor (GEF) EPHX-1/ephexin by phosphorylating the Tyr-568 residue in the autoinhibitory domain. Our results suggest that the C. elegans integrin signaling network regulates axon regeneration via the Src-RhoGEF-RhoA axis.Significance StatementThe ability of axons to regenerate after injury is governed by cell-intrinsic regeneration pathways. We have previously demonstrated that the C. elegans RhoA GTPase-ROCK pathway promotes axon regeneration by inducing MLC-4 phosphorylation. In this study, we found that axon injury activates TLN-1/talin through the cAMP-Epac-Rap GTPase cascade, leading to integrin inside-out activation, which promotes axonal regeneration by activating the RhoA signaling pathway. In this pathway, SRC-1/Src acts downstream of integrin activation and subsequently activates EPHX-1/ephexin RhoGEF by phosphorylating the Tyr-568 residue in the autoinhibitory domain. Our results suggest that the C. elegans integrin signaling network regulates axon regeneration via the Src-RhoGEF-RhoA axis.
  7. CEN Case Rep. 2021 May 03.
      The gene encoding hepatocyte nuclear factor 1β (HNF1B), a transcription factor involved in the development of the kidney and other organs, is located on chromosome 17q12. Heterozygous deletions of chromosome 17q12, which involve 15 genes including HNF1B, are known as 17q12 deletion syndrome and are a common cause of congenital anomalies of the kidneys and urinary tract (CAKUT) and may also present as a multisystem disorder. Autosomal recessive polycystic kidney disease (ARPKD), on the other hand, is a severe form of polycystic kidney disease caused by mutations in PKHD1 (polycystic kidney and hepatic disease 1). It is important to differentiate between these two diseases because they differ significantly in inheritance patterns, renal prognosis, and extrarenal manifestations. Here we report a case of 17q12 deletion syndrome that clinically mimicked ARPKD in which genetic testing was essential for appropriate genetic counseling and monitoring of possible extrarenal manifestations. The patient presented antenatally with markedly enlarged kidneys and showed bilaterally hyperechoic kidneys with poor corticomedullary differentiation and multiple cysts on ultrasonography. There was no family history of renal disease. ARPKD was clinically suspected and genetic testing was performed to confirm diagnosis, resulting in an unexpected finding of 17q12 deletion including HNF1B. While some research has been done to identify patients that should be tested for HNF1B anomalies, this case illustrates the difficulty of recognizing HNF1B-related disease and the importance of genetic testing in appropriately managing CAKUT cases.
    Keywords:  17q12 deletion syndrome; Autosomal recessive polycystic kidney disease (ARPKD); Congenital anomalies of the kidneys and urinary tract (CAKUT); Genetic testing; HNF1B-associated disease; Hepatocyte nuclear factor 1β (HNF1B)
  8. J Extracell Vesicles. 2021 Apr;10(6): e12086
      Extracellular vesicles (EVs) are cell-derived membrane vesicles that are released into the extracellular space. EVs encapsulate key proteins and mediate intercellular signalling pathways. Recently, primary cilia have been shown to release EVs under fluid-shear flow, but many proteins encapsulated in these vesicles have never been identified. Primary cilia are ubiquitous mechanosensory organelles that protrude from the apical surface of almost all human cells. Primary cilia also serve as compartments for signalling pathways, and their defects have been associated with a wide range of human genetic diseases called ciliopathies. To better understand the mechanism of ciliopathies, it is imperative to know the distinctive protein profiles of the differently sourced EVs (cilia vs cytosol). Here, we isolated EVs from ciliated wild-type (WT) and non-ciliated IFT88 knockout (KO) mouse endothelial cells using fluid-shear flow followed by a conventional method of EV isolation. EVs isolated from WT and KO exhibited distinctive sizes. Differences in EV protein contents were studied using liquid chromatography with tandem mass spectrometry (LC-MS-MS) and proteomic comparative analysis, which allowed us to classify proteins between ciliary EVs and cytosolic EVs derived from WT and KO, respectively. A total of 79 proteins were exclusively expressed in WT EVs, 145 solely in KO EVs, and 524 in both EVs. Our bioinformatics analyses revealed 29% distinct protein classes and 75% distinct signalling pathways between WT and KO EVs. Based on our statistical analyses and in vitro studies, we identified NADPH-cytochrome P450 reductase (POR), and CD166 antigen (CD166) as potential biomarkers for ciliary and cytosolic EVs, respectively. Our protein-protein interaction network analysis revealed that POR, but not CD166, interacted with either established or strong ciliopathy gene candidates. This report shows the unique differences between EVs secreted from cilia and the cytosol. These results will be important in advancing our understanding of human genetic diseases.
    Keywords:  bioinformatics; ciliary ectosomes; ciliary exosomes; ciliary extracellular vesicles; ciliary protein classes; ciliary vesicle proteome; cytosolic extracellular vesicles; gene ontology; primary cilia; signalling pathways
  9. Aging Cell. 2021 May 07. e13369
      Serotonin 6 receptor (5-HT6R) is a promising target for a variety of human diseases, such as Alzheimer's disease (AD) and schizophrenia. However, the detailed mechanism underlying 5-HT6R activity in the central nervous system (CNS) is not fully understood. In the present study, 5-HT6R null mutant (5-HT6R-/- ) mice were found to exhibit cognitive deficiencies and abnormal anxiety levels. 5-HT6R is considered to be specifically localized on the primary cilia. We found that the loss of 5-HT6R affected the Sonic Hedgehog signaling pathway in the primary cilia. 5-HT6R-/- mice showed remarkable alterations in neuronal morphology, including dendrite complexity and axon initial segment morphology. Neurons lacking 5-HT6R exhibited increased neuronal excitability. Our findings highlight the complexity of 5-HT6R functions in the primary ciliary and neuronal physiology, supporting the theory that this receptor modulates neuronal morphology and transmission, and contributes to cognitive deficits in a variety of human diseases, such as AD, schizophrenia, and ciliopathies.
    Keywords:  5-HT6R; learning and memory; neuronal excitability; primary cilia
  10. J Cardiovasc Pharmacol. 2021 May 05.
      ABSTRACT: Vascular smooth muscle cell (VSMC) dysfunction is the main cause of aortic dissection (AD). In this study, we focused on the role and mechanism of miR-4787-5p in regulating VSMC apoptosis. RT-qPCR was used to detect the expression of miR-4787-5p in aorta tissues of AD (n=10) and normal aortic tissues of donors (n=10). Cell apoptosis was tested by TUNEL assay and Annexin V FITC/PI staining flow cytometry. The expression of PC1 and the PI3K/Akt/FKHR signaling pathway associated proteins in VSMCs was measured by Western blot. We found that the miR-4787-5p was highly expressed in aorta tissues of AD compared with 10 healthy volunteers. Meanwhile, PI3K/Akt/FKHR signaling pathway was inactive in the aortic tissue of AD. The overexpression of miR-4787-5p significantly induced VSMC apoptosis, and miR-4787-5p knockdown showed the opposite results. In addition, polycystic kidney disease 1 gene (PKD1), which encodes polycystin-1(PC1), was found to be a direct target of miR-4787-5p in the VSMCs and this was validated using a luciferase reporter assay. Overexpression of PC1 by LV-PC1 plasmids markedly eliminated the promotion of miR-4787-5p overexpression on VSMC apoptosis. Finally, it was found that miR-4787-5p deactivated the PI3K/Akt/FKHR pathway, as demonstrated by the down-regulation of phosphorylated (p-)PI3K, p-Akt, and p-FKHR. In conclusion, these findings confirm an important role for the miR-4787-5p/PKD1 axis in AD pathobiology.
  11. Front Cell Dev Biol. 2021 ;9 625251
      Background: Nasal inverted papilloma (NIP) is a common benign tumor. Yes-associated protein (YAP) is the core effector molecule of the Hippo pathway, which regulates the proliferation and differentiation of airway epithelium. While its role in proliferation may be connected to NIP formation, no definitive association has been made between them.Methods: We compared the difference of YAP expression and proliferation level between the control inferior turbinate, NP (nasal polyps), and NIP groups. In addition, we further used PCR, immunofluorescence, and immunohistochemistry to investigate YAP's role in the proliferation and differentiation of the nasal epithelium and inflammatory cell infiltration, correlating them with different grades of epithelial remodeling. We further used an IL-13 remodeling condition to investigate YAP's role in differentiation in an in vitro air-liquid interface (ALI) human nasal epithelial cell (hNECs) model. Finally, we also explored the correlation between YAP expression and clinical indicators of NIP.
    Results: The expression of YAP/active YAP in the NIP group was significantly higher than that in the NP group and control group. Moreover, within the NIP group, the higher grade of epithelial remodeling was associated with higher YAP induced proliferation, leading to reduced ciliated cells and goblet cells. The finding was further verified using an IL-13 remodeling condition in differentiating ALI hNECs. Furthermore, YAP expression was positively correlated with proliferation and neutrophil infiltration in NIP. YAP expression was also significantly increased in NIP patients with adverse outcomes.
    Conclusion: Abnormal expression of YAP/active YAP is associated with proliferation, differentiation, neutrophil infiltration, and adverse outcome in NIP and may present a novel target for diagnosis and intervention in NIP.
    Keywords:  differentiation; epithelial cells; nasal inverted papilloma; neutrophils; proliferation; yes-associated protein
  12. Annu Rev Biophys. 2021 May 06. 50 549-574
      Dyneins make up a family of AAA+ motors that move toward the minus end of microtubules. Cytoplasmic dynein is responsible for transporting intracellular cargos in interphase cells and mediating spindle assembly and chromosome positioning during cell division. Other dynein isoforms transport cargos in cilia and power ciliary beating. Dyneins were the least studied of the cytoskeletal motors due to challenges in the reconstitution of active dynein complexes in vitro and the scarcity of high-resolution methods for in-depth structural and biophysical characterization of these motors. These challenges have been recently addressed, and there have been major advances in our understanding of the activation, mechanism, and regulation of dyneins. This review synthesizes the results of structural and biophysical studies for each class of dynein motors. We highlight several outstanding questions about the regulation of bidirectional transport along microtubules and the mechanisms that sustain self-coordinated oscillations within motile cilia.
    Keywords:  axoneme; cilia; dynein; intracellular transport; intraflagellar transport; microtubules
  13. Biochem Soc Trans. 2021 May 07. pii: BST20200833. [Epub ahead of print]
      Centrioles are important cellular organelles involved in the formation of both cilia and centrosomes. It is therefore not surprising that their dysfunction may lead to a variety of human pathologies. Studies have identified a conserved pathway of proteins required for centriole formation, and investigations using the embryo of the fruit fly Drosophila melanogaster have been crucial in elucidating their dynamics. However, a full understanding of how these components interact has been hampered by the total absence of centrioles in null mutant backgrounds for any of these core centriole factors. Here, I review our recent work describing a new model for investigating these interactions in the absence of bona fide centrioles. Sas-6 Ana2 Particles (SAPs) form when two core centriole factors, Sas-6 and Ana2, are co-over-expressed in fruit fly eggs. Crucially, they form even in eggs lacking other core centriole proteins. I review our characterisation of SAPs, and provide one example of how they have been used to investigate the role of a core centriole protein in PCM formation. I then consider some of the strengths and weaknesses of the SAP model, and discuss them in the context of other models for centriole study in Drosophila. Similar aggregates have been seen in other systems upon expression of centriole factors, so SAPs may also be a useful approach to study centriole proteins in other organisms.
    Keywords:   Drosophila melanogaster ; biological models; centrosomes
  14. Front Psychiatry. 2021 ;12 666646
      Midazolam is a benzodiazepine (BZD) mainly used in anesthetic induction due to its pharmacokinetic features. Its place in the therapeutic management of catatonia remains to be determined. Here we present the case of a 65-year-old man who presented with a first episode of catatonia with opposition to any form of oral treatment, where a single dose of 1 mg of subcutaneous (SC) Midazolam permitted clinical improvement allowing oral treatment to be given. The patient's history notably included a renal transplant linked to Polycystic Kidney Disease (PKD) and no history of psychiatric illness nor of any use of psychotropic drugs. As the patient refused to drink or eat and ceased answering basic questions, a psychiatric assessment was required. A diagnosis of Catatonic disorder due to a general medical condition [DSM 5-293.89/ ICD10 [F06.1]] was made. A Bush-Francis Catatonia Rating Scale (BFCRS) analysis returned a score of 15 out of 62, with stupor, mutism, negativism, staring, withdrawal, rigidity, and stereotypy. As the negativism prevented the patient from taking any form of oral treatment, after a brief discussion with the unit's physician, it was decided to administer 1 mg of SC Midazolam. One hour later, the patient was more responsive and compliant, and agreed to drink, eat, and take medication. Thus, the catatonic signs of mutism, negativism, staring, and withdrawal were resolved, but waxy flexibility and catalepsy appeared, leading to a new BFCRS score of 10 out of 62. Oral treatment with 2.5 mg Lorazepam, 4 times a day, was then initiated. Midazolam could be a safer choice compared with the other options available, such as other SC BZD, considering the complex safety profile of this patient with renal insufficiency. This situation represents the first report of using SC Midazolam as an injectable treatment for catatonia. More studies are needed to assess the clinical pertinence of SC Midazolam in the treatment of catatonia.
    Keywords:  benzodiazepine; catatonia; negativism; subcutaenous administration; withdrawal