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Fuentealba LM, Pizarro H, Marzolo MP. OCRL1 Deficiency Affects the Intracellular Traffic of ApoER2 and Impairs Reelin-Induced Responses. Biomolecules 2024; 14:799. [PMID: 39062513 PMCID: PMC11274606 DOI: 10.3390/biom14070799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 07/01/2024] [Accepted: 07/02/2024] [Indexed: 07/28/2024] Open
Abstract
Lowe Syndrome (LS) is a rare X-linked disorder characterized by renal dysfunction, cataracts, and several central nervous system (CNS) anomalies. The mechanisms underlying the neurological dysfunction in LS remain unclear, albeit they share some phenotypic characteristics similar to the deficiency or dysfunction of the Reelin signaling, a relevant pathway with roles in CNS development and neuronal functions. In this study, we investigated the role of OCRL1, an inositol polyphosphate 5-phosphatase encoded by the OCRL gene, mutated in LS, focusing on its impact on endosomal trafficking and receptor recycling in human neuronal cells. Specifically, we tested the effects of OCRL1 deficiency in the trafficking and signaling of ApoER2/LRP8, a receptor for the ligand Reelin. We found that loss of OCRL1 impairs ApoER2 intracellular trafficking, leading to reduced receptor expression and decreased levels at the plasma membrane. Additionally, human neurons deficient in OCRL1 showed impairments in ApoER2/Reelin-induced responses. Our findings highlight the critical role of OCRL1 in regulating ApoER2 endosomal recycling and its impact on the ApoER2/Reelin signaling pathway, providing insights into potential mechanisms underlying the neurological manifestations of LS.
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Affiliation(s)
| | | | - María-Paz Marzolo
- Laboratorio de Tráfico Intracelular y Señalización, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 7810128, Chile; (L.M.F.); (H.P.)
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2
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Bura A, de Matteis MA, Bender M, Swinkels M, Versluis J, Jansen AJG, Jurak Begonja A. Oculocerebrorenal syndrome of Lowe protein controls cytoskeletal reorganisation during human platelet spreading. Br J Haematol 2023; 200:87-99. [PMID: 36176266 DOI: 10.1111/bjh.18478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 09/05/2022] [Accepted: 09/14/2022] [Indexed: 11/28/2022]
Abstract
Lowe syndrome (LS) is a rare, X-linked disorder characterised by numerous symptoms affecting the brain, the eyes, and the kidneys. It is caused by mutations in the oculocerebrorenal syndrome of Lowe (OCRL) protein, a 5-phosphatase localised in different cellular compartments that dephosphorylates phosphatidylinositol-4,5-bisphosphate into phosphatidylinositol-4-monophosphate. Some patients with LS also have bleeding disorders, with normal to low platelet (PLT) count and impaired PLT function. However, the mechanism of PLT dysfunction in patients with LS is not completely understood. The main function of PLTs is to activate upon vessel wall injury and stop the bleeding by clot formation. PLT activation is accompanied by a shape change that is a result of massive cytoskeletal rearrangements. Here, we show that OCRL-inhibited human PLTs do not fully spread, form mostly filopodia, and accumulate actin nodules. These nodules co-localise with ARP2/3 subunit p34, vinculin, and sorting nexin 9. Furthermore, OCRL-inhibited PLTs have a retained microtubular coil with high levels of acetylated tubulin. Also, myosin light chain phosphorylation is decreased upon OCRL inhibition, without impaired degranulation or integrin activation. Taken together, these results suggest that OCRL contributes to cytoskeletal rearrangements during PLT activation that could explain mild bleeding problems in patients with LS.
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Affiliation(s)
- Ana Bura
- Department of Biotechnology, University of Rijeka, Rijeka, Croatia
| | - Maria Antonietta de Matteis
- Telethon Institute of Genetics and Medicine, TIGEM, Pozzuoli, Naples, Italy.,Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | - Markus Bender
- Institute of Experimental Biomedicine, University Hospital Wuerzburg, Rudolf Virchow Center, Wuerzburg, Germany
| | - Maurice Swinkels
- Erasmus MC University Medical Center, Rotterdam, the Netherlands
| | - Jurjen Versluis
- Erasmus MC University Medical Center, Rotterdam, the Netherlands
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Chen C, Hu J, Ling K. The Role of Primary Cilia-Associated Phosphoinositide Signaling in Development. J Dev Biol 2022; 10:51. [PMID: 36547473 PMCID: PMC9785882 DOI: 10.3390/jdb10040051] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 11/22/2022] [Accepted: 11/24/2022] [Indexed: 12/07/2022] Open
Abstract
Primary cilia are microtube-based organelles that extend from the cell surface and function as biochemical and mechanical extracellular signal sensors. Primary cilia coordinate a series of signaling pathways during development. Cilia dysfunction leads to a pleiotropic group of developmental disorders, termed ciliopathy. Phosphoinositides (PIs), a group of signaling phospholipids, play a crucial role in development and tissue homeostasis by regulating membrane trafficking, cytoskeleton reorganization, and organelle identity. Accumulating evidence implicates the involvement of PI species in ciliary defects and ciliopathies. The abundance and localization of PIs in the cell are tightly regulated by the opposing actions of kinases and phosphatases, some of which are recently discovered in the context of primary cilia. Here, we review several cilium-associated PI kinases and phosphatases, including their localization along cilia, function in regulating the ciliary biology under normal conditions, as well as the connection of their disease-associated mutations with ciliopathies.
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Affiliation(s)
- Chuan Chen
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN 55905, USA
| | - Jinghua Hu
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN 55905, USA
| | - Kun Ling
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
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Sena C, Iannello G, Skowronski AA, Dannheim K, Cheung L, Agrawal PB, Hirschhorn JN, Zeitler P, LeDuc CA, Stratigopoulos G, Thaker VV. Endocrine and behavioural features of Lowe syndrome and their potential molecular mechanisms. J Med Genet 2022; 59:1171-1178. [PMID: 35803701 PMCID: PMC10186212 DOI: 10.1136/jmedgenet-2022-108490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 06/11/2022] [Indexed: 01/12/2023]
Abstract
BACKGROUND Lowe syndrome (LS) is an X linked disease caused by pathogenic variants in the OCRL gene that impacts approximately 1 in 500 000 children. Classic features include congenital cataract, cognitive/behavioural impairment and renal tubulopathy. METHODS This study is a retrospective review of clinical features reported by family based survey conducted by Lowe Syndrome Association. Frequency of non-ocular clinical feature(s) of LS and their age of onset was summarised. An LS-specific therapy effectiveness scale was used to assess the response to the administered treatment. Expression of OCRL and relevant neuropeptides was measured in postmortem human brain by qPCR. Gene expression in the mouse brain was determined by reanalysis of publicly available bulk and single cell RNA sequencing. RESULTS A total of 137 individuals (1 female, 89.1% white, median age 14 years (range 0.8-56)) were included in the study. Short stature (height <3rd percentile) was noted in 81% (n=111) individuals, and 15% (n=20) received growth hormone therapy. Undescended testis was reported in 47% (n=64), and median age of onset of puberty was 15 years. Additional features were dental problems (n=77, 56%), bone fractures (n=63, 46%), hypophosphataemia (n=60, 44%), developmental delay and behavioural issues. OCRL is expressed in human and mouse hypothalami, and in hypothalamic cell clusters expressing Ghrh, Sst, Oxt, Pomc and pituitary cells expressing Gh and Prl. CONCLUSIONS There is a wide spectrum of the clinical phenotype of LS. Some of the features may be partly driven by the loss of function of OCRL in the hypothalamus and the pituitary.
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Affiliation(s)
- Cecilia Sena
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA
- Naomi Berrie Diabetes Center, Columbia University Irving Medical Center, New York, New York, USA
| | - Grazia Iannello
- Columbia Stem Cell Initiative, Stem Cell Core, Columbia University Irving Medical Center, New York, New York, USA
| | - Alicja A Skowronski
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA
- Naomi Berrie Diabetes Center, Columbia University Irving Medical Center, New York, New York, USA
| | - Katelyn Dannheim
- Department of Pathology and Laboratory Medicine, Rhode Island and Hasbro Children's Hospitals and the Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA
| | - Leonard Cheung
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Pankaj B Agrawal
- Division of Neonatology, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Joel N Hirschhorn
- Division of Endocrinology, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Phillip Zeitler
- Department of Endocrinology, Children's Hospital Colorado, Aurora, Colorado, USA
| | - Charles A LeDuc
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA
- Naomi Berrie Diabetes Center, Columbia University Irving Medical Center, New York, New York, USA
| | - George Stratigopoulos
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA
- Naomi Berrie Diabetes Center, Columbia University Irving Medical Center, New York, New York, USA
| | - Vidhu V Thaker
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA
- Naomi Berrie Diabetes Center, Columbia University Irving Medical Center, New York, New York, USA
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Sandoval L, Fuentealba LM, Marzolo MP. Participation of OCRL1, and APPL1, in the expression, proteolysis, phosphorylation and endosomal trafficking of megalin: Implications for Lowe Syndrome. Front Cell Dev Biol 2022; 10:911664. [PMID: 36340038 PMCID: PMC9630597 DOI: 10.3389/fcell.2022.911664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 10/10/2022] [Indexed: 11/13/2022] Open
Abstract
Megalin/LRP2 is the primary multiligand receptor for the re-absorption of low molecular weight proteins in the proximal renal tubule. Its function is significantly dependent on its endosomal trafficking. Megalin recycling from endosomal compartments is altered in an X-linked disease called Lowe Syndrome (LS), caused by mutations in the gene encoding for the phosphatidylinositol 5-phosphatase OCRL1. LS patients show increased low-molecular-weight proteins with reduced levels of megalin ectodomain in the urine and accumulation of the receptor in endosomal compartments of the proximal tubule cells. To gain insight into the deregulation of megalin in the LS condition, we silenced OCRL1 in different cell lines to evaluate megalin expression finding that it is post-transcriptionally regulated. As an indication of megalin proteolysis, we detect the ectodomain of the receptor in the culture media. Remarkably, in OCRL1 silenced cells, megalin ectodomain secretion appeared significantly reduced, according to the observation in the urine of LS patients. Besides, the silencing of APPL1, a Rab5 effector associated with OCRL1 in endocytic vesicles, also reduced the presence of megalin’s ectodomain in the culture media. In both silencing conditions, megalin cell surface levels were significantly decreased. Considering that GSK3ß-mediated megalin phosphorylation reduces receptor recycling, we determined that the endosomal distribution of megalin depends on its phosphorylation status and OCRL1 function. As a physiologic regulator of GSK3ß, we focused on insulin signaling that reduces kinase activity. Accordingly, megalin phosphorylation was significantly reduced by insulin in wild-type cells. Moreover, even though in cells with low activity of OCRL1 the insulin response was reduced, the phosphorylation of megalin was significantly decreased and the receptor at the cell surface increased, suggesting a protective role of insulin in a LS cellular model.
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Affiliation(s)
- Lisette Sandoval
- Laboratorio de Tráfico Intracelular y Señalización, Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Luz M. Fuentealba
- Laboratorio de Tráfico Intracelular y Señalización, Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - María-Paz Marzolo
- Laboratorio de Tráfico Intracelular y Señalización, Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
- *Correspondence: María-Paz Marzolo,
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Drosataki E, Maragkou S, Dermitzaki K, Stavrakaki I, Lygerou D, Latsoudis H, Pleros C, Petrakis I, Zaganas I, Stylianou K. Dent-2 disease with a Bartter-like phenotype caused by the Asp631Glu mutation in the OCRL gene. BMC Nephrol 2022; 23:182. [PMID: 35549682 PMCID: PMC9097321 DOI: 10.1186/s12882-022-02812-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 05/04/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Dent disease is an X-linked disorder characterized by low molecular weight proteinuria (LMWP), hypercalciuria, nephrolithiasis and chronic kidney disease (CKD). It is caused by mutations in the chloride voltage-gated channel 5 (CLCN5) gene (Dent disease-1), or in the OCRL gene (Dent disease-2). It is associated with chronic metabolic acidosis; however metabolic alkalosis has rarely been reported. CASE PRESENTATION We present a family with Dent-2 disease and a Bartter-like phenotype. The main clinical problems observed in the proband included a) primary phosphaturia leading to osteomalacia and stunted growth; b) elevated serum calcitriol levels, leading to hypercalcemia, hypercalciuria, nephrolithiasis and nephrocalcinosis; c) severe salt wasting causing hypotension, hyperaldosteronism, hypokalemia and metabolic alkalosis; d) partial nephrogenic diabetes insipidus attributed to hypercalcemia, hypokalemia and nephrocalcinosis; e) albuminuria, LMWP. Phosphorous repletion resulted in abrupt cessation of hypercalciuria and significant improvement of hypophosphatemia, physical stamina and bone histology. Years later, he presented progressive CKD with nephrotic range proteinuria attributed to focal segmental glomerulosclerosis (FSGS). Targeted genetic analysis for several phosphaturic diseases was unsuccessful. Whole Exome Sequencing (WES) revealed a c.1893C > A variant (Asp631Glu) in the OCRL gene which was co-segregated with the disease in male family members. CONCLUSIONS We present the clinical characteristics of the Asp631Glu mutation in the OCRL gene, presenting as Dent-2 disease with Bartter-like features. Phosphorous repletion resulted in significant improvement of all clinical features except for progressive CKD. Angiotensin blockade improved proteinuria and stabilized kidney function for several years.
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Affiliation(s)
- Eleni Drosataki
- Nephrology Department, Heraklion University Hospital, Voutes, 71500, Heraklion, Crete, Greece
| | - Sevasti Maragkou
- Nephrology Department, Heraklion University Hospital, Voutes, 71500, Heraklion, Crete, Greece
| | - Kleio Dermitzaki
- Nephrology Department, Heraklion University Hospital, Voutes, 71500, Heraklion, Crete, Greece
| | - Ioanna Stavrakaki
- Nephrology Department, Heraklion University Hospital, Voutes, 71500, Heraklion, Crete, Greece
| | - Dimitra Lygerou
- Nephrology Department, Heraklion University Hospital, Voutes, 71500, Heraklion, Crete, Greece
| | - Helen Latsoudis
- Foundation for Research and Technology - Hellas, Heraklion, Crete, Greece
| | - Christos Pleros
- Nephrology Department, Heraklion University Hospital, Voutes, 71500, Heraklion, Crete, Greece
| | - Ioannis Petrakis
- Department of Nephrology, Saarland University Medical Center, Homburg, Germany
| | - Ioannis Zaganas
- Neurogenetics Laboratory Medical School, University of Crete, Heraklion, Greece
| | - Kostas Stylianou
- Nephrology Department, Heraklion University Hospital, Voutes, 71500, Heraklion, Crete, Greece.
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7
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Ramadesikan S, Lee J, Aguilar RC. The Future of Genetic Disease Studies: Assembling an Updated Multidisciplinary Toolbox. Front Cell Dev Biol 2022; 10:886448. [PMID: 35573700 PMCID: PMC9096115 DOI: 10.3389/fcell.2022.886448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 04/04/2022] [Indexed: 11/20/2022] Open
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8
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Kozyraki R, Verroust P, Cases O. Cubilin, the intrinsic factor-vitamin B12 receptor. VITAMINS AND HORMONES 2022; 119:65-119. [PMID: 35337634 DOI: 10.1016/bs.vh.2022.01.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Cubilin (CUBN), the intrinsic factor-vitamin B12 receptor is a large endocytic protein involved in various physiological functions: vitamin B12 uptake in the gut; reabsorption of albumin and maturation of vitamin D in the kidney; nutrient delivery during embryonic development. Cubilin is an atypical receptor, peripherally associated to the plasma membrane. The transmembrane proteins amnionless (AMN) and Lrp2/Megalin are the currently known molecular partners contributing to plasma membrane transport and internalization of Cubilin. The role of Cubilin/Amn complex in the handling of vitamin B12 in health and disease has extensively been studied and so is the role of the Cubilin-Lrp2 tandem in renal pathophysiology. Accumulating evidence strongly supports a role of Cubilin in some developmental defects including impaired closure of the neural tube. Are these defects primarily caused by the dysfunction of a specific Cubilin ligand or are they secondary to impaired vitamin B12 or protein uptake? We will present the established Cubilin functions, discuss the developmental data and provide an overview of the emerging implications of Cubilin in the field of cardiovascular disease and cancer pathogenesis.
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Affiliation(s)
- Renata Kozyraki
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, Paris, France.
| | - Pierre Verroust
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, Paris, France
| | - Olivier Cases
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, Paris, France
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9
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Oltrabella F, Jackson-Crawford A, Yan G, Rixham S, Starborg T, Lowe M. IPIP27A cooperates with OCRL to support endocytic traffic in the zebrafish pronephric tubule. Hum Mol Genet 2021; 31:1183-1196. [PMID: 34673953 DOI: 10.1093/hmg/ddab307] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 10/12/2021] [Accepted: 10/14/2021] [Indexed: 01/08/2023] Open
Abstract
Endocytosis is a fundamentally important process through which material is internalized into cells from the extracellular environment. In the renal proximal tubule, endocytosis of the abundant scavenger receptor megalin and its co-receptor cubilin play a vital role in retrieving low molecular weight proteins from the renal filtrate. Although we know much about megalin and its ligands, the machinery and mechanisms by which the receptor is trafficked through the endosomal system remain poorly defined. In this study, we show that Ipip27A, an interacting partner of the Lowe syndrome protein OCRL, is required for endocytic traffic of megalin within the proximal renal tubule of zebrafish larvae. Knockout of Ipip27A phenocopies the endocytic phenotype seen upon loss of OCRL, with a deficit in uptake of both fluid-phase and protein cargo, which is accompanied by a reduction in megalin abundance and altered endosome morphology. Rescue and co-depletion experiments indicate that Ipip27A functions together with OCRL to support proximal tubule endocytosis. The results therefore identify Ipip27A as a new player in endocytic traffic in the proximal tubule in vivo and support the view that defective endocytosis underlies the renal tubulopathy in Lowe syndrome and Dent-2 disease.
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Affiliation(s)
- Francesca Oltrabella
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK.,Medical Scientific Liaison - Nephrology, Astellas Pharma, Via Dante, 20123 Milano, Italy
| | - Anthony Jackson-Crawford
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK.,Department of Blood Sciences, Grange University Hospital, Llanyravon, Gwent, NP44 8YN
| | - Guanhua Yan
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
| | - Sarah Rixham
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
| | - Tobias Starborg
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK.,Rosalind Franklin Institute, Harwell Campus, Didcot, OX11 0FA, UK
| | - Martin Lowe
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
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10
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Gianesello L, Arroyo J, Del Prete D, Priante G, Ceol M, Harris PC, Lieske JC, Anglani F. Genotype Phenotype Correlation in Dent Disease 2 and Review of the Literature: OCRL Gene Pleiotropism or Extreme Phenotypic Variability of Lowe Syndrome? Genes (Basel) 2021; 12:1597. [PMID: 34680992 PMCID: PMC8535715 DOI: 10.3390/genes12101597] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/30/2021] [Accepted: 10/05/2021] [Indexed: 11/29/2022] Open
Abstract
Dent disease is a rare X-linked renal tubulopathy due to CLCN5 and OCRL (DD2) mutations. OCRL mutations also cause Lowe syndrome (LS) involving the eyes, brain and kidney. DD2 is frequently described as a mild form of LS because some patients may present with extra-renal symptoms (ESs). Since DD2 is a rare disease and there are a low number of reported cases, it is still unclear whether it has a clinical picture distinct from LS. We retrospectively analyzed the phenotype and genotype of our cohort of 35 DD2 males and reviewed all published DD2 cases. We analyzed the distribution of mutations along the OCRL gene and evaluated the type and frequency of ES according to the type of mutation and localization in OCRL protein domains. The frequency of patients with at least one ES was 39%. Muscle findings are the most common ES (52%), while ocular findings are less common (11%). Analysis of the distribution of mutations revealed (1) truncating mutations map in the PH and linker domain, while missense mutations map in the 5-phosphatase domain, and only occasionally in the ASH-RhoGAP module; (2) five OCRL mutations cause both DD2 and LS phenotypes; (3) codon 318 is a DD2 mutational hot spot; (4) a correlation was found between the presence of ES and the position of the mutations along OCRL domains. DD2 is distinct from LS. The mutation site and the mutation type largely determine the DD2 phenotype.
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Affiliation(s)
- Lisa Gianesello
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology, Dialysis and Transplantation Unit, Department of Medicine-DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (D.D.P.); (G.P.); (M.C.)
| | - Jennifer Arroyo
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN 55905, USA; (J.A.); (P.C.H.); (J.C.L.)
| | - Dorella Del Prete
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology, Dialysis and Transplantation Unit, Department of Medicine-DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (D.D.P.); (G.P.); (M.C.)
| | - Giovanna Priante
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology, Dialysis and Transplantation Unit, Department of Medicine-DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (D.D.P.); (G.P.); (M.C.)
| | - Monica Ceol
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology, Dialysis and Transplantation Unit, Department of Medicine-DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (D.D.P.); (G.P.); (M.C.)
| | - Peter C. Harris
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN 55905, USA; (J.A.); (P.C.H.); (J.C.L.)
| | - John C. Lieske
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN 55905, USA; (J.A.); (P.C.H.); (J.C.L.)
| | - Franca Anglani
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology, Dialysis and Transplantation Unit, Department of Medicine-DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (D.D.P.); (G.P.); (M.C.)
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11
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Weisz OA. Targeting PIs to improve PTs:a new approach to treating genetic diseases of the proximal tubule. Kidney Int 2021; 98:824-826. [PMID: 32998810 DOI: 10.1016/j.kint.2020.06.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/03/2020] [Accepted: 06/05/2020] [Indexed: 11/15/2022]
Abstract
Defective recycling of megalin consequent to impaired phosphatidylinositol metabolism has been implicated as a mechanism causing tubular proteinuria in patients with Lowe syndrome. In this issue, Berquez et al. describe an innovative approach using a clinically approved drug to "rebalance" phosphatidylinositols and restore megalin traffic in mouse and cell models of the disease.
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Affiliation(s)
- Ora A Weisz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
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12
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A 3D Renal Proximal Tubule on Chip Model Phenocopies Lowe Syndrome and Dent II Disease Tubulopathy. Int J Mol Sci 2021; 22:ijms22105361. [PMID: 34069732 PMCID: PMC8161077 DOI: 10.3390/ijms22105361] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 05/14/2021] [Accepted: 05/18/2021] [Indexed: 12/28/2022] Open
Abstract
Lowe syndrome and Dent II disease are X-linked monogenetic diseases characterised by a renal reabsorption defect in the proximal tubules and caused by mutations in the OCRL gene, which codes for an inositol-5-phosphatase. The life expectancy of patients suffering from Lowe syndrome is largely reduced because of the development of chronic kidney disease and related complications. There is a need for physiological human in vitro models for Lowe syndrome/Dent II disease to study the underpinning disease mechanisms and to identify and characterise potential drugs and drug targets. Here, we describe a proximal tubule organ on chip model combining a 3D tubule architecture with fluid flow shear stress that phenocopies hallmarks of Lowe syndrome/Dent II disease. We demonstrate the high suitability of our in vitro model for drug target validation. Furthermore, using this model, we demonstrate that proximal tubule cells lacking OCRL expression upregulate markers typical for epithelial–mesenchymal transition (EMT), including the transcription factor SNAI2/Slug, and show increased collagen expression and deposition, which potentially contributes to interstitial fibrosis and disease progression as observed in Lowe syndrome and Dent II disease.
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13
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Wang B, He W, Prosseda PP, Li L, Kowal TJ, Alvarado JA, Wang Q, Hu Y, Sun Y. OCRL regulates lysosome positioning and mTORC1 activity through SSX2IP-mediated microtubule anchoring. EMBO Rep 2021; 22:e52173. [PMID: 33987909 DOI: 10.15252/embr.202052173] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 03/18/2021] [Accepted: 04/08/2021] [Indexed: 11/09/2022] Open
Abstract
Lysosomal positioning and mTOR (mammalian target of rapamycin) signaling coordinate cellular responses to nutrient levels. Inadequate nutrient sensing can result in growth delays, a hallmark of Lowe syndrome. OCRL mutations cause Lowe syndrome, but the role of OCRL in nutrient sensing is unknown. Here, we show that OCRL is localized to the centrosome by its ASH domain and that it recruits microtubule-anchoring factor SSX2IP to the centrosome, which is important in the formation of the microtubule-organizing center. Deficiency of OCRL in human and mouse cells results in loss of microtubule-organizing centers and impaired microtubule-based lysosome movement, which in turn leads to mTORC1 inactivation and abnormal nutrient sensing. Centrosome-targeted PACT-SSX2IP can restore microtubule anchoring and mTOR activity. Importantly, boosting the activity of mTORC1 restores the nutrient sensing ability of Lowe patients' cells. Our findings highlight mTORC1 as a novel therapeutic target for Lowe syndrome.
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Affiliation(s)
- Biao Wang
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Wei He
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Philipp P Prosseda
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Liang Li
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Tia J Kowal
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Jorge A Alvarado
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Qing Wang
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Yang Hu
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Yang Sun
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA.,Palo Alto Veterans Administration, Palo Alto, CA, USA
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14
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Festa BP, Berquez M, Nieri D, Luciani A. Endolysosomal Disorders Affecting the Proximal Tubule of the Kidney: New Mechanistic Insights and Therapeutics. Rev Physiol Biochem Pharmacol 2021; 185:233-257. [PMID: 33649992 DOI: 10.1007/112_2020_57] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Epithelial cells that line the proximal tubule of the kidney rely on an intertwined ecosystem of vesicular membrane trafficking pathways to ensure the reabsorption of essential nutrients. To function effectively and to achieve homeostasis, these specialized cells require the sorting and recycling of a wide array of cell surface proteins within the endolysosomal network, including signaling receptors, nutrient transporters, ion channels, and polarity markers. The dysregulation of the endolysosomal system can lead to a generalized proximal tubule dysfunction, ultimately causing severe metabolic complications and kidney disease.In this chapter, we highlight the biological functions of the genes that code endolysosomal proteins from the perspective of understanding - and potentially reversing - the pathophysiology of endolysosomal disorders affecting the proximal tubule of the kidney. These insights might ultimately lead to potential treatments for currently intractable diseases and transform our ability to regulate kidney homeostasis and health.
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Affiliation(s)
- Beatrice Paola Festa
- Institute of Physiology, Mechanisms of Inherited Kidney Disorders Group, University of Zurich, Zurich, Switzerland
| | - Marine Berquez
- Institute of Physiology, Mechanisms of Inherited Kidney Disorders Group, University of Zurich, Zurich, Switzerland
| | - Daniela Nieri
- Institute of Physiology, Mechanisms of Inherited Kidney Disorders Group, University of Zurich, Zurich, Switzerland
| | - Alessandro Luciani
- Institute of Physiology, Mechanisms of Inherited Kidney Disorders Group, University of Zurich, Zurich, Switzerland.
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15
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Berquez M, Gadsby JR, Festa BP, Butler R, Jackson SP, Berno V, Luciani A, Devuyst O, Gallop JL. The phosphoinositide 3-kinase inhibitor alpelisib restores actin organization and improves proximal tubule dysfunction in vitro and in a mouse model of Lowe syndrome and Dent disease. Kidney Int 2020; 98:883-896. [PMID: 32919786 PMCID: PMC7550850 DOI: 10.1016/j.kint.2020.05.040] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 05/01/2020] [Accepted: 05/15/2020] [Indexed: 12/19/2022]
Abstract
Loss-of-function mutations in the OCRL gene, which encodes the phosphatidylinositol [PI] 4,5-bisphosphate [PI(4,5)P2] 5-phosphatase OCRL, cause defective endocytosis and proximal tubule dysfunction in Lowe syndrome and Dent disease 2. The defect is due to increased levels of PI(4,5)P2 and aberrant actin polymerization, blocking endosomal trafficking. PI 3-phosphate [PI(3)P] has been recently identified as a coactivator with PI(4,5)P2 in the actin pathway. Here, we tested the hypothesis that phosphoinositide 3-kinase (PI3K) inhibitors may rescue the endocytic defect imparted by OCRL loss, by rebalancing phosphoinositide signals to the actin machinery. The broad-range PI3K inhibitor copanlisib and class IA p110α PI3K inhibitor alpelisib reduced aberrant actin polymerization in OCRL-deficient human kidney cells in vitro. Levels of PI 3,4,5-trisphosphate, PI(4,5)P2 and PI(3)P were all reduced with alpelisib treatment, and siRNA knockdown of the PI3K catalytic subunit p110α phenocopied the actin phenotype. In a humanized OcrlY/- mouse model, alpelisib reduced endosomal actin staining while restoring stress fiber architecture and levels of megalin at the plasma membrane of proximal tubule cells, reflected by improved endocytic uptake of low molecular weight proteins in vivo. Thus, our findings support the link between phosphoinositide lipids, actin polymerization and endocytic trafficking in the proximal tubule and represent a proof-of-concept for repurposing alpelisib in Lowe syndrome/Dent disease 2.
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Affiliation(s)
- Marine Berquez
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Jonathan R Gadsby
- Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | | | - Richard Butler
- Gurdon Institute, University of Cambridge, Cambridge, UK
| | - Stephen P Jackson
- Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Valeria Berno
- Experimental Imaging Center, ALEMBIC, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | | | - Olivier Devuyst
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
| | - Jennifer L Gallop
- Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK.
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16
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Conduit SE, Vanhaesebroeck B. Phosphoinositide lipids in primary cilia biology. Biochem J 2020; 477:3541-3565. [PMID: 32970140 PMCID: PMC7518857 DOI: 10.1042/bcj20200277] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/30/2020] [Accepted: 08/27/2020] [Indexed: 12/11/2022]
Abstract
Primary cilia are solitary signalling organelles projecting from the surface of most cell types. Although the ciliary membrane is continuous with the plasma membrane it exhibits a unique phospholipid composition, a feature essential for normal cilia formation and function. Recent studies have illustrated that distinct phosphoinositide lipid species localise to specific cilia subdomains, and have begun to build a 'phosphoinositide map' of the cilium. The abundance and localisation of phosphoinositides are tightly regulated by the opposing actions of lipid kinases and lipid phosphatases that have also been recently discovered at cilia. The critical role of phosphoinositides in cilia biology is highlighted by the devastating consequences of genetic defects in cilia-associated phosphoinositide regulatory enzymes leading to ciliopathy phenotypes in humans and experimental mouse and zebrafish models. Here we provide a general introduction to primary cilia and the roles phosphoinositides play in cilia biology. In addition to increasing our understanding of fundamental cilia biology, this rapidly expanding field may inform novel approaches to treat ciliopathy syndromes caused by deregulated phosphoinositide metabolism.
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Affiliation(s)
- Sarah E. Conduit
- UCL Cancer Institute, University College London, 72 Huntley Street, London WC1E 6BT, U.K
| | - Bart Vanhaesebroeck
- UCL Cancer Institute, University College London, 72 Huntley Street, London WC1E 6BT, U.K
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17
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Gianesello L, Del Prete D, Anglani F, Calò LA. Genetics and phenotypic heterogeneity of Dent disease: the dark side of the moon. Hum Genet 2020; 140:401-421. [PMID: 32860533 PMCID: PMC7889681 DOI: 10.1007/s00439-020-02219-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 08/20/2020] [Indexed: 12/18/2022]
Abstract
Dent disease is a rare genetic proximal tubulopathy which is under-recognized. Its phenotypic heterogeneity has led to several different classifications of the same disorder, but it is now widely accepted that the triad of symptoms low-molecular-weight proteinuria, hypercalciuria and nephrocalcinosis/nephrolithiasis are pathognomonic of Dent disease. Although mutations on the CLCN5 and OCRL genes are known to cause Dent disease, no such mutations are found in about 25–35% of cases, making diagnosis more challenging. This review outlines current knowledge regarding Dent disease from another perspective. Starting from the history of Dent disease, and reviewing the clinical details of patients with and without a genetic characterization, we discuss the phenotypic and genetic heterogeneity that typifies this disease. We focus particularly on all those confounding clinical signs and symptoms that can lead to a misdiagnosis. We also try to shed light on a concealed aspect of Dent disease. Although it is a proximal tubulopathy, its misdiagnosis may lead to patients undergoing kidney biopsy. In fact, some individuals with Dent disease have high-grade proteinuria, with or without hematuria, as in the clinical setting of glomerulopathy, or chronic kidney disease of uncertain origin. Although glomerular damage is frequently documented in Dent disease patients’ biopsies, there is currently no reliable evidence of renal biopsy being of either diagnostic or prognostic value. We review published histopathology reports of tubular and glomerular damage in these patients, and discuss current knowledge regarding the role of CLCN5 and OCRL genes in glomerular function.
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Affiliation(s)
- Lisa Gianesello
- Nephrology, Dialysis and Transplantation Unit, Kidney Histomorphology and Molecular Biology Laboratory, Department of Medicine-DIMED, University of Padua, Via Giustiniani n° 2, 35128, Padua, Italy
| | - Dorella Del Prete
- Nephrology, Dialysis and Transplantation Unit, Kidney Histomorphology and Molecular Biology Laboratory, Department of Medicine-DIMED, University of Padua, Via Giustiniani n° 2, 35128, Padua, Italy
| | - Franca Anglani
- Nephrology, Dialysis and Transplantation Unit, Kidney Histomorphology and Molecular Biology Laboratory, Department of Medicine-DIMED, University of Padua, Via Giustiniani n° 2, 35128, Padua, Italy.
| | - Lorenzo A Calò
- Nephrology, Dialysis and Transplantation Unit, Kidney Histomorphology and Molecular Biology Laboratory, Department of Medicine-DIMED, University of Padua, Via Giustiniani n° 2, 35128, Padua, Italy
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18
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Liu H, Barnes J, Pedrosa E, Herman NS, Salas F, Wang P, Zheng D, Lachman HM. Transcriptome analysis of neural progenitor cells derived from Lowe syndrome induced pluripotent stem cells: identification of candidate genes for the neurodevelopmental and eye manifestations. J Neurodev Disord 2020; 12:14. [PMID: 32393163 PMCID: PMC7212686 DOI: 10.1186/s11689-020-09317-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 04/28/2020] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Lowe syndrome (LS) is caused by loss-of-function mutations in the X-linked gene OCRL, which codes for an inositol polyphosphate 5-phosphatase that plays a key role in endosome recycling, clathrin-coated pit formation, and actin polymerization. It is characterized by congenital cataracts, intellectual and developmental disability, and renal proximal tubular dysfunction. Patients are also at high risk for developing glaucoma and seizures. We recently developed induced pluripotent stem cell (iPSC) lines from three patients with LS who have hypomorphic variants affecting the 3' end of the gene, and their neurotypical brothers to serve as controls. METHODS In this study, we used RNA sequencing (RNA-seq) to obtain transcriptome profiles in LS and control neural progenitor cells (NPCs). RESULTS In a comparison of the patient and control NPCs (n = 3), we found 16 differentially expressed genes (DEGs) at the multiple test adjusted p value (padj) < 0.1, with nine at padj < 0.05. Using nominal p value < 0.05, 319 DEGs were detected. The relatively small number of DEGs could be due to the fact that OCRL is not a transcription factor per se, although it could have secondary effects on gene expression through several different mechanisms. Although the number of DEGs passing multiple test correction was small, those that were found are quite consistent with some of the known molecular effects of OCRL protein, and the clinical manifestations of LS. Furthermore, using gene set enrichment analysis (GSEA), we found that genes increased expression in the patient NPCs showed enrichments of several gene ontology (GO) terms (false discovery rate < 0.25): telencephalon development, pallium development, NPC proliferation, and cortex development, which are consistent with a condition characterized by intellectual disabilities and psychiatric manifestations. In addition, a significant enrichment among the nominal DEGs for genes implicated in autism spectrum disorder (ASD) was found (e.g., AFF2, DNER, DPP6, DPP10, RELN, CACNA1C), as well as several that are strong candidate genes for the development of eye problems found in LS, including glaucoma. The most notable example is EFEMP1, a well-known candidate gene for glaucoma and other eye pathologies. CONCLUSION Overall, the RNA-seq findings present several candidate genes that could help explain the underlying basis for the neurodevelopmental and eye problems seen in boys with LS.
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Affiliation(s)
- Hequn Liu
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Jesse Barnes
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Erika Pedrosa
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Nathaniel S. Herman
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Franklin Salas
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Ping Wang
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Deyou Zheng
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, USA
- Dominick P Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
- Department of Neurology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Herbert M. Lachman
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, USA
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, Bronx, New York, USA
- Dominick P Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA
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19
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Prosseda PP, Alvarado JA, Wang B, Kowal TJ, Ning K, Stamer WD, Hu Y, Sun Y. Optogenetic stimulation of phosphoinositides reveals a critical role of primary cilia in eye pressure regulation. SCIENCE ADVANCES 2020; 6:eaay8699. [PMID: 32494665 PMCID: PMC7190330 DOI: 10.1126/sciadv.aay8699] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 02/11/2020] [Indexed: 05/10/2023]
Abstract
Glaucoma is a group of progressive optic neuropathies that cause irreversible vision loss. Although elevated intraocular pressure (IOP) is associated with the development and progression of glaucoma, the mechanisms for its regulation are not well understood. Here, we have designed CIBN/CRY2-based optogenetic constructs to study phosphoinositide regulation within distinct subcellular compartments. We show that stimulation of CRY2-OCRL, an inositol 5-phosphatase, increases aqueous humor outflow and lowers IOP in vivo, which is caused by a calcium-dependent actin rearrangement of the trabecular meshwork cells. Phosphoinositide stimulation also rescues defective aqueous outflow and IOP in a Lowe syndrome mouse model but not in IFT88fl/fl mice that lack functional cilia. Thus, our study is the first to use optogenetics to regulate eye pressure and demonstrate that tight regulation of phosphoinositides is critical for aqueous humor homeostasis in both normal and diseased eyes.
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Affiliation(s)
- Philipp P. Prosseda
- Department of Ophthalmology, Stanford University School of Medicine, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94305, USA
| | - Jorge A. Alvarado
- Department of Ophthalmology, Stanford University School of Medicine, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94305, USA
| | - Biao Wang
- Department of Ophthalmology, Stanford University School of Medicine, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94305, USA
| | - Tia J. Kowal
- Department of Ophthalmology, Stanford University School of Medicine, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94305, USA
| | - Ke Ning
- Department of Ophthalmology, Stanford University School of Medicine, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94305, USA
| | - W. Daniel Stamer
- Duke Eye Center, Department of Ophthalmology, Duke University, Durham, NC 27710, USA
| | - Yang Hu
- Department of Ophthalmology, Stanford University School of Medicine, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94305, USA
| | - Yang Sun
- Department of Ophthalmology, Stanford University School of Medicine, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94305, USA
- Palo Alto Veterans Administration, Palo Alto, CA 94304, USA
- Corresponding author.
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20
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Rho GTPase Regulators and Effectors in Autism Spectrum Disorders: Animal Models and Insights for Therapeutics. Cells 2020; 9:cells9040835. [PMID: 32244264 PMCID: PMC7226772 DOI: 10.3390/cells9040835] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 03/22/2020] [Accepted: 03/26/2020] [Indexed: 12/18/2022] Open
Abstract
The Rho family GTPases are small G proteins that act as molecular switches shuttling between active and inactive forms. Rho GTPases are regulated by two classes of regulatory proteins, guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Rho GTPases transduce the upstream signals to downstream effectors, thus regulating diverse cellular processes, such as growth, migration, adhesion, and differentiation. In particular, Rho GTPases play essential roles in regulating neuronal morphology and function. Recent evidence suggests that dysfunction of Rho GTPase signaling contributes substantially to the pathogenesis of autism spectrum disorder (ASD). It has been found that 20 genes encoding Rho GTPase regulators and effectors are listed as ASD risk genes by Simons foundation autism research initiative (SFARI). This review summarizes the clinical evidence, protein structure, and protein expression pattern of these 20 genes. Moreover, ASD-related behavioral phenotypes in animal models of these genes are reviewed, and the therapeutic approaches that show successful treatment effects in these animal models are discussed.
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21
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Festa BP, Berquez M, Gassama A, Amrein I, Ismail HM, Samardzija M, Staiano L, Luciani A, Grimm C, Nussbaum RL, De Matteis MA, Dorchies OM, Scapozza L, Wolfer DP, Devuyst O. OCRL deficiency impairs endolysosomal function in a humanized mouse model for Lowe syndrome and Dent disease. Hum Mol Genet 2020; 28:1931-1946. [PMID: 30590522 PMCID: PMC6548226 DOI: 10.1093/hmg/ddy449] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 12/09/2018] [Accepted: 12/20/2018] [Indexed: 11/29/2022] Open
Abstract
Mutations in OCRL encoding the inositol polyphosphate 5-phosphatase OCRL (Lowe oculocerebrorenal syndrome protein) disrupt phosphoinositide homeostasis along the endolysosomal pathway causing dysfunction of the cells lining the kidney proximal tubule (PT). The dysfunction can be isolated (Dent disease 2) or associated with congenital cataracts, central hypotonia and intellectual disability (Lowe syndrome). The mechanistic understanding of Dent disease 2/Lowe syndrome remains scarce due to limitations of animal models of OCRL deficiency. Here, we investigate the role of OCRL in Dent disease 2/Lowe syndrome by using OcrlY/− mice, where the lethal deletion of the paralogue Inpp5b was rescued by human INPP5B insertion, and primary culture of proximal tubule cells (mPTCs) derived from OcrlY/− kidneys. The OcrlY/− mice show muscular defects with dysfunctional locomotricity and present massive urinary losses of low-molecular-weight proteins and albumin, caused by selective impairment of receptor-mediated endocytosis in PT cells. The latter was due to accumulation of phosphatidylinositol 4,5–bisphosphate PI(4,5)P2 in endolysosomes, driving local hyper-polymerization of F-actin and impairing trafficking of the endocytic LRP2 receptor, as evidenced in OcrlY/− mPTCs. The OCRL deficiency was also associated with a disruption of the lysosomal dynamic and proteolytic activity. Partial convergence of disease-pathways and renal phenotypes observed in OcrlY/− and Clcn5Y/− mice suggest shared mechanisms in Dent diseases 1 and 2. These studies substantiate the first mouse model of Lowe syndrome and give insights into the role of OCRL in cellular trafficking of multiligand receptors. These insights open new avenues for therapeutic interventions in Lowe syndrome and Dent disease.
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Affiliation(s)
| | - Marine Berquez
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Alkaly Gassama
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Irmgard Amrein
- Division of Functional Neuroanatomy, Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Department of Health Sciences and Technology, ETH Zurich, Institute of Human Movement Sciences and Sport, Zurich, Switzerland.,Neuroscience Center Zurich, University of Zurich, Zurich, Switzerland
| | - Hesham M Ismail
- School of Pharmaceutical Sciences, University of Geneva, Rue Michel-Servet 1, Geneva, Switzerland
| | - Marijana Samardzija
- Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Leopoldo Staiano
- Telethon Institute of Genetics and Medicine, Pozzuoli, Naples, Italy
| | | | - Christian Grimm
- Neuroscience Center Zurich, University of Zurich, Zurich, Switzerland.,Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Robert L Nussbaum
- Department of Medicine and Institute of Human Genetics, University of California, San Francisco, CA, USA.,Invitae Corporation, San Francisco, CA, USA
| | | | - Olivier M Dorchies
- School of Pharmaceutical Sciences, University of Geneva, Rue Michel-Servet 1, Geneva, Switzerland
| | - Leonardo Scapozza
- School of Pharmaceutical Sciences, University of Geneva, Rue Michel-Servet 1, Geneva, Switzerland
| | - David Paul Wolfer
- Division of Functional Neuroanatomy, Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Department of Health Sciences and Technology, ETH Zurich, Institute of Human Movement Sciences and Sport, Zurich, Switzerland.,Neuroscience Center Zurich, University of Zurich, Zurich, Switzerland
| | - Olivier Devuyst
- Institute of Physiology, University of Zurich, Zurich, Switzerland
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22
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Gliozzi ML, Espiritu EB, Shipman KE, Rbaibi Y, Long KR, Roy N, Duncan AW, Lazzara MJ, Hukriede NA, Baty CJ, Weisz OA. Effects of Proximal Tubule Shortening on Protein Excretion in a Lowe Syndrome Model. J Am Soc Nephrol 2019; 31:67-83. [PMID: 31676724 DOI: 10.1681/asn.2019020125] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 09/24/2019] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND Lowe syndrome (LS) is an X-linked recessive disorder caused by mutations in OCRL, which encodes the enzyme OCRL. Symptoms of LS include proximal tubule (PT) dysfunction typically characterized by low molecular weight proteinuria, renal tubular acidosis (RTA), aminoaciduria, and hypercalciuria. How mutant OCRL causes these symptoms isn't clear. METHODS We examined the effect of deleting OCRL on endocytic traffic and cell division in newly created human PT CRISPR/Cas9 OCRL knockout cells, multiple PT cell lines treated with OCRL-targeting siRNA, and in orcl-mutant zebrafish. RESULTS OCRL-depleted human cells proliferated more slowly and about 10% of them were multinucleated compared with fewer than 2% of matched control cells. Heterologous expression of wild-type, but not phosphatase-deficient, OCRL prevented the accumulation of multinucleated cells after acute knockdown of OCRL but could not rescue the phenotype in stably edited knockout cell lines. Mathematic modeling confirmed that reduced PT length can account for the urinary excretion profile in LS. Both ocrl mutant zebrafish and zebrafish injected with ocrl morpholino showed truncated expression of megalin along the pronephric kidney, consistent with a shortened S1 segment. CONCLUSIONS Our data suggest a unifying model to explain how loss of OCRL results in tubular proteinuria as well as the other commonly observed renal manifestations of LS. We hypothesize that defective cell division during kidney development and/or repair compromises PT length and impairs kidney function in LS patients.
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Affiliation(s)
| | | | | | | | | | - Nairita Roy
- Department of Pathology, McGowan Institute for Regenerative Medicine, and Pittsburgh Liver Research Center, Pittsburgh, Pennsylvania
| | - Andrew W Duncan
- Department of Pathology, McGowan Institute for Regenerative Medicine, and Pittsburgh Liver Research Center, Pittsburgh, Pennsylvania
| | - Matthew J Lazzara
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia; and
| | - Neil A Hukriede
- Department of Developmental Biology, and.,Center for Critical Care Nephrology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | | | - Ora A Weisz
- Renal-Electrolyte Division, Department of Medicine,
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23
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Volpatti JR, Al-Maawali A, Smith L, Al-Hashim A, Brill JA, Dowling JJ. The expanding spectrum of neurological disorders of phosphoinositide metabolism. Dis Model Mech 2019; 12:12/8/dmm038174. [PMID: 31413155 PMCID: PMC6737944 DOI: 10.1242/dmm.038174] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Phosphoinositides (PIPs) are a ubiquitous group of seven low-abundance phospholipids that play a crucial role in defining localized membrane properties and that regulate myriad cellular processes, including cytoskeletal remodeling, cell signaling cascades, ion channel activity and membrane traffic. PIP homeostasis is tightly regulated by numerous inositol kinases and phosphatases, which phosphorylate and dephosphorylate distinct PIP species. The importance of these phospholipids, and of the enzymes that regulate them, is increasingly being recognized, with the identification of human neurological disorders that are caused by mutations in PIP-modulating enzymes. Genetic disorders of PIP metabolism include forms of epilepsy, neurodegenerative disease, brain malformation syndromes, peripheral neuropathy and congenital myopathy. In this Review, we provide an overview of PIP function and regulation, delineate the disorders associated with mutations in genes that modulate or utilize PIPs, and discuss what is understood about gene function and disease pathogenesis as established through animal models of these diseases. Summary: This Review highlights the intersection between phosphoinositides and the enzymes that regulate their metabolism, which together are crucial regulators of myriad cellular processes and neurological disorders.
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Affiliation(s)
- Jonathan R Volpatti
- Division of Neurology and Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Almundher Al-Maawali
- Division of Neurology and Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Genetics, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat 123, Oman
| | - Lindsay Smith
- Division of Neurology and Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Aqeela Al-Hashim
- Division of Neurology and Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Neuroscience, King Fahad Medical City, Riyadh 11525, Saudi Arabia
| | - Julie A Brill
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada.,Program in Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - James J Dowling
- Division of Neurology and Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada .,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
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24
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Abstract
Phosphoinositides (PIs) play pivotal roles in the regulation of many biological processes. The quality and quantity of PIs is regulated in time and space by the activity of PI kinases and PI phosphatases. The number of PI-metabolizing enzymes exceeds the number of PIs with, in many cases, more than one enzyme controlling the same biochemical step. This would suggest that the PI system has an intrinsic ability to buffer and compensate for the absence of a specific enzymatic activity. However, there are several examples of severe inherited human diseases caused by mutations in one of the PI enzymes, although other enzymes with the same activity are fully functional. The kidney depends strictly on PIs for physiological processes, such as cell polarization, filtration, solute reabsorption, and signal transduction. Indeed, alteration of the PI system in the kidney very often results in pathological conditions, both inherited and acquired. Most of the knowledge of the roles that PIs play in the kidney comes from the study of KO animal models for genes encoding PI enzymes and from the study of human genetic diseases, such as Lowe syndrome/Dent disease 2 and Joubert syndrome, caused by mutations in the genes encoding the PI phosphatases, OCRL and INPP5E, respectively.
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Affiliation(s)
- Leopoldo Staiano
- Telethon Institute of Genetics and Medicine, 80078 Pozzuoli, Italy
| | - Maria Antonietta De Matteis
- Telethon Institute of Genetics and Medicine, 80078 Pozzuoli, Italy .,University of Naples Federico II, 80131 Naples, Italy
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25
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Barnes J, Salas F, Mokhtari R, Dolstra H, Pedrosa E, Lachman HM. Modeling the neuropsychiatric manifestations of Lowe syndrome using induced pluripotent stem cells: defective F-actin polymerization and WAVE-1 expression in neuronal cells. Mol Autism 2018; 9:44. [PMID: 30147856 PMCID: PMC6094927 DOI: 10.1186/s13229-018-0227-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 07/29/2018] [Indexed: 12/12/2022] Open
Abstract
Background Lowe syndrome (LS) is a rare genetic disorder caused by loss of function mutations in the X-linked gene, OCRL, which codes for inositol polyphosphate 5-phosphatase. LS is characterized by the triad of congenital cataracts, neurodevelopmental impairment (primarily intellectual and developmental disabilities [IDD]), and renal proximal tubular dysfunction. Studies carried out over the years have shown that hypomorphic mutations in OCRL adversely affect endosome recycling and actin polymerization in kidney cells and patient-derived fibroblasts. The renal problem has been traced to an impaired recycling of megalin, a multi-ligand receptor that plays a key role in the reuptake of lipoproteins, amino acids, vitamin-binding proteins, and hormones. However, the neurodevelopmental aspects of the disorder have been difficult to study because the mouse knockout (KO) model does not display LS-related phenotypes. Fortunately, the discovery of induced pluripotent stem (iPS) cells has provided an opportunity to grow patient-specific neurons, which can be used to model neurodevelopmental disorders in vitro, as demonstrated in the many studies that have been published in the past few years in autism spectrum disorders (ASD), schizophrenia (SZ), bipolar disorder (BD), and IDD. Methods We now report the first findings in neurons and neural progenitor cells (NPCs) generated from iPS cells derived from patients with LS and their typically developing male siblings, as well as an isogenic line in which the OCRL gene has been incapacitated by a null mutation generated using CRISPR-Cas9 gene editing. Results We show that neuronal cells derived from patient-specific iPS cells containing hypomorphic variants are deficient in their capacity to produce F-filamentous actin (F-actin) fibers. Abnormalities were also found in the expression of WAVE-1, a component of the WAVE regulatory complex (WRC) that regulates actin polymerization. Curiously, neuronal cells carrying the engineered OCRL null mutation, in which OCRL protein is not expressed, did not show similar defects in F-actin and WAVE-1 expression. This is similar to the apparent lack of a phenotype in the mouse Ocrl KO model, and suggests that in the complete absence of OCRL protein, as opposed to producing a dysfunctional protein, as seen with the hypomorphic variants, there is partial compensation for the F-actin/WAVE-1 regulating function of OCRL. Conclusions Alterations in F-actin polymerization and WRC have been found in a number of genetic subgroups of IDD and ASD. Thus, LS, a very rare genetic condition, is linked to a more expansive family of genes responsible for neurodevelopmental disorders that have shared pathogenic features. Electronic supplementary material The online version of this article (10.1186/s13229-018-0227-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jesse Barnes
- 1Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Franklin Salas
- 2Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Ryan Mokhtari
- 3Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Hedwig Dolstra
- 4Swammerdam Institute of Life Sciences, University of Amsterdam, Amsterdam, Netherlands
| | - Erika Pedrosa
- 2Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Herbert M Lachman
- 1Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, USA.,2Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, Bronx, New York, USA.,5Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA.,6Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA
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26
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Del Signore SJ, Biber SA, Lehmann KS, Heimler SR, Rosenfeld BH, Eskin TL, Sweeney ST, Rodal AA. dOCRL maintains immune cell quiescence by regulating endosomal traffic. PLoS Genet 2017; 13:e1007052. [PMID: 29028801 PMCID: PMC5656325 DOI: 10.1371/journal.pgen.1007052] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 10/25/2017] [Accepted: 10/04/2017] [Indexed: 01/07/2023] Open
Abstract
Lowe Syndrome is a developmental disorder characterized by eye, kidney, and neurological pathologies, and is caused by mutations in the phosphatidylinositol-5-phosphatase OCRL. OCRL plays diverse roles in endocytic and endolysosomal trafficking, cytokinesis, and ciliogenesis, but it is unclear which of these cellular functions underlie specific patient symptoms. Here, we show that mutation of Drosophila OCRL causes cell-autonomous activation of hemocytes, which are macrophage-like cells of the innate immune system. Among many cell biological defects that we identified in docrl mutant hemocytes, we pinpointed the cause of innate immune cell activation to reduced Rab11-dependent recycling traffic and concomitantly increased Rab7-dependent late endosome traffic. Loss of docrl amplifies multiple immune-relevant signals, including Toll, Jun kinase, and STAT, and leads to Rab11-sensitive mis-sorting and excessive secretion of the Toll ligand Spåtzle. Thus, docrl regulation of endosomal traffic maintains hemocytes in a poised, but quiescent state, suggesting mechanisms by which endosomal misregulation of signaling may contribute to symptoms of Lowe syndrome. Lowe syndrome is a developmental disorder characterized by severe kidney, eye, and neurological symptoms, and is caused by mutations in the gene OCRL. OCRL has been shown to control many steps of packaging and transport of materials within cells, though it remains unclear which of these disrupted transport steps cause each of the many symptoms in Lowe syndrome patients. We found that in fruit flies, loss of OCRL caused transport defects at specific internal compartments in innate immune cells, resulting in amplification of multiple critical inflammatory signals. Similar inflammatory signals have been implicated in forms of epilepsy, which is a primary symptom in Lowe syndrome patients. Thus, our work uncovers a new function for OCRL in animals, and opens an exciting new avenue of investigation into how loss of OCRL causes the symptoms of Lowe syndrome.
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Affiliation(s)
- Steven J. Del Signore
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Sarah A. Biber
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Katherine S. Lehmann
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Stephanie R. Heimler
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Benjamin H. Rosenfeld
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Tania L. Eskin
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
| | - Sean T. Sweeney
- Department of Biology, University of York, York, United Kingdom
| | - Avital A. Rodal
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts, United States of America
- * E-mail:
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27
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Prosseda PP, Luo N, Wang B, Alvarado JA, Hu Y, Sun Y. Loss of OCRL increases ciliary PI(4,5)P 2 in Lowe oculocerebrorenal syndrome. J Cell Sci 2017; 130:3447-3454. [PMID: 28871046 DOI: 10.1242/jcs.200857] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 08/29/2017] [Indexed: 12/24/2022] Open
Abstract
Lowe syndrome is a rare X-linked disorder characterized by bilateral congenital cataracts and glaucoma, mental retardation, and proximal renal tubular dysfunction. Mutations in OCRL, an inositol polyphosphate 5-phosphatase that dephosphorylates PI(4,5)P2, cause Lowe syndrome. Previously we showed that OCRL localizes to the primary cilium, which has a distinct membrane phospholipid composition, but disruption of phosphoinositides in the ciliary membrane is poorly understood. Here, we demonstrate that cilia from Lowe syndrome patient fibroblasts exhibit increased levels of PI(4,5)P2 and decreased levels of PI4P. In particular, subcellular distribution of PI(4,5)P2 build-up was observed at the transition zone. Accumulation of ciliary PI(4,5)P2 was pronounced in mouse embryonic fibroblasts (MEFs) derived from Lowe syndrome mouse model as well as in Ocrl-null MEFs, which was reversed by reintroduction of OCRL. Similarly, expression of wild-type OCRL reversed the elevated PI(4,5)P2 in Lowe patient cells. Accumulation of sonic hedgehog protein in response to hedgehog agonist was decreased in MEFs derived from a Lowe syndrome mouse model. Together, our findings show for the first time an abnormality in ciliary phosphoinositides of both human and mouse cell models of Lowe syndrome.
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Affiliation(s)
- Philipp P Prosseda
- Stanford University, Department of Ophthalmology, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94304, USA
| | - Na Luo
- Eugene and Marilyn Glick Eye Institute, Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Biao Wang
- Stanford University, Department of Ophthalmology, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94304, USA
| | - Jorge A Alvarado
- Stanford University, Department of Ophthalmology, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94304, USA
| | - Yang Hu
- Stanford University, Department of Ophthalmology, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94304, USA
| | - Yang Sun
- Stanford University, Department of Ophthalmology, 1651 Page Mill Road, Rm 2220, Palo Alto, CA 94304, USA .,Palo Alto Veterans Administration, Palo Alto, CA 94304, USA
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28
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Abstract
Lowe syndrome is an X-linked disease that is characterized by congenital cataracts, central hypotonia, intellectual disability and renal Fanconi syndrome. The disease is caused by mutations in OCRL, which encodes an inositol polyphosphate 5-phosphatase (OCRL) that acts on phosphoinositides - quantitatively minor constituents of cell membranes that are nonetheless pivotal regulators of intracellular trafficking. In this Review we summarize the considerable progress made over the past decade in understanding the cellular roles of OCRL in regulating phosphoinositide balance along the endolysosomal pathway, a fundamental system for the reabsorption of proteins and solutes by proximal tubular cells. We discuss how studies of OCRL have led to important discoveries about the basic mechanisms of membrane trafficking and describe the key features and limitations of the currently available animal models of Lowe syndrome. Mutations in OCRL can also give rise to a milder pathology, Dent disease 2, which is characterized by renal Fanconi syndrome in the absence of extrarenal pathologies. Understanding how mutations in OCRL give rise to two clinical entities with differing extrarenal manifestations represents an opportunity to identify molecular pathways that could be targeted to develop treatments for these conditions.
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29
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Duran D, Jin SC, DeSpenza T, Nelson-Williams C, Cogal AG, Abrash EW, Harris PC, Lieske JC, Shimshak SJ, Mane S, Bilguvar K, DiLuna ML, Günel M, Lifton RP, Kahle KT. Digenic mutations of human OCRL paralogs in Dent's disease type 2 associated with Chiari I malformation. Hum Genome Var 2016; 3:16042. [PMID: 28018608 PMCID: PMC5143364 DOI: 10.1038/hgv.2016.42] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Accepted: 10/21/2016] [Indexed: 02/06/2023] Open
Abstract
OCRL1 and its paralog INPP5B encode phosphatidylinositol 5-phosphatases that localize to the primary cilium and have roles in ciliogenesis. Mutations in OCRL1 cause the X-linked Dent disease type 2 (DD2; OMIM# 300555), characterized by low-molecular weight proteinuria, hypercalciuria, and the variable presence of cataracts, glaucoma and intellectual disability without structural brain anomalies. Disease-causing mutations in INPP5B have not been described in humans. Here, we report the case of an 11-year-old boy with short stature and an above-average IQ; severe proteinuria, hypercalciuria and osteopenia resulting in a vertebral compression fracture; and Chiari I malformation with cervico-thoracic syringohydromyelia requiring suboccipital decompression. Sequencing revealed a novel, de novo DD2-causing 462 bp deletion disrupting exon 3 of OCRL1 and a maternally inherited, extremely rare (ExAC allele frequency 8.4×10−6) damaging missense mutation in INPP5B (p.A51V). This mutation substitutes an evolutionarily conserved amino acid in the protein’s critical PH domain. In silico analyses of mutation impact predicted by SIFT, PolyPhen2, MetaSVM and CADD algorithms were all highly deleterious. Together, our findings report a novel association of DD2 with Chiari I malformation and syringohydromyelia, and document the effects of digenic mutation of human OCRL paralogs. These findings lend genetic support to the hypothesis that impaired ciliogenesis may contribute to the development of Chiari I malformation, and implicates OCRL-dependent PIP3 metabolism in this mechanism.
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Affiliation(s)
- Daniel Duran
- Department of Neurosurgery, Yale School of Medicine , New Haven, CT, USA
| | - Sheng Chih Jin
- Department of Genetics, Yale School of Medicine , New Haven, CT, USA
| | - Tyrone DeSpenza
- Department of Neurosurgery, Yale School of Medicine , New Haven, CT, USA
| | - Carol Nelson-Williams
- Department of Genetics, Yale School of Medicine, New Haven, CT, USA; Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Andrea G Cogal
- Division of Nephrology and Hypertension, Mayo Clinic College of Medicine , Rochester, MN, USA
| | - Elizabeth W Abrash
- Division of Nephrology and Hypertension, Mayo Clinic College of Medicine , Rochester, MN, USA
| | - Peter C Harris
- Division of Nephrology and Hypertension, Mayo Clinic College of Medicine, Rochester, MN, USA; Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - John C Lieske
- Division of Nephrology and Hypertension, Mayo Clinic College of Medicine, Rochester, MN, USA; O'Brien Urology Research Center, Mayo Clinic College of Medicine, Rochester, MN, USA; Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Serena Je Shimshak
- Department of Neurosurgery, Yale School of Medicine , New Haven, CT, USA
| | - Shrikant Mane
- Yale Center for Genome Analysis, Yale School of Medicine, Yale University , New Haven, CT, USA
| | - Kaya Bilguvar
- Yale Center for Genome Analysis, Yale School of Medicine, Yale University , New Haven, CT, USA
| | - Michael L DiLuna
- Department of Neurosurgery, Yale School of Medicine , New Haven, CT, USA
| | - Murat Günel
- Department of Neurosurgery, Yale School of Medicine, New Haven, CT, USA; Department of Genetics, Yale School of Medicine, New Haven, CT, USA
| | | | - Kristopher T Kahle
- Department of Neurosurgery, Yale School of Medicine, New Haven, CT, USA; Department of Pediatrics, Yale School of Medicine, New Haven, CT, USA; Department of Cellular & Molecular Physiology, Yale School of Medicine, New Haven, CT, USA
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30
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Inoue K, Balkin DM, Liu L, Nandez R, Wu Y, Tian X, Wang T, Nussbaum R, De Camilli P, Ishibe S. Kidney Tubular Ablation of Ocrl/ Inpp5b Phenocopies Lowe Syndrome Tubulopathy. J Am Soc Nephrol 2016; 28:1399-1407. [PMID: 27895154 DOI: 10.1681/asn.2016080913] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Accepted: 10/05/2016] [Indexed: 12/26/2022] Open
Abstract
Lowe syndrome and Dent disease are two conditions that result from mutations of the inositol 5-phosphatase oculocerebrorenal syndrome of Lowe (OCRL) and share the feature of impaired kidney proximal tubule function. Genetic ablation of Ocrl in mice failed to recapitulate the human phenotypes, possibly because of the redundant functions of OCRL and its paralog type 2 inositol polyphosphate-5-phosphatase (INPP5B). Germline knockout of both paralogs in mice results in early embryonic lethality. We report that kidney tubule-specific inactivation of Inpp5b on a global Ocrl-knockout mouse background resulted in low molecular weight proteinuria, phosphaturia, and acidemia. At the cellular level, we observed a striking impairment of clathrin-dependent and -independent endocytosis in proximal tubules, phenocopying what has been reported for Dent disease caused by mutations in the gene encoding endosomal proton-chloride exchange transporter 5. These results suggest that the functions of OCRL/INPP5B and proton-chloride exchange transporter 5 converge on shared mechanisms, the impairment of which has a dramatic effect on proximal tubule endocytosis.
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Affiliation(s)
| | - Daniel M Balkin
- Cell Biology.,Howard Hughes Medical Institute, and.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale School of Medicine, New Haven, Connecticut
| | - Lijuan Liu
- Cell Biology.,Howard Hughes Medical Institute, and.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale School of Medicine, New Haven, Connecticut.,Neuroscience, and
| | - Ramiro Nandez
- Cell Biology.,Howard Hughes Medical Institute, and.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale School of Medicine, New Haven, Connecticut
| | - Yumei Wu
- Cell Biology.,Howard Hughes Medical Institute, and.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale School of Medicine, New Haven, Connecticut.,Neuroscience, and
| | | | | | - Robert Nussbaum
- Department of Medicine and.,Institute of Human Genetics, University of California, San Francisco, California; and.,Howard Hughes Medical Institute, and
| | - Pietro De Camilli
- Cell Biology, .,Howard Hughes Medical Institute, and.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale School of Medicine, New Haven, Connecticut.,Neuroscience, and
| | - Shuta Ishibe
- Departments of Internal Medicine, .,Cellular and Molecular Physiology
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31
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Abstract
Cells lining the proximal tubule (PT) of the kidney are highly specialized for apical endocytosis of filtered proteins and small bioactive molecules from the glomerular ultrafiltrate to maintain essentially protein-free urine. Compromise of this pathway results in low molecular weight (LMW) proteinuria that can progress to end-stage kidney disease. This review describes our current understanding of the endocytic pathway and the multiligand receptors that mediate LMW protein uptake in PT cells, how these are regulated in response to physiologic cues, and the molecular basis of inherited diseases characterized by LMW proteinuria.
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Affiliation(s)
- Megan L Eshbach
- Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261; ,
| | - Ora A Weisz
- Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261; ,
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32
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Abstract
The oculocerebrorenal syndrome of Lowe is a rare X-linked multisystemic disorder characterized by the triad of congenital cataracts, intellectual disability, and proximal renal tubular dysfunction. Whereas the ocular manifestations and severe muscular hypotonia are the typical first diagnostic clues apparent at birth, the manifestations of incomplete renal Fanconi syndrome are often recognized only later in life. Other characteristic features are progressive severe growth retardation and behavioral problems, with tantrums. Many patients develop a debilitating arthropathy. Treatment is symptomatic, and the life span rarely exceeds 40 years. The causative oculocerebrorenal syndrome of Lowe gene (OCRL) encodes the inositol polyphosphate 5-phosphatase OCRL-1. OCRL variants have not only been found in classic Lowe syndrome, but also in patients with a predominantly renal phenotype classified as Dent disease type 2 (Dent-2). Recent data indicate that there is a phenotypic continuum between Dent-2 disease and Lowe syndrome, suggesting that there are individual differences in the ability to compensate for the loss of enzyme function. Extensive research has demonstrated that OCRL-1 is involved in multiple intracellular processes involving endocytic trafficking and actin skeleton dynamics. This explains the multi-organ manifestations of the disease. Still, the mechanisms underlying the wide phenotypic spectrum are poorly understood, and we are far from a causative therapy. In this review, we provide an update on clinical and molecular genetic findings in Lowe syndrome and the cellular and physiological functions of OCRL-1.
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33
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Oltrabella F, Pietka G, Ramirez IBR, Mironov A, Starborg T, Drummond IA, Hinchliffe KA, Lowe M. The Lowe syndrome protein OCRL1 is required for endocytosis in the zebrafish pronephric tubule. PLoS Genet 2015; 11:e1005058. [PMID: 25838181 PMCID: PMC4383555 DOI: 10.1371/journal.pgen.1005058] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 02/07/2015] [Indexed: 02/03/2023] Open
Abstract
Lowe syndrome and Dent-2 disease are caused by mutation of the inositol 5-phosphatase OCRL1. Despite our increased understanding of the cellular functions of OCRL1, the underlying basis for the renal tubulopathy seen in both human disorders, of which a hallmark is low molecular weight proteinuria, is currently unknown. Here, we show that deficiency in OCRL1 causes a defect in endocytosis in the zebrafish pronephric tubule, a model for the mammalian renal tubule. This coincides with a reduction in levels of the scavenger receptor megalin and its accumulation in endocytic compartments, consistent with reduced recycling within the endocytic pathway. We also observe reduced numbers of early endocytic compartments and enlarged vacuolar endosomes in the sub-apical region of pronephric cells. Cell polarity within the pronephric tubule is unaffected in mutant embryos. The OCRL1-deficient embryos exhibit a mild ciliogenesis defect, but this cannot account for the observed impairment of endocytosis. Catalytic activity of OCRL1 is required for renal tubular endocytosis and the endocytic defect can be rescued by suppression of PIP5K. These results indicate for the first time that OCRL1 is required for endocytic trafficking in vivo, and strongly support the hypothesis that endocytic defects are responsible for the renal tubulopathy in Lowe syndrome and Dent-2 disease. Moreover, our results reveal PIP5K as a potential therapeutic target for Lowe syndrome and Dent-2 disease. Phosphoinositide lipids are key regulators of cellular physiology and consequently enzymes that generate or remove these lipids are of fundamental importance. Mutation of one such enzyme, called OCRL1, causes two disorders in humans, Lowe syndrome and Dent-2 disease. However, the underlying mechanisms remain poorly defined. Here, we demonstrate that OCRL1 regulates endocytosis, the process by which cells internalize material from their extracellular environment. Importantly, this is demonstrated in a physiologically relevant tissue in vivo, namely the zebrafish renal tubule. Defective endocytosis can explain the renal symptoms seen in Lowe syndrome and Dent-2 patients. We also report that defects in cell polarity or cilia formation cannot explain the renal symptoms. This study not only increases our understanding of the endocytic pathway, it also provides a mechanistic explanation for the renal defects observed in Lowe syndrome and Dent-2 patients.
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Affiliation(s)
| | - Grzegorz Pietka
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | | | - Aleksandr Mironov
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Toby Starborg
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Iain A Drummond
- Nephrology Division, Massachusetts General Hospital and Department of Genetics, Harvard Medical School, Charlestown, Massachusetts, United States of America
| | | | - Martin Lowe
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
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34
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Madhivanan K, Ramadesikan S, Aguilar RC. Role of Ocrl1 in primary cilia assembly. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 317:331-47. [PMID: 26008789 DOI: 10.1016/bs.ircmb.2015.02.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Lowe syndrome is a lethal X-linked genetic disorder characterized by congenital cataracts, mental retardation, and kidney dysfunction. It is caused by mutations in the OCRL1 (oculocerebrorenal syndrome of Lowe) gene that encodes a phosphatidylinositol 5-phosphatase (EC 3.1.3.36). The gene product Ocrl1 has been linked to a multitude of functions due to the central role played by phosphoinositides in signaling. Moreover, this protein also has the ability to bind Rho GTPases, the master regulators of the actin cytoskeleton, and to interact with elements of the vesicle trafficking machinery. It is currently under investigation how deficiencies in Ocrl1 affect these different processes and contribute to patient symptoms. This chapter outlines the known physiological roles of Ocrl1 which might be relevant to the mechanism underlying Lowe syndrome.
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Affiliation(s)
| | - Swetha Ramadesikan
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - R Claudio Aguilar
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
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35
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Surendran K, Vitiello SP, Pearce DA. Lysosome dysfunction in the pathogenesis of kidney diseases. Pediatr Nephrol 2014; 29:2253-61. [PMID: 24217784 PMCID: PMC4018427 DOI: 10.1007/s00467-013-2652-z] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 09/29/2013] [Accepted: 10/01/2013] [Indexed: 12/18/2022]
Abstract
The lysosome, an organelle central to macromolecule degradation and recycling, plays a pivotal role in normal cell processes, ranging from autophagy to redox regulation. Not surprisingly, lysosomes are an integral part of the renal epithelial molecular machinery that facilitates normal renal physiology. Two inherited diseases that manifest as kidney dysfunction are Fabry's disease and cystinosis, each of which is caused by a primary biochemical defect at the lysosome resulting from loss-of-function mutations in genes that encode lysosomal proteins. The functions of the lysosomes in the kidney and how lysosomal dysfunction might contribute to Fabry's disease and cystinosis are discussed. Unlike most other pediatric renal diseases, therapies are available for Fabry's disease and cystinosis, but require early diagnosis. Recent analysis of ceroid neuronal lipofuscinosis type 3 (Cln3) null mice, a mouse model of lysosomal disease that is primarily associated with neurological deficits, revealed renal functional abnormalities. As current and future therapeutics increase the life-span of those suffering from diseases like neuronal ceroid lipofuscinosis, it remains a distinct possibility that many more lysosomal disorders that primarily manifest as infant and juvenile neurodegenerative diseases may also include renal disease phenotypes.
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Affiliation(s)
- Kameswaran Surendran
- Sanford Children’s Health Research Center, Sanford Research/USD, Sioux Falls, SD 57104, USA,Department of Pediatrics, Sanford School of Medicine, Sioux Falls, SD 57104, USA
| | - Seasson P. Vitiello
- Sanford Children’s Health Research Center, Sanford Research/USD, Sioux Falls, SD 57104, USA,Augustana College, Sioux Falls, SD
| | - David A. Pearce
- Sanford Children’s Health Research Center, Sanford Research/USD, Sioux Falls, SD 57104, USA,Department of Pediatrics, Sanford School of Medicine, Sioux Falls, SD 57104, USA,Corresponding Author: David A. Pearce, Sanford Research/USD, 2301 East 60th Street North, Sioux Falls, SD, 57104-0589, Telephone: 605 312-6004, FAX: 605 312-6071,
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Kim HK, Kim JH, Kim YM, Kim GH, Lee BH, Choi JH, Yoo HW. Lowe syndrome: a single center's experience in Korea. KOREAN JOURNAL OF PEDIATRICS 2014; 57:140-8. [PMID: 24778696 PMCID: PMC4000760 DOI: 10.3345/kjp.2014.57.3.140] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Revised: 10/13/2013] [Accepted: 10/16/2013] [Indexed: 01/12/2023]
Abstract
Purpose Lowe syndrome is a rare, X-linked recessive disorder caused by mutations in the OCRL gene. It involves multiple anatomic systems, particularly the eyes, central nervous system, and kidneys, and leads to profound growth failure and global developmental delay. This study evaluated the clinical and genetic characteristics of Korean patients with Lowe syndrome. Methods The clinical findings and results of genetic studies were reviewed for 12 male patients diagnosed with Lowe syndrome at a single medical institution. Results The mean age of the patients at presentation was 2.2 months (range, 0-4 months), although the diagnosis was delayed by a mean of 2.8 years (range, 0-9.7 years). The mean follow-up period was 9.0 years (range, 0.6-16.7 years). Nine mutations in OCRL were identified in 11 patients (92%), with three novel mutations. The main presentation was congenital cataract in both eyes necessitating early cataract removal in the 11 patients with impaired visual acuity. Profound short stature and developmental delay were observed in all patients, and seizures occurred in 50% of the patients. All patients suffered from proximal renal tubular dysfunction, and one patient developed chronic renal failure. Other manifestations included pathologic fracture (50%), cutaneous cysts (42%), and cryptorchidism (42%). However, there was no bleeding tendency, and none of the patients died during the study period. Conclusion This study describes the clinical and genetic characteristics of Korean patients with Lowe syndrome. The observations are helpful for understanding the natural courses of Lowe syndrome and for appropriate genetic counseling.
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Affiliation(s)
- Hyun-Kyung Kim
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Ja Hye Kim
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Yoo-Mi Kim
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Gu-Hwan Kim
- Medical Genetics Center, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Beom Hee Lee
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea. ; Medical Genetics Center, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Jin-Ho Choi
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Han-Wook Yoo
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea. ; Medical Genetics Center, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
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Mehta ZB, Pietka G, Lowe M. The cellular and physiological functions of the Lowe syndrome protein OCRL1. Traffic 2014; 15:471-87. [PMID: 24499450 PMCID: PMC4278560 DOI: 10.1111/tra.12160] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 02/03/2014] [Accepted: 02/05/2014] [Indexed: 12/17/2022]
Abstract
Phosphoinositide lipids play a key role in cellular physiology, participating in a wide array of cellular processes. Consequently, mutation of phosphoinositide-metabolizing enzymes is responsible for a growing number of diseases in humans. Two related disorders, oculocerebrorenal syndrome of Lowe (OCRL) and Dent-2 disease, are caused by mutation of the inositol 5-phosphatase OCRL1. Here, we review recent advances in our understanding of OCRL1 function. OCRL1 appears to regulate many processes within the cell, most of which depend upon coordination of membrane dynamics with remodeling of the actin cytoskeleton. Recently developed animal models have managed to recapitulate features of Lowe syndrome and Dent-2 disease, and revealed new insights into the underlying mechanisms of these disorders. The continued use of both cell-based approaches and animal models will be key to fully unraveling OCRL1 function, how its loss leads to disease and, importantly, the development of therapeutics to treat patients.
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Affiliation(s)
- Zenobia B Mehta
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK; Current address: Faculty of Medicine, Imperial College, London, UK
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Luo N, Kumar A, Conwell M, Weinreb RN, Anderson R, Sun Y. Compensatory Role of Inositol 5-Phosphatase INPP5B to OCRL in Primary Cilia Formation in Oculocerebrorenal Syndrome of Lowe. PLoS One 2013; 8:e66727. [PMID: 23805271 PMCID: PMC3689662 DOI: 10.1371/journal.pone.0066727] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 05/10/2013] [Indexed: 12/11/2022] Open
Abstract
Inositol phosphatases are important regulators of cell signaling, polarity, and vesicular trafficking. Mutations in OCRL, an inositol polyphosphate 5-phosphatase, result in Oculocerebrorenal syndrome of Lowe, an X-linked recessive disorder that presents with congenital cataracts, glaucoma, renal dysfunction and mental retardation. INPP5B is a paralog of OCRL and shares similar structural domains. The roles of OCRL and INPP5B in the development of cataracts and glaucoma are not understood. Using ocular tissues, this study finds low levels of INPP5B present in human trabecular meshwork but high levels in murine trabecular meshwork. In contrast, OCRL is localized in the trabecular meshwork and Schlemm's canal endothelial cells in both human and murine eyes. In cultured human retinal pigmented epithelial cells, INPP5B was observed in the primary cilia. A functional role for INPP5B is revealed by defects in cilia formation in cells with silenced expression of INPP5B. This is further supported by the defective cilia formation in zebrafish Kupffer's vesicles and in cilia-dependent melanosome transport assays in inpp5b morphants. Taken together, this study indicates that OCRL and INPP5B are differentially expressed in the human and murine eyes, and play compensatory roles in cilia development.
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Affiliation(s)
- Na Luo
- Glick Eye Institute, Department of Ophthalmology, Department of Biochemistry and Cell Biology, Department of Dermatology, Indiana University Indianapolis, Indiana, United States of America
| | - Akhilesh Kumar
- Glick Eye Institute, Department of Ophthalmology, Department of Biochemistry and Cell Biology, Department of Dermatology, Indiana University Indianapolis, Indiana, United States of America
| | - Michael Conwell
- Glick Eye Institute, Department of Ophthalmology, Department of Biochemistry and Cell Biology, Department of Dermatology, Indiana University Indianapolis, Indiana, United States of America
| | - Robert N. Weinreb
- Department of Ophthalmology, University of California San Diego, San Diego, California, United States of America
| | - Ryan Anderson
- Department of Pediatrics, Indiana University Indianapolis, Indiana,United States of America
| | - Yang Sun
- Glick Eye Institute, Department of Ophthalmology, Department of Biochemistry and Cell Biology, Department of Dermatology, Indiana University Indianapolis, Indiana, United States of America
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Abstract
Phosphoinositide signalling molecules interact with a plethora of effector proteins to regulate cell proliferation and survival, vesicular trafficking, metabolism, actin dynamics and many other cellular functions. The generation of specific phosphoinositide species is achieved by the activity of phosphoinositide kinases and phosphatases, which phosphorylate and dephosphorylate, respectively, the inositol headgroup of phosphoinositide molecules. The phosphoinositide phosphatases can be classified as 3-, 4- and 5-phosphatases based on their specificity for dephosphorylating phosphates from specific positions on the inositol head group. The SAC phosphatases show less specificity for the position of the phosphate on the inositol ring. The phosphoinositide phosphatases regulate PI3K/Akt signalling, insulin signalling, endocytosis, vesicle trafficking, cell migration, proliferation and apoptosis. Mouse knockout models of several of the phosphoinositide phosphatases have revealed significant physiological roles for these enzymes, including the regulation of embryonic development, fertility, neurological function, the immune system and insulin sensitivity. Importantly, several phosphoinositide phosphatases have been directly associated with a range of human diseases. Genetic mutations in the 5-phosphatase INPP5E are causative of the ciliopathy syndromes Joubert and MORM, and mutations in the 5-phosphatase OCRL result in Lowe's syndrome and Dent 2 disease. Additionally, polymorphisms in the 5-phosphatase SHIP2 confer diabetes susceptibility in specific populations, whereas reduced protein expression of SHIP1 is reported in several human leukaemias. The 4-phosphatase, INPP4B, has recently been identified as a tumour suppressor in human breast and prostate cancer. Mutations in one SAC phosphatase, SAC3/FIG4, results in the degenerative neuropathy, Charcot-Marie-Tooth disease. Indeed, an understanding of the precise functions of phosphoinositide phosphatases is not only important in the context of normal human physiology, but to reveal the mechanisms by which these enzyme families are implicated in an increasing repertoire of human diseases.
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Conduit SE, Dyson JM, Mitchell CA. Inositol polyphosphate 5-phosphatases; new players in the regulation of cilia and ciliopathies. FEBS Lett 2012; 586:2846-57. [PMID: 22828281 DOI: 10.1016/j.febslet.2012.07.037] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 07/16/2012] [Accepted: 07/16/2012] [Indexed: 10/28/2022]
Abstract
Phosphoinositides regulate numerous cellular events via the recruitment and activation of multiple lipid-binding effector proteins. The precise temporal and spatial regulation of phosphoinositide signals by the co-ordinated activities of phosphoinositide kinases and phosphatases is essential for homeostasis and development. Mutations in two inositol polyphosphate 5-phosphatases, INPP5E and OCRL, cause the cerebrorenal syndromes of Joubert and Lowe's, respectively. INPP5E and OCRL exhibit overlapping phosphoinositide substrate specificity and subcellular localisation, including an association with the primary cilia. Here, we review recent studies that identify a new role for these enzymes in the regulation of primary cilia function. Joubert syndrome has been extensively linked to primary cilia defects, and Lowe's may represent a new class of 'ciliopathy associated' syndromes.
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Affiliation(s)
- Sarah E Conduit
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
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Besouw MTP, van Pelt AMM, Gaide Chevronnay HP, Courtoy PJ, Pastore A, Goossens E, Devuyst O, Antignac C, Levtchenko EN. Studying nonobstructive azoospermia in cystinosis: histologic examination of testes and epididymis and sperm analysis in a Ctns⁻/⁻ mouse model. Fertil Steril 2012; 98:162-5. [PMID: 22578532 DOI: 10.1016/j.fertnstert.2012.03.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 03/16/2012] [Accepted: 03/27/2012] [Indexed: 11/18/2022]
Abstract
OBJECTIVE To study the pathogenesis of male infertility in cystinosis due to nonobstructive azoospermia, using a Ctns(-/-) mouse model. DESIGN Observational case-control study. SETTING Academic research laboratory. ANIMAL(S) Male C57BL/6 Ctns(-/-) mice were compared with C57BL/6 wild-type (wt) mice. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Fertility was studied using litter size (n = 3 vs. n = 2). After animals were sacrificed, testes, epididymis, and vas deferens were removed for testicular cystine measurements (n = 5 vs. n = 6), histologic studies (n = 3 vs. n = 3), and sperm analysis (n = 3 vs. n = 3). RESULT(S) Mean testicular cystine content was significantly higher in Ctns(-/-) mice compared with wt mice (26.6 ± 1.22 vs. 0.1 ± 0.01 nmol cystine/mg protein). Testes of Ctns(-/-) mice had lower weight compared with wt mice (0.096 ± 0.009 g vs. 0.112 ± 0.004 g), but mice fertility was similar (litter size 6.6 ± 1.4 vs. 6.3 ± 2.6 pups). Neither histologic nor sperm abnormalities were found. CONCLUSION(S) The Ctns(-/-) mouse model generated on C57BL/6 background is not suitable for clarifying the pathogenesis of male infertility in cystinosis. The etiology of nonobstructive azoospermia in these patients remains unclear.
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Affiliation(s)
- Martine T P Besouw
- Department of Pediatric Nephrology, University Hospitals Leuven, Leuven, Belgium.
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Ke YH, He JW, Fu WZ, Zhang ZL. Identification of two novel mutations in the OCRL1 gene in two Chinese families with Lowe syndrome. Nephrology (Carlton) 2012; 17:20-5. [PMID: 21854507 DOI: 10.1111/j.1440-1797.2011.01514.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM Lowe syndrome is a rare, multisystem, X-linked disorder characterized by anomalies affecting the eyes, the nervous system and the kidneys. The objective of this study was to identify and characterize the clinical manifestations of mutations of the causative gene in two Chinese families with Lowe syndrome. METHODS Lowe syndrome was diagnosed based on the clinical manifestations and laboratory and imaging findings. Altogether, 164 DNA samples, including samples from three affected subjects, five family members (from two families) and 156 healthy donors, were analyzed to identify the mutations in the OCRL1 gene. RESULTS In family 1, proband 1 had a novel nonsense mutation (c.880G>T) in exon 10 of the OCRL1. This mutation led to a premature termination of the OCRL1 protein (p.Glu294X). In family 2, a novel insertion mutation (c.2626dupA) in exon 24 of OCRL1 was found in proband 2 and his affected elder brother. This mutation likely results in the degradation of the OCRL1 protein (p.Met876AsnfsX8). Both probands' mothers were identified as carriers of the respective mutations. These mutations were not found in the unrelated controls. CONCLUSIONS Our study suggests that the novel nonsense mutation (c.880G>T) in exon 10 and the novel insertion mutation (c.2626dupA) in exon 24 of the OCRL1 gene cause Lowe syndrome in these two Chinese families.
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Affiliation(s)
- Yao-Hua Ke
- Metabolic Bone Disease and Genetic Research Unit, The Department of Osteoporosis and Bone Diseases, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
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Taranta A, Petrini S, Citti A, Boldrini R, Corallini S, Bellomo F, Levtchenko E, Emma F. Distribution of cystinosin-LKG in human tissues. Histochem Cell Biol 2012; 138:351-63. [PMID: 22544350 DOI: 10.1007/s00418-012-0958-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/13/2012] [Indexed: 12/31/2022]
Abstract
Nephropathic cystinosis is multisystemic progressive disorder caused by mutations of CTNS gene that encodes for the lysosomal cystine co-transporter cystinosin, and for a less abundant isoform termed cystinosin-LKG, which is expressed in not only lysosomes but also other cell compartments. To overcome the absence of high-quality antibodies against cystinosin, we have obtained a rabbit antiserum against cystinosin-LKG and have analyzed in human tissues the expression of the two known cystinosin isoforms by RT-PCR, and the expression of cystinosin-LKG by immunohistochemistry. In most tissues, CTNS-LKG represents 5-20 % of CTNS transcripts, with the exception of the testis that expresses both isoforms in equal proportions. Cystinosin-LKG was found to be highly expressed in renal tubular cells, pancreatic islets of Langerhans, Leydig cells of the testis, mucoserous glands of the bronchial wall, melanocytes and keratinocytes. These results are parallel with many features of cystinosis, such as early onset Fanconi syndrome, male infertility, diabetes mellitus and hypopigmentation. Intermediate expression levels were of the LKG isoform observed in the gastro-intestinal tract and thyroid glands; low levels of expression were observed in the brain, skeletal and cardiac muscles.
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Affiliation(s)
- Anna Taranta
- Division of Nephrology, Department of Nephrology and Urology, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.
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Luo N, West CC, Murga-Zamalloa CA, Sun L, Anderson RM, Wells CD, Weinreb RN, Travers JB, Khanna H, Sun Y. OCRL localizes to the primary cilium: a new role for cilia in Lowe syndrome. Hum Mol Genet 2012; 21:3333-44. [PMID: 22543976 PMCID: PMC3392109 DOI: 10.1093/hmg/dds163] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Oculocerebral renal syndrome of Lowe (OCRL or Lowe syndrome), a severe X-linked congenital disorder characterized by congenital cataracts and glaucoma, mental retardation and kidney dysfunction, is caused by mutations in the OCRL gene. OCRL is a phosphoinositide 5-phosphatase that interacts with small GTPases and is involved in intracellular trafficking. Despite extensive studies, it is unclear how OCRL mutations result in a myriad of phenotypes found in Lowe syndrome. Our results show that OCRL localizes to the primary cilium of retinal pigment epithelial cells, fibroblasts and kidney tubular cells. Lowe syndrome-associated mutations in OCRL result in shortened cilia and this phenotype can be rescued by the introduction of wild-type OCRL; in vivo, knockdown of ocrl in zebrafish embryos results in defective cilia formation in Kupffer vesicles and cilia-dependent phenotypes. Cumulatively, our data provide evidence for a role of OCRL in cilia maintenance and suggest the involvement of ciliary dysfunction in the manifestation of Lowe syndrome.
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Affiliation(s)
- Na Luo
- Department of Ophthalmology, Glick Eye Institute, Indiana University, 1601 W Michigan St., Indianapolis, IN 46202, USA
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Wu G, Zhang W, Na T, Jing H, Wu H, Peng JB. Suppression of intestinal calcium entry channel TRPV6 by OCRL, a lipid phosphatase associated with Lowe syndrome and Dent disease. Am J Physiol Cell Physiol 2012; 302:C1479-91. [PMID: 22378746 DOI: 10.1152/ajpcell.00277.2011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Oculocerebrorenal syndrome of Lowe (OCRL) gene product is a phosphatidyl inositol 4,5-bisphosphate [PI(4,5)P(2)] 5-phosphatase, and mutations of OCRL cause Lowe syndrome and Dent disease, both of which are frequently associated with hypercalciuria. Transient receptor potential, vanilloid subfamily, subtype 6 (TRPV6) is an intestinal epithelial Ca(2+) channel mediating active Ca(2+) absorption. Hyperabsorption of Ca(2+) was found in patients of Dent disease with increased Ca(2+) excretion. In this study, we tested whether TRPV6 is regulated by OCRL and, if so, to what extent it is altered by Dent-causing OCRL mutations using Xenopus laevis oocyte expression system. Exogenous OCRL decreased TRPV6-mediated Ca(2+) uptake by regulating the function and trafficking of TRPV6 through different domains of OCRL. The PI(4,5)P(2) 5-phosphatase domain suppressed the TRPV6-mediated Ca(2+) transport likely through regulating the PI(4,5)P(2) level needed for TRPV6 function without affecting TRPV6 protein abundance of TRPV6 at the cell surface. The forward trafficking of TRPV6 was decreased by OCRL. The Rab binding domain in OCRL was involved in regulating the trafficking of TRPV6. Knocking down endogenous X. laevis OCRL by antisense approach increased TRPV6-mediated Ca(2+) transport and TRPV6 forward trafficking. All seven Dent-causing OCRL mutations examined exhibited alleviation of the inhibitory effect on TRPV6-mediated Ca(2+) transport together with decreased overall PI(4,5)P(2) 5-phosphatase activity. In conclusion, OCRL suppresses TRPV6 via two separate mechanisms. The disruption of PI(4,5)P(2) 5-phosphatase activity by Dent-causing mutations of OCRL may lead to increased intestinal Ca(2+) absorption and, in turn, hypercalciuria.
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Affiliation(s)
- Guojin Wu
- Nephrology Research and Training Center, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294-0006, USA
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Pirruccello M, De Camilli P. Inositol 5-phosphatases: insights from the Lowe syndrome protein OCRL. Trends Biochem Sci 2012; 37:134-43. [PMID: 22381590 DOI: 10.1016/j.tibs.2012.01.002] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/13/2012] [Accepted: 01/24/2012] [Indexed: 12/01/2022]
Abstract
The precise regulation of phosphoinositide lipids in cellular membranes is crucial for cellular survival and function. Inositol 5-phosphatases have been implicated in a variety of disorders, including various cancers, obesity, type 2 diabetes, neurodegenerative diseases and rare genetic conditions. Despite the obvious impact on human health, relatively little structural and biochemical information is available for this family. Here, we review recent structural and mechanistic work on the 5-phosphatases with a focus on OCRL, whose loss of function results in oculocerebrorenal syndrome of Lowe and Dent 2 disease. Studies of OCRL emphasize how the actions of 5-phosphatases rely on both intrinsic and extrinsic membrane recognition properties for full catalytic function. Additionally, structural analysis of missense mutations in the catalytic domain of OCRL provides insight into the phenotypic heterogeneity observed in Lowe syndrome and Dent disease.
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Affiliation(s)
- Michelle Pirruccello
- Department of Cell Biology, HHMI and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA
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Ramirez IBR, Pietka G, Jones DR, Divecha N, Alia A, Baraban SC, Hurlstone AFL, Lowe M. Impaired neural development in a zebrafish model for Lowe syndrome. Hum Mol Genet 2011; 21:1744-59. [PMID: 22210625 PMCID: PMC3313792 DOI: 10.1093/hmg/ddr608] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Lowe syndrome, which is characterized by defects in the central nervous system, eyes and kidneys, is caused by mutation of the phosphoinositide 5-phosphatase OCRL1. The mechanisms by which loss of OCRL1 leads to the phenotypic manifestations of Lowe syndrome are currently unclear, in part, owing to the lack of an animal model that recapitulates the disease phenotype. Here, we describe a zebrafish model for Lowe syndrome using stable and transient suppression of OCRL1 expression. Deficiency of OCRL1, which is enriched in the brain, leads to neurological defects similar to those reported in Lowe syndrome patients, namely increased susceptibility to heat-induced seizures and cystic brain lesions. In OCRL1-deficient embryos, Akt signalling is reduced and there is both increased apoptosis and reduced proliferation, most strikingly in the neural tissue. Rescue experiments indicate that catalytic activity and binding to the vesicle coat protein clathrin are essential for OCRL1 function in these processes. Our results indicate a novel role for OCRL1 in neural development, and support a model whereby dysregulation of phosphoinositide metabolism and clathrin-mediated membrane traffic leads to the neurological symptoms of Lowe syndrome.
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