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Elena Levtchenko - One of the best experts on this subject based on the ideXlab platform.
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Swallowing dysfunction in patients with nephropathic Cystinosis
Molecular genetics and metabolism, 2019Co-Authors: A.e. Van Rijssel, Elena Levtchenko, Koenraad Veys, S. Knuijt, Mirian C H JanssenAbstract:Abstract Introduction Nephropathic Cystinosis is a rare autosomal recessive lysosomal storage disorder caused by mutations in the CTNS gene. Patients with nephropathic Cystinosis suffer not only from renal disease but have also other systemic complications like myopathy and swallowing dysfunction. Dysphagia for solid food is mentioned in patients with Cystinosis, but in clinical practice swallowing investigations are only performed when the patient has complaints. The aim of this study was to explore the swallowing function in patients with Cystinosis by use of the Test of Mastication and Swallowing Solids (TOMASS), and to compare their performance with patients with myotonic dystrophy type 1 – a neuromuscular disease in which dysphagia for solid food is a known problem. Methods Twenty adult patients with Cystinosis (11 men and 9 women, range 19–51 years) and 10 patients with myotonic dystrophy type 1 (5 men and 5 women, range 20–60 years) were included. All Cystinosis patients were treated with cysteamine. Data of the two groups were compared with normative data using independent-samples t-tests. In case the variables were not normally distributed, the non-parametric Mann-Whitney U test was used. Results There was a significant difference in the number of bites, masticatory cycles, swallows and total time between the normal values and Cystinosis patients. The results of the Cystinosis patients were comparable to those of the patients with myotonic dystrophy. Discussion and conclusion Adult patients with Cystinosis have significant dysphagia for solid food. Clinicians treating these patients should be aware of this fact. The TOMASS can be performed easily in clinical practice to investigate whether patients with Cystinosis have swallowing dysfunction. The swallowing dysfunction can now be diagnosed by use of a non-invasive, very simple, non-harmful test. It can be discussed whether this should be added to the regular care scheme of Cystinosis patients in order to regularly follow-up swallowing function.
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molecular basis of Cystinosis geographic distribution functional consequences of mutations in the ctns gene and potential for repair
Nephron, 2019Co-Authors: Dries David, Sante Princiero Berlingerio, Mohamed A Elmonem, Fanny Oliveira Arcolino, Neveen A Soliman, Bert Van Den Heuvel, Rik Gijsbers, Elena LevtchenkoAbstract:Mutations in the CTNS gene encoding the lysosomal membrane cystine transporter cystinosin are the cause of Cystinosis, an autosomal recessive lysosomal storage disease. More than 140 CTNS mutations have been reported worldwide. Recent studies have discovered that cystinosin exerts other key cellular functions beyond cystine transport such as regulation of oxidative state, lysosomal dynamics and autophagy. Here, we review the different mutations described in the CTNS gene and the geographical distribution of incidence. In addition, the characteristics of the various mutations in relation to the functions of cystinosin needs to be further elucidated. In this review, we highlight the functional consequences of the different mutations in correlation with the clinical phenotypes. Moreover, we propose how this understanding would be fundamental for the development of new technologies through targeted gene therapy, holding promises for a possible cure of the kidney and extra-renal phenotypes of Cystinosis.
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Cystinosis: a review
Orphanet journal of rare diseases, 2016Co-Authors: Mohamed A Elmonem, Koenraad Veys, Neveen A Soliman, Lambertus P Van Den Heuvel, Maria Van Dyck, Elena LevtchenkoAbstract:Cystinosis is the most common hereditary cause of renal Fanconi syndrome in children. It is an autosomal recessive lysosomal storage disorder caused by mutations in the CTNS gene encoding for the carrier protein cystinosin, transporting cystine out of the lysosomal compartment. Defective cystinosin function leads to intra-lysosomal cystine accumulation in all body cells and organs. The kidneys are initially affected during the first year of life through proximal tubular damage followed by progressive glomerular damage and end stage renal failure during mid-childhood if not treated. Other affected organs include eyes, thyroid, pancreas, gonads, muscles and CNS. Leucocyte cystine assay is the cornerstone for both diagnosis and therapeutic monitoring of the disease. Several lines of treatment are available for Cystinosis including the cystine depleting agent cysteamine, renal replacement therapy, hormonal therapy and others; however, no curative treatment is yet available. In the current review we will discuss the most important clinical features of the disease, advantages and disadvantages of the current diagnostic and therapeutic options and the main topics of future research in Cystinosis.
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mutational spectrum of the ctns gene in egyptian patients with nephropathic Cystinosis
JIMD Reports, 2014Co-Authors: Neveen A Soliman, Mohamed A Elmonem, Lambertus P Van Den Heuvel, Rehab Abdel H Hamid, Mohamed A Gamal, Inge Bongaers, Sandrine Marie, Elena LevtchenkoAbstract:Background: Nephropathic Cystinosis is a rare autosomal recessive disorder caused by mutations in the CTNS gene, encoding for cystinosin, a carrier protein transporting cystine out of lysosomes. Its deficiency leads to cystine accumulation and cell damage in multiple organs, especially in the kidney. In this study, we aimed to provide the first report describing the mutational spectrum of Egyptian patients with nephropathic Cystinosis and their genotype–phenotype correlation.
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Management of nephropathic Cystinosis
Expert Opinion on Orphan Drugs, 2013Co-Authors: Martine T. P Besouw, Francesco Emma, Elena LevtchenkoAbstract:Introduction: Cystinosis is a lysosomal storage disease caused by mutations in the CTNS gene (17p13), encoding the lysosomal cystine transporter cystinosin. Nephropathic Cystinosis is characterized by the development of generalized proximal tubular dysfunction during infancy or childhood, progressing towards end-stage renal disease around the age of 10 in untreated patients. Extrarenal organs including the eyes, thyroid gland, endocrine and exocrine pancreas, liver, muscles, central and peripheral nervous system are also affected by the disease, mostly at later age. The pathogenesis of Cystinosis is still incompletely understood. Treatment strategies are focused, on the one hand, on the replacement of renal losses and endocrine deficiencies and, on the other hand, on lowering cystine accumulation by the administration of cysteamine. Cysteamine is of major importance for protecting kidneys and extrarenal organs; however, this treatment is not curative and has multiple side effects thus hampering the compli...
Stephanie Cherqui - One of the best experts on this subject based on the ideXlab platform.
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dync1li2 regulates localization of the chaperone mediated autophagy receptor lamp2a and improves cellular homeostasis in Cystinosis
bioRxiv, 2020Co-Authors: Farhana Rahman, Stephanie Cherqui, Jinzhong Zhang, Jennifer L Johnson, Sergio D CatzAbstract:SUMMARY The dynein motor protein complex is required for retrograde transport but the functions of the intermediate-light chains that form the cargo-binding complex are not elucidated and the importance of individual subunits in the maintenance of cellular homeostasis is unknown. Here, using mRNA arrays and protein analysis, we show that the dynein subunit, intermediate chain 2 (DYNC1LI2) is downregulated in Cystinosis, a lysosomal storage disorder caused by genetic defects in the lysosomal cystine transporter, cystinosin. Reconstitution of the expression of DYNC1LI2 in Ctns-/- cells re-established endolysosomal dynamics. Defective vesicular trafficking in cystinotic cells was rescued by DYNC1LI2 expression which correlated with decreased endoplasmic reticulum stress manifested as decreased expression levels of the chaperone Grp78. Mitochondrial fragmentation in cystinotic fibroblasts was also rescued by DYNC1LI2. Survival of cystinotic cells to oxidative stress insult was increased by DYNC1LI2 reconstitution but not by its paralog DYNC1LI1, which also failed to decrease ER stress levels and mitochondrial fragmentation. Restoring DYNC1LI2 expression rescued the localization of the chaperone-mediated autophagy receptor, LAMP2A, and restored cellular homeostasis of cystinotic proximal tubule cells, the primary cell type affected in Cystinosis. DYNC1LI2 failed to rescue phenotypes in cystinotic cells when LAMP2A was downregulated or when co-expressed with dominant negative (DN) RAB7 or DN-RAB11, which regulate LAMP2A trafficking. DYNC1LI2 emerges as a new target to repair underlying trafficking and CMA defects in Cystinosis, a mechanism that is not restored by currently used lysosomal depletion therapies.
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Potential use of stem cells as a therapy for Cystinosis
Pediatric Nephrology, 2019Co-Authors: Celine J Rocca, Stephanie CherquiAbstract:Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders (LSDs). Initial symptoms of Cystinosis correspond to the renal Fanconi syndrome. Patients then develop chronic kidney disease and multi-organ failure due to accumulation of cystine in all tissue compartments. LSDs are commonly characterized by a defective activity of lysosomal enzymes. Hematopoietic stem and progenitor cell (HSPC) transplantation is a treatment option for several LSDs based on the premise that their progeny will integrate in the affected tissues and secrete the functional enzyme, which will be recaptured by the surrounding deficient cells and restore physiological activity. However, in the case of Cystinosis, the defective protein is a transmembrane lysosomal protein, cystinosin. Thus, cystinosin cannot be secreted, and yet, we showed that HSPC transplantation can rescue disease phenotype in the mouse model of Cystinosis. In this review, we are describing a different mechanism by which HSPC-derived cells provide cystinosin to diseased cells within tissues, and how HSPC transplantation could be an effective one-time treatment to treat Cystinosis but also other LSDs associated with a lysosomal transmembrane protein dysfunction.
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The renal Fanconi syndrome in Cystinosis: pathogenic insights and therapeutic perspectives
Nature Reviews Nephrology, 2017Co-Authors: Stephanie Cherqui, Pierre J. CourtoyAbstract:One of the first manifestations of Cystinosis is a renal Fanconi syndrome, characterized by severe dysfunction of proximal tubule cells. This Review describes the pathogenesis of renal Fanconi syndrome in Cystinosis, focusing on the importance of cystinosin in the maintenance of cellular homeostasis beyond its function in cystine transport. Cystinosis is a multi-systemic lysosomal storage disease caused by inactivating mutations in, or the absence of, the lysosomal membrane exporter for cystine, cystinosin; Cystinosis is the main cause of hereditary renal Fanconi syndrome Treatment with cysteamine efficiently depletes lysosomal cystine and delays progression to renal insufficiency; however, cysteamine does not reverse established renal Fanconi syndrome, indicating functions of cystinosin beyond cystine transport Insights from mechanistic studies suggest that the pathological mechanisms of Fanconi syndrome in Cystinosis are multifactorial, involving oxidative stress and impaired vesicular trafficking, autophagy, and mTORC1 and TFEB signalling Haematopoietic stem cell (HSC) transplantation ameliorates renal Fanconi syndrome in cystinotic mice; HSCs differentiate into macrophages that transfer cystinosin-bearing lysosomes into proximal tubule cells via tunnelling nanotubes that cross the tubular basement membrane Since tunnelling nanotubes contain donor-derived cytosol and carry all types of organelles, this mechanism should be generic and could be used to correct other genetic diseases that affect proximal tubule cells Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders. It is caused by a defect in the lysosomal cystine transporter, cystinosin, which results in an accumulation of cystine in all organs. Despite the ubiquitous expression of cystinosin, a renal Fanconi syndrome is often the first manifestation of Cystinosis, usually presenting within the first year of life and characterized by the early and severe dysfunction of proximal tubule cells, highlighting the unique vulnerability of this cell type. The current therapy for Cystinosis, cysteamine, facilitates lysosomal cystine clearance and greatly delays progression to kidney failure but is unable to correct the Fanconi syndrome. This Review summarizes decades of studies that have fostered a better understanding of the pathogenesis of the renal Fanconi syndrome associated with Cystinosis. These studies have unraveled some of the early molecular changes that occur before the onset of tubular atrophy and identified a role for cystinosin beyond cystine transport, in endolysosomal trafficking and proteolysis, lysosomal clearance, autophagy and the regulation of energy balance. These studies have also led to the identification of new potential therapeutic targets and here, we outline the potential role of stem cell therapy for Cystinosis and provide insights into the mechanism of haematopoietic stem cell-mediated kidney protection.
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the renal fanconi syndrome in Cystinosis pathogenic insights and therapeutic perspectives
Nature Reviews Nephrology, 2017Co-Authors: Stephanie Cherqui, Pierre J. CourtoyAbstract:Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders. It is caused by a defect in the lysosomal cystine transporter, cystinosin, which results in an accumulation of cystine in all organs. Despite the ubiquitous expression of cystinosin, a renal Fanconi syndrome is often the first manifestation of Cystinosis, usually presenting within the first year of life and characterized by the early and severe dysfunction of proximal tubule cells, highlighting the unique vulnerability of this cell type. The current therapy for Cystinosis, cysteamine, facilitates lysosomal cystine clearance and greatly delays progression to kidney failure but is unable to correct the Fanconi syndrome. This Review summarizes decades of studies that have fostered a better understanding of the pathogenesis of the renal Fanconi syndrome associated with Cystinosis. These studies have unraveled some of the early molecular changes that occur before the onset of tubular atrophy and identified a role for cystinosin beyond cystine transport, in endolysosomal trafficking and proteolysis, lysosomal clearance, autophagy and the regulation of energy balance. These studies have also led to the identification of new potential therapeutic targets and here, we outline the potential role of stem cell therapy for Cystinosis and provide insights into the mechanism of haematopoietic stem cell-mediated kidney protection.
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32 towards a phase i clinical trial for Cystinosis
Molecular Therapy, 2016Co-Authors: Tatiana Lobry, Celine J Rocca, Donald B Kohn, Jay Sharma, Athena Lau, Denise Carbonaro, Laura Hernandez, Stephanie CherquiAbstract:Cystinosis is an autosomal recessive lysosomal storage disorder characterized by the accumulation of cystine in the lysosomes leading to cystine crystals formation. The gene involved, CTNS, encodes a lysosomal cystine transporter, cystinosin. Cystinosis leads to a renal Fanconi's syndrome before the age of one characterized by polyuria and nutrients loss, and to multi-organ degeneration especially the eyes and kidneys. The cysteamine treatment allows the exit of cystine out of the lysosomes but only delays the evolution of the disease. We showed that transplantation of wild-type Hematopoietic Stem and Progenitor Cells (HSPCs) in a lethally irradiated Ctns−/− mouse leads to cystine content decrease in every tissues tested and kidney, eye and thyroid function and structure improvement in treated mice compared to mock-treated mice. An autologous HSPCs gene therapy approach has then been developed with Ctns−/− HSPCs gene-modified ex vivo to express a functional CTNS cDNA using the lentiviral vector pCCL-CTNS. Tissue cystine decrease and kidney function rescue were observed with this strategy. The toxicology and pharmacology studies required by the FDA are in progress with a targeted Vector Copy Number (VCN) included between 1 and 3. The in vitro studies, Colony Forming Unit assay and In Vitro Immortalization assay, have been completed using peripheral blood CD34+ cells from five healthy donors and four Cystinosis patients. The in vivo studies are in progress: Ctns−/− HSPCs are isolated and transduced with pCCL-CTNS and transplanted into primary Ctns−/− mice and 6-months later their bone marrow cells are transplanted into secondary Ctns−/− recipients. Primary and secondary mice are carefully monitored and comprehensive histological, biochemical, molecular and clinical analyses are performed at 6 months post-transplant. So far, seven primary and one secondary Ctns−/− mice transplanted with pCCL-CTNS-transduced Ctns−/− HSPCs have reached the 6 month post-transplantation time point. The primary mice had a mean VCN of 1.713 and the secondary 2.04. Clinical evaluations, histopathology and Vector Integration Site (VIS) analyses revealed no adverse event so far suggesting a good safety profile of our product. Moreover, cystine content was significantly decreased in all tissues tested. Analysis of the remaining primary and secondary recipient mice is in progress and these data will be included in an Investigational New Drug (IND) for a phase 1 clinical trial for autologous transplantation of pCCL-CTNS-modified CD34+ HSPCs in patients with nephropathic Cystinosis, For the design and conduct of the future clinical trial, the Cystinosis Stem Cell and Gene Therapy Consortium was recently created and is composed of experts in Cystinosis, bone marrow transplant and gene therapy. The clinical grade pCCL-CTNS virus preparation is about to be produced at the Gene Therapy Resources Program (GTRP), Clinical Grade Lentivirus Vector Core directed by Dr. Kenneth Cornetta who prepared the Good Manufactory Practice-comparable (GMPc) virus used for the pharmacology/toxicology studies. We are currently preparing the documents necessary for the IND such as the clinical protocol, the toxicology/pharmacology report, the Chemistry, Manufacturing and Controls (CMC) report, etc. This clinical trial will represent the first stem cell and gene therapy treatment strategy for Cystinosis.
Sergio D Catz - One of the best experts on this subject based on the ideXlab platform.
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dync1li2 regulates localization of the chaperone mediated autophagy receptor lamp2a and improves cellular homeostasis in Cystinosis
bioRxiv, 2020Co-Authors: Farhana Rahman, Stephanie Cherqui, Jinzhong Zhang, Jennifer L Johnson, Sergio D CatzAbstract:SUMMARY The dynein motor protein complex is required for retrograde transport but the functions of the intermediate-light chains that form the cargo-binding complex are not elucidated and the importance of individual subunits in the maintenance of cellular homeostasis is unknown. Here, using mRNA arrays and protein analysis, we show that the dynein subunit, intermediate chain 2 (DYNC1LI2) is downregulated in Cystinosis, a lysosomal storage disorder caused by genetic defects in the lysosomal cystine transporter, cystinosin. Reconstitution of the expression of DYNC1LI2 in Ctns-/- cells re-established endolysosomal dynamics. Defective vesicular trafficking in cystinotic cells was rescued by DYNC1LI2 expression which correlated with decreased endoplasmic reticulum stress manifested as decreased expression levels of the chaperone Grp78. Mitochondrial fragmentation in cystinotic fibroblasts was also rescued by DYNC1LI2. Survival of cystinotic cells to oxidative stress insult was increased by DYNC1LI2 reconstitution but not by its paralog DYNC1LI1, which also failed to decrease ER stress levels and mitochondrial fragmentation. Restoring DYNC1LI2 expression rescued the localization of the chaperone-mediated autophagy receptor, LAMP2A, and restored cellular homeostasis of cystinotic proximal tubule cells, the primary cell type affected in Cystinosis. DYNC1LI2 failed to rescue phenotypes in cystinotic cells when LAMP2A was downregulated or when co-expressed with dominant negative (DN) RAB7 or DN-RAB11, which regulate LAMP2A trafficking. DYNC1LI2 emerges as a new target to repair underlying trafficking and CMA defects in Cystinosis, a mechanism that is not restored by currently used lysosomal depletion therapies.
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interaction between galectin 3 and cystinosin uncovers a pathogenic role of inflammation in kidney involvement of Cystinosis
Kidney International, 2019Co-Authors: Tatiana Lobry, Roy Miller, Nathalie Nevo, Celine J Rocca, Jinzhong Zhang, Sergio D Catz, Fiona Moore, Lucie ThomasAbstract:Inflammation is involved in the pathogenesis of many disorders. However, the underlying mechanisms are often unknown. Here, we test whether cystinosin, the protein involved in Cystinosis, is a critical regulator of galectin-3, a member of the β-galactosidase binding protein family, during inflammation. Cystinosis is a lysosomal storage disorder and, despite ubiquitous expression of cystinosin, the kidney is the primary organ impacted by the disease. Cystinosin was found to enhance lysosomal localization and degradation of galectin-3. In Ctns-/- mice, a mouse model of Cystinosis, galectin-3 is overexpressed in the kidney. The absence of galectin-3 in cystinotic mice ameliorates pathologic renal function and structure and decreases macrophage/monocyte infiltration in the kidney of the Ctns-/-Gal3-/- mice compared to Ctns-/- mice. These data strongly suggest that galectin-3 mediates inflammation involved in kidney disease progression in Cystinosis. Furthermore, galectin-3 was found to interact with the pro-inflammatory cytokine Monocyte Chemoattractant Protein-1, which stimulates the recruitment of monocytes/macrophages, and proved to be significantly increased in the serum of Ctns-/- mice and also patients with Cystinosis. Thus, our findings highlight a new role for cystinosin and galectin-3 interaction in inflammation and provide an additional mechanistic explanation for the kidney disease of Cystinosis. This may lead to the identification of new drug targets to delay Cystinosis progression.
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Video_2_Chaperone-Mediated Autophagy Upregulation Rescues Megalin Expression and Localization in Cystinotic Proximal Tubule Cells.AVI
2019Co-Authors: Jinzhong Zhang, Jennifer L Johnson, Farhana Rahman, Evripidis Gavathiotis, Ana Maria Cuervo, Sergio D CatzAbstract:Cystinosis is a lysosomal storage disorder caused by defects in CTNS, the gene that encodes the lysosomal cystine transporter cystinosin. Patients with nephropathic Cystinosis are characterized by endocrine defects, defective proximal tubule cell (PTC) function, the development of Fanconi syndrome and, eventually, end-stage renal disease. Kidney disease is developed despite the use of cysteamine, a drug that decreases lysosomal cystine overload but fails to correct overload-independent defects. Chaperone-mediated autophagy (CMA), a selective form of autophagy, is defective in cystinotic mouse fibroblasts, and treatment with cysteamine is unable to correct CMA defects in vivo, but whether the vesicular trafficking mechanisms that lead to defective CMA in Cystinosis are manifested in human PTCs is not currently known and whether PTC-specific mechanisms are corrected upon CMA upregulation remains to be elucidated. Here, using CRISPR-Cas9 technology, we develop a new human PTC line with defective cystinosin expression (CTNS-KO PTCs). We show that the expression and localization of the CMA receptor, LAMP2A, is defective in CTNS-KO PTCs. The expression of the lipidated form of LC3B, a marker for another form of autophagy (macroautophagy), is decreased in CTNS-KO PTCs indicating decreased autophagosome numbers under basal conditions. However, the autophagic flux is functional, as measured by induction by starvation or by blockage using the v-ATPase inhibitor bafilomycin A, and by degradation of the macroautophagy substrate SQSTM1 under starvation and proteasome-inhibited conditions. Previous studies showed that LAMP2A accumulates in Rab11-positive vesicles in cystinotic cells. Here, we show defective Rab11 expression, localization and trafficking in CTNS-KO PTCs as determined by confocal microscopy, immunoblotting and TIRFM. We also show that both Rab11 expression and trafficking in cystinotic PTCs are rescued by the upregulation of CMA using small-molecule CMA activators. Cystinotic PTCs are characterized by PTC de-differentiation accompanied by loss of the endocytic receptor megalin, and megalin recycling is regulated by Rab11. Here we show that megalin plasma membrane localization is defective in CTNS-KO PTCs and its expression is rescued by treatment with CMA activators. Altogether, our data support that CMA upregulation has the potential to improve PTC function in Cystinosis.
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Chaperone-Mediated Autophagy Upregulation Rescues Megalin Expression and Localization in Cystinotic Proximal Tubule Cells
Frontiers Media S.A., 2019Co-Authors: Jinzhong Zhang, Jennifer L Johnson, Farhana Rahman, Evripidis Gavathiotis, Ana Maria Cuervo, Sergio D CatzAbstract:Cystinosis is a lysosomal storage disorder caused by defects in CTNS, the gene that encodes the lysosomal cystine transporter cystinosin. Patients with nephropathic Cystinosis are characterized by endocrine defects, defective proximal tubule cell (PTC) function, the development of Fanconi syndrome and, eventually, end-stage renal disease. Kidney disease is developed despite the use of cysteamine, a drug that decreases lysosomal cystine overload but fails to correct overload-independent defects. Chaperone-mediated autophagy (CMA), a selective form of autophagy, is defective in cystinotic mouse fibroblasts, and treatment with cysteamine is unable to correct CMA defects in vivo, but whether the vesicular trafficking mechanisms that lead to defective CMA in Cystinosis are manifested in human PTCs is not currently known and whether PTC-specific mechanisms are corrected upon CMA upregulation remains to be elucidated. Here, using CRISPR-Cas9 technology, we develop a new human PTC line with defective cystinosin expression (CTNS-KO PTCs). We show that the expression and localization of the CMA receptor, LAMP2A, is defective in CTNS-KO PTCs. The expression of the lipidated form of LC3B, a marker for another form of autophagy (macroautophagy), is decreased in CTNS-KO PTCs indicating decreased autophagosome numbers under basal conditions. However, the autophagic flux is functional, as measured by induction by starvation or by blockage using the v-ATPase inhibitor bafilomycin A, and by degradation of the macroautophagy substrate SQSTM1 under starvation and proteasome-inhibited conditions. Previous studies showed that LAMP2A accumulates in Rab11-positive vesicles in cystinotic cells. Here, we show defective Rab11 expression, localization and trafficking in CTNS-KO PTCs as determined by confocal microscopy, immunoblotting and TIRFM. We also show that both Rab11 expression and trafficking in cystinotic PTCs are rescued by the upregulation of CMA using small-molecule CMA activators. Cystinotic PTCs are characterized by PTC de-differentiation accompanied by loss of the endocytic receptor megalin, and megalin recycling is regulated by Rab11. Here we show that megalin plasma membrane localization is defective in CTNS-KO PTCs and its expression is rescued by treatment with CMA activators. Altogether, our data support that CMA upregulation has the potential to improve PTC function in Cystinosis
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impairment of chaperone mediated autophagy leads to selective lysosomal degradation defects in the lysosomal storage disease Cystinosis
Embo Molecular Medicine, 2015Co-Authors: Gennaro Napolitano, Stephanie Cherqui, Celine J Rocca, Jennifer L Johnson, Jlenia Monfregola, Kersi Pestonjamasp, Sergio D CatzAbstract:Metabolite accumulation in lysosomal storage disorders (LSDs) results in impaired cell function and multi-systemic disease. Although substrate reduction and lysosomal overload-decreasing therapies can ameliorate disease progression, the significance of lysosomal overload-independent mechanisms in the development of cellular dysfunction is unknown for most LSDs. Here, we identify a mechanism of impaired chaperone-mediated autophagy (CMA) in Cystinosis, a LSD caused by defects in the cystine transporter cystinosin (CTNS) and characterized by cystine lysosomal accumulation. We show that, different from other LSDs, autophagosome number is increased, but macroautophagic flux is not impaired in Cystinosis while mTOR activity is not affected. Conversely, the expression and localization of the CMA receptor LAMP2A are abnormal in CTNS-deficient cells and degradation of the CMA substrate GAPDH is defective in Ctns(-/-) mice. Importantly, cysteamine treatment, despite decreasing lysosomal overload, did not correct defective CMA in Ctns(-/-) mice or LAMP2A mislocalization in cystinotic cells, which was rescued by CTNS expression instead, suggesting that cystinosin is important for CMA activity. In conclusion, CMA impairment contributes to cell malfunction in Cystinosis, highlighting the need for treatments complementary to current therapies that are based on decreasing lysosomal overload.
Mohamed A Elmonem - One of the best experts on this subject based on the ideXlab platform.
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molecular basis of Cystinosis geographic distribution functional consequences of mutations in the ctns gene and potential for repair
Nephron, 2019Co-Authors: Dries David, Sante Princiero Berlingerio, Mohamed A Elmonem, Fanny Oliveira Arcolino, Neveen A Soliman, Bert Van Den Heuvel, Rik Gijsbers, Elena LevtchenkoAbstract:Mutations in the CTNS gene encoding the lysosomal membrane cystine transporter cystinosin are the cause of Cystinosis, an autosomal recessive lysosomal storage disease. More than 140 CTNS mutations have been reported worldwide. Recent studies have discovered that cystinosin exerts other key cellular functions beyond cystine transport such as regulation of oxidative state, lysosomal dynamics and autophagy. Here, we review the different mutations described in the CTNS gene and the geographical distribution of incidence. In addition, the characteristics of the various mutations in relation to the functions of cystinosin needs to be further elucidated. In this review, we highlight the functional consequences of the different mutations in correlation with the clinical phenotypes. Moreover, we propose how this understanding would be fundamental for the development of new technologies through targeted gene therapy, holding promises for a possible cure of the kidney and extra-renal phenotypes of Cystinosis.
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Cystinosis ctns zebrafish mutant shows pronephric glomerular and tubular dysfunction
Scientific Reports, 2017Co-Authors: Mohamed A Elmonem, Fanny Oliveira Arcolino, Anna Pastore, Ramzi Khalil, Ladan Khodaparast, Laleh Khodaparast, Joseph Morgan, Przemko Tylzanowski, Martin LoweAbstract:The human ubiquitous protein cystinosin is responsible for transporting the disulphide amino acid cystine from the lysosomal compartment into the cytosol. In humans, Pathogenic mutations of CTNS lead to defective cystinosin function, intralysosomal cystine accumulation and the development of Cystinosis. Kidneys are initially affected with generalized proximal tubular dysfunction (renal Fanconi syndrome), then the disease rapidly affects glomeruli and progresses towards end stage renal failure and multiple organ dysfunction. Animal models of Cystinosis are limited, with only a Ctns knockout mouse reported, showing cystine accumulation and late signs of tubular dysfunction but lacking the glomerular phenotype. We established and characterized a mutant zebrafish model with a homozygous nonsense mutation (c.706 C > T; p.Q236X) in exon 8 of ctns. Cystinotic mutant larvae showed cystine accumulation, delayed development, and signs of pronephric glomerular and tubular dysfunction mimicking the early phenotype of human cystinotic patients. Furthermore, cystinotic larvae showed a significantly increased rate of apoptosis that could be ameliorated with cysteamine, the human cystine depleting therapy. Our data demonstrate that, ctns gene is essential for zebrafish pronephric podocyte and proximal tubular function and that the ctns-mutant can be used for studying the disease pathogenic mechanisms and for testing novel therapies for Cystinosis.
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Cystinosis: a review
Orphanet journal of rare diseases, 2016Co-Authors: Mohamed A Elmonem, Koenraad Veys, Neveen A Soliman, Lambertus P Van Den Heuvel, Maria Van Dyck, Elena LevtchenkoAbstract:Cystinosis is the most common hereditary cause of renal Fanconi syndrome in children. It is an autosomal recessive lysosomal storage disorder caused by mutations in the CTNS gene encoding for the carrier protein cystinosin, transporting cystine out of the lysosomal compartment. Defective cystinosin function leads to intra-lysosomal cystine accumulation in all body cells and organs. The kidneys are initially affected during the first year of life through proximal tubular damage followed by progressive glomerular damage and end stage renal failure during mid-childhood if not treated. Other affected organs include eyes, thyroid, pancreas, gonads, muscles and CNS. Leucocyte cystine assay is the cornerstone for both diagnosis and therapeutic monitoring of the disease. Several lines of treatment are available for Cystinosis including the cystine depleting agent cysteamine, renal replacement therapy, hormonal therapy and others; however, no curative treatment is yet available. In the current review we will discuss the most important clinical features of the disease, advantages and disadvantages of the current diagnostic and therapeutic options and the main topics of future research in Cystinosis.
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altered mtor signalling in nephropathic Cystinosis
Journal of Inherited Metabolic Disease, 2016Co-Authors: Ekaterina A Ivanova, Mohamed A Elmonem, Lambertus P Van Den Heuvel, Humbert De Smedt, Ludwig Missiaen, Anna Pastore, Djalila Mekahli, Greet BultynckAbstract:Lysosomes play a central role in regulating autophagy via activation of mammalian target of rapamycin complex 1 (mTORC1). We examined mTORC1 signalling in the lysosomal storage disease nephropathic Cystinosis (MIM 219800), in which accumulation of autophagy markers has been previously demonstrated. Cystinosis is caused by mutations in the lysosomal cystine transporter cystinosin and initially affects kidney proximal tubules causing renal Fanconi syndrome, followed by a gradual development of end-stage renal disease and extrarenal complications. Using proximal tubular kidney cells obtained from healthy donors and from cystinotic patients, we demonstrate that cystinosin deficiency is associated with a perturbed mTORC1 signalling, delayed reactivation of mTORC1 after starvation and abnormal lysosomal retention of mTOR during starvation. These effects could not be reversed by treatment with cystine-depleting drug cysteamine. Altered mTORC1 signalling can contribute to the development of proximal tubular dysfunction in Cystinosis and points to new possibilities in therapeutic intervention through modulation of mTORC-dependent signalling cascades.
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mutational spectrum of the ctns gene in egyptian patients with nephropathic Cystinosis
JIMD Reports, 2014Co-Authors: Neveen A Soliman, Mohamed A Elmonem, Lambertus P Van Den Heuvel, Rehab Abdel H Hamid, Mohamed A Gamal, Inge Bongaers, Sandrine Marie, Elena LevtchenkoAbstract:Background: Nephropathic Cystinosis is a rare autosomal recessive disorder caused by mutations in the CTNS gene, encoding for cystinosin, a carrier protein transporting cystine out of lysosomes. Its deficiency leads to cystine accumulation and cell damage in multiple organs, especially in the kidney. In this study, we aimed to provide the first report describing the mutational spectrum of Egyptian patients with nephropathic Cystinosis and their genotype–phenotype correlation.
Corinne Antignac - One of the best experts on this subject based on the ideXlab platform.
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Impact of cystinosin glycosylation on protein stability by differential dynamic SILAC
Molecular and Cellular Proteomics, 2017Co-Authors: Nathalie Nevo, A. Bailleux, Lucie Thomas, Corinne Antignac, Cerina Chhuon, Zuzanna Andrzejewska, Joanna Lipecka, François Guillonneau, Aleksander Edelman, Ida Chiara GuerreraAbstract:Cystinosis is a rare autosomal recessive lysosomal storage disorder characterized by intralysosomal accumulation of cystine. The causative gene for Cystinosis is CTNS, which encodes the protein cystinosin, a lysosomal proton-driven cystine transporter. Over 100 mutations have been reported, leading to varying disease severity, often in correlation with residual cystinosin activity as a transporter and with maintenance of its protein-protein interactions. In this study, we focus on the ΔITILELP mutation, the only mutation reported that sometimes leads to severe forms, inconsistent with its residual transported activity. ΔITILELP is a deletion that eliminates a consensus site on N66, one of the protein seven glycosylation sites. Our hypothesis was that the ΔITILELP mutant is less stable and undergoes faster degradation. Our dynamic SILAC study clearly showed that wild-type cystinosin is very stable, while ΔITILELP is degraded three times more rapidly. Additional lysosome inhibition experiments confirmed ΔITILELP instability and showed that the degradation was mainly lysosomal. We observed that in the lysosome, ΔITILELP is still capable of interacting with the V-ATPase complex and some members of the mTOR pathway, similar to the wild-type protein. Intriguingly, our interactomic and immunofluorescence studies showed that ΔITILELP is partially retained at the endoplasmic reticulum (ER). We proposed that the ΔITILELP mutation causes protein misfolding, ER retention and inability to be processed in the Golgi apparatus, and we demonstrated that ΔITILELP carries high-mannose glycans on all six of its remaining glycosylation sites. We found that the high turnover of ΔITILELP, due to its immature glycosylation state in combination with low transport activity, might be responsible for the phenotype observed in some patients. Data are available via ProteomeXchange with identifier PXD004948, PXD005357 and on Panorama Public at https://panoramaweb.org/labkey/Guerrera.url.
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a mouse model suggests two mechanisms for thyroid alterations in infantile Cystinosis decreased thyroglobulin synthesis due to endoplasmic reticulum stress unfolded protein response and impaired lysosomal processing
Endocrinology, 2015Co-Authors: H Gaide P Chevronnay, Stephanie Cherqui, Nathalie Nevo, Corinne Antignac, Virginie Janssens, P Van Der Smissen, Xiao Hui Liao, Y Abid, Samuel Refetoff, Christophe E PierreuxAbstract:Thyroid hormones are released from thyroglobulin (Tg) in lysosomes, which are impaired in infantile/nephropathic Cystinosis. Cystinosis is a lysosomal cystine storage disease due to defective cystine exporter, cystinosin. Cystinotic children develop subclinical and then overt hypothyroidism. Why hypothyroidism is the most frequent and earliest endocrine complication of Cystinosis is unknown. We here defined early alterations in Ctns−/− mice thyroid and identified subcellular and molecular mechanisms. At 9 months, T4 and T3 plasma levels were normal and TSH was moderately increased (∼4-fold). By histology, hyperplasia and hypertrophy of most follicles preceded colloid exhaustion. Increased immunolabeling for thyrocyte proliferation and apoptotic shedding indicated accelerated cell turnover. Electron microscopy revealed endoplasmic reticulum (ER) dilation, apical lamellipodia indicating macropinocytic colloid uptake, and lysosomal cystine crystals. Tg accumulation in dilated ER contrasted with mRNA down-reg...
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dedifferentiation and aberrations of the endolysosomal compartment characterize the early stage of nephropathic Cystinosis
Human Molecular Genetics, 2014Co-Authors: Claudia Raggi, O. Devuyst, Nathalie Nevo, Corinne Antignac, Alessandro Luciani, Sara TerrynAbstract:Nephropathic Cystinosis, a lysosomal storage disease caused by mutations in the CTNS gene encoding the lysosomal cystine transporter cystinosin, is characterized by generalized proximal tubule (PT) dysfunction that progresses, if untreated, to end-stage renal disease. The pathogenesis of defective PT cellular transport in nephropathic Cystinosis remains unclear. We characterized a recently generated line of C57BL/6 Ctns mice and analyzed endocytic uptake, lysosome function, and dedifferentiation and proliferation markers using primary cultures of PT epithelial cells derived from Ctns(-/-) and Ctns(+/+) littermates. Metabolic studies revealed that Ctns(-/-) mice show a progressive PT dysfunction characterized by low-molecular-weight (LMW) proteinuria, glucosuria and phosphaturia, before structural damage and in the absence of renal failure. These changes are related to decreased expression of the multi-ligand receptors megalin and cubilin and to increased dedifferentiation (ZONAB transcription factor) and proliferation (PCNA and Cyclin D1) rates. Studies on PT cells derived from Ctns(-/-) kidneys confirmed cystine overload, with accumulation of enlarged, dysfunctional lysosomes and reduced expression of endocytic receptors reflected by decreased uptake of specific ligands. These changes were related to a loss of integrity of tight junctions with a nuclear translocation of ZONAB and increased proliferation, as observed in Ctns(-/-) kidneys. These data reveal that the absence of cystinosin in PT cells triggers aberrations of the endolysosomal compartment, transport defects and an abnormal transcription program in the early stage of nephropathic Cystinosis. Insights into the early manifestations of Cystinosis may offer new targets for intervention, before irreversible renal damage.
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Chapter 39 – Hereditary Cystinosis
Genetic Diseases of the Kidney, 2009Co-Authors: V. Kalatzis, Corinne AntignacAbstract:Publisher Summary This chapter reviews the most recent advances in the molecular biology of Cystinosis, focuses on the causative CTNSmutations identified to date, and explains a correlation between genotype and the differing clinical phenotypes. Cystinosis is a rare autosomal recessive monogenic disorder with an incidence of ~1/200,000 live births, characterized by an intralysosomal accumulation of cystine. It constitutes the most common familial form of the renal Fanconi syndrome. The underlying metabolic defect of Cystinosis is an accumulation of cystine in the lysosomes. Cystine, the disulfide of the amino acid cysteine, is a by-product of lysosomal protein hydrolysis, and is reduced to cysteine in the cytoplasm. Lysosome hydrolases, responsible for the digestion of macromolecules, have optimal activity at acid pH and the acidification of the lysosomal lumen is accomplished by the presence of an ATPase H+-pump in its membrane. In the case of Cystinosis, the lysosomal cystine transporter is defective leading to an abnormal storage of cystine. It is due to its poor solubility that cystine forms crystals as its concentration increases. A measure of leukocyte cystine levels using a cystine binding protein assay is generally used to confirm a suspicion of Cystinosis. Oral cysteamine therapy, if administered early in the course of the disease and in high doses, delays the progression of renal insufficiency. In addition, it prevents the appearance of hypothyroidism, and decreases the severity of oral motor and swallowing dysfunction, which is correlated with generalized muscle atrophy. Approximately 90 different CTNSmutations have been detected in all forms of Cystinosis up to now. Many of the point mutations associated with the infantile form are deletions, insertions, and splice site mutations that cause premature termination of cystinosin.
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The Ocular Anomalies in a Cystinosis Animal Model Mimic Disease Pathogenesis
Pediatric Research, 2007Co-Authors: V. Kalatzis, Nicolas Serratrice, Claire Hippert, Olivier Payet, Carl Arndt, Chantal Cazevieille, Tangui Maurice, Christian Hamel, François Malecaze, Corinne AntignacAbstract:Cystinosis is a lysosomal storage disorder characterized by abnormal accumulation of cystine, which forms crystals at high concentrations. The causative gene CTNS encodes cystinosin, the lysosomal cystine transporter. The eye is one of the first organs affected (corneal lesions and photophobia in the first and visual impairment in the second decade of life). We characterized the ocular anomalies of Ctns ^−/− mice to determine whether they mimic those of patients. The most dramatic cystine accumulation was seen in the iris, ciliary body, and cornea of Ctns ^−/− mice. Consistently, Ctns ^−/− mice had a low intraocular pressure (IOP) and seemed mildly photophobic. Retinal cystine levels were elevated but increased less dramatically with age. Consistently, the retina was intact and electroretinogram (ERG) profiles were normal in mice younger than 19 mo; beyond this age, retinal crystals and lesions appeared. Finally, the lens contained the lowest cystine levels and crystals were not seen. The temporospatial pattern of cystine accumulation in Ctns ^−/− mice parallels that of patients and validates the mice as a model for the ocular anomalies of Cystinosis. This work is a prerequisite step to the testing of novel ocular cystine-depleting therapies.
