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Pennesi M, Marchetti F, Crovella S, Boaretto F, Travan L, Lazzerini M, Neri E, Ventura A. A new mutation in two siblings with cystinosis presenting with Bartter syndrome. Pediatr Nephrol 2005; 20:217-9. [PMID: 15583946 DOI: 10.1007/s00467-004-1702-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2004] [Revised: 09/13/2004] [Accepted: 09/14/2004] [Indexed: 01/28/2023]
Abstract
Nephropathic cystinosis is a severe autosomal recessive inherited metabolic disease characterized by accumulation of free cystine in lysosomes. Cystinosis can lead to renal failure and multiorgan impairment. Only five cases of cystinosis with associated Bartter syndrome are reported in the literature, and no genetic evaluation has been reported. We describe two siblings with nephropathic cystinosis presenting with features of Bartter syndrome and their genetic pattern.
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Chol M, Nevo N, Cherqui S, Antignac C, Rustin P. Glutathione precursors replenish decreased glutathione pool in cystinotic cell lines. Biochem Biophys Res Commun 2004; 324:231-5. [PMID: 15465007 DOI: 10.1016/j.bbrc.2004.09.033] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2004] [Indexed: 12/13/2022]
Abstract
Cystinosis is an inherited disorder due to mutations in the CTNS gene which encodes cystinosin, a lysosomal transmembrane protein involved in cystine export to the cytosol. Both accumulation of cystine in the lysosome and decreased cystine in the cytosol may participate in the pathogenic mechanism underlying the disease. We observed that cystinotic cell lines have moderate decrease of glutathione content during exponential growth phase. This resulted in increased solicitation of oxidative defences of the cell denoted by concurrent superoxide dismutase induction, although without major oxidative insult under our experimental conditions. Finally, decreased glutathione content in cystinotic cell lines could be counterbalanced by a series of exogenous precursors of cysteine, denoting that lysosomal cystine export is a natural source of cellular cysteine in the studied cell lines.
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Bendavid C, Kleta R, Long R, Ouspenskaia M, Muenke M, Haddad BR, Gahl WA. FISH diagnosis of the common 57-kb deletion in CTNS causing cystinosis. Hum Genet 2004; 115:510-4. [PMID: 15365816 DOI: 10.1007/s00439-004-1170-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2004] [Accepted: 06/21/2004] [Indexed: 01/28/2023]
Abstract
Cystinosis is an autosomal recessive lysosomal storage disease caused by mutations in CTNS. The most prevalent CTNS mutation, a 57-kb deletion, occurs in approximately 60% of patients in the United States and northern Europe and removes exons 1-9, most of exon 10, the CTNS promoter region, and all of an adjacent gene of unknown function called CARKL. CTNS codes for the lysosomal cystine transporter, whose absence leads to intracellular cystine accumulation, widespread cellular destruction, renal Fanconi syndrome in infancy, renal glomerular failure in later childhood, and other systemic complications. Because treatment with oral cysteamine can prevent or delay these complications significantly, early and accurate diagnosis is critical. This study describes the generation of fluorescence in situ hybridization (FISH) probes for the 57-kb deletion in CTNS, enabling cytogenetics laboratories to test for this common mutation. The probes would also be able to detect a less frequent 11.7-kb deletion. A blinded study was performed using multiplex PCR analysis as the gold standard to determine the presence or absence of the 57-kb deletion. The FISH probes, evaluated on 12 lymphoblastoid cell lines from singly deleted, doubly deleted, and nondeleted patients, made the correct diagnosis in every case. This appears to be the first FISH-based diagnostic method described for any lysosomal storage disorder. It can assist in the antenatal and perinatal diagnosis of cystinosis and promote earlier salutary therapy with cysteamine.
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Pintos Morell G. Cistinosis: acumulación de cistina por defecto de transporte translisosomal. Med Clin (Barc) 2004; 123:95-6. [PMID: 15225474 DOI: 10.1016/s0025-7753(04)74424-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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55
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Quinn JP, Royston D, Murphy PT. Bone marrow findings in hereditary cystinosis with renal failure. Am J Hematol 2004; 76:79. [PMID: 15114603 DOI: 10.1002/ajh.20040] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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56
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Middleton R, Bradbury M, Webb N, O'Donoghue D, Van't Hoff W. Cystinosis. A clinicopathological conference. "From toddlers to twenties and beyond" Adult-Paediatric Nephrology Interface Meeting, Manchester 2001. Nephrol Dial Transplant 2004; 18:2492-5. [PMID: 14605270 DOI: 10.1093/ndt/gfg445] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Abstract
This paper gives an overview of the two sialic acid storage disorders, Salla disease and infantile sialic acid storage disease, and the related disorders cystinosis, sialuria, sialidosis, and galactosialidosis. Sialic acid storage disease and cystinosis are models for a deficient lysosomal transport of monosaccharides and amino acids, respectively. Several gene mutations leading to the production of the faulty membrane proteins sialin and cystinosin have been identified in recent years. Knowledge of the underlying pathophysiology is a prerequisite for future research projects, which will focus on the expression of the disease genes in living systems and the physical characterization of these proteins by X-ray crystallography and nuclear magnetic resonance spectroscopy.
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Levtchenko EN, Wilmer M, de Graaf-Hess AC, van den Heuvel LP, Blom H, Monnens LA. [From gene to disease: cystinosis]. NEDERLANDS TIJDSCHRIFT VOOR GENEESKUNDE 2004; 148:476-8. [PMID: 15042893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Cystinosis is an autosomal recessive disorder caused by an impaired transport of cystine out of lysosomes. The most severe infantile form of cystinosis starts with Fanconi syndrome at the age of 3-6 months. Untreated patients develop renal failure before the age of 10. The cystinosis gene (CTNS) maps to chromosome 17p13, spans 23 kb and is composed of 12 exons. CTNS encodes a 367 amino acid protein, cystinosin, which is a H(+)-driven lysosomal cystine transporter. It is enigmatic how lysosomal cystine accumulation induces the clinical symptoms. ATP depletion was demonstrated in an experimental model consisting of loading lysosomes with cystine dimethylester. The amino-thiol cysteamine depletes lysosomal cystine content by a disulfide-exchange reaction with cystine. Therapy with cysteamine should be administered as early as possible and continued after a renal transplantation as the extra renal damage still progresses. Improved life expectancy of cystinotic patients requires the attention of internists with a special interest for this rare disorder.
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Nuutinen M. [Cystinosis--a treatable disease due to defective lysosomal transporter protein]. DUODECIM; LAAKETIETEELLINEN AIKAKAUSKIRJA 2004; 120:593-8. [PMID: 15060996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
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Mason S, Pepe G, Dall'Amico R, Tartaglia S, Casciani S, Greco M, Bencivenga P, Murer L, Rizzoni G, Tenconi R, Clementi M. Mutational spectrum of the CTNS gene in Italy. Eur J Hum Genet 2003; 11:503-8. [PMID: 12825071 DOI: 10.1038/sj.ejhg.5200993] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Classic nephropathic or infantile cystinosis (NC) is an autosomal recessive disorder; the gene coding for the integral membrane protein cystinosin, which is responsible for membrane transport of cystine (CTNS), was cloned. Mutation analysis of the CTNS gene of Caucasian patients revealed a common 57-kb deletion, and several other mutations spread throughout the entire gene. In the present study, we report the CTNS mutations identified in 42 of 46 Italian families with NC. The percentage of mutations characterized in this study is 86%. The mutational spectrum of the Italian population is different from that of populations of North European origin: the 57-kb deletion is present in a lower percentage, while the splicing mutations represent 30% of mutation detected in our sample. In all, six novel mutations have been identified, and the origin of one recurrent mutation has been traced.
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61
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Pintos G. [Cystinosis: from cystine crystals to the cystinosin]. Nefrologia 2003; 23 Suppl 1:60-70. [PMID: 12708365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023] Open
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Eskelinen EL, Tanaka Y, Saftig P. At the acidic edge: emerging functions for lysosomal membrane proteins. Trends Cell Biol 2003; 13:137-45. [PMID: 12628346 DOI: 10.1016/s0962-8924(03)00005-9] [Citation(s) in RCA: 462] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
It has recently become clear that lysosomes have more complex functions than simply being the end-point on a degradative pathway. Similarly, it is now emerging that there are interesting functions for the limiting membranes around these organelles and their associated proteins. Although it has been known for several decades that the lysosomal membrane contains several highly N-glycosylated proteins, including the lysosome-associated membrane proteins LAMP-1 and LAMP-2 and lysosomal integral membrane protein-2/lysosomal membrane glycoprotein-85 (LIMP-2/LGP85), specific functions of these proteins have only recently begun to be recognized. Although the normal functions of LAMP-1 can be substituted by the structurally related LAMP-2, LAMP-2 itself has more specific tasks. Knockout of LAMP-2 in mice has revealed roles for LAMP-2 in lysosomal enzyme targeting, autophagy and lysosomal biogenesis. LAMP-2 deficiency in humans leads to Danon disease, a fatal cardiomyopathy and myopathy. Furthermore, there is evidence that LAMP-2 functions in chaperone-mediated autophagy. LIMP-2/LGP85 also seems to have specific functions in maintaining endosomal transport and lysosomal biogenesis. The pivotal function of lysosomal membrane proteins is also highlighted by the recent identification of disease-causing mutations in cystine and sialic acid transporter proteins, leading to nephropathic cystinosis and Salla disease.
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Kalatzis V, Antignac C. New aspects of the pathogenesis of cystinosis. Pediatr Nephrol 2003; 18:207-15. [PMID: 12644911 DOI: 10.1007/s00467-003-1077-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2002] [Revised: 11/04/2002] [Accepted: 11/08/2002] [Indexed: 10/25/2022]
Abstract
Cystinosis is a lysosomal transport disorder characterized by an intra-lysosomal accumulation of cystine, the disulfide of the amino acid cysteine. It is the most common inherited cause of the renal Fanconi syndrome. There are various clinical forms, infantile, juvenile, and ocular, based on age of onset and severity of symptoms. The first clinical description appeared in the early 1900s, but it was not until 1998 that the causative gene, CTNS, was identified. CTNS encodes cystinosin, a novel seven transmembrane domain (TM) protein. Cystinosin is a lysosomal membrane protein that requires two lysosomal targeting signals: a classic GYDQL motif in its C-terminal tail and a novel conformational motif, the core of which is YFPQA, situated in the fifth inter-TM loop. Cystinosin is the lysosomal cystine transporter and its activity is H(+)-driven. A mouse model of cystinosis was recently generated and Ctns(-/-) mice accumulate cystine in all tissues. A high level of cystine accumulates in the kidney, but these mice do not present with proximal tubulopathy or renal dysfunction. The Ctns(-/-) mouse model may provide clues to the cause of the Fanconi syndrome associated with cystinosis, the origin of which remains poorly understood.
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Kalatzis V, Cohen-Solal L, Cordier B, Frishberg Y, Kemper M, Nuutinen EM, Legrand E, Cochat P, Antignac C. Identification of 14 novel CTNS mutations and characterization of seven splice site mutations associated with cystinosis. Hum Mutat 2002; 20:439-46. [PMID: 12442267 DOI: 10.1002/humu.10141] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cystinosis is an autosomal recessive disorder characterized by intra-lysosomal accumulation of cystine. Three disease forms exist, infantile, juvenile, and ocular nonnephropathic cystinosis, delineated on the basis of severity of symptoms and age of onset. Mutations in the causative gene, CTNS, which encodes cystinosin, the seven transmembrane domain lysosomal cystine transporter, have been identified in all forms confirming their allelic status. By screening for mutations in the CTNS exons and promotor region, we report 14 novel mutations associated with cystinosis: 11 underlying infantile cystinosis, two juvenile cystinosis, and one associated with an atypical form of the disease. These mutations, all situated in the exons or immediately flanking intronic sequences, comprise in-frame insertions and deletions, as well as missense, nonsense, and putative splice-site mutations. Furthermore, we confirmed the putative splice-site mutations we have reported to date (five novel and two previously reported) by isolation of RNA from the affected carriers and characterization of the resultant transcripts using RT-PCR. Since the cloning of CTNS, we have screened for mutations in 108 affected individuals, which has resulted in a high mutation detection rate of 95.8%. Interestingly, the few undetectable mono- or bi-allelic mutations segregated mostly in the noninfantile forms, suggesting that these individuals carry mutations either in the introns or in unidentified regulatory sequences.
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65
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Dixit MP, Greifer I. Nephropathic cystinosis associated with cardiomyopathy: a 27-year clinical follow-up. BMC Nephrol 2002; 3:8. [PMID: 12425721 PMCID: PMC137602 DOI: 10.1186/1471-2369-3-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2002] [Accepted: 11/09/2002] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Nephropathic cystinosis is an autosomal recessive disease resulting from intracellular accumulation of cystine leading to multiple organ failure. CASE REPORT We describe the clinical course of a patient managed from the age of six until his death at the age of 33 years. He underwent multiple surgery, including two renal transplants, developed transplant renal artery stenosis that was managed medically, and progressive heart failure at the age of 33 years. His death from a ruptured pseudoaneurysm associated with a restrictive cardiomyopathy is noteworthy. A limited cardiac autopsy revealed the presence of cystine crystals in interstitial cardiac histiocytes and one myocardial cell, along with 1000-fold higher tissue cystine content of the left ventricular myocardium compared to patients without cystinosis, suggesting the possibility of direct cystine mediated metabolic injury.
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Cherqui S, Sevin C, Hamard G, Kalatzis V, Sich M, Pequignot MO, Gogat K, Abitbol M, Broyer M, Gubler MC, Antignac C. Intralysosomal cystine accumulation in mice lacking cystinosin, the protein defective in cystinosis. Mol Cell Biol 2002; 22:7622-32. [PMID: 12370309 PMCID: PMC135682 DOI: 10.1128/mcb.22.21.7622-7632.2002] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cystinosis is an autosomal recessive disorder characterized by an accumulation of intralysosomal cystine. The causative gene, CTNS, encodes cystinosin, a seven-transmembrane-domain protein, which we recently showed to be a lysosomal cystine transporter. The most severe and frequent form of cystinosis, the infantile form, appears around 6 to 12 months, with a proximal tubulopathy (de Toni-Debré-Fanconi syndrome) and ocular damage. End-stage renal failure is reached by 10 years of age. Accumulation of cystine in all tissues eventually leads to multisystemic disease. Treatment with cysteamine, which reduces the concentration of intracellular cystine, delays disease progression but has undesirable side effects. We report the first Ctns knockout mouse model generated using a promoter trap approach. We replaced the last four Ctns exons by an internal ribosome entry site-betagal-neo cassette and showed that the truncated protein was mislocalized and nonfunctional. Ctns(-/-) mice accumulated cystine in all organs tested, and cystine crystals, pathognomonic of cystinosis, were observed. Ctns(-/-) mice developed ocular changes similar to those observed in affected individuals, bone defects and behavioral anomalies. Interestingly, Ctns(-/-) mice did not develop signs of a proximal tubulopathy, or renal failure. A preliminary therapeutic trial using an oral administration of cysteamine was carried out and demonstrated the efficiency of this treatment for cystine clearance in Ctns(-/-) mice. This animal model will prove an invaluable and unique tool for testing emerging therapeutics for cystinosis.
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Kiehntopf M, Schickel J, Gönne BVD, Koch HG, Superti-Furga A, Steinmann B, Deufel T, Harms E. Analysis of the CTNS gene in patients of German and Swiss origin with nephropathic cystinosis. Hum Mutat 2002; 20:237. [PMID: 12204010 DOI: 10.1002/humu.9063] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The autosomal recessive lysosomal storage disorder, nephropathic cystinosis is characterized by impaired transport of free cystine out of lysosomes. The gene responsible for cystinosis, CTNS, consists of 12 exons and encodes a 55 kDa putative lysosomal membrane protein, called cystinosin. Up to now more than 55 different CTNS mutations have been described in cystinosis. We have analyzed the mutation pattern in a population of 40 cystinosis patients from 35 families of German and Swiss origin. CTNS mutations in 68 out of 70 alleles were identified. The common 57-kb deletion accounted for 65% of the alleles. In five patients we found a known GACT deletion at position 18-21. In two patients we identified a nucleotide substitution at codon 339 and one patient showed a CG insertion at position 697-698. In five patients we observed a G insertion at position 926-927. Moreover, five novel mutations including two deletions involving exon 3 (61-61+2delGGT) and exon 6 (280delG), two insertions in exon 6 (292-293insA) and exon 7 (684insCACTT) and one nucleotide substitution in exon 11 (923G>T) have been identified. These data provide a basis for routine molecular diagnosis of cystinosis in the central European population, especially in cystinosis patients of German and Swiss origin.
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Gebrail F, Knapp M, Perotta G, Cualing H. Crystalline histiocytosis in hereditary cysinosis. Arch Pathol Lab Med 2002; 126:1135. [PMID: 12240632 DOI: 10.5858/2002-126-1135-chihc] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Haq MR, Kalatzis V, Gubler MC, Town MM, Antignac C, Van't Hoff WG, Woolf AS. Immunolocalization of cystinosin, the protein defective in cystinosis. J Am Soc Nephrol 2002; 13:2046-51. [PMID: 12138135 DOI: 10.1097/01.asn.0000022012.95680.ba] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Cystinosis is an autosomal recessive disorder associated with excessive lysosomal cystine accumulation secondary to defective lysosomal cystine efflux. CTNS, the gene mutated in cystinosis, codes for the lysosomal membrane protein cystinosin. Antisera were raised in rabbits to a carboxy-terminal oligopeptide sequence from cystinosin. Antisera were screened by Western blotting and immunocytochemical analyses of transfected COS-7 cells expressing either human wild-type cystinosin, a wild-type cystinosin-green fluorescent protein (GFP) fusion protein, or a fusion protein of GFP and mutant human cystinosin with a carboxy-terminal deletion. In Western blots, bands corresponding to cystinosin or cystinosin-GFP were observed in transfected cells but no signal was detected in cells expressing the carboxy-terminal mutant; preimmune sera yielded negative results in all three cases. In transfected cells expressing wild-type cystinosin, immunoreactivity appeared in subcellular vesicles. In cells expressing the wild-type cystinosin-GFP fusion protein, immunoreactivity colocalized with GFP fluorescence. Previous studies demonstrated that GFP fluorescence from this construct colocalized with immunostaining for a known lysosomal membrane protein, i.e., lysosome-associated membrane protein 2. In immunohistochemical analyses, cystinosin localized to tubule epithelia in three normal human kidneys, with a pattern similar to that of lysosome-associated membrane protein 2; cystinosin immunoreactivity was absent in kidneys from patients with a CTNS deletion. For the first time, antisera have been raised that localize cystinosin in cells in vitro and in vivo.
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Helip-Wooley A, Park MA, Lemons RM, Thoene JG. Expression of CTNS alleles: subcellular localization and aminoglycoside correction in vitro. Mol Genet Metab 2002; 75:128-33. [PMID: 11855931 DOI: 10.1006/mgme.2001.3272] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mutations in CTNS result in one of three forms of cystinosis: benign, intermediate, or nephropathic. Homozygosity for a nonsense mutation in CTNS (753G -->A), encoding a premature termination codon (PTC) at amino acid 138 (W138X), results in nephropathic cystinosis. Gentamicin is known to induce PTC readthrough and hence full-length protein production. We demonstrate that addition of gentamicin (300 microg/ml) to cystinotic fibroblasts leads to depletion of intracellular cystine in cell lines with a premature termination codon, but not in those with a large deletion or a deletion leading to a frameshift mutation. Plasmids were constructed with GFP as a C-terminal or N-terminal fusion to CTNS. The normal CTNS protein fused with either N- or C-terminal GFP colocalized with Lysotracker red, a fluorescent stain which selectively accumulates in lysosomes. PTC-GFP, a construct with GFP fused to the C-terminus of CTNS containing a PTC, allowed GFP to serve as a reporter of PTC readthrough. No significant fluorescence was observed in PTC-GFP-transfected cells in the absence of gentamicin but was seen and localized to lysosomes in its presence. A patient with a splice site mutation (IVS11 + 2T -->C) that eliminates the GYDQL lysosomal targeting sequence of cystinosin on one allele, and a PTC mutation (753G -->A) on the other, displays the intermediate phenotype. Transfection of the splice site mutant allele into CTNS null fibroblasts produced cystine depletion. Plasmids with GFP fused to the N-terminus of CTNS containing the splice site mutation (GFP-SS) were constructed. While the normal CTNS-GFP fusion protein was found to colocalize with Lysotracker red almost exclusively, the GFP-SS fusion product was found in the plasma membrane and cytoplasm, as well as lysosomes. A second lysosomal targeting motif in CTNS is present in this sequence, just proximal to the mutation, accounting for the partial lysosomal localization.
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73
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Ponting CP, Mott R, Bork P, Copley RR. Novel protein domains and repeats in Drosophila melanogaster: insights into structure, function, and evolution. Genome Res 2001; 11:1996-2008. [PMID: 11731489 DOI: 10.1101/gr.198701] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Sequence database searching methods such as BLAST, are invaluable for predicting molecular function on the basis of sequence similarities among single regions of proteins. Searches of whole databases however, are not optimized to detect multiple homologous regions within a single polypeptide. Here we have used the prospero algorithm to perform self-comparisons of all predicted Drosophila melanogaster gene products. Predicted repeats, and their homologs from all species, were analyzed further to detect hitherto unappreciated evolutionary relationships. Results included the identification of novel tandem repeats in the human X-linked retinitis pigmentosa type-2 gene product, repeated segments in cystinosin, associated with a defect in cystine transport, and 'nested' homologous domains in dysferlin, whose gene is mutated in limb girdle muscular dystrophy. Novel signaling domain families were found that may regulate the microtubule-based cytoskeleton and ubiquitin-mediated proteolysis, respectively. Two families of glycosyl hydrolases were shown to contain internal repetitions that hint at their evolution via a piecemeal, modular approach. In addition, three examples of fruit fly genes were detected with tandem exons that appear to have arisen via internal duplication. These findings demonstrate how completely sequenced genomes can be exploited to further understand the relationships between molecular structure, function, and evolution.
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MESH Headings
- Amino Acid Sequence/genetics
- Amino Acid Transport Systems, Neutral
- Animals
- Antigens, Differentiation, B-Lymphocyte/chemistry
- Antigens, Differentiation, B-Lymphocyte/genetics
- Antigens, Differentiation, B-Lymphocyte/physiology
- Aspartate-tRNA Ligase/chemistry
- Aspartate-tRNA Ligase/genetics
- Aspartate-tRNA Ligase/physiology
- Cystinosis/genetics
- Drosophila Proteins/chemistry
- Drosophila Proteins/genetics
- Drosophila Proteins/physiology
- Drosophila melanogaster/chemistry
- Drosophila melanogaster/enzymology
- Drosophila melanogaster/genetics
- Evolution, Molecular
- Exons/genetics
- Eye Proteins
- GTP-Binding Proteins
- Gene Duplication
- Glycoproteins
- Glycoside Hydrolases/chemistry
- Glycoside Hydrolases/genetics
- Glycoside Hydrolases/physiology
- Histocompatibility Antigens Class II/chemistry
- Histocompatibility Antigens Class II/genetics
- Histocompatibility Antigens Class II/physiology
- Humans
- Insect Proteins/chemistry
- Insect Proteins/genetics
- Insect Proteins/physiology
- Intracellular Signaling Peptides and Proteins
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/physiology
- Membrane Transport Proteins
- Molecular Sequence Data
- Muscular Dystrophies/genetics
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Proteins/chemistry
- Proteins/genetics
- Proteins/physiology
- Repetitive Sequences, Amino Acid
- Retinitis Pigmentosa/genetics
- Signal Transduction/genetics
- Species Specificity
- Tandem Repeat Sequences
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Kleta R, Anikster Y, Lucero C, Shotelersuk V, Huizing M, Bernardini I, Park M, Thoene J, Schneider J, Gahl WA. CTNS mutations in African American patients with cystinosis. Mol Genet Metab 2001; 74:332-7. [PMID: 11708862 DOI: 10.1006/mgme.2001.3218] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cystinosis, an autosomal recessive lysosomal storage disorder, is rarely diagnosed in African Americans. The disease results from mutations in the gene CTNS; at least 55 such mutations have been reported. By far the most common is a 57,257-bp deletion of Northern European origin encompassing most of the CTNS gene. We performed mutation analysis on DNA from four African American patients with cystinosis. In one individual with classical, nephropathic cystinosis, we identified a new molecular defect, i.e., a homozygous GT-->CC substitution at the +5 position of IVS 5 of CTNS (IVS 5+5 GT-->CC). The out-of-frame splicing of exon 5 creates a null allele consistent with the patient's severe phenotype. Two patients were heterozygous and one homozygous for the common 57-kb deletion allele, reflecting the admixture of African and Northern European gene pools in North America. The two African Americans heterozygous for the 57-kb deletion were also hemizygous for a 928G-->A change, associated with ocular or nonnephropathic cystinosis. These two individuals are the only known African Americans with ocular cystinosis. We conclude that the diagnosis of cystinosis should be entertained in African Americans with symptoms of the disease, and that mutation analysis for the 57-kb deletion should be considered in this group of patients.
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Kalatzis V, Cherqui S, Antignac C, Gasnier B. Cystinosin, the protein defective in cystinosis, is a H(+)-driven lysosomal cystine transporter. EMBO J 2001; 20:5940-9. [PMID: 11689434 PMCID: PMC125690 DOI: 10.1093/emboj/20.21.5940] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cystinosis is an inherited lysosomal storage disease characterized by defective transport of cystine out of lysosomes. However, the causative gene, CTNS, encodes a seven transmembrane domain lysosomal protein, cystinosin, unrelated to known transporters. To investigate the molecular function of cystinosin, the protein was redirected from lysosomes to the plasma membrane by deletion of its C-terminal GYDQL sorting motif (cystinosin-DeltaGYDQL), thereby exposing the intralysosomal side of cystinosin to the extracellular medium. COS cells expressing cystinosin-DeltaGYDQL selectively take up L-cystine from the extracellular medium at acidic pH. Disruption of the transmembrane pH gradient or incubation of the cells at neutral pH strongly inhibits the uptake. Cystinosin-DeltaGYDQL is directly involved in the observed cystine transport, since this activity is highly reduced when the GYDQL motif is restored and is abolished upon introduction of a point mutation inducing early-onset cystinosis. We conclude that cystinosin represents a novel H(+)-driven transporter that is responsible for cystine export from lysosomes, and propose that cystinosin homologues, such as mammalian SL15/Lec35 and Saccharomyces cerevisiae ERS1, may perform similar transport processes at other cellular membranes.
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