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Novel Compound Heterozygous Variations in MPDZ Gene Caused Isolated Bilateral Macular Coloboma in a Chinese Family. Cells 2022; 11:cells11223602. [PMID: 36429029 PMCID: PMC9688216 DOI: 10.3390/cells11223602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 11/01/2022] [Accepted: 11/07/2022] [Indexed: 11/16/2022] Open
Abstract
Macular coloboma (MC) is a rare congenital retinochoroidal defect characterized by lesions of different sizes in the macular region. The pathological mechanism underlying congenital MC is unknown. Novel compound heterozygous variations, c.4301delA (p.Asp1434fs*3) and c.5255C>G (p.Ser1752Ter), in the multiple PDZ domain (MPDZ) proteins were identified via whole-exome analysis on the proband with isolated bilateral macular coloboma in a Chinese family. Segregation analysis revealed that each of the unaffected parents was heterozygous for one of the two variants. The results of the in silico and bioinformatics analysis were aligned with the experimental data. The knockdown of MPDZ in zebrafish caused a decrease in the ellipsoid zone, a destruction of the outer limiting membrane, and the subsequent RPE degeneration. Overall, the loss of MPDZ in zebrafish contributed to retinal development failure. These results indicate that MPDZ plays an essential role in the occurrence and maintenance of the macula, and the novel compound heterozygous variations were responsible for an autosomal recessive macular deficiency in this Chinese family.
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Vall-Palomar M, Burballa C, Claverie-Martín F, Meseguer A, Ariceta G. Heterogeneity is a common ground in familial hypomagnesemia with hypercalciuria and nephrocalcinosis caused by CLDN19 gene mutations. J Nephrol 2021; 34:2053-2062. [PMID: 33929692 DOI: 10.1007/s40620-021-01054-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 04/19/2021] [Indexed: 11/26/2022]
Abstract
BACKGROUND Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is a rare tubulopathy caused by mutations in the CLDN16 or CLDN19 genes. Patients usually develop hypomagnesemia, hypercalciuria, nephrocalcinosis and renal failure early in life. Patients with CLDN19 mutations may also have ocular abnormalities. Despite clinical variability, factors associated with kidney function impairment, especially in patients with CLDN19 mutations, have not been addressed. METHODS Retrospective multicenter study of 30 genetically confirmed FHHNC Spanish patients. We analyzed kidney function impairment considering as outcomes chronic kidney disease (CKD) stage 3 and annual estimated glomerular filtration rate (eGFR) decline, to identify factors associated with the different phenotypes. RESULTS Of thirty patients, 27 had mutations in the CLDN19 gene (20 homozygous for the p.G20D mutation) and 3 in the CLDN16. Age at diagnosis was 1.71 (0.67-6.04) years and follow-up time was 8.34 ± 4.30 years. No differences in CKD stage 3-free survival based on CLDN19 mutation (p.G20D homozygous vs. other mutations) or gender were found, although females seemed to progress faster than males. Patients with more pronounced eGFR decline had higher PTH levels at diagnosis than those with stable kidney function, despite similar initial eGFR. Approximately 60% of CLDN19 patients presented ocular abnormalities. Furthermore, we confirmed high phenotypic intrafamilial variability. CONCLUSIONS In a contemporary cohort of FHHNC patients with CLDN19 mutations, females seemed to progress to CKD-stage 3 faster than males. Increased PTH levels at baseline may indicate a more severe renal course. There was high phenotype variability among patients with CLDN19 mutations and kidney function impairment differed even between siblings.
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Affiliation(s)
- Mònica Vall-Palomar
- Fisiopatologia Renal, Centre D'Investigacions en Bioquímica I Biologia Molecular (CIBBIM), Institut de Recerca Vall D'Hebron (VHIR), Barcelona, Spain
| | - Carla Burballa
- Fisiopatologia Renal, Centre D'Investigacions en Bioquímica I Biologia Molecular (CIBBIM), Institut de Recerca Vall D'Hebron (VHIR), Barcelona, Spain
| | - Félix Claverie-Martín
- Unidad de Investigación, Hospital Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Anna Meseguer
- Fisiopatologia Renal, Centre D'Investigacions en Bioquímica I Biologia Molecular (CIBBIM), Institut de Recerca Vall D'Hebron (VHIR), Barcelona, Spain
- Departament de Bioquímica I Biologia Molecular. Unitat de Bioquímica de Medicina, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
- Red de Investigación Renal (REDINREN), Instituto Carlos III-FEDER, Madrid, Spain
| | - Gema Ariceta
- Fisiopatologia Renal, Centre D'Investigacions en Bioquímica I Biologia Molecular (CIBBIM), Institut de Recerca Vall D'Hebron (VHIR), Barcelona, Spain.
- Servicio de Nefrología Pediátrica, Hospital Universitari Vall D'Hebron, 08035, Barcelona, Spain.
- Departamento de Pediatría, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.
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Liu F, Xu T, Peng S, Adelman RA, Rizzolo LJ. Claudins regulate gene and protein expression of the retinal pigment epithelium independent of their association with tight junctions. Exp Eye Res 2020; 198:108157. [PMID: 32712183 DOI: 10.1016/j.exer.2020.108157] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/18/2020] [Accepted: 07/20/2020] [Indexed: 01/14/2023]
Abstract
Claudin-19 is the major claudin in the tight junctions of the retinal pigment epithelium (RPE). Claudin-3 is also uniformly expressed albeit in lesser amounts. Besides modulating transepithelial diffusion, claudins modulate gene expression. The absence of claudin-19 and claudin-3 in the RPE cell lines, ARPE-19 and hTERT-RPE-1, provide an opportunity to examine whether exogenous claudins regulate gene expression in the absence of tight junctions. Quantitative RT-PCR was used to compare gene expression in ARPE-19 and hTERT-RPE-1 with that of highly differentiated, human fetal RPE. Claudin-19 and claudin-3 were exogenously expressed using an adenoviral vector. The transepithelial electrical resistance (TER) was measured using Endohm electrodes, and the effects of claudin on the actin cytoskeleton were determined by immunocytochemistry. The effect of claudin on gene expression was examined by quantitative RT-PCR and western blotting. Aside from claudin-19 and claudin-3, ARPE-19 and hTERT-RPE-1 expressed most junction-associated mRNAs in amounts comparable to human fetal RPE, but some RPE signature and maturation genes were under-expressed. Unlike ARPE-19, hTERT-RPE-1 failed to form tight junctions or develop a TER. Claudins exogenously expressed in hTERT-RPE-1 failed to crystalize an apical junctional complex. Actin filaments were not redistributed from stress fibers to cortical bands, and a TER was not established. In hTERT-RPE-1, claudins were found only in internal vesicular-like structures. Nonetheless, claudins increased the expression of the mRNAs for a collection of RPE-enriched proteins. Claudin-19 and claudin-3 had different effects on gene and protein expression indicating activation of overlapping, but distinct, signaling pathways. A major difference was the ability of claudin-19 to affect steady-state levels of ADAM9 and tyrosinase in ARPE-19. In conclusion, claudins can increase the barrier function of a pre-existing apical junctional complex, but on its own it cannot recruit tight junction proteins to form a complex de novo. Many effects of claudin on gene expression did not require an association with the apical junctional complex. Although claudin-19 shared many effects with claudin-3, claudin-19 exerted unique effects on the maturation of RPE.
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Affiliation(s)
- Fanfei Liu
- Aier School of Ophthalmology, Central South University, Changsha, China; Department of Surgery, Yale University, New Haven, USA; Department of Ophthalmology and Visual Science, Yale University, New Haven, USA
| | - Tao Xu
- Aier School of Ophthalmology, Central South University, Changsha, China; Department of Surgery, Yale University, New Haven, USA; Department of Ophthalmology and Visual Science, Yale University, New Haven, USA
| | - Shaomin Peng
- Aier School of Ophthalmology, Central South University, Changsha, China.
| | - Ron A Adelman
- Department of Ophthalmology and Visual Science, Yale University, New Haven, USA
| | - Lawrence J Rizzolo
- Department of Surgery, Yale University, New Haven, USA; Department of Ophthalmology and Visual Science, Yale University, New Haven, USA.
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Prot-Bertoye C, Houillier P. Claudins in Renal Physiology and Pathology. Genes (Basel) 2020; 11:genes11030290. [PMID: 32164158 PMCID: PMC7140793 DOI: 10.3390/genes11030290] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 02/24/2020] [Accepted: 02/24/2020] [Indexed: 12/18/2022] Open
Abstract
Claudins are integral proteins expressed at the tight junctions of epithelial and endothelial cells. In the mammalian kidney, every tubular segment express a specific set of claudins that give to that segment unique properties regarding permeability and selectivity of the paracellular pathway. So far, 3 claudins (10b, 16 and 19) have been causally traced to rare human syndromes: variants of CLDN10b cause HELIX syndrome and variants of CLDN16 or CLDN19 cause familial hypomagnesemia with hypercalciuria and nephrocalcinosis. The review summarizes our current knowledge on the physiology of mammalian tight junctions and paracellular ion transport, as well as on the role of the 3 above-mentioned claudins in health and disease. Claudin 14, although not having been causally linked to any rare renal disease, is also considered, because available evidence suggests that it may interact with claudin 16. Some single-nucleotide polymorphisms of CLDN14 are associated with urinary calcium excretion and/or kidney stones. For each claudin considered, the pattern of expression, the function and the human syndrome caused by pathogenic variants are described.
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Affiliation(s)
- Caroline Prot-Bertoye
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France;
- Service de Physiologie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, F-75015 Paris, France
- Centre de Référence des Maladies Rénales Héréditaires de l’Enfant et de l’Adulte (MARHEA), F-75015 Paris, France
- Centre de Référence des Maladies Rares du Calcium et du Phosphate, F-75015 Paris, France
- CNRS, ERL8228, F-75006 Paris, France
| | - Pascal Houillier
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France;
- Service de Physiologie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, F-75015 Paris, France
- Centre de Référence des Maladies Rénales Héréditaires de l’Enfant et de l’Adulte (MARHEA), F-75015 Paris, France
- Centre de Référence des Maladies Rares du Calcium et du Phosphate, F-75015 Paris, France
- CNRS, ERL8228, F-75006 Paris, France
- Correspondence:
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Fields MA, Del Priore LV, Adelman RA, Rizzolo LJ. Interactions of the choroid, Bruch's membrane, retinal pigment epithelium, and neurosensory retina collaborate to form the outer blood-retinal-barrier. Prog Retin Eye Res 2019; 76:100803. [PMID: 31704339 DOI: 10.1016/j.preteyeres.2019.100803] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 10/26/2019] [Accepted: 10/28/2019] [Indexed: 01/10/2023]
Abstract
The three interacting components of the outer blood-retinal barrier are the retinal pigment epithelium (RPE), choriocapillaris, and Bruch's membrane, the extracellular matrix that lies between them. Although previously reviewed independently, this review integrates these components into a more wholistic view of the barrier and discusses reconstitution models to explore the interactions among them. After updating our understanding of each component's contribution to barrier function, we discuss recent efforts to examine how the components interact. Recent studies demonstrate that claudin-19 regulates multiple aspects of RPE's barrier function and identifies a barrier function whereby mutations of claudin-19 affect retinal development. Co-culture approaches to reconstitute components of the outer blood-retinal barrier are beginning to reveal two-way interactions between the RPE and choriocapillaris. These interactions affect barrier function and the composition of the intervening Bruch's membrane. Normal or disease models of Bruch's membrane, reconstituted with healthy or diseased RPE, demonstrate adverse effects of diseased matrix on RPE metabolism. A stumbling block for reconstitution studies is the substrates typically used to culture cells are inadequate substitutes for Bruch's membrane. Together with human stem cells, the alternative substrates that have been designed offer an opportunity to engineer second-generation culture models of the outer blood-retinal barrier.
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Affiliation(s)
- Mark A Fields
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, PO Box 208061, New Haven, CT, 06520-8061, USA
| | - Lucian V Del Priore
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, PO Box 208061, New Haven, CT, 06520-8061, USA
| | - Ron A Adelman
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, PO Box 208061, New Haven, CT, 06520-8061, USA
| | - Lawrence J Rizzolo
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, PO Box 208061, New Haven, CT, 06520-8061, USA; Department of Surgery, Yale University School of Medicine, PO Box 208062, New Haven, CT, 06520-8062, USA.
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Wang SB, Xu T, Peng S, Singh D, Ghiassi-Nejad M, Adelman RA, Rizzolo LJ. Disease-associated mutations of claudin-19 disrupt retinal neurogenesis and visual function. Commun Biol 2019; 2:113. [PMID: 30937396 PMCID: PMC6433901 DOI: 10.1038/s42003-019-0355-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 02/15/2019] [Indexed: 12/13/2022] Open
Abstract
Mutations of claudin-19 cause Familial Hypomagnesaemia and Hypercalciuria, Nephrocalcinosis with Ocular Involvement. To study the ocular disease without the complications of the kidney disease, naturally occurring point mutations of human CLDN19 were recreated in human induced pluripotent cells or overexpressed in the retinae of newborn mice. In human induced pluripotent cells, we show that the mutation affects retinal neurogenesis and maturation of retinal pigment epithelium (RPE). In mice, the mutations diminish the P1 wave of the electroretinogram, activate apoptosis in the outer nuclear layer, and alter the morphology of bipolar cells. If mice are given 9-cis-retinal to counter the loss of retinal isomerase, the P1 wave is partially restored. The ARPE19 cell line fails to express claudin-19. Exogenous expression of wild type, but not mutant claudin-19, increases the expression of RPE signature genes. Mutated claudin-19 affects multiple stages of RPE and retinal differentiation through its effects on multiple functions of the RPE.
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Affiliation(s)
- Shao-Bin Wang
- Department of Surgery, Yale University, PO Box 208062, New Haven, CT USA
- Department of Ophthalmology, Yale University, 40 Temple Street, New Haven, CT USA
- Present Address: Center for Advanced Vision Science, Department of Ophthalmology, School of Medicine, University of Virginia, Charlottesville, VA 22908 USA
| | - Tao Xu
- Department of Surgery, Yale University, PO Box 208062, New Haven, CT USA
- Department of Ophthalmology, Yale University, 40 Temple Street, New Haven, CT USA
- Aier School of Ophthalmology, Central South University, 198 Furong Middle Ave Section 2, Tianxin District, Changsha, China
| | - Shaomin Peng
- Aier School of Ophthalmology, Central South University, 198 Furong Middle Ave Section 2, Tianxin District, Changsha, China
| | - Deepti Singh
- Department of Surgery, Yale University, PO Box 208062, New Haven, CT USA
- Department of Ophthalmology, Yale University, 40 Temple Street, New Haven, CT USA
- Present Address: Department of Ophthalmology, The Schepens Eye Research Institute, Massachusetts Eye and Ear, Harvard Medical School, 20 Staniford St., Boston, MA 02114 USA
| | - Maryam Ghiassi-Nejad
- Department of Surgery, Yale University, PO Box 208062, New Haven, CT USA
- Department of Ophthalmology, Yale University, 40 Temple Street, New Haven, CT USA
| | - Ron A. Adelman
- Department of Ophthalmology, Yale University, 40 Temple Street, New Haven, CT USA
| | - Lawrence J. Rizzolo
- Department of Surgery, Yale University, PO Box 208062, New Haven, CT USA
- Department of Ophthalmology, Yale University, 40 Temple Street, New Haven, CT USA
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Abstract
Calcium is vital for life, and extracellular calcium concentrations must constantly be maintained within a precise concentration range. Low serum calcium (hypocalcemia) occurs in conjunction with multiple disorders and can be life-threatening if severe. Symptoms of acute hypocalcemia include neuromuscular irritability, tetany, and seizures, which are rapidly resolved with intravenous administration of calcium gluconate. However, disorders that lead to chronic hypocalcemia often have more subtle manifestations. Hypoparathyroidism, characterized by impaired secretion of parathyroid hormone (PTH), a key regulatory hormone for maintaining calcium homeostasis, is a classic cause of chronic hypocalcemia. Disorders that disrupt the metabolism of vitamin D can also lead to chronic hypocalcemia, as vitamin D is responsible for increasing the gut absorption of dietary calcium. Treatment and management options for chronic hypocalcemia vary depending on the underlying disorder. For example, in patients with hypoparathyroidism, calcium and vitamin D supplementation must be carefully titrated to avoid symptoms of hypocalcemia while keeping serum calcium in the low-normal range to minimize hypercalciuria, which can lead to renal dysfunction. Management of chronic hypocalcemia requires knowledge of the factors that influence the complex regulatory axes of calcium homeostasis in a given disorder. This chapter discusses common and rare disorders of hypocalcemia, symptoms and workup, and management options including replacement of PTH in hypoparathyroidism.
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Affiliation(s)
- Erin Bove-Fenderson
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Thier 1101, 50 Blossom St, Boston, MA, 02114, USA
| | - Michael Mannstadt
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Thier 1101, 50 Blossom St, Boston, MA, 02114, USA.
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Lv F, Xu XJ, Wang JY, Liu Y, Jiang Y, Wang O, Xia WB, Xing XP, Li M. A novel mutation in CLDN16 results in rare familial hypomagnesaemia with hypercalciuria and nephrocalcinosis in a Chinese family. Clin Chim Acta 2016; 457:69-74. [PMID: 27067446 DOI: 10.1016/j.cca.2016.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 03/30/2016] [Accepted: 04/06/2016] [Indexed: 02/08/2023]
Abstract
BACKGROUND Familial hypomagnesaemia with hypercalciuria and nephrocalcinosis (FHHNC) is a rare autosomal recessively inherited disease characterized by excessive wasting of renal tubular magnesium and calcium. FHHNC is associated with various mutations in CLDN16 and CLDN19. CASES Two children from a consanguineous family of Chinese Han origin demonstrated manifestations of rickets, polyuria, polydipsia, hematuria and failure to thrive. Hypomagnesaemia (0.49-0.50mmol/L), hypercalciuria or a trend to hypercalciuria (24hour urine calcium: 3.8-5.1mg/kg/day), and secondary hyperparathyroidism (serum PTH level: 94.7-200pg/mL) were revealed upon laboratory examination. Using targeted next-generation sequencing and subsequent confirmation by Sanger sequencing, a novel homozygous mutation was identified in the CLDN16 gene of both FHHNC patients. This specific mutation, a 16bp deletion followed by a 23bp insertion in exon 3, led to the generation of a premature termination codon. The parents and an unaffected sister were all heterozygous carriers of this mutation. CONCLUSIONS We detected a novel mutation in CLDN16 for the first time. The clinical and genetic findings from this study will help to expand the understanding of this rare disease, FHHNC.
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Affiliation(s)
- Fang Lv
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Xiao-Jie Xu
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Jian-Yi Wang
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Yi Liu
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Yan Jiang
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Ou Wang
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Wei-Bo Xia
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Xiao-Ping Xing
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Mei Li
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
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Claverie-Martin F. Familial hypomagnesaemia with hypercalciuria and nephrocalcinosis: clinical and molecular characteristics. Clin Kidney J 2015; 8:656-64. [PMID: 26613020 PMCID: PMC4655790 DOI: 10.1093/ckj/sfv081] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 08/04/2015] [Indexed: 01/19/2023] Open
Abstract
Familial hypomagnesaemia with hypercalciuria and nephrocalcinosis (FHHNC) is an autosomal-recessive renal tubular disorder characterized by excessive urinary losses of magnesium and calcium, bilateral nephrocalcinosis and progressive chronic renal failure. Presentation with FHHNC symptoms generally occurs early in childhood or before adolescence. At present, the only therapeutic option is supportive and consists of oral magnesium supplementation and thiazide diuretics. However, neither treatment seems to have a significant effect on the levels of serum magnesium or urine calcium or on the decline of renal function. In end-stage renal disease patients, renal transplantation is the only effective approach. This rare disease is caused by mutations in the CLDN16 or CLDN19 genes. Patients with mutations in CLDN19 also present severe ocular abnormalities such as myopia, nystagmus and macular colobamata. CLDN16 and CLDN19 encode the tight-junction proteins claudin-16 and claudin-19, respectively, which are expressed in the thick ascending limb of Henle's loop and form an essential complex for the paracellular reabsorption of magnesium and calcium. Claudin-19 is also expressed in retinal epithelium and peripheral neurons. Research studies using mouse and cell models have generated significant advances on the understanding of the pathophysiology of FHHNC. A recent finding has established that another member of the claudin family, claudin-14, plays a key regulatory role in paracellular cation reabsorption by inhibiting the claudin-16-claudin-19 complex. Furthermore, several studies on the molecular and cellular consequences of disease-causing CLDN16 and CLDN19 mutations have provided critical information for the development of potential therapeutic strategies.
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Affiliation(s)
- Felix Claverie-Martin
- Unidad de Investigación, Hospital Nuestra Señora de Candelaria , Santa Cruz de Tenerife , Spain
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