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Hebestreit S, Schwahn J, Sandikci V, Maros ME, Valkadinov I, Yilmaz R, Eckrich L, Loghmani SB, Lesch H, Conrad J, Wenz H, Ebert A, Brenner D, Weishaupt JH. PSEN1/SLC20A2 double mutation causes early-onset Alzheimer's disease and primary familial brain calcification co-morbidity. Neurogenetics 2023; 24:209-213. [PMID: 37341843 PMCID: PMC10319679 DOI: 10.1007/s10048-023-00723-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Accepted: 06/07/2023] [Indexed: 06/22/2023]
Abstract
Primary familial brain calcification (PFBC; formerly Fahr's disease) and early-onset Alzheimer's disease (EOAD) may share partially overlapping pathogenic principles. Although the heterozygous loss-of-function mutation c.1523 + 1G > T in the PFBC-linked gene SLC20A2 was detected in a patient with asymmetric tremor, early-onset dementia, and brain calcifications, CSF β-amyloid parameters and FBB-PET suggested cortical β-amyloid pathology. Genetic re-analysis of exome sequences revealed the probably pathogenic missense mutation c.235G > A/p.A79T in PSEN1. The SLC20A2 mutation segregated with mild calcifications in two children younger than 30 years. We thus describe the stochastically extremely unlikely co-morbidity of genetic PFBC and genetic EOAD. The clinical syndromes pointed to additive rather than synergistic effects of the two mutations. MRI data revealed the formation of PFBC calcifications decades before the probable onset of the disease. Our report furthermore exemplifies the value of neuropsychology and amyloid PET for differential diagnosis.
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Affiliation(s)
- Sophie Hebestreit
- Division of Neurodegenerative Disorders, Department of Neurology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany
| | - Janine Schwahn
- Division of Neurodegenerative Disorders, Department of Neurology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany
| | - Vesile Sandikci
- Department of Neurology, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Mate E Maros
- Department of Neuroradiology, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
- Department of Biomedical Informatics, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Ivan Valkadinov
- Division of Neurodegenerative Disorders, Department of Neurology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany
| | - Rüstem Yilmaz
- Division of Neurodegenerative Disorders, Department of Neurology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany
| | - Lukas Eckrich
- Division of Neurodegenerative Disorders, Department of Neurology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany
| | - Seyed Babak Loghmani
- Division of Neurodegenerative Disorders, Department of Neurology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany
| | - Hendrik Lesch
- Department of Neurology, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Julian Conrad
- Division of Neurodegenerative Disorders, Department of Neurology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany
| | - Holger Wenz
- Department of Neuroradiology, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Anne Ebert
- Department of Neurology, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - David Brenner
- Division of Neurodegenerative Disorders, Department of Neurology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany
- Department of Neurology, University of Ulm, Ulm, Germany
| | - Jochen H Weishaupt
- Division of Neurodegenerative Disorders, Department of Neurology, Mannheim Center for Translational Neurosciences, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany.
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Expanding the genetic spectrum of primary familial brain calcification due to SLC2OA2 mutations: a case series. Neurogenetics 2021; 22:65-70. [PMID: 33471268 PMCID: PMC7997821 DOI: 10.1007/s10048-021-00634-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 01/03/2021] [Indexed: 11/08/2022]
Abstract
Primary familial brain calcification (PFBC) is a neurological condition characterized by the presence of intracranial calcifications, mainly involving basal ganglia, thalamus, and dentate nuclei. So far, six genes have been linked to this condition: SLC20A2, PDGFRB, PDGFB, and XPR1 inherited as autosomal-dominant trait, while MYORG and JAM2 present a recessive pattern of inheritance. Patients mainly present with movement disorders, psychiatric disturbances, and cognitive decline or are completely asymptomatic and calcifications may represent an occasional finding. Here we present three variants in SLC20A2, two exonic and one intronic, which we found in patients with PFBC associated to three different clinical phenotypes. One variant is novel and two were already described as variants of uncertain significance. We confirm the pathogenicity of these three variants and suggest a broadening of the phenotypic spectrum associated with mutations in SLC20A2.
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Barker CJ, Tessaro FHG, Ferreira SDS, Simas R, Ayala TS, Köhler M, Rajasekaran SS, Martins JO, Darè E, Berggren PO. XPR1 Mediates the Pancreatic β-Cell Phosphate Flush. Diabetes 2021; 70:111-118. [PMID: 32826297 PMCID: PMC7881847 DOI: 10.2337/db19-0633] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 08/17/2020] [Indexed: 11/13/2022]
Abstract
Glucose-stimulated insulin secretion is the hallmark of the pancreatic β-cell, a critical player in the regulation of blood glucose concentration. In 1974, the remarkable observation was made that an efflux of intracellular inorganic phosphate (Pi) accompanied the events of stimulated insulin secretion. The mechanism behind this "phosphate flush," its association with insulin secretion, and its regulation have since then remained a mystery. We recapitulated the phosphate flush in the MIN6m9 β-cell line and pseudoislets. We demonstrated that knockdown of XPR1, a phosphate transporter present in MIN6m9 cells and pancreatic islets, prevented this flush. Concomitantly, XPR1 silencing led to intracellular Pi accumulation and a potential impact on Ca2+ signaling. XPR1 knockdown slightly blunted first-phase glucose-stimulated insulin secretion in MIN6m9 cells, but had no significant impact on pseudoislet secretion. In keeping with other cell types, basal Pi efflux was stimulated by inositol pyrophosphates, and basal intracellular Pi accumulated following knockdown of inositol hexakisphosphate kinases. However, the glucose-driven phosphate flush occurred despite inositol pyrophosphate depletion. Finally, while it is unlikely that XPR1 directly affects exocytosis, it may protect Ca2+ signaling. Thus, we have revealed XPR1 as the missing mediator of the phosphate flush, shedding light on a 45-year-old mystery.
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Affiliation(s)
- Christopher J Barker
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Fernando Henrique Galvão Tessaro
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
- Laboratory of Immunoendocrinology, Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University São Paulo, São Paulo, Brazil
| | - Sabrina de Souza Ferreira
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
- Laboratory of Immunoendocrinology, Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University São Paulo, São Paulo, Brazil
| | - Rafael Simas
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Thais S Ayala
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
- Laboratory of Immunoendocrinology, Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University São Paulo, São Paulo, Brazil
| | - Martin Köhler
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | | | - Joilson O Martins
- Laboratory of Immunoendocrinology, Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University São Paulo, São Paulo, Brazil
| | - Elisabetta Darè
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Per-Olof Berggren
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
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Abstract
Phosphate is an essential nutrient for life and is a critical component of bone formation, a major signaling molecule, and structural component of cell walls. Phosphate is also a component of high-energy compounds (i.e., AMP, ADP, and ATP) and essential for nucleic acid helical structure (i.e., RNA and DNA). Phosphate plays a central role in the process of mineralization, normal serum levels being associated with appropriate bone mineralization, while high and low serum levels are associated with soft tissue calcification. The serum concentration of phosphate and the total body content of phosphate are highly regulated, a process that is accomplished by the coordinated effort of two families of sodium-dependent transporter proteins. The three isoforms of the SLC34 family (SLC34A1-A3) show very restricted tissue expression and regulate intestinal absorption and renal excretion of phosphate. SLC34A2 also regulates the phosphate concentration in multiple lumen fluids including milk, saliva, pancreatic fluid, and surfactant. Both isoforms of the SLC20 family exhibit ubiquitous expression (with some variation as to which one or both are expressed), are regulated by ambient phosphate, and likely serve the phosphate needs of the individual cell. These proteins exhibit similarities to phosphate transporters in nonmammalian organisms. The proteins are nonredundant as mutations in each yield unique clinical presentations. Further research is essential to understand the function, regulation, and coordination of the various phosphate transporters, both the ones described in this review and the phosphate transporters involved in intracellular transport.
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Affiliation(s)
- Nati Hernando
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Kenneth Gagnon
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Eleanor Lederer
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
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Huang YT, Zhang LH, Li MF, Cheng L, Zou GY, Zhou HH. A splice site mutation causing exon 6 skipping in SLC20A2 gene in a primary familial brain calcification family. Brain Res Bull 2019; 150:261-265. [DOI: 10.1016/j.brainresbull.2019.01.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 12/24/2018] [Accepted: 01/03/2019] [Indexed: 12/17/2022]
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Taglia I, Formichi P, Battisti C, Peppoloni G, Barghigiani M, Tessa A, Federico A. Primary familial brain calcification with a novel SLC20A2 mutation: Analysis of PiT-2 expression and localization. J Cell Physiol 2017; 233:2324-2331. [PMID: 28722801 DOI: 10.1002/jcp.26104] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 07/18/2017] [Indexed: 12/11/2022]
Abstract
Primary familial brain calcification (PFBC) is an autosomal dominant rare disorder characterized by bilateral and symmetric brain calcifications, and neuropsychiatric manifestations. Four genes have been linked to PFBC: SLC20A2, PDGFRB, PDGFB, and XPR1. In this study, we report molecular and clinical data of a PFBC patient carrying a novel SLC20A2 mutation and we investigate the impact of the mutation on PiT-2 expression and function. Sanger sequencing of SLC20A2, PDGFRB, PDGFB, XPR1 led to the identification of a novel duplication of twelve nucleotides (c.1876_1887dup/ p.Trp626_Thr629dup) in SLC20A2 gene. SLC20A2 encodes for a cell membrane transporter (PiT-2) involved in maintenance of inorganic phosphate homeostasis. We performed an analysis of expression and functionality of PiT-2 protein in patient primary cultured fibroblasts. In patient fibroblasts, the mutation does not affect PiT-2 expression but alter sub-cellular localization. The Pi-uptake assay revealed a less Pi depletion in patient than in control fibroblasts, suggesting that SLC20A2 duplication may impair Pi internalization. This is the first study reporting sub-cellular expression analysis of mutant PiT-2 in primary cultured fibroblasts from a PFBC patient, showing that p.Trp626_Thr629dup in SLC20A2 alters PiT-2 sub-cellular localization and reduces Pi-uptake, leading to onset of PFBC in our patient.
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Affiliation(s)
- Ilaria Taglia
- Department of Medicine, Surgery and Neurosciences, University of Siena, Siena, Italy
| | - Patrizia Formichi
- Department of Medicine, Surgery and Neurosciences, University of Siena, Siena, Italy
| | - Carla Battisti
- Department of Medicine, Surgery and Neurosciences, University of Siena, Siena, Italy
| | - Giulia Peppoloni
- Department of Medicine, Surgery and Neurosciences, University of Siena, Siena, Italy
| | | | - Alessandra Tessa
- Molecular Medicine and Neurogenetics, IRCCS Stella Maris, Pisa, Italy
| | - Antonio Federico
- Department of Medicine, Surgery and Neurosciences, University of Siena, Siena, Italy
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