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Zhu Z, Bo-Ran Ho B, Chen A, Amrhein J, Apetrei A, Carpenter TO, Lazaretti-Castro M, Colazo JM, McCrystal Dahir K, Geßner M, Gurevich E, Heier CA, Simmons JH, Hunley TE, Hoppe B, Jacobsen C, Kouri A, Ma N, Majumdar S, Molin A, Nokoff N, Ott SM, Peña HG, Santos F, Tebben P, Topor LS, Deng Y, Bergwitz C. An update on clinical presentation and responses to therapy of patients with hereditary hypophosphatemic rickets with hypercalciuria (HHRH). Kidney Int 2024; 105:1058-1076. [PMID: 38364990 PMCID: PMC11106756 DOI: 10.1016/j.kint.2024.01.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 12/23/2023] [Accepted: 01/08/2024] [Indexed: 02/18/2024]
Abstract
Pathogenic variants in solute carrier family 34, member 3 (SLC34A3), the gene encoding the sodium-dependent phosphate cotransporter 2c (NPT2c), cause hereditary hypophosphatemic rickets with hypercalciuria (HHRH). Here, we report a pooled analysis of clinical and laboratory records of 304 individuals from 145 kindreds, including 20 previously unreported HHRH kindreds, in which two novel SLC34A3 pathogenic variants were identified. Compound heterozygous/homozygous carriers show above 90% penetrance for kidney and bone phenotypes. The biochemical phenotype for heterozygous carriers is intermediate with decreased serum phosphate, tubular reabsorption of phosphate (TRP (%)), fibroblast growth factor 23, and intact parathyroid hormone, but increased serum 1,25-dihydroxy vitamin D, and urine calcium excretion causing idiopathic hypercalciuria in 38%, with bone phenotypes still observed in 23% of patients. Oral phosphate supplementation is the current standard of care, which typically normalizes serum phosphate. However, although in more than half of individuals this therapy achieves correction of hypophosphatemia it fails to resolve the other outcomes. The American College of Medical Genetics and Genomics score correlated with functional analysis of frequent SLC34A3 pathogenic variants in vitro and baseline disease severity. The number of mutant alleles and baseline TRP (%) were identified as predictors for kidney and bone phenotypes, baseline TRP (%) furthermore predicted response to therapy. Certain SLC34A3/NPT2c pathogenic variants can be identified with partial responses to therapy, whereas with some overlap, others present only with kidney phenotypes and a third group present only with bone phenotypes. Thus, our report highlights important novel clinical aspects of HHRH and heterozygous carriers, raises awareness to this rare group of disorders and can be a foundation for future studies urgently needed to guide therapy of HHRH.
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Affiliation(s)
- Zewu Zhu
- Department of Internal Medicine, Section of Endocrinology, Yale University School of Medicine, New Haven, Connecticut, USA; Department of Urology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Bryan Bo-Ran Ho
- Department of Internal Medicine, Section of Endocrinology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Alyssa Chen
- Department of Internal Medicine, Section of Endocrinology, Yale University School of Medicine, New Haven, Connecticut, USA; Department of Otolaryngology, Harvard Medical School, Boston, Massachusetts, USA
| | - James Amrhein
- Pediatric Endocrinology and Diabetes, School of Medicine Greenville Campus, University of South Carolina, Greenville, South Carolina, USA
| | - Andreea Apetrei
- Caen University Hospital, Department of Genetics, UR7450 Biotargen, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, OSCAR Network, Caen, France
| | - Thomas Oliver Carpenter
- Department of Internal Medicine, Section of Endocrinology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Marise Lazaretti-Castro
- Division of Endocrinology, Escola Paulista de Medicina-Universidade Federal de Sao Paulo (EPM-UNIFESP), Sao Paulo, Brazil
| | - Juan Manuel Colazo
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Kathryn McCrystal Dahir
- Division of Endocrinology, Program for Metabolic Bone Disorders, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Michaela Geßner
- Pediatric Nephrology, Children's and Adolescents' Hospital, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Evgenia Gurevich
- Schneider Children's Medical Center of Israel, Pediatric Nephrology Institute, Petach Tikva, Israel; Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva, Israel
| | | | - Jill Hickman Simmons
- Department of Pediatrics, Division of Endocrinology and Diabetes, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, Tennessee, USA
| | - Tracy Earl Hunley
- Division of Pediatric Nephrology, Vanderbilt University Medical Center, Monroe Carell Jr Children's Hospital at Vanderbilt, Nashville, Tennessee, USA
| | - Bernd Hoppe
- Division of Pediatric Nephrology, Department of Pediatrics, University of Bonn, Bonn, Germany
| | - Christina Jacobsen
- Division of Endocrinology, Harvard Medical School, Boston, Massachusetts, USA
| | - Anne Kouri
- Pediatric Nephrology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Nina Ma
- Section of Pediatric Endocrinology, Children's Hospital Colorado, Aurora, Colorado, USA; Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Sachin Majumdar
- Department of Internal Medicine, Section of Endocrinology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Arnaud Molin
- Caen University Hospital, Department of Genetics, UR7450 Biotargen, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, OSCAR Network, Caen, France
| | - Natalie Nokoff
- Department of Pediatrics, Section of Endocrinology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Susan M Ott
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Helena Gil Peña
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), Oviedo, Spain
| | - Fernando Santos
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), Oviedo, Spain
| | - Peter Tebben
- Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic, Rochester, Minnesota, USA; Division of Pediatric Endocrinology, Mayo Clinic, Rochester, Minnesota, USA
| | - Lisa Swartz Topor
- Division of Pediatric Endocrinology, Hasbro Children's Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA
| | - Yanhong Deng
- Yale School of Public Health, New Haven, Connecticut, USA
| | - Clemens Bergwitz
- Department of Internal Medicine, Section of Endocrinology, Yale University School of Medicine, New Haven, Connecticut, USA.
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Wang L, Kulaixi G, Zaiyinati J, Aibai G, Du D, Guo Y. Family analysis and literature study of hereditary hypophosphatemic rickets with hypercalciuria. BMC Pediatr 2024; 24:121. [PMID: 38355430 PMCID: PMC10865686 DOI: 10.1186/s12887-024-04589-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 01/24/2024] [Indexed: 02/16/2024] Open
Abstract
BACKGROUND Hereditary hypophosphatemia rickets with hypercalciuria (HHRH) is a rare autosomal recessive disorder characterised by reduced renal phosphate reabsorption leading to hypophosphataemia, rickets and bone pain. Here, we present a case of HHRH in a Chinese boy. CASE PRESENTATION We report a 11-year-old female proband, who was admitted to our hospital with bilateral genuvarum deformity and short stature. Computed Tomography (CT) showed kidney stones, blood tests showed hypophosphatemia, For a clear diagnosis, we employed high-throughput sequencing technology to screen for variants. Our gene sequencing approach encompassed whole exome sequencing, detection of exon and intron junction regions, and examination of a 20 bp region of adjacent introns. Flanking sequences are defined as ±50 bp upstream and downstream of the 5' and 3' ends of the coding region.The raw sequence data were compared to the known gene sequence data in publicly available sequence data bases using Burrows-Wheeler Aligner software (BWA, 0.7.12-r1039), and the pathogenic variant sites were annotated using Annovar. Subsequently, the suspected pathogenic variants were classified according to ACMG's gene variation classification system. Simultaneously, unreported or clinically ambiguous pathogenic variants were predicted and annotated based on population databases. Any suspected pathogenic variants identified through this analysis were then validated using Sanger sequencing technology. At last, the proband and her affected sister carried pathogenic homozygous variant in the geneSLC34A3(exon 13, c.1402C > T; p.R468W). Their parents were both heterozygous carriers of the variant. Genetic testing revealed that the patient has anLRP5(exon 18, c.3917C > T; p.A1306V) variant of Uncertain significance, which is a rare homozygous variant. CONCLUSION This case report aims to raise awareness of the presenting characteristics of HHRH. The paper describes a unique case involving variants in both theSLC34A3andLRP5genes, which are inherited in an autosomal recessive manner. This combination of gene variants has not been previously reported in the literature. It is uncertain whether the presence of these two mutated genes in the same individual will result in more severe clinical symptoms. This report shows that an accurate diagnosis is critical, and with early diagnosis and correct treatment, patients will have a better prognosis.
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Affiliation(s)
- Lufeng Wang
- Department of Endocrinology, People's Hospital of Xinjiang Uygur Autonomous Region, Xinjiang Clinical Research Center for Diabetes, Urumqi, 830000, China
| | - Gulimire Kulaixi
- Department of Endocrinology, Yecheng County, Kashi City of Xinjiang Uygur Autonomous Region, Kashi City, 832000, China
| | - Jiazireya Zaiyinati
- Department of Endocrinology, People's Hospital of Xinjiang Uygur Autonomous Region, Xinjiang Clinical Research Center for Diabetes, Urumqi, 830000, China
| | - Guzhalikezi Aibai
- Department of Endocrinology, Yecheng County, Kashi City of Xinjiang Uygur Autonomous Region, Kashi City, 832000, China
| | - Danyang Du
- Department of Endocrinology, People's Hospital of Xinjiang Uygur Autonomous Region, Xinjiang Clinical Research Center for Diabetes, Urumqi, 830000, China
| | - Yanying Guo
- Department of Endocrinology, People's Hospital of Xinjiang Uygur Autonomous Region, Xinjiang Clinical Research Center for Diabetes, Urumqi, 830000, China.
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Collins MT, Marcucci G, Anders HJ, Beltrami G, Cauley JA, Ebeling PR, Kumar R, Linglart A, Sangiorgi L, Towler DA, Weston R, Whyte MP, Brandi ML, Clarke B, Thakker RV. Skeletal and extraskeletal disorders of biomineralization. Nat Rev Endocrinol 2022; 18:473-489. [PMID: 35578027 DOI: 10.1038/s41574-022-00682-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/13/2022] [Indexed: 12/15/2022]
Abstract
The physiological process of biomineralization is complex and deviation from it leads to a variety of diseases. Progress in the past 10 years has enhanced understanding of the genetic, molecular and cellular pathophysiology underlying these disorders; sometimes, this knowledge has both facilitated restoration of health and clarified the very nature of biomineralization as it occurs in humans. In this Review, we consider the principal regulators of mineralization and crystallization, and how dysregulation of these processes can lead to human disease. The knowledge acquired to date and gaps still to be filled are highlighted. The disorders of mineralization discussed comprise a broad spectrum of conditions that encompass bone disorders associated with alterations of mineral quantity and quality, as well as disorders of extraskeletal mineralization (hyperphosphataemic familial tumoural calcinosis). Included are disorders of alkaline phosphatase (hypophosphatasia) and phosphate homeostasis (X-linked hypophosphataemic rickets, fluorosis, rickets and osteomalacia). Furthermore, crystallopathies are covered as well as arterial and renal calcification. This Review discusses the current knowledge of biomineralization derived from basic and clinical research and points to future studies that will lead to new therapeutic approaches for biomineralization disorders.
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Affiliation(s)
- Michael T Collins
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, NIH, Bethesda, MD, USA.
| | - Gemma Marcucci
- Bone Metabolic Diseases Unit, Department of Biomedical, Experimental and Clinical Sciences, University of Florence, Florence, Italy
| | - Hans-Joachim Anders
- Department of Medicine IV, Hospital of the University of Munich, Ludwig-Maximilians University, Munich, Germany
| | - Giovanni Beltrami
- Department Paediatric Orthopedic Oncology, Careggi and Meyer Children Hospital, Florence, Italy
| | - Jane A Cauley
- Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
| | - Peter R Ebeling
- Department of Medicine, School of Clinical Sciences, Monash University, Melbourne, Australia
| | - Rajiv Kumar
- Departments of Medicine, Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Agnès Linglart
- APHP, Endocrinologie et diabète de l'enfant, Paris, France
| | - Luca Sangiorgi
- Medical Genetics and Skeletal Rare Diseases, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Dwight A Towler
- University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ria Weston
- Cardiovascular Research Group, Manchester Metropolitan University, Manchester, UK
| | - Michael P Whyte
- Center for Metabolic Bone Disease and Molecular Research, Shriners Hospitals for Children-St Louis, St Louis, MO, USA
- Division of Bone and Mineral Diseases, Department of Internal Medicine, Washington University School of Medicine, St Louis, MO, USA
| | | | - Bart Clarke
- Mayo Clinic Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Rochester, MN, USA
| | - Rajesh V Thakker
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
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Stürznickel J, Heider F, Delsmann A, Gödel M, Grünhagen J, Huber TB, Kornak U, Amling M, Oheim R. Clinical Spectrum of Hereditary Hypophosphatemic Rickets With Hypercalciuria (HHRH). J Bone Miner Res 2022; 37:1580-1591. [PMID: 35689455 DOI: 10.1002/jbmr.4630] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 05/19/2022] [Accepted: 06/04/2022] [Indexed: 11/11/2022]
Abstract
Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) represents an FGF23-independent disease caused by biallelic variants in the solute carrier family 34-member 3 (SLC34A3) gene. HHRH is characterized by chronic hypophosphatemia and an increased risk for nephrocalcinosis and rickets/osteomalacia, muscular weakness, and secondary limb deformity. Biochemical changes, but no relevant skeletal changes, have been reported for heterozygous SLC34A3 carriers. Therefore, we assessed the characteristics of individuals with biallelic and monoallelic SLC34A3 variants. In 8 index patients and 5 family members, genetic analysis was performed using a custom gene panel. The skeletal assessment comprised biochemical parameters, areal bone mineral density (aBMD), and bone microarchitecture. Pathogenic SLC34A3 variants were revealed in 7 of 13 individuals (2 homozygous, 5 heterozygous), whereas 3 of 13 carried monoallelic variants of unknown significance. Whereas both homozygous individuals had nephrocalcinosis, only one displayed a skeletal phenotype consistent with HHRH. Reduced to low-normal phosphate levels, decreased tubular reabsorption of phosphate (TRP), and high-normal to elevated values of 1,25-OH2 -D3 accompanied by normal cFGF23 levels were revealed independently of mutational status. Interestingly, individuals with nephrocalcinosis showed significantly increased calcium excretion and 1,25-OH2 -D3 levels but normal phosphate reabsorption. Furthermore, aBMD Z-score <-2.0 was revealed in 4 of 8 heterozygous carriers, and HR-pQCT analysis showed a moderate decrease in structural parameters. Our findings highlight the clinical relevance also of monoallelic SLC34A3 variants, including their potential skeletal impairment. Calcium excretion and 1,25-OH2 -D3 levels, but not TRP, were associated with nephrocalcinosis. Future studies should investigate the effects of distinct SLC34A3 variants and optimize treatment and monitoring regimens to prevent nephrocalcinosis and skeletal deterioration. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Julian Stürznickel
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,Department of Trauma and Orthopaedic Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Fiona Heider
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Alena Delsmann
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Markus Gödel
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Johannes Grünhagen
- Labor Berlin Charité Vivantes GmbH-corporate member of Institute for Medical Genetics and Human Genetics, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Tobias B Huber
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Uwe Kornak
- Institute for Medical Genetics and Human Genetics, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin, Germany.,BIH Center for Regenerative Therapies (BCRT), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin, Germany.,Institute of Human Genetics, University Medical Center Göttingen, Göttingen, Germany
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Ralf Oheim
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,Martin Zeitz Center for Rare Diseases, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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5
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Rush ET, Johnson B, Aradhya S, Beltran D, Bristow SL, Eisenbeis S, Guerra NE, Krolczyk S, Miller N, Morales A, Ramesan P, Sarafrazi S, Truty R, Dahir K. Molecular Diagnoses of X-Linked and Other Genetic Hypophosphatemias: Results From a Sponsored Genetic Testing Program. J Bone Miner Res 2022; 37:202-214. [PMID: 34633109 PMCID: PMC9298723 DOI: 10.1002/jbmr.4454] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 09/27/2021] [Accepted: 10/02/2021] [Indexed: 12/20/2022]
Abstract
X-linked hypophosphatemia (XLH), a dominant disorder caused by pathogenic variants in the PHEX gene, affects both sexes of all ages and results in elevated serum fibroblast growth factor 23 (FGF23) and below-normal serum phosphate. In XLH, rickets, osteomalacia, short stature, and lower limb deformity may be present with muscle pain and/or weakness/fatigue, bone pain, joint pain/stiffness, hearing difficulty, enthesopathy, osteoarthritis, and dental abscesses. Invitae and Ultragenyx collaborated to provide a no-charge sponsored testing program using a 13-gene next-generation sequencing panel to confirm clinical XLH or aid diagnosis of suspected XLH/other genetic hypophosphatemia. Individuals aged ≥6 months with clinical XLH or suspected genetic hypophosphatemia were eligible. Of 831 unrelated individuals tested between February 2019 and June 2020 in this cross-sectional study, 519 (62.5%) individuals had a pathogenic or likely pathogenic variant in PHEX (PHEX-positive). Among the 312 PHEX-negative individuals, 38 received molecular diagnoses in other genes, including ALPL, CYP27B1, ENPP1, and FGF23; the remaining 274 did not have a molecular diagnosis. Among 319 patients with a provider-reported clinical diagnosis of XLH, 88.7% (n = 283) had a reportable PHEX variant; 81.5% (n = 260) were PHEX-positive. The most common variant among PHEX-positive individuals was an allele with both the gain of exons 13-15 and c.*231A>G (3'UTR variant) (n = 66/519). Importantly, over 80% of copy number variants would have been missed by traditional microarray analysis. A positive molecular diagnosis in 41 probands (4.9%; 29 PHEX positive, 12 non-PHEX positive) resulted in at least one family member receiving family testing. Additional clinical or family member information resulted in variant(s) of uncertain significance (VUS) reclassification to pathogenic/likely pathogenic (P/LP) in 48 individuals, highlighting the importance of segregation and clinical data. In one of the largest XLH genetic studies to date, 65 novel PHEX variants were identified and a high XLH diagnostic yield demonstrated broad insight into the genetic basis of XLH. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Eric T Rush
- Children's Mercy Kansas City, Kansas City, MO, USA.,Department of Pediatrics, University of Missouri - Kansas City School of Medicine, Kansas City, MO, USA.,Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS, USA
| | | | | | | | | | | | - Norma E Guerra
- Department of Pediatric Nephrology, Hospital General del Centro Médico Nacional «La Raza», Instituto Mexicano del Seguro Social (IMSS), Ciudad de México, Mexico
| | | | | | | | | | | | | | - Kathryn Dahir
- Program for Metabolic Bone Disorders, Vanderbilt University Medical Center (VUMC), Nashville, TN, USA
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Pinto E Vairo F, Prochnow C, Kemppainen JL, Lisi EC, Steyermark JM, Kruisselbrink TM, Pichurin PN, Dhamija R, Hager MM, Albadri S, Cornell LD, Lazaridis KN, Klee EW, Senum SR, El Ters M, Amer H, Baudhuin LM, Moyer AM, Keddis MT, Zand L, Sas DJ, Erickson SB, Fervenza FC, Lieske JC, Harris PC, Hogan MC. Genomics Integration Into Nephrology Practice. Kidney Med 2021; 3:785-798. [PMID: 34746741 PMCID: PMC8551494 DOI: 10.1016/j.xkme.2021.04.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
RATIONALE & OBJECTIVE The etiology of kidney disease remains unknown in many individuals with chronic kidney disease (CKD). We created the Mayo Clinic Nephrology Genomics Clinic to improve our ability to integrate genomic and clinical data to identify the etiology of unexplained CKD. STUDY DESIGN Retrospective study. SETTING & PARTICIPANTS An essential component of our program is the Nephrology Genomics Board which consists of nephrologists, geneticists, pathologists, translational omics scientists, and trainees who interpret the patient's clinical and genetic data. Since September 2016, the Board has reviewed 163 cases (15 cystic, 100 glomerular, 6 congenital anomalies of kidney and urinary tract (CAKUT), 20 stones, 15 tubulointerstitial, and 13 other). ANALYTICAL APPROACH Testing was performed with targeted panels, single gene analysis, or analysis of kidney-related genes from exome sequencing. Variant classification was obtained based on the 2015 American College of Medical Genetics and Genomics and the Association for Molecular Pathology guidelines. RESULTS A definitive genetic diagnosis was achieved for 50 families (30.7%). The highest diagnostic yield was obtained in individuals with tubulointerstitial diseases (53.3%), followed by congenital anomalies of the kidney and urological tract (33.3%), glomerular (31%), cysts (26.7%), stones (25%), and others (15.4%). A further 20 (12.3%) patients had variants of interest, and variant segregation, and research activities (exome, genome, or transcriptome sequencing) are ongoing for 44 (40%) unresolved families. LIMITATIONS Possible overestimation of diagnostic rate due to inclusion of individuals with variants with evidence of pathogenicity but classified as of uncertain significance by the clinical laboratory. CONCLUSIONS Integration of genomic and research testing and multidisciplinary evaluation in a nephrology cohort with CKD of unknown etiology or suspected monogenic disease provided a diagnosis in a third of families. These diagnoses had prognostic implications, and often changes in management were implemented.
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Affiliation(s)
- Filippo Pinto E Vairo
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota
- Department of Clinical Genomics, Mayo Clinic, Rochester, Minnesota
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Carri Prochnow
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota
- Department of Clinical Genomics, Mayo Clinic, Rochester, Minnesota
| | | | - Emily C Lisi
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota
| | - Joan M Steyermark
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota
| | | | - Pavel N Pichurin
- Department of Clinical Genomics, Mayo Clinic, Rochester, Minnesota
| | - Rhadika Dhamija
- Department of Clinical Genomics, Mayo Clinic, Scottsdale, Arizona
| | - Megan M Hager
- Department of Clinical Genomics, Mayo Clinic, Scottsdale, Arizona
| | - Sam Albadri
- Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, Minnesota
| | - Lynn D Cornell
- Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, Minnesota
| | - Konstantinos N Lazaridis
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota
- Division of Gastroenterology & Hepatology, Mayo Clinic, Rochester, Minnesota
| | - Eric W Klee
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota
- Department of Clinical Genomics, Mayo Clinic, Rochester, Minnesota
- Department of Quantitative Health Sciences, Mayo Clinic, Rochester, Minnesota
| | - Sarah R Senum
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Mireille El Ters
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Hatem Amer
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Linnea M Baudhuin
- Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, Minnesota
| | - Ann M Moyer
- Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, Minnesota
| | - Mira T Keddis
- Division of Nephrology, Mayo Clinic, Scottsdale, Arizona
| | - Ladan Zand
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
| | - David J Sas
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Stephen B Erickson
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
| | | | - John C Lieske
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
- Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, Minnesota
| | - Peter C Harris
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Marie C Hogan
- Department of Clinical Genomics, Mayo Clinic, Rochester, Minnesota
- Division of Nephrology & Hypertension, Mayo Clinic, Rochester, Minnesota
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7
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Marcucci G, Brandi ML. Congenital Conditions of Hypophosphatemia Expressed in Adults. Calcif Tissue Int 2021; 108:91-103. [PMID: 32409880 DOI: 10.1007/s00223-020-00695-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 04/15/2020] [Indexed: 01/05/2023]
Abstract
The main congenital conditions of hypophosphatemia expressed in adulthood include several forms of hereditary hypophosphatemic rickets and a congenital disorder of vitamin D metabolism characterized by osteomalacia and hypophosphatemia in adult patients. Hypophosphatemia in adults is defined as serum phosphate concentration < 0.80 mmol/L. The principal regulators of phosphate homeostasis, as is well known, are parathyroid hormone (PTH), activated vitamin D, and Fibroblast Growth Factor 23 (FGF23). Differential diagnosis of hypophosphatemia is based on the evaluation of mechanisms leading to this alteration, such as high PTH activity, inadequate phosphate absorption from the gut, or renal phosphate wasting, either due to primary tubular defects or high FGF23 levels. The most common inherited form associated to hypophosphatemia is X-linked hypophosphatemic rickets (XLH), caused by PHEX gene mutations with enhanced secretion of the FGF23. Until now, the management of hypophosphatemia in adulthood has been poorly investigated. It is widely debated whether adult patients benefit from the conventional treatments normally used for pediatric patients. The new treatment for XLH with burosumab, a recombinant human IgG1 monoclonal antibody that binds to FGF23, blocking its activity, may change the pharmacological management of adult subjects with hypophosphatemia associated to FGF23-dependent mechanisms.
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Affiliation(s)
- Gemma Marcucci
- Bone Metabolic Diseases Unit, Department of Biomedical, Experimental and Clinical Sciences, University of Florence, AOU Careggi, Florence, Italy
| | - Maria Luisa Brandi
- Bone Metabolic Diseases Unit, Department of Biomedical, Experimental and Clinical Sciences, University of Florence, AOU Careggi, Florence, Italy.
- Head Bone Metabolic Diseases Unit, Department of Biomedical, Experimental and Clinical Sciences, University of Florence, Largo Palagi 1, 50139, Florence, Italy.
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8
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Hereditary Hypophosphatemic Rickets with Hypercalciuria (HHRH) Presenting with Genu Valgum Deformity: Treatment with Phosphate Supplementation and Surgical Correction. Case Rep Endocrinol 2020; 2020:1047327. [PMID: 32695531 PMCID: PMC7368196 DOI: 10.1155/2020/1047327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/18/2020] [Indexed: 11/17/2022] Open
Abstract
We describe a case of hereditary hypophosphatemic rickets with hypercalciuria (HHRH) in a 32-year-old female with short stature, chronic pathologic genu valgum deformity, and knee pain who was referred to endocrinology clinic after previous inconclusive workups. We present imaging spanning 10 years of untreated disease. Biochemical studies showed hypophosphatemia with undetectable fibroblast growth factor 23 (FGF23.) Renal ultrasound revealed bilateral medullary nephrocalcinosis despite no apparent hypercalciuria. Due to concern for HHRH, genetic testing was performed that determined this patient to be homozygous in the SLC34A3 gene for a previously described missense variant (c.1402C > T, p.Arg468Trp). There was no known family history of rickets. A bone biopsy with metabolic studies was performed for diagnostic and prognostic reasons. The histopathological findings along with tetracycline uptake studies were consistent with a diagnosis of HHRH. Treatment with phosphorous supplementation and surgical correction of her valgum deformity resulted in resolution of pain, but no change in bone histomorphometry.
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9
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Tsuboi Y, Ohtomo S, Ichida Y, Hagita H, Ozawa K, Iida M, Nagao S, Ikegami H, Takahashi T, Horiba N. EOS789, a novel pan-phosphate transporter inhibitor, is effective for the treatment of chronic kidney disease-mineral bone disorder. Kidney Int 2020; 98:343-354. [PMID: 32624180 DOI: 10.1016/j.kint.2020.02.040] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 02/18/2020] [Accepted: 02/28/2020] [Indexed: 12/13/2022]
Abstract
Chronic kidney disease is characterized as impaired renal function along with the imbalance and dysregulation of mineral metabolism; recognized as chronic kidney disease-mineral and bone disorder. Hyperphosphatemia, characterized by altered phosphate homeostasis along with elevated fibroblast growth factor-23 and intact parathyroid hormone, is such an alteration of mineral metabolism. We discovered a novel inhibitor, EOS789, that interacts with several sodium-dependent phosphate transporters (NaPi-IIb, PiT-1, and PiT-2) known to contribute to intestinal phosphate absorption. This inhibitor dose-dependently increased the fecal phosphorus excretion rate and inversely decreased the urinary phosphorus excretion rate in normal rats, suggesting inhibition of intestinal phosphorus absorption. In rats with adenine-induced hyperphosphatemia, EOS789 markedly decreased the serum phosphate, fibroblast growth factor-23, and intact parathyroid hormone below values found in normal control rats. Notably, this pan-phosphate transporter inhibitor exhibited a more potent effect on serum phosphate than a NaPi-IIb-selective inhibitor in rats with hyperphosphatemia indicating that PiT-1 and PiT-2 play important roles in intestinal phosphate absorption. Moreover, in a long-term study, EOS789 sustained the suppression of serum phosphorus in parallel with fibroblast growth factor-23 and intact parathyroid hormone and ameliorated ectopic calcification of the thoracic aorta. Additionally, EOS789 treatment also ameliorated kidney deterioration in rats with progressive kidney injury, probably due to the strict phosphate control. Thus, EOS789 has potent efficacy against hyperphosphatemia and its complications and could provide a significant benefit to patients who are ineffectively treated with phosphate binders.
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Affiliation(s)
- Yoshinori Tsuboi
- Research Division, Chugai Pharmaceutical Co., Ltd., Gotemba, Shizuoka, Japan
| | - Shuichi Ohtomo
- Research Division, Chugai Pharmaceutical Co., Ltd., Gotemba, Shizuoka, Japan.
| | - Yasuhiro Ichida
- Research Division, Chugai Pharmaceutical Co., Ltd., Gotemba, Shizuoka, Japan
| | - Hitoshi Hagita
- Chugai Research Institute for Medical Science, Inc., Gotemba, Shizuoka, Japan
| | - Kazuharu Ozawa
- Research Division, Chugai Pharmaceutical Co., Ltd., Gotemba, Shizuoka, Japan
| | - Manami Iida
- Research Division, Chugai Pharmaceutical Co., Ltd., Gotemba, Shizuoka, Japan
| | - Shunsuke Nagao
- Translational Research Division, Chugai Pharmaceutical Co., Ltd., Kamakura, Kanagawa, Japan
| | - Hisashi Ikegami
- Translational Research Division, Chugai Pharmaceutical Co., Ltd., Kamakura, Kanagawa, Japan
| | - Tadakatsu Takahashi
- Research Division, Chugai Pharmaceutical Co., Ltd., Gotemba, Shizuoka, Japan
| | - Naoshi Horiba
- Research Division, Chugai Pharmaceutical Co., Ltd., Gotemba, Shizuoka, Japan
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10
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Tang A, Hinz L, Khan A, Kline G. Phosphate matters when investigating hypercalcemia: a mutation in SLC34A3 causing HHRH. Endocrinol Diabetes Metab Case Rep 2019; 2019:1-6. [PMID: 31352694 PMCID: PMC6685096 DOI: 10.1530/edm-19-0058] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is a rare, autosomal recessive disorder caused by mutations in the SLC34A3 gene that encodes the renal sodium-dependent phosphate cotransporter 2c (NaPi-IIc). It may present as intermittent mild hypercalcemia which may attract initial diagnostic attention but appreciation of concomitant hypophosphatemia is critical for consideration of the necessary diagnostic approach. A 21-year-old woman was assessed by adult endocrinology for low bone mass. She initially presented age two with short stature, nephrocalcinosis and mild intermittent hypercalcemia with hypercalciuria. She had no evidence of medullary sponge kidney or Fanconi syndrome and no bone deformities, pain or fractures. She had recurrent episodes of nephrolithiasis. In childhood, she was treated with hydrochlorothiazide to reduce urinary calcium. Upon review of prior investigations, she had persistent hypophosphatemia with phosphaturia, low PTH and a high-normal calcitriol. A diagnosis of HHRH was suspected and genetic testing confirmed a homozygous c.1483G>A (p.G495R) missense mutation of the SLC34A3 gene. She was started on oral phosphate replacement which normalized her serum phosphate, serum calcium and urine calcium levels over the subsequent 5 years. HHRH is an autosomal recessive condition that causes decreased renal reabsorption of phosphate, leading to hyperphosphaturia, hypophosphatemia and PTH-independent hypercalcemia due to the physiologic increase in calcitriol which also promotes hypercalciuria. Classically, patients present in childhood with bone pain, vitamin D-independent rickets and growth delay. This case of a SLC34A3 mutation illustrates the importance of investigating chronic hypophosphatemia even in the presence of other more common electrolyte abnormalities.
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Affiliation(s)
- Andrew Tang
- Division of Endocrinology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Laura Hinz
- Division of Endocrinology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Aneal Khan
- Department of Medical Genetics and Pediatrics, University of Calgary, Alberta Children’s Hospital Research Institute, Calgary, Alberta, Canada
| | - Gregroy Kline
- Division of Endocrinology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada
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11
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Wagner CA, Rubio-Aliaga I, Hernando N. Renal phosphate handling and inherited disorders of phosphate reabsorption: an update. Pediatr Nephrol 2019; 34:549-559. [PMID: 29275531 DOI: 10.1007/s00467-017-3873-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 12/08/2017] [Accepted: 12/12/2017] [Indexed: 01/12/2023]
Abstract
Renal phosphate handling critically determines plasma phosphate and whole body phosphate levels. Filtered phosphate is mostly reabsorbed by Na+-dependent phosphate transporters located in the brush border membrane of the proximal tubule: NaPi-IIa (SLC34A1), NaPi-IIc (SLC34A3), and Pit-2 (SLC20A2). Here we review new evidence for the role and relevance of these transporters in inherited disorders of renal phosphate handling. The importance of NaPi-IIa and NaPi-IIc for renal phosphate reabsorption and mineral homeostasis has been highlighted by the identification of mutations in these transporters in a subset of patients with infantile idiopathic hypercalcemia and patients with hereditary hypophosphatemic rickets with hypercalciuria. Both diseases are characterized by disturbed calcium homeostasis secondary to elevated 1,25-(OH)2 vitamin D3 as a consequence of hypophosphatemia. In vitro analysis of mutated NaPi-IIa or NaPi-IIc transporters suggests defective trafficking underlying disease in most cases. Monoallelic pathogenic mutations in both SLC34A1 and SLC34A3 appear to be very frequent in the general population and have been associated with kidney stones. Consistent with these findings, results from genome-wide association studies indicate that variants in SLC34A1 are associated with a higher risk to develop kidney stones and chronic kidney disease, but underlying mechanisms have not been addressed to date.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland. .,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland.
| | - Isabel Rubio-Aliaga
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland
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12
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Role of the putative PKC phosphorylation sites of the type IIc sodium-dependent phosphate transporter in parathyroid hormone regulation. Clin Exp Nephrol 2019; 23:898-907. [DOI: 10.1007/s10157-019-01725-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 03/01/2019] [Indexed: 11/26/2022]
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13
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Evaluating pathogenicity of SLC34A3-Ser192Leu, a frequent European missense variant in disorders of renal phosphate wasting. Urolithiasis 2019; 47:511-519. [PMID: 30798342 PMCID: PMC6825645 DOI: 10.1007/s00240-019-01116-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 02/07/2019] [Indexed: 11/26/2022]
Abstract
Loss-of-function mutations of SLC34A3 represent an established cause of a distinct renal phosphate wasting disorder termed hereditary hypophosphatemic rickets with hypercalciuria (HHRH). SLC34A3 encodes the renal phosphate transporter NaPi2c expressed at the apical brush border of proximal renal tubules. Substitution of p.Ser192Leu is one of the most frequent genetic changes among HHRH patients in Europe, but has never been systematically evaluated, clinically or on a cellular level. Identification of a 32-year-old female with a homozgyous c.575C>T, p.Ser192Leu substitution enabled a more comprehensive assessment of the impact of this missense variant. Clinically, the patient showed renal phosphate wasting and nephrocalcinosis without any bone abnormalities. Heterozygous carriers of deleterious SLC34A3 variants were previously described to harbor an increased risk of kidney stone formation and renal calcification. We hence examined the frequency of p.Ser192Leu variants in our adult kidney stone cohort and compared the results to clinical findings of previously published cases of both mono- and biallelic p.Ser192Leu changes. On a cellular level, p.Ser192Leu-mutated transporters localize to the plasma membrane in different cellular systems, but lead to significantly reduced transport activity of inorganic phosphate upon overexpression in Xenopus oocytes. Despite the reduced function in ectopic cellular systems, the clinical consequences of p.Ser192Leu may appear relatively mild, at least in our index patient, and can potentially be missed in clinical practice.
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14
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Marcucci G, Masi L, Ferrarì S, Haffner D, Javaid MK, Kamenický P, Reginster JY, Rizzoli R, Brandi ML. Phosphate wasting disorders in adults. Osteoporos Int 2018; 29:2369-2387. [PMID: 30014155 DOI: 10.1007/s00198-018-4618-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 06/19/2018] [Indexed: 12/14/2022]
Abstract
A cause of hypophosphatemia is phosphate wasting disorders. Knowledge concerning mechanisms involved in phosphate wasting disorders has greatly increased in the last decade by the identification of phosphatonins, among them FGF-23. FGF-23 is a primarily bone derived factor decreasing renal tubular reabsorption of phosphate and the synthesis of calcitriol. Currently, pharmacological treatment of these disorders offers limited efficacy and is potentially associated to gastrointestinal, renal, and parathyroid complications; therefore, efforts have been directed toward newer pharmacological strategies that target the FGF-23 pathway. This review focuses on phosphate metabolism, its main regulators, and phosphate wasting disorders in adults, highlighting the main issues related to diagnosis and current and new potential treatments.
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Affiliation(s)
- G Marcucci
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy
| | - L Masi
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy
| | - S Ferrarì
- Division of Bone Diseases, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland
| | - D Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - M K Javaid
- Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
| | - P Kamenický
- Service d'Endocrinologie et des Maladies de la Reproduction, Centre de référence des Maladies Rares du métabolisme du calcium et du phosphore, Hopital de Bicêtre - AP-HP, 94275, Le Kremlin-Bicêtre, France
| | - J-Y Reginster
- Department of Public Health, Epidemiology and Health Economics, University of Liège, Liège, Belgium
| | - R Rizzoli
- Division of Bone Diseases, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland
| | - M L Brandi
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy.
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15
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Fujii T, Shiozaki Y, Segawa H, Nishiguchi S, Hanazaki A, Noguchi M, Kirino R, Sasaki S, Tanifuji K, Koike M, Yokoyama M, Arima Y, Kaneko I, Tatsumi S, Ito M, Miyamoto KI. Analysis of opossum kidney NaPi-IIc sodium-dependent phosphate transporter to understand Pi handling in human kidney. Clin Exp Nephrol 2018; 23:313-324. [PMID: 30317447 DOI: 10.1007/s10157-018-1653-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 09/24/2018] [Indexed: 01/17/2023]
Abstract
BACKGROUND The role of Na+-dependent inorganic phosphate (Pi) transporters in the human kidney is not fully clarified. Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is caused by loss-of-function mutations in the IIc Na+-dependent Pi transporter (NPT2c/Npt2c/NaPi-IIc) gene. Another Na+-dependent type II transporter, (NPT2A/Npt2a/NaPi-IIa), is also important for renal Pi reabsorption in humans. In mice, Npt2c deletion does not lead to hypophosphatemia and rickets because Npt2a compensates for the impaired Pi reabsorption. To clarify the differences between mouse and human, we investigated the relation between NaPi-IIa and NaPi-IIc functions in opossum kidney (OK) cells. METHODS We cloned NaPi-IIc from OK cells and created opossum NaPi-IIc (oNaPi-IIc) antibodies. We used oNaPi-IIc small interference (si)RNA and investigated the role of NaPi-IIc in Pi transport in OK cells. RESULTS We cloned opossum kidney NaPi-IIc cDNAs encoding 622 amino acid proteins (variant1) and examined their pH- and sodium-dependency. The antibodies reacted specifically with 75-kDa and 150-kDa protein bands, and the siRNA of NaPi-IIc markedly suppressed endogenous oNaPi-IIc in OK cells. Treatment with siRNA significantly suppressed the expression of NaPi-4 (NaPi-IIa) protein and mRNA. oNaPi-IIc siRNA also suppressed Na+/H+ exchanger regulatory factor 1 expression in OK cells. CONCLUSION These findings suggest that NaPi-IIc is important for the expression of NaPi-IIa (NaPi-4) protein in OK cells. Suppression of Npt2c may downregulate Npt2a function in HHRH patients.
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Affiliation(s)
- Toru Fujii
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Yuji Shiozaki
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Hiroko Segawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Shiori Nishiguchi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ai Hanazaki
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Miwa Noguchi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ruri Kirino
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Sumire Sasaki
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Kazuya Tanifuji
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Megumi Koike
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Mizuki Yokoyama
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Yuki Arima
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ichiro Kaneko
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Sawako Tatsumi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Mikiko Ito
- Human Science and Environment, University of Hyogo Graduate School, Hyogo, Japan
| | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan.
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16
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Bergwitz C, Miyamoto KI. Hereditary hypophosphatemic rickets with hypercalciuria: pathophysiology, clinical presentation, diagnosis and therapy. Pflugers Arch 2018; 471:149-163. [PMID: 30109410 DOI: 10.1007/s00424-018-2184-2] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 07/06/2018] [Accepted: 07/10/2018] [Indexed: 12/24/2022]
Abstract
Hereditary hypophosphatemic rickets with hypercalciuria (HHRH; OMIM: 241530) is a rare autosomal recessive disorder with an estimated prevalence of 1:250,000 that was originally described by Tieder et al. Individuals with HHRH carry compound-heterozygous or homozygous (comp/hom) loss-of-function mutations in the sodium-phosphate co-transporter NPT2c. These mutations result in the development of urinary phosphate (Pi) wasting and hypophosphatemic rickets, bowing, and short stature, as well as appropriately elevated 1,25(OH)2D levels, which sets this fibroblast growth factor 23 (FGF23)-independent disorder apart from the more common X-linked hypophosphatemia. The elevated 1,25(OH)2D levels in turn result in hypercalciuria due to enhanced intestinal calcium absorption and reduced parathyroid hormone (PTH)-dependent calcium-reabsorption in the distal renal tubules, leading to the development of kidney stones and/or nephrocalcinosis in approximately half of the individuals with HHRH. Even heterozygous NPT2c mutations are frequently associated with isolated hypercalciuria (IH), which increases the risk of kidney stones or nephrocalcinosis threefold in affected individuals compared with the general population. Bone disease is generally absent in individuals with IH, in contrast to those with HHRH. Treatment of HHRH and IH consists of monotherapy with oral Pi supplements, while active vitamin D analogs are contraindicated, mainly because the endogenous 1,25(OH)2D levels are already elevated but also to prevent further worsening of the hypercalciuria. Long-term studies to determine whether oral Pi supplementation alone is sufficient to prevent renal calcifications and bone loss, however, are lacking. It is also unknown how therapy should be monitored, whether secondary hyperparathyroidism can develop, and whether Pi requirements decrease with age, as observed in some FGF23-dependent hypophosphatemic disorders, or whether this can lead to osteoporosis.
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Affiliation(s)
- Clemens Bergwitz
- Section Endocrinology and Metabolism, Yale University School of Medicine, Anlyan Center, Office S117, Lab S110, 1 Gilbert Street, New Haven, CT 06519, USA.
| | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
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17
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Shiozaki Y, Segawa H, Ohnishi S, Ohi A, Ito M, Kaneko I, Kido S, Tatsumi S, Miyamoto KI. Relationship between sodium-dependent phosphate transporter (NaPi-IIc) function and cellular vacuole formation in opossum kidney cells. THE JOURNAL OF MEDICAL INVESTIGATION 2017; 62:209-18. [PMID: 26399350 DOI: 10.2152/jmi.62.209] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
NaPi-IIc/SLC34A3 is a sodium-dependent inorganic phosphate (Pi) transporter in the renal proximal tubules and its mutations cause hereditary hypophosphatemic rickets with hypercalciuria (HHRH). In the present study, we created a specific antibody for opossum SLC34A3, NaPi-IIc (oNaPi-IIc), and analyzed its localization and regulation in opossum kidney cells (a tissue culture model of proximal tubular cells). Immunoreactive oNaPi-IIc protein levels increased during the proliferative phase and decreased during differentiation. Moreover, stimulating cell growth upregulated oNaPi-IIc protein levels, whereas suppressing cell proliferation downregulated oNaPi-IIc protein levels. Immunocytochemistry revealed that endogenous and exogenous oNaPi-IIc proteins localized at the protrusion of the plasma membrane, which is a phosphatidylinositol 4,5-bisphosphate (PIP2) rich-membrane, and at the intracellular vacuolar membrane. Exogenous NaPi-IIc also induced cellular vacuoles and localized in the plasma membrane. The ability to form vacuoles is specific to electroneutral NaPi-IIc, and not electrogenic NaPi-IIa or NaPi-IIb. In addition, mutations of NaPi-IIc (S138F and R468W) in HHRH did not cause cellular PIP2-rich vacuoles. In conclusion, our data anticipate that NaPi-IIc may regulate PIP2 production at the plasma membrane and cellular vesicle formation.
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Affiliation(s)
- Yuji Shiozaki
- Department of Molecular Nutrition, University of Tokushima Graduate School
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18
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Tatsumi S, Miyagawa A, Kaneko I, Shiozaki Y, Segawa H, Miyamoto KI. Regulation of renal phosphate handling: inter-organ communication in health and disease. J Bone Miner Metab 2016; 34:1-10. [PMID: 26296817 DOI: 10.1007/s00774-015-0705-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 07/16/2015] [Indexed: 01/18/2023]
Abstract
In this review, we focus on the interconnection of inorganic phosphate (Pi) homeostasis in the network of the bone-kidney, parathyroid-kidney, intestine-kidney, and liver-kidney axes. Such a network of organ communication is important for body Pi homeostasis. Normalization of serum Pi levels is a clinical target in patients with chronic kidney disease (CKD). Particularly, disorders of the fibroblast growth factor 23/klotho system are observed in early CKD. Identification of phosphaturic factors from the intestine and liver may enhance our understanding of body Pi homeostasis and Pi metabolism disturbances in CKD patients.
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Affiliation(s)
- Sawako Tatsumi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Atsumi Miyagawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ichiro Kaneko
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Yuji Shiozaki
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Hiroko Segawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan.
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19
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Abstract
Recent studies of inherited disorders of phosphate metabolism have shed new light on the understanding of phosphate metabolism. Phosphate has important functions in the body and several mechanisms have evolved to regulate phosphate balance including vitamin D, parathyroid hormone and phosphatonins such as fibroblast growth factor-23 (FGF23). Disorders of phosphate homeostasis leading to hypo- and hyperphosphataemia are common and have clinical and biochemical consequences. Notably, recent studies have linked hyperphosphataemia with an increased risk of cardiovascular disease. This review outlines the recent advances in the understanding of phosphate homeostasis and describes the causes, investigation and management of hypo- and hyperphosphataemia.
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Affiliation(s)
- P Manghat
- Department of Chemical Pathology, Darent Valley Hospital, Dartford, UK
| | - R Sodi
- Department of Biochemistry, NHS Lanarkshire, East Kilbride, UK
| | - R Swaminathan
- Department of Chemical Pathology, St. Thomas Hospital, London, UK
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20
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The SLC34 family of sodium-dependent phosphate transporters. Pflugers Arch 2013; 466:139-53. [PMID: 24352629 DOI: 10.1007/s00424-013-1418-6] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 12/01/2013] [Accepted: 12/02/2013] [Indexed: 12/27/2022]
Abstract
The SLC34 family of sodium-driven phosphate cotransporters comprises three members: NaPi-IIa (SLC34A1), NaPi-IIb (SLC34A2), and NaPi-IIc (SLC34A3). These transporters mediate the translocation of divalent inorganic phosphate (HPO4 (2-)) together with two (NaPi-IIc) or three sodium ions (NaPi-IIa and NaPi-IIb), respectively. Consequently, phosphate transport by NaPi-IIa and NaPi-IIb is electrogenic. NaPi-IIa and NaPi-IIc are predominantly expressed in the brush border membrane of the proximal tubule, whereas NaPi-IIb is found in many more organs including the small intestine, lung, liver, and testis. The abundance and activity of these transporters are mostly regulated by changes in their expression at the cell surface and are determined by interactions with proteins involved in scaffolding, trafficking, or intracellular signaling. All three transporters are highly regulated by factors including dietary phosphate status, hormones like parathyroid hormone, 1,25-OH2 vitamin D3 or FGF23, electrolyte, and acid-base status. The physiological relevance of the three members of the SLC34 family is underlined by rare Mendelian disorders causing phosphaturia, hypophosphatemia, or ectopic organ calcifications.
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Nomura K, Tatsumi S, Miyagawa A, Shiozaki Y, Sasaki S, Kaneko I, Ito M, Kido S, Segawa H, Sano M, Fukuwatari T, Shibata K, Miyamoto KI. Hepatectomy-related hypophosphatemia: a novel phosphaturic factor in the liver-kidney axis. J Am Soc Nephrol 2013; 25:761-72. [PMID: 24262791 DOI: 10.1681/asn.2013060569] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Marked hypophosphatemia is common after major hepatic resection, but the pathophysiologic mechanism remains unknown. We used a partial hepatectomy (PH) rat model to investigate the molecular basis of hypophosphatemia. PH rats exhibited hypophosphatemia and hyperphosphaturia. In renal and intestinal brush-border membrane vesicles isolated from PH rats, Na(+)-dependent phosphate (Pi) uptake decreased by 50%-60%. PH rats also exhibited significantly decreased levels of renal and intestinal Na(+)-dependent Pi transporter proteins (NaPi-IIa [NaPi-4], NaPi-IIb, and NaPi-IIc). Parathyroid hormone was elevated at 6 hours after PH. Hyperphosphaturia persisted, however, even after thyroparathyroidectomy in PH rats. Moreover, DNA microarray data revealed elevated levels of nicotinamide phosphoribosyltransferase (Nampt) mRNA in the kidney after PH, and Nampt protein levels and total NAD concentration increased significantly in the proximal tubules. PH rats also exhibited markedly increased levels of the Nampt substrate, urinary nicotinamide (NAM), and NAM catabolites. In vitro analyses using opossum kidney cells revealed that NAM alone did not affect endogenous NaPi-4 levels. However, in cells overexpressing Nampt, the addition of NAM led to a marked decrease in cell surface expression of NaPi-4 that was blocked by treatment with FK866, a specific Nampt inhibitor. Furthermore, FK866-treated mice showed elevated renal Pi reabsorption and hypophosphaturia. These findings indicate that hepatectomy-induced hypophosphatemia is due to abnormal NAM metabolism, including Nampt activation in renal proximal tubular cells.
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Affiliation(s)
- Kengo Nomura
- Department of Molecular Nutrition Institution of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan; and
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Affiliation(s)
- Jürg Biber
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, CH-8057 Zurich, Switzerland; , ,
| | - Nati Hernando
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, CH-8057 Zurich, Switzerland; , ,
| | - Ian Forster
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, CH-8057 Zurich, Switzerland; , ,
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Abstract
PURPOSE OF REVIEW Description of the recent advances on the regulation of phosphate metabolism, gene mutations, and new approaches to treatment in patients with hypophosphatemic rickets. RECENT FINDINGS Fibroblast growth factor 23 (FGF23) overproduction may be a primary cause of hypophosphatemic rickets. Inactivating mutations of phosphate-regulating gene with homologies to endopeptidases on the X chromosome, dentin matrix acidic phosphoprotein 1, and ectonucleotide pyrophosphatase/phosphodiesterase 1 are associated with X-linked hypophosphatemic rickets, autosomal recessive hypophosphatemic rickets 1, and autosomal recessive hypophosphatemic rickets 2, respectively. Activating mutations of FGF23 gene is the cause of autosomal dominant hypophosphatemic rickets. Iron deficiency may affect autosomal dominant hypophosphatemic rickets phenotype by regulating FGF23 production.Current treatment with activated vitamin D metabolites and oral inorganic phosphate salts may partially correct skeletal lesions and linear growth in patients with hypophosphatemic rickets. However, some patients have poor improvement by the current treatment. SUMMARY Identification of the causative mutation in patients with hypophosphatemic rickets may be useful to confirm the diagnosis and probably for prognosis. Inhibition of FGF23 overproduction by anti-FGF23 neutralizing antibodies could be a future approach for treatment of patients with FGF23-dependent hypophosphatemic rickets.
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Affiliation(s)
- Giampiero I Baroncelli
- Pediatric Unit I, Department of Obstetrics, Gynecology and Pediatrics, University-Hospital, Pisa, Italy.
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Forster IC, Hernando N, Biber J, Murer H. Phosphate transport kinetics and structure-function relationships of SLC34 and SLC20 proteins. CURRENT TOPICS IN MEMBRANES 2012. [PMID: 23177991 DOI: 10.1016/b978-0-12-394316-3.00010-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Transport of inorganic phosphate (P(i)) is mediated by proteins belonging to two solute carrier families (SLC20 and SLC34). Members of both families transport P(i) using the electrochemical gradient for Na(+). The role of the SLC34 members as essential players in mammalian P(i) homeostasis is well established, whereas that of SLC20 proteins is less well defined. The SLC34 family comprises the following three isoforms that preferentially cotransport divalent P(i) and are expressed in epithelial tissue: the renal NaPi-IIa and NaPi-IIc are responsible for reabsorbing P(i) in the proximal tubule, whereas NaPi-IIb is more ubiquitously expressed, including the small intestine, where it mediates dietary P(i) absorption. The SLC20 family comprises two members (PiT-1, PiT-2) that preferentially cotransport monovalent P(i) and are expressed in epithelial as well as nonepithelial tissue. The transport kinetics of members of both families have been characterized in detail using heterologous expression in Xenopus oocytes. For the electrogenic NaPi-IIa/b, and PiT-1,-2, conventional electrophysiological techniques together with radiotracer methods have been applied, as well as time-resolved fluorometric measurements that allow new insights into local conformational changes of the protein during the cotransport cycle. For the electroneutral NaPi-IIc, conventional tracer uptake and fluorometry have been used to elucidate its transport properties. The 3-D structures of these proteins remain unresolved and structure-function studies have so far concentrated on defining the topology and identifying sites of functional importance.
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Affiliation(s)
- Ian C Forster
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Winterthurerstrasse, Zurich, Switzerland.
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