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Abu Obaid A, Ivandic I, Korsching SI. Deciphering the function of the fifth class of Gα proteins: regulation of ionic homeostasis as unifying hypothesis. Cell Mol Life Sci 2024; 81:213. [PMID: 38727814 PMCID: PMC11087313 DOI: 10.1007/s00018-024-05228-w] [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: 02/26/2024] [Revised: 04/02/2024] [Accepted: 04/04/2024] [Indexed: 05/13/2024]
Abstract
Trimeric G proteins transduce signals from a superfamily of receptors and each G protein controls a wide range of cellular and systemic functions. Their highly conserved alpha subunits fall in five classes, four of which have been well investigated (Gs, Gi, G12, Gq). In contrast, the function of the fifth class, Gv is completely unknown, despite its broad occurrence and evolutionary ancient origin (older than metazoans). Here we show a dynamic presence of Gv mRNA in several organs during early development of zebrafish, including the hatching gland, the pronephros and several cartilage anlagen, employing in situ hybridisation. Next, we generated a Gv frameshift mutation in zebrafish and observed distinct phenotypes such as reduced oviposition, premature hatching and craniofacial abnormalities in bone and cartilage of larval zebrafish. These phenotypes could suggest a disturbance in ionic homeostasis as a common denominator. Indeed, we find reduced levels of calcium, magnesium and potassium in the larvae and changes in expression levels of the sodium potassium pump atp1a1a.5 and the sodium/calcium exchanger ncx1b in larvae and in the adult kidney, a major osmoregulatory organ. Additionally, expression of sodium chloride cotransporter slc12a3 and the anion exchanger slc26a4 is altered in complementary ways in adult kidney. It appears that Gv may modulate ionic homeostasis in zebrafish during development and in adults. Our results constitute the first insight into the function of the fifth class of G alpha proteins.
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Affiliation(s)
- Asmaa Abu Obaid
- Institute of Genetics, Faculty of Mathematics and Natural Sciences of the University at Cologne, Zülpicher Str. 47A, 50674, Cologne, Germany
- Department of Optometry, Faculty of Modern Sciences, The Arab American University, Yousef Asfour Street, Ramallah, Palestine
| | - Ivan Ivandic
- Institute of Genetics, Faculty of Mathematics and Natural Sciences of the University at Cologne, Zülpicher Str. 47A, 50674, Cologne, Germany
| | - Sigrun I Korsching
- Institute of Genetics, Faculty of Mathematics and Natural Sciences of the University at Cologne, Zülpicher Str. 47A, 50674, Cologne, Germany.
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Majmundar AJ, Widmeier E, Heneghan JF, Daga A, Wu CHW, Buerger F, Hugo H, Ullah I, Amar A, Ottlewski I, Braun DA, Jobst-Schwan T, Lawson JA, Zahoor MY, Rodig NM, Tasic V, Nelson CP, Khaliq S, Schönauer R, Halbritter J, Sayer JA, Fathy HM, Baum MA, Shril S, Mane S, Alper SL, Hildebrandt F. OXGR1 is a candidate disease gene for human calcium oxalate nephrolithiasis. Genet Med 2023; 25:100351. [PMID: 36571463 PMCID: PMC9992313 DOI: 10.1016/j.gim.2022.11.019] [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: 08/08/2022] [Revised: 11/23/2022] [Accepted: 11/27/2022] [Indexed: 12/12/2022] Open
Abstract
PURPOSE Nephrolithiasis (NL) affects 1 in 11 individuals worldwide, leading to significant patient morbidity. NL is associated with nephrocalcinosis (NC), a risk factor for chronic kidney disease. Causative genetic variants are detected in 11% to 28% of NL and/or NC, suggesting that additional NL/NC-associated genetic loci await discovery. Therefore, we employed genomic approaches to discover novel genetic forms of NL/NC. METHODS Exome sequencing and directed sequencing of the OXGR1 locus were performed in a worldwide NL/NC cohort. Putatively deleterious, rare OXGR1 variants were functionally characterized. RESULTS Exome sequencing revealed a heterozygous OXGR1 missense variant (c.371T>G, p.L124R) cosegregating with calcium oxalate NL and/or NC disease in an autosomal dominant inheritance pattern within a multigenerational family with 5 affected individuals. OXGR1 encodes 2-oxoglutarate (α-ketoglutarate [AKG]) receptor 1 in the distal nephron. In response to its ligand AKG, OXGR1 stimulates the chloride-bicarbonate exchanger, pendrin, which also regulates transepithelial calcium transport in cortical connecting tubules. Strong amino acid conservation in orthologs and paralogs, severe in silico prediction scores, and extreme rarity in exome population databases suggested that the variant was deleterious. Interrogation of the OXGR1 locus in 1107 additional NL/NC families identified 5 additional deleterious dominant variants in 5 families with calcium oxalate NL/NC. Rare, potentially deleterious OXGR1 variants were enriched in patients with NL/NC compared with Exome Aggregation Consortium controls (χ2 = 7.117, P = .0076). Wild-type OXGR1-expressing Xenopus oocytes exhibited AKG-responsive Ca2+ uptake. Of 5 NL/NC-associated missense variants, 5 revealed impaired AKG-dependent Ca2+ uptake, demonstrating loss of function. CONCLUSION Rare, dominant loss-of-function OXGR1 variants are associated with recurrent calcium oxalate NL/NC disease.
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Affiliation(s)
- Amar J Majmundar
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Eugen Widmeier
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - John F Heneghan
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Ankana Daga
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Chen-Han Wilfred Wu
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Division of Genetics and Genomics, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Departments of Urology and Genetics and Genome Sciences, School of Medicine, Case Western Reserve University and University Hospitals, Cleveland, OH
| | - Florian Buerger
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Hannah Hugo
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Ihsan Ullah
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Molecular Biology Laboratory, Institute of Biochemistry and Biotechnology, University of Veterinary & Animal Sciences, Lahore, Pakistan
| | - Ali Amar
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Department of Human Genetics and Molecular Biology, University of Health Sciences Lahore, Lahore, Pakistan
| | - Isabel Ottlewski
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Daniela A Braun
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Tilman Jobst-Schwan
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Department of Nephrology and Hypertension, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jennifer A Lawson
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Muhammad Yasir Zahoor
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Molecular Biology Laboratory, Institute of Biochemistry and Biotechnology, University of Veterinary & Animal Sciences, Lahore, Pakistan
| | - Nancy M Rodig
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Velibor Tasic
- Medical Faculty Skopje, University Children's Hospital, Skopje, North Macedonia
| | - Caleb P Nelson
- Department of Urology, Boston Children's Hospital and Department of Surgery, Harvard Medical School, Boston, MA
| | - Shagufta Khaliq
- Department of Human Genetics and Molecular Biology, University of Health Sciences Lahore, Lahore, Pakistan
| | - Ria Schönauer
- Division of Nephrology, Department of Internal Medicine, University of Leipzig, Leipzig, Germany; Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jan Halbritter
- Division of Nephrology, Department of Internal Medicine, University of Leipzig, Leipzig, Germany; Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - John A Sayer
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom; The Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle, United Kingdom; NIHR Newcastle Biomedical Research Centre, Newcastle, United Kingdom
| | - Hanan M Fathy
- Pediatric Nephrology Unit, Alexandria University, Alexandria, Egypt
| | - Michelle A Baum
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Shirlee Shril
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Shrikant Mane
- Department of Genetics and Yale Center for Mendelian Genomics, Yale University School of Medicine, New Haven, CT
| | - Seth L Alper
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA.
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3
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Anastasio P, Trepiccione F, De Santo NG, Capasso G, Viggiano D, Capolongo G. Regulation of urinary calcium excretion by vasopressin. Clin Kidney J 2020; 13:873-877. [PMID: 33123363 PMCID: PMC7577769 DOI: 10.1093/ckj/sfaa134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Indexed: 12/17/2022] Open
Abstract
Background The antidiuretic hormone (ADH) or arginine vasopressin (AVP) regulates the body's water balance. Recently, modifications in AVP levels have been related to osteoporosis during ageing and microgravity/bed rest. Therefore the present study was devised to assess whether the absence of AVP, as in patients with central diabetes insipidus (CDI), modulates renal calcium excretion. Methods We retrospectively analysed data from 12 patients with CDI with measured 24-h urinary excretion levels of calcium. Data were available at the moment of the diagnosis when patients were drug-free and after therapy with dDAVP, an analog of AVP. Hypercalciuria was defined as 24-h urinary Ca2+ >275 mg/day in males and >250 mg/day in females and a urinary calcium (Ca):creatinine (Cr) ratio >0.20 mg/mg. Results Untreated CDI patients had a daily urinary Ca2+ excretion of 383 ± 47 mg/day and a urinary Ca:Cr ratio of 0.26 ± 0.38 mg/mg. The urine osmolarity significantly increased after the administration of dDAVP by 210% and the urinary flow decreased by 72%. Furthermore, the estimated glomerular filtration rate (eGFR) increased by 7%, which did not reach statistical significance. dDAVP treatment did not significantly modify the urinary Ca2+ concentration; however, the daily calcium excretion and the urinary Ca:Cr ratio were significantly decreased (160 ± 27 mg/day and 0.11 ± 0.02 mg/mg, respectively). Conclusions Patients with CDI show hypercalciuria even though urine is more diluted than normal controls, and dDAVP reverses this effect. These data support the intriguing relationship between AVP and osteoporosis in ageing and microgravity/bed rest.
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Affiliation(s)
- Pietro Anastasio
- Department of Translational Medical Sciences, University of Campania 'L.Vanvitelli', Naples, Italy
| | - Francesco Trepiccione
- Department of Translational Medical Sciences, University of Campania 'L.Vanvitelli', Naples, Italy.,BIOGEM, Ariano Irpino, Italy
| | | | - Giovambattista Capasso
- Department of Translational Medical Sciences, University of Campania 'L.Vanvitelli', Naples, Italy.,BIOGEM, Ariano Irpino, Italy
| | - Davide Viggiano
- Department of Translational Medical Sciences, University of Campania 'L.Vanvitelli', Naples, Italy.,BIOGEM, Ariano Irpino, Italy.,Department of Medicine and Health Sciences, University of Molise, Campobasso, Italy
| | - Giovanna Capolongo
- Department of Translational Medical Sciences, University of Campania 'L.Vanvitelli', Naples, Italy
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Touré A. Importance of SLC26 Transmembrane Anion Exchangers in Sperm Post-testicular Maturation and Fertilization Potential. Front Cell Dev Biol 2019; 7:230. [PMID: 31681763 PMCID: PMC6813192 DOI: 10.3389/fcell.2019.00230] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 09/26/2019] [Indexed: 12/17/2022] Open
Abstract
In mammals, sperm cells produced within the testis are structurally differentiated but remain immotile and are unable to fertilize the oocyte unless they undergo a series of maturation events during their transit in the male and female genital tracts. This post-testicular functional maturation is known to rely on the micro-environment of both male and female genital tracts, and is tightly controlled by the pH of their luminal milieus. In particular, within the epididymis, the establishment of a low bicarbonate (HCO3–) concentration contributes to luminal acidification, which is necessary for sperm maturation and subsequent storage in a quiescent state. Following ejaculation, sperm is exposed to the basic pH of the female genital tract and bicarbonate (HCO3–), calcium (Ca2+), and chloride (Cl–) influxes induce biochemical and electrophysiological changes to the sperm cells (cytoplasmic alkalinization, increased cAMP concentration, and protein phosphorylation cascades), which are indispensable for the acquisition of fertilization potential, a process called capacitation. Solute carrier 26 (SLC26) members are conserved membranous proteins that mediate the transport of various anions across the plasma membrane of epithelial cells and constitute important regulators of pH and HCO3– concentration. Most SLC26 members were shown to physically interact and cooperate with the cystic fibrosis transmembrane conductance regulator channel (CFTR) in various epithelia, mainly by stimulating its Cl– channel activity. Among SLC26 members, the function of SLC26A3, A6, and A8 were particularly investigated in the male genital tract and the sperm cells. In this review, we will focus on SLC26s contributions to ionic- and pH-dependent processes during sperm post-testicular maturation. We will specify the current knowledge regarding their functions, based on data from the literature generated by means of in vitro and in vivo studies in knock-out mouse models together with genetic studies of infertile patients. We will also discuss the limits of those studies, the current research gaps and identify some key points for potential developments in this field.
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Affiliation(s)
- Aminata Touré
- INSERM U1016, Centre National de la Recherche Scientifique, UMR 8104, Institut Cochin, Université de Paris, Paris, France
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Alshahrani S, Rapoport RM, Zahedi K, Jiang M, Nieman M, Barone S, Meredith AL, Lorenz JN, Rubinstein J, Soleimani M. The non-diuretic hypotensive effects of thiazides are enhanced during volume depletion states. PLoS One 2017; 12:e0181376. [PMID: 28719636 PMCID: PMC5515454 DOI: 10.1371/journal.pone.0181376] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 06/29/2017] [Indexed: 12/25/2022] Open
Abstract
Thiazide derivatives including Hydrochlorothiazide (HCTZ) represent the most common treatment of mild to moderate hypertension. Thiazides initially enhance diuresis via inhibition of the kidney Na+-Cl- Cotransporter (NCC). However, chronic volume depletion and diuresis are minimal while lowered blood pressure (BP) is maintained on thiazides. Thus, a vasodilator action of thiazides is proposed, likely via Ca2+-activated K+ (BK) channels in vascular smooth muscles. This study ascertains the role of volume depletion induced by salt restriction or salt wasting in NCC KO mice on the non-diuretic hypotensive action of HCTZ. HCTZ (20mg/kg s.c.) lowered BP in 1) NCC KO on a salt restricted diet but not with normal diet; 2) in volume depleted but not in volume resuscitated pendrin/NCC dKO mice; the BP reduction occurs without any enhancement in salt excretion or reduction in cardiac output. HCTZ still lowered BP following treatment of NCC KO on salt restricted diet with paxilline (8 mg/kg, i.p.), a BK channel blocker, and in BK KO and BK/NCC dKO mice on salt restricted diet. In aortic rings from NCC KO mice on normal and low salt diet, HCTZ did not alter and minimally decreased maximal phenylephrine contraction, respectively, while contractile sensitivity remained unchanged. These results demonstrate 1) the non-diuretic hypotensive effects of thiazides are augmented with volume depletion and 2) that the BP reduction is likely the result of HCTZ inhibition of vasoconstriction through a pathway dependent on factors present in vivo, is unrelated to BK channel activation, and involves processes associated with intravascular volume depletion.
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Affiliation(s)
- Saeed Alshahrani
- Department of Pharmacology and Cell Biophysics, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
| | - Robert M. Rapoport
- Department of Pharmacology and Cell Biophysics, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
| | - Kamyar Zahedi
- Center on Genetics of Transport and Epithelial Biology, University of Cincinnati, Cincinnati, OH, United States of America
- Division of Nephrology, Department of Medicine, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
- Research Services, Veterans Affairs Medical Center, Cincinnati, OH, United States of America
| | - Min Jiang
- Division of Cardiology, Department of Medicine, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
| | - Michelle Nieman
- Department of Physiology, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
| | - Sharon Barone
- Center on Genetics of Transport and Epithelial Biology, University of Cincinnati, Cincinnati, OH, United States of America
- Division of Nephrology, Department of Medicine, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
- Research Services, Veterans Affairs Medical Center, Cincinnati, OH, United States of America
| | - Andrea L. Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - John N. Lorenz
- Department of Physiology, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
| | - Jack Rubinstein
- Division of Cardiology, Department of Medicine, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
| | - Manoocher Soleimani
- Department of Pharmacology and Cell Biophysics, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
- Center on Genetics of Transport and Epithelial Biology, University of Cincinnati, Cincinnati, OH, United States of America
- Division of Nephrology, Department of Medicine, University of Cincinnati, College of Medicine, Cincinnati, OH, United States of America
- Research Services, Veterans Affairs Medical Center, Cincinnati, OH, United States of America
- * E-mail:
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Khairallah P, Isakova T, Asplin J, Hamm L, Dobre M, Rahman M, Sharma K, Leonard M, Miller E, Jaar B, Brecklin C, Yang W, Wang X, Feldman H, Wolf M, Scialla JJ. Acid Load and Phosphorus Homeostasis in CKD. Am J Kidney Dis 2017. [PMID: 28645705 DOI: 10.1053/j.ajkd.2017.04.022] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND The kidneys maintain acid-base homeostasis through excretion of acid as either ammonium or as titratable acids that primarily use phosphate as a buffer. In chronic kidney disease (CKD), ammoniagenesis is impaired, promoting metabolic acidosis. Metabolic acidosis stimulates phosphaturic hormones, parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF-23) in vitro, possibly to increase urine titratable acid buffers, but this has not been confirmed in humans. We hypothesized that higher acid load and acidosis would associate with altered phosphorus homeostasis, including higher urinary phosphorus excretion and serum PTH and FGF-23. STUDY DESIGN Cross-sectional. SETTING & PARTICIPANTS 980 participants with CKD enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study. PREDICTORS Net acid excretion as measured in 24-hour urine, potential renal acid load (PRAL) estimated from food frequency questionnaire responses, and serum bicarbonate concentration < 22 mEq/L. OUTCOME & MEASUREMENTS 24-hour urine phosphorus and calcium excretion and serum phosphorus, FGF-23, and PTH concentrations. RESULTS Using linear and log-linear regression adjusted for demographics, kidney function, comorbid conditions, body mass index, diuretic use, and 24-hour urine creatinine excretion, we found that 24-hour urine phosphorus excretion was higher at higher net acid excretion, higher PRAL, and lower serum bicarbonate concentration (each P<0.05). Serum phosphorus concentration was also higher with higher net acid excretion and lower serum bicarbonate concentration (each P=0.001). Only higher net acid excretion associated with higher 24-hour urine calcium excretion (P<0.001). Neither net acid excretion nor PRAL was associated with FGF-23 or PTH concentrations. PTH, but not FGF-23, concentration (P=0.2) was 26% (95% CI, 13%-40%) higher in participants with a serum bicarbonate concentration <22 versus ≥22 mEq/L (P<0.001). Primary results were similar if stratified by estimated glomerular filtration rate categories or adjusted for iothalamate glomerular filtration rate (n=359), total energy intake, dietary phosphorus, or urine urea nitrogen excretion, when available. LIMITATIONS Possible residual confounding by kidney function or nutrition; urine phosphorus excretion was included in calculation of the titratable acid component of net acid excretion. CONCLUSIONS In CKD, higher acid load and acidosis associate independently with increased circulating phosphorus concentration and augmented phosphaturia, but not consistently with FGF-23 or PTH concentrations. This may be an adaptation that increases titratable acid excretion and thus helps maintain acid-base homeostasis in CKD. Understanding whether administration of base can lower phosphorus concentrations requires testing in interventional trials.
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Affiliation(s)
| | - Tamara Isakova
- Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL; Center for Translational Metabolism and Health, Institute of Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - John Asplin
- Litholink Corp, Laboratory Corporation of America Holdings, Chicago, IL
| | - Lee Hamm
- Department of Medicine, Tulane University School of Medicine, New Orleans, LA
| | - Mirela Dobre
- Department of Medicine, Case Western Reserve University, Cleveland, OH
| | - Mahboob Rahman
- Department of Medicine, Case Western Reserve University, Cleveland, OH
| | - Kumar Sharma
- Department of Medicine, University of San Diego, San Diego, CA
| | - Mary Leonard
- Department of Pediatrics, Stanford University School of Medicine, Palo Alto, CA
| | - Edgar Miller
- Department of Medicine, Prevention and Clinical Research, Johns Hopkins University, Baltimore, MD; Welch Center for Epidemiology, Prevention and Clinical Research, Johns Hopkins University, Baltimore, MD
| | - Bernard Jaar
- Department of Medicine, Prevention and Clinical Research, Johns Hopkins University, Baltimore, MD; Welch Center for Epidemiology, Prevention and Clinical Research, Johns Hopkins University, Baltimore, MD; Nephrology Center of Maryland, Baltimore, MD
| | - Carolyn Brecklin
- Department of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Wei Yang
- Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA
| | - Xue Wang
- Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA
| | - Harold Feldman
- Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA; Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA
| | - Myles Wolf
- Department of Medicine, Duke University School of Medicine, Durham, NC
| | - Julia J Scialla
- Department of Medicine, Duke University School of Medicine, Durham, NC; Duke Clinical Research Institute, Duke University School of Medicine, Durham, NC; Department of Medicine, Durham Veterans Affairs Medical Center, Durham, NC.
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Soleimani M, Barone S, Xu J, Alshahrani S, Brooks M, McCormack FX, Smith RD, Zahedi K. Prostaglandin-E2 Mediated Increase in Calcium and Phosphate Excretion in a Mouse Model of Distal Nephron Salt Wasting. PLoS One 2016; 11:e0159804. [PMID: 27442254 PMCID: PMC4956050 DOI: 10.1371/journal.pone.0159804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 07/10/2016] [Indexed: 01/29/2023] Open
Abstract
Contribution of salt wasting and volume depletion to the pathogenesis of hypercalciuria and hyperphosphaturia is poorly understood. Pendrin/NCC double KO (pendrin/NCC-dKO) mice display severe salt wasting under basal conditions and develop profound volume depletion, prerenal renal failure, and metabolic alkalosis and are growth retarded. Microscopic examination of the kidneys of pendrin/NCC-dKO mice revealed the presence of calcium phosphate deposits in the medullary collecting ducts, along with increased urinary calcium and phosphate excretion. Confirmatory studies revealed decreases in the expression levels of sodium phosphate transporter-2 isoforms a and c, increases in the expression of cytochrome p450 family 4a isotypes 12 a and b, as well as prostaglandin E synthase 1, and cyclooxygenases 1 and 2. Pendrin/NCC-dKO animals also had a significant increase in urinary prostaglandin E2 (PGE-2) and renal content of 20-hydroxyeicosatetraenoic acid (20-HETE) levels. Pendrin/NCC-dKO animals exhibit reduced expression levels of the sodium/potassium/2chloride co-transporter 2 (NKCC2) in their medullary thick ascending limb. Further assessment of the renal expression of NKCC2 isoforms by quantitative real time PCR (qRT-PCR) reveled that compared to WT mice, the expression of NKCC2 isotype F was significantly reduced in pendrin/NCC-dKO mice. Provision of a high salt diet to rectify volume depletion or inhibition of PGE-2 synthesis by indomethacin, but not inhibition of 20-HETE generation by HET0016, significantly improved hypercalciuria and salt wasting in pendrin/NCC dKO mice. Both high salt diet and indomethacin treatment also corrected the alterations in NKCC2 isotype expression in pendrin/NCC-dKO mice. We propose that severe salt wasting and volume depletion, irrespective of the primary originating nephron segment, can secondarily impair the reabsorption of salt and calcium in the thick ascending limb of Henle and/or proximal tubule, and reabsorption of sodium and phosphate in the proximal tubule via processes that are mediated by PGE-2.
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Affiliation(s)
- Manoocher Soleimani
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Research Services, Veterans Affairs Medical Center, Cincinnati, OH, United States of America
- * E-mail:
| | - Sharon Barone
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Research Services, Veterans Affairs Medical Center, Cincinnati, OH, United States of America
| | - Jie Xu
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Saeed Alshahrani
- Department of Pharmacology and Cell Biophysics and, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Marybeth Brooks
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Francis X. McCormack
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Roger D. Smith
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Kamyar Zahedi
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Research Services, Veterans Affairs Medical Center, Cincinnati, OH, United States of America
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Abstract
The H(+) concentration in human blood is kept within very narrow limits, ~40 nmol/L, despite the fact that dietary metabolism generates acid and base loads that are added to the systemic circulation throughout the life of mammals. One of the primary functions of the kidney is to maintain the constancy of systemic acid-base chemistry. The kidney has evolved the capacity to regulate blood acidity by performing three key functions: (i) reabsorb HCO3(-) that is filtered through the glomeruli to prevent its excretion in the urine; (ii) generate a sufficient quantity of new HCO3(-) to compensate for the loss of HCO3(-) resulting from dietary metabolic H(+) loads and loss of HCO3(-) in the urea cycle; and (iii) excrete HCO3(-) (or metabolizable organic anions) following a systemic base load. The ability of the kidney to perform these functions requires that various cell types throughout the nephron respond to changes in acid-base chemistry by modulating specific ion transport and/or metabolic processes in a coordinated fashion such that the urine and renal vein chemistry is altered appropriately. The purpose of the article is to provide the interested reader with a broad review of a field that began historically ~60 years ago with whole animal studies, and has evolved to where we are currently addressing questions related to kidney acid-base regulation at the single protein structure/function level.
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Affiliation(s)
- Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, Los Angeles, CA; Brain Research Institute, UCLA, Los Angeles, CA
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Abstract
The distal convoluted tubule (DCT) is a short nephron segment, interposed between the macula densa and collecting duct. Even though it is short, it plays a key role in regulating extracellular fluid volume and electrolyte homeostasis. DCT cells are rich in mitochondria, and possess the highest density of Na+/K+-ATPase along the nephron, where it is expressed on the highly amplified basolateral membranes. DCT cells are largely water impermeable, and reabsorb sodium and chloride across the apical membrane via electroneurtral pathways. Prominent among this is the thiazide-sensitive sodium chloride cotransporter, target of widely used diuretic drugs. These cells also play a key role in magnesium reabsorption, which occurs predominantly, via a transient receptor potential channel (TRPM6). Human genetic diseases in which DCT function is perturbed have provided critical insights into the physiological role of the DCT, and how transport is regulated. These include Familial Hyperkalemic Hypertension, the salt-wasting diseases Gitelman syndrome and EAST syndrome, and hereditary hypomagnesemias. The DCT is also established as an important target for the hormones angiotensin II and aldosterone; it also appears to respond to sympathetic-nerve stimulation and changes in plasma potassium. Here, we discuss what is currently known about DCT physiology. Early studies that determined transport rates of ions by the DCT are described, as are the channels and transporters expressed along the DCT with the advent of molecular cloning. Regulation of expression and activity of these channels and transporters is also described; particular emphasis is placed on the contribution of genetic forms of DCT dysregulation to our understanding.
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Affiliation(s)
- James A McCormick
- Division of Nephrology & Hypertension, Oregon Health & Science University, & VA Medical Center, Portland, Oregon, United States
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10
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Moss DM, Neary M, Owen A. The role of drug transporters in the kidney: lessons from tenofovir. Front Pharmacol 2014; 5:248. [PMID: 25426075 PMCID: PMC4227492 DOI: 10.3389/fphar.2014.00248] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 10/24/2014] [Indexed: 12/15/2022] Open
Abstract
Tenofovir disoproxil fumarate, the prodrug of nucleotide reverse transcriptase inhibitor tenofovir, shows high efficacy and relatively low toxicity in HIV patients. However, long-term kidney toxicity is now acknowledged as a modest but significant risk for tenofovir-containing regimens, and continuous use of tenofovir in HIV therapy is currently under question by practitioners and researchers. Co-morbidities (hepatitis C, diabetes), low body weight, older age, concomitant administration of potentially nephrotoxic drugs, low CD4 count, and duration of therapy are all risk factors associated with tenofovir-associated tubular dysfunction. Tenofovir is predominantly eliminated via the proximal tubules of the kidney, therefore drug transporters expressed in renal proximal tubule cells are believed to influence tenofovir plasma concentration and toxicity in the kidney. We review here the current evidence that the actions, pharmacogenetics, and drug interactions of drug transporters are relevant factors for tenofovir-associated tubular dysfunction. The use of creatinine and novel biomarkers for kidney damage, and the role that drug transporters play in biomarker disposition, are discussed. The lessons learnt from investigating the role of transporters in tenofovir kidney elimination and toxicity can be utilized for future drug development and clinical management programs.
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Affiliation(s)
- Darren M Moss
- Department of Molecular and Clinical Pharmacology, University of Liverpool Liverpool, UK
| | - Megan Neary
- Department of Molecular and Clinical Pharmacology, University of Liverpool Liverpool, UK
| | - Andrew Owen
- Department of Molecular and Clinical Pharmacology, University of Liverpool Liverpool, UK
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11
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Soleimani M. The multiple roles of pendrin in the kidney. Nephrol Dial Transplant 2014; 30:1257-66. [PMID: 25281699 DOI: 10.1093/ndt/gfu307] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/25/2014] [Indexed: 12/30/2022] Open
Abstract
The [Formula: see text] exchanger pendrin (SLC26A4, PDS) is located on the apical membrane of B-intercalated cells in the kidney cortical collecting duct and the connecting tubules and mediates the secretion of bicarbonate and the reabsorption of chloride. Given its dual function of bicarbonate secretion and chloride reabsorption in the distal tubules, it was thought that pendrin plays important roles in systemic acid-base balance and electrolyte and vascular volume homeostasis under basal conditions. Mice with the genetic deletion of pendrin or humans with inactivating mutations in PDS gene, however, do not display excessive salt and fluid wasting or altered blood pressure under baseline conditions. Very recent reports have unmasked the basis of incongruity between the mild phenotype in mutant mice and the role of pendrin as an important player in salt reabsorption in the distal tubule. These studies demonstrate that pendrin and the Na-Cl cotransporter (NCC; SLC12A3) cross compensate for the loss of each other, therefore masking the role that each transporter plays in salt reabsorption under baseline conditions. In addition, pendrin regulates calcium reabsorption in the distal tubules. Furthermore, combined deletion of pendrin and NCC not only causes severe volume depletion but also results in profound calcium wasting and luminal calcification in medullary collecting ducts. Based on studies in pathophysiological states and the examination of genetically engineered mouse models, the evolving picture points to important roles for pendrin (SLC26A4) in kidney physiology and in disease states. This review summarizes recent advances in the characterization of pendrin and the multiple roles it plays in the kidney, with emphasis on its essential roles in several diverse physiological processes, including chloride homeostasis, vascular volume and blood pressure regulation, calcium excretion and kidney stone formation.
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Affiliation(s)
- Manoocher Soleimani
- Center on Genetics of Transport and Epithelial Biology, University of Cincinnati, Cincinnati, OH, USA Research Services, Veterans Affairs Medical Center, Cincinnati, OH, USA Department of Medicine, University of Cincinnati, Cincinnati, OH, USA
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12
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Alka K, Casey JR. Bicarbonate transport in health and disease. IUBMB Life 2014; 66:596-615. [PMID: 25270914 DOI: 10.1002/iub.1315] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 09/10/2014] [Indexed: 12/28/2022]
Abstract
Bicarbonate (HCO3(-)) has a central place in human physiology as the waste product of mitochondrial energy production and for its role in pH buffering throughout the body. Because bicarbonate is impermeable to membranes, bicarbonate transport proteins are necessary to enable control of bicarbonate levels across membranes. In humans, 14 bicarbonate transport proteins, members of the SLC4 and SLC26 families, function by differing transport mechanisms. In addition, some anion channels and ZIP metal transporters contribute to bicarbonate movement across membranes. Defective bicarbonate transport leads to diseases, including systemic acidosis, brain dysfunction, kidney stones, and hypertension. Altered expression levels of bicarbonate transporters in patients with breast, colon, and lung cancer suggest an important role of these transporters in cancer.
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Affiliation(s)
- Kumari Alka
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
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13
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Soleimani M. SLC26 Cl-/HCO3- exchangers in the kidney: roles in health and disease. Kidney Int 2013; 84:657-66. [PMID: 23636174 PMCID: PMC10947778 DOI: 10.1038/ki.2013.138] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 01/25/2013] [Accepted: 02/14/2013] [Indexed: 12/30/2022]
Abstract
Solute-linked carrier 26 (SLC26) isoforms constitute a conserved family of anion transporters with 10 distinct members. Except for SLC26A5 (prestin), all can operate as multifunctional anion exchangers, with three members (SLC26A7, SLC26A9, and SLC26A11) also capable of functioning as chloride channels. Several SLC26 isoforms can specifically mediate Cl(-)/HCO(3)(-) exchange. These include SLC26A3, A4, A6, A7, A9, and A11, which are expressed in the kidney except for SLC26A3 (DRA), which is predominantly expressed in the intestine. SLC26 Cl(-)/HCO(3)(-) exchanger isoforms display unique nephron segment distribution patterns with distinct subcellular localization in the kidney tubules. Together with studies in pathophysiologic states and the examination of genetically engineered mouse models, the evolving picture points to important roles for the SLC26 family in health and disease states. This review summarizes recent advances in the characterization of the SLC26 Cl(-)/HCO(3)(-) exchangers in the kidney with emphasis on their essential role in diverse physiological processes, including chloride homeostasis, oxalate excretion and kidney stone formation, vascular volume and blood pressure regulation, and acid-base balance.
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Affiliation(s)
- Manoocher Soleimani
- 1] Center on Genetics of Transport and Epithelial Biology, University of Cincinnati, Cincinnati, Ohio, USA [2] Research Services, Veterans Affairs Medical Center, Cincinnati, Ohio, USA [3] Department of Medicine, University of Cincinnati, Cincinnati, Ohio, USA
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14
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Alper SL, Sharma AK. The SLC26 gene family of anion transporters and channels. Mol Aspects Med 2013; 34:494-515. [PMID: 23506885 DOI: 10.1016/j.mam.2012.07.009] [Citation(s) in RCA: 256] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 06/21/2012] [Indexed: 02/08/2023]
Abstract
The phylogenetically ancient SLC26 gene family encodes multifunctional anion exchangers and anion channels transporting a broad range of substrates, including Cl(-), HCO3(-), sulfate, oxalate, I(-), and formate. SLC26 polypeptides are characterized by N-terminal cytoplasmic domains, 10-14 hydrophobic transmembrane spans, and C-terminal cytoplasmic STAS domains, and appear to be homo-oligomeric. SLC26-related SulP proteins of marine bacteria likely transport HCO3(-) as part of oceanic carbon fixation. SulP genes present in antibiotic operons may provide sulfate for antibiotic biosynthetic pathways. SLC26-related Sultr proteins transport sulfate in unicellular eukaryotes and in plants. Mutations in three human SLC26 genes are associated with congenital or early onset Mendelian diseases: chondrodysplasias for SLC26A2, chloride diarrhea for SLC26A3, and deafness with enlargement of the vestibular aqueduct for SLC26A4. Additional disease phenotypes evident only in mouse knockout models include oxalate urolithiasis for Slc26a6 and Slc26a1, non-syndromic deafness for Slc26a5, gastric hypochlorhydria for Slc26a7 and Slc26a9, distal renal tubular acidosis for Slc26a7, and male infertility for Slc26a8. STAS domains are required for cell surface expression of SLC26 proteins, and contribute to regulation of the cystic fibrosis transmembrane regulator in complex, cell- and tissue-specific ways. The protein interactomes of SLC26 polypeptides are under active investigation.
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Affiliation(s)
- Seth L Alper
- Renal Division and Division of Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
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15
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Wangemann P. The role of pendrin in the development of the murine inner ear. Cell Physiol Biochem 2011; 28:527-34. [PMID: 22116367 DOI: 10.1159/000335113] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/19/2011] [Indexed: 12/13/2022] Open
Abstract
Enlargement of the vestibular aqueduct (EVA) is a common inner ear malformation found in children with sensorineural hearing loss that is frequently associated with loss-of-function or hypo-function mutations of SLC26A4. SLC26A4 codes for pendrin, which is a protein that is expressed in apical membranes of selected epithelia and functions as an anion exchanger. The comparatively high prevalence of EVA provides a strong imperative to develop rational interventions that delay, ameliorate or prevent hearing loss associated with this phenotype. The development of rational interventions requires a fundamental understanding of the role that pendrin plays in the normal development of hearing, as well as a detailed understanding of the pathobiologic mechanisms that, in the absence of fully functional pendrin, lead to an unstable hearing phenotype, with fluctuating or progressive loss of hearing. This review summarizes studies in mouse models that have focused on delineating the role of pendrin in the physiology of the inner ear and the pathobiology that leads to hearing loss.
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Affiliation(s)
- Philine Wangemann
- Anatomy & Physiology Department, Kansas State University, Manhattan, Kansas 66506, USA.
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Dror AA, Brownstein Z, Avraham KB. Integration of human and mouse genetics reveals pendrin function in hearing and deafness. Cell Physiol Biochem 2011; 28:535-44. [PMID: 22116368 DOI: 10.1159/000335163] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/28/2011] [Indexed: 12/21/2022] Open
Abstract
Genomic technology has completely changed the way in which we are able to diagnose human genetic mutations. Genomic techniques such as the polymerase chain reaction, linkage analysis, Sanger sequencing, and most recently, massively parallel sequencing, have allowed researchers and clinicians to identify mutations for patients with Pendred syndrome and DFNB4 non-syndromic hearing loss. While thus far most of the mutations have been in the SLC26A4 gene coding for the pendrin protein, other genetic mutations may contribute to these phenotypes as well. Furthermore, mouse models for deafness have been invaluable to help determine the mechanisms for SLC26A4-associated deafness. Further work in these areas of research will help define genotype-phenotype correlations and develop methods for therapy in the future.
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Affiliation(s)
- Amiel A Dror
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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