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Zhen T, Li Y, Guo Q, Yao S, You Y, Lei B. Pathogenicity and Function Analysis of Two Novel SLC4A11 Variants in Patients With Congenital Hereditary Endothelial Dystrophy. Transl Vis Sci Technol 2023; 12:1. [PMID: 37787991 PMCID: PMC10561774 DOI: 10.1167/tvst.12.10.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 08/10/2023] [Indexed: 10/04/2023] Open
Abstract
Purpose The purpose of this study was to explore the pathogenicity and function of two novel SLC4A11 variants associated with congenital hereditary endothelial dystrophy (CHED) and to study the function of a SLC4A11 (K263R) mutant in vitro. Methods Ophthalmic examinations were performed on a 28-year-old male proband with CHED. Whole-exome and Sanger sequencing were applied for mutation screening. Bioinformatics and pathogenicity analysis were performed. HEK293T cells were transfected with the plasmids of empty vector, wild-type SLC4A11, and SLC4A11 (K263R) mutant. The transfected cells were treated with SkQ1. Oxygen consumption, cellular reactive oxygen species (ROS) level, mitochondrial membrane potential, and apoptosis rate were measured. Results The proband had poor visual acuity with nystagmus since childhood. Corneal foggy opacity was evident in both eyes. Two novel SLC4A11 variants were detected. Sanger sequencing showed that the proband's father and sister carried c.1464-1G>T variant, and the proband's mother and sister carried c.788A>G (p.Lys263Arg) variant. Based on the American College of Medical Genetics (ACMG) guidelines, SLC4A11 c.1464-1G>T was pathogenic, whereas c.788A>G, p.K263R was a variant of undetermined significance. In vitro, SLC4A11 (K263R) variant increased ROS level and apoptosis rate. Decrease in mitochondrial membrane potential and oxygen consumption rate were remarkable. Furthermore, SkQ1 decreased ROS levels and apoptosis rate but increased mitochondrial membrane potential in the transfected cells. Conclusions Two novel heterozygous pathogenic variants of the SLC4A11 gene were identified in a family with CHED. The missense variant SLC4A11 (K263R) caused mitochondrial dysfunction and increased apoptosis in mutant transfected cells. In addition, SkQ1 presented a protective effect suggesting the anti-oxidant might be a novel therapeutic drug. Translational Relevance This study verified the pathogenicity of 2 novel variants in the SLC4A11 gene in a CHED family and found an anti-oxidant might be a new drug.
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Affiliation(s)
- Tianjiao Zhen
- Henan University People's Hospital, Henan Provincial People's Hospital, Zhengzhou, China
| | - Ya Li
- Henan Branch of National Clinical Research Center for Ocular Diseases, Henan Eye Institute/Henan Eye Hospital, People's Hospital of Zhengzhou University, Henan Provincial People's Hospital, Zhengzhou, China
| | - Qingge Guo
- Henan Branch of National Clinical Research Center for Ocular Diseases, Henan Eye Institute/Henan Eye Hospital, People's Hospital of Zhengzhou University, Henan Provincial People's Hospital, Zhengzhou, China
| | - Shun Yao
- Henan Branch of National Clinical Research Center for Ocular Diseases, Henan Eye Institute/Henan Eye Hospital, People's Hospital of Zhengzhou University, Henan Provincial People's Hospital, Zhengzhou, China
| | - Ya You
- Henan Branch of National Clinical Research Center for Ocular Diseases, Henan Eye Institute/Henan Eye Hospital, People's Hospital of Zhengzhou University, Henan Provincial People's Hospital, Zhengzhou, China
| | - Bo Lei
- Henan University People's Hospital, Henan Provincial People's Hospital, Zhengzhou, China
- Henan Branch of National Clinical Research Center for Ocular Diseases, Henan Eye Institute/Henan Eye Hospital, People's Hospital of Zhengzhou University, Henan Provincial People's Hospital, Zhengzhou, China
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Souzeau E, Siggs OM, Mullany S, Schmidt JM, Hassall MM, Dubowsky A, Chappell A, Breen J, Bae H, Nicholl J, Hadler J, Kearns LS, Staffieri SE, Hewitt AW, Mackey DA, Gupta A, Burdon KP, Klebe S, Craig JE, Mills RA. Diagnostic yield of candidate genes in an Australian corneal dystrophy cohort. Mol Genet Genomic Med 2022; 10:e2023. [PMID: 35985662 PMCID: PMC9544209 DOI: 10.1002/mgg3.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 07/18/2022] [Indexed: 11/09/2022] Open
Abstract
Corneal dystrophies describe a clinically and genetically heterogeneous group of inherited disorders. The International Classification of Corneal Dystrophies (IC3D) lists 22 types of corneal dystrophy, 17 of which have been demonstrated to result from pathogenic variants in 19 identified genes. In this study, we investigated the diagnostic yield of genetic testing in a well‐characterised cohort of 58 individuals from 44 families with different types of corneal dystrophy. Individuals diagnosed solely with Fuchs endothelial corneal dystrophy were excluded. Clinical details were obtained from the treating ophthalmologist. Participants and their family members were tested using a gene candidate and exome sequencing approach. We identified a likely molecular diagnosis in 70.5% families (31/44). The detection rate was significantly higher among probands with a family history of corneal dystrophy (15/16, 93.8%) than those without (16/28, 57.1%, p = .015), and among those who had undergone corneal graft surgery (9/9, 100.0%) compared to those who had not (22/35, 62.9%, p = .041). We identified eight novel variants in five genes and identified five families with syndromes associated with corneal dystrophies. Our findings highlight the genetic heterogeneity of corneal dystrophies and the clinical utility of genetic testing in reaching an accurate clinical diagnosis.
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Affiliation(s)
- Emmanuelle Souzeau
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - Owen M Siggs
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia.,Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Sean Mullany
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - Joshua M Schmidt
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - Mark M Hassall
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia
| | | | - Angela Chappell
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - James Breen
- South Australian Genomics Centre (SAGC), South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.,Robinson Research Institute, University of Adelaide, Adelaide, South Australia, Australia.,Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia
| | - Haae Bae
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia
| | | | | | - Lisa S Kearns
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - Sandra E Staffieri
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia.,Department of Ophthalmology, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Alex W Hewitt
- Menzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia
| | - David A Mackey
- Menzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia.,Centre for Ophthalmology and Visual Science, University of Western Australia, Lions Eye Institute, Perth, Western Australia, Australia
| | - Aanchal Gupta
- South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Australia, Australia.,Adelaide Eye & Laser Centre, Adelaide, South Australia, Australia
| | - Kathryn P Burdon
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia.,Centre for Ophthalmology and Visual Science, University of Western Australia, Lions Eye Institute, Perth, Western Australia, Australia
| | - Sonja Klebe
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - Jamie E Craig
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - Richard A Mills
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, South Australia, Australia
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Harboyan Syndrome: A Novel SLC4A11 Variant With Unique Genotype-Phenotype Correlation. Cornea 2022; 41:1053-1057. [PMID: 35439766 DOI: 10.1097/ico.0000000000003023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE The purpose of this study was to describe the genotypic and phenotypic characteristics of an infant with a SLC4A11 mutation associated with bilateral corneal edema, hearing loss, and hydronephrosis present since birth. METHODS This was a case report. Ophthalmic and systemic examination of the proband, histopathologic and ultrastructural characteristics of bilateral corneal discs, and molecular genetic evaluation by whole-exome sequencing are described. RESULTS A male infant was born with bilateral corneal opacities, sensorineural hearing loss, and hydronephrosis to healthy parents after an uneventful pregnancy. Penetrating keratoplasty of the left eye at age 10 months demonstrated minimal corneal edema with normal thickness Descemet membrane and cellular endothelium with intracytoplasmic vacuoles and degenerative changes in rare cells. Penetrating keratoplasty of the right eye 6 months later disclosed prominent corneal edema with a thickened posterior banded layer of Descemet membrane and severe endothelial atrophy. Whole-exome sequencing of the proband and parents' blood demonstrated a homozygous mutation in SLC4A11 gene (c.1735_1737delCTC,p.Leu579del). The combined clinical, histopathologic, and molecular genetic findings raised consideration of an unusual phenotype of Harboyan syndrome manifesting as congenital hereditary endothelial dystrophy with a prelingual rather than, as previously described, postlingual hearing loss. CONCLUSIONS We report a novel homozygous SLC4A11 variant with a previously undocumented phenotype of CHED in association with prelingual sensorineural hearing loss and hydronephrosis, thus broadening our understanding of the spectrum of genotypic and phenotypic findings of Harboyan syndrome.
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SLC4A11 mutations causative of congenital hereditary endothelial dystrophy (CHED) progressing to Harboyan syndrome in consanguineous Pakistani families. Mol Biol Rep 2021; 48:7467-7476. [PMID: 34637099 DOI: 10.1007/s11033-021-06765-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 08/17/2021] [Indexed: 10/20/2022]
Abstract
BACKGROUND Autosomal recessive corneal hereditary endothelial dystrophy (CHED) is a rare congenital disorder of cornea. Mutations in SLC4A11 gene are associated with CHED phenotype. CHED is also an early feature of Harboyan syndrome. The aim of the present study was to identify genetic mutations in the SLC4A11 gene in CHED cases belonging to inbred Pakistani families. Furthermore, all homozygous mutation carriers were investigated for hearing deficit. METHODS AND RESULTS This study included consanguineous CHED families presented at Al-Shifa Trust Eye Hospital, Rawalpindi, Pakistan from June 2018 to September 2018. DNA was extracted from blood samples. Direct sequencing of SLC4A11 gene was performed. All identified variants were evaluated by in silico programs i.e., SIFT, PolyPhen-2, and MutationTaster. Pathogenicity of the two identified splice site variants was analyzed by Human Splicing Finder and MaxEnt Scan. Screening of five CHED families revealed a total of three previously un reported (p.Arg128Gly, c.2241-2A > T and c.1898-2A > C in family CHED19, CHED22 and CHED26 respectively) and two already reported homozygous disease causing variants (p.Arg869Cys and p.Val824Met in family CHED24 and CHED25 respectively) as predicted by mutation taster. All of these variants segregated with disease phenotype and were not detected in controls. CONCLUSION Affected individuals of the five CHED families screened in this study had the disease due to SLC4A11 mutations and progressing to Harboyan syndrome. Identification of previously unreported mutations aid to heterogeneity of SLC4A11 and CHED pathogenesis as well as helped to provide genetic counseling to affected families.
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Tananuvat N, Tananuvat R, Chartapisak W, Mahanupab P, Hokierti C, Srikummool M, Kampuansai J, Intachai W, Olsen B, Ketudat Cairns JR, Kantaputra P. Harboyan syndrome: novel SLC4A11 mutation, clinical manifestations, and outcome of corneal transplantation. J Hum Genet 2020; 66:193-203. [PMID: 32884076 DOI: 10.1038/s10038-020-00834-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 07/20/2020] [Accepted: 08/27/2020] [Indexed: 11/10/2022]
Abstract
Harboyan syndrome or corneal dystrophy and progressive deafness (MIM #217400) is characterized by congenital hereditary endothelial dystrophy (CHED) and progressive, sensorineural hearing loss. Mutations in SLC4A11 are responsible for this rare genetic syndrome. Eight patients from seven unrelated families affected with Harboyan Syndrome with mean follow-up of 12.0 ± 0.9 years were thoroughly investigated for the ocular, hearing, and kidney function abnormalities and the outcome of penetrating keratoplasty (PK). Mutation analysis of SLC4A11 was performed. All patients presented with bilateral cloudy corneas since birth. Sensorineural hearing loss was detected in all patients. Seven patients (11 eyes) underwent PK with the median age at surgery of 10.1 years (7.1-22.9). The overall corneal graft survival rate after primary PK was 72.7% (8/11 eyes). The mean graft survival time was 94.6 months (95% CI 83.1-126.0). All patients had unremarkable kidney function. The c.2264G>A (p.Arg755Gln) mutation in SCL4A11 was detected in most patients (87.5%). All unrelated Karen tribe patients had p.Arg755Gln mutation, suggestive of founder effect. We found the allele frequency of this variant in the Karen population to be 0.01. The c.2263C>T (p.Arg755Trp) mutation was found in one patient with mild phenotype and the novel truncating protein mutation c.2127delG (p.Gly710fsx*25) in SCL4A11 was identified in two Thai sisters. Visual outcome and graft survival after PK were satisfactory. Our study shows that all studied patients with SLC4A11 mutations had CHED and sensorineural hearing loss, and SLC4A11 mutations were not related to the onset and severity of hearing loss or outcome of keratoplasty.
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Affiliation(s)
- Napaporn Tananuvat
- Department of Ophthalmology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Rak Tananuvat
- Department of Otolaryngology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Wattana Chartapisak
- Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Pongsak Mahanupab
- Department of Pathology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | | | - Metawee Srikummool
- Department of Biochemistry, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand
| | - Jatupol Kampuansai
- Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
| | - Worrachet Intachai
- Center of Excellence in Medical Genetics Research, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand
| | - Bjorn Olsen
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - James R Ketudat Cairns
- School of Chemistry, Institute of Science, and Center for Biomolecular Structure, Function and Application, Suranaree University of Technology, Nakhon Ratchasima, Thailand.,Laboratory of Biochemistry, Chulabhorn Research Institute, Bangkok, Thailand
| | - Piranit Kantaputra
- Division of Pediatric Dentistry, Department of Orthodontics and Pediatric Dentistry, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand.
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Romero PT, Donoso R, López P, Miranda A, Rodríguez L, Chrzanowsky D, Asenjo MS, Burgos G, Villegas P, Desir J, Moya G, Herrera LM. Clinical features and possible founder mutation of the 8bp duplication mutation in the SLC4A11 gene causing corneal dystrophy and perceptive deafness in three South American families. Ophthalmic Genet 2019; 40:91-98. [PMID: 30856043 DOI: 10.1080/13816810.2019.1571615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Corneal Dystrophy and Perceptive Deafness (CDPD) or Harboyan syndrome is an autosomal recessive rare disorder, characterized by congenital corneal opacities and progressive sensorineural hearing loss, which usually begins after the second decades of life. This study reports the ophthalmic, audiological and genetic features, in five CDPD affected patients from three Chilean families. MATERIALS AND METHODS Five individuals affected with CDPD from three unrelated Chilean families were clinically and genetically examined. To evaluate a putative founder mutation 7 SNPs were analyzed in the three families, an Argentinian patient (carrier of the same mutation previously reported) and 87 Chilean controls. RESULTS The ophthalmic symptoms in the five patients were bilateral and symmetric, starting before one year of age, and visual acuity varied from 0.1 to 0.3. In all cases, hearing loss began over 8 years old. The sequence of the 19 exons of SLC4A11 gene of all the affected patients exhibited homozygous eight nucleotide sequence duplication (c.2233_2240dup TATGACAC, p.(Ile748Metfs*5)) at the end of exon 16. All the affected patients of the three families were homozygous for a haplotype composed of five SNPs and covering 4,1 Mb. The same haplotype was present in one allele of the heterozygous Argentinean patient and has a frequency of 2.76% in Chilean population. CONCLUSIONS The five CDPD patients were homozygous for the same mutation in the SLC4A11 gene. Haplotype analysis of all the affected, including the case reported from Argentina was in accordance with a founder mutation.
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Affiliation(s)
- Pablo T Romero
- a Hospital Clínico Universidad de Chile José Joaquín Aguirre , Santiago , Chile
| | - Rodrigo Donoso
- b Servicio de Oftalmología , Hospital del Salvador , Santiago , Chile
| | - Pamela López
- c Programa de Genética Humana, ICBM, Facultad de Medicina , Universidad de Chile , Santiago , Chile
| | - Ana Miranda
- c Programa de Genética Humana, ICBM, Facultad de Medicina , Universidad de Chile , Santiago , Chile
| | - Leandro Rodríguez
- d Servicio de Otorrinolaringología , Hospital del Salvador , Santiago , Chile
| | - Dominique Chrzanowsky
- c Programa de Genética Humana, ICBM, Facultad de Medicina , Universidad de Chile , Santiago , Chile
| | - Maria S Asenjo
- c Programa de Genética Humana, ICBM, Facultad de Medicina , Universidad de Chile , Santiago , Chile
| | - Gonzalo Burgos
- c Programa de Genética Humana, ICBM, Facultad de Medicina , Universidad de Chile , Santiago , Chile
| | - Pablo Villegas
- e Servicio de Anatomía Patológica , Hospital del Salvador , Santiago , Chile
| | - Julie Desir
- f Department of Medical Genetics , Hôpital Erasme, ULB , Brussels , Belgium
| | | | - Luisa M Herrera
- c Programa de Genética Humana, ICBM, Facultad de Medicina , Universidad de Chile , Santiago , Chile
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SLC4A11 and the Pathophysiology of Congenital Hereditary Endothelial Dystrophy. BIOMED RESEARCH INTERNATIONAL 2015; 2015:475392. [PMID: 26451371 PMCID: PMC4588344 DOI: 10.1155/2015/475392] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 05/17/2015] [Indexed: 12/13/2022]
Abstract
Congenital hereditary endothelial dystrophy (CHED) is a rare autosomal recessive disorder of the corneal endothelium characterized by nonprogressive bilateral corneal edema and opacification present at birth. Here we review the current knowledge on the role of the SLC4A11 gene, protein, and its mutations in the pathophysiology and clinical presentation of CHED. Individuals with CHED have mutations in SLC4A11 which encodes a transmembrane protein in the SLC4 family of bicarbonate transporters. The expression of SLC4A11 in the corneal endothelium and inner ear patterns the deficits seen in CHED with corneal edema and hearing loss (Harboyan syndrome). slc4a11-null-mouse models recapitulate the CHED disease phenotype, thus establishing a functional role for SLC4A11 in CHED. However, the transport function of SLC4A11 remains unsettled. Some of the roles that have been attributed to SLC4A11 include H(+) and NH4 (+) permeation, electrogenic Na(+)-H(+) exchange, and water transport. Future studies of the consequences of SLC4A11 dysfunction as well as further understanding of corneal endothelial ion transport will help clarify the involvement of SLC4A11 in the pathophysiology of CHED.
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Liskova P, Dudakova L, Tesar V, Bednarova V, Kidorova J, Jirsova K, Davidson AE, Hardcastle AJ. Detailed assessment of renal function in a proband with Harboyan syndrome caused by a novel homozygous SLC4A11 nonsense mutation. Ophthalmic Res 2014; 53:30-5. [PMID: 25500497 DOI: 10.1159/000365109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 05/28/2014] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIMS To identify the underlying molecular genetic cause of disease in a patient with Harboyan syndrome and to perform a detailed assessment of her renal function. We also assessed the influence of the SLC4A11 mutation identified on the corneal endothelium in the heterozygous state. METHODS A 55-year-old female was examined ophthalmologically, audiologically and nephrologically including 24-hour urine collection. The coding region of SLC4A11 was directly sequenced. Specular microscopy was performed in the proband's 21-year-old daughter. RESULTS The proband had bilateral iridectomy at the age of 3 months because of an initial diagnosis of congenital glaucoma and since the age of 12 years she underwent several keratoplasties in each eye. Nephrological examination did not reveal any abnormalities. Moderate bilateral sensorineural hearing loss was confirmed by audiometry. A novel homozygous mutation predicted to lead to a premature stop codon at the protein level, c.2188C>T; p.(Arg730*), was identified in SLC4A11. No changes in corneal endothelial cell morphology or density were observed in the heterozygous daughter. CONCLUSION In contrast to the Slc4a11(-/-) mouse, no abnormalities in daily renal ion excretion or polyuria were observed in the Harboyan syndrome patient. The mutation identified does not affect corneal endothelial cell morphology or density in the heterozygous state.
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Affiliation(s)
- Petra Liskova
- Laboratory of the Biology and Pathology of the Eye, Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
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Siddiqui S, Zenteno JC, Rice A, Chacón-Camacho O, Naylor SG, Rivera-de la Parra D, Spokes DM, James N, Toomes C, Inglehearn CF, Ali M. Congenital hereditary endothelial dystrophy caused by SLC4A11 mutations progresses to Harboyan syndrome. Cornea 2014; 33:247-51. [PMID: 24351571 PMCID: PMC4195577 DOI: 10.1097/ico.0000000000000041] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Supplemental Digital Content is Available in the Text. Purpose: Homozygous mutations in SLC4A11 cause 2 rare recessive conditions: congenital hereditary endothelial dystrophy (CHED), affecting the cornea alone, and Harboyan syndrome consisting of corneal dystrophy and sensorineural hearing loss. In addition, adult-onset Fuchs endothelial corneal dystrophy (FECD) is associated with dominant mutations in SLC4A11. In this report, we investigate whether patients with CHED go on to develop hearing loss and whether their parents, who are carriers of an SLC4A11 mutation, show signs of having FECD. Methods: Patients with CHED were screened for mutations in the SLC4A11 gene and underwent audiometric testing. The patients and their parents underwent a clinical examination and specular microscopy. Results: Molecular analyses confirmed SLC4A11 mutations in 4 affected individuals from 3 families. All the patients were found to have varying degrees of sensorineural hearing loss at a higher frequency range. Guttate lesions were seen in 2 of the 4 parents who were available for examination. Conclusions: Our observations suggest that CHED caused by homozygous SLC4A11 mutations progresses to Harboyan syndrome, but the severity of this may vary considerably. Patients with CHED should therefore be monitored for progressive hearing loss. We could not determine conclusively whether the parents of the patients with CHED were at increased risk of developing late-onset FECD.
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Affiliation(s)
- Salina Siddiqui
- *Section of Ophthalmology and Neuroscience, Leeds Institute of Biomedical and Clinical Sciences, University of Leeds, Leeds, United Kingdom; †Department of Ophthalmology, St James's University Hospital, Leeds, United Kingdom; ‡Department of Biochemistry, Faculty of Medicine, National Autonomous University of Mexico (UNAM), Mexico City, Mexico; §Department of Genetics, Institute of Ophthalmology "Conde de Valenciana," Mexico City, Mexico; and ¶Department of Ophthalmology, Bradford Royal Infirmary, Bradford, United Kingdom
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Biosynthetic and functional defects in newly identified SLC4A11 mutants and absence of COL8A2 mutations in Fuchs endothelial corneal dystrophy. J Hum Genet 2014; 59:444-53. [PMID: 25007886 DOI: 10.1038/jhg.2014.55] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 05/26/2014] [Accepted: 06/12/2014] [Indexed: 12/31/2022]
Abstract
Late-onset Fuchs endothelial corneal dystrophy (FECD) shows genetic heterogeneity. Identification of SLC4A11 as a candidate gene for congenital hereditary endothelial dystrophy with similar corneal endothelial defects as FECD and reduced mRNA expression of SLC4A11 in the endothelium of FECD cases suggested that this gene may also be involved in pathogenesis of FECD. Mutations in SLC4A11 give rise to SLC4A11 protein marked by retention in the endoplasmic reticulum as a result of mis-folding. We screened 45 sporadic late-onset, 4 early-onset FECD patients and an early-onset autosomal dominant FECD family. We identified three previously unreported missense mutations: c.719G>C (p.W240S), c.1519G>A (p.V507I) and c.1304C>T (p.T434I) in unrelated individuals. These SLC4A11 mutants, expressed in HEK293 cells, had defects in either their cell surface expression or functional activity (rate of osmotically driven water flux). SLC4A11 mutations contribute to 11% (5/45) of sporadic late-onset FECD in the cohort studied. COL8A2, which causes some cases of early-onset FECD, was also screened in this cohort. No mutations were identified in COL8A2, in neither the late-onset cohort nor the early-onset family, suggesting genetic heterogeneity in this FECD family.
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Romero MF, Chen AP, Parker MD, Boron WF. The SLC4 family of bicarbonate (HCO₃⁻) transporters. Mol Aspects Med 2013; 34:159-82. [PMID: 23506864 DOI: 10.1016/j.mam.2012.10.008] [Citation(s) in RCA: 236] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 08/28/2012] [Indexed: 01/13/2023]
Abstract
The SLC4 family consists of 10 genes (SLC4A1-5; SLC4A7-11). All encode integral membrane proteins with very similar hydropathy plots-consistent with 10-14 transmembrane segments. Nine SLC4 members encode proteins that transport HCO3(-) (or a related species, such as CO3(2-)) across the plasma membrane. Functionally, eight of these proteins fall into two major groups: three Cl-HCO3 exchangers (AE1-3) and five Na(+)-coupled HCO3(-) transporters (NBCe1, NBCe2, NBCn1, NBCn2, NDCBE). Two of the Na(+)-coupled transporters (NBCe1, NBCe2) are electrogenic; the other three Na(+)-coupled HCO3(-) transporters and all three AEs are electroneutral. In addition, two other SLC4 members (AE4, SLC4A9 and BTR1, SLC4A11) do not yet have a firmly established function. Most, though not all, SLC4 members are functionally inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS). SLC4 proteins play important roles many modes of acid-base homeostasis: the carriage of CO2 by erythrocytes, the transport of H(+) or HCO3(-) by several epithelia, as well as the regulation of cell volume and intracellular pH.
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Affiliation(s)
- Michael F Romero
- Physiology & Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
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12
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Parker MD, Boron WF. The divergence, actions, roles, and relatives of sodium-coupled bicarbonate transporters. Physiol Rev 2013; 93:803-959. [PMID: 23589833 PMCID: PMC3768104 DOI: 10.1152/physrev.00023.2012] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mammalian Slc4 (Solute carrier 4) family of transporters is a functionally diverse group of 10 multi-spanning membrane proteins that includes three Cl-HCO3 exchangers (AE1-3), five Na(+)-coupled HCO3(-) transporters (NCBTs), and two other unusual members (AE4, BTR1). In this review, we mainly focus on the five mammalian NCBTs-NBCe1, NBCe2, NBCn1, NDCBE, and NBCn2. Each plays a specialized role in maintaining intracellular pH and, by contributing to the movement of HCO3(-) across epithelia, in maintaining whole-body pH and otherwise contributing to epithelial transport. Disruptions involving NCBT genes are linked to blindness, deafness, proximal renal tubular acidosis, mental retardation, and epilepsy. We also review AE1-3, AE4, and BTR1, addressing their relevance to the study of NCBTs. This review draws together recent advances in our understanding of the phylogenetic origins and physiological relevance of NCBTs and their progenitors. Underlying these advances is progress in such diverse disciplines as physiology, molecular biology, genetics, immunocytochemistry, proteomics, and structural biology. This review highlights the key similarities and differences between individual NCBTs and the genes that encode them and also clarifies the sometimes confusing NCBT nomenclature.
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Affiliation(s)
- Mark D Parker
- Dept. of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106-4970, USA.
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