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Thomas L, Cuisset L, Papon JF, Tamalet A, Pin I, Abou Taam R, Faucon C, Montantin G, Tissier S, Duquesnoy P, Dastot-Le Moal F, Copin B, Carion N, Louis B, Chantot-Bastaraud S, Siffroi JP, Mitri R, Coste A, Escudier E, Thouvenin G, Amselem S, Legendre M. Skewed X-chromosome inactivation drives the proportion of DNAAF6-defective airway motile cilia and variable expressivity in primary ciliary dyskinesia. J Med Genet 2024; 61:595-604. [PMID: 38408845 DOI: 10.1136/jmg-2023-109700] [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: 10/19/2023] [Accepted: 02/10/2024] [Indexed: 02/28/2024]
Abstract
BACKGROUND Primary ciliary dyskinesia (PCD) is a rare airway disorder caused by defective motile cilia. Only male patients have been reported with pathogenic mutations in X-linked DNAAF6, which result in the absence of ciliary dynein arms, whereas their heterozygous mothers are supposedly healthy. Our objective was to assess the possible clinical and ciliary consequences of X-chromosome inactivation (XCI) in these mothers. METHODS XCI patterns of six mothers of male patients with DNAAF6-related PCD were determined by DNA-methylation studies and compared with their clinical phenotype (6/6 mothers), as well as their ciliary phenotype (4/6 mothers), as assessed by immunofluorescence and high-speed videomicroscopy analyses. The mutated X chromosome was tracked to assess the percentage of cells with a normal inactivated DNAAF6 allele. RESULTS The mothers' phenotypes ranged from absence of symptoms to mild/moderate or severe airway phenotypes, closely reflecting their XCI pattern. Analyses of the symptomatic mothers' airway ciliated cells revealed the coexistence of normal cells and cells with immotile cilia lacking dynein arms, whose ratio closely mirrored their XCI pattern. CONCLUSION This study highlights the importance of searching for heterozygous pathogenic DNAAF6 mutations in all female relatives of male PCD patients with a DNAAF6 defect, as well as in females consulting for mild chronic respiratory symptoms. Our results also demonstrate that about one-third-ranging from 20% to 50%-normal ciliated airway cells sufficed to avoid severe PCD, a result paving the way for gene therapy.
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Affiliation(s)
- Lucie Thomas
- Childhood Genetic Diseases, Sorbonne Université, Inserm, Hôpital Armand-Trousseau, Paris, F-75012, France
| | - Laurence Cuisset
- Service de Médecine Génomique, Assistance Publique Hôpitaux de Paris (AP-HP), Université de Paris, Hôpital Cochin, Paris, F-75014, France
| | - Jean-Francois Papon
- Service d'Oto-Rhino-Laryngologie et de Chirurgie Cervico-Faciale, AP-HP, Hôpital Bicêtre, Le Kremlin-Bicêtre, F-94270, France
- Institut Mondor de Recherche Biomédicale, Université Paris-Est Créteil, Inserm U955, CNRS ERL7240, Hôpital Henri-Mondor, Créteil, F-94010, France
| | - Aline Tamalet
- Département de Pneumologie Pédiatrique, Centre National de Référence des Maladies Respiratoires Rares RespiRare, AP-HP, Sorbonne Université, Hôpital Armand-Trousseau Hospital, Paris, F-75012, France
| | - Isabelle Pin
- Pédiatrie, CHU Grenoble Alpes, Grenoble, F-38500, France
| | - Rola Abou Taam
- Service de Pneumologie et Allergologie Pédiatriques, AP-HP, Hôpital Necker-Enfants Malades, Paris, F-75015, France
| | - Catherine Faucon
- Service d'Anatomopathologie, Laboratoire de Microscopie Electronique, Centre Hospitalier Intercommunal de Créteil, Créteil, F-94000, France
| | - Guy Montantin
- Génétique moléculaire, AP-HP, Hôpital Armand-Trousseau, Paris, F-75012, Paris
| | - Sylvie Tissier
- Génétique moléculaire, AP-HP, Hôpital Armand-Trousseau, Paris, F-75012, Paris
| | - Philippe Duquesnoy
- Childhood Genetic Diseases, Sorbonne Université, Inserm, Hôpital Armand-Trousseau, Paris, F-75012, France
| | | | - Bruno Copin
- Childhood Genetic Diseases, Sorbonne Université, Inserm, Hôpital Armand-Trousseau, Paris, F-75012, France
- Génétique moléculaire, AP-HP, Hôpital Armand-Trousseau, Paris, F-75012, Paris
| | - Nathalie Carion
- Service de Médecine Génomique, Assistance Publique Hôpitaux de Paris (AP-HP), Université de Paris, Hôpital Cochin, Paris, F-75014, France
| | - Bruno Louis
- Institut Mondor de Recherche Biomédicale, Université Paris-Est Créteil, Inserm U955, CNRS ERL7240, Hôpital Henri-Mondor, Créteil, F-94010, France
| | - Sandra Chantot-Bastaraud
- Childhood Genetic Diseases, Sorbonne Université, Inserm, Hôpital Armand-Trousseau, Paris, F-75012, France
- Génétique chromosomique, AP-HP, Hôpital Trousseau, Paris, F-75012, France
| | - Jean-Pierre Siffroi
- Childhood Genetic Diseases, Sorbonne Université, Inserm, Hôpital Armand-Trousseau, Paris, F-75012, France
- Génétique chromosomique, AP-HP, Hôpital Trousseau, Paris, F-75012, France
| | - Rana Mitri
- Service d'Anatomopathologie, Laboratoire de Microscopie Electronique, Centre Hospitalier Intercommunal de Créteil, Créteil, F-94000, France
| | - André Coste
- Institut Mondor de Recherche Biomédicale, Université Paris-Est Créteil, Inserm U955, CNRS ERL7240, Hôpital Henri-Mondor, Créteil, F-94010, France
- Service d'ORL et de Chirurgie Cervico-Faciale, AP-HP, Hôpital Henri-Mondor, Centre Hospitalier Intercommunal de Créteil, Créteil, F-94000, France
| | - Estelle Escudier
- Childhood Genetic Diseases, Sorbonne Université, Inserm, Hôpital Armand-Trousseau, Paris, F-75012, France
- Génétique moléculaire, AP-HP, Hôpital Armand-Trousseau, Paris, F-75012, Paris
| | - Guillaume Thouvenin
- Département de Pneumologie Pédiatrique, Centre National de Référence des Maladies Respiratoires Rares RespiRare, AP-HP, Sorbonne Université, Hôpital Armand-Trousseau Hospital, Paris, F-75012, France
| | - Serge Amselem
- Childhood Genetic Diseases, Sorbonne Université, Inserm, Hôpital Armand-Trousseau, Paris, F-75012, France
- Génétique moléculaire, AP-HP, Hôpital Armand-Trousseau, Paris, F-75012, Paris
| | - Marie Legendre
- Childhood Genetic Diseases, Sorbonne Université, Inserm, Hôpital Armand-Trousseau, Paris, F-75012, France
- Génétique moléculaire, AP-HP, Hôpital Armand-Trousseau, Paris, F-75012, Paris
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Chen X, Yun L, Long Y, Sun Y, Chen T. First report on female monozygotic twins discordant for congenital nephrogenic diabetes insipidus. Am J Med Genet A 2024; 194:e63407. [PMID: 37909842 DOI: 10.1002/ajmg.a.63407] [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: 07/11/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 11/03/2023]
Abstract
Ninety percent of congenital nephrogenic diabetes insipidus (NDI) are X-linked inherited and are caused by mutations in the vasopressin type 2 receptor gene (AVPR2). Most affected individuals are males. Only sporadic female cases have been reported. Here, we first reported a female monozygotic twin with discordant phenotypes for NDI carrying a missense variant c.845T>C (p.Leu282Pro) in exon 4 of AVPR2. Intracellular cAMP concentrations in COS7 cells transfected with AVPR2-L282P were significantly decreased by about 60% compared with those in wild-type AVPR2 plasmid transfected cells, suggesting this variation was pathogenic. The X-inactivation pattern was investigated in peripheral leukocytes and urine sediments in both the unaffected and affected pair. Results showed that the affected pair had a skewed X chromosome inactivation (XCI) pattern in urine sediments and a random XCI pattern in leukocytes, while the unaffected pair showed a random XCI pattern both in leukocytes and urine sediments. This was the first report of monozygotic twins who developed different phenotypes of NDI. Our study suggested that the development of NDI symptoms is more closely associated with the XCI pattern in urine sediments compared with the XCI pattern in peripheral leukocytes. Analysis of XCI in peripheral leukocytes may not be enough to explore possible mechanisms.
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Affiliation(s)
- Xiang Chen
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, Chengdu, Sichuan, China
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, Chengdu, Sichuan, China
| | - Libing Yun
- Institute of Forensic Medicine, West China School of Basic Science and Forensic Medicine, Sichuan University, Chengdu, Sichuan, China
| | - Yang Long
- Experimental Medicine Center, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China
| | - Yuxia Sun
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, Chengdu, Sichuan, China
| | - Tao Chen
- Department of Endocrinology and Metabolism, West China Hospital of Sichuan University, Chengdu, Sichuan, China
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Hureaux M, Vargas-Poussou R. Genetic basis of nephrogenic diabetes insipidus. Mol Cell Endocrinol 2023; 560:111825. [PMID: 36460218 DOI: 10.1016/j.mce.2022.111825] [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: 05/23/2022] [Revised: 10/26/2022] [Accepted: 10/28/2022] [Indexed: 12/02/2022]
Abstract
Nephrogenic diabetes insipidus is defined as an inability to concentrate urine due to a complete or partial alteration of the renal tubular response to arginine vasopressin hormone, resulting in excessive diluted urine excretion. Hereditary forms are caused by molecular defects in the genes encoding either of the two main renal effectors of the arginine vasopressin pathway: the AVPR2 gene, which encodes for the type 2 vasopressin receptor, or the AQP2 gene, which encodes for the water channel aquaporin-2. About 90% of cases of nephrogenic diabetes insipidus result from loss-of-function variants in the AVPR2 gene, which are inherited in a X-linked recessive manner. The remaining 10% of cases result from loss-of-function variants in the AQP2 gene, which can be inherited in either a recessive or a dominant manner. The main symptoms of the disease are polyuria, chronic dehydration and hypernatremia. These symptoms usually occur in the first year of life, although some patients present later. Diagnosis is based on abnormal response in urinary osmolality after water restriction and/or administration of exogenous vasopressin. Treatment involves ensuring adequate water intake on demand, possibly combined with thiazide diuretics, non-steroidal anti-inflammatory drugs, and a low-salt and protein diet. In this review, we provide an update on current understanding of the molecular basis of inherited nephrogenic insipidus diabetes.
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Affiliation(s)
- Marguerite Hureaux
- Assistance Publique Hôpitaux de Paris, Hôpital Européen Georges-Pompidou, Department of Genetics, France and University of Paris Cité, Paris, France; Centre de Référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte (MARHEA), Paris, France
| | - Rosa Vargas-Poussou
- Assistance Publique Hôpitaux de Paris, Hôpital Européen Georges-Pompidou, Department of Genetics, France and University of Paris Cité, Paris, France; Centre de Référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte (MARHEA), Paris, France.
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A Novel Missense Mutation of Arginine Vasopressin Receptor 2 in a Chinese Family with Congenital Nephrogenic Diabetes Insipidus: X-Chromosome Inactivation in Female CNDI Patients with Heterozygote 814A>G Mutation. BIOMED RESEARCH INTERNATIONAL 2022; 2022:7073158. [PMID: 35865667 PMCID: PMC9296320 DOI: 10.1155/2022/7073158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 04/10/2022] [Accepted: 06/02/2022] [Indexed: 11/27/2022]
Abstract
Background To identify novel clinical phenotypic signatures of congenital nephrogenic diabetes insipidus (CNDI). Methods A Chinese family with CNDI was recruited for participation in this study. The proband and one of his uncles suffered from polydipsia and polyuria since infancy. The results of clinical testing indicated the diagnosis of CNDI. 10 family members had similar symptoms but did not seek medical advice. Genetic testing of mutations in the coding region of the aquaporin 2 (AQP2) gene and the arginine vasopressin receptor 2 (AVPR2) gene were carried out in 11 family members. Somatic DNA from 5 female family members was used to test for methylation of polymorphic CAG repeats in the human androgen receptor (AR) gene, as an index for X-chromosome inactivation pattern (XCIP). Results AQP2 gene mutations were not found in any family members, but a novel missense mutation (814th base A>G) in exon 2 of the AVPR2 gene was identified in 10 individuals. This mutation leads to a Met 272 Val (GAT-GGT) amino acid substitution. Skewed X-chromosome inactivation patterns of the normal X allele were observed in 4 females with the AVPR2 gene mutation and symptoms of diabetes insipidus, but not in an asymptomatic female with the AVPR2 gene mutation. Conclusions Met 272 Val mutation of the AVPR2 gene was identified as a novel genetic risk factor for CDNI. The clinical NDI phenotype of female carriers with heterozygous AVPR2 mutation may be caused by X-chromosome inactivation induced by dominant methylation of the normal allele of AVPR2 gene.
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Makita N, Manaka K, Sato J, Iiri T. V2 vasopressin receptor mutations. VITAMINS AND HORMONES 2019; 113:79-99. [PMID: 32138955 DOI: 10.1016/bs.vh.2019.08.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
V2 vasopressin receptor (V2R) is a member of the G protein-coupled receptor (GPCR) family in which many disease-causing mutations have been identified and thus generated much interest. Loss-of-function V2R mutations cause nephrogenic diabetes insipidus (NDI) whereas gain-of-function mutations cause nephrogenic syndrome of inappropriate antidiuresis (NSIAD). The mechanisms underlying a V2R loss-of-function can be theoretically classified as either protein expression, localization (ER retention) or functional disorders. Functional analyses have revealed however that these mechanisms are likely to be complex. Strikingly, V2R mutations at the same site can result in opposite phenotypes, e.g., R137H and R137L/C cause NDI and NSIAD, respectively. These findings support the notion that the constitutive activation of GPCRs might be often associated with their instability and denaturation. Thus, functional analysis of disease-causing V2R mutations may not only reveal potential new treatment strategies using pharmacochaperones for NDI and inverse agonists for NSIAD, but also provide a greater understanding of the physiological functions of GPCRs and highlight the new paradigms, i.e., biased agonism and protean agonism.
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Affiliation(s)
- Noriko Makita
- Department of Endocrinology and Nephrology, The University of Tokyo, Tokyo, Japan.
| | - Katsunori Manaka
- Department of Endocrinology and Nephrology, The University of Tokyo, Tokyo, Japan
| | - Junichiro Sato
- Department of Endocrinology and Nephrology, The University of Tokyo, Tokyo, Japan
| | - Taroh Iiri
- Department of Endocrinology and Nephrology, The University of Tokyo, Tokyo, Japan; Department of Pharmacology, St. Marianna University School of Medicine, Kawasaki, Japan.
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Four Japanese Patients with Congenital Nephrogenic Diabetes Insipidus due to the AVPR2 Mutations. Case Rep Pediatr 2018; 2018:6561952. [PMID: 30073107 PMCID: PMC6057286 DOI: 10.1155/2018/6561952] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 03/23/2018] [Accepted: 04/16/2018] [Indexed: 01/04/2023] Open
Abstract
Almost 90% of nephrogenic diabetes insipidus (NDI) is caused by mutations in the arginine vasopressin receptor 2 gene (AVPR2) on the X chromosome. Herein, we reported clinical and biochemical parameters in four cases of three unrelated Japanese families and analyzed the status of the AVPR2. Two of the four patients had poor weight gain. However, in the male and female sibling cases, neither had poor weight gain while toddlers, but in the male sibling, episodes of recurrent fever, polyuria, and polydipsia led to the diagnosis of NDI at 4 years of age. Analysis of AVPR2 identified two nonsense mutations (c.299_300insA; p.K100KfsX91 and c.296G > A; p.W99X) and one missense mutation (c.316C > T; p.R106C). These mutations were previously reported. The patient with c.316C > T; p.R106C had milder symptoms consistent with previous reports. Of the familial cases, the sister was diagnosed as having NDI, but a skewed X-inactivation pattern in her peripheral blood lymphocytes was not identified. In conclusion, our study expands the spectrum of phenotypes and characterized mutations in AVPR2 in NDI.
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Yoshida S, Nakanishi C, Okada H, Mori M, Yokawa J, Yoshimuta T, Ohta K, Konno T, Fujino N, Kawashiri MA, Yachie A, Yamagishi M, Hayashi K. Characteristics of induced pluripotent stem cells from clinically divergent female monozygotic twins with Danon disease. J Mol Cell Cardiol 2018; 114:234-242. [DOI: 10.1016/j.yjmcc.2017.11.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 11/04/2017] [Accepted: 11/22/2017] [Indexed: 12/20/2022]
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Milano S, Carmosino M, Gerbino A, Svelto M, Procino G. Hereditary Nephrogenic Diabetes Insipidus: Pathophysiology and Possible Treatment. An Update. Int J Mol Sci 2017; 18:ijms18112385. [PMID: 29125546 PMCID: PMC5713354 DOI: 10.3390/ijms18112385] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 11/03/2017] [Accepted: 11/07/2017] [Indexed: 12/17/2022] Open
Abstract
Under physiological conditions, excessive loss of water through the urine is prevented by the release of the antidiuretic hormone arginine-vasopressin (AVP) from the posterior pituitary. In the kidney, AVP elicits a number of cellular responses, which converge on increasing the osmotic reabsorption of water in the collecting duct. One of the key events triggered by the binding of AVP to its type-2 receptor (AVPR2) is the exocytosis of the water channel aquaporin 2 (AQP2) at the apical membrane the principal cells of the collecting duct. Mutations of either AVPR2 or AQP2 result in a genetic disease known as nephrogenic diabetes insipidus, which is characterized by the lack of responsiveness of the collecting duct to the antidiuretic action of AVP. The affected subject, being incapable of concentrating the urine, presents marked polyuria and compensatory polydipsia and is constantly at risk of severe dehydration. The molecular bases of the disease are fully uncovered, as well as the genetic or clinical tests for a prompt diagnosis of the disease in newborns. A real cure for nephrogenic diabetes insipidus (NDI) is still missing, and the main symptoms of the disease are handled with s continuous supply of water, a restrictive diet, and nonspecific drugs. Unfortunately, the current therapeutic options are limited and only partially beneficial. Further investigation in vitro or using the available animal models of the disease, combined with clinical trials, will eventually lead to the identification of one or more targeted strategies that will improve or replace the current conventional therapy and grant NDI patients a better quality of life. Here we provide an updated overview of the genetic defects causing NDI, the most recent strategies under investigation for rescuing the activity of mutated AVPR2 or AQP2, or for bypassing defective AVPR2 signaling and restoring AQP2 plasma membrane expression.
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Affiliation(s)
- Serena Milano
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70126 Bari, Italy.
| | - Monica Carmosino
- Department of Sciences, University of Basilicata, 85100 Potenza, Italy.
| | - Andrea Gerbino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70126 Bari, Italy.
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70126 Bari, Italy.
| | - Giuseppe Procino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70126 Bari, Italy.
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Abstract
Diabetes insipidus is a disease characterized by polyuria and polydipsia due to inadequate release of arginine vasopressin from the posterior pituitary gland (neurohypophyseal diabetes insipidus) or due to arginine vasopressin insensitivity by the renal distal tubule, leading to a deficiency in tubular water reabsorption (nephrogenic diabetes insipidus). This article reviews the genetics of diabetes insipidus in the context of its diagnosis, clinical presentation, and therapy.
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Affiliation(s)
- Marie Helene Schernthaner-Reiter
- Clinical Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria; Section on Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 31 Center Drive, Bethesda, MD 20892, USA.
| | - Constantine A Stratakis
- Section on Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 31 Center Drive, Bethesda, MD 20892, USA
| | - Anton Luger
- Clinical Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria
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Viggiano E, Ergoli M, Picillo E, Politano L. Determining the role of skewed X-chromosome inactivation in developing muscle symptoms in carriers of Duchenne muscular dystrophy. Hum Genet 2016; 135:685-98. [PMID: 27098336 DOI: 10.1007/s00439-016-1666-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 03/29/2016] [Indexed: 11/24/2022]
Abstract
Duchenne and Becker dystrophinopathies (DMD and BMD) are X-linked recessive disorders caused by mutations in the dystrophin gene that lead to absent or reduced expression of dystrophin in both skeletal and heart muscles. DMD/BMD female carriers are usually asymptomatic, although about 8 % may exhibit muscle or cardiac symptoms. Several mechanisms leading to a reduced dystrophin have been hypothesized to explain the clinical manifestations and, in particular, the role of the skewed XCI is questioned. In this review, the mechanism of XCI and its involvement in the phenotype of BMD/DMD carriers with both a normal karyotype or with X;autosome translocations with breakpoints at Xp21 (locus of the DMD gene) will be analyzed. We have previously observed that DMD carriers with moderate/severe muscle involvement, exhibit a moderate or extremely skewed XCI, in particular if presenting with an early onset of symptoms, while DMD carriers with mild muscle involvement present a random XCI. Moreover, we found that among 87.1 % of the carriers with X;autosome translocations involving the locus Xp21 who developed signs and symptoms of dystrophinopathy such as proximal muscle weakness, difficulty to run, jump and climb stairs, 95.2 % had a skewed XCI pattern in lymphocytes. These data support the hypothesis that skewed XCI is involved in the onset of phenotype in DMD carriers, the X chromosome carrying the normal DMD gene being preferentially inactivated and leading to a moderate-severe muscle involvement.
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Affiliation(s)
- Emanuela Viggiano
- Cardiomyology and Medical Genetics, Department of Experimental Medicine, I Policlinico, Second University of Naples, Piazza Miraglia, 80138, Naples, Italy
| | - Manuela Ergoli
- Cardiomyology and Medical Genetics, Department of Experimental Medicine, I Policlinico, Second University of Naples, Piazza Miraglia, 80138, Naples, Italy
| | - Esther Picillo
- Cardiomyology and Medical Genetics, Department of Experimental Medicine, I Policlinico, Second University of Naples, Piazza Miraglia, 80138, Naples, Italy
| | - Luisa Politano
- Cardiomyology and Medical Genetics, Department of Experimental Medicine, I Policlinico, Second University of Naples, Piazza Miraglia, 80138, Naples, Italy.
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Giri D, Hart R, Jones C, Ellis I, Ramakrishnan R. An unusual case of hereditary nephrogenic diabetes insipidus (HNDI) affecting mother and daughter. J Pediatr Endocrinol Metab 2016; 29:93-6. [PMID: 26244674 DOI: 10.1515/jpem-2015-0174] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 05/04/2015] [Indexed: 11/15/2022]
Abstract
Hereditary nephrogenic diabetes iInsipidus (HNDI) is an uncommon disorder due to a resistance to anti-diuretic hormone leading to a reduced urinary concentrating ability. The X-linked form is fully expressed in hemizygous male patients, but diabetes insipidus may also present in heterozygous females where it must be distinguished from autosomal and other secondary causes. We report a mother and daughter in the same family with HNDI due to a heterozygous deletion in exon 1 of the AVPR2 gene, not previously described in the literature. A 5-year-old girl was referred for investigation of polyuria and polydipsia. The patient had a water deprivation test elsewhere at the age of 3 that was inconclusive. A degree of water restriction was imposed leading to headaches. The thyroid, cortisol, renal, and calcium profiles were normal. Her mother showed similar symptoms that had not been previously investigated. AQP2 (Aquaporin) and initial AVPR2 gene sequencing had not identified a mutation, but subsequent quantitative polymerase chain reaction analysis revealed a heterozygous large exon 1 deletion of the AVPR2 gene. The same deletion was also found in the child's mother. The patient's symptoms have significantly improved on appropriate treatment. Further analysis revealed skewed X inactivation in mother and daughter.
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García Castaño A, Pérez de Nanclares G, Madariaga L, Aguirre M, Chocron S, Madrid A, Lafita Tejedor FJ, Gil Campos M, Sánchez Del Pozo J, Ruiz Cano R, Espino M, Gomez Vida JM, Santos F, García Nieto VM, Loza R, Rodríguez LM, Hidalgo Barquero E, Printza N, Camacho JA, Castaño L, Ariceta G. Novel mutations associated with nephrogenic diabetes insipidus. A clinical-genetic study. Eur J Pediatr 2015; 174:1373-85. [PMID: 25902753 DOI: 10.1007/s00431-015-2534-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 03/18/2015] [Accepted: 03/24/2015] [Indexed: 12/22/2022]
Abstract
UNLABELLED Molecular diagnosis is a useful diagnostic tool in primary nephrogenic diabetes insipidus (NDI), an inherited disease characterized by renal inability to concentrate urine. The AVPR2 and AQP2 genes were screened for mutations in a cohort of 25 patients with clinical diagnosis of NDI. Patients presented with dehydration, polyuria-polydipsia, failure to thrive (mean ± SD; Z-height -1.9 ± 2.1 and Z-weight -2.4 ± 1.7), severe hypernatremia (mean ± SD; Na 150 ± 10 mEq/L), increased plasma osmolality (mean ± SD; 311 ± 18 mOsm/Kg), but normal glomerular filtration rate. Genetic diagnosis revealed that 24 male patients were hemizygous for 17 different putative disease-causing mutations in the AVPR2 gene (each one in a different family). Of those, nine had not been previously reported, and eight were recurrent. Moreover, we found those same AVPR2 changes in 12 relatives who were heterozygous carriers. Further, in one female patient, AVPR2 gene study turned out to be negative and she was found to be homozygous for the novel AQP2 p.Ala86Val alteration. CONCLUSION Genetic analysis presumably confirmed the diagnosis of nephrogenic diabetes insipidus in every patient of the studied cohort. We emphasize that we detected a high presence (50 %) of heterozygous females with clinical NDI symptoms. WHAT IS KNOWN • In most cases (90 %), inherited nephrogenic diabetes insipidus (NDI) is an X-linked disease, caused by mutations in the AVPR2 gene. • In rare occasions (10 %), it is caused by mutations in the AQP2 gene. What is new: • In this study, we report 10 novel mutations associated with NDI. • We have detected a high presence (50 %) of heterozygous carriers with clinical NDI symptoms.
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Affiliation(s)
| | | | - Leire Madariaga
- Paediatric Nephrology, Cruces University Hospital, Bizkaia, Spain.
- Department of Paediatrics, School of Medicine and Odontology, University of Basque Country UPV/EHU, Bizkaia, Spain.
| | - Mireia Aguirre
- Paediatric Nephrology, Cruces University Hospital, Bizkaia, Spain.
| | - Sara Chocron
- Paediatric Nephrology, University Hospital Vall d'Hebron, Barcelona, Spain.
| | - Alvaro Madrid
- Paediatric Nephrology, University Hospital Vall d'Hebron, Barcelona, Spain.
| | | | - Mercedes Gil Campos
- Paediatric Research and Metabolism Unit, Reina Sofia University Hospital, Córdoba, Spain.
| | - Jaime Sánchez Del Pozo
- Department of Paediatrics, Division of Endocrinology, 12 de Octubre Hospital, Madrid, Spain.
| | - Rafael Ruiz Cano
- Paediatric Endocrinology, Albacete General University Hospital, Albacete, Spain.
| | - Mar Espino
- Paediatric Nephrology, 12 de Octubre Hospital, Madrid, Spain.
| | | | - Fernando Santos
- Paediatric Nephrology, Asturias Central University Hospital, Oviedo, Asturias, Spain.
| | | | - Reyner Loza
- Nephrology Unit, Cayetano Heredia University, Cayetano Heredia Hospital, Lima, Peru.
| | | | | | - Nikoleta Printza
- Department of Paediatrics, Aristotle University of Thessaloniki, Hippokratio Hospital, Thessaloniki, Greece.
| | | | - Luis Castaño
- BioCruces Institute, Ciberer, Cruces University Hospital, Bizkaia, Spain.
- Department of Paediatrics, School of Medicine and Odontology, University of Basque Country UPV/EHU, Bizkaia, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain, .
| | - Gema Ariceta
- Paediatric Nephrology, University Hospital Vall d'Hebron, Barcelona, Spain.
- Autonomous University of Barcelona, Barcelona, Spain.
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Bockenhauer D, Bichet DG. Pathophysiology, diagnosis and management of nephrogenic diabetes insipidus. Nat Rev Nephrol 2015; 11:576-88. [PMID: 26077742 DOI: 10.1038/nrneph.2015.89] [Citation(s) in RCA: 162] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Healthy kidneys maintain fluid and electrolyte homoeostasis by adjusting urine volume and composition according to physiological needs. The final urine composition is determined in the last tubular segment: the collecting duct. Water permeability in the collecting duct is regulated by arginine vasopressin (AVP). Secretion of AVP from the neurohypophysis is regulated by a complex signalling network that involves osmosensors, barosensors and volume sensors. AVP facilitates aquaporin (AQP)-mediated water reabsorption via activation of the vasopressin V2 receptor (AVPR2) in the collecting duct, thus enabling concentration of urine. In nephrogenic diabetes insipidus (NDI), inability of the kidneys to respond to AVP results in functional AQP deficiency. Consequently, affected patients have constant diuresis, resulting in large volumes of dilute urine. Primary forms of NDI result from mutations in the genes that encode the key proteins AVPR2 and AQP2, whereas secondary forms are associated with biochemical abnormalities, obstructive uropathy or the use of certain medications, particularly lithium. Treatment of the disease is informed by identification of the underlying cause. Here we review the clinical aspects and diagnosis of NDI, the various aetiologies, current treatment options and potential future developments.
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Affiliation(s)
- Detlef Bockenhauer
- University College London Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
| | - Daniel G Bichet
- Departments of Medicine and Molecular and Integrative Physiology, Université de Montréal Research Center, Hôpital du Sacré-Coeur de Montréal, 5400 Boulevard Gouin Ouest, Montréal, QC H4J 1C5 Canada
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15
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Kortenoeven MLA, Fenton RA. Renal aquaporins and water balance disorders. Biochim Biophys Acta Gen Subj 2013; 1840:1533-49. [PMID: 24342488 DOI: 10.1016/j.bbagen.2013.12.002] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/26/2013] [Accepted: 12/09/2013] [Indexed: 12/17/2022]
Abstract
BACKGROUND Aquaporins (AQPs) are a family of proteins that can act as water channels. Regulation of AQPs is critical to osmoregulation and the maintenance of body water homeostasis. Eight AQPs are expressed in the kidney of which five have been shown to play a role in body water balance; AQP1, AQP2, AQP3, AQP4 and AQP7. AQP2 in particular is regulated by vasopressin. SCOPE OF REVIEW This review summarizes our current knowledge of the underlying mechanisms of various water balance disorders and their treatment strategies. MAJOR CONCLUSIONS Dysfunctions of AQPs are involved in disorders associated with disturbed water homeostasis. Hyponatremia with increased AQP levels can be caused by diseases with low effective circulating blood volume, such as congestive heart failure, or osmoregulation disorders such as the syndrome of inappropriate secretion of antidiuretic hormone. Treatment consists of fluid restriction, demeclocycline and vasopressin type-2 receptor antagonists. Decreased AQP levels can lead to diabetes insipidus (DI), characterized by polyuria and polydipsia. In central DI, vasopressin production is impaired, while in gestational DI, levels of the vasopressin-degrading enzyme vasopressinase are abnormally increased. Treatment consists of the vasopressin analogue dDAVP. Nephrogenic DI is caused by the inability of the kidney to respond to vasopressin and can be congenital, but is most commonly acquired, usually due to lithium therapy. Treatment consists of sufficient fluid supply, low-solute diet and diuretics. GENERAL SIGNIFICANCE In recent years, our understanding of the underlying mechanisms of water balance disorders has increased enormously, which has opened up several possible new treatment strategies. This article is part of a Special Issue entitled Aquaporins.
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Affiliation(s)
- Marleen L A Kortenoeven
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark.
| | - Robert A Fenton
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Center for Interactions of Proteins in Epithelial Transport (InterPrET), Aarhus University, Aarhus, Denmark.
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Moeller HB, Rittig S, Fenton RA. Nephrogenic diabetes insipidus: essential insights into the molecular background and potential therapies for treatment. Endocr Rev 2013; 34:278-301. [PMID: 23360744 PMCID: PMC3610677 DOI: 10.1210/er.2012-1044] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The water channel aquaporin-2 (AQP2), expressed in the kidney collecting ducts, plays a pivotal role in maintaining body water balance. The channel is regulated by the peptide hormone arginine vasopressin (AVP), which exerts its effects through the type 2 vasopressin receptor (AVPR2). Disrupted function or regulation of AQP2 or the AVPR2 results in nephrogenic diabetes insipidus (NDI), a common clinical condition of renal origin characterized by polydipsia and polyuria. Over several years, major research efforts have advanced our understanding of NDI at the genetic, cellular, molecular, and biological levels. NDI is commonly characterized as hereditary (congenital) NDI, arising from genetic mutations in the AVPR2 or AQP2; or acquired NDI, due to for exmple medical treatment or electrolyte disturbances. In this article, we provide a comprehensive overview of the genetic, cell biological, and pathophysiological causes of NDI, with emphasis on the congenital forms and the acquired forms arising from lithium and other drug therapies, acute and chronic renal failure, and disturbed levels of calcium and potassium. Additionally, we provide an overview of the exciting new treatment strategies that have been recently proposed for alleviating the symptoms of some forms of the disease and for bypassing G protein-coupled receptor signaling.
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Affiliation(s)
- Hanne B Moeller
- Department of Biomedicine, Aarhus University, and Department of Pediatrics, Aarhus University Hospital, Wilhelm Meyers Alle 3, Building 1234, Aarhus 8000, Denmark.
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Congenital nephrogenic diabetes insipidus: the current state of affairs. Pediatr Nephrol 2012; 27:2183-204. [PMID: 22427315 DOI: 10.1007/s00467-012-2118-8] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 01/14/2012] [Accepted: 01/17/2012] [Indexed: 01/02/2023]
Abstract
The anti-diuretic hormone arginine vasopressin (AVP) is released from the pituitary upon hypovolemia or hypernatremia, and regulates water reabsorption in the renal collecting duct principal cells. Binding of AVP to the arginine vasopressin receptor type 2 (AVPR2) in the basolateral membrane leads to translocation of aquaporin 2 (AQP2) water channels to the apical membrane of the collecting duct principal cells, inducing water permeability of the membrane. This results in water reabsorption from the pro-urine into the medullary interstitium following an osmotic gradient. Congenital nephrogenic diabetes insipidus (NDI) is a disorder associated with mutations in either the AVPR2 or AQP2 gene, causing the inability of patients to concentrate their pro-urine, which leads to a high risk of dehydration. This review focuses on the current knowledge regarding the cell biological aspects of congenital X-linked, autosomal-recessive and autosomal-dominant NDI while specifically addressing the latest developments in the field. Based on deepened mechanistic understanding, new therapeutic strategies are currently being explored, which we also discuss here.
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18
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Sasaki S, Chiga M, Kikuchi E, Rai T, Uchida S. Hereditary nephrogenic diabetes insipidus in Japanese patients: analysis of 78 families and report of 22 new mutations in AVPR2 and AQP2. Clin Exp Nephrol 2012; 17:338-44. [PMID: 23150186 DOI: 10.1007/s10157-012-0726-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 10/28/2012] [Indexed: 12/22/2022]
Abstract
BACKGROUND Familial form of nephrogenic diabetes insipidus (NDI) is a rare hereditary disease caused by arginine vasopressin type 2 receptor (AVPR2) or water channel aquaporin 2 (AQP2) gene mutations. It is speculated that 90% of NDI families carry disease-causing mutations in AVPR2 and 10% carry the mutations in AQP2; however, these percentages have not been supported by actual data. It is also unknown whether these percentages vary in different ethnic groups. METHODS Gene mutation analyses were performed for 78 Japanese NDI families. All exons and intron-exon boundaries of the AVPR2 and AQP2 genes were directly sequenced. RESULTS A total of 62 families (79%) carried disease-causing mutations in AVPR2, while nine families (12%) carried mutations in AQP2. We identified 22 novel putatively disease-causing mutations (19 in AVPR2 and 3 in AQP2). Regarding AVPR2, 52 disease-causing mutations were identified. Among them, missense mutations were most common (54%), followed by deletion mutations. In the 64 women who had monoallelic disease-causing AVPR2 mutations, 16 (25%) had NDI symptoms, including 4 complete NDI subjects. Regarding AQP2, 9 disease-causing mutations were identified in nine families. Two missense mutations and one deletion mutation showed a recessive inheritance, while one missense mutation and five small deletion mutations in the C-terminus of AQP2 showed a dominant inheritance. CONCLUSIONS Most Japanese NDI families carry disease-causing mutations in AVPR2 and 12% carry mutations in AQP2. A total of 22 novel putatively disease-causing mutations were identified. The relatively high occurrence of symptomatic carriers of AVPR2 mutations needs attention.
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Affiliation(s)
- Sei Sasaki
- Department of Nephrology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
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Neocleous V, Skordis N, Shammas C, Efstathiou E, Mastroyiannopoulos NP, Phylactou LA. Identification and characterization of a novel X-linked AVPR2 mutation causing partial nephrogenic diabetes insipidus: a case report and review of the literature. Metabolism 2012; 61:922-30. [PMID: 22386940 DOI: 10.1016/j.metabol.2012.01.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 01/04/2012] [Accepted: 01/05/2012] [Indexed: 11/23/2022]
Abstract
X-linked nephrogenic diabetes insipidus (NDI) is a rare disease characterized by a malfunctioning renal response to the antidiuretic hormone arginine vasopressin (AVP) due to mutations in the AVPR2 gene. A limited number of mutations in the AVPR2 gene resulting in partial phenotype have been described so far. In this mini-review the retrospective analysis of 13 known AVPR2 mutations that have been previously shown in vitro to partially abolish AVPR2 function is described, along with a novel mutation diagnosed in a kindred with partial NDI. In the present study, a 14 year old male and his 73 year old maternal grandfather were diagnosed with partial NDI based on the clinical phenotype, the water deprivation test and the inadequate response to 1-desamino-8-d-arginine vasopressin (DDAVP) administration. Sequencing analysis of the AVPR2 gene revealed the novel missense mutation p.N317S (g.1417A > G) in both patients. This mutation was re-created by site directed mutagenesis in an AVPR2 cDNA expression vector and was functionally characterized, in terms of arginine vasopressin (AVP) and DDAVP response. AVPR2 activity of the p.N317S mutant receptor after the AVP and DDAVP administration, as assessed by cAMP production was reduced and impaired when compared to cells that expressed the wild type AVPR2 gene. In conclusion, the affected members of this family have X-linked NDI with partial resistance to AVP, due to a missense mutation in the AVPR2 gene.
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Affiliation(s)
- Vassos Neocleous
- Department of Molecular Genetics, Function and Therapy, The Cyprus Institute of Neurology and Genetics, P.O. Box 23462, 1683 Nicosia, Cyprus
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Böselt I, Tramma D, Kalamitsou S, Niemeyer T, Nykänen P, Gräf KJ, Krude H, Marenzi KS, Di Candia S, Schöneberg T, Schulz A. Functional characterization of novel loss-of-function mutations in the vasopressin type 2 receptor gene causing nephrogenic diabetes insipidus. Nephrol Dial Transplant 2011; 27:1521-8. [PMID: 21917732 DOI: 10.1093/ndt/gfr487] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND X-linked nephrogenic diabetes insipidus (NDI) is a rare polyuric disorder caused by inactivating mutations in the arginine vasopressin receptor Type 2 (AVPR2) gene. METHODS NDI patients from six unrelated families were subjected to mutational analysis of the AVPR2 gene. In-depth in vitro characterization of novel AVPR2 mutants by a combination of functional and immunological techniques provided further insight into molecular mechanisms causing receptor dysfunction. RESULTS Mutational analysis revealed four novel (A89P, G107R, Q174R, W208X) and three recurrent (V277A, R337X, ΔR247-G250) mutations within the AVPR2 gene. One family carried the missense mutation R337X and a 12-bp deletion (ΔR247-G250), corresponding to a fragment in the third intracellular loop (ICL3), which was not genetically linked to R337X. The functionally tested missense mutations A89P, G107R and Q174R led to reduced receptor cell surface expression in transfected COS-7 cells, most probably due to misfolding and intracellular retention, and consequently to reduction or loss of agonist-mediated cyclic adenosine monophosphate formation. Deletion of R247-G250 had no effect on receptor function in vitro. Comparison with other mammalian AVPR2 orthologs showed that this part of the ICL3 is structurally not conserved and, therefore, less relevant for receptor function. In contrast, all missense mutations (A89P, G107R, Q174R, V277A) affect receptor positions that were fully preserved during mammalian evolution. CONCLUSION Our results provide valuable information about residues critical for AVPR2 folding, trafficking and function and proof that these mutations are responsible for causing NDI in the affected subjects.
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Affiliation(s)
- Iris Böselt
- Molecular Biochemistry, Institute of Biochemistry, Medical Faculty, University of Leipzig, Leipzig, Germany
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21
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Abstract
Over the past two decades, the genetic and molecular basis of familial forms of diabetes insipidus has been elucidated. Diabetes insipidus is a clinical syndrome characterized by the excretion of abnormally large volumes of diluted urine (polyuria) and increased fluid intake (polydipsia). The most common type of diabetes insipidus is caused by lack of the antidiuretic hormone arginine vasopressin (vasopressin), which is produced in the hypothalamus and secreted by the neurohypophysis. This type of diabetes insipidus is referred to here as neurohypophyseal diabetes insipidus. The syndrome can also result from resistance to the antidiuretic effects of vasopressin on the kidney, either at the level of the vasopressin 2 receptor or the aquaporin 2 water channel (which mediates the re-absorption of water from urine), and is referred to as renal or nephrogenic diabetes insipidus. Differentiation between these two types of diabetes insipidus and primary polydipsia can be difficult owing to the existence of partial as well as complete forms of vasopressin deficiency or resistance. Seven different familial forms of diabetes insipidus are known to exist. The clinical presentation, genetic basis and cellular mechanisms responsible for them vary considerably. This information has led to improved methods of differential diagnosis and could provide the basis of new forms of therapy.
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Affiliation(s)
- Muriel Babey
- Division of Endocrinology, Metabolism and Molecular Medicine, Feinberg School of Medicine, Northwestern University, Tarry 15, 303 East Chicago Avenue, Chicago, IL 60611, USA
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Perez-Cano HJ, Garnica-Hayashi RE, Zenteno JC. CHM gene molecular analysis and X-chromosome inactivation pattern determination in two families with choroideremia. Am J Med Genet A 2009; 149A:2134-40. [PMID: 19764077 DOI: 10.1002/ajmg.a.32727] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Choroideremia is an X-linked recessive retinal dystrophy characterized by progressive loss of the photoreceptor, the retinal pigment epithelium, and the choriocapillaris layers which ultimately can result in blindness by the fifth decade of life. The disease is caused by mutations in the gene CHM, which encodes a protein involved in the regulation of intracellular vesicular traffic. Typically, hemizygous males are affected by the disease and female carriers are asymptomatic with only a diffuse mottled pattern of hyperpigmentation on funduscopy. Uncommon instances of fully affected females have been described previously and these cases are proposed to arise from an skewed Lyonization mechanism preferentially inactivating the X chromosome carrying the normal CHM allele. In this work, the clinical and molecular features of two Mexican families with choroideremia are described. A novel and a previously described CHM mutation were identified. X-chromosome inactivation assays were performed in a total of 12 heterozygous carriers from the two families. In an affected female from family A, a random X-inactivation pattern was demonstrated; on the other hand, in a female carrier from family B displaying a conspicuous pattern of pigment epithelium mottling at the peripheral retina, a skewed X-inactivation pattern was found. However, the X-chromosome preferentially inactivated in this female was the one carrying the mutated allele. Our results add to the genotypic spectrum in choroideremia and does not support a correlation between X-inactivation status and abnormal retinal phenotype in heterozygous female carriers from these two families.
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Affiliation(s)
- Hector J Perez-Cano
- Research Unit, Institute of Ophthalmology Conde De Valenciana, Mexico City, Mexico
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Orstavik KH. X chromosome inactivation in clinical practice. Hum Genet 2009; 126:363-73. [PMID: 19396465 DOI: 10.1007/s00439-009-0670-5] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Accepted: 04/07/2009] [Indexed: 01/19/2023]
Abstract
X chromosome inactivation (XCI) is the transcriptional silencing of the majority of genes on one of the two X chromosomes in mammalian females. Females are, therefore, mosaics for two cell lines, one with the maternal X and one with the paternal X as the active chromosome. The relative proportion of the two cell lines, the X inactivation pattern, may be analyzed by simple assays in DNA from available tissues. This review focuses on medical issues related to XCI in X-linked disorders, and on the value of X inactivation analysis in clinical practice.
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Affiliation(s)
- Karen Helene Orstavik
- Department of Medical Genetics, Oslo University Hospital, Rikshospitalet and Faculty Division Rikshospitalet, University of Oslo, Forskningsveien 2B, 0027, Oslo, Norway.
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