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Liu Z, Zhao W, Cao C, Wang Y, Xiao L, Wang X, Jin C, Xiao J. Pituitary stalk interruption syndrome and liver cirrhosis associated with diabetes and an inactivating KCNJ11 gene mutation: a case report and literature review. Front Endocrinol (Lausanne) 2023; 14:1297146. [PMID: 38152125 PMCID: PMC10751576 DOI: 10.3389/fendo.2023.1297146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 11/28/2023] [Indexed: 12/29/2023] Open
Abstract
Background Pituitary stalk interruption syndrome (PSIS) is a congenital disease commonly found in patients with combined pituitary hormone deficiency (CPHD). Most PSIS patients manifest growth retardation and delayed puberty. We report a rare case of PSIS with tall stature, liver cirrhosis and diabetes, possibly caused by an inactivating KCNJ11 gene mutation. Case presentation A 37-year-old female patient initially presented with liver cirrhosis and diabetes, without any secondary sexual characteristics. Endocrine investigation indicated CPHD. Small anterior pituitary, invisible pituitary stalk and no eutopic posterior lobe hypersignal in the sella turcica viewed in magnetic resonance imaging (MRI) confirmed the diagnosis of PSIS. Despite receiving no growth hormone or sex hormone therapy, she reached a final height of 186 cm. Liver histopathology revealed nonalcoholic fatty cirrhosis. Genetic testing identified a heterozygous p.Arg301Cys mutation in the KCNJ11 gene. Conclusion This is a rare case of PSIS with liver cirrhosis and diabetes associated with an inactivating KCNJ11 gene mutation. It's supposed that early hyperinsulinism caused by the KCNJ11 gene mutation, as well as delayed epiphyseal closure due to estrogen deficiency, contributed to the patient's exceptionally tall stature. Untreated growth hormone deficiency (GHD) resulted in increased visceral fat, leading to nonalcoholic fatty liver disease (NAFLD) and cirrhosis. The decline in β cell function with age, combined with NAFLD, may have played a role in the development of diabetes.
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Song X, Cao Y, Ye J, Dai W, Zhang S, Ye S. A new mutation c.685G>A:p.E229K in the KCNJ11 gene: A case report of maturity-onset diabetes of the young13. Medicine (Baltimore) 2022; 101:e30668. [PMID: 36181023 PMCID: PMC9524910 DOI: 10.1097/md.0000000000030668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
INTRODUCTION Maturity-onset diabetes of the young (MODY) is an autosomal dominant monogenic diabetes. We report a pair of father and son diagnosed as MODY13 with a new mutation c.685G>A:p.E229K in the inwardly rectifying subfamily J, member 11 (KCNJ11) gene. CASE PRESENTATION A pair of father and son was examined after admission to the hospital and a whole exome test performed. Whole exome test showed that there was a mutation c.685G>A:p.E229K in the KCNJ11 gene encoding a potassium channel, KCNJ11. CONCLUSIONS The diagnosis of MODY13 requires genetic testing. After confirmation, medication and diet need to be adjusted to control blood glucose. The treatment plan was adjusted. After glimepiride was administered, symptoms of diabetes were effectively improved. According to our knowledge, this is the first reported mutation of c.685G>A:p.E229K in the KCNJ11 gene.
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Affiliation(s)
- Xinjie Song
- Department of Endocrinology, Second People’s Hospital of Hefei City, Hefei City, Anhui Province, China
| | - Yonghong Cao
- Department of Endocrinology, Second People’s Hospital of Hefei City, Hefei City, Anhui Province, China
- *Correspondence: Yonghong Cao, Department of Endocrinology, Second People’s Hospital of Hefei City, Intersection of Guangde Road and Leshui Road, Yaohai District, Hefei City, Anhui Province 230011, China (e-mail: )
| | - Jun Ye
- Department of Endocrinology, Second People’s Hospital of Hefei City, Hefei City, Anhui Province, China
| | - Wu Dai
- Department of Endocrinology, Second People’s Hospital of Hefei City, Hefei City, Anhui Province, China
| | - Suwan Zhang
- Department of Endocrinology, Second People’s Hospital of Hefei City, Hefei City, Anhui Province, China
| | - Shuai Ye
- Department of Endocrinology, Second People’s Hospital of Hefei City, Hefei City, Anhui Province, China
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Dusatkova P, Pavlikova M, Elblova L, Larionov V, Vesela K, Kolarova K, Sumnik Z, Lebl J, Pruhova S. Search for a time- and cost-saving genetic testing strategy for maturity-onset diabetes of the young. Acta Diabetol 2022; 59:1169-1178. [PMID: 35737141 PMCID: PMC9219402 DOI: 10.1007/s00592-022-01915-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 06/01/2022] [Indexed: 11/16/2022]
Abstract
AIMS Correct genetic diagnosis of maturity-onset diabetes of the young (MODY) is beneficial for person's diabetes management compared to no genetic testing. Aim of the present study was a search for optimal time- and cost-saving strategies by comparing two approaches of genetic testing of participants with clinical suspicion of MODY. METHODS A total of 121 consecutive probands referred for suspicion of MODY (Group A) were screened using targeted NGS (tNGS), while the other 112 consecutive probands (Group B) underwent a single gene test based on phenotype, and in cases of negative findings, tNGS was conducted. The study was performed in two subsequent years. The genetic results, time until reporting of the final results and financial expenses were compared between the groups. RESULTS MODY was confirmed in 30.6% and 40.2% probands from Groups A and B, respectively; GCK-MODY was predominant (72.2% in Group A and 77.8% in Group B). The median number of days until results reporting was 184 days (IQR 122-258) in Group A and 91 days (44-174) in Group B (p < 0.00001). Mean costs per person were higher for Group A (639 ± 30 USD) than for Group B (584 ± 296 USD; p = 0.044). CONCLUSIONS The two-step approach represented a better strategy for genetic investigation of MODY concerning time and costs compared to direct tNGS. Although a single-gene investigation clarified the diabetes aetiology in the majority of cases, tNGS could reveal rare causes of MODY and expose possible limitations of both standard genetic techniques and clinical evaluation.
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Affiliation(s)
- Petra Dusatkova
- Department of Paediatrics, 2nd Faculty of Medicine, Charles University and University Hospital Motol, V Uvalu 84, 15006, Prague, Czech Republic.
| | - Marketa Pavlikova
- Department of Probability and Mathematical Statistics, Faculty of Mathematics and Physics, Charles University, Sokolovska 83, 18675, Prague, Czech Republic
| | - Lenka Elblova
- Department of Paediatrics, 2nd Faculty of Medicine, Charles University and University Hospital Motol, V Uvalu 84, 15006, Prague, Czech Republic
| | - Vladyslav Larionov
- Department of Paediatrics, 2nd Faculty of Medicine, Charles University and University Hospital Motol, V Uvalu 84, 15006, Prague, Czech Republic
| | - Klara Vesela
- Department of Paediatrics, 2nd Faculty of Medicine, Charles University and University Hospital Motol, V Uvalu 84, 15006, Prague, Czech Republic
| | - Katerina Kolarova
- Department of Paediatrics, 2nd Faculty of Medicine, Charles University and University Hospital Motol, V Uvalu 84, 15006, Prague, Czech Republic
| | - Zdenek Sumnik
- Department of Paediatrics, 2nd Faculty of Medicine, Charles University and University Hospital Motol, V Uvalu 84, 15006, Prague, Czech Republic
| | - Jan Lebl
- Department of Paediatrics, 2nd Faculty of Medicine, Charles University and University Hospital Motol, V Uvalu 84, 15006, Prague, Czech Republic
| | - Stepanka Pruhova
- Department of Paediatrics, 2nd Faculty of Medicine, Charles University and University Hospital Motol, V Uvalu 84, 15006, Prague, Czech Republic
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Gaál Z, Szűcs Z, Kántor I, Luczay A, Tóth-Heyn P, Benn O, Felszeghy E, Karádi Z, Madar L, Balogh I. A Comprehensive Analysis of Hungarian MODY Patients-Part I: Gene Panel Sequencing Reveals Pathogenic Mutations in HNF1A, HNF1B, HNF4A, ABCC8 and INS Genes. Life (Basel) 2021; 11:life11080755. [PMID: 34440499 PMCID: PMC8399091 DOI: 10.3390/life11080755] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/20/2021] [Accepted: 07/24/2021] [Indexed: 12/13/2022] Open
Abstract
Maturity-onset diabetes of the young (MODY) has about a dozen known causal genes to date, the most common ones being HNF1A, HNF4A, HNF1B and GCK. The phenotype of this clinically and genetically heterogeneous form of diabetes depends on the gene in which the patient has the mutation. We have tested 450 Hungarian index patients with suspected MODY diagnosis with Sanger sequencing and next-generation sequencing and found a roughly 30% positivity rate. More than 70% of disease-causing mutations were found in the GCK gene, about 20% in the HNF1A gene and less than 10% in other MODY-causing genes. We found 8 pathogenic and 9 likely pathogenic mutations in the HNF1A gene in a total of 48 patients and family members. In the case of HNF1A-MODY, the recommended first-line treatment is low dose sulfonylurea but according to our data, the majority of our patients had been on unnecessary insulin therapy at the time of requesting their genetic testing. Our data highlights the importance of genetic testing in the diagnosis of MODY and the establishment of the MODY subtype in order to choose the most appropriate treatment.
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Affiliation(s)
- Zsolt Gaál
- 4th Department of Medicine, Jósa András Teaching Hospital, 4400 Nyíregyháza, Hungary;
| | - Zsuzsanna Szűcs
- Division of Clinical Genetics, Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.S.); (L.M.)
| | - Irén Kántor
- Department of Pediatrics, Jósa András Teaching Hospital, 4400 Nyíregyháza, Hungary;
| | - Andrea Luczay
- 1st Department of Pediatrics, Semmelweis University, 1085 Budapest, Hungary; (A.L.); (P.T.-H.)
| | - Péter Tóth-Heyn
- 1st Department of Pediatrics, Semmelweis University, 1085 Budapest, Hungary; (A.L.); (P.T.-H.)
| | - Orsolya Benn
- Department of Pediatrics, Szent György Hospital of Fejér County, 8000 Székesfehérvár, Hungary; (O.B.); (Z.K.)
| | - Enikő Felszeghy
- Department of Pediatrics, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary;
| | - Zsuzsanna Karádi
- Department of Pediatrics, Szent György Hospital of Fejér County, 8000 Székesfehérvár, Hungary; (O.B.); (Z.K.)
| | - László Madar
- Division of Clinical Genetics, Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.S.); (L.M.)
| | - István Balogh
- Division of Clinical Genetics, Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.S.); (L.M.)
- Correspondence:
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Structure based analysis of K ATP channel with a DEND syndrome mutation in murine skeletal muscle. Sci Rep 2021; 11:6668. [PMID: 33758250 PMCID: PMC7988048 DOI: 10.1038/s41598-021-86121-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 03/11/2021] [Indexed: 12/12/2022] Open
Abstract
Developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome, the most severe end of neonatal diabetes mellitus, is caused by mutation in the ATP-sensitive potassium (KATP) channel. In addition to diabetes, DEND patients present muscle weakness as one of the symptoms, and although the muscle weakness is considered to originate in the brain, the pathological effects of mutated KATP channels in skeletal muscle remain elusive. Here, we describe the local effects of the KATP channel on muscle by expressing the mutation present in the KATP channels of the DEND syndrome in the murine skeletal muscle cell line C2C12 in combination with computer simulation. The present study revealed that the DEND mutation can lead to a hyperpolarized state of the muscle cell membrane, and molecular dynamics simulations based on a recently reported high-resolution structure provide an explanation as to why the mutation reduces ATP sensitivity and reveal the changes in the local interactions between ATP molecules and the channel.
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Abstract
The endoderm is the innermost germ layer that forms the linings of the respiratory and gastrointestinal tracts, and their associated organs, during embryonic development. Xenopus embryology experiments have provided fundamental insights into how the endoderm develops in vertebrates, including the critical role of TGFβ-signaling in endoderm induction,elucidating the gene regulatory networks controlling germ layer development and the key molecular mechanisms regulating endoderm patterning and morphogenesis. With new genetic, genomic, and imaging approaches, Xenopus is now routinely used to model human disease, discover mechanisms underlying endoderm organogenesis, and inform differentiation protocols for pluripotent stem cell differentiation and regenerative medicine applications. In this chapter, we review historical and current discoveries of endoderm development in Xenopus, then provide examples of modeling human disease and congenital defects of endoderm-derived organs using Xenopus.
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Affiliation(s)
- Nicole A Edwards
- Division of Developmental Biology, Center for Stem Cell and Organoid Medicine, Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States.
| | - Aaron M Zorn
- Division of Developmental Biology, Center for Stem Cell and Organoid Medicine, Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States.
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7
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He B, Li X, Zhou Z. Continuous spectrum of glucose dysmetabolism due to the KCNJ11 gene mutation-Case reports and review of the literature. J Diabetes 2021; 13:19-32. [PMID: 32935446 DOI: 10.1111/1753-0407.13114] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 07/20/2020] [Accepted: 09/03/2020] [Indexed: 12/01/2022] Open
Abstract
The KCNJ11 gene encodes the Kir6.2 subunit of the adenosine triphosphate-sensitive potassium (KATP ) channel, which plays a key role in insulin secretion. Monogenic diseases caused by KCNJ11 gene mutation are rare and easily misdiagnosed. It has been shown that mutations in the KCNJ11 gene are associated with neonatal diabetes mellitus (NDM), maturity-onset diabetes of the young 13 (MODY13), type 2 diabetes mellitus (T2DM), and hyperinsulinemic hypoglycemia. We report four patients with KCNJ11 gene mutations and provide a systematic review of the literature. A boy with diabetes onset at the age of 1 month was misdiagnosed as type 1 diabetes mellitus (T1DM) for 12 years and received insulin therapy continuously, resulting in poor glycemic control. He was diagnosed as NDM with KCNJ11 E322K gene mutation, and glibenclamide was given to replace exogenous insulin. The successful transfer time was 4 months, much longer than the previous unsuccessful standard of 4 weeks. The other three patients were two sisters and their mother; the younger sister was misdiagnosed with T1DM at 13 years old, while the elder sister was diagnosed with diabetes (type undefined) at 16 years old. They were treated with insulin for 3 years, with poor glycemic control. Their mother was diagnosed with T2DM and achieved good glycemia control with glimepiride. They were diagnosed as MODY13 because of the autosomal dominant inheritance of two generations, early onset of diabetes before 25 years of age in the two sisters, and the presence of the KCNJ11 N48D gene mutation. All patients successfully transferred to sulfonylureas with excellent glycemic control. Therefore, the wide spectrum of clinical phenotypes of glucose dysmetabolism caused by KCNJ11 should be recognized to reduce misdiagnosis and implement appropriate treatment.
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Affiliation(s)
- Binbin He
- Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, China
- Key Laboratory of Diabetes Immunology (Central South University), Ministry of Education; National Clinical Research Center for Metabolic Diseases, Changsha, China
| | - Xia Li
- Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, China
- Key Laboratory of Diabetes Immunology (Central South University), Ministry of Education; National Clinical Research Center for Metabolic Diseases, Changsha, China
| | - Zhiguang Zhou
- Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, China
- Key Laboratory of Diabetes Immunology (Central South University), Ministry of Education; National Clinical Research Center for Metabolic Diseases, Changsha, China
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8
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Wong SK. Repurposing New Use for Old Drug Chloroquine against Metabolic Syndrome: A Review on Animal and Human Evidence. Int J Med Sci 2021; 18:2673-2688. [PMID: 34104100 PMCID: PMC8176183 DOI: 10.7150/ijms.58147] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 05/04/2021] [Indexed: 01/15/2023] Open
Abstract
Chloroquine (CQ) and hydroxychloroquine (HCQ) are traditional anti-malarial drugs that have been repurposed for new therapeutic uses in many diseases due to their simple usage and cost-effectiveness. The pleiotropic effects of CQ and HCQ in regulating blood pressure, glucose homeostasis, lipid, and carbohydrate metabolism have been previously described in vivo and in humans, thus suggesting their role in metabolic syndrome (MetS) prevention. The anti-hyperglycaemic, anti-hyperlipidaemic, cardioprotective, anti-hypertensive, and anti-obesity effects of CQ and HCQ might be elicited through reduction of inflammatory response and oxidative stress, improvement of endothelial function, activation of insulin signalling pathway, inhibition of lipogenesis and autophagy, as well as regulation of adipokines and apoptosis. In conclusion, the current state of knowledge supported the repurposing of CQ and HCQ usage in the management of MetS.
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Affiliation(s)
- Sok Kuan Wong
- Department of Pharmacology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Bandar Tun Razak, 56000 Cheras, Kuala Lumpur, Malaysia
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9
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Garcin L, Mericq V, Fauret-Amsellem AL, Cave H, Polak M, Beltrand J. Neonatal diabetes due to potassium channel mutation: Response to sulfonylurea according to the genotype. Pediatr Diabetes 2020; 21:932-941. [PMID: 32418263 DOI: 10.1111/pedi.13041] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 04/17/2020] [Accepted: 05/04/2020] [Indexed: 12/21/2022] Open
Abstract
OBJECTIVE A precision medicine approach is used to improve treatment of patients with monogenic diabetes. Herein, we searched SU efficiency according to the genotype-phenotype correlation, dosage used, and side effects. RESEARCH DESIGN AND METHODS Systematic review conducted according the PRISMA control criteria identifying relevant studies evaluating the in vivo and in vitro sensitivity of ATP-dependent potassium channels according to the characteristics of genetic mutation. RESULTS Hundred and three selected articles with complete data in 502 cases in whom 413 (82.3%) had mutations in KCNJ11 (#64) and 89 in ABCC8 (# 56). Successful transfer from insulin to SU was achieved in 91% and 86.5% patients, respectively, at a mean age of 36.5 months (0-63 years). Among patients with KCNJ11 and ABCC8 mutations 64 and 46 were associated with constant success, 5 and 5 to constant failure, and 10 and 4 to variable degrees of reported success rate, respectively. The glibenclamide dosage required for each genotype ranged from 0.017 to 2.8 mg/kg/day. Comparing both the in vivo and in vitro susceptibility results, some mutations appear more sensitive than others to sulfonylurea treatment. Side effects were reported in 17/103 of the included articles: mild gastrointestinal symptoms and hypoglycaemia were the most common. One premature patient had an ulcerative necrotizing enterocolitis which association with SU is difficult to ascertain. CONCLUSIONS Sulfonylureas are an effective treatment for monogenic diabetes due to KCNJ11 and ABCC8 genes mutations. The success of the treatment is conditioned by differences in pharmacogenetics, younger age, pharmacokinetics, compliance, and maximal dose used.
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Affiliation(s)
- Laure Garcin
- Pediatric Gynecology Diabetes and Endocrinology, APHP Centre - Hôpital Universitaire Necker Enfants Malades, Paris, France
| | - Veronica Mericq
- Faculty of Medicine, Institute of Maternal and Child Research (IDIMI), University of Chile, Santiago, Chile
| | - Anne-Laure Fauret-Amsellem
- Département de Génétique, Assistance Publique-Hôpitaux de Paris, Hôpital Universitaire Robert Debré, Paris, France.,Centre de référence national des maladies rares de la sécrétion d'insuline et de la sensibilité à l'insuline, PRISIS, Paris, France
| | - Helene Cave
- Département de Génétique, Assistance Publique-Hôpitaux de Paris, Hôpital Universitaire Robert Debré, Paris, France.,Centre de référence national des maladies rares de la sécrétion d'insuline et de la sensibilité à l'insuline, PRISIS, Paris, France.,Université de Paris, Paris, France
| | - Michel Polak
- Pediatric Gynecology Diabetes and Endocrinology, APHP Centre - Hôpital Universitaire Necker Enfants Malades, Paris, France.,Centre de référence national des maladies rares de la sécrétion d'insuline et de la sensibilité à l'insuline, PRISIS, Paris, France.,Université de Paris, Paris, France.,Institut IMAGINE, Paris, France.,Inserm U1016, Institut Cochin, Paris, France.,ENDO European Reference Network, Main Thematic Group 3, Genetic Disorders of Glucose and Insulin Homeostasis, European Reference Networks, Paris, France
| | - Jacques Beltrand
- Pediatric Gynecology Diabetes and Endocrinology, APHP Centre - Hôpital Universitaire Necker Enfants Malades, Paris, France.,Centre de référence national des maladies rares de la sécrétion d'insuline et de la sensibilité à l'insuline, PRISIS, Paris, France.,Université de Paris, Paris, France.,Institut IMAGINE, Paris, France.,Inserm U1016, Institut Cochin, Paris, France.,ENDO European Reference Network, Main Thematic Group 3, Genetic Disorders of Glucose and Insulin Homeostasis, European Reference Networks, Paris, France
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10
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Pipatpolkai T, Usher S, Stansfeld PJ, Ashcroft FM. New insights into K ATP channel gene mutations and neonatal diabetes mellitus. Nat Rev Endocrinol 2020; 16:378-393. [PMID: 32376986 DOI: 10.1038/s41574-020-0351-y] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/17/2020] [Indexed: 12/12/2022]
Abstract
The ATP-sensitive potassium channel (KATP channel) couples blood levels of glucose to insulin secretion from pancreatic β-cells. KATP channel closure triggers a cascade of events that results in insulin release. Metabolically generated changes in the intracellular concentrations of adenosine nucleotides are integral to this regulation, with ATP and ADP closing the channel and MgATP and MgADP increasing channel activity. Activating mutations in the genes encoding either of the two types of KATP channel subunit (Kir6.2 and SUR1) result in neonatal diabetes mellitus, whereas loss-of-function mutations cause hyperinsulinaemic hypoglycaemia of infancy. Sulfonylurea and glinide drugs, which bind to SUR1, close the channel through a pathway independent of ATP and are now the primary therapy for neonatal diabetes mellitus caused by mutations in the genes encoding KATP channel subunits. Insight into the molecular details of drug and nucleotide regulation of channel activity has been illuminated by cryo-electron microscopy structures that reveal the atomic-level organization of the KATP channel complex. Here we review how these structures aid our understanding of how the various mutations in the genes encoding Kir6.2 (KCNJ11) and SUR1 (ABCC8) lead to a reduction in ATP inhibition and thereby neonatal diabetes mellitus. We also provide an update on known mutations and sulfonylurea therapy in neonatal diabetes mellitus.
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Affiliation(s)
- Tanadet Pipatpolkai
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Samuel Usher
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Phillip J Stansfeld
- Department of Biochemistry, University of Oxford, Oxford, UK
- School of Life Sciences, University of Warwick, Coventry, UK
- Department of Chemistry, University of Warwick, Coventry, UK
| | - Frances M Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
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11
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Letourneau LR, Greeley SAW. Precision Medicine: Long-Term Treatment with Sulfonylureas in Patients with Neonatal Diabetes Due to KCNJ11 Mutations. Curr Diab Rep 2019; 19:52. [PMID: 31250216 PMCID: PMC6894166 DOI: 10.1007/s11892-019-1175-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
PURPOSE OF REVIEW The goal of this review is to provide updates on the safety and efficacy of long-term sulfonylurea use in patients with KCNJ11-related diabetes. Publications from 2004 to the present were reviewed with an emphasis on literature since 2014. RECENT FINDINGS Sulfonylureas, often taken at high doses, have now been utilized effectively in KCNJ11 patients for over 10 years. Mild-moderate hypoglycemia can occur, but in two studies with a combined 975 patient-years on sulfonylureas, no severe hypoglycemic events were reported. Improvements in neurodevelopment and motor function after transition to sulfonylureas continue to be described. Sulfonylureas continue to be an effective, sustainable, and safe treatment for KCNJ11-related diabetes. Ongoing follow-up of patients in research registries will allow for deeper understanding of the facilitators and barriers to long-term sustainability. Further understanding of the effect of sulfonylurea on long-term neurodevelopmental outcomes, and the potential for adjunctive therapies, is needed.
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Affiliation(s)
- Lisa R Letourneau
- Section of Pediatric and Adult Endocrinology, Diabetes, and Metabolism Kovler Diabetes Center, University of Chicago, 5841 S. Maryland Ave., MC1027-N235, Chicago, IL, 60637, USA
| | - Siri Atma W Greeley
- Section of Pediatric and Adult Endocrinology, Diabetes, and Metabolism Kovler Diabetes Center, University of Chicago, 5841 S. Maryland Ave., MC1027-N235, Chicago, IL, 60637, USA.
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12
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Bowman P, Day J, Torrens L, Shepherd MH, Knight BA, Ford TJ, Flanagan SE, Chakera A, Hattersley AT, Zeman A. Cognitive, Neurological, and Behavioral Features in Adults With KCNJ11 Neonatal Diabetes. Diabetes Care 2019; 42:215-224. [PMID: 30377186 PMCID: PMC6354912 DOI: 10.2337/dc18-1060] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 09/22/2018] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Central nervous system (CNS) features in children with permanent neonatal diabetes (PNDM) due to KCNJ11 mutations have a major impact on affected families. Sulfonylurea therapy achieves outstanding metabolic control but only partial improvement in CNS features. The effects of KCNJ11 mutations on the adult brain and their functional impact are not well understood. We aimed to characterize the CNS features in adults with KCNJ11 PNDM compared with adults with INS PNDM. RESEARCH DESIGN AND METHODS Adults with PNDM due to KCNJ11 mutations (n = 8) or INS mutations (n = 4) underwent a neurological examination and completed standardized neuropsychological tests/questionnaires about development/behavior. Four individuals in each group underwent a brain MRI scan. Test scores were converted to Z scores using normative data, and outcomes were compared between groups. RESULTS In individuals with KCNJ11 mutations, neurological examination was abnormal in seven of eight; predominant features were subtle deficits in coordination/motor sequencing. All had delayed developmental milestones and/or required learning support/special schooling. Half had features and/or a clinical diagnosis of autism spectrum disorder. KCNJ11 mutations were also associated with impaired attention, working memory, and perceptual reasoning and reduced intelligence quotient (IQ) (median IQ KCNJ11 vs. INS mutations 76 vs. 111, respectively; P = 0.02). However, no structural brain abnormalities were noted on MRI. The severity of these features was related to the specific mutation, and they were absent in individuals with INS mutations. CONCLUSIONS KCNJ11 PNDM is associated with specific CNS features that are not due to long-standing diabetes, persist into adulthood despite sulfonylurea therapy, and represent the major burden from KCNJ11 mutations.
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Affiliation(s)
- Pamela Bowman
- University of Exeter Medical School, Exeter, U.K. .,Exeter National Institute for Health Research Clinical Research Facility, Exeter, U.K
| | - Jacob Day
- University of Exeter Medical School, Exeter, U.K.,Exeter National Institute for Health Research Clinical Research Facility, Exeter, U.K
| | - Lorna Torrens
- Kent Neuropsychology Service, Kent and Medway NHS and Social Care Partnership Trust, Gillingham, U.K
| | - Maggie H Shepherd
- University of Exeter Medical School, Exeter, U.K.,Exeter National Institute for Health Research Clinical Research Facility, Exeter, U.K
| | - Bridget A Knight
- University of Exeter Medical School, Exeter, U.K.,Exeter National Institute for Health Research Clinical Research Facility, Exeter, U.K
| | | | | | - Ali Chakera
- University of Exeter Medical School, Exeter, U.K.,Exeter National Institute for Health Research Clinical Research Facility, Exeter, U.K
| | - Andrew T Hattersley
- University of Exeter Medical School, Exeter, U.K.,Exeter National Institute for Health Research Clinical Research Facility, Exeter, U.K
| | - Adam Zeman
- University of Exeter Medical School, Exeter, U.K
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13
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Abstract
In addition to the common types of diabetes mellitus, two major monogenic diabetes forms exist. Maturity-onset diabetes of the young (MODY) represents a heterogenous group of monogenic, autosomal dominant diseases. MODY accounts for 1-2% of all diabetes cases, and it is not just underdiagnosed but often misdiagnosed to type 1 or type 2 diabetes. More than a dozen MODY genes have been identified to date, and their molecular classification is of great importance in the correct treatment decision and in the judgment of the prognosis. The most prevalent subtypes are HNF1A, GCK, and HNF4A. Genetic testing for MODY has changed recently due to the technological advancements, as contrary to the sequential testing performed in the past, nowadays all MODY genes can be tested simultaneously by next-generation sequencing. The other major group of monogenic diabetes is neonatal diabetes mellitus which can be transient or permanent, and often the diabetes is a part of a syndrome. It is a severe monogenic disease appearing in the first 6 months of life. The hyperglycemia usually requires insulin. There are two forms, permanent neonatal diabetes mellitus (PNDM) and transient neonatal diabetes mellitus (TNDM). In TNDM, the diabetes usually reverts within several months but might relapse later in life. The incidence of NDM is 1:100,000-1:400,000 live births, and PNDM accounts for half of the cases. Most commonly, neonatal diabetes is caused by mutations in KCNJ11 and ABCC8 genes encoding the ATP-dependent potassium channel of the β cell. Neonatal diabetes has experienced a quick and successful transition into the clinical practice since the discovery of the molecular background. In case of both genetic diabetes groups, recent guidelines recommend genetic testing.
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Affiliation(s)
- Zsolt Gaál
- 4th Department of Medicine, Jósa András Teaching Hospital, Nyíregyháza, Hungary
| | - István Balogh
- Division of Clinical Genetics, Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
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14
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Tinker A, Aziz Q, Li Y, Specterman M. ATP‐Sensitive Potassium Channels and Their Physiological and Pathophysiological Roles. Compr Physiol 2018; 8:1463-1511. [DOI: 10.1002/cphy.c170048] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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15
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Breidbart E, Golden L, Gonzaga-Jauregui C, Deng L, Lanzano P, LeDuc C, Guo J, Overton JD, Reid J, Shuldiner A, Chung WK. KCNJ11 Mutation in One Family is Associated with Adult-Onset Rather than Neonatal-Onset Diabetes Mellitus. AACE Clin Case Rep 2018. [DOI: 10.4158/accr-2018-0007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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16
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Gole E, Oikonomou S, Ellard S, De Franco E, Karavanaki K. A Novel KCNJ11 Mutation Associated with Transient Neonatal Diabetes. J Clin Res Pediatr Endocrinol 2018; 10:175-178. [PMID: 28943514 PMCID: PMC5985388 DOI: 10.4274/jcrpe.5166] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Neonatal diabetes mellitus (NDM) is a rare type of monogenic diabetes that presents in the first 6 months of life. Activating mutations in the KCNJ11 gene encoding for the Kir6.2 subunit of the ATP-sensitive potassium (KATP ) channel can lead to transient NDM (TNDM) or to permanent NDM (PNDM). A female infant presented on the 22nd day of life with severe hyperglycemia and ketoacidosis (glucose: 907mg/dL, blood gas pH: 6.84, HCO3: 6 mmol/L). She was initially managed with intravenous (IV) fluids and IV insulin. Ketoacidosis resolved within 48 hours and she was started on subcutaneous insulin injections with intermediate acting insulin NPH twice daily requiring initially 0.75-1.35 IU/kg/d. Pre-prandial C-peptide levels were 0.51 ng/mL (normal: 1.77-4.68). Insulin requirements were gradually reduced and insulin administration was discontinued at the age of 10 months with subsequent normal glucose and HbA1c levels. C-peptide levels normalized (pre-prandial: 1.6 ng/mL, postprandial: 2 ng/mL). Genetic analysis identified a novel missense mutation (p.Pro254Gln) in the KCNJ11 gene. We report a novel KCNJ11 mutation in a patient who presented in the first month of life with a phenotype of NDM that subsided at the age of 10 months. It is likely that the novel p.P254Q mutation results in mild impairment of the KATP channel function leading to TNDM.
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Affiliation(s)
- Evangelia Gole
- University of Athens, 2nd Department of Pediatrics, “P&A Kyriakou” Children’s Hospital, Diabetes and Metabolism Unit, Athens, Greece
| | - Stavroula Oikonomou
- University of Athens, 2nd Department of Pediatrics, “P&A Kyriakou” Children’s Hospital, Diabetes and Metabolism Unit, Athens, Greece
| | - Sian Ellard
- University of Exeter Medical School, Institute of Biomedical and Clinical Science, Exeter, United Kingdom
| | - Elisa De Franco
- University of Exeter Medical School, Institute of Biomedical and Clinical Science, Exeter, United Kingdom
| | - Kyriaki Karavanaki
- University of Athens, 2nd Department of Pediatrics, “P&A Kyriakou” Children’s Hospital, Diabetes and Metabolism Unit, Athens, Greece,* Address for Correspondence: University of Athens, 2nd Department of Pediatrics, “P&A Kyriakou” Children’s Hospital, Diabetes and Metabolism Unit, Athens, Greece Phone: +30-210-7726488 E-mail:
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17
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Proks P, Puljung MC, Vedovato N, Sachse G, Mulvaney R, Ashcroft FM. Running out of time: the decline of channel activity and nucleotide activation in adenosine triphosphate-sensitive K-channels. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0426. [PMID: 27377720 PMCID: PMC4938026 DOI: 10.1098/rstb.2015.0426] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/17/2016] [Indexed: 11/29/2022] Open
Abstract
KATP channels act as key regulators of electrical excitability by coupling metabolic cues—mainly intracellular adenine nucleotide concentrations—to cellular potassium ion efflux. However, their study has been hindered by their rapid loss of activity in excised membrane patches (rundown), and by a second phenomenon, the decline of activation by Mg-nucleotides (DAMN). Degradation of PI(4,5)P2 and other phosphoinositides is the strongest candidate for the molecular cause of rundown. Broad evidence indicates that most other determinants of rundown (e.g. phosphorylation, intracellular calcium, channel mutations that affect rundown) also act by influencing KATP channel regulation by phosphoinositides. Unfortunately, experimental conditions that reproducibly prevent rundown have remained elusive, necessitating post hoc data compensation. Rundown is clearly distinct from DAMN. While the former is associated with pore-forming Kir6.2 subunits, DAMN is generally a slower process involving the regulatory sulfonylurea receptor (SUR) subunits. We speculate that it arises when SUR subunits enter non-physiological conformational states associated with the loss of SUR nucleotide-binding domain dimerization following prolonged exposure to nucleotide-free conditions. This review presents new information on both rundown and DAMN, summarizes our current understanding of these processes and considers their physiological roles. This article is part of the themed issue ‘Evolution brings Ca2+ and ATP together to control life and death’.
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Affiliation(s)
- Peter Proks
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Michael C Puljung
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Natascia Vedovato
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Gregor Sachse
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Rachel Mulvaney
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Frances M Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
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18
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Abstract
Since the discovery of the KATP channel in 1983, numerous studies have revealed its physiological functions. The KATP channel is expressed in various organs, including the pancreas, brain and skeletal muscles. It functions as a "metabolic sensor" that converts the metabolic status to electrical activity. In pancreatic beta-cells, the KATP channel regulates the secretion of insulin by sensing a change in the blood glucose level and thus maintains glucose homeostasis. In 2004, heterozygous gain-of-function mutations in the KCNJ11 gene, which encodes the Kir6.2 subunit of the KATP channel, were found to cause neonatal diabetes. In some mutations, diabetes is accompanied by severe neurological symptoms [developmental delay, epilepsy, neonatal diabetes (DEND) syndrome]. This review focuses on mutations of Kir6.2, the pore-forming subunit and sulfonylurea receptor (SUR) 1, the regulatory subunit of the KATP channel, which cause neonatal diabetes/DEND syndrome and also discusses the findings of the pathological mechanisms that are associated with neonatal diabetes, and its neurological features.
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Affiliation(s)
- Kenju Shimomura
- Department of Medical Electrophysiology, Fukushima Medical University School of Medicine, Japan
| | - Yuko Maejima
- Department of Medical Electrophysiology, Fukushima Medical University School of Medicine, Japan
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19
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Notary AM, Westacott MJ, Hraha TH, Pozzoli M, Benninger RKP. Decreases in Gap Junction Coupling Recovers Ca2+ and Insulin Secretion in Neonatal Diabetes Mellitus, Dependent on Beta Cell Heterogeneity and Noise. PLoS Comput Biol 2016; 12:e1005116. [PMID: 27681078 PMCID: PMC5040430 DOI: 10.1371/journal.pcbi.1005116] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 08/23/2016] [Indexed: 11/29/2022] Open
Abstract
Diabetes is caused by dysfunction to β-cells in the islets of Langerhans, disrupting insulin secretion and glucose homeostasis. Gap junction-mediated electrical coupling between β-cells in the islet plays a major role in coordinating a pulsatile secretory response at elevated glucose and suppressing insulin secretion at basal glucose. Previously, we demonstrated that a critical number of inexcitable cells can rapidly suppress the overall islet response, as a result of gap junction coupling. This was demonstrated in a murine model of Neonatal Diabetes Mellitus (NDM) involving expression of ATP-insensitive KATP channels, and by a multi-cellular computational model of islet electrical activity. Here we examined the mechanisms by which gap junction coupling contributes to islet dysfunction in NDM. We first verified the computational model against [Ca2+] and insulin secretion measurements in islets expressing ATP-insensitive KATP channels under different levels of gap junction coupling. We then applied this model to predict how different KATP channel mutations found in NDM suppress [Ca2+], and the role of gap junction coupling in this suppression. We further extended the model to account for stochastic noise and insulin secretion dynamics. We found experimentally and in the islet model that reductions in gap junction coupling allow progressively greater glucose-stimulated [Ca2+] and insulin secretion following expression of ATP-insensitive KATP channels. The model demonstrated good correspondence between suppression of [Ca2+] and clinical presentation of different NDM mutations. Significant recoveries in [Ca2+] and insulin secretion were predicted for many mutations upon reductions in gap junction coupling, where stochastic noise played a significant role in the recoveries. These findings provide new understanding how the islet functions as a multicellular system and for the role of gap junction channels in exacerbating the effects of decreased cellular excitability. They further suggest novel therapeutic options for NDM and other monogenic forms of diabetes. Diabetes is a disease reaching a global epidemic, which results from dysfunction to the islets of Langerhans in the pancreas and their ability to secrete the hormone insulin to regulate glucose homeostasis. Islets are multicellular structures that show extensive coupling between heterogeneous cellular units; and central to the causes of diabetes is a dysfunction to these cellular units and their interactions. Understanding the inter-relationship between structure and function is challenging in biological systems, but is crucial to the cause of disease and discovering therapeutic targets. With the goal of further characterizing the islet of Langerhans and its excitable behavior, we examined the role of important channels in the islet where dysfunction is linked to or causes diabetes. Advances in our ability to computationally model perturbations in physiological systems has allowed for the testing of hypothesis quickly, in systems that are not experimentally accessible. Using an experimentally validated model and modeling human mutations, we discover that monogenic forms of diabetes may be remedied by a reduction in electrical coupling between cells; either alone or in conjunction with pharmacological intervention. Knowledge of biological systems in general is also helped by these findings, in that small changes to cellular elements may lead to major disruptions in the overall system. This may then be overcome by allowing the system components to function independently in the presence of dysfunction to individual cells.
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Affiliation(s)
- Aleena M. Notary
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Matthew J. Westacott
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Thomas H. Hraha
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Marina Pozzoli
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Richard K. P. Benninger
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
- Barbara Davis Center for Diabetes, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
- * E-mail:
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20
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Babiker T, Vedovato N, Patel K, Thomas N, Finn R, Männikkö R, Chakera AJ, Flanagan SE, Shepherd MH, Ellard S, Ashcroft FM, Hattersley AT. Successful transfer to sulfonylureas in KCNJ11 neonatal diabetes is determined by the mutation and duration of diabetes. Diabetologia 2016; 59:1162-6. [PMID: 27033559 PMCID: PMC4869695 DOI: 10.1007/s00125-016-3921-8] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 02/17/2016] [Indexed: 10/29/2022]
Abstract
AIMS/HYPOTHESIS The finding that patients with diabetes due to potassium channel mutations can transfer from insulin to sulfonylureas has revolutionised the management of patients with permanent neonatal diabetes. The extent to which the in vitro characteristics of the mutation can predict a successful transfer is not known. Our aim was to identify factors associated with successful transfer from insulin to sulfonylureas in patients with permanent neonatal diabetes due to mutations in KCNJ11 (which encodes the inwardly rectifying potassium channel Kir6.2). METHODS We retrospectively analysed clinical data on 127 patients with neonatal diabetes due to KCNJ11 mutations who attempted to transfer to sulfonylureas. We considered transfer successful when patients completely discontinued insulin whilst on sulfonylureas. All unsuccessful transfers received ≥0.8 mg kg(-1) day(-1) glibenclamide (or the equivalent) for >4 weeks. The in vitro response of mutant Kir6.2/SUR1 channels to tolbutamide was assessed in Xenopus oocytes. For some specific mutations, not all individuals carrying the mutation were able to transfer successfully; we therefore investigated which clinical features could predict a successful transfer. RESULTS In all, 112 out of 127 (88%) patients successfully transferred to sulfonylureas from insulin with an improvement in HbA1c from 8.2% (66 mmol/mol) on insulin, to 5.9% (41 mmol/mol) on sulphonylureas (p = 0.001). The in vitro response of the mutation to tolbutamide determined the likelihood of transfer: the extent of tolbutamide block was <63% for the p.C166Y, p.I296L, p.L164P or p.T293N mutations, and no patients with these mutations successfully transferred. However, most individuals with mutations for which tolbutamide block was >73% did transfer successfully. The few patients with these mutations who could not transfer had a longer duration of diabetes than those who transferred successfully (18.2 vs 3.4 years, p = 0.032). There was no difference in pre-transfer HbA1c (p = 0.87), weight-for-age z scores (SD score; p = 0.12) or sex (p = 0.17). CONCLUSIONS/INTERPRETATION Transfer from insulin is successful for most KCNJ11 patients and is best predicted by the in vitro response of the specific mutation and the duration of diabetes. Knowledge of the specific mutation and of diabetes duration can help predict whether successful transfer to sulfonylureas is likely. This result supports the early genetic testing and early treatment of patients with neonatal diabetes aged under 6 months.
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Affiliation(s)
- Tarig Babiker
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Natascia Vedovato
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Kashyap Patel
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Nicholas Thomas
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Roisin Finn
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Roope Männikkö
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
- UCL Institute of Neurology, MRC Centre for Neuromuscular Diseases, London, UK
| | - Ali J Chakera
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
- Department of Diabetes and Endocrinology, Royal Sussex County Hospital, Brighton and Sussex University Hospitals, Brighton, UK
| | - Sarah E Flanagan
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Maggie H Shepherd
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Sian Ellard
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Frances M Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK.
| | - Andrew T Hattersley
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK.
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK.
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21
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Kofent J, Spagnoli FM. Xenopus as a model system for studying pancreatic development and diabetes. Semin Cell Dev Biol 2016; 51:106-16. [PMID: 26806634 DOI: 10.1016/j.semcdb.2016.01.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 01/06/2016] [Indexed: 02/07/2023]
Abstract
Diabetes is a chronic disease caused by the loss or dysfunction of the insulin-producing β-cells in the pancreas. To date, much of our knowledge about β-cells in humans comes from studying rare monogenic forms of diabetes. Importantly, the majority of mutations so far associated to monogenic diabetes are in genes that exert a regulatory role in pancreatic development and/or β-cell function. Thus, the identification and study of novel mutations open an unprecedented window into human pancreatic development. In this review, we summarize major advances in the genetic dissection of different types of monogenic diabetes and the insights gained from a developmental perspective. We highlight future challenges to bridge the gap between the fast accumulation of genetic data through next-generation sequencing and the need of functional insights into disease mechanisms. Lastly, we discuss the relevance and advantages of studying candidate gene variants in vivo using the Xenopus as model system.
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Affiliation(s)
- Julia Kofent
- Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Str. 10, D-13125 Berlin, Germany
| | - Francesca M Spagnoli
- Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Str. 10, D-13125 Berlin, Germany.
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22
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Liu L, Nagashima K, Yasuda T, Liu Y, Hu HR, He G, Feng B, Zhao M, Zhuang L, Zheng T, Friedman TC, Xiang K. Mutations in KCNJ11 are associated with the development of autosomal dominant, early-onset type 2 diabetes. Diabetologia 2013; 56:2609-18. [PMID: 24018988 PMCID: PMC5333983 DOI: 10.1007/s00125-013-3031-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Accepted: 08/02/2013] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS More than 90% of Chinese familial early-onset type 2 diabetes mellitus is genetically unexplained. To investigate the molecular aetiology, we identified and characterised whether mutations in the KCNJ11 gene are responsible for these families. METHODS KCNJ11 mutations were screened for 96 familial early-onset type 2 diabetic probands and their families. Functional significance of the identified mutations was confirmed by physiological analysis, molecular modelling and population survey. RESULTS Three novel KCNJ11 mutations, R27H, R192H and S116F117del, were identified in three families with early-onset type 2 diabetes mellitus. Mutated KCNJ11 with R27H or R192H markedly reduced ATP sensitivity (E23K>R27H>C42R>R192H>R201H), but no ATP-sensitive potassium channel currents were detected in the loss-of-function S116F117del channel in vitro. Molecular modelling indicated that R192H had a larger effect on the channel ATP-binding pocket than R27H, which may qualitatively explain why the ATP sensitivity of the R192H mutation is seven times less than R27H. The shape of the S116F117del channel may be compressed, which may explain why the mutated channel had no currents. Discontinuation of insulin and implementation of sulfonylureas for R27H or R192H carriers and continuation/switch to insulin therapy for S116F117del carriers resulted in good glycaemic control. CONCLUSIONS/INTERPRETATION Our results suggest that genetic diagnosis for the KCNJ11 mutations in familial early-onset type 2 diabetes mellitus may help in understanding the molecular aetiology and in providing more personalised treatment for these specific forms of diabetes in Chinese and other Asian patients.
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Affiliation(s)
- Limei Liu
- Department of Endocrinology & Metabolism, Shanghai Jiaotong University Affiliated Sixth People's Hospital, Shanghai Diabetes Institute, 600 Yishan Road, Shanghai, 200233, China,
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23
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Fendler W, Pietrzak I, Brereton MF, Lahmann C, Gadzicki M, Bienkiewicz M, Drozdz I, Borowiec M, Malecki MT, Ashcroft FM, Mlynarski WM. Switching to sulphonylureas in children with iDEND syndrome caused by KCNJ11 mutations results in improved cerebellar perfusion. Diabetes Care 2013; 36:2311-6. [PMID: 23462667 PMCID: PMC3714477 DOI: 10.2337/dc12-2166] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Activating mutations in the KCNJ11 gene, encoding the Kir6.2 subunit of the KATP channel, result in permanent neonatal diabetes mellitus. They also may cause neurologic symptoms such as mental retardation and motor problems (iDEND syndrome) and epilepsy (DEND syndrome). Sulphonylurea (SU) treatment is reported to alleviate both the neurologic symptoms and diabetes in such cases. The study aimed to establish the magnitude and functional basis of the effect of SUs on the neurologic phenotype in children with iDEND using neuroimaging before and after insulin replacement with glibenclamide. RESEARCH DESIGN AND METHODS To localize and quantify the effect of glibenclamide administration, we performed single-photon emission computed tomography in seven patients with different mutations in KCNJ11. In five patients, measurements before and after initiation of SU treatment were performed. RESULTS Significant changes in single-photon emission computed tomography signal intensity after transfer to SU therapy were restricted to the cerebellum, consistent with previous data showing high Kir6.2 expression in this brain region. Cerebellar perfusion improved for both left (P = 0.006) and right (P = 0.01) hemispheres, with the mean improvement being 26.7 ± 7.1% (n = 5). No patients showed deterioration of cerebellar perfusion on SU therapy. Electrophysiological studies revealed a good correlation between the magnitude of KATP channel dysfunction and the clinical phenotype; mutant channels with the greatest reduction in adenosine 5'-triphosphate inhibition were associated with the most severe neurologic symptoms. CONCLUSIONS We conclude it is likely that at least some of the beneficial effects of SU treatment on neurodevelopment in iDEND patients result from improved cerebellar perfusion.
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Affiliation(s)
- Wojciech Fendler
- Department of Paediatrics, Oncology, Haematology, and Diabetology, Medical University of Lodz, Lodz, Poland.
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24
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Lin YW, Li A, Grasso V, Battaglia D, Crinò A, Colombo C, Barbetti F, Nichols CG. Functional characterization of a novel KCNJ11 in frame mutation-deletion associated with infancy-onset diabetes and a mild form of intermediate DEND: a battle between K(ATP) gain of channel activity and loss of channel expression. PLoS One 2013; 8:e63758. [PMID: 23667671 PMCID: PMC3646792 DOI: 10.1371/journal.pone.0063758] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 04/05/2013] [Indexed: 12/19/2022] Open
Abstract
ATP-sensitive potassium (KATP) channels are widely distributed in various tissues and cell types where they couple cell metabolism to cell excitability. Gain of channel function (GOF) mutations in the genes encoding Kir6.2 (KCNJ11) or the associated regulatory ssulfonylurea receptor 1 subunit (ABCC8), cause developmental delay, epilepsy and neonatal diabetes (DEND) due to suppressed cell excitability in pancreatic β-cells and neurons. The objective of this study was to determine the molecular basis of infancy-onset diabetes and a mild form of intermediate DEND, resulting from a novel KCNJ11 in frame mutation plus deletion. The naturally occurring Kir6.2 mutation plus deletion (Ser225Thr, Pro226_Pro232del) as well as the isolated S225T mutation or isolated del226–232 deletion were coexpressed with SUR1 in COS cells in homozygous or heterozygous states. The protein expression and gating effects of the resulting channels were assessed biochemically and electrophysiologically. For both the deletion and point mutations, simulated heterozygous expression resulted in overall increased conductance in intact cells in basal conditions and rightward shifted ATP dose-response curves in excised patches, due to increased intrinsic open probability. Interestingly, homomeric channels for the combined deletion/mutation, or for the deletion alone, showed dramatically reduced channel expression at the cell membrane, which would underlie a reduced function in vivo. These results demonstrate that both the mis-sense mutation and the deleted region in the Kir6.2 subunit are important for control of the intrinsic channel gating and suggest that the clinical presentation could be affected by the competition between loss-of-function by reduced trafficking and enhanced channel gating.
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Affiliation(s)
- Yu-Wen Lin
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Anlong Li
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Valeria Grasso
- Laboratory of Mendelian Diabetes, Bambino Gesù Children's Hospital, Research Institute, at University of Tor Vergata, Rome, Italy
| | - Domenica Battaglia
- Child Neurology Unit, Department of Pediatrics, Sacro Cuore Catholic University, Rome, Italy
| | - Antonino Crinò
- Autoimmune Endocrine Diseases Unit, Endocrinology Department, Bambino Gesù Children's Hospital, Research Institute, Palidoro, Rome, Italy
| | - Carlo Colombo
- Laboratory of Mendelian Diabetes, Bambino Gesù Children's Hospital, Research Institute, at University of Tor Vergata, Rome, Italy
| | - Fabrizio Barbetti
- Laboratory of Mendelian Diabetes, Bambino Gesù Children's Hospital, Research Institute, at University of Tor Vergata, Rome, Italy
- Department of Internal Medicine, University of Tor Vergata, Rome, Italy
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
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Detection of KCNJ11 gene mutations in a family with neonatal diabetes mellitus: implications for therapeutic management of family members with long-standing disease. Mol Diagn Ther 2012; 16:109-14. [PMID: 22471336 DOI: 10.1007/bf03256435] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
BACKGROUND Activating mutations of potassium inwardly-rectifying channel, subfamily J, member 11 (KCNJ11), which encodes Kir6.2 (beta-cell adenosine triphosphate-sensitive potassium [K(ATP)] channel subunit), have been associated with neonatal diabetes mellitus (NDM) in different studies. Treatment with oral sulfonylureas in place of exogenous insulin injections results in improved glycemic control in most patients carrying these mutations. Exploration of genetic causes of NDM occurring before the age of 6 months has been proposed as an important issue in identification of monogenic forms of diabetes, which might be critical in their therapeutic management, as a consequence. METHODS Mutation screening of the KCNJ11 gene was carried out using PCR amplification followed by direct sequencing in three family members: the proband, ND1, diagnosed at 40 days of age (current age 7 years); his sibling, ND2, diagnosed at 2 years of age (current age 14 years); and their father, ND3, diagnosed at 15 years of age (current age 35 years), who had been exclusively treated with insulin. The effect of the E227K mutation was also examined in a homology model of Kir6.2. RESULTS Our results revealed the presence of the heterozygous missense mutation c. 679 G/A (E227K) in all three patients, who were all able to successfully transfer from insulin injections to an oral sulfonylurea, with improved glycemic control. CONCLUSION We found that three members of a family with highly variable age of onset of insulin-treated diabetes, diagnosed at 40 days, 2 years, and 15 years of age, all carried the E227K mutation in KCNJ11 and could switch to an oral sulfonylurea. This mutation has been previously reported in patients with permanent and transient NDM, as well as later-onset diabetes; this report adds to the variability in phenotypic presentation and further supports genetic testing in all diabetic members of any family affected by NDM.
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Bonnefond A, Philippe J, Durand E, Dechaume A, Huyvaert M, Montagne L, Marre M, Balkau B, Fajardy I, Vambergue A, Vatin V, Delplanque J, Le Guilcher D, De Graeve F, Lecoeur C, Sand O, Vaxillaire M, Froguel P. Whole-exome sequencing and high throughput genotyping identified KCNJ11 as the thirteenth MODY gene. PLoS One 2012; 7:e37423. [PMID: 22701567 PMCID: PMC3372463 DOI: 10.1371/journal.pone.0037423] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 04/23/2012] [Indexed: 01/27/2023] Open
Abstract
Background Maturity-onset of the young (MODY) is a clinically heterogeneous form of diabetes characterized by an autosomal-dominant mode of inheritance, an onset before the age of 25 years, and a primary defect in the pancreatic beta-cell function. Approximately 30% of MODY families remain genetically unexplained (MODY-X). Here, we aimed to use whole-exome sequencing (WES) in a four-generation MODY-X family to identify a new susceptibility gene for MODY. Methodology WES (Agilent-SureSelect capture/Illumina-GAIIx sequencing) was performed in three affected and one non-affected relatives in the MODY-X family. We then performed a high-throughput multiplex genotyping (Illumina-GoldenGate assay) of the putative causal mutations in the whole family and in 406 controls. A linkage analysis was also carried out. Principal Findings By focusing on variants of interest (i.e. gains of stop codon, frameshift, non-synonymous and splice-site variants not reported in dbSNP130) present in the three affected relatives and not present in the control, we found 69 mutations. However, as WES was not uniform between samples, a total of 324 mutations had to be assessed in the whole family and in controls. Only one mutation (p.Glu227Lys in KCNJ11) co-segregated with diabetes in the family (with a LOD-score of 3.68). No KCNJ11 mutation was found in 25 other MODY-X unrelated subjects. Conclusions/Significance Beyond neonatal diabetes mellitus (NDM), KCNJ11 is also a MODY gene (‘MODY13’), confirming the wide spectrum of diabetes related phenotypes due to mutations in NDM genes (i.e. KCNJ11, ABCC8 and INS). Therefore, the molecular diagnosis of MODY should include KCNJ11 as affected carriers can be ideally treated with oral sulfonylureas.
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Affiliation(s)
- Amélie Bonnefond
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Julien Philippe
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Emmanuelle Durand
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Aurélie Dechaume
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Marlène Huyvaert
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Louise Montagne
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
- Department of Pediatrics, Saint Antoine Pediatric Hospital, Saint Vincent de Paul Hospital, Catholic University of Lille, Lille, France
| | - Michel Marre
- Department of Endocrinology, Diabetology and Nutrition, Bichat-Claude Bernard University Hospital, Assistance Publique des Hôpitaux de Paris (AP-HP), Paris, France
- Inserm-U695, Paris 7 University, Paris, France
| | - Beverley Balkau
- Inserm-U1018, Centre for research in Epidemiology and Population Health, Villejuif, France
- Paris-Sud 11 University, Villejuif, France
| | | | - Anne Vambergue
- Lille Nord de France University, Lille, France
- EA 4489 “Perinatal Environment and Fetal Growth”, Department of Diabetology, Huriez Hospital, CHRU Lille, Lille, France
| | - Vincent Vatin
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Jérôme Delplanque
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - David Le Guilcher
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Franck De Graeve
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Cécile Lecoeur
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Olivier Sand
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Martine Vaxillaire
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
| | - Philippe Froguel
- CNRS-UMR8199, Lille Pasteur Institute, Lille, France
- Lille Nord de France University, Lille, France
- Department of Genomics of Common Disease, School of Public Health, Imperial College London, Hammersmith Hospital, London, United Kingdom
- * E-mail:
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Männikkö R, Stansfeld PJ, Ashcroft AS, Hattersley AT, Sansom MSP, Ellard S, Ashcroft FM. A conserved tryptophan at the membrane-water interface acts as a gatekeeper for Kir6.2/SUR1 channels and causes neonatal diabetes when mutated. J Physiol 2011; 589:3071-83. [PMID: 21540348 PMCID: PMC3145925 DOI: 10.1113/jphysiol.2011.209700] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 04/26/2011] [Indexed: 12/20/2022] Open
Abstract
We identified a novel heterozygous mutation, W68R, in the Kir6.2 subunit of the ATP-sensitive potassium (KATP) channel, in a patient with transient neonatal diabetes. This tryptophan is absolutely conserved in mammalian Kir channels. The functional effects of mutations at residue 68 of Kir6.2 were studied by heterologous expression in Xenopus oocytes, and by homology modelling. We found the Kir6.2-W68R mutation causes a small reduction in ATP inhibition in the heterozygous state and an increase in the whole-cell KATP current. This can explain the clinical phenotype of the patient. The effect of the mutation was not charge or size dependent, the order of potency for ATP inhibition being W
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Affiliation(s)
- Roope Männikkö
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
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Lang V, Light PE. The molecular mechanisms and pharmacotherapy of ATP-sensitive potassium channel gene mutations underlying neonatal diabetes. Pharmgenomics Pers Med 2010; 3:145-61. [PMID: 23226049 PMCID: PMC3513215 DOI: 10.2147/pgpm.s6969] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Indexed: 12/14/2022] Open
Abstract
Neonatal diabetes mellitus (NDM) is a monogenic disorder caused by mutations in genes involved in regulation of insulin secretion from pancreatic β-cells. Mutations in the KCNJ11 and ABCC8 genes, encoding the adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channel Kir6.2 and SUR1 subunits, respectively, are found in ∼50% of NDM patients. In the pancreatic β-cell, K(ATP) channel activity couples glucose metabolism to insulin secretion via cellular excitability and mutations in either KCNJ11 or ABCC8 genes alter K(ATP) channel activity, leading to faulty insulin secretion. Inactivation mutations decrease K(ATP) channel activity and stimulate excessive insulin secretion, leading to hyperinsulinism of infancy. In direct contrast, activation mutations increase K(ATP) channel activity, resulting in impaired insulin secretion, NDM, and in severe cases, developmental delay and epilepsy. Many NDM patients with KCNJ11 and ABCC8 mutations can be successfully treated with sulfonylureas (SUs) that inhibit the K(ATP) channel, thus replacing the need for daily insulin injections. There is also strong evidence indicating that SU therapy ameliorates some of the neurological defects observed in patients with more severe forms of NDM. This review focuses on the molecular and cellular mechanisms of mutations in the K(ATP) channel that underlie NDM. SU pharmacogenomics is also discussed with respect to evaluating whether patients with certain K(ATP) channel activation mutations can be successfully switched to SU therapy.
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Affiliation(s)
- Veronica Lang
- Department of Pharmacology and Alberta Diabetes Institute, Faculty of Medicine and Dentistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Peter E Light
- Department of Pharmacology and Alberta Diabetes Institute, Faculty of Medicine and Dentistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta, Canada
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Kline CF, Hund TJ, Mohler PJ. Ankyrin regulates KATP channel membrane trafficking and gating in excitable cells. Channels (Austin) 2010; 4:55-7. [PMID: 19901534 DOI: 10.4161/chan.4.1.10362] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
K(ATP) channels play critical roles in many cellular functions by coupling cell metabolic status to electrical activity. First discovered in cardiomyocytes,(1) K(ATP) channels (comprised of Kir6.x and SUR subunits) have since been found in many other tissues, including pancreatic beta cells, skeletal muscle, smooth muscle, brain, pituitary and kidney. By linking cellular metabolic state with membrane potential, K(ATP) channels are able to regulate a number of cellular functions such as hormone secretion, vascular tone and excitability. Specifically, a reduction in metabolism causes a decrease in the ATP:ADP ratio, opening of K(ATP) channels, K(+) efflux, membrane hyperpolarization, and suppression of electrical activity. Conversely, increased cellular metabolism causes an increase in the ATP:ADP ratio that leads to closure of the K(ATP) channel, membrane depolarization, and stimulation of cell electrical activity.
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Affiliation(s)
- Crystal F Kline
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA
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30
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Clark R, Proks P. ATP-sensitive potassium channels in health and disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 654:165-92. [PMID: 20217498 DOI: 10.1007/978-90-481-3271-3_8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The ATP-sensitive potassium (K(ATP)) channel plays a crucial role in insulin secretion and thus glucose homeostasis. K(ATP) channel activity in the pancreatic beta-cell is finely balanced; increased activity prevents insulin secretion, whereas reduced activity stimulates insulin release. The beta-cell metabolism tightly regulates K(ATP) channel gating, and if this coupling is perturbed, two distinct disease states can result. Diabetes occurs when the K(ATP) channel fails to close in response to increased metabolism, whereas congenital hyperinsulinism results when K(ATP) channels remain closed even at very low blood glucose levels. In general there is a good correlation between the magnitude of K(ATP) current and disease severity. Mutations that cause a complete loss of K(ATP) channels in the beta-cell plasma membrane produce a severe form of congenital hyperinsulinism, whereas mutations that partially impair channel function produce a milder phenotype. Similarly mutations that greatly reduce the ATP sensitivity of the K(ATP) channel lead to a severe form of neonatal diabetes with associated neurological complications, whilst mutations that cause smaller shifts in ATP sensitivity cause neonatal diabetes alone. This chapter reviews our current understanding of the pancreatic beta-cell K(ATP) channel and highlights recent structural, functional and clinical advances.
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Affiliation(s)
- Rebecca Clark
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.
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Remedi MS, Koster JC. K(ATP) channelopathies in the pancreas. Pflugers Arch 2009; 460:307-20. [PMID: 19921246 DOI: 10.1007/s00424-009-0756-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 10/20/2009] [Accepted: 10/23/2009] [Indexed: 12/14/2022]
Abstract
Adenosine-triphosphate-sensitive potassium channels (KATP) are regulated by adenosine nucleotides, and, thereby, couple cellular metabolism with electrical activity in multiple tissues including the pancreatic beta-cell. The critical involvement of KATP in insulin secretion is confirmed by the demonstration that inactivating and activating mutations in KATP underlie persistent hyperinsulinemia and neonatal diabetes mellitus, respectively, in both animal models and humans. In addition, a common variant in KATP represents a risk factor in the etiology of type 2 diabetes. This review focuses on the mechanistic basis by which KATP mutations underlie insulin secretory disorders and the implications of these findings for successful clinical intervention.
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Affiliation(s)
- Maria S Remedi
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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32
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Craig TJ, Shimomura K, Holl RW, Flanagan SE, Ellard S, Ashcroft FM. An in-frame deletion in Kir6.2 (KCNJ11) causing neonatal diabetes reveals a site of interaction between Kir6.2 and SUR1. J Clin Endocrinol Metab 2009; 94:2551-7. [PMID: 19351728 PMCID: PMC7611921 DOI: 10.1210/jc.2009-0159] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
CONTEXT Activating mutations in genes encoding the Kir6.2 (KCNJ11) and SUR1 (ABCC8) subunits of the pancreatic ATP-sensitive K(+) channel are a common cause of permanent neonatal diabetes (PNDM). All Kir6.2 mutations identified to date are missense mutations. We describe here a novel in-frame deletion (residues 28-32) in Kir6.2 in a heterozygous patient with PNDM without neurological problems that are detectable by standard evaluation. OBJECTIVE The aim of the study was to identify the mutation responsible for neonatal diabetes in this patient and characterize its functional effects. DESIGN Wild-type and mutant Kir6.2/SUR1 channels were examined by heterologous expression in Xenopus oocytes. RESULTS The Kir6.2-28Delta32 mutation produced a significant decrease in ATP inhibition and an increase in whole-cell K(ATP) currents, explaining the diabetes of the patient. Tolbutamide block was only slightly reduced in the simulated heterozygous state, suggesting that the patient should respond to sulfonylurea therapy. The mutation decreased ATP inhibition indirectly, by increasing the intrinsic (unliganded) channel open probability. Neither effect was observed when Kir6.2 was expressed in the absence of SUR1, suggesting that the mutation impairs coupling between SUR1 and Kir6.2. Coimmunoprecipitation studies further revealed that the mutation disrupted a physical interaction between Kir6.2 and residues 1-288 (but not residues 1-196) of SUR1. CONCLUSIONS We report a novel KCNJ11 mutation causing PNDM. Our results show that residues 28-32 in the N terminus of Kir6.2 interact both physically and functionally with SUR1 and suggest that residues 196-288 of SUR1 are important in this interaction.
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MESH Headings
- ATP-Binding Cassette Transporters/metabolism
- Animals
- Binding Sites/genetics
- Diabetes Mellitus, Type 2/congenital
- Diabetes Mellitus, Type 2/genetics
- Diabetes Mellitus, Type 2/metabolism
- Gene Deletion
- Humans
- Infant
- Infant, Newborn
- Infant, Newborn, Diseases/genetics
- Male
- Models, Biological
- Open Reading Frames/genetics
- Potassium Channels, Inwardly Rectifying/chemistry
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Potassium Channels, Inwardly Rectifying/physiology
- Protein Binding/genetics
- Receptors, Drug/metabolism
- Sulfonylurea Receptors
- Xenopus
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Affiliation(s)
- Tim J Craig
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
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Shimomura K, Flanagan SE, Zadek B, Lethby M, Zubcevic L, Girard CAJ, Petz O, Mannikko R, Kapoor RR, Hussain K, Skae M, Clayton P, Hattersley A, Ellard S, Ashcroft FM. Adjacent mutations in the gating loop of Kir6.2 produce neonatal diabetes and hyperinsulinism. EMBO Mol Med 2009; 1:166-77. [PMID: 20049716 PMCID: PMC3378123 DOI: 10.1002/emmm.200900018] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2008] [Accepted: 03/11/2009] [Indexed: 01/10/2023] Open
Abstract
K(ATP) channels regulate insulin secretion from pancreatic beta-cells. Loss- and gain-of-function mutations in the genes encoding the Kir6.2 and SUR1 subunits of this channel cause hyperinsulinism of infancy and neonatal diabetes, respectively. We report two novel mutations in the gating loop of Kir6.2 which cause neonatal diabetes with developmental delay (T293N) and hyperinsulinism (T294M). These mutations increase (T293N) or decrease (T294M) whole-cell K(ATP) currents, accounting for the different clinical phenotypes. The T293N mutation increases the intrinsic channel open probability (Po((0))), thereby indirectly decreasing channel inhibition by ATP and increasing whole-cell currents. T294M channels exhibit a dramatically reduced Po((0)) in the homozygous but not in the pseudo-heterozygous state. Unlike wild-type channels, hetT294M channels were activated by MgADP in the absence but not in the presence of MgATP; however, they are activated by MgGDP in both the absence and presence of MgGTP. These mutations demonstrate the importance of the gating loop of Kir channels in regulating Po((0)) and further suggest that Mg-nucleotide interaction with SUR1 may reduce ATP inhibition at Kir6.2.
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Affiliation(s)
- Kenju Shimomura
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of OxfordUK
| | - Sarah E Flanagan
- Institute of Biomedical and Clinical Research, Peninsula Medical SchoolExeter, UK
| | - Brittany Zadek
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of OxfordUK
| | - Mark Lethby
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of OxfordUK
| | - Lejla Zubcevic
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of OxfordUK
| | - Christophe A J Girard
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of OxfordUK
| | - Oliver Petz
- St. Vincenz Hospital Coesfeld, Childrens HospitalGermany
| | - Roope Mannikko
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of OxfordUK
| | - Ritika R Kapoor
- London Centre for Paediatric Endocrinology and Metabolism, Great Ormond Street Hospital for Children NHS Trust and The Institute of Child Health, University College LondonUK
| | - Khalid Hussain
- London Centre for Paediatric Endocrinology and Metabolism, Great Ormond Street Hospital for Children NHS Trust and The Institute of Child Health, University College LondonUK
| | - Mars Skae
- Department of Endocrinology, Royal Manchester Children's Hospital, Central Manchester & Manchester Children's University Hospitals NHS TrustUK
| | - Peter Clayton
- Department of Endocrinology, Royal Manchester Children's Hospital, Central Manchester & Manchester Children's University Hospitals NHS TrustUK
| | - Andrew Hattersley
- Institute of Biomedical and Clinical Research, Peninsula Medical SchoolExeter, UK
| | - Sian Ellard
- Institute of Biomedical and Clinical Research, Peninsula Medical SchoolExeter, UK
| | - Frances M Ashcroft
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of OxfordUK
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Martín-Frías M, Colino E, Pérez de Nanclares G, Alonso M, Ros P, Barrio R. Glibenclamide treatment in relapsed transient neonatal diabetes as a result of a KCNJ11 activating mutation (N48D). Diabet Med 2009; 26:567-9. [PMID: 19646201 DOI: 10.1111/j.1464-5491.2009.02704.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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35
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Flanagan SE, Clauin S, Bellanné-Chantelot C, de Lonlay P, Harries LW, Gloyn AL, Ellard S. Update of mutations in the genes encoding the pancreatic beta-cell K(ATP) channel subunits Kir6.2 (KCNJ11) and sulfonylurea receptor 1 (ABCC8) in diabetes mellitus and hyperinsulinism. Hum Mutat 2009; 30:170-80. [PMID: 18767144 DOI: 10.1002/humu.20838] [Citation(s) in RCA: 191] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The beta-cell ATP-sensitive potassium (K(ATP)) channel is a key component of stimulus-secretion coupling in the pancreatic beta-cell. The channel couples metabolism to membrane electrical events bringing about insulin secretion. Given the critical role of this channel in glucose homeostasis it is therefore not surprising that mutations in the genes encoding for the two essential subunits of the channel can result in both hypo- and hyperglycemia. The channel consists of four subunits of the inwardly rectifying potassium channel Kir6.2 and four subunits of the sulfonylurea receptor 1 (SUR1). It has been known for some time that loss of function mutations in KCNJ11, which encodes for Kir6.2, and ABCC8, which encodes for SUR1, can cause oversecretion of insulin and result in hyperinsulinism of infancy, while activating mutations in KCNJ11 and ABCC8 have recently been described that result in the opposite phenotype of diabetes. This review focuses on reported mutations in both genes, the spectrum of phenotypes, and the implications for treatment on diagnosing patients with mutations in these genes.
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Affiliation(s)
- Sarah E Flanagan
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Exeter, United Kingdom
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Abstract
ATP-sensitive potassium (K(ATP)) channels play a key role in glucose-dependent insulin secretion in pancreatic beta-cells. Recently, activating mutations in beta-cell K(ATP) channels were found to be an important cause of neonatal diabetes. In some patients, these mutations may also affect K(ATP) channel function in muscles, nerves and brain which can result in a severe disease termed DEND syndrome (Developmental delay, Epilepsy and Neonatal Diabetes). This review focuses on mutations in the pore-forming K(ATP) channel subunit (Kir6.2) that cause neonatal diabetes and discusses recent advances in our understanding of clinical features of neonatal diabetes, its underlying molecular mechanisms and their impact on treatment.
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Affiliation(s)
- Kenju Shimomura
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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37
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Modeling K(ATP) channel gating and its regulation. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 99:7-19. [PMID: 18983870 DOI: 10.1016/j.pbiomolbio.2008.10.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
ATP-sensitive potassium (K(ATP)) channels couple cell metabolism to plasmalemmal potassium fluxes in a variety of cell types. The activity of these channels is primarily determined by intracellular adenosine nucleotides, which have both inhibitory and stimulatory effects. The role of K(ATP) channels has been studied most extensively in pancreatic beta-cells, where they link glucose metabolism to insulin secretion. Many mutations in K(ATP) channel subunits (Kir6.2, SUR1) have been identified that cause either neonatal diabetes or congenital hyperinsulinism. Thus, a mechanistic understanding of K(ATP) channel behavior is necessary for modeling beta-cell electrical activity and insulin release in both health and disease. Here, we review recent advances in the K(ATP) channel structure and function. We focus on the molecular mechanisms of K(ATP) channel gating by adenosine nucleotides, phospholipids and sulphonylureas and consider the advantages and limitations of various mathematical models of macroscopic and single-channel K(ATP) currents. Finally, we outline future directions for the development of more realistic models of K(ATP) channel gating.
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Støy J, Greeley SAW, Paz VP, Ye H, Pastore AN, Skowron KB, Lipton RB, Cogen FR, Bell GI, Philipson LH. Diagnosis and treatment of neonatal diabetes: a United States experience. Pediatr Diabetes 2008; 9:450-9. [PMID: 18662362 PMCID: PMC2574846 DOI: 10.1111/j.1399-5448.2008.00433.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND/OBJECTIVE Mutations in KCNJ11, ABCC8, or INS are the cause of permanent neonatal diabetes mellitus in about 50% of patients diagnosed with diabetes before 6 months of age and in a small fraction of those diagnosed between 6 and 12 months. The aim of this study was to identify the genetic cause of diabetes in 77 consecutive patients referred to the University of Chicago with diabetes diagnosed before 1 yr of age. METHODS We used Oragene DNA Self-Collection kit to obtain a saliva sample for DNA. We sequenced the protein-coding regions of KCNJ11, ABCC8, and INS using standard methods. RESULTS We enrolled 32 patients diagnosed with diabetes before 6 months of age and 45 patients diagnosed between 6 and 12 months. We identified a mutation in KCNJ11 in 14 patients from 12 families and in INS in 7 patients from 4 families. Three of the patients with an INS mutation were diagnosed with diabetes between 6 and 12 months of age. Finally, we found that two patients had an abnormality of chromosome 6q24 associated with transient neonatal diabetes mellitus. CONCLUSIONS We were able to establish a genetic cause of diabetes in 63% of patients diagnosed with diabetes before 6 months of age and in 7% of patients diagnosed between 6 and 12 months. Genetic testing, which is critical for guiding appropriate management, should be considered in patients diagnosed with diabetes before 1 yr of age, especially if they are autoantibody negative, although the presence of autoantibodies does not rule out a monogenic cause.
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Affiliation(s)
- Julie Støy
- Department of Medicine, The University of Chicago, Chicago, IL 60637, USA
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DEND mutation in Kir6.2 (KCNJ11) reveals a flexible N-terminal region critical for ATP-sensing of the KATP channel. Biophys J 2008; 95:4689-97. [PMID: 18708460 DOI: 10.1529/biophysj.108.138685] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
ATP-sensitive K(+)-channels link metabolism and excitability in neurons, myocytes, and pancreatic islets. Mutations in the pore-forming subunit (Kir6.2; KCNJ11) cause neonatal diabetes, developmental delay, and epilepsy by decreasing sensitivity to ATP inhibition and suppressing electrical activity. Mutations of residue G53 underlie both mild (G53R,S) and severe (G53D) forms of the disease. All examined substitutions (G53D,R,S,A,C,F) reduced ATP-sensitivity, indicating an intolerance of any amino acid other than glycine. Surprisingly, each mutation reduces ATP affinity, rather than intrinsic gating, although structural modeling places G53 at a significant distance from the ATP-binding pocket. We propose that glycine is required in this location for flexibility of the distal N-terminus, and for an induced fit of ATP at the binding site. Consistent with this hypothesis, glycine substitution of the adjacent residue (Q52G) partially rescues ATP affinity of reconstituted Q52G/G53D channels. The results reveal an important feature of the noncanonical ATP-sensing mechanism of K(ATP) channels.
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Orío Hernández M, de la Serna Martínez M, González Casado I, Lapunzina P, Gracia Bouthelier R. [Neonatal diabetes mellitus and KCNJ11 gene mutation: report of a family case]. An Pediatr (Barc) 2008; 68:602-4. [PMID: 18559200 DOI: 10.1157/13123293] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neonatal diabetes mellitus (NDM) is characterized by hyperglycemia within the first month of life and insulin dependence for at least two weeks. There are two types of NDM, transient (TNDM) and permanent (PNDM), which are genetically different. We report the case of two brothers who developed hyperglycemia without ketosis on the 18th day and 2 h of life, respectively. Thyroid function tests, abdominal ultrasound and karyotype where normal and there were no pancreatic antibodies. The first one required insulin therapy for the first 92 days of life and the second for 5 months. The mother developed gestational diabetes during both pregnancies and she was later diagnosed diabetes mellitus (without antibodies). They were studied for mutations in KCNJ11 gene (principally related to the permanent form). The three of them showed the E229K mutation (frequently associated with the transient form). A genetic study is essential in NDM to achieve the most accurate prognosis possible.
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Affiliation(s)
- M Orío Hernández
- Servicio de Endocrinología Pediátrica, Hospital Universitario Infantil La Paz, Madrid, España.
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41
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D'Amato E, Tammaro P, Craig TJ, Tosi A, Giorgetti R, Lorini R, Ashcroft FM. Variable phenotypic spectrum of diabetes mellitus in a family carrying a novel KCNJ11 gene mutation. Diabet Med 2008; 25:651-6. [PMID: 18544102 DOI: 10.1111/j.1464-5491.2008.02443.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIMS Heterozygous activating mutations in KCNJ11, which encodes the Kir6.2 subunit of the pancreatic ATP-sensitive potassium (K(ATP)) channel, cause both permanent and transient neonatal diabetes. Identification of KCNJ11 mutations has important therapeutic implications, as many patients can replace insulin injections with sulphonylurea tablets. The aim was to determine if a KCNJ11 mutation was responsible for a dominantly inherited form of diabetes mellitus, showing variability in age at diagnosis, in an Italian family. METHODS We sequenced KCNJ11 in members of a three-generation family with variable phenotypes of dominantly inherited diabetes mellitus. One had transient early-onset diabetes, one had impaired glucose tolerance during the second pregnancy, and two had young-onset diabetes. None of the subjects showed permanent neonatal diabetes or neurological symptoms. RESULTS A novel heterozygous mutation (c. 679C-->G and c. 680A-->T) was identified, resulting in a GAG-->CTG (E227L) substitution in KCNJ11. Functional studies of recombinant heterozygous K(ATP) channels revealed a small reduction in channel inhibition by ATP (IC(50) of 15 micromol/l and 38 micromol/l for wild-type and heterozygous channels, respectively) and an increase in the resting K(ATP) current. This would be expected to impair insulin secretion. The results are in agreement with the mild phenotype of the patients. CONCLUSIONS Our results broaden the spectrum of diabetes phenotypes resulting from KCNJ11 mutations. They indicate testing for KCNJ11 mutations should be considered not only for neonatal diabetes but also for other forms of dominantly inherited diabetes with later onset, especially where these are associated with a low body mass index and low birth weight.
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Affiliation(s)
- E D'Amato
- Department of Paediatrics, University of Genoa, IRCCS G. Gaslini, Largo Gaslini, Genoa, Italy.
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Abstract
An explosion of work over the last decade has produced insight into the multiple hereditary causes of a nonimmunological form of diabetes diagnosed most frequently within the first 6 months of life. These studies are providing increased understanding of genes involved in the entire chain of steps that control glucose homeostasis. Neonatal diabetes is now understood to arise from mutations in genes that play critical roles in the development of the pancreas, of beta-cell apoptosis and insulin processing, as well as the regulation of insulin release. For the basic researcher, this work is providing novel tools to explore fundamental molecular and cellular processes. For the clinician, these studies underscore the need to identify the genetic cause underlying each case. It is increasingly clear that the prognosis, therapeutic approach, and genetic counseling a physician provides must be tailored to a specific gene in order to provide the best medical care.
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Affiliation(s)
- Lydia Aguilar-Bryan
- Pacific Northwest Diabetes Research Institute, 720 Broadway, Seattle, Washington 98122, USA.
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Lin YW, Bushman JD, Yan FF, Haidar S, MacMullen C, Ganguly A, Stanley CA, Shyng SL. Destabilization of ATP-sensitive potassium channel activity by novel KCNJ11 mutations identified in congenital hyperinsulinism. J Biol Chem 2008; 283:9146-56. [PMID: 18250167 DOI: 10.1074/jbc.m708798200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The inwardly rectifying potassium channel Kir6.2 is the pore-forming subunit of the ATP-sensitive potassium (K(ATP)) channel, which controls insulin secretion by coupling glucose metabolism to membrane potential in beta-cells. Loss of channel function because of mutations in Kir6.2 or its associated regulatory subunit, sulfonylurea receptor 1, causes congenital hyperinsulinism (CHI), a neonatal disease characterized by persistent insulin secretion despite severe hypoglycemia. Here, we report a novel K(ATP) channel gating defect caused by CHI-associated Kir6.2 mutations at arginine 301 (to cysteine, glycine, histidine, or proline). These mutations in addition to reducing channel expression at the cell surface also cause rapid, spontaneous current decay, a gating defect we refer to as inactivation. Based on the crystal structures of Kir3.1 and KirBac1.1, Arg-301 interacts with several residues in the neighboring Kir6.2 subunit. Mutation of a subset of these residues also induces channel inactivation, suggesting that the disease mutations may cause inactivation by disrupting subunit-subunit interactions. To evaluate the effect of channel inactivation on beta-cell function, we expressed an alternative inactivation mutant R301A, which has equivalent surface expression efficiency as wild type channels, in the insulin-secreting cell line INS-1. Mutant expression resulted in more depolarized membrane potential and elevated insulin secretion at basal glucose concentration (3 mm) compared with cells expressing wild type channels, demonstrating that the inactivation gating defect itself is sufficient to cause loss of channel function and hyperinsulinism. Our studies suggest the importance of Kir6.2 subunit-subunit interactions in K(ATP) channel gating and function and reveal a novel gating defect underlying CHI.
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Affiliation(s)
- Yu-Wen Lin
- Center for Research on Occupational and Environmental Toxicology, Oregon Health and Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97239, USA
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Tarasov AI, Girard CA, Larkin B, Tammaro P, Flanagan SE, Ellard S, Ashcroft FM. Functional analysis of two Kir6.2 (KCNJ11) mutations, K170T and E322K, causing neonatal diabetes. Diabetes Obes Metab 2007; 9 Suppl 2:46-55. [PMID: 17919178 DOI: 10.1111/j.1463-1326.2007.00777.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Heterozygous activating mutations in Kir6.2 (KCNJ11), the pore-forming subunit of the adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channel, are a common cause of neonatal diabetes (ND). We assessed the functional effects of two Kir6.2 mutations associated with ND: K170T and E322K. K(ATP) channels were expressed in Xenopus oocytes, and the heterozygous state was simulated by coexpression of wild-type and mutant Kir6.2 with SUR1 (the beta cell type of sulphonylurea receptor (SUR)). Both mutations reduced the sensitivity of the K(ATP) channel to inhibition by MgATP and enhanced whole-cell K(ATP) currents. In pancreatic beta cells, such an increase in the K(ATP) current is expected to reduce insulin secretion and thereby cause diabetes. The E322K mutation was without effect when Kir6.2 was expressed in the absence of SUR1, suggesting that this residue impairs coupling to SUR1. This is consistent with its predicted location on the outer surface of the tetrameric Kir6.2 pore. The kinetics of K170T channel opening and closing were altered by the mutation, which may contribute to the lower ATP sensitivity. Neither mutation affected the sensitivity of the channel to inhibition by the sulphonylurea tolbutamide, suggesting that patients carrying these mutations may respond to these drugs.
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Affiliation(s)
- A I Tarasov
- University Laboratory of Physiology, Oxford University, Oxford, UK
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Ashcroft FM. The Walter B. Cannon Physiology in Perspective Lecture, 2007. ATP-sensitive K+ channels and disease: from molecule to malady. Am J Physiol Endocrinol Metab 2007; 293:E880-9. [PMID: 17652156 DOI: 10.1152/ajpendo.00348.2007] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
This essay is based on a lecture given to the American Physiological Society in honor of Walter B. Cannon, an advocate of homeostasis. It focuses on the role of the ATP-sensitive potassium K(+) (K(ATP)) channel in glucose homeostasis and, in particular, on its role in insulin secretion from pancreatic beta-cells. The beta-cell K(ATP) channel comprises pore-forming Kir6.2 and regulatory SUR1 subunits, and mutations in either type of subunit can result in too little or too much insulin release. Here, I review the latest information on the relationship between K(ATP) channel structure and function, and consider how mutations in the K(ATP) channel genes lead to neonatal diabetes or congenital hyperinsulinism.
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Affiliation(s)
- Frances M Ashcroft
- Henry Wellcome Centre for Gene Function, Dept. of Physiology, Anatomy and Genetics, Univ. of Oxford, Parks Road, Oxford OX1 3PT, UK.
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Smith AJ, Taneja TK, Mankouri J, Sivaprasadarao A. Molecular cell biology of KATPchannels: implications for neonatal diabetes. Expert Rev Mol Med 2007; 9:1-17. [PMID: 17666135 DOI: 10.1017/s1462399407000403] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractATP-sensitive potassium (KATP) channels play a key role in the regulation of insulin secretion by coupling glucose metabolism to the electrical activity of pancreatic β-cells. To generate an electric signal of suitable magnitude, the plasma membrane of the β-cell must contain an appropriate number of channels. An inadequate number of channels can lead to congenital hyperinsulinism, whereas an excess of channels can result in the opposite condition, neonatal diabetes. KATPchannels are made up of four subunits each of Kir6.2 and the sulphonylurea receptor (SUR1), encoded by the genesKCNJ11andABCC8, respectively. Following synthesis, the subunits must assemble into an octameric complex to be able to exit the endoplasmic reticulum and reach the plasma membrane. While this biosynthetic pathway ensures supply of channels to the cell surface, an opposite pathway, involving clathrin-mediated endocytosis, removes channels back into the cell. The balance between these two processes, perhaps in conjunction with endocytic recycling, would dictate the channel density at the cell membrane. In this review, we discuss the molecular signals that contribute to this balance, and how an imbalance could lead to a disease state such as neonatal diabetes.
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Affiliation(s)
- Andrew J Smith
- Institute of Membrane and Systems Biology, University of Leeds, Leeds, UK
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Rica I, Luzuriaga C, Pérez de Nanclares G, Estalella I, Aragonés A, Barrio R, Bilbao JR, Carlés C, Fernández C, Fernández JM, Fernández-Rebollo E, Gastaldo E, Giralt P, Gomez Vida JM, Gutiérrez A, López Siguero JP, Martínez-Aedo MJ, Muñoz M, Prieto J, Rodrigo J, Vargas F, Castano L. The majority of cases of neonatal diabetes in Spain can be explained by known genetic abnormalities. Diabet Med 2007; 24:707-13. [PMID: 17490422 DOI: 10.1111/j.1464-5491.2007.02140.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
BACKGROUND Neonatal diabetes is a rare disease characterized by hyperglycaemia within the first 3 months of life and requiring insulin treatment; it can either be transient (TNDM) or permanent (PNDM). Alterations at band 6q24 and heterozygous activating mutations in KCNJ11, the gene encoding the pore-forming subunit of the KATP channel, can cause neonatal diabetes. Aims We screened the 6q24 region, KCNJ11, GCK, FOXP3 and IPF1 genes for mutations in families with PNDM or TNDM to establish a phenotype-genotype correlation. METHODS Twenty-two patients with neonatal diabetes were recruited. Inclusion criteria were insulin-treated diabetes diagnosed within the first 3 months and insulin treatment for at least 15 days. Clinical data were recorded in a questionnaire. RESULTS We identified 17 genetic alterations in our patients: six alterations at the 6q24 band associated with TNDM and nine mutations in KCNJ11, five of which were novel. The analysis for a phenotype-genotype correlation showed that patients with 6q24 alterations had a lower birth weight and were diagnosed earlier than patients with KCNJ11 mutations. At follow-up of the TNDM patients with genetic alterations, 43% developed diabetes or impaired glucose tolerance in later life (one with 6q24 duplication and two with N48D and E227K mutations at KCNJ11 gene). Furthermore, half the first-degree relatives who carried a genetic alteration but who had not suffered from neonatal diabetes were diagnosed with diabetes or impaired glucose tolerance before the age of 30 years. CONCLUSIONS KCNJ11 mutations are common in both TNDM and PNDM and are associated with a higher birth weight compared with patients with 6q24 abnormalities. Patients with TNDM should be screened for abnormalities in glucose metabolism in adult life.
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Affiliation(s)
- I Rica
- Endocrinology and Diabetes Research Group, Hospital de Cruces, Barakaldo, Basque Country, Spain
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Flanagan SE, Patch AM, Mackay DJ, Edghill EL, Gloyn AL, Robinson D, Shield JP, Temple K, Ellard S, Hattersley AT. Mutations in ATP-sensitive K+ channel genes cause transient neonatal diabetes and permanent diabetes in childhood or adulthood. Diabetes 2007; 56:1930-7. [PMID: 17446535 PMCID: PMC7611811 DOI: 10.2337/db07-0043] [Citation(s) in RCA: 237] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Transient neonatal diabetes mellitus (TNDM) is diagnosed in the first 6 months of life, with remission in infancy or early childhood. For approximately 50% of patients, their diabetes will relapse in later life. The majority of cases result from anomalies of the imprinted region on chromosome 6q24, and 14 patients with ATP-sensitive K+ channel (K(ATP) channel) gene mutations have been reported. We determined the 6q24 status in 97 patients with TNDM. In patients in whom no abnormality was identified, the KCNJ11 gene and/or ABCC8 gene, which encode the Kir6.2 and SUR1 subunits of the pancreatic beta-cell K(ATP) channel, were sequenced. K(ATP) channel mutations were found in 25 of 97 (26%) TNDM probands (12 KCNJ11 and 13 ABCC8), while 69 of 97 (71%) had chromosome 6q24 abnormalities. The phenotype associated with KCNJ11 and ABCC8 mutations was similar but markedly different from 6q24 patients who had a lower birth weight and who were diagnosed and remitted earlier (all P < 0.001). K(ATP) channel mutations were identified in 26 additional family members, 17 of whom had diabetes. Of 42 diabetic patients, 91% diagnosed before 6 months remitted, but those diagnosed after 6 months had permanent diabetes (P < 0.0001). K(ATP) channel mutations account for 89% of patients with non-6q24 TNDM and result in a discrete clinical subtype that includes biphasic diabetes that can be treated with sulfonylureas. Remitting neonatal diabetes was observed in two of three mutation carriers, and permanent diabetes occurred after 6 months of age in subjects without an initial diagnosis of neonatal diabetes.
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Affiliation(s)
- Sarah E. Flanagan
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Exeter, UK
| | - Ann-Marie Patch
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Exeter, UK
| | - Deborah J.G. Mackay
- Wessex Regional Genetics Labs, Salisbury District Hospital, Salisbury, UK
- Division of Human Genetics, Southampton University, Southampton, UK
| | - Emma L. Edghill
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Exeter, UK
| | - Anna L. Gloyn
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Exeter, UK
- Diabetes Research Laboratories, Oxford Centre for Diabetes Endocrinology & Metabolism, University of Oxford, UK
| | - David Robinson
- Wessex Regional Genetics Labs, Salisbury District Hospital, Salisbury, UK
| | | | - Karen Temple
- Division of Human Genetics, Southampton University, Southampton, UK
- Wessex Clinical Genetics Service, NHS Trust, Southampton, UK
| | - Sian Ellard
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Exeter, UK
| | - Andrew T. Hattersley
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Exeter, UK
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