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Potassium channelopathies associated with epilepsy-related syndromes and directions for therapeutic intervention. Biochem Pharmacol 2023; 208:115413. [PMID: 36646291 DOI: 10.1016/j.bcp.2023.115413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023]
Abstract
A number of mutations to members of several CNS potassium (K) channel families have been identified which result in rare forms of neonatal onset epilepsy, or syndromes of which one prominent characteristic is a form of epilepsy. Benign Familial Neonatal Convulsions or Seizures (BFNC or BFNS), also referred to as Self-Limited Familial Neonatal Epilepsy (SeLNE), results from mutations in 2 members of the KV7 family (KCNQ) of K channels; while generally self-resolving by about 15 weeks of age, these mutations significantly increase the probability of generalized seizure disorders in the adult, in some cases they result in more severe developmental syndromes. Epilepsy of Infancy with Migrating Focal Seizures (EIMSF), or Migrating Partial Seizures of Infancy (MMPSI), is a rare severe form of epilepsy linked primarily to gain of function mutations in a member of the sodium-dependent K channel family, KCNT1 or SLACK. Finally, KCNMA1 channelopathies, including Liang-Wang syndrome (LIWAS), are rare combinations of neurological symptoms including seizure, movement abnormalities, delayed development and intellectual disabilities, with Liang-Wang syndrome an extremely serious polymalformative syndrome with a number of neurological sequelae including epilepsy. These are caused by mutations in the pore-forming subunit of the large-conductance calcium-activated K channel (BK channel) KCNMA1. The identification of these rare but significant channelopathies has resulted in a resurgence of interest in their treatment by direct pharmacological or genetic modulation. We will briefly review the genetics, biophysics and pharmacology of these K channels, their linkage with the 3 syndromes described above, and efforts to more effectively target these syndromes.
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Kaneko S, Yoshida S, Kanai K, Yasui-Furukori N, Iwasa H. Development of individualized medicine for epilepsy based on genetic information. Expert Rev Clin Pharmacol 2014; 1:661-81. [DOI: 10.1586/17512433.1.5.661] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Ferraro TN, Dlugos DJ, Buono RJ. Role of genetics in the diagnosis and treatment of epilepsy. Expert Rev Neurother 2014; 6:1789-800. [PMID: 17181426 DOI: 10.1586/14737175.6.12.1789] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Epilepsy is a heterogeneous group of multifactorial diseases, the vast majority determined by interactions between many genes and environmental factors; however, there are rare epilepsy syndromes that can be caused by a single gene mutation and are inherited according to classical mendelian genetic principles. Finding disease-causing genetic mutations in epilepsy has provided new opportunities for aiding diagnosis and developing therapies. Thus, the discovery of KCNQ2 mutations in benign familial neonatal convulsions, SCN1A mutations in severe myoclonic epilepsy of infancy and in generalized epilepsy with febrile seizures plus, and CHRA4 and CHRB2 mutations in autosomal-dominant nocturnal frontal lobe epilepsy, has led to the establishment of epilepsy as a disorder of ion channel function and, furthermore, has led to the introduction of genetic tests that are available clinically to aid in diagnosis and treatment. At the present time, clinical use of genetic testing in epilepsy is greatest in suspected cases of severe myoclonic epilepsy of infancy, generalized epilepsy with febrile seizures plus, atypical cases of benign familial neonatal convulsions and 'occult' cases of autosomal-dominant nocturnal frontal lobe epilepsy without a family history. Overall, clinical use is limited by the low number of documented disease-associated mutations and the uncertain clinical significance of many test results. Further elucidation of the relationship between gene mutations and channel function will add value to genetic testing in the future, as will better characterization of the association between gene mutations and clinical phenotypes.
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Affiliation(s)
- Thomas N Ferraro
- University of Pennsylvania, Department of Psychiatry, 125 S.31 Street, Room 2209 TRL, Philadelphia, PA 19104-3403, USA.
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Deng H, Xiu X, Song Z. The molecular biology of genetic-based epilepsies. Mol Neurobiol 2013; 49:352-67. [PMID: 23934645 DOI: 10.1007/s12035-013-8523-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2013] [Accepted: 07/24/2013] [Indexed: 01/02/2023]
Abstract
Epilepsy is one of the most common neurological disorders characterized by abnormal electrical activity in the central nervous system. The clinical features of this disorder are recurrent seizures, difference in age onset, type, and frequency, leading to motor, sensory, cognitive, psychic, or autonomic disturbances. Since the discovery of the first monogenic gene mutation in 1995, it is proposed that genetic factor plays an important role in the mechanism of epilepsy. Genes discovered in idiopathic epilepsies encode for ion channel or neurotransmitter receptor proteins, whereas syndromes with epilepsy as a main feature are caused by genes that are involved in functions such as cortical development, mitochondrial function, and cell metabolism. The identification of these monogenic epilepsy-causing genes provides new insight into the pathogenesis of epilepsies. Although most of the identified gene mutations present a monogenic inheritance, most of idiopathic epilepsies are complex genetic diseases exhibiting a polygenic or oligogenic inheritance. This article reviews recent genetic and molecular progresses in exploring the pathogenesis of epilepsy, with special emphasis on monogenic epilepsy-causing genes, including voltage-gated channels (Na(+), K(+), Ca(2+), Cl(-), and HCN), ligand-gated channels (nicotinic acetylcholine and GABAA receptors), non-ion channel genes as well as the mitochondrial DNA genes. These progresses have improved our understanding of the complex neurological disorder.
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Affiliation(s)
- Hao Deng
- Center for Experimental Medicine, the Third Xiangya Hospital, Central South University, Tongzipo Road 138, Changsha, Hunan, 410013, People's Republic of China,
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Lichter-Peled A, Polani S, Stanyon R, Rocchi M, Kahila Bar-Gal G. Role of KCNQ2 and KCNQ3 genes in juvenile idiopathic epilepsy in Arabian foals. Vet J 2013. [DOI: 10.1016/j.tvjl.2012.08.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Deconstructing the neural and ionic involvement of seizure-like events in the striatal network. Neurobiol Dis 2013; 52:128-36. [DOI: 10.1016/j.nbd.2012.11.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 11/28/2012] [Indexed: 02/07/2023] Open
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Blumkin L, Suls A, Deconinck T, De Jonghe P, Linder I, Kivity S, Dabby R, Leshinsky-Silver E, Lev D, Lerman-Sagie T. Neonatal seizures associated with a severe neonatal myoclonus like dyskinesia due to a familial KCNQ2 gene mutation. Eur J Paediatr Neurol 2012; 16:356-60. [PMID: 22169383 DOI: 10.1016/j.ejpn.2011.11.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 11/09/2011] [Accepted: 11/20/2011] [Indexed: 10/14/2022]
Abstract
UNLABELLED Mutations in the potassium channel gene KCNQ2, usually cause benign familial neonatal epilepsy. This is an autosomal dominant disorder characterized by clusters of seizures occurring in the first days of life. Most patients have normal psychomotor development and spontaneous remission of seizures by 12 months of age. Since Rett and Teubel reported the first family in 1964 and the identification of KCNQ2 gene mutations in this family by Zimprich et al. in 2006, phenotypic variability has been recognized including: later onset of seizures, myokymia in isolation or accompanied by seizures, neurological deficit and mental retardation. We report a mother and son with an atypical presentation of familial neonatal epilepsy. The mother has persistent epilepsy and subnormal intelligence. The son developed a severe dyskinesia clinically compatible with multifocal myoclonus in the neonatal period that only responded to carbamazepine. He also has ataxia and delayed psychomotor development. EMG revealed a spontaneous occurrence of repetitive normal motor potentials in different muscle groups. Genetic analysis identified a heterozygous missense mutation in KCNQ2 in the child and his mother. CONCLUSION KCNQ2 mutations can present with a neonatal onset multifocal myoclonus-like dyskinesia.
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Affiliation(s)
- Lubov Blumkin
- Pediatric Neurology Unit, Wolfson Medical Center, Holon, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
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Cooper EC. Made for "anchorin": Kv7.2/7.3 (KCNQ2/KCNQ3) channels and the modulation of neuronal excitability in vertebrate axons. Semin Cell Dev Biol 2011; 22:185-92. [PMID: 20940059 PMCID: PMC3070838 DOI: 10.1016/j.semcdb.2010.10.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 09/30/2010] [Accepted: 10/01/2010] [Indexed: 12/13/2022]
Abstract
Kv7.2 and Kv7.3 (encoded by KCNQ2 and KCNQ3) are homologous subunits forming a widely expressed neuronal voltage-gated K(+) (Kv) channel. Hypomorphic mutations in either KCNQ2 or KCNQ3 cause a highly penetrant, though transient, human phenotype-epilepsy during the first months of life. Some KCNQ2 mutations also cause involuntary muscle rippling, or myokymia, which is indicative of motoneuron axon hyperexcitability. Kv7.2 and Kv7.3 are concentrated at axonal initial segments (AISs), and at nodes of Ranvier in the central and peripheral nervous system. Kv7.2 and Kv7.3 share a novel ∼80 residue C-terminal domain bearing an "anchor" motif, which interacts with ankyrin-G and is required for channel AIS (and likely, nodal) localization. This domain includes the sequence IAEGES/TDTD, which is analogous (not homologous) to the ankyrin-G interaction motif of voltage-gated Na(+) (Na(V)) channels. The KCNQ subfamily is evolutionarily ancient, with two genes (KCNQ1 and KCNQ5) persisting as orthologues in extant bilaterian animals from worm to man. However, KCNQ2 and KCNQ3 arose much more recently, in the interval between the divergence of extant jawless and jawed vertebrates. This is precisely the interval during which myelin and saltatory conduction evolved. The natural selection for KCNQ2 and KCNQ3 appears to hinge on these subunits' unique ability to be coordinately localized with Na(V) channels by ankyrin-G, and the resulting enhancement in the reliability of neuronal excitability.
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Affiliation(s)
- Edward C Cooper
- Neurology and Neuroscience, Baylor College of Medicine, Houston, TX 77030, United States.
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Novel mutation in KCNQ2 causing benign familial neonatal seizures. Pediatr Neurol 2009; 41:367-70. [PMID: 19818940 DOI: 10.1016/j.pediatrneurol.2009.05.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 04/30/2009] [Accepted: 05/04/2009] [Indexed: 11/22/2022]
Abstract
Potassium channel subunits encoded by several genes of the KCNQ family underlie the M-current. Specifically, KCNQ2 and KCNQ3 play a major role at most neuronal sites. Mutations in KCNQ2 or KCNQ3 that reduce the M-current are responsible for benign familial neonatal seizures, a rare autosomal dominant idiopathic epilepsy of the newborn. The aim of this study was to investigate a single family with benign familial neonatal seizures for mutations in KCNQ genes and to analyze the association of mutation type with disease prognosis. A family in which members in several generations had signs and symptoms compatible with a diagnosis of benign familial neonatal seizures had DNA testing with single-stranded conformation polymorphism analysis for various mutations known to cause benign familial neonatal seizures. A novel KCNQ2 mutation c.63-66delGGTG (p.K21fsX40), causing a framework shift and early chain termination, was identified in the affected family members. In all cases, there was complete remission of the seizures after the neonatal period. This KCNQ2 mutation has implications for diagnosis and prognosis of familial neonatal seizures. Its presence suggests a benign disease with good prognosis and its identification can spare patients and physicians the need for extensive investigations or prolonged therapy.
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Seeman MV. Mechanisms of sex difference: a historical perspective. J Womens Health (Larchmt) 2009; 18:861-6. [PMID: 19514828 DOI: 10.1089/jwh.2008.1208] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVE The history of the discovery of mechanisms contributing to sex difference helps to better appreciate gender factors in a variety of disease states. The objective of this article is to illustrate four mechanisms of sex differences in disease incidence: X-linkage (including inactivation, escape from inactivating, skewed inactivation), sex-specific exposure to disease-producing pathogens, fetal microchimerism, and iron depletion. METHODS This is a historic review. RESULTS An emphasis on sex difference led to the uncovering of four different mechanisms by which illness rates differ in men and women. CONCLUSIONS Research into many disease states can benefit from a focus on potential mechanisms that yield sex differences in illness susceptibility, progression, and outcome.
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Affiliation(s)
- Mary V Seeman
- Centre for Addiction and Mental Health, Psychiatry, 250 College Street, Toronto, Ontario M5T 1R8, Canada.
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Lee IC, Chen JY, Chen YJ, Yu JS, Su PH. Benign familial neonatal convulsions: novel mutation in a newborn. Pediatr Neurol 2009; 40:387-91. [PMID: 19380078 DOI: 10.1016/j.pediatrneurol.2008.12.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 11/26/2008] [Accepted: 12/01/2008] [Indexed: 10/20/2022]
Abstract
Benign familial neonatal convulsions are a rare, autosomal-dominant form of neonatal epileptic syndrome. It can occur 1 week after birth, and usually involves frequent episodes, but with a benign course. The diagnosis depends on family history and clinical features. The mutant gene locates at 20q13, a voltage-gated potassium-channel gene (KCNQ2). Our patient exhibited an uneventful delivery course and onset of seizures at age 2 days. The general tonic seizures were unique and asymmetric, with frequencies of >20 per day. Results of examinations were within normal limits, including biochemistry and brain magnetic resonance imaging. Abnormalities included a small ventricular septum defect on cardiac sonography unrelated to the seizures, and nonspecific, multiple, high-voltage sharp waves and spike waves occurring infrequently in the central region on electroencephalogram. After phenobarbital and phenytoin use, the seizures persisted. On day 12, another antiepileptic drug, vigabatrin (unavailable in the United States), was used, and seizures decreased. A novel mutation of KCNQ2 was identified from a blood sample. The baby had occasional seizures with drug treatment at age 3 months. Benign familial neonatal convulsion should be considered in a baby with a unique seizure pattern and positive family history. Genetic counseling and diagnosis are mandatory.
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Affiliation(s)
- Inn-Chi Lee
- Division of Pediatric Neurology, Department of Pediatrics, College of Medicine, Chung-Shan Medical University Hospital, Institute of Medicine of Chung-Shan Medical University, Taichung, Taiwan
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Raol YH, Lapides DA, Keating JG, Brooks-Kayal AR, Cooper EC. A KCNQ channel opener for experimental neonatal seizures and status epilepticus. Ann Neurol 2009; 65:326-36. [PMID: 19334075 DOI: 10.1002/ana.21593] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Neonatal seizures occur frequently, are often refractory to anticonvulsants, and are associated with considerable morbidity and mortality. Genetic and electrophysiological evidence indicates that KCNQ voltage-gated potassium channels are critical regulators of neonatal brain excitability. This study tests the hypothesis that selective openers of KCNQ channels may be effective for treatment of neonatal seizures. METHODS We induced seizures in postnatal day 10 rats with either kainic acid or flurothyl. We measured seizure activity using quantified behavioral rating and electrocorticography. We compared the efficacy of flupirtine, a selective KCNQ channel opener, with phenobarbital and diazepam, two drugs in current use for neonatal seizures. RESULTS Unlike phenobarbital or diazepam, flupirtine prevented animals from experiencing development of status epilepticus when administered before kainate. In the flurothyl model, phenobarbital and diazepam increased latency to seizure onset, but flupirtine completely prevented seizures throughout the experiment. Flupirtine was also effective in arresting electrographic and behavioral seizures when administered after animals had developed continuous kainate-induced status epilepticus. Flupirtine caused dose-related sedation and suppressed electroencephalographic activity but did not result in respiratory suppression or result in any mortality. INTERPRETATION Flupirtine appears more effective than either of two commonly used antiepileptic drugs, phenobarbital and diazepam, in preventing and suppressing seizures in both the kainic acid and flurothyl models of symptomatic neonatal seizures. KCNQ channel openers merit further study as potential treatments for seizures in infants and children.
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Affiliation(s)
- Yogendrasinh H Raol
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
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Cortical hyperexcitability and epileptogenesis: Understanding the mechanisms of epilepsy – Part 1. J Clin Neurosci 2009; 16:355-65. [DOI: 10.1016/j.jocn.2008.08.026] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Accepted: 08/12/2008] [Indexed: 11/22/2022]
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Ronen GM, Meaney B, Dan B, Zimprich F, Stögmann W, Neugebauer W. From eugenic euthanasia to habilitation of "disabled'' children: Andreas Rett's contribution. J Child Neurol 2009; 24:115-27. [PMID: 19168827 DOI: 10.1177/0883073808321763] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Although the name of Andreas Rett is familiar to many from his eponymous neurogenetic syndrome, his other achievements involving the care of disabled children deserve special attention. His tireless advocacy helped to bring fundamental changes in the medical and societal attitude toward disabled individuals in a city that had recently seen more than 7500 disabled children and inmates of psychiatric hospitals actively euthanized by National Socialist (Nazi) decree. Most notably, this study demonstrates the remarkable changes that can be achieved single-handedly by a vocal and energetic physician. Yet at the same time, several instances are recorded in which Rett appeared to prioritize his own professional advancement at the expense of truthful disclosure of his own past, as well as that of some of his close associates. Dr Rett's professional life and contributions, now 10 years after his death, presents a compelling object lesson for neurologists and others involved in the care of the disabled.
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Affiliation(s)
- Gabriel M Ronen
- Department of Pediatrics, Faculty of Health Sciences, McMaster University, Ontario, Canada.
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Heron SE, Scheffer IE, Berkovic SF, Dibbens LM, Mulley JC. Channelopathies in idiopathic epilepsy. Neurotherapeutics 2007; 4:295-304. [PMID: 17395140 DOI: 10.1016/j.nurt.2007.01.009] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Approximately 70% of all patients with epilepsy lack an obvious extraneous cause and are presumed to have a predominantly genetic basis. Both familial and de novo mutations in neuronal voltage-gated and ligand-gated ion channel subunit genes have been identified in autosomal dominant epilepsies. However, patients with dominant familial mutations are rare and the majority of idiopathic epilepsy is likely to be the result of polygenic susceptibility alleles (complex epilepsy). Data on the identity of the genes involved in complex epilepsy is currently sparse but again points to neuronal ion channels. The number of genes and gene families associated with epilepsy is rapidly increasing and this increase is likely to escalate over the coming years with advances in mutation detection technologies. The genetic heterogeneity underlying idiopathic epilepsy presents challenges for the rational selection of therapies targeting particular ion channels. Too little is currently known about the genetic architecture of the epilepsies, and genetic testing for the known epilepsy genes remains costly. Pharmacogenetic studies have yet to explain why 30% of patients do not respond to the usual antiepileptic drugs. Despite this, the recognition that the idiopathic epilepsies are a group of channelopathies has, to a limited extent, explained the therapeutic action of the common antiepileptic drugs and has assisted clinical diagnosis of some epilepsy syndromes.
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Affiliation(s)
- Sarah E Heron
- Department of Genetic Medicine, Women's and Children's Hospital, North Adelaide, South Australia 5006.
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