Publications by authors named "Sarah E Heron"

42 Publications

Integrated in silico and experimental assessment of disease relevance of PCDH19 missense variants.

Hum Mutat 2021 Aug 15;42(8):1030-1041. Epub 2021 Jun 15.

Neurogenetics, Adelaide Medical School, The University of Adelaide, Adelaide, South Australia, Australia.

PCDH19 is a nonclustered protocadherin molecule involved in axon bundling, synapse function, and transcriptional coregulation. Pathogenic variants in PCDH19 cause infantile-onset epilepsy known as PCDH19-clustering epilepsy or PCDH19-CE. Recent advances in DNA-sequencing technologies have led to a significant increase in the number of reported PCDH19-CE variants, many of uncertain significance. We aimed to determine the best approaches for assessing the disease relevance of missense variants in PCDH19. The application of the American College of Medical Genetics and Association for Molecular Pathology (ACMG-AMP) guidelines was only 50% accurate. Using a training set of 322 known benign or pathogenic missense variants, we identified MutPred2, MutationAssessor, and GPP as the best performing in silico tools. We generated a protein structural model of the extracellular domain and assessed 24 missense variants. We also assessed 24 variants using an in vitro reporter assay. A combination of these tools was 93% accurate in assessing known pathogenic and benign PCDH19 variants. We increased the accuracy of the ACMG-AMP classification of 45 PCDH19 variants from 50% to 94%, using these tools. In summary, we have developed a robust toolbox for the assessment of PCDH19 variant pathogenicity to improve the accuracy of PCDH19-CE variant classification.
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http://dx.doi.org/10.1002/humu.24237DOI Listing
August 2021

Association of Missense Variants With Genetic Epilepsy With Febrile Seizures Plus.

Neurology 2021 05 23;96(18):e2251-e2260. Epub 2021 Mar 23.

From the Adelaide Medical School, Faculty of Health and Medical Sciences (S.E.H., A.E.G., M.A.C., J.G.), and Robinson Research Institute (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (B.M.R., R.V.H., M.C., B.E.G., M.F.B., S.P., M.S.H., I.E.S., S.F.B.), Austin Health, University of Melbourne, Heidelberg; Population Health and Immunity Division (M.F.B., M.B.), The Walter and Eliza Hall Institute of Medical Research; Department of Medical Biology (M.F.B., M.B.), University of Melbourne, Parkville, Australia; Division of Neurology (K.L.H.), Children's Hospital of Philadelphia; Department of Neurology (M.R.S.), Thomas Jefferson University, Philadelphia, PA; Department of Neurology (S.H.), Montefiore Medical Center, Albert Einstein College of Medicine, New York, NY; Institute of Neurology and Neurosurgery at Saint Barnabas (E.B.G.), Livingston, NJ; Department of Neurology (P.W.-W.), Beaumont Hospital, Dublin, Ireland; Royal Brisbane and Women's Hospital (J.T.P.), Brisbane, Australia; Centre for Genomics Research (S.P.), Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, Cambridge, UK; Institute for Genomic Medicine (E.L.H.), Columbia University Medical Center, New York, NY; Murdoch Children's Research Institute (M.S.H., I.E.S.), Parkville; Department of Paediatrics (I.E.S.), Royal Children's Hospital, University of Melbourne; Florey Institute of Neuroscience and Mental Health (I.E.S.), Melbourne; and Healthy Mothers, Babies and Children (J.G.), South Australian Health and Medical Research Institute, Adelaide, Australia.

Objective: To identify the causative gene in a large unsolved family with genetic epilepsy with febrile seizures plus (GEFS+), we sequenced the genomes of family members, and then determined the contribution of the identified gene to the pathogenicity of epilepsies by examining sequencing data from 2,772 additional patients.

Methods: We performed whole genome sequencing of 3 members of a GEFS+ family. Subsequently, whole exome sequencing data from 1,165 patients with epilepsy from the Epi4K dataset and 1,329 Australian patients with epilepsy from the Epi25 dataset were interrogated. Targeted resequencing was performed on 278 patients with febrile seizures or GEFS+ phenotypes. Variants were validated and familial segregation examined by Sanger sequencing.

Results: Eight previously unreported missense variants were identified in , coding for the vesicular inhibitory amino acid cotransporter VGAT. Two variants cosegregated with the phenotype in 2 large GEFS+ families containing 8 and 10 affected individuals, respectively. Six further variants were identified in smaller families with GEFS+ or idiopathic generalized epilepsy (IGE).

Conclusion: Missense variants in cause GEFS+ and IGE. These variants are predicted to alter γ-aminobutyric acid (GABA) transport into synaptic vesicles, leading to altered neuronal inhibition. Examination of further epilepsy cohorts will determine the full genotype-phenotype spectrum associated with variants.
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http://dx.doi.org/10.1212/WNL.0000000000011855DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8166436PMC
May 2021

BRAT1-associated neurodegeneration: Intra-familial phenotypic differences in siblings.

Am J Med Genet A 2016 11 2;170(11):3033-3038. Epub 2016 Aug 2.

Epilepsy Research Program, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia, Australia.

Recessive mutations in BRAT1 cause lethal neonatal rigidity and multifocal seizure syndrome, a phenotype characterized by neonatal microcephaly, hypertonia, and refractory epilepsy with premature death by age 2 years. Recently, attenuated disease variants have been described, suggesting that a wider clinical spectrum of BRAT1-associated neurodegeneration exists than was previously thought. Here, we report two affected siblings with compound heterozygous truncating mutations in BRAT1 and intra-familial phenotypic heterogeneity, with a less severe disease course in the female sibling. This phenotypic variability should be taken into account when treating patients with BRAT1-associated neurodegenerative disease. Mildly affected individuals with BRAT1 mutations show that BRAT1 must be considered as a cause in childhood refractory epilepsy and microcephaly with survival beyond infancy. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.a.37853DOI Listing
November 2016

Reply.

Ann Neurol 2016 07 10;80(1):168-9. Epub 2016 May 10.

Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.

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http://dx.doi.org/10.1002/ana.24669DOI Listing
July 2016

Multiplex families with epilepsy: Success of clinical and molecular genetic characterization.

Neurology 2016 Feb 22;86(8):713-22. Epub 2016 Jan 22.

From the Sackler School of Medicine (Z.A., I.B., M.Y.N., T.L.-S., A.D.K.), Tel Aviv University, Ramat Aviv, Israel; Epilepsy Research Centre (K.L.O., K.L.H., I.E.S., S.F.B.), University of Melbourne, Austin Health, Heidelberg, Australia; Epilepsy Unit (S.K., H.G.-S., R.S.), Schneider Children's Medical Center of Israel, Petach Tikvah; Department of Neurology (A.M., M.Y.N.), Tel Aviv Sourasky Medical Center; Department of Neurology (I.B.), The Chaim Sheba Medical Center, Tel Hashomer; Shaare Zedek Medical Center (A.J.M.), Jerusalem; Department of Neurology (S.W.), Western Galilee Hospital, Nahariya; Pediatric Neurology and Child Development Center (M. Mahajnah), Hillel Yaffe Medical Center, Hadera; Ruth and Bruce Rappaport Faculty of Medicine (M. Mahajnah), Technion, Haifa; Pediatric Neurology Unit (T.L.-S.), Wolfson Medical Center, Holon; The Edmond and Lily Safra Children's Hospital (B.B.-Z.), Sheba Medical Center, Ramat Gan; Department of Neurology (E.K.), Barzilai Medical Center, Ashkelon; Faculty of Health Sciences (E.K., R.M., Z.S.), Ben-Gurion University of the Negev, Beer-Sheva; Department of Neurology (R.M.) and Pediatric Neurology Unit (Z.S.), Soroka University Medical Center, Beer-Sheva; Pediatric Neurology Unit (U.K.), Dana Children's Hospital, Tel Aviv; Department of Neurology (D.E.), Agnes Ginges Center of Neurogenetics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; School of Biomedical Sciences (R.H.W.), Charles Sturt University, NSW; Queensland Brain Institute (M. Mangelsdorf), University of Queensland, Brisbane, Australia; Wessex Regional Genetics Laboratory (J.N.M.), Salisbury NHS Foundation Trust, Salisbury, UK; Division of Genetic Medicine (G.L.C., H.C.M.), Department of Pediatrics, University of Washington, Seattle; Florey Institute (G.D.J., I.E.S.), Melbourne; Department of Pediatrics (I.E.S.), University of Melbourne, Royal Children's Hospital; Population Health and Immunity Division (M.B.), The Walter and Eliza Hall Institute o

Objective: To analyze the clinical syndromes and inheritance patterns of multiplex families with epilepsy toward the ultimate aim of uncovering the underlying molecular genetic basis.

Methods: Following the referral of families with 2 or more relatives with epilepsy, individuals were classified into epilepsy syndromes. Families were classified into syndromes where at least 2 family members had a specific diagnosis. Pedigrees were analyzed and molecular genetic studies were performed as appropriate.

Results: A total of 211 families were ascertained over an 11-year period in Israel. A total of 169 were classified into broad familial epilepsy syndrome groups: 61 generalized, 22 focal, 24 febrile seizure syndromes, 33 special syndromes, and 29 mixed. A total of 42 families remained unclassified. Pathogenic variants were identified in 49/211 families (23%). The majority were found in established epilepsy genes (e.g., SCN1A, KCNQ2, CSTB), but in 11 families, this cohort contributed to the initial discovery (e.g., KCNT1, PCDH19, TBC1D24). We expand the phenotypic spectrum of established epilepsy genes by reporting a familial LAMC3 homozygous variant, where the predominant phenotype was epilepsy with myoclonic-atonic seizures, and a pathogenic SCN1A variant in a family where in 5 siblings the phenotype was broadly consistent with Dravet syndrome, a disorder that usually occurs sporadically.

Conclusion: A total of 80% of families were successfully classified, with pathogenic variants identified in 23%. The successful characterization of familial electroclinical and inheritance patterns has highlighted the value of studying multiplex families and their contribution towards uncovering the genetic basis of the epilepsies.
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http://dx.doi.org/10.1212/WNL.0000000000002404DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763801PMC
February 2016

KCNT1 mutations in seizure disorders: the phenotypic spectrum and functional effects.

J Med Genet 2016 Apr 6;53(4):217-25. Epub 2016 Jan 6.

Epilepsy Research Group, School of Pharmacy and Medical Sciences, Sansom Institute for Health Research and Centre for Cancer Biology, University of South Australia, Adelaide, South Australia, Australia.

Mutations in the sodium-gated potassium channel subunit gene KCNT1 have recently emerged as a cause of several different epileptic disorders. This review describes the mutational and phenotypic spectrum associated with the gene and discusses the comorbidities found in patients, which include intellectual disability and psychiatric features. The gene may also be linked with cardiac disorders. KCNT1 missense mutations have been found in 39% of patients with the epileptic encephalopathy malignant migrating focal seizures of infancy (MMFSI), making it the most significant MMFSI disease-causing gene identified to date. Mutations in KCNT1 have also been described in eight unrelated cases of sporadic and familial autosomal-dominant nocturnal frontal lobe epilepsy (ADNFLE). These patients have a high frequency of associated intellectual disability and psychiatric features. Two mutations in KCNT1 have been associated with both ADNFLE and MMFSI, suggesting that the genotype-phenotype relationship for KCNT1 mutations is not straightforward. Mutations have also been described in several patients with infantile epileptic encephalopathies other than MMFSI. Notably, all mutations in KCNT1 described to date are missense mutations, and electrophysiological studies have shown that they result in increased potassium current. Together, these genetic and electrophysiological studies raise the possibility of delivering precision medicine by treating patients with KCNT1 mutations using drugs that alter the action of potassium channels to specifically target the biological effects of their disease-causing mutation. Such trials are now in progress. Better understanding of the mechanisms underlying KCNT1-related disease will produce further improvements in treatment of the associated severe seizure disorders.
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http://dx.doi.org/10.1136/jmedgenet-2015-103508DOI Listing
April 2016

Benign infantile seizures and paroxysmal dyskinesia caused by an SCN8A mutation.

Ann Neurol 2016 Mar 13;79(3):428-36. Epub 2016 Feb 13.

Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.

Objective: Benign familial infantile seizures (BFIS), paroxysmal kinesigenic dyskinesia (PKD), and their combination-known as infantile convulsions and paroxysmal choreoathetosis (ICCA)-are related autosomal dominant diseases. PRRT2 (proline-rich transmembrane protein 2 gene) has been identified as the major gene in all 3 conditions, found to be mutated in 80 to 90% of familial and 30 to 35% of sporadic cases.

Methods: We searched for the genetic defect in PRRT2-negative, unrelated families with BFIS or ICCA using whole exome or targeted gene panel sequencing, and performed a detailed cliniconeurophysiological workup.

Results: In 3 families with a total of 16 affected members, we identified the same, cosegregating heterozygous missense mutation (c.4447G>A; p.E1483K) in SCN8A, encoding a voltage-gated sodium channel. A founder effect was excluded by linkage analysis. All individuals except 1 had normal cognitive and motor milestones, neuroimaging, and interictal neurological status. Fifteen affected members presented with afebrile focal or generalized tonic-clonic seizures during the first to second year of life; 5 of them experienced single unprovoked seizures later on. One patient had seizures only at school age. All patients stayed otherwise seizure-free, most without medication. Interictal electroencephalogram (EEG) was normal in all cases but 2. Five of 16 patients developed additional brief paroxysmal episodes in puberty, either dystonic/dyskinetic or "shivering" attacks, triggered by stretching, motor initiation, or emotional stimuli. In 1 case, we recorded typical PKD spells by video-EEG-polygraphy, documenting a cortical involvement.

Interpretation: Our study establishes SCN8A as a novel gene in which a recurrent mutation causes BFIS/ICCA, expanding the clinical-genetic spectrum of combined epileptic and dyskinetic syndromes.
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http://dx.doi.org/10.1002/ana.24580DOI Listing
March 2016

Mutations in the mammalian target of rapamycin pathway regulators NPRL2 and NPRL3 cause focal epilepsy.

Ann Neurol 2016 Jan 12;79(1):120-31. Epub 2015 Dec 12.

Epilepsy Research Program, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia, Australia.

Objective: Focal epilepsies are the most common form observed and have not generally been considered to be genetic in origin. Recently, we identified mutations in DEPDC5 as a cause of familial focal epilepsy. In this study, we investigated whether mutations in the mammalian target of rapamycin (mTOR) regulators, NPRL2 and NPRL3, also contribute to cases of focal epilepsy.

Methods: We used targeted capture and next-generation sequencing to analyze 404 unrelated probands with focal epilepsy. We performed exome sequencing on two families with multiple members affected with focal epilepsy and linkage analysis on one of these.

Results: In our cohort of 404 unrelated focal epilepsy patients, we identified five mutations in NPRL2 and five in NPRL3. Exome sequencing analysis of two families with focal epilepsy identified NPRL2 and NPRL3 as the top candidate-causative genes. Some patients had focal epilepsy associated with brain malformations. We also identified 18 new mutations in DEPDC5.

Interpretation: We have identified NPRL2 and NPRL3 as two new focal epilepsy genes that also play a role in the mTOR-signaling pathway. Our findings show that mutations in GATOR1 complex genes are the most significant cause of familial focal epilepsy identified to date, including cases with brain malformations. It is possible that deregulation of cellular growth control plays a more important role in epilepsy than is currently recognized.
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http://dx.doi.org/10.1002/ana.24547DOI Listing
January 2016

Mutations in KCNT1 cause a spectrum of focal epilepsies.

Epilepsia 2015 Sep 30;56(9):e114-20. Epub 2015 Jun 30.

Department of Pediatrics, Aarhus University Hospital, Aarhus, Denmark.

Autosomal dominant mutations in the sodium-gated potassium channel subunit gene KCNT1 have been associated with two distinct seizure syndromes, nocturnal frontal lobe epilepsy (NFLE) and malignant migrating focal seizures of infancy (MMFSI). To further explore the phenotypic spectrum associated with KCNT1, we examined individuals affected with focal epilepsy or an epileptic encephalopathy for mutations in the gene. We identified KCNT1 mutations in 12 previously unreported patients with focal epilepsy, multifocal epilepsy, cardiac arrhythmia, and in a family with sudden unexpected death in epilepsy (SUDEP), in addition to patients with NFLE and MMFSI. In contrast to the 100% penetrance so far reported for KCNT1 mutations, we observed incomplete penetrance. It is notable that we report that the one KCNT1 mutation, p.Arg398Gln, can lead to either of the two distinct phenotypes, ADNFLE or MMFSI, even within the same family. This indicates that genotype-phenotype relationships for KCNT1 mutations are not straightforward. We demonstrate that KCNT1 mutations are highly pleiotropic and are associated with phenotypes other than ADNFLE and MMFSI. KCNT1 mutations are now associated with Ohtahara syndrome, MMFSI, and nocturnal focal epilepsy. They may also be associated with multifocal epilepsy and cardiac disturbances.
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http://dx.doi.org/10.1111/epi.13071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5915334PMC
September 2015

Familial neonatal seizures in 36 families: Clinical and genetic features correlate with outcome.

Epilepsia 2015 Jul 15;56(7):1071-80. Epub 2015 May 15.

Epilepsy Research Centre, Department of Medicine, Austin Health, The University of Melbourne, Heidelberg, Victoria, Australia.

Objective: We evaluated seizure outcome in a large cohort of familial neonatal seizures (FNS), and examined phenotypic overlap with different molecular lesions.

Methods: Detailed clinical data were collected from 36 families comprising two or more individuals with neonatal seizures. The seizure course and occurrence of seizures later in life were analyzed. Families were screened for KCNQ2, KCNQ3, SCN2A, and PRRT2 mutations, and linkage studies were performed in mutation-negative families to exclude known loci.

Results: Thirty-three families fulfilled clinical criteria for benign familial neonatal epilepsy (BFNE); 27 of these families had KCNQ2 mutations, one had a KCNQ3 mutation, and two had SCN2A mutations. Seizures persisting after age 6 months were reported in 31% of individuals with KCNQ2 mutations; later seizures were associated with frequent neonatal seizures. Linkage mapping in two mutation-negative BFNE families excluded linkage to KCNQ2, KCNQ3, and SCN2A, but linkage to KCNQ2 could not be excluded in the third mutation-negative BFNE family. The three remaining families did not fulfill criteria of BFNE due to developmental delay or intellectual disability; a molecular lesion was identified in two; the other family remains unsolved.

Significance: Most families in our cohort of familial neonatal seizures fulfill criteria for BFNE; the molecular cause was identified in 91%. Most had KCNQ2 mutations, but two families had SCN2A mutations, which are normally associated with a mixed picture of neonatal and infantile onset seizures. Seizures later in life are more common in BFNE than previously reported and are associated with a greater number of seizures in the neonatal period. Linkage studies in two families excluded known loci, suggesting a further gene is involved in BFNE.
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http://dx.doi.org/10.1111/epi.13020DOI Listing
July 2015

Single nucleotide variations in CLCN6 identified in patients with benign partial epilepsies in infancy and/or febrile seizures.

PLoS One 2015 20;10(3):e0118946. Epub 2015 Mar 20.

Department of Pediatrics, Juntendo University Faculty of Medicine, Tokyo, Japan.

Nucleotide alterations in the gene encoding proline-rich transmembrane protein 2 (PRRT2) have been identified in most patients with benign partial epilepsies in infancy (BPEI)/benign familial infantile epilepsy (BFIE). However, not all patients harbor these PRRT2 mutations, indicating the involvement of genes other than PRRT2. In this study, we performed whole exome sequencing analysis for a large family affected with PRRT2-unrelated BPEI. We identified a non-synonymous single nucleotide variation (SNV) in the voltage-sensitive chloride channel 6 gene (CLCN6). A cohort study of 48 BPEI patients without PRRT2 mutations revealed a different CLCN6 SNV in a patient, his sibling and his father who had a history of febrile seizures (FS) but not BPEI. Another study of 48 patients with FS identified an additional SNV in CLCN6. Chloride channels (CLCs) are involved in a multitude of physiologic processes and some members of the CLC family have been linked to inherited diseases. However, a phenotypic correlation has not been confirmed for CLCN6. Although we could not detect significant biological effects linked to the identified CLCN6 SNVs, further studies should investigate potential CLCN6 variants that may underlie the genetic susceptibility to convulsive disorders.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0118946PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4368117PMC
December 2015

A recurrent de novo mutation in KCNC1 causes progressive myoclonus epilepsy.

Nat Genet 2015 Jan 17;47(1):39-46. Epub 2014 Nov 17.

Department of Neurology, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.

Progressive myoclonus epilepsies (PMEs) are a group of rare, inherited disorders manifesting with action myoclonus, tonic-clonic seizures and ataxia. We sequenced the exomes of 84 unrelated individuals with PME of unknown cause and molecularly solved 26 cases (31%). Remarkably, a recurrent de novo mutation, c.959G>A (p.Arg320His), in KCNC1 was identified as a new major cause for PME. Eleven unrelated exome-sequenced (13%) and two affected individuals in a secondary cohort (7%) had this mutation. KCNC1 encodes KV3.1, a subunit of the KV3 voltage-gated potassium ion channels, which are major determinants of high-frequency neuronal firing. Functional analysis of the Arg320His mutant channel showed a dominant-negative loss-of-function effect. Ten cases had pathogenic mutations in known PME-associated genes (NEU1, NHLRC1, AFG3L2, EPM2A, CLN6 and SERPINI1). Identification of mutations in PRNP, SACS and TBC1D24 expand their phenotypic spectra to PME. These findings provide insights into the molecular genetic basis of PME and show the role of de novo mutations in this disease entity.
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http://dx.doi.org/10.1038/ng.3144DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4281260PMC
January 2015

Genetics of epilepsy: The testimony of twins in the molecular era.

Neurology 2014 Sep 8;83(12):1042-8. Epub 2014 Aug 8.

From the Epilepsy Research Centre, Department of Medicine (Neurology) (L.V., K.L., J.E., D.K., M.C., Y.T.-B., R.A.H., I.E.S., S.F.B.), University of Melbourne, Austin Health; School of Medicine (L.V.), The University of Queensland, Brisbane; Department of Neurology (L.V.), Royal Brisbane and Women's Hospital; Centre for Molecular, Environmental, Analytic and Genetic Epidemiology (R.L.M., J.L.H.), University of Melbourne; School of Pharmacy and Medical Sciences and Sansom Institute for Health Research (S.E.H., L.M.D.), University of South Australia, Adelaide; and the Department of Genetic Medicine, SA Pathology (J.C.M.), Women's and Children's Hospital, North Adelaide, Australia.

Objective: Analysis of twins with epilepsy to explore the genetic architecture of specific epilepsies, to evaluate the applicability of the 2010 International League Against Epilepsy (ILAE) organization of epilepsy syndromes, and to integrate molecular genetics with phenotypic analyses.

Methods: A total of 558 twin pairs suspected to have epilepsy were ascertained from twin registries (69%) or referral (31%). Casewise concordance estimates were calculated for epilepsy syndromes. Epilepsies were then grouped according to the 2010 ILAE organizational scheme. Molecular genetic information was utilized where applicable.

Results: Of 558 twin pairs, 418 had confirmed seizures. A total of 534 twin individuals were affected. There were higher twin concordance estimates for monozygotic (MZ) than for dizygotic (DZ) twins for idiopathic generalized epilepsies (MZ = 0.77; DZ = 0.35), genetic epilepsy with febrile seizures plus (MZ = 0.85; DZ = 0.25), and focal epilepsies (MZ = 0.40; DZ = 0.03). Utilizing the 2010 ILAE scheme, the twin data clearly demonstrated genetic influences in the syndromes designated as genetic. Of the 384 tested twin individuals, 10.9% had mutations of large effect in known epilepsy genes or carried validated susceptibility alleles.

Conclusions: Twin studies confirm clear genetic influences for specific epilepsies. Analysis of the twin sample using the 2010 ILAE scheme strongly supported the validity of grouping the "genetic" syndromes together and shows this organizational scheme to be a more flexible and biologically meaningful system than previous classifications. Successful selected molecular testing applied to this cohort is the prelude to future large-scale next-generation sequencing of epilepsy research cohorts. Insights into genetic architecture provided by twin studies provide essential data for optimizing such approaches.
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http://dx.doi.org/10.1212/WNL.0000000000000790DOI Listing
September 2014

A variant of KCC2 from patients with febrile seizures impairs neuronal Cl- extrusion and dendritic spine formation.

EMBO Rep 2014 Jun 24;15(6):723-9. Epub 2014 Mar 24.

Department of Biosciences, University of Helsinki, Helsinki, Finland Neuroscience Center, University of Helsinki, Helsinki, Finland

Genetic variation in SLC12A5 which encodes KCC2, the neuron-specific cation-chloride cotransporter that is essential for hyperpolarizing GABAergic signaling and formation of cortical dendritic spines, has not been reported in human disease. Screening of SLC12A5 revealed a co-segregating variant (KCC2-R952H) in an Australian family with febrile seizures. We show that KCC2-R952H reduces neuronal Cl(-) extrusion and has a compromised ability to induce dendritic spines in vivo and in vitro. Biochemical analyses indicate a reduced surface expression of KCC2-R952H which likely contributes to the functional deficits. Our data suggest that KCC2-R952H is a bona fide susceptibility variant for febrile seizures.
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http://dx.doi.org/10.1002/embr.201438749DOI Listing
June 2014

KCNT1 gain of function in 2 epilepsy phenotypes is reversed by quinidine.

Ann Neurol 2014 Apr 14;75(4):581-90. Epub 2014 Apr 14.

Ion Channels and Disease Group, Epilepsy Division, Florey Institute of Neuroscience and Mental Health, Parkville, Australia.

Objective: Mutations in KCNT1 have been implicated in autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) and epilepsy of infancy with migrating focal seizures (EIMFS). More recently, a whole exome sequencing study of epileptic encephalopathies identified an additional de novo mutation in 1 proband with EIMFS. We aim to investigate the electrophysiological and pharmacological characteristics of hKCNT1 mutations and examine developmental expression levels.

Methods: Here we use a Xenopus laevis oocyte-based automated 2-electrode voltage clamp assay. The effects of quinidine (100 and 300 μM) are also tested. Using quantitative reverse transcriptase polymerase chain reaction, the relative levels of mouse brain mKcnt1 mRNA expression are determined.

Results: We demonstrate that KCNT1 mutations implicated in epilepsy cause a marked increase in function. Importantly, there is a significant group difference in gain of function between mutations associated with ADNFLE and EIMFS. Finally, exposure to quinidine significantly reduces this gain of function for all mutations studied.

Interpretation: These results establish direction for a targeted therapy and potentially exemplify a translational paradigm for in vitro studies informing novel therapies in a neuropsychiatric disease.
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http://dx.doi.org/10.1002/ana.24128DOI Listing
April 2014

Mutations in mammalian target of rapamycin regulator DEPDC5 cause focal epilepsy with brain malformations.

Ann Neurol 2014 May 14;75(5):782-7. Epub 2014 Apr 14.

Epilepsy Research Centre, Department of Medicine, University of Melbourne, Austin Health, Melbourne, Australia; Florey Institute of Neuroscience and Mental Health, Melbourne, Australia; Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia.

We recently identified DEPDC5 as the gene for familial focal epilepsy with variable foci and found mutations in >10% of small families with nonlesional focal epilepsy. Here we show that DEPDC5 mutations are associated with both lesional and nonlesional epilepsies, even within the same family. DEPDC5-associated malformations include bottom-of-the-sulcus dysplasia (3 members from 2 families), and focal band heterotopia (1 individual). DEPDC5 negatively regulates the mammalian target of rapamycin (mTOR) pathway, which plays a key role in cell growth. The clinicoradiological phenotypes associated with DEPDC5 mutations share features with the archetypal mTORopathy, tuberous sclerosis, raising the possibility of therapies targeted to this pathway.
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http://dx.doi.org/10.1002/ana.24126DOI Listing
May 2014

Autosomal dominant vasovagal syncope: clinical features and linkage to chromosome 15q26.

Neurology 2013 Apr;80(16):1485-93

Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Heidelberg, Australia.

Objective: To establish the occurrence of an autosomal dominant form of vasovagal syncope (VVS) by detailed phenotyping of multiplex families and identification of the causative locus.

Methods: Patients with VVS and a family history of syncope were recruited. A standardized questionnaire was administered to all available family members and medical records were reviewed. Of 44 families recruited, 6 were suggestive of autosomal dominant inheritance. Genome-wide linkage was performed in family A using single nucleotide polymorphism genotyping microarrays. Targeted analysis of chromosome 15q26 with microsatellite markers was implemented in 4 families; 1 family was too small for analysis.

Results: Family A contained 30 affected individuals over 3 generations with a median onset of 8 to 9 years. The other families comprised 4 to 14 affected individuals. Affected individuals reported typical triggers of VVS (sight of blood, injury, medical procedures, prolonged standing, pain, frightening thoughts). The triggers varied considerably within the families. Significant linkage to chromosome 15q26 (logarithm of odds score 3.28) was found in family A. Linkage to this region was excluded in 2 medium-sized families but not in 2 smaller families. Sequence analysis of the candidate genes SLCO3A1, ST8SIA2, and NR2F2 within the linkage interval did not reveal any mutations.

Conclusions: Familial VVS, inherited in an autosomal dominant manner, may not be rare and has similar features to sporadic VVS. The chromosome 15q26 locus in family A increases the susceptibility to VVS but does not predispose to a particular vasovagal trigger. Linkage analysis in the remaining families established likely genetic heterogeneity.
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http://dx.doi.org/10.1212/WNL.0b013e31828cfad0DOI Listing
April 2013

Mutations in PRRT2 are not a common cause of infantile epileptic encephalopathies.

Epilepsia 2013 May 8;54(5):e86-9. Epub 2013 Apr 8.

Epilepsy Research Program, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia, Australia.

Heterozygous mutations in PRRT2 have recently been identified as the major cause of autosomal dominant benign familial infantile epilepsy (BFIE), infantile convulsions with choreoathetosis syndrome (ICCA), and paroxysmal kinesigenic dyskinesia (PKD). Homozygous mutations in PRRT2 have also been reported in two families with intellectual disability (ID) and seizures. Heterozygous mutations in the genes KCNQ2 and SCN2A cause the two other autosomal dominant seizure disorders of infancy: benign familial neonatal epilepsy and benign familial neonatal-infantile epilepsy. Mutations in KCNQ2 and SCN2A also contribute to severe infantile epileptic encephalopathies (IEEs) in which seizures and intellectual disability co-occur. We therefore hypothesized that PRRT2 mutations may also underlie cases of IEE. We examined PRRT2 for heterozygous, compound heterozygous or homozygous mutations to determine their frequency in causing epileptic encephalopathies (EEs). Two hundred twenty patients with EEs with onset by 2 years were phenotyped. An assay for the common PRRT2 c.649-650insC mutation and high resolution-melt analysis for mutations in the remaining exons of PRRT2 were performed. Neither the common mutation nor any other pathogenic variants in PRRT2 were detected in the 220 patients. Our findings suggest that mutations in PRRT2 are not a common cause of IEEs.
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http://dx.doi.org/10.1111/epi.12167DOI Listing
May 2013

Mutations in DEPDC5 cause familial focal epilepsy with variable foci.

Nat Genet 2013 May 31;45(5):546-51. Epub 2013 Mar 31.

Epilepsy Research Program, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia, Australia.

The majority of epilepsies are focal in origin, with seizures emanating from one brain region. Although focal epilepsies often arise from structural brain lesions, many affected individuals have normal brain imaging. The etiology is unknown in the majority of individuals, although genetic factors are increasingly recognized. Autosomal dominant familial focal epilepsy with variable foci (FFEVF) is notable because family members have seizures originating from different cortical regions. Using exome sequencing, we detected DEPDC5 mutations in two affected families. We subsequently identified mutations in five of six additional published large families with FFEVF. Study of families with focal epilepsy that were too small for conventional clinical diagnosis with FFEVF identified DEPDC5 mutations in approximately 12% of families (10/82). This high frequency establishes DEPDC5 mutations as a common cause of familial focal epilepsies. Shared homology with G protein signaling molecules and localization in human neurons suggest a role of DEPDC5 in neuronal signal transduction.
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http://dx.doi.org/10.1038/ng.2599DOI Listing
May 2013

Role of PRRT2 in common paroxysmal neurological disorders: a gene with remarkable pleiotropy.

J Med Genet 2013 Mar 23;50(3):133-9. Epub 2013 Jan 23.

School of Pharmacy and Medical Sciences, University of South Australia, P4-47, City East Campus, GPO Box 2471, Adelaide, SA 5001, Australia.

Mutations in the gene PRRT2 encoding proline-rich transmembrane protein 2 have recently been identified as the cause of three clinical entities: benign familial infantile epilepsy (BFIE), infantile convulsions with choreoathetosis (ICCA) syndrome, and paroxysmal kinesigenic dyskinesia (PKD). Patients with ICCA have both BFIE and PKD and families with ICCA may contain individuals who exhibit all three phenotypes. These three phenotypes were all mapped by linkage analyses to the pericentromeric region of chromosome 16, and were hypothesised to have the same genetic basis due to the co-occurrence of the disorders in some families. Despite considerable effort, the gene or genes for BFIE, ICCA, and PKD were not identified for many years after the linkage region was identified. Mutations in the gene PRRT2 were identified in several Chinese families with PKD, suggesting that the gene may also be responsible for ICCA and BFIE in families linked to the chromosome 16 locus. This was demonstrated to be the case, with the majority of families with ICCA and BFIE found to have PRRT2 mutations. The vast majority of these mutations are truncating and are predicted to lead to haploinsufficiency. PRRT2 is a largely uncharacterised protein. It is expressed in the brain and has been demonstrated to interact with SNAP-25, a component of the molecular machinery involved in the release of neurotransmitters at the presynaptic membrane. Therefore, the PRRT2 protein may play a role in this process. However, the molecular mechanisms underlying the remarkable pleiotropy associated with PRRT2 mutations have still to be determined.
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http://dx.doi.org/10.1136/jmedgenet-2012-101406DOI Listing
March 2013

Missense mutations in the sodium-gated potassium channel gene KCNT1 cause severe autosomal dominant nocturnal frontal lobe epilepsy.

Nat Genet 2012 Nov 21;44(11):1188-90. Epub 2012 Oct 21.

Epilepsy Research Program, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia.

We performed genomic mapping of a family with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) and intellectual and psychiatric problems, identifying a disease-associated region on chromosome 9q34.3. Whole-exome sequencing identified a mutation in KCNT1, encoding a sodium-gated potassium channel subunit. KCNT1 mutations were identified in two additional families and a sporadic case with severe ADNFLE and psychiatric features. These findings implicate the sodium-gated potassium channel complex in ADNFLE and, more broadly, in the pathogenesis of focal epilepsies.
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http://dx.doi.org/10.1038/ng.2440DOI Listing
November 2012

PRRT2 phenotypic spectrum includes sporadic and fever-related infantile seizures.

Neurology 2012 Nov 17;79(21):2104-8. Epub 2012 Oct 17.

Florey Neuroscience Institutes, Melbourne, Australia.

Objective: Benign familial infantile epilepsy (BFIE) is an autosomal dominant epilepsy syndrome characterized by afebrile seizures beginning at about 6 months of age. Mutations in PRRT2, encoding the proline-rich transmembrane protein 2 gene, have recently been identified in the majority of families with BFIE and the associated syndrome of infantile convulsions and choreoathetosis (ICCA). We asked whether the phenotypic spectrum of PRRT2 was broader than initially recognized by studying patients with sporadic benign infantile seizures and non-BFIE familial infantile seizures for PRRT2 mutations.

Methods: Forty-four probands with infantile-onset seizures, infantile convulsions with mild gastroenteritis, and benign neonatal seizures underwent detailed phenotyping and PRRT2 sequencing. The familial segregation of mutations identified in probands was studied.

Results: The PRRT2 mutation c.649-650insC (p.R217fsX224) was identified in 11 probands. Nine probands had a family history of BFIE or ICCA. Two probands had no family history of infantile seizures or paroxysmal kinesigenic dyskinesia and had de novo PRRT2 mutations. Febrile seizures with or without afebrile seizures were observed in 2 families with PRRT2 mutations.

Conclusions: PRRT2 mutations are present in >80% of BFIE and >90% ICCA families, but are not a common cause of other forms of infantile epilepsy. De novo mutations of PRRT2 can cause sporadic benign infantile seizures. Seizures with fever may occur in BFIE such that it may be difficult to distinguish BFIE from febrile seizures and febrile seizures plus in small families.
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http://dx.doi.org/10.1212/WNL.0b013e3182752c6cDOI Listing
November 2012

Familial focal epilepsy with variable foci mapped to chromosome 22q12: expansion of the phenotypic spectrum.

Epilepsia 2012 Aug 10;53(8):e151-5. Epub 2012 Jul 10.

Epilepsy Research Centre, University of Melbourne, Austin Health, Heidelberg, Victoria, Australia.

We aimed to refine the phenotypic spectrum and map the causative gene in two families with familial focal epilepsy with variable foci (FFEVF). A new five-generation Australian FFEVF family (A) underwent electroclinical phenotyping, and the original four-generation Australian FFEVF family (B) (Ann Neurol, 44, 1998, 890) was re-analyzed, including new affected individuals. Mapping studies examined segregation at the chromosome 22q12 FFEVF region. In family B, the original whole genome microsatellite data was reviewed. Five subjects in family A and 10 in family B had FFEVF with predominantly awake attacks and active EEG studies with a different phenotypic picture from other families. In family B, reanalysis excluded the tentative 2q locus reported. Both families mapped to chromosome 22q12. Our results confirm chromosome 22q12 as the solitary locus for FFEVF. Both families show a subtly different phenotype to other published families extending the clinical spectrum of FFEVF.
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http://dx.doi.org/10.1111/j.1528-1167.2012.03585.xDOI Listing
August 2012

KCNQ2 encephalopathy: emerging phenotype of a neonatal epileptic encephalopathy.

Ann Neurol 2012 Jan;71(1):15-25

Neurogenetics Group, VIB-Department of Molecular Genetics, University of Antwerp, Antwerp, Belgium.

Objective: KCNQ2 and KCNQ3 mutations are known to be responsible for benign familial neonatal seizures (BFNS). A few reports on patients with a KCNQ2 mutation with a more severe outcome exist, but a definite relationship has not been established. In this study we investigated whether KCNQ2/3 mutations are a frequent cause of epileptic encephalopathies with an early onset and whether a recognizable phenotype exists.

Methods: We analyzed 80 patients with unexplained neonatal or early-infantile seizures and associated psychomotor retardation for KCNQ2 and KCNQ3 mutations. Clinical and imaging data were reviewed in detail.

Results: We found 7 different heterozygous KCNQ2 mutations in 8 patients (8/80; 10%); 6 mutations arose de novo. One parent with a milder phenotype was mosaic for the mutation. No KCNQ3 mutations were found. The 8 patients had onset of intractable seizures in the first week of life with a prominent tonic component. Seizures generally resolved by age 3 years but the children had profound, or less frequently severe, intellectual disability with motor impairment. Electroencephalography (EEG) at onset showed a burst-suppression pattern or multifocal epileptiform activity. Early magnetic resonance imaging (MRI) of the brain showed characteristic hyperintensities in the basal ganglia and thalamus that later resolved.

Interpretation: KCNQ2 mutations are found in a substantial proportion of patients with a neonatal epileptic encephalopathy with a potentially recognizable electroclinical and radiological phenotype. This suggests that KCNQ2 screening should be included in the diagnostic workup of refractory neonatal seizures of unknown origin.
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http://dx.doi.org/10.1002/ana.22644DOI Listing
January 2012

PRRT2 mutations cause benign familial infantile epilepsy and infantile convulsions with choreoathetosis syndrome.

Am J Hum Genet 2012 Jan;90(1):152-60

Epilepsy Research Program, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia.

Benign familial infantile epilepsy (BFIE) is a self-limited seizure disorder that occurs in infancy and has autosomal-dominant inheritance. We have identified heterozygous mutations in PRRT2, which encodes proline-rich transmembrane protein 2, in 14 of 17 families (82%) affected by BFIE, indicating that PRRT2 mutations are the most frequent cause of this disorder. We also report PRRT2 mutations in five of six (83%) families affected by infantile convulsions and choreoathetosis (ICCA) syndrome, a familial syndrome in which infantile seizures and an adolescent-onset movement disorder, paroxysmal kinesigenic choreoathetosis (PKC), co-occur. These findings show that mutations in PRRT2 cause both epilepsy and a movement disorder. Furthermore, PRRT2 mutations elicit pleiotropy in terms of both age of expression (infancy versus later childhood) and anatomical substrate (cortex versus basal ganglia).
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http://dx.doi.org/10.1016/j.ajhg.2011.12.003DOI Listing
January 2012

The Role of Seizure-Related SEZ6 as a Susceptibility Gene in Febrile Seizures.

Neurol Res Int 2011 16;2011:917565. Epub 2011 Jul 16.

Department of Genetic Medicine, Directorate of Genetics and Molecular Pathology, SA Pathology at Women's and Children's Hospital, Adelaide, SA 5006, Australia.

Sixty cases of febrile seizures from a Chinese cohort had previously been reported with a strong association between variants in the seizure-related (SEZ) 6 gene and febrile seizures. They found a striking lack of genetic variation in their controls. We found genetic variation in SEZ6 at similar levels at the same DNA sequence positions in our 94 febrile seizure cases as in our 96 unaffected controls. Two of our febrile seizure cases carried rare variants predicted to have damaging consequences. Combined with some of the variants from the Chinese cohort, these data are compatible with a role for SEZ6 as a susceptibility gene for febrile seizures. However, the polygenic determinants underlying most cases of febrile seizures with complex inheritance remain to be determined.
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http://dx.doi.org/10.1155/2011/917565DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3139179PMC
November 2011

Proposed genetic classification of the "benign" familial neonatal and infantile epilepsies.

Epilepsia 2011 Mar;52(3):649-50

Department of Genetic Medicine, Directorate of Genetics and Molecular Pathology, SA Pathology at Women's and Children's Hospital, Adelaide, Australia.

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http://dx.doi.org/10.1111/j.1528-1167.2010.02953.xDOI Listing
March 2011

Familial neonatal seizures with intellectual disability caused by a microduplication of chromosome 2q24.3.

Epilepsia 2010 Sep;51(9):1865-9

SA Pathology at Women's and Children's Hospital, Adelaide, South Australia, Australia.

A family with dominantly inherited neonatal seizures and intellectual disability was atypical for neonatal and infantile seizure syndromes associated with potassium (KCNQ2 and KCNQ3) and sodium (SCN2A) channel mutations. Microsatellite markers linked to KCNQ2, KCNQ3, and SCN2A were examined to exclude candidate locations, but instead revealed a duplication detected by observation of three alleles for two markers flanking SCN2A. Characterization revealed a 1.57 Mb duplication at 2q24.3 containing eight genes including SCN2A, SCN3A, and the 3¢ end of SCN1A. The duplication was partially inverted and inserted within or near SCN1A, probably affecting the expression levels of associated genes, including sodium channels. Rare or unique microchromosomal copy number mutations might underlie familial epilepsies that do not fit within the clinical criteria for the established syndromes.
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http://dx.doi.org/10.1111/j.1528-1167.2010.02558.xDOI Listing
September 2010

Neonatal seizures and long QT syndrome: a cardiocerebral channelopathy?

Epilepsia 2010 Feb 27;51(2):293-6. Epub 2009 Oct 27.

SA Pathology at Women's and Children's Hospital, North Adelaide, SA, Australia.

We identified a patient with electrophysiologically verified neonatal long QT syndrome (LQTS) and neonatal seizures in the presence of a controlled cardiac rhythm. To find a cause for this unusual combination of phenotypes, we tested the patient for mutations in seven ion channel genes associated with either LQTS or benign familial neonatal seizures (BFNS). Comparative genome hybridization (CGH) was done to exclude the possibility of a contiguous gene syndrome. No mutations were found in the genes (KCNQ2, KCNQ3) associated with BFNS, and CGH was negative. A previously described mutation and a known rare variant were found in the LQTS-associated genes SCN5A and KCNE2. Both are expressed in the brain, and although mutations have not been associated with epilepsy, we propose a pathophysiologic mechanism by which the combination of molecular changes may cause seizures.
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http://dx.doi.org/10.1111/j.1528-1167.2009.02317.xDOI Listing
February 2010
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