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Deletions of SCN2A and SCN3A genes in a patient with West syndrome and autistic spectrum disorder
Seizure: European Journal of Epilepsy 60 (2018) 91–93
Contents lists available at ScienceDirect
Seizure: European Journal of Epilepsy journal homepage: www.elsevier.com/locate/seizure
Deletions of SCN2A and SCN3A genes in a patient with West syndrome and autistic spectrum disorder
T
⁎
Pin Fee Chonga, , Hirotomo Saitsub, Yasunari Sakaic, Toru Imagia, Ryoko Nakamuraa, Masaru Matsukuraa, Naomichi Matsumotod, Ryutaro Kiraa a
Department of Pediatric Neurology, Fukuoka Children’s Hospital, Fukuoka, Japan Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu, Japan c Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan d Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan b
A R T I C LE I N FO
A B S T R A C T
Keywords: West syndrome Autistic spectrum disorders SCN2A Whole-exome sequencing Deletion XHMM
SCN2A encodes the alpha-subunit of voltage-gated sodium channel, Nav1.2, which is highly expressed at an early stage of the postnatal brain. Genetic studies revealed that de novo heterozygous mutations of SCN2A caused severe developmental disorders in childhood, such as autism and epileptic encephalopathy. However, few reports have demonstrated the cases carrying segmental deletions at the SCN2A locus for those with epileptic disorders. In this study, we report a 1.8-year-old boy, who presented with West syndrome in infancy and developed the sequelae of psychomotor delay and autism. Since whole-exome sequencing did not detect pathogenic mutations, we extensively searched for microdeletions and duplications by applying the eXome Hidden Markov Model (XHMM) for read depths of sequenced intervals. Using this approach, we identified a de novo deletion spanning the 1.1-Mb region of chromosome 2q24.3. We found that the deleted interval included the SCN2A and SCN3A loci. These data validate the utility of XHMM and support that SCN2A is involved in the pathogenic processes underlying epileptic encephalopathy in childhood.
1. Introduction West syndrome (WS) is one of the well-known types of early onset epileptic encephalopathy, which is characterized by infantile onset of recurrent seizures and prominent interictal epileptiform discharges with frequent neurological comorbidity. A variety of mutations and copy number variations (CNVs) have been associated with this epileptic disorder. Among these, germline mutations in voltage-gated sodium channels (VGSCs) have been implicated in various neurological disorders. In particular, the chromosome 2q24.3 region has been drawing increasing attention since it harbors three VGSC genes: SCN1A, SCN2A, and SCN3A. We present the case of a one-year-old male with autistic features, psychomotor delay, and a history of WS. A de novo 1.1-Mb heterozygous deletion spanning the SCN2A and SCN3A genes was identified in this patient, demonstrating it as one of the genetic causes of WS and developmental problems. 2. Case report The proband was born after 39 weeks of gestation to healthy non-
⁎
consanguineous parents. His birth weight was 2982 g (−0.04 SD) and the head circumference was 32.5 cm (−0.57 SD). Although he developed normally for the first 4 months, eye contact and facial expression disappeared at this age. Motor delay was evident at 9 months. He was referred to us at 10 months for recurrent episodes of head nodding and upward eye deviations occurring in clusters. Facial dysmorphisms of upslanted palpebral fissure, hypertelorism, and cupid’s bow mouth were noted, with an absence of eye contact and smiles. Poor head control, generalized muscular hypotonia, stereotypic behavior, and dystonia-like involuntary movements were observed. Interictal electroencephalogram demonstrated a typical hypsarrhythmic pattern when sleeping and awake (Fig. 1A). He was thus diagnosed with WS. Pyridoxine and valproate did not improve the seizure frequency. Intramuscular low-dose adrenocorticotropic hormone administered was effective, and subsequent seizure control was achieved with topiramate. Known etiologic factors for symptomatic WS were ruled out after laboratory tests including metabolic profiling. Intracranial MRI yielded normal findings (Fig. 1B). Chromosomal analysis using G-banding revealed a normal male karyotype. Development was evaluated to be as low as 8 months at 21 months of age according to the Denver
Corresponding author at: Department of Pediatric Neurology, Fukuoka Children’s Hospital, 5-1-1 Kashiiteriha, Higashi-ku, Fukuoka 813-0017, Japan. E-mail address: [email protected] (P.F. Chong).
https://doi.org/10.1016/j.seizure.2018.06.012 Received 9 February 2018; Received in revised form 11 May 2018; Accepted 13 June 2018 1059-1311/ © 2018 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.
Seizure: European Journal of Epilepsy 60 (2018) 91–93
P.F. Chong et al.
Fig. 1. (A) Interictal electroencephalogram (EEG) at 10 months of age revealed the characteristic random high-voltage slow waves with spikes and polyspikes activity. Fragmentation of the hypsarrhythmic activity was noted in this sleep EEG recording. (B) Brain magnetic resonance imaging on admission at 10 months revealed no pathological findings. Axial T2-weighted FLAIR image (left) and sagittal T1-weighted image (right). (C) XHMM analysis of the whole of chromosome 2. X- and Y-axes show the physical position and read-depth z-score, respectively. XHMM automatically called a deletion (gray box). (D) High-magnification view of the deleted interval. Deletion interval called by XHMM (upper panel) contained 6 genes including SCN3A and SCN2A (middle panel), and Nord’s script analysis could detect additional FIGN deletion (lower panel). Deleted genes are highlighted in red. (E) Quantitative real-time PCR analysis confirmed the heterozygous deletion of SCN3A and SCN2A in the patient but not in his parents, indicating that the microdeletion occurred de novo. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Table 1 Clinical phenotypes of SCN2A and SCN3A deletion cases without SCN1A involvement. Patient 1 [2]
Patient 2 [3]
Patient 3 [4]
Present Case
Sex Age at report Development Autistic features Other neurological symptoms
Female 40 months Delayed Yes Not mentioned
Male 3 years Delayed Yes Microcephaly
Facial dysmorphism
Prominent nasal bridge, down slanting palpebral fissure, low-set ears, micrognathia No – Immature myelination at periventricular areas No epileptiform disharges 2.8 Mb FIGN, GRB14, COBLL1, SLC38A11, SCN3A, SCN2A, part of CSRNP3
Female 25 years Mildly delayed Yes Mild hypotonia, Ocular motor apraxia, Bipolar disorder Short palpebral fissures, short neck Yes ‘shiver-like’ episodes/unknown Not mentioned
No – Not mentioned
Male 21 months Delayed Yes Generalized hypotonia, dystonia-like movement Upslanted palpebral fissure, hypertelorism, cupid’s bow mouth Yes Infantile spasms/West syndrome Normal
Not mentioned 230 kb SCN2A, part of SCN3A
Hypsarrhythmia 1,102 kb FIGN, GRB14, COBLL1, SLC38A11, SCN3A, SCN2A, part of CSRNP3
Epilepsy Seizure types/Diagnosis Brain MRI Electroencephalogram Deletion size Involved genes
No epileptiform discharges 112 kb Part of SCN2A, part of SCN3A
Not mentioned
CDKL5, SLC35A2, CASK, PCDH19, or MECP2, we hypothesized that the present case might carry pathogenic CNVs. Indeed, XHMM successfully detected a microdeletion encompassing a 1,102-kb region of chromosome 2q24.3 (GRch37/hg19; chr2: 165,349,365–166,451,795) (Fig. 1C). Analysis of the relative coverage ratio depth using Nord’s script against genes within or adjacent to the deleted interval revealed that the deletion contained FIGN, GRB14, COBLL1, SLC38A11, SCN3A, SCN2A, and part of CSRNP3 (Fig. 1D). SCN1A gene located at the telomeric side of this region was not involved. qPCR analysis confirmed that the microdeletion spanning SCN3A and SCN2A had occurred de novo (Fig. 1E).
development screening test. He was diagnosed with autism spectrum disorders (ASD) using the Modified Checklist for Autism in ToddlersRevised. Following written informed consent, genomic DNA was extracted from leukocytes of the patient and his parents. Whole-exome sequencing (WES) and variant calling were performed as previously described [1]. CNV analysis using the WES data was performed by eXome Hidden Markov Model (XHMM) algorithm. The deletion interval was further determined by analyzing the relative depth of coverage ratio (Nord’s script) [1]. Quantitative real-time PCR (qPCR) was performed to validate the predicted CNVs (Supplementary method). Experimental protocols were approved by the Institutional Review Board of Yokohama City University School of Medicine, Japan. Following WES, 95.8% of target coding sequences were covered by 10 or more reads. Because WES did not reveal any causative de novo point mutations in previously known epileptic encephalopathy-associated genes including ARX, KCNT1, KCNQ2, SCN1A, SCN2A, SCN8A, STXBP1, SPTAN1, GNAO1, GRIN1, FOXG1, QARS, EEF1A2, PIGA,
3. Discussion Chromosomal deletions involving the Sodium voltage-gated channels (SCN) gene cluster at 2q24.3 have been documented in patients with epilepsy [1]. Deletion of the SCN1A gene was perceived to be the dominant genetic factor in these cases, as loss-of-function SCN1A 92
Seizure: European Journal of Epilepsy 60 (2018) 91–93
P.F. Chong et al.
Conflict of interest
mutations are associated with severe epilepsy phenotypes. Three cases of SCN2A deletion without concomitant SCN1A involvement were reported previously [2–4]. Clinical symptoms and deletion ranges are summarized in Table 1. Although all patients showed autistic features, neurodevelopmental disorders, and facial dysmorphism, only 1 patient exhibited infantile seizure of unknown type without electroencephalogram abnormalities [3]. This is the first report implicating a deletion of SCN2A and SCN3A as a probable genetic cause in a clearly defined WS case. SCN2A encodes the α-subunit of VGSCs (Nav1.2), which are highly expressed in the brain at an early postnatal stage. SCN2A mutations have been associated with various neurodevelopmental disorders, including ASDs and intellectual disability. Earlier studies have shown that point mutations in SCN2A cause a variety of seizure phenotypes ranging from benign neonatal-infantile seizures to severe infantile-onset epilepsies, including Ohtahara syndrome, WS, and epilepsy of infancy with migrating focal seizures. Moreover, deletion of the SCN2A gene has been reported in ASDs, suggesting haploinsufficiency of SCN2A may promote the onset of autistic features. Clinical characteristics of the proband included autistic behavior, involuntary movement, and facial dysmorphism, consistent with previously reported 2q24.3 deletion cases. Previous studies indicated that Nav1.2 is predominantly expressed at terminals and initial segments of axons, playing essential roles in regulating both neuronal firing and inter-neuronal connectivity. SCN3A-encoded Nav1.3 exhibits a predominantly somato-dendritic localization and has properties that may cause neuronal hyper-responsiveness. SCN3A was thought to be insignificant in the neurobiology of epilepsy. However, a possible association of SCN3A variants and focal epilepsy owing to increased seizure susceptibility was reported in recent electrophysiological studies. Given the intact copy number of SCN1A in this case, the SCN2A deletion might be sufficient to present a severely epileptic phenotype. Haploinsufficiency of SCN3A and other deleted genes or dual haploinsufficiency of SCN2A and SCN3A may lead to the syndromic phenotypes of WS, dysmorphism and ASDs as observed in our case. Future studies involving the functional interactions between SCN3A and SCN2A could be helpful. Collectively, our study provides new evidence that the CNV involving SCN2A plays a critical role in the pathogenic processes for both WS and ASDs. It also emphasizes XHMM as a powerful tool for identifying pathogenic CNVs in epileptic disorders.
None. Acknowledgments We thank the patient and his family for their participation in this study. We also thank Nobuko Watanabe and Mai Sato for their technical assistance. This work is supported in part by a grant for Research on Measures for Intractable Diseases (14525125); a grant for Comprehensive Research on Disability Health and Welfare (13802019); the Strategic Research Program for Brain Science (SRPBS) (11105137) and Practical Research Project for Rare/Intractable Diseases (27280301), and a grant for Initiative on Rare and Undiagnosed Diseases in Pediatrics (IRUD-P) (15gk0110012h0101) from Japan Agency for Medical Research and Development; a Grant-in-Aid for Scientific Research on Innovative Areas (Transcription Cycle, 24118007) from the Ministry of Education, Culture, Sports, Science and Technology of Japan; Grants-in-Aid for Scientific Research (B) (25293085) and (A) (13313587), Challenging Exploratory Research (26670505) from the Japan Society for the Promotion of Science; the fund for Creation of Innovation Centers for Advanced Interdisciplinary Research Areas Program in the Project for Developing Innovation Systems (11105305) from the Japan Science and Technology Agency; and the Takeda Science Foundation. References [1] Kodera H, Kato M, Nord AS, Walsh T, Lee M, Yamanaka G, et al. Targeted capture and sequencing for detection of mutations causing early onset epileptic encephalopathy. Epilepsia 2013;54:1262–9. [2] Chen CP, Lin SP, Chern SR, Chen YJ, Tsai JF, Wu PC, et al. Array-CGH detection of a de novo 2.8 Mb deletion in 2q24.2→q24.3 in a girl with autistic features and developmental delay. Eur J Med Genet 2010;53:217–20. [3] Bartnik M, Chun-Hui Tsai A, Xia Z, Cheung SW, Stankiewicz P. Disruption of the SCN2A and SCN3A genes in a patient with mental retardation, neurobehavioral and psychiatric abnormalities, and a history of infantile seizures. Clin Genet 2011;80:191–5. [4] Celle ME, Cuoco C, Porta S, Gimelli G, Tassano E. Interstitial 2q24.3 deletion including SCN2A and SCN3A genes in a patient with autistic features, psychomotor delay, microcephaly and no history of seizures. Gene 2013;532:294–6.
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Contents lists available at ScienceDirect
Seizure: European Journal of Epilepsy journal homepage: www.elsevier.com/locate/seizure
Deletions of SCN2A and SCN3A genes in a patient with West syndrome and autistic spectrum disorder
T
⁎
Pin Fee Chonga, , Hirotomo Saitsub, Yasunari Sakaic, Toru Imagia, Ryoko Nakamuraa, Masaru Matsukuraa, Naomichi Matsumotod, Ryutaro Kiraa a
Department of Pediatric Neurology, Fukuoka Children’s Hospital, Fukuoka, Japan Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu, Japan c Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan d Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan b
A R T I C LE I N FO
A B S T R A C T
Keywords: West syndrome Autistic spectrum disorders SCN2A Whole-exome sequencing Deletion XHMM
SCN2A encodes the alpha-subunit of voltage-gated sodium channel, Nav1.2, which is highly expressed at an early stage of the postnatal brain. Genetic studies revealed that de novo heterozygous mutations of SCN2A caused severe developmental disorders in childhood, such as autism and epileptic encephalopathy. However, few reports have demonstrated the cases carrying segmental deletions at the SCN2A locus for those with epileptic disorders. In this study, we report a 1.8-year-old boy, who presented with West syndrome in infancy and developed the sequelae of psychomotor delay and autism. Since whole-exome sequencing did not detect pathogenic mutations, we extensively searched for microdeletions and duplications by applying the eXome Hidden Markov Model (XHMM) for read depths of sequenced intervals. Using this approach, we identified a de novo deletion spanning the 1.1-Mb region of chromosome 2q24.3. We found that the deleted interval included the SCN2A and SCN3A loci. These data validate the utility of XHMM and support that SCN2A is involved in the pathogenic processes underlying epileptic encephalopathy in childhood.
1. Introduction West syndrome (WS) is one of the well-known types of early onset epileptic encephalopathy, which is characterized by infantile onset of recurrent seizures and prominent interictal epileptiform discharges with frequent neurological comorbidity. A variety of mutations and copy number variations (CNVs) have been associated with this epileptic disorder. Among these, germline mutations in voltage-gated sodium channels (VGSCs) have been implicated in various neurological disorders. In particular, the chromosome 2q24.3 region has been drawing increasing attention since it harbors three VGSC genes: SCN1A, SCN2A, and SCN3A. We present the case of a one-year-old male with autistic features, psychomotor delay, and a history of WS. A de novo 1.1-Mb heterozygous deletion spanning the SCN2A and SCN3A genes was identified in this patient, demonstrating it as one of the genetic causes of WS and developmental problems. 2. Case report The proband was born after 39 weeks of gestation to healthy non-
⁎
consanguineous parents. His birth weight was 2982 g (−0.04 SD) and the head circumference was 32.5 cm (−0.57 SD). Although he developed normally for the first 4 months, eye contact and facial expression disappeared at this age. Motor delay was evident at 9 months. He was referred to us at 10 months for recurrent episodes of head nodding and upward eye deviations occurring in clusters. Facial dysmorphisms of upslanted palpebral fissure, hypertelorism, and cupid’s bow mouth were noted, with an absence of eye contact and smiles. Poor head control, generalized muscular hypotonia, stereotypic behavior, and dystonia-like involuntary movements were observed. Interictal electroencephalogram demonstrated a typical hypsarrhythmic pattern when sleeping and awake (Fig. 1A). He was thus diagnosed with WS. Pyridoxine and valproate did not improve the seizure frequency. Intramuscular low-dose adrenocorticotropic hormone administered was effective, and subsequent seizure control was achieved with topiramate. Known etiologic factors for symptomatic WS were ruled out after laboratory tests including metabolic profiling. Intracranial MRI yielded normal findings (Fig. 1B). Chromosomal analysis using G-banding revealed a normal male karyotype. Development was evaluated to be as low as 8 months at 21 months of age according to the Denver
Corresponding author at: Department of Pediatric Neurology, Fukuoka Children’s Hospital, 5-1-1 Kashiiteriha, Higashi-ku, Fukuoka 813-0017, Japan. E-mail address: [email protected] (P.F. Chong).
https://doi.org/10.1016/j.seizure.2018.06.012 Received 9 February 2018; Received in revised form 11 May 2018; Accepted 13 June 2018 1059-1311/ © 2018 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.
Seizure: European Journal of Epilepsy 60 (2018) 91–93
P.F. Chong et al.
Fig. 1. (A) Interictal electroencephalogram (EEG) at 10 months of age revealed the characteristic random high-voltage slow waves with spikes and polyspikes activity. Fragmentation of the hypsarrhythmic activity was noted in this sleep EEG recording. (B) Brain magnetic resonance imaging on admission at 10 months revealed no pathological findings. Axial T2-weighted FLAIR image (left) and sagittal T1-weighted image (right). (C) XHMM analysis of the whole of chromosome 2. X- and Y-axes show the physical position and read-depth z-score, respectively. XHMM automatically called a deletion (gray box). (D) High-magnification view of the deleted interval. Deletion interval called by XHMM (upper panel) contained 6 genes including SCN3A and SCN2A (middle panel), and Nord’s script analysis could detect additional FIGN deletion (lower panel). Deleted genes are highlighted in red. (E) Quantitative real-time PCR analysis confirmed the heterozygous deletion of SCN3A and SCN2A in the patient but not in his parents, indicating that the microdeletion occurred de novo. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Table 1 Clinical phenotypes of SCN2A and SCN3A deletion cases without SCN1A involvement. Patient 1 [2]
Patient 2 [3]
Patient 3 [4]
Present Case
Sex Age at report Development Autistic features Other neurological symptoms
Female 40 months Delayed Yes Not mentioned
Male 3 years Delayed Yes Microcephaly
Facial dysmorphism
Prominent nasal bridge, down slanting palpebral fissure, low-set ears, micrognathia No – Immature myelination at periventricular areas No epileptiform disharges 2.8 Mb FIGN, GRB14, COBLL1, SLC38A11, SCN3A, SCN2A, part of CSRNP3
Female 25 years Mildly delayed Yes Mild hypotonia, Ocular motor apraxia, Bipolar disorder Short palpebral fissures, short neck Yes ‘shiver-like’ episodes/unknown Not mentioned
No – Not mentioned
Male 21 months Delayed Yes Generalized hypotonia, dystonia-like movement Upslanted palpebral fissure, hypertelorism, cupid’s bow mouth Yes Infantile spasms/West syndrome Normal
Not mentioned 230 kb SCN2A, part of SCN3A
Hypsarrhythmia 1,102 kb FIGN, GRB14, COBLL1, SLC38A11, SCN3A, SCN2A, part of CSRNP3
Epilepsy Seizure types/Diagnosis Brain MRI Electroencephalogram Deletion size Involved genes
No epileptiform discharges 112 kb Part of SCN2A, part of SCN3A
Not mentioned
CDKL5, SLC35A2, CASK, PCDH19, or MECP2, we hypothesized that the present case might carry pathogenic CNVs. Indeed, XHMM successfully detected a microdeletion encompassing a 1,102-kb region of chromosome 2q24.3 (GRch37/hg19; chr2: 165,349,365–166,451,795) (Fig. 1C). Analysis of the relative coverage ratio depth using Nord’s script against genes within or adjacent to the deleted interval revealed that the deletion contained FIGN, GRB14, COBLL1, SLC38A11, SCN3A, SCN2A, and part of CSRNP3 (Fig. 1D). SCN1A gene located at the telomeric side of this region was not involved. qPCR analysis confirmed that the microdeletion spanning SCN3A and SCN2A had occurred de novo (Fig. 1E).
development screening test. He was diagnosed with autism spectrum disorders (ASD) using the Modified Checklist for Autism in ToddlersRevised. Following written informed consent, genomic DNA was extracted from leukocytes of the patient and his parents. Whole-exome sequencing (WES) and variant calling were performed as previously described [1]. CNV analysis using the WES data was performed by eXome Hidden Markov Model (XHMM) algorithm. The deletion interval was further determined by analyzing the relative depth of coverage ratio (Nord’s script) [1]. Quantitative real-time PCR (qPCR) was performed to validate the predicted CNVs (Supplementary method). Experimental protocols were approved by the Institutional Review Board of Yokohama City University School of Medicine, Japan. Following WES, 95.8% of target coding sequences were covered by 10 or more reads. Because WES did not reveal any causative de novo point mutations in previously known epileptic encephalopathy-associated genes including ARX, KCNT1, KCNQ2, SCN1A, SCN2A, SCN8A, STXBP1, SPTAN1, GNAO1, GRIN1, FOXG1, QARS, EEF1A2, PIGA,
3. Discussion Chromosomal deletions involving the Sodium voltage-gated channels (SCN) gene cluster at 2q24.3 have been documented in patients with epilepsy [1]. Deletion of the SCN1A gene was perceived to be the dominant genetic factor in these cases, as loss-of-function SCN1A 92
Seizure: European Journal of Epilepsy 60 (2018) 91–93
P.F. Chong et al.
Conflict of interest
mutations are associated with severe epilepsy phenotypes. Three cases of SCN2A deletion without concomitant SCN1A involvement were reported previously [2–4]. Clinical symptoms and deletion ranges are summarized in Table 1. Although all patients showed autistic features, neurodevelopmental disorders, and facial dysmorphism, only 1 patient exhibited infantile seizure of unknown type without electroencephalogram abnormalities [3]. This is the first report implicating a deletion of SCN2A and SCN3A as a probable genetic cause in a clearly defined WS case. SCN2A encodes the α-subunit of VGSCs (Nav1.2), which are highly expressed in the brain at an early postnatal stage. SCN2A mutations have been associated with various neurodevelopmental disorders, including ASDs and intellectual disability. Earlier studies have shown that point mutations in SCN2A cause a variety of seizure phenotypes ranging from benign neonatal-infantile seizures to severe infantile-onset epilepsies, including Ohtahara syndrome, WS, and epilepsy of infancy with migrating focal seizures. Moreover, deletion of the SCN2A gene has been reported in ASDs, suggesting haploinsufficiency of SCN2A may promote the onset of autistic features. Clinical characteristics of the proband included autistic behavior, involuntary movement, and facial dysmorphism, consistent with previously reported 2q24.3 deletion cases. Previous studies indicated that Nav1.2 is predominantly expressed at terminals and initial segments of axons, playing essential roles in regulating both neuronal firing and inter-neuronal connectivity. SCN3A-encoded Nav1.3 exhibits a predominantly somato-dendritic localization and has properties that may cause neuronal hyper-responsiveness. SCN3A was thought to be insignificant in the neurobiology of epilepsy. However, a possible association of SCN3A variants and focal epilepsy owing to increased seizure susceptibility was reported in recent electrophysiological studies. Given the intact copy number of SCN1A in this case, the SCN2A deletion might be sufficient to present a severely epileptic phenotype. Haploinsufficiency of SCN3A and other deleted genes or dual haploinsufficiency of SCN2A and SCN3A may lead to the syndromic phenotypes of WS, dysmorphism and ASDs as observed in our case. Future studies involving the functional interactions between SCN3A and SCN2A could be helpful. Collectively, our study provides new evidence that the CNV involving SCN2A plays a critical role in the pathogenic processes for both WS and ASDs. It also emphasizes XHMM as a powerful tool for identifying pathogenic CNVs in epileptic disorders.
None. Acknowledgments We thank the patient and his family for their participation in this study. We also thank Nobuko Watanabe and Mai Sato for their technical assistance. This work is supported in part by a grant for Research on Measures for Intractable Diseases (14525125); a grant for Comprehensive Research on Disability Health and Welfare (13802019); the Strategic Research Program for Brain Science (SRPBS) (11105137) and Practical Research Project for Rare/Intractable Diseases (27280301), and a grant for Initiative on Rare and Undiagnosed Diseases in Pediatrics (IRUD-P) (15gk0110012h0101) from Japan Agency for Medical Research and Development; a Grant-in-Aid for Scientific Research on Innovative Areas (Transcription Cycle, 24118007) from the Ministry of Education, Culture, Sports, Science and Technology of Japan; Grants-in-Aid for Scientific Research (B) (25293085) and (A) (13313587), Challenging Exploratory Research (26670505) from the Japan Society for the Promotion of Science; the fund for Creation of Innovation Centers for Advanced Interdisciplinary Research Areas Program in the Project for Developing Innovation Systems (11105305) from the Japan Science and Technology Agency; and the Takeda Science Foundation. References [1] Kodera H, Kato M, Nord AS, Walsh T, Lee M, Yamanaka G, et al. Targeted capture and sequencing for detection of mutations causing early onset epileptic encephalopathy. Epilepsia 2013;54:1262–9. [2] Chen CP, Lin SP, Chern SR, Chen YJ, Tsai JF, Wu PC, et al. Array-CGH detection of a de novo 2.8 Mb deletion in 2q24.2→q24.3 in a girl with autistic features and developmental delay. Eur J Med Genet 2010;53:217–20. [3] Bartnik M, Chun-Hui Tsai A, Xia Z, Cheung SW, Stankiewicz P. Disruption of the SCN2A and SCN3A genes in a patient with mental retardation, neurobehavioral and psychiatric abnormalities, and a history of infantile seizures. Clin Genet 2011;80:191–5. [4] Celle ME, Cuoco C, Porta S, Gimelli G, Tassano E. Interstitial 2q24.3 deletion including SCN2A and SCN3A genes in a patient with autistic features, psychomotor delay, microcephaly and no history of seizures. Gene 2013;532:294–6.
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