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Pantazis A, Kaneko M, Angelini M, Steccanella F, Westerlund AM, Lindström SH, Nilsson M, Delemotte L, Saitta SC, Olcese R. Tracking the motion of the K V1.2 voltage sensor reveals the molecular perturbations caused by a de novo mutation in a case of epilepsy. J Physiol 2020; 598:5245-5269. [PMID: 32833227 PMCID: PMC8923147 DOI: 10.1113/jp280438] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 08/14/2020] [Indexed: 12/28/2022] Open
Abstract
KEY POINTS KV1.2 channels, encoded by the KCNA2 gene, regulate neuronal excitability by conducting K+ upon depolarization. A new KCNA2 missense variant was discovered in a patient with epilepsy, causing amino acid substitution F302L at helix S4, in the KV1.2 voltage-sensing domain. Immunocytochemistry and flow cytometry showed that F302L does not impair KCNA2 subunit surface trafficking. Molecular dynamics simulations indicated that F302L alters the exposure of S4 residues to membrane lipids. Voltage clamp fluorometry revealed that the voltage-sensing domain of KV1.2-F302L channels is more sensitive to depolarization. Accordingly, KV1.2-F302L channels opened faster and at more negative potentials; however, they also exhibited enhanced inactivation: that is, F302L causes both gain- and loss-of-function effects. Coexpression of KCNA2-WT and -F302L did not fully rescue these effects. The proband's symptoms are more characteristic of patients with loss of KCNA2 function. Enhanced KV1.2 inactivation could lead to increased synaptic release in excitatory neurons, steering neuronal circuits towards epilepsy. ABSTRACT An exome-based diagnostic panel in an infant with epilepsy revealed a previously unreported de novo missense variant in KCNA2, which encodes voltage-gated K+ channel KV1.2. This variant causes substitution F302L, in helix S4 of the KV1.2 voltage-sensing domain (VSD). F302L does not affect KCNA2 subunit membrane trafficking. However, it does alter channel functional properties, accelerating channel opening at more hyperpolarized membrane potentials, indicating gain of function. F302L also caused loss of KV1.2 function via accelerated inactivation onset, decelerated recovery and shifted inactivation voltage dependence to more negative potentials. These effects, which are not fully rescued by coexpression of wild-type and mutant KCNA2 subunits, probably result from the enhancement of VSD function, as demonstrated by optically tracking VSD depolarization-evoked conformational rearrangements. In turn, molecular dynamics simulations suggest altered VSD exposure to membrane lipids. Compared to other encephalopathy patients with KCNA2 mutations, the proband exhibits mild neurological impairment, more characteristic of patients with KCNA2 loss of function. Based on this information, we propose a mechanism of epileptogenesis based on enhanced KV1.2 inactivation leading to increased synaptic release preferentially in excitatory neurons, and hence the perturbation of the excitatory/inhibitory balance of neuronal circuits.
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Affiliation(s)
- Antonios Pantazis
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
- Division of Neurobiology, Department of Biomedical and Clinical Sciences (BKV), Linköping University, Linköping, Sweden
- Wallenberg Center for Molecular Medicine, Linköping University, Linköping, Sweden
| | - Maki Kaneko
- Center for Personalized Medicine, Children's Hospital, Los Angeles, Los Angeles, CA, USA
- Division of Genomic Medicine, Department of Pathology, Children's Hospital Los Angeles, Los Angeles, CA, USA
| | - Marina Angelini
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
| | - Federica Steccanella
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
| | - Annie M Westerlund
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, Solna, Sweden
| | - Sarah H Lindström
- Division of Neurobiology, Department of Biomedical and Clinical Sciences (BKV), Linköping University, Linköping, Sweden
| | - Michelle Nilsson
- Division of Neurobiology, Department of Biomedical and Clinical Sciences (BKV), Linköping University, Linköping, Sweden
| | - Lucie Delemotte
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, Solna, Sweden
| | - Sulagna C Saitta
- Department of Obstetrics and Gynecology and Division of Medical Genetics, Department of Pediatrics, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
| | - Riccardo Olcese
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
- Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
- Brain Research Institute, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
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Qiu S, Joshi PS, Miller MI, Xue C, Zhou X, Karjadi C, Chang GH, Joshi AS, Dwyer B, Zhu S, Kaku M, Zhou Y, Alderazi YJ, Swaminathan A, Kedar S, Saint-Hilaire MH, Auerbach SH, Yuan J, Sartor EA, Au R, Kolachalama VB. Development and validation of an interpretable deep learning framework for Alzheimer's disease classification. Brain 2020; 143:1920-1933. [PMID: 32357201 PMCID: PMC7296847 DOI: 10.1093/brain/awaa137] [Citation(s) in RCA: 130] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/11/2020] [Accepted: 03/06/2020] [Indexed: 12/18/2022] Open
Abstract
Alzheimer's disease is the primary cause of dementia worldwide, with an increasing morbidity burden that may outstrip diagnosis and management capacity as the population ages. Current methods integrate patient history, neuropsychological testing and MRI to identify likely cases, yet effective practices remain variably applied and lacking in sensitivity and specificity. Here we report an interpretable deep learning strategy that delineates unique Alzheimer's disease signatures from multimodal inputs of MRI, age, gender, and Mini-Mental State Examination score. Our framework linked a fully convolutional network, which constructs high resolution maps of disease probability from local brain structure to a multilayer perceptron and generates precise, intuitive visualization of individual Alzheimer's disease risk en route to accurate diagnosis. The model was trained using clinically diagnosed Alzheimer's disease and cognitively normal subjects from the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset (n = 417) and validated on three independent cohorts: the Australian Imaging, Biomarker and Lifestyle Flagship Study of Ageing (AIBL) (n = 382), the Framingham Heart Study (n = 102), and the National Alzheimer's Coordinating Center (NACC) (n = 582). Performance of the model that used the multimodal inputs was consistent across datasets, with mean area under curve values of 0.996, 0.974, 0.876 and 0.954 for the ADNI study, AIBL, Framingham Heart Study and NACC datasets, respectively. Moreover, our approach exceeded the diagnostic performance of a multi-institutional team of practicing neurologists (n = 11), and high-risk cerebral regions predicted by the model closely tracked post-mortem histopathological findings. This framework provides a clinically adaptable strategy for using routinely available imaging techniques such as MRI to generate nuanced neuroimaging signatures for Alzheimer's disease diagnosis, as well as a generalizable approach for linking deep learning to pathophysiological processes in human disease.
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Affiliation(s)
- Shangran Qiu
- Section of Computational Biomedicine, Department of Medicine, Boston University School of Medicine, Boston, MA, USA
- College of Arts and Sciences, Boston University, MA, USA
| | - Prajakta S Joshi
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, USA
| | - Matthew I Miller
- Section of Computational Biomedicine, Department of Medicine, Boston University School of Medicine, Boston, MA, USA
| | - Chonghua Xue
- Section of Computational Biomedicine, Department of Medicine, Boston University School of Medicine, Boston, MA, USA
| | - Xiao Zhou
- College of Arts and Sciences, Boston University, MA, USA
| | - Cody Karjadi
- The Framingham Heart Study, Boston University School of Medicine, Boston, MA, USA
| | - Gary H Chang
- Section of Computational Biomedicine, Department of Medicine, Boston University School of Medicine, Boston, MA, USA
| | - Anant S Joshi
- College of Computing, Georgia Institute of Technology, Atlanta, GA, USA
| | - Brigid Dwyer
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA
| | - Shuhan Zhu
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA
| | - Michelle Kaku
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA
| | - Yan Zhou
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Yazan J Alderazi
- Department of Neurology, University of Texas Health Science Center, Houston, TX, USA
- Department of Neurology, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Arun Swaminathan
- Department of Neurological Sciences, College of Medicine, University of Nebraska Medical Center, Omaha, NE, USA
| | - Sachin Kedar
- Department of Neurological Sciences, College of Medicine, University of Nebraska Medical Center, Omaha, NE, USA
| | | | - Sanford H Auerbach
- The Framingham Heart Study, Boston University School of Medicine, Boston, MA, USA
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA
| | - Jing Yuan
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - E Alton Sartor
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA
| | - Rhoda Au
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA, USA
- The Framingham Heart Study, Boston University School of Medicine, Boston, MA, USA
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA
- Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA
- Boston University Alzheimer’s Disease Center, Boston, MA, USA
| | - Vijaya B Kolachalama
- Section of Computational Biomedicine, Department of Medicine, Boston University School of Medicine, Boston, MA, USA
- Boston University Alzheimer’s Disease Center, Boston, MA, USA
- Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, USA
- Hariri Institute for Computing and Computational Science & Engineering, Boston University, Boston, MA, USA
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