Axonopathy and altered synaptic development in early hippocampal epileptogenesis of Dravet syndrome

bioRxiv (Cold Spring Harbor Laboratory)

Abstract

Abstract Dravet syndrome caused by SCN1A variants is a severe developmental epileptic encephalopathy (DEE) characterized by pharmaco-resistant epileptic seizures and progressive neurodevelopmental decline with cognitive impairment and autism-spectrum-traits. Numerous preceding studies indicate that the initial pathophysiology due to impaired Na V 1.1 function mainly derives from reduced interneuron firing leading to a network hyperexcitability (Bender et al. 2012). However, little is known how epileptogenesis and generally disease pathogenesis progress from the inborn molecular defect to infantile seizure onset. We address this question in a Dravet mouse model by comprehensive single-cell RNA sequencing and selected downstream analysis via single-cell electrophysiology, histology, live cell imaging and electron microscopy. Our data reveal a continuum of early primary (preseizure) and secondary (post-seizure onset) transcriptomic changes in various cell populations in the hippocampus. Focusing on cornu ammonis , we find a number of transcriptional pathways that are dysregulated including synaptic transmembrane adhesion molecules of the neurexin superfamily and voltage-gated ion channels. Further investigations support an ultrastructural and functional axonopathy and synaptopathy of parvalbumin interneurons. These processes precede somatic firing impairment and seizures suggesting they underlie fundamental early-phase disease mechanisms. Taken together we provide a cellularly resolved transcriptomic resource of early disease phases of Dravet syndrome and demonstrate epileptogenesis beyond Na V 1.1 loss-of-function during an early developmental time window of CNS maturation. Altogether these data establish proof-of principle that the concept of epileptogenesis, originally devised for acquired forms of epilepsy, similarly applies to genetic epilepsies and DEEs.

Authors 13

1. Nikolas Layer

   Hertie Institute for Clinical Brain Research · University of Tübingen

   Affiliation as printed

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

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

2. Peter Müller

   Hertie Institute for Clinical Brain Research · University of Tübingen

   Affiliation as printed

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

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

3. Maya Ayash

   Hertie Institute for Clinical Brain Research · University of Tübingen

   Affiliation as printed

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

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

4. Friederike Pfeiffer

   University of Tübingen

   Affiliation as printed

   Department of Neurophysiology, Institute of Physiology, University of Tübingen

   Department of Neurophysiology, Institute of Physiology, University of Tübingen, Tübingen, Germany

5. Meret Saile

   Hertie Institute for Clinical Brain Research · University of Tübingen

   Affiliation as printed

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

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

6. Fabian Klopfer

   Hertie Institute for Clinical Brain Research · University of Tübingen

   Affiliation as printed

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

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

7. Stefano Iavarone

   Hertie Institute for Clinical Brain Research · University of Tübingen

   Affiliation as printed

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

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

8. Andrea Santuy

   Hertie Institute for Clinical Brain Research · University of Tübingen

   Affiliation as printed

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

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

9. Petra Fallier‐Becker

   University of Tübingen

   Affiliation as printed

   Institute of Pathology and Neuropathology, University Tübingen

   Institute of Pathology and Neuropathology, University Tübingen, Tübingen, Germany

10. Ulrike B. S. Hedrich

    Hertie Institute for Clinical Brain Research · University of Tübingen

    Affiliation as printed

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

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

11. Holger Lerche

    Hertie Institute for Clinical Brain Research · University of Tübingen

    Affiliation as printed

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

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

12. Henner Koch Aachen Department of Epileptology, Neurology

    Universitätsklinikum Aachen · RWTH Aachen University

    Affiliation as printed

    Department of Epileptology, Neurology, RWTH Aachen University Hospital

    Department of Epileptology, Neurology, RWTH Aachen University Hospital, Aachen, Germany

13. Thomas V. Wuttke corresponding

    Hertie Institute for Clinical Brain Research · University of Tübingen

    Affiliation as printed

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

    Department of Neurosurgery, University of Tübingen

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

    Department of Neurosurgery, University of Tübingen, Tübingen, Germany