Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Wednesday Speaker Abstracts

DYNAMIN-1 DYSFUNCTION IN HUMAN DISEASE

Katherine Bonnycastle 1 ; Katharine L Dobson 1 ; Marie Pronot 1 ; Elizabeth C Davenport 1 ; Moritz Steinruecke 1 ; Akshada Gajbhiye 2 ; Matthias Trost 2 ; Alfredo Gonzalez-Sulser 1 ; Michael A Cousin 1 ; 1 University of Edinburgh, Center for Discovery Brain Sciences, Edinburgh, United Kingdom 2 Newcastle University, Faculty of Medical Sciences, Newcastle, United Kingdom The large GTPase dynamin-1 has an obligatory role in the endocytosis of synaptic vesicles (SVs) at mammalian nerve terminals. In recent years, pathogenic heterozygous missense mutations in the gene that encodes dynamin-1, DNM1, have been shown to result in a novel form of epileptic encephalopathy. Intriguingly, DNM1 mutations cluster within regions required for its essential GTPase activity, implicating disruption of its enzyme activity as being central to this disorder. Our objective was to determine how dynamin-1 dysfunction may result in epileptic encephalopathy, therefore we investigated the most prevalent pathogenic mutation of DNM1, R237W. We determined that this mutation disrupts dynamin-1 enzyme activity in vitro and inhibited SV endocytosis when overexpressed in primary cultures of wild-type neurons. To discover how this dominant-negative heterozygous mutant impacted cell, circuit and behavior when expressed from its endogenous locus, we generated a mouse carrying the R237W mutation. Cultured neurons isolated from heterozygous mice displayed dysfunctional SV endocytosis, and furthermore altered excitatory neurotransmission and seizure-like phenotypes. Therefore the Dnm1 +/R237W mouse provides an excellent opportunity to determine 1) the molecular and circuit basis of epileptogenic mechanisms and 2) whether SV endocytosis is a viable therapeutic route for monogenic intractable epilepsies.

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