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Proteomic and metabolomic signature of Dravet Syndrome. analysis in a genetic Scn1a-A1783V mouse model
Proteomic and metabolomic signature of Dravet Syndrome. analysis in a genetic Scn1a-A1783V mouse model
Dravet syndrome is a rare, severe form of pediatric epilepsy, accompanied by cognitive, behavioral and motor disturbances. Haploinsufficiency of the Scn1a gene, encoding the function of sodium channels on GABAergic neurons, has been detected in over 80 % of patients. Thus, it is considered the main cause of hyperexcitability. Albeit few drugs have received orphan drug status over the past years, pharmacoresistance remains the biggest challenge in the treatment of Dravet syndrome. Therefore, novel therapeutic strategies are urgently needed. Characterization of a novel, conditional, Scn1a-A1783V knock-in mouse model confirmed an increased seizure susceptibility, behavioral and motor alterations and thus demonstrated excellent face validity for the further investigation of Dravet syndrome. The untargeted proteomic screening displayed more pronounced changes following the onset of spontaneous seizures, dominated by the down-regulation of proteins involved in synaptic and glutamatergic signaling in the hippocampus of Dravet mice. The proteomic data was complemented by metabolome data that detected lower levels of glutamate and GABA in the hippocampus, suggesting a disturbed glutamate/GABA-glutamine cycle and an increased GABA:glutamate ratio. This can later be supported by GABAergic drugs. A comparison of proteomic data to published data from animal models of acquired epilepsies revealed common molecular alterations between genetic and acquired epilepsies comprising proteins linked with synaptic plasticity, astrogliosis and angiogenesis. Metabolomic screening of hippocampal tissue in Dravet mice showed pronounced alterations in energy metabolism and an impact of Dravet genotype on concentrations of several glycolysis and tricarboxylic acid (TCA) cycle intermediates. These changes in energy metabolism may contribute to seizure susceptibility and ictogenesis. Furthermore, they could explain the therapeutic potential of a ketogenic diet, which aims to shift energy metabolism towards a more fat-based energy supply. This diet improved the motor deficits observed in Dravet mice. Overall, the proteome and metabolome analysis in a mouse model of Dravet syndrome demonstrated complex molecular alterations in the hippocampus. Whether these alterations may contribute to hyperexcitability or, instead, represent a compensatory mechanism, will have to be confirmed by further investigations. The proteomic data indicated more complex pathophysiological mechanisms during the course of the disease, which should be considered in the management of Dravet syndrome. However, future studies investigating the functional relevance of the aforementioned molecular changes may confirm our data and provide valuable guidance on the development of novel therapeutic options.
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Miljanović, Nina
2021
English
Universitätsbibliothek der Ludwig-Maximilians-Universität München
Miljanović, Nina (2021): Proteomic and metabolomic signature of Dravet Syndrome: analysis in a genetic Scn1a-A1783V mouse model. Dissertation, LMU München: Graduate School of Systemic Neurosciences (GSN)
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Abstract

Dravet syndrome is a rare, severe form of pediatric epilepsy, accompanied by cognitive, behavioral and motor disturbances. Haploinsufficiency of the Scn1a gene, encoding the function of sodium channels on GABAergic neurons, has been detected in over 80 % of patients. Thus, it is considered the main cause of hyperexcitability. Albeit few drugs have received orphan drug status over the past years, pharmacoresistance remains the biggest challenge in the treatment of Dravet syndrome. Therefore, novel therapeutic strategies are urgently needed. Characterization of a novel, conditional, Scn1a-A1783V knock-in mouse model confirmed an increased seizure susceptibility, behavioral and motor alterations and thus demonstrated excellent face validity for the further investigation of Dravet syndrome. The untargeted proteomic screening displayed more pronounced changes following the onset of spontaneous seizures, dominated by the down-regulation of proteins involved in synaptic and glutamatergic signaling in the hippocampus of Dravet mice. The proteomic data was complemented by metabolome data that detected lower levels of glutamate and GABA in the hippocampus, suggesting a disturbed glutamate/GABA-glutamine cycle and an increased GABA:glutamate ratio. This can later be supported by GABAergic drugs. A comparison of proteomic data to published data from animal models of acquired epilepsies revealed common molecular alterations between genetic and acquired epilepsies comprising proteins linked with synaptic plasticity, astrogliosis and angiogenesis. Metabolomic screening of hippocampal tissue in Dravet mice showed pronounced alterations in energy metabolism and an impact of Dravet genotype on concentrations of several glycolysis and tricarboxylic acid (TCA) cycle intermediates. These changes in energy metabolism may contribute to seizure susceptibility and ictogenesis. Furthermore, they could explain the therapeutic potential of a ketogenic diet, which aims to shift energy metabolism towards a more fat-based energy supply. This diet improved the motor deficits observed in Dravet mice. Overall, the proteome and metabolome analysis in a mouse model of Dravet syndrome demonstrated complex molecular alterations in the hippocampus. Whether these alterations may contribute to hyperexcitability or, instead, represent a compensatory mechanism, will have to be confirmed by further investigations. The proteomic data indicated more complex pathophysiological mechanisms during the course of the disease, which should be considered in the management of Dravet syndrome. However, future studies investigating the functional relevance of the aforementioned molecular changes may confirm our data and provide valuable guidance on the development of novel therapeutic options.