Reasons for phenotypic variability of epilepsy syndromes conditioned by mutations of the Nav1.1 sodium ion channel

1. Purpose of the research / research hypothesis Epilepsy syndromes whose molecular basis are mutations of the SCN1A gene encoding the subunit and the potential-dependent Na + ion channel (Nayl.l) constitute a group of disease entities with high phenotypic variability. These include both epilepsy with a relatively mild clinical picture and catastrophic epileptic encephalopathy, e.g. Dravet syndrome. So far, the relationship between the type and location of the mutation in the SCN1A gene and the clinical picture of the observed syndrome has not been established, and in the vast majority of cases it is not known what functions of the potential-dependent Na + ion channel are disturbed in individual cases of the disease. Taking into account the variability of the clinical picture for specific mutations, even in related individuals, it can be hypothesized that the patient's phenotype (type of epileptic syndrome) is the result of a type of molecular pathology and a functional disorder of the Nayl subunit, which may be overlapped by the influence of factors modifying the final picture clinical disease. The aim of this project is to study in vitro and in vivo methods the relationship between the type of SCNIA mutation and disturbances in the function of potential-dependent Na + ion channels, and the impact of potential genetic modifiers on the clinical picture of the disease.The results will also allow to understand the individual genetic heterogeneity within the genes encoding other ion channels in patients from the Polish population and their influence on the variability of the phenotype of the analyzed epilepsy syndromes. 2. Applied research method / methodology Selected mutations of the SCNIA gene found in patients with Dravet syndrome, reconstructed in the cDNA of the SCNIA gene, will be expressed in model non-neuronal HEK tsA201 cells. The potential-dependent Na + ion currents in these cells will be investigated using voltage-clamp techniques to determine the properties of the kintic Na + ion currents found in different types of SCNIA gene mutations. Patients will be tested for excitability of peripheral nerve membranes, which will allow to demonstrate whether the Na + ion channel dysfunctions are detectable by clinical neurophysiological examination and whether the results of this study correlate with the results of voltage-clamp experiments.In order to identify factors influencing the mutation-dependent SCNIA phenotype, an analysis of the variability of genes encoding ion channels that may affect the function of the potential-dependent Na 'ion channels, and thus constitute genetic modifiers of the course of epilepsy, will be carried out using exomic next-generation sequencing. 3. Influence of the expected results on the development of science, civilization, society. The implementation of the research provided for in the project will allow to deepen the knowledge about the molecular and functional basis of genetically determined epileptic early childhood encephalopathies, in particular in the context of the transfer of molecular pathology to functional disorders of the potential-dependent Na + channel and their correlation with phenotype.