CELL SPECIFIC REGULATION OF PATHOLOGICAL NEURONAL ACTIVITY IN A MODEL OF FOCAL CORTICAL DYSPLASIA

Focal cortical dysplasia (FCD) is one of the main causes of drug resistant epilepsy. It is induced by somatic mutations of proteins involved in the mTOR signaling pathway. Our optogenetic experiments showed that specific activation of neurons bearing mTORp.L2427P mutation resulted in seizure induction in mouse model of FCD II. This suggests important role of these neurons in ictogenesis and their therapeutic potential for gene therapy approaches. To decrease activity of the mutated neurons we induced expression of inhibitory receptors hM4Di by in utero electroporation (IUE) of mTORp.L2427P and cre-recombinase into hM4Di mouse line. IUE of cre recombinase into neural precursors induced broad expression of hM4Di in neuronal and glial populations within the lesion. Activation of hM4Di by deschloroclozapine (DCZ) caused aggravation of seizures, possibly due to increased glutamate release from astrocytes activated by the hM4Di. WT animals electroporated with mTORp.L2427P and cre-recombinase plasmids were then transduced with hM4Di gene to improve its cell specific expression. DCZ application slightly decreased seizure frequency and duration. The low efficacy could be caused by desensitization of the hM4Di. To avoid unwanted hM4Di properties, excitatory neurons were transduced using voltage-activated potassium channel Kv1.1 that limits neuronal spiking activity. Resulting sparse expression of Kv1.1 within the epileptic tissue did not substantially decrease ictal activity. Our results show that sparse expression of inhibitory receptors or potassium ion channels is not sufficient to reduce epileptic activity in mouse model of FCD II and suggest a need to control the majority of excitatory neurons in epileptic tissue.