Novel AAV mediated RNA editing treatment for Dravet Syndrome.

Dravet syndrome (DS) is a severe childhood epilepsy which leads to life-long disability. The disease becomes apparent in the first year of life, where babies present severe seizures (spontaneous & hyperthermia induced seizures), followed by developmental delay, behavioural, cognitive, and motor impairment and in some cases premature death. Approximately 90% of patients exhibit a spelling mistake, or mutation, in the genetic code of the SCN1A gene leading to loss-of-function of the voltage-gated sodium channel, Nav1.1. This channel is present in brain cells and allow normal firing patterns between these cells. The affected brain cells which contain the mutated Nav1.1 channel, results in abnormal firing. Thus, the disease manifests. Current treatments for Dravet syndrome are inadequate and ineffective.

The process of making proteins in cells involves translating DNA (the genetic code) into RNA (the protein code) which is then made into proteins such as the Nav1.1 channel. We aim to develop a novel RNA editing therapy treatment for Dravet Syndrome, altering the protein code so more protein is made. Our approach involved delivering our RNA editing therapy using a virus called adeno-associated virus (AAV), to increase the healthy SCN1A gene expression and therefore restore the Nav1.1 function. We aimed to test this novel treatment in a DS mouse model. The DS mouse model, like the human DS patients, contain one functional gene and one-non-functional gene and show clinically relevant phenotypes such as, spontaneous seizures, hyperthermia induced seizures, behavioural abnormalities, and premature death.

We developed 21 novel RNA editing sequences, of which 5 sequences showed to significantly increase healthy Scn1a (mouse gene equivalent) expression in cells. We selected two novel RNA editing sequences and produced AAV viral vector to test in the DS mouse model. The AAV gene therapy was delivered directly to the brain and systemically in the blood stream to new-born DS...