Deciphering SPTAN1-associated disease mechanisms and potential therapy in patient-derived cell lines - Project Summary Developmental and epileptic encephalopathy 5 (DEE5) is a rare neurodevelopmental disorder caused by monoallelic pathogenic variants (PV) in SPTAN1, which encodes non-erythrocytic αII-spectrin. Individuals with c.6908_6916dup (p.D2303_L2305dup) and the c.6619_6621del (p.E2207del) PV experience infantile epilepsy with refractory seizures, profound developmental delay, hypotonia, and microcephaly. There is no available cure for the affected children, and the current treatment goal aims to improve quality of life. However, there remains a significant need for therapy development as multiple reports of failure to respond to anti-seizure medication have been documented. Typically, children harboring the duplication variant succumb to the disorder before 6 years of age. Previous studies in patient-derived fibroblasts and transfected mouse neurons had demonstrated a dominant-negative consequence of the variants resulting in aggregation of αII with β spectrins and a disrupted axon initiation segment based on Ankyrin G and voltage-gated sodium channel signals. However, there is a lack of connection between the molecular phenotypes and the clinical seizure phenotypes. Hence, there is a critical need to clarify the fundamental molecular factors involved and assess the cellular and biochemical properties using patient-derived cells and a mouse model to develop feasible therapy for the affected individuals. The overall goal of the proposed work is to better the understanding of the molecular consequences of DEE5 (Aim 1) and develop appropriate assays and a generalizable pipeline for screening antisense oligonucleotide (ASO) therapy that addresses the dominant-negative neurodevelopmental disorders (Aim 2). The applicant hypothesizes that the SPTAN1 PV variants aggregate with SPTBN4 at the axon initiation segment to cause aberrant action potential and thus seizures, and the wildtype protein function can be restored by knocking down the variant allele using ASO. The applicant will use lineage-appropriate patient-derived cell lines as well as develop a humanized mouse model to fully assess the disease mechanisms underlying DEE5 and will design and screen RNase-H-dependent ASOs in patient-derived cell lines to determine the effective therapeutic approach for alleviating cellular phenotypes. The proposed work serves instrumental value to the scientific community and patient families by providing an extensive understanding of SPTAN1 dominant-negative disease mechanisms, a valuable mouse model for future research, and supportive preclinical evidence for treatment development. This project is designed to prepare the applicant for a career as an independent scientist in translational research and furthers the applicant’s long-term goals of contributing to the preclinical development of rare genetic disorders affecting the central nervous system.
