Modeling an ultra-rare epilepsy variant in wildtype mice with in utero prime editing

Generating animal models that mirror a patients seizures within clinically-useful timeframes is an important step toward advancing precision medicine for genetic epilepsies. Here we report a somatic cell genome editing approach that rapidly incorporated a patients genomic variant into mice, which developed seizures recapitulating elements of the patients pathology. This approach offers a versatile in vivo platform for clinical, preclinical, and basic research applications, including tailoring pharmacotherapy, assessing variants of uncertain significance, and screening compounds to develop drugs for rare epilepsies. As proof-of-principle, we modeled an epilepsy patient with an ultra-rare variant of the NMDA receptor subunit GRIN2A using prime editing in utero directly in the developing brain of wild-type mice. This methodology achieved high-fidelity genome editing in vivo sufficient to induce frequent spontaneous seizures without necessitating germline modification or extensive breeding. Leveraging the speed and versatility of this approach, we propose a generalizable workflow to generate bedside-to-bench animal models of individual patients within weeks. This advance holds promise for providing a cost-effective, expedient in vivo testing platform that reduces barriers to access for precision medicine, and accelerates drug development for rare and neglected neurological conditions.