Developmental epileptic encephalopathies (DEEs) are severe genetic disorders in infants and children, marked by persistent, drug-resistant seizures and profound physical and cognitive impairments. Despite the identification of numerous DEE-associated genes, functional studies in animal or cell models are lacking for the majority of DEE which hinders the understanding of the common pathways involved in DEE development. To bridge this gap, this study developed a high-throughput DEE model using CRISPR/Cas9-mediated loss-of-function in Xenopus laevis tadpoles, aiming to elucidate the role of gene mutations in spontaneous seizure occurrence and abnormal brain signalling.

Focusing on DEE75, caused by de novo mutations in the NEUROD2 gene, it was observed that CRISPR/Cas9-edited NeuroD2.S tadpoles exhibited heightened activity, faster swimming, and increased seizure frequency compared to controls. Live brain calcium imaging revealed prolonged, intense signals indicative of neuronal hyperactivity, and the crispants also showed a compromised blood-brain barrier (BBB) ¹.

Additionally, recent research highlighted neuroinflammation (NI) as a contributing factor in seizure severity, suggesting a promising therapeutic target. The study utilized repurposed anti-inflammatory drugs (AIDs) to target NI in this model. The findings indicate that pathogenic variants lead to abnormal neuronal signalling and chronic seizures, resulting in sustained NI. Specifically, the TGF-β antagonist Losartan demonstrated a protective effect, reducing seizure events and neuronal hyperactivity, and temporarily improving BBB permeability.

These results support a model where diminished NeuroD2 activity during brain development contributed to DEE75 pathogenesis. Moreover, they suggest that targeting NI with AIDs like Losartan present a novel therapeutic strategy for managing intractable seizures in DEEs.