Ectopically overexpressed glycine transporter 2 contributes to epileptogenesis in DEPDC5-related epilepsy

Loss-of-function mutations in DEPDC5 (DEP domain-containing protein 5), a critical negative regulator of mTORC1 (mechanistic Target of Rapamycin Complex 1), are often identified in patients with refractory epilepsy. To understand its underlying pathogenesis and develop novel therapeutics, we used a highly clinically relevant rat model of DEPDC5-related epilepsy and resected human patient tissues to profile the molecular architecture in the dysplastic cortex. We report here that Slc6a5 (solute carrier family 6 member 5 gene), a marker gene for glycinergic inhibitory neurons, is ectopically overexpressed in mutant excitatory neurons in both experimental animal and human tissues. Using CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) in utero electroporation (IUE) to simultaneously knock out Depdc5 and Slc6a5 in forebrain excitatory neurons reduces seizure frequency and duration. These data suggest that SLC6A5 plays an important role in the epileptogenesis of DEPDC5-related epilepsy, although the underlying mechanisms remain unclear.