Ectopic Overexpression of Glycine Transporter 2 Contributes to the Epileptogenesis in DEPDC5-related Epilepsies
Abstract number :
3.018
Submission category :
1. Basic Mechanisms / 1B. Epileptogenesis of genetic epilepsies
Year :
2025
Submission ID :
791
Source :
www.aesnet.org
Presentation date :
12/8/2025 12:00:00 AM
Published date :
Authors :
Presenting Author: Rajat Benerjee, PhD – University of Michigan
Tao Yang, PhD – University of Michigan
Mi Jiang, MD – University of Michigan
Mirte Scheper, Ph.D. – Amsterdam UMC
Eleonora Aronica, Ph.D. – University of Amsterdam UMC
Yu Wang, MD. Ph.D. – University of Michigan
Rationale: Loss-of-function mutations in DEPDC5, the critical negative MTOR regulator, are the most common cause of familial focal epilepsies with or without FCDII. Because most patients don’t respond to anti-seizure medications and often are not surgical candidates for destructive lesionectomy, there is an urgent need to understand its cellular and molecular mechanisms for novel therapeutic development.
Methods: We took advantage of a highly clinically relevant rat model of DEPDC5-related epilepsies and resected human patient tissues to profile the cellular and molecular architectures. We then used transgenic animals and CRISPR-IUE to knock out the two most overexpressed genes in the dysplastic cortex, complement 3 (C3) and Slc6a5, respectively, to investigate their role in epileptogenesis.
Results: The dysplastic cortex showed extensive astrogliosis, microgliosis, and excessive synaptic phagocytosis. However, mutant neurons received significantly more inhibitory synapses and fewer excitatory synapses compared to wild-type neurons. Genes related to neuroinflammation and synaptic pruning, particularly complement C1 and C3, were prominently upregulated in the whole lysates and synaptosome fraction of the dysplastic cortex. However, a novel C3 knockout rat did not improve the seizure outcome. Interestingly, Slc6a5, a marker gene for inhibitory neurons encoding glycine transporter 2 (GLYT2) in the hindbrain and spinal cord, modulating neuronal excitability, is ectopically over-expressed in mutant excitatory neurons. Using CRISPR-IUE to simultaneously knock out Depdc5 and Slc6a5 in forebrain excitatory neurons shortened the seizure duration and frequency.
Conclusions: The logic of cellular and molecular networks underlying DEPDC5-related epilepsies is complex. C3 overexpression results in a sustained local neuroinflammatory microenvironment in the dysplastic cortex but may not drive epileptogenesis and cortical hyperexcitability. The ectopically overexpressed Slc6a5 in excitatory mutant neurons, on the other hand, plays an important role in seizure severity, although the underlying mechanisms are not clear.
Funding: R01 NS113824
Basic Mechanisms