Abstracts

Rationale: Developmental epileptic encephalopathy-28 (DEE28, OMIM 616211), also known as WWOX-related epileptic encephalopathy (WOREE) syndrome is caused by human germline biallelic mutations in WW domain-containing oxidoreductase (WWOX). DEE28 is a neurodevelopmental disorder characterized by intractable epilepsy, severe developmental delay, ataxia and premature death at the age of 2-4 years. The underlying mechanisms of WWOX actions in DEE-28 development are poorly understood.

Methods: Using genetic mouse modeling and patient-derived induced-pluripotent stem cells (iPSCs) and brain organoids, we studied WWOX in brain homeostasis and in its loss of function in DEE-28/WOREE syndrome. WWOX restoration was achieved using an adeno-associated viral vector (AAV9) harboring human WWOXcDNA and driven by the human neuronal Synapsin I promoter (AAV9-SynI-WWOX).

Results: We demonstrated that specific neuronal deletion of murine Wwox produces phenotypes typical of the Wwox-null mutation leading to brain hyperexcitability, intractable epilepsy, ataxia and postnatal lethality. The phenotypes of this mouse model closely resembled that of WOREE patients. In-depth characterization of these mice revealed a major myelination defect that results in reduced maturation of oligodendrocytes, reduced myelinated axons and impaired axonal conductivity. Brain hyperexcitability as well as dramatic cellular and molecular CNS abnormalities, including neural population changes, cortical differentiation malfunctions, and Wnt-pathway and DNA-damage response impairment were also revealed in human unpatterned brain organoids derived from CRISPR-engineered human ES cells and from patient-derived iPSCs. Furthermore, we provide a proof-of-concept that ectopic WWOX expression, using AAV9-SynI-WWOX, could rescue these phenotypes.

Conclusions: Our findings underscore the utility of modeling childhood epileptic encephalopathies using genetically engineered mouse models and brain organoids and their use as a unique platform to test possible therapeutic intervention strategies.

Funding: Please list any funding that was received in support of this abstract.: The Aqeilan’s lab is funded by the European Research Council (ERC) [No. 682118], Proof-of-concept ERC grant [No. 957543] and research agreement support from Mahzi Therapeutics.