WWOX-related Epileptic Encephalopathy: Molecular and Functional Characteristics of Human iPSC-Derived Cerebral Organoids

The WW domain-containing oxidoreductase (WWOX) gene maps to chromosomal fragile site FRA16D and is a tumor suppressor. Recent evidence links WWOX with DNA damage response. Moreover, WWOX gene mutations were recently associated with epilepsy and ataxia in both animals and humans. WWOX-related epileptic encephalopathy (WOREE syndrome) is a devastating childhood epilepsy disorder, associated with large range of phenotypes in young ages (as young as 1.5 months). Those include global developmental delay, progressive microcephaly, bilateral optic atrophy, spastic quadriplegia, and premature death. Milder phenotypes, which include non-progressive microcephaly and spinocerebellar ataxia type-12 (SCAR12), are also observed with later onset (9-12 months). These manifestations differ also in nature of the mutation, with a pattern suggestive of genotype-phenotype correlation. The underlying molecular basis for these severe epilepsy syndromes is still lacking.

Recent advancements enable generation of cerebral organoids from human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs)- this multicellular structure recapitulate much of the morphology, physiology and complex circuitry of the developing human brain while modeling the genetic background and brain development of a specific individual. To date, almost no work has been done using human organoids from epileptic patients. We have generated cerebral organoids using SCAR12 and WOREE patients-derived iPSCs, as well as WWOX-edited hESCs. This is the first human-based model for these diseases that enable characterization of WWOX’s role in neonatal-cerebral development and epileptogenesis. Furthermore, drug screening will be performed, both for conventional anticonvulsant medications and for state-of-the-art approaches for epilepsy management, such as gene and antisense therapies.

We predict that this novel approach of characterizing the patient-specific in-vitro organoids will result in more appropriate treatment and in detailed investigations that will elucidate the underlying pathophysiology of a WWOX-specific patient’s epilepsy syndrome. Furthermore, this line of research can become a reference platform for modeling other intractable epilepsy syndromes.