WWOX P47T loss-of-function mutation induces epilepsy, progressive neuroinflammation, and cerebellar degeneration in mice phenocopying human SCAR12

Abstract

WWOX gene loss-of-function (LoF) has been associated with neuropathologies resulting in developmental, epileptic, and ataxic phenotypes of varying severity based on the level of WWOX dysfunction. WWOX gene biallelic germline variant p.Pro47Thr (P47T) has been causally associated with a new form of autosomal recessive cerebellar ataxia with epilepsy and intellectual disability (SCAR12). This mutation affects the WW1 protein binding domain of WWOX, impairing its ability to interact with canonical proline-proline-X-tyrosine motifs in partner proteins. We generated a mutant knock-in mouse model of Wwox P47T that phenocopies SCAR12. WwoxP47T/P47T mice displayed epilepsy, profound social behavior and cognition deficits, and poor motor coordination, and unlike KO models that survive only for 1 month, live beyond 1 year of age. These deficits progressed with age, and mice became practically immobile, suggesting severe cerebellar dysfunction. WwoxP47T/P47T mice exhibited signs of progressive neuroinflammation with elevated astro-microgliosis that increased with age. The cerebellar cortex displayed significantly reduced molecular and granular layer thickness and a strikingly reduced number of Purkinje cells with degenerated dendrites. Transcriptome profiling from various brain regions from these Wwox LoF mice highlighted widespread changes in neuronal and glial pathways, enrichment of bioprocesses related to neuroinflammation and severe cerebellar dysfunction, activation of pathways compatible with compensatory neurogenesis along with major suppression of gene networks associated with excitability, neuronal cell differentiation and brain development. Our results show significant pathobiological effects and potential mechanisms through which WWOX LoF leads to epilepsy, cerebellar neurodegeneration, neuroinflammation, and ataxia. Additionally, the mouse model described here will be a useful tool for the study of WWOX in common neurodegenerative conditions in which it has been identified as a novel risk factor.