Wwox deletion leads to reduced GABA-ergic inhibitory interneuron numbers and activation of microglia and astrocytes in mouse hippocampus

Abstract The association of WW domain-containing oxidoreductase WWOXgene loss of function with central nervous system (CNS) related pathologies is well documented. These include spinocerebellar ataxia, epilepsy and mental retardation (SCAR12, OMIM: 614322 ) and early infantile epileptic encephalopathy (EIEE28, OMIM: 616211 ) syndromes. However, there is complete lack of understanding of the pathophysiological mechanisms at play. In this study, using a Wwoxknockout ( WwoxKO) mouse model (2 weeks old, both sexes) and stereologicalstudies we observe that Wwoxdeletion leads to a significant reduction in the number of hippocampal GABA-ergic (γ-aminobutyric acid) interneurons. WwoxKO mice displayed significantly reduced numbers of calcium-binding protein parvalbumin(PV) and neuropeptide Y (NPY) expressing interneuronsin different subfields of the hippocampus in comparison to Wwoxwild-type (WT) mice. We also detected decreased levels of Glutamic Acid Decarboxylase protein isoformsGAD65/67 expression in Wwoxnull hippocampi suggesting lower levels of GABA synthesis. In addition, Wwoxdeficiency was associated with signs of neuroinflammation such as evidence of activated microglia, astrogliosis, and overexpression of inflammatory cytokines Tnf-a and Il6 . We also performed comparative transcriptome-wide expression analyses of neural stem cells grown as neurospheresfrom hippocampi of WwoxKO and WT mice thus identifying 283 genes significantly dysregulated in their expression. Functional annotation of transcriptome profiling differences identified ‘neurological disease’ and ‘CNS development related functions’ to be significantly enriched. Several epilepsy-related genes were found differentially expressed in WwoxKO neurospheres. This study provides the first genotype-phenotype observations as well as potential mechanistic clues associated with Wwoxloss of function in the brain.