Autism-like phenotypes and increased NMDAR2D expression in mice with KDM5B histone lysine demethylase deficiency

Loss-of-function mutations in genes encoding lysine methyltransferases (KMTs) and demethylases (KDMs) specific for trimethylated of lysine 4 of histone 3 (H3K4me3) are associated with neurodevelopmental conditions, including autism spectrum disorder and intellectual disability. To study the role of KDM5B (Lysine DeMethylase-5B)-mediated H3K4me3 demethylation, we investigated neurodevelopmental phenotypes in mice without KDM5B demethylase activity. These mice exhibited autism-like behaviours and increased brain size. H3K4me3 levels and the expression of neurodevelopmental genes were increased in the developing Kdm5b mutant neocortex. These included elevated expression of Grin2d. The Grin2d gene product NMDAR2D was increased in synaptosomes isolated from the Kdm5b-deficient neocortex and treating mice with the NMDAR antagonist memantine rescued deficits in ultrasonic vocalisations and reduced repetitive digging behaviours. These findings suggest that increased H3K4me3 levels and associated Grin2d gene upregulation disrupt brain development and function, leading to socio-communication deficits and repetitive behaviours, and identify a potential therapeutic target for neurodevelopmental disorders associated with KDM5B deficiency.