ARHGAP15 and Huntington disease: Of note, loss of Arhgap15 gene, a member of the Rac signaling pathway, was shown to cause decreased synaptic density and cognitive deficits in mouse and its mutations were identified in association with neurological and cognitive deficits in patients with Intellectual Disability (Zamboni et al., 2018), revealing the rescue of its expression by HDACi treatment as potentially therapeutically relevant in HD.