MAPK1 and RASopathy: We found that ERK2 gain-of-function is sufficient to produce a core set of central nervous system cellular, histological, and functional phenotypes observed in Rasopathy mouse models with upstream mutations: oligodendrocyte lineage defects, reactive astrocytosis, deficits in hippocampus-dependent spatial learning, and increased reactivity to arousing sensory stimuli, such as looming visual threats.