Finally, RAS-Rac1-PAK signaling (Fig. 2B) in neurons governs social learning in Nf1+/− mice (Molosh et al., 2014), while, in Nf1+/− mast cells, it regulates gain-of-function phenotypes relevant to neurofibroma pathogenesis (McDaniel et al., 2008). Here, NF1 is linked to plexiform neurofibroma.