ARF6 and cyst: Furthermore, it has been reported that in 3D Matrigel culture, MDCK cells depleted of the small GTPase Arf6 form an inverted cyst, whose inversion is restored by epidermal growth factor‐elicited Rac1 activation and by expression of a constitutively active form of Rac1 (Monteleon et al., 2012).