“…Since its original discovery as a novel interactor of the small GTPase Rap1 ( Serebriiskii et al, 1997 ), as well as being the major protein involved in the pathogenesis of the human genetic disease CCM ( Laberge-le Couteulx et al, 1999 ; Sahoo et al, 1999 ), KRIT1 has progressively emerged as a key player in fundamental cellular functions, including control of cell–matrix and cell–cell adhesion ( Glading et al, 2007 ; Zhang et al, 2001 ), Rho GTPase activity and actin cytoskeleton dynamics ( Stockton et al, 2010 ), intracellular redox homeostasis and signaling ( Antognelli et al, 2018a , b ; Cianfruglia et al, 2019 ; Goitre et al, 2010 , 2014 ), and autophagy ( Marchi et al, 2015 ). The pleiotropic functions of KRIT1 have been clearly implicated in the maintenance of endothelial cell homeostasis and blood-brain barrier integrity through the control of coordinated molecular and cellular responses to oxidative stress and inflammation, which in turn suggest novel mechanisms of CCM disease onset and severity, providing new preventive and therapeutic perspectives ( Antognelli et al, 2020 ; Choquet et al, 2016 ; De Luca et al, 2018 ; Finetti et al, 2020 ; Gibson et al, 2015 ; Goitre et al, 2017 ; Kim et al, 2020 ; Marchi et al, 2016 ; Perrelli et al, 2018 ; Retta and Glading, 2016 ; Trapani and Retta, 2015 ). On the other hand, recent evidence demonstrates that the consequences of KRIT1 loss-of-function mutations extend beyond the pathogenesis of CCM disease, being also implicated in the development of aortic endothelial dysfunction and atherosclerosis ( Vieceli Dalla Sega et al, 2019 ), as well as of epithelial barrier dysfunction in the gastrointestinal tract ( Wei et al, 2020 ).…”