Mice lacking Muc2 (Van der Sluis et al, 2006), Agr2 (Park et al, 2009; Zhao et al, 2010) or having mutations in Muc2 that interfere with initial mucin folding and assembly (Heazlewood et al, 2008) develop spontaneous colitis or display rectal prolapse. Here, AGR2 is linked to colitis.