Observed claudin-1 and claudin-3 expression along the whole length of colonocyte basolateral membrane is in line with previous reports in healthy human colon mucosa and IBD, as well as in mice (Prasad et al., 2005; Guttman et al., 2006; Barrmeyer et al., 2015; Hagen, 2017). Here, CLDN1 is linked to inflammatory bowel disease.