Gene expression was measured using qRT-PCR on intestinal tissue from 2 week old (black) and 12 week old (blue) mice. Relative mRNA expression of the barrier-forming genes Claudin 3, Occludin, ZO-1, and JAM-A was lower in infantile tissue. Expression of the pore-forming genes Claudins 2 and 5 was higher in infantile tissue only in the proximal small intestine. Relative mRNA expression is expressed as percentage of β actin mean ± SEM (n = 6). One-way ANOVA with Tukey’s multiple comparison test; * P < 0.05, ** P < 0.01, *** P < 0.001.