CLDN2 and necrotizing enterocolitis: Reported alterations of apical junction complex proteins in human NEC specimen include a reduced mRNA expression of occludin [172,173], claudin-4 [173], vinculin [173] and ZO-1 [173], reduced immunoreactivity of occludin and ZO-1 in jejunum and ileum [173], increased immunoreactivity for claudin-2 in both colon and small intestine [116] and an increased protein expression and internalization of claudin-2 [174].