Both paracellular hyperpermeability [demonstrated by abnormal TJ expression and upregulation of myosin light chain kinase (MLCK) activity (86, 322–324)] and transcellular hyperpermeability [represented by bacterial internalization to epithelia (325)] were documented in mucosal biopsies of patients with Crohn's disease and UC. The gene discussed is MYLK; the disease is Crohn disease.