| Summary: | Background & Aims: Congenital tufting enteropathy (CTE) is an intractable diarrheal disease of infancy caused by mutations of epithelial cell adhesion molecule (EpCAM). The cellular and molecular basis of CTE pathology has been elusive. We hypothesized that the loss of EpCAM in CTE results in altered lineage differentiation and defects in absorptive enterocytes thereby contributing to CTE pathogenesis. Methods: Intestine and colon from mice expressing a CTE-associated mutant form of EpCAM (mutant mice) were evaluated for specific markers by quantitative real-time polymerase chain reaction, Western blotting, and immunostaining. Body weight, blood glucose, and intestinal enzyme activity were also investigated. Enteroids derived from mutant mice were used to assess whether the decreased census of major secretory cells could be rescued. Results: Mutant mice exhibited alterations in brush-border ultrastructure, function, disaccharidase activity, and glucose absorption, potentially contributing to nutrient malabsorption and impaired weight gain. Altered cell differentiation in mutant mice led to decreased enteroendocrine cells and increased numbers of nonsecretory cells, though the hypertrophied absorptive enterocytes lacked key features, causing brush border malfunction. Further, treatment with the Notch signaling inhibitor, DAPT, increased the numbers of major secretory cell types in mutant enteroids (graphical abstract 1). Conclusions: Alterations in intestinal epithelial cell differentiation in mutant mice favor an increase in absorptive cells at the expense of major secretory cells. Although the proportion of absorptive enterocytes is increased, they lack key functional properties. We conclude that these effects underlie pathogenic features of CTE such as malabsorption and diarrhea, and ultimately the failure to thrive seen in patients.
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