Development of Claudin 2 and Claudin 4 in Embryonic and Hatched Chick Intestine

Abstract

The epithelium of the vertebrate intestine is a dynamic structure, under constant renewal. The intestinal crypts represent a proliferative compartment that is monoclonal and is maintained by multiple stem cells. Epithelial cells migrate up the villus in sheets where they differentiate into enterocytes and goblet cells. A defining characteristic of the epithelial sheets are tight junctions that behave as a primary barrier to the diffusion of solvents through the paracellular pathway in both epithelia and endothelia. This work utilized Western blotting to study the expression of two tight junction proteins, claudin 2 and claudin 4, in duodenal epithelial cells from pre- and posthatched chick intestine during development, as well as along the crypt-villus . Claudin 2 expression was stronger at 20 days of incubation than at 18 days and had the greatest expression in epithelium from 2-day old chicks. Additionally, claudin 2 was found to decrease up the crypt-villus axis in duodenal epithelium from 2-day old chicks. The claudin 2 crypt-villus axis gradient is present by 20 days of embryonic development, at the onset of crypt formation. The localization of claudin 2 in the crypts at 20 days may establish the adult pattern of tight junctions and prepare the intestine for the absorptive functions required soon after hatching. Conversely, claudin 4 was not detected in late embryonic or early posthatch duodenal epithelium. Claudin 4 was expressed in the intestinal epithelium of 3-week old chickens; its expression may be dependent on feeding or other physiological factors.

Committee Chair: Betty L. Black Committee Members: Brenda J. Grubb, James N. Petitte