Developmental Profile of Claudin-3, Claudin-5, and Claudin-16 Tight Junction Proteins in the Chick Intestine.

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Title: Developmental Profile of Claudin-3, Claudin-5, and Claudin-16 Tight Junction Proteins in the Chick Intestine.
Author: Ozden, Ozkan
Advisors: Betty L. Black, Committee Co-Chair
Brenda J. Brizuela, Committee Co-Chair
Herbert A. Underwood, Committee Member
Abstract: Tight junction (TJ) proteins form major barriers between epithelial and endothelial cells and are responsible for regulating paracellular transport. Claudin protein family members are important structural and functional components of TJs. This study investigates, for the first time, the subcellular localization and distribution of Cla3, Cla5, and Cla16 proteins in the intestine of chick embryos during the week before hatching, and in one-day old chicks. The localizations of Cla3, Cla5, and Cla16 proteins were determined in sections of frozen and paraffin-embedded tissue from duodenum, jejunum and ileum using an immunostaining protocol. These proteins were determined during both pre-hatch and post-hatch periods in all three parts of the chick intestine, and concluded that they might not only play a role in regulating paracellular pathways, but might also play a role in normal chick intestinal development. Subcellular localization differed for each Cla protein. Cla3 expression was seen within the epithelial cell layer and in the connective tissues. It might have an adhesive role for epithelial cells to attach to each other and to basal lamina. Cla5 expression was observed strictly in the epithelial and endothelial tight junctional complexes, and its primary role might be the regulation of paracellular pathways. Mutations in Cla16 have been linked to impaired reabsorption of magnesium and calcium leading to kidney disease, and Cla16 is reported to play a role in forming aqueous pores in the paracellular pathway within Henle's loop. Interestingly, the expression of Cla16 was primarily detected in two regions of chick intestine: 1) goblet cells within the intestinal epithelium and 2) smooth muscle layers. It may play a role in the mucus secretion process in intestinal goblet cells and the Ca++ movement process in the smooth muscle fibers, possibly by creating a calcium channel subunit. Further studies are underway to elucidate the novel roles of TJ proteins in the chick intestine.
Date: 2006-01-03
Degree: MS
Discipline: Zoology

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