Date of Graduation

5-2015

Document Type

Thesis

Degree Name

Master of Science in Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor

Michelle Evans-White

Committee Member

Steven Beaupre

Second Committee Member

Charles Rosenkrans

Keywords

Biological sciences; Claudin; Gills; Osmoregulation; Rainbow trout; Tight junction

Abstract

Claudin proteins, a key element of tight junction complexes, are known to control paracellular permeability. In euryhaline fish, changes in claudin abundance and localization are critical during salinity acclimation. In seawater, a leaky paracellular pathway that facilitates sodium extrusion is hypothesized to be controlled by claudin proteins. The aim of this study was to evaluate the role of Claudin-10c, -10d -10e and Claudin-30 in gill function in freshwater (FW) and seawater (SW) rainbow trout (Oncorhynchus mykiss). I examined mRNA and protein abundance along with cellular localization. A tissue distribution survey showed that all of the claudins studied were predominantly expressed in gill tissue. Transcript and protein expression of Claudin-10s was significantly up-regulated after SW transfer, while no difference in Claudin-30 expressions was observed. In accordance with these expression patterns, in silico prediction showed that Claudin-10s could form cation-selective pores and thus be critical to sodium secretion in SW. Claudin-30 is known as a resistance forming claudin and its insensitivity to salinity suggests an epithelial barrier function in both FW and SW gills. In addition, immunofluorescence microscopy revealed that Claudin-10s are localized in association with the ionocytes in SW. Expression of Claudin-30 was restricted to intermediate cells on the gill filament. This study also suggest that claudins expression may be influenced by combination of both genetic and environmental factors.

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