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Title	Expression of the ARNT protein in developing or juvenile rat, mouse, chicken, and rainbow trout, and functionality of rainbow trout AHR isoforms
Author	Sojka, Katherine Marks
Date	2001
Affiliation/College	College of Graduate Studies
Department	Molecular and Cellular Biology and Pathobiology
Extent	vii, 186 leaves : ill. 29 cm
Source	QH 601 S683e 2001
Subject.MeSH	Academic Dissertations Signal Transduction Hydrocarbons Aryl Hydrocarbon
Collection	MUSC Theses and Dissertations
Contributing Institution	Waring Historical Library (MUSC)
Rights	Copyright is held by the author.
Language	English
Type	Text
Format	application/pdf
Media Type	Manuscripts
Resource Identifier	mtd2001_sojka_km
Abstract	The aryl hydrocarbon receptor nuclear translocator (ARNT) is a bHLHlPAS transcription factor that serves as a central modulator responding to a range of stimuli including xenobiotic insult, developmental processes, and hypoxia. Its versatility as a dimerization partner alludes to possible involvement in undiscovered pathways. The mouse knockout model of ARNT results in an embryonic lethal phenotype at gestation day 10.5, emphasizing ARNT is vital for murine development. Given the importance of ARNT in mouse development, the goal of this research was to determine the developmental or juvenile expression of ARNT proteins in the rat, mouse, chicken, and rainbow trout to identify potentially important areas of ARNT function, as well as, provide an evolutionary perspective to ARNT signaling. Importantly, rainbow trout possess a novel mechanism for regulating ARNT function. While rtARNTb was found in all life stages, the expression of the dominant negative isofonn, rtARNTa, was restricted to the adult gill. Interestingly, the level of rtARNT protein expression was highest in two day posthatch sac fry, which is the stage most TeDD induced toxicity occurs and the point where the yolk sac vasculature expands. This ARNT expression peak and TeDn sensitivity suggests the sac fry stage may be a critical window of ARNT function in the trout. In contrast ARNT was expressed in the male rat reproductive tract at a consistent level regardless of TenD exposure or stage of development. Although it was initially thought that ARNT functions to transport the AHR into the nucleus, immunohistochemical studies revealed that ARNT resides primarily in the nucleus of embryonic mouse and chicken tissues emphasizing that this ARNT dimerization partner must enter the nucleus to complement signal transduction. Complementary studies showed that both rtAHR2 isoforms were found to act as positive regulators of promoter activity, though rtAHR2B is less potent. Importantly, rtARNTa did not complement TCDD mediated signal transduction when heterodimerizing with rtAHRa. The restricted expression of rtARNT a in the adult gill and the ubiquitous nature of rtARNT b suggests the rainbow trout is a unique model system for studying ARNT signal transduction.

Expression of the ARNT protein in developing or juvenile rat, mouse, chicken, and rainbow trout, and functionality of rainbow trout AHR isoforms

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