Meeting Abstract

P1.131  Monday, Jan. 4  Identifying Pathways of Thyroid Hormone Production in the Parrotfish Thyroid Gland JOHNSON, K.M.*; LEMA, S.C.; Univ. of North Carolina, Wilmington; Univ. of North Carolina, Wilmington kmj5818@uncw.edu

The physiological and behavioral functions of thyroid hormones have been studied extensively at the organismal level in teleost fish. However, considerably less is known about the mechanisms of thyroid hormone production at the level of the thyroid tissue. Teleost fish typically possess thyroid follicles scattered throughout the branchial region, rather than the single compact thyroid gland characteristic of most vertebrates. This anatomical arrangement of thyroid follicles has restricted study of how thyroid hormones are synthesized and released in teleost fish. A few taxonomic groups of teleosts do, however, possess a discrete thyroid glandular tissue. We have recently begun examining mechanisms of thyroid regulation in the thyroid gland tissue of one of these groups of fishes, the sex-changing parrotfish (family Scaridae). The goals of this research are: 1) to identify mRNAs encoding proteins in key steps of thyroid hormone synthesis in the follicles, and 2) to examine regulation of these gene transcripts – as well as mRNAs encoding thyroid hormone receptors and deiodinase enzymes – by thyroid hormones. We recently identified two sections of coding region for a thyroglobulin cDNA from the thyroid gland of princess parrotfish (Scarus taeniopterus). These cDNAs consist of a 296 bp nucleotide sequence that encodes 98 amino acids that shares 46.9% homology, and a 377 bp sequence encoding 125 amino acids with 55.3% homology, to human thyroglobulin. This is one of the first descriptions of a thyroglobulin cDNA from a teleost, and the identification of thyroglobulin and cDNAs for other proteins involved in thyroid hormone synthesis will permit new investigations into how thyroid hormone production in teleosts is regulated at the level of the thyroid tissue.