Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2007
Publication Date: 1/2/2008
Citation: Lynn, S.G., Birge, W.J., Shepherd, B.S. 2008. Molecular Characterization and Sex-Specific Tissue Expression of Estrogen Receptor Alpha (esr1), Estrogen Receptor Beta-a (esr2a) and Ovarian Aromatase (cyp19a1a) in Yellow Perch (Perca flavescens). Comparative Biochemistry and Physiology, Part B. 149:126-147. Interpretive Summary: Yellow perch have a high commercial value in the Great Lakes Regions and have (historically) comprised the largest inland fishery in the U.S. Consequently, improvements in growth and feed efficiency are of considerable importance to the U.S. perch industry since improved production efficiency would improve global competitiveness and food safety, in part, by decreasing imports of lesser quality Eurasian perch species. The yellow perch exhibits a sexual size dimorphism (SSD) wherein females grow faster than males. Studies have identified that the female sex steroid, 17?-estradiol (E2), is a growth stimulator in yellow perch, but the growth promoting effects of E2 were only noticeable in fish of 80-110 mm total length or greater. This critical size range is also the specific minimum body size for the onset of sexual maturity in females and males. This is also the period when females normally begin to outgrow males and a female-biased SSD begins to be manifested, pointing towards an upregulation of E2 receptors (ERs) on target tissues (ovary, liver or pituitary) and a coinciding increase in tissue expression of growth-regulatory factors. These studies point out a clear linkage of growth and reproductive development in this species and suggest the presence of an intricate, sex-specific regulatory relationship between growth factors and E2. In an effort to gain more understanding into the yellow perch E2 stimulated SSD, the cDNAs for genes that encode for hormones that are involved with the endocrine growth axis (GH, PRL, SL and IGF-I) have been recently cloned and characterized. In this current paper, we have cloned and sequenced the full length cDNAs for ER?, ER?a, and aromatase (CYP19A1) and examined the sex-specific tissue expression of these. Development of these molecular tools will enable us to understand their involvement in commercially-important physiological traits. Application of this knowledge in a selective breeding program should lead to improvements in yellow perch production efficiency.
Technical Abstract: Yellow perch (Perca flavescens) exhibit an estrogen-stimulated sexual size dimorphism (SSD) wherein females grow faster and larger than males. To aid in the examination of this phenomenon, the cDNA sequences encoding estrogen receptor-alpha (esr1), estrogen receptor-beta-a (esr2a) and ovarian aromatase (cyp19a1a) for the yellow perch were obtained. Several tissues were analyzed from both male and female adult yellow perch for sex-specific tissue expression. The full length cDNAs of yellow perch esr1, esr2a and cyp19a1a consist of 3052 bp, 2462 bp and 1859 bp with open reading frames encoding putative proteins of 576 amino acids, 555 amino acids and 518 amino acids, respectively. Esr1 and esr2a expression was highest in female ovary and liver tissues with low to moderate expression in other tissues. Esr2a showed a more global tissue expression pattern than esr1, particularly in males but also in females. Cyp19a1a expression was highest in both male and female spleen tissue and oocytes with moderate expression in male pituitary and gill tissue. Cyp19a1a expression was moderately high in female liver tissue with undetectable expression in male liver tissue, suggesting its involvement in sexually dimorphic growth. These sequences are valuable molecular tools that can be used in future studies investigating estrogen mechanisms and actions, such as SSD, in yellow perch.