Submitted to: Comparative Endocrinology International Congress Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: February 1, 2005
Publication Date: May 22, 2005
Citation: Murdock, C.A., Small, B.C., Waldbieser, G.C. 2005. Molecular cloning of channel catfish steroidogenic factor-1 and the effects of exogenous LHRH treatment on expression. Proc. XV International Conference of Comparative Endocrinology, Boston, MA. p. 101. Technical Abstract: Steroidogenic factor-1 is an orphan nuclear receptor that mediates the expression of a number of genes involved in steroidogenesis. Specifically, studies in mammals have shown that SF-1 controls the transcription of several cytochrome P450 steroidogenic enzymes (e.g., aromatase). However, the role of SF-1 in steroidogenic tissues of fish is unclear. In the current study, a 2,325 bp cDNA encoding an SF-1 homolog was isolated from channel catfish (Ictalurus punctatus) ovarian tissue using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) procedures. A putative 1,650 bp open reading frame (550 amino acid protein) was identified and compared to other published vertebrate SF-1 homologues. These data indicated I. punctatus SF-1 to be conserved with other SF-1 homologues (>68% homology), particularly within the predicted functional domains (e.g., DNA-binding motif). Tissue distribution analysis via RT-PCR showed that SF-1 was expressed in the pituitary, hypothalamus, ovary, testis, spleen, and skeletal muscle. Additional expression analyses were conducted using real-time quantitative RT-PCR (rtqRT-PCR) to measure SF-1 mRNA levels in total RNA isolated from pituitaries and ovaries of I. punctatus. SF-1 expression was quantified in I. punctatus females that received a single luteinizing hormone releasing hormone (LHRH) injection (20 ng/kg). Under these conditions, exogenous LHRH treatment did not enhance SF-1 transcript levels in either the pituitary or ovary. These data suggest that the regulation of SF-1 expression may not be directly dependent on LHRH release in I. punctatus.