CATFISH GENETICS, BREEDING, AND PHYSIOLOGY
Location: Catfish Genetics Research
Title: IN VIVO AND IN VITRO CYP1B MRNA EXPRESSION IN CHANNEL CATFISH
Submitted to: Marine Environmental Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 22, 2005
Publication Date: June 26, 2005
Citation: Willett, K.L., Ganesan, S., Patel, M., Metzger, C., Quiniou, S.M., Waldbieser, G.C., Scheffler, B.E. 2005. In vivo and in vitro cyp1b mrna expression in channel catfish. Marine Environmental Research.
Interpretive Summary: Polycyclic aromatic hydrocarbons (PAH) can be oxidized into carcinogenic metabolites by cytochrome P450 1B (CYP1B). In order to develop an assay for these chemicals in water environments, the CYP1B gene was identified in channel catfish. Experimental exposure to PAH revealed increased CYP1B gene expression in catfish tissues and cultured cells. Expression of the CYP1B gene in catfish may be useful in environmental monitoring to detect exposure to polyaromatic hydrocarbons in an aquatic environment.
Our goal was to study the induction of CYP1B mRNA expression in channel catfish (Ictalurus punctatus). CYP1B belongs to the cytochrome P450 superfamily of genes, is involved in the oxidation of endogenous and exogenous compounds, and could potentially be a useful biomarker in fish for exposure to AhR ligands. The full-length catfish CYP1B cDNA is 2417 nt to the polyA tail and encodes a putative protein of 536 amino acids. It has 67% amino acid similarity to carp and zebrafish CYP1B and 68% similarity to carp CYP1B2. Male channel catfish were collected from three Mississippi Delta sites: Lake Roebuck, Itta Bena; Bee Lake, Thornton; and Sunflower River, Indianola. Total RNA was isolated from wild-caught catfish gill, blood, gonad and liver tissues. Quantitative real-time reverse transcriptase PCR was used to determine relative induction of CYP1B in wild catfish compared to laboratory control and BaP-exposed catfish (20 mg/kg i.p. after 4 days). BaP exposure significantly induced CYP1B message in blood, gonad, and liver of laboratory catfish whereas CYP1B message in wild catfish was not statistically increased relative to laboratory control catfish. This was consistent with relatively low sediment contaminant concentrations at the sampling sites. CYP1B transcript abundance was higher in gills compared to other tissues in both laboratory and wild catfish. When primary cultured gill cells were treated with increasing concentrations of BaP, TCDD, and PCBs 77, 126 and 169, CYP1B mRNA was induced more than 10-fold while PCB153 and DDT did not cause significant CYP1B induction. Our results suggest that catfish CYP1B is induced by the classic AhR ligands.