Cloning and expression pattern of peroxisome proliferator-activated receptor α in the thicklip grey mullet Chelon labrosus

Aquatic organisms living in coastal and estuarine areas are exposed to diverse contaminants which can cause peroxisome proliferation. Peroxisome proliferators are agonists of peroxisome proliferator-activated receptors (PPARs), members of the nuclear receptor superfamily. We have recently demonstrated expression of the three PPAR isoforms in liver of mullet Chelon labrosus and other fish species by immunohistochemistry. The goal of the present study was first to clone PPARα and second to investigate its expression pattern in various tissues of mullet. PCR-based screening of mullet cDNA with PPARα specific degenerate primers resulted in amplification, subcloning and sequencing of a 1090 bp cDNA fragment (AY618315) that encodes mullet PPARα and exhibits highest amino acid identity to fish Sparus aurata PPARα (90%). Semi-quantitative RT-PCR was used to characterize the expression of PPARα in brain, muscle, liver, spleen, gill, heart and female gonad of juvenile and adult male and female mullet. For this, mullet 18S-rRNA (AY825252), β-actin (AY836368) and elongation factor α (AY836369) were cloned and used as internal reference for RT-PCR. Expression of PPARα was detected in all tissues, was highest in liver and lowest in adult male and female muscle.