Sequence Variations in pxr (nr1i2) From Zebrafish (Danio rerio) Strains Affect Nuclear Receptor Function

Area of Science:

• Pharmacology and toxicology
• Environmental toxicology
• Genetics and genomics

Background:

• Regulators of biotransformation are crucial for understanding chemical metabolism, disposition, and toxicity.
• The nuclear receptor NR1I2 (pregnane X receptor, PXR) is a key xenosensor controlling the elimination of exogenous and endogenous compounds.
• Zebrafish (Danio rerio) possess a single Pxr gene locus, but genetic variants exist, though their prevalence and significance are largely unknown.

Purpose of the Study:

• To investigate sequence variations in the zebrafish Pxr gene across different strains.
• To assess the functional impact of these Pxr variants on ligand binding and gene regulation.
• To determine if Pxr variations influence the response to xenobiotics in zebrafish, a key model organism.

Main Methods:

• Sequencing of Pxr genes from four distinct zebrafish strains.
• In vitro assessment of Pxr variant responses to known ligands (clotrimazole and butyl-4-aminobenzoate).
• Reporter gene assays to measure Pxr-mediated gene expression.

Main Results:

• Identified sequence variations within the Pxr gene among the four zebrafish strains.
• Demonstrated differential binding affinities of Pxr variants to clotrimazole and butyl-4-aminobenzoate.
• Observed distinct Pxr variant abilities to regulate reporter gene expression in vitro.

Conclusions:

• Sequence variations in zebrafish Pxr genes likely affect the in vivo response to potential Pxr agonists.
• Observed Pxr variants may lead to strain-specific biotransformation of xenobiotics in zebrafish.
• The selection of zebrafish strain is a critical factor that can influence the results of toxicological studies.