Aromatic Hydrocarbon Receptor Polymorphism: Development of New Methods to Correlate Genotype with Phenotype

Abstract

Differential CYPlAl inducibility, reflecting variations in aromatic hydrocarbon receptor (AHR) affinity among inbred mouse strains, is an important determinant of environmental toxicity. We took advantage of the Air polymorphism in C57BL16 and DBA/2 mice to develop an oligonudeotide-hybridization screening approach for the rapid identification of DNA sequence differences between Air alleles. Oligonudeotides containing single-base changes at polymorphic sites were immobilized on a solid support and hybridized with C57BL/6 or DBA/2 AHR cDNA radiolabeled probes. The observed hybridization patterns demonstrate that this approach can be used to detect nudeotide differences in the Air coding region with very high accuracy. In parallel experiments, we used a yeast two-hybrid system to assess phenotypic differences in AHR function. AHR activation, as measured by 13-galactosidase reporter activity in Saceharomyces cerevisiae strain SFY526, was determined following treatment with varying doses of the AHR ligand P-naphthoflavone (BNF (9). Ahr nucleotide differences, and corresponding AHR amino-acid changes between the C57BL/6 (B6) and DBA/2 (D2) mouse strains that carry the AhA'-1 and Ahkd alleles, respectively, have been studied extensively (9-15). An A375V change has been reported to confer most of the observed phenotypic differences between B6 and D2 (15). With hepatic cytosol from B6 and D2 mice, ligand-affinity differences were found to range between 4-and 10-fold for the B6 and D2 AHRs (1618, whereas ligand-affinity differences range between 2-and 6-fold for the B6 and D2 AHRs when cDNA-expressed AHRs are studied (9,15 (15,22,

Vessel tortuousity and reduced vascularization in the fetoplacental arterial tree after maternal exposure to polycyclic aromatic hydrocarbons

“…We have also observed disparities in the degree of growth restriction between two mouse strains, C57Bl6 and CD1, given the identical PAH treatment regimen (13,14). These differences may be due to AhR, which is highly polymorphic among mouse strains (28) and mediates the effects of PAH on fetal growth (14). The current study used an inbred strain to control for genetic variability.…”

Electrophilic tissue burden in male Sprague-Dawley rats following repeated exposure to binary mixtures of polycyclic aromatic hydrocarbons

“…2 Correlation between electrophilic tissue burden (ETB) levels in lung and in haemoglobin (Hb), measured as benzo(a)pyrene diolepoxide (BaPDE) adducts, following intraperitoneal administration of binary mixture of benzo(a)pyrene (BaP) and pyrene (P) in three doses of BaP for all of the three BaP/P ratios. Each data point represents an individual animal (n=36) lytical variability, this could be related to the genetic polymorphism of CYP450 and/or other enzymes of phase I and phase II, extensively studied in rodent and humans (Hirvonen 1995;Maier et al 1998;Pastorelli et al 1998), on the one hand, and/or to the poor absorption of BaP from the peritoneal cavity, on the other hand. This latter statement relates to our experimental observation of residual oil traces in the peritoneal cavity found in some animals at the time of sacrifice.…”

Identification and Functional Characterization of Two Highly Divergent Aryl Hydrocarbon Receptors (AHR1 and AHR2) in the TeleostFundulus heteroclitus

“…Within this ligand-binding domain, FhAHR1 and FhAHR2 share 79 and 61% amino acid identity, respectively, with the human AHR. Previously, residue 375 of the murine AHR has been identified as a site where a A 3 V change results in a 4-fold decrease in binding affinity (52)(53)(54). The equivalent residues in Fundulus AHR1 and AHR2 are alanine (Ala 376 and Ala 373 , respectively), as in the high affinity mouse AHR b-1 allele.…”