title: Inter-strain heterogeneity in rat hepatic transcriptomic responses to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).
abstract: The biochemical and toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have been the subject of intense study for decades. It is now clear that essentially all TCDD-induced toxicities are mediated by DNA-protein interactions involving the Aryl Hydrocarbon Receptor (AHR). Nevertheless, it remains unknown which AHR target genes cause TCDD toxicities. Several groups, including our own, have developed rodent model systems to probe these questions. mRNA expression profiling of these model systems has revealed significant inter-species heterogeneity in rodent hepatic responses to TCDD. It has remained unclear if this variability also exists within a species, amongst rodent strains. To resolve this question, we profiled the hepatic transcriptomic response to TCDD of diverse rat strains (L-E, H/W, F344 and Wistar rats) and two lines derived from L-E×H/W crosses, at consistent age, sex, and dosing (100 μg/kg TCDD for 19 h). Using this uniquely consistent dataset, we show that the majority of TCDD-induced alterations in mRNA abundance are strain/line-specific: only 11 genes were affected by TCDD across all strains, including well-known dioxin-responsive genes such as Cyp1a1 and Nqo1. Our analysis identified two novel universally dioxin-responsive genes as well as 4 genes induced by TCDD in dioxin-sensitive rats only. These 6 genes are strong candidates to explain TCDD-related toxicities, so we validated them using 152 animals in time-course (0 to 384 h) and dose-response (0 to 3000 μg/kg) experiments. This study reveals that different rat strains exhibit dramatic transcriptional heterogeneity in their hepatic responses to TCDD and that inter-strain comparisons can help identify candidate toxicity-related genes.
authors.affiliation: Informatics and Biocomputing Platform, Ontario Institute for Cancer Research, Toronto, Canada.
authors.forename: Cindy Q
authors.initials: CQ
authors.lastname: Yao
authors.forename: Stephenie D
authors.initials: SD
authors.lastname: Prokopec
authors.forename: John D
authors.initials: JD
authors.lastname: Watson
authors.forename: Renee
authors.initials: R
authors.lastname: Pang
authors.forename: Christine
authors.initials: C
authors.lastname: P'ng
authors.forename: Lauren C
authors.initials: LC
authors.lastname: Chong
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Harding
authors.forename: Raimo
authors.initials: R
authors.lastname: Pohjanvirta
authors.forename: Allan B
authors.initials: AB
authors.lastname: Okey
authors.forename: Paul C
authors.initials: PC
authors.lastname: Boutros
mesh_terms: D000818:Animals; D003433:Crosses, Genetic; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D014644:Genetic Variation; D008099:Liver / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D008297:Male; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D051381:Rats; D011916:Rats, Inbred F344; D020318:Rats, Long-Evans; D017208:Rats, Wistar; D018336:Receptors, Aryl Hydrocarbon / Q000096:biosynthesis / Q000235:genetics; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D059467:Transcriptome / Q000187:drug effects*
chemical_list: D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D019363:Cytochrome P-450 CYP1A1; D016660:NAD(P)H Dehydrogenase (Quinone); C507703:NQO1 protein, rat