This view would be in keeping with the poor segregation of changes in individual gene expression levels with TCDD sensitivity in the present study. We recently also showed that the number of dissimilar transcriptomic responses between L-E and H/W rats increases as
3-MA in vitro a function of time (Boutros et al., 2011). TCDD exposure and subsequent toxicity are an important issue that could directly affect human health. We focused our experiments on liver tissue because there is extensive hepatotoxicity in rats following exposure to TCDD. The ultimate target organ for lethality remains unknown; however, large hepatic differences exist in toxic end-points between the sensitive L-E and the resistant H/W rats, making liver a good candidate organ for involvement in systemic TCDD toxicities. The role of the AHR genotype in regard to liver toxicity is especially well demonstrated in a study conducted by Pohjanvirta, where transgenic C57BL/6 mice that express the rat wild-type isoform of the AHR SB431542 nmr showed significantly higher expression of AHR and CYP1A1 in comparison to non-transgenic mice, particularly in liver (Pohjanvirta, 2009). That study also demonstrated that liver is a major target for TCDD’s toxic effects; hence, studying differential gene expression in liver is critical to the overall
understanding of TCDD toxicity. By combining existing genetic models with microarray analysis, we have identified key novel candidate genes that are worthy of further investigation for differential expression at the protein level and ultimately in mechanistic
studies to connect altered expression to subsequent overt toxicity. The following are the supplementary materials related to this article. Supplementary Fig. 1. PCR validation of Sdc1. ABO has served as a paid consultant to the Dow Chemical Company as a member of their Dioxin Scientific Advisory Board. Other authors declare that they have no conflicts of interest. This work was supported by the Canadian Institutes of Health Research (grant number MOP-57903 to ABO and PCB), the Academy of Finland (grant number 123345 to RP), the Ontario Genomics Institute Resminostat (to CP) and with the support of the Ontario Institute for Cancer Research to PCB through funding provided by the Government of Ontario. The study sponsors had no role in the study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. The authors thank Hanbert Chen, Alexander Wu, Ashley Smith, Janne Korkalainen, Arja Moilanen, and Virpi Tiihonen for excellent technical assistance and support. We are also obliged to Dr. Jouni T. Tuomisto for providing us LnA and LnC rats.