Project description:The constitutive androstane receptor (CAR) and the pregnane X receptor (PXR) are closely related nuclear receptors involved in drug metabolism and play important roles in the mechanism of phenobarbital (PB)-induced rodent nongenotoxic hepatocarcino- genesis. Here, we have used a humanized CAR/PXR mouse model to examine potential species differences in receptor-dependent mechanisms underlying liver tissue molecular responses to PB. Early and late transcriptomic responses to sustained PB exposure were investigated in liver tissue from double knock-out CAR and PXR (CARKO -PXRKO ), double humanized CAR and PXR (CARh - PXRh), and wild-type C57BL/6 mice. Wild-type and CARh-PXRh mouse livers exhibited temporally and quantitatively similar tran- scriptional responses during 91 days of PB exposure including the sustained induction of the xenobiotic response gene Cyp2b10, the Wnt signaling inhibitor Wisp1, and noncoding RNA biomarkers from the Dlk1-Dio3 locus. Transient induction of DNA replication (Hells, Mcm6, and Esco2) and mitotic genes (Ccnb2, Cdc20, and Cdk1) and the proliferation-related nuclear antigen Mki67 were ob- served with peak expression occurring between 1 and 7 days PB ex- posure. All these transcriptional responses were absent in CARKO- PXRKO mouse livers and largely reversible in wild-type and CARh - PXRh mouse livers following 91 days of PB exposure and a subse- quent 4-week recovery period. Furthermore, PB-mediated upregu- lation of the noncoding RNA Meg3, which has recently been associ- ated with cellular pluripotency, exhibited a similar dose response and perivenous hepatocyte-specific localization in both wild-type and CARh-PXRh mice. Thus, mouse livers coexpressing human CAR and PXR support both the xenobiotic metabolizing and the proliferative transcriptional responses following exposure to PB. 13-week oral (drinking water) investigative phenobarbital study in male C57BL/6 wild type, CAR/PXR knockout and humanized CAR/PXR mice with a 4 week recovery period

Project description:Purpose: Next-generation sequencing (NGS) has been utilized for systems-based analysis of all liver samples. The goals of this study are to use NGS-derived mouse CAR and human CAR initiated transcriptome profiling (RNA-seq) and find out similarity and difference drug processing gene (DPG) pattern after CAR activation in different genotype include WT (C57BL/6 and human CAR transgenic mice with C57BL/6 background) Methods: Liver mRNA profiles of wild-type (WT) and human CAR knockin (hCAR-TG) mice at the age of day 5 and day 60 treated with mouse CAR activator (TCPOBOP) and human CAR activator (CITCO) respectively were generated by deep sequencing, in triplicate, using HiSeq 2000 sequencer. The sequence reads that passed quality filters were analyzed at the transcript level with followed method: HISAT followed by Cufflinks. Results: Using an optimized data analysis workflow,RNA-Seq generated approximately 47 to 68 million reads per sample, among which approximately 40 to 60 million reads were uniquely mapped to the mouse reference genome (NCBI GRCm/38/mm10). And we identified 393 drug processing genes in the livers of WT and hCAR-TG with with HISAT workflow. RNA-seq data confirmed that among all the 393 DPGs with known important functions in xenobiotic biotransformation, 90 DPGs were not expressed in livers of any groups (threshold: average FPKM < 1 in all treatment groups); whereas a total of 303 genes were expressed in livers of at least one groups, among which 258 DPGs were differentially regulated by mCAR or hCAR activation in either Day 5 or Day 60 (FDR-BH<0.05), and 45 genes were stably expressed among all treatment groups. Conclusions: Our study represents the first detailed analysis of drug processing genes, with 3 biologic replicates, generated by RNA-seq technology. The optimized data analysis reported here should provide a framework for comparative investigations of expression profiles by mouse CAR activation and human CAR activation. Our results show that NGS offers a comprehensive and accurate quantitative and qualitative evaluation of mRNA content within tissues.

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High-resolution, in vivo genome binding interactions of the mouse and human constitutive androstane receptors in rodent liver reveal species differences and novel cancer-related target genes

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