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Figure 1. Humanized UGT1 mice develop neonatal hyperbilirubinemia and seizures.

Toxicant Exposure and Modulation of UGTs in Humanized Mice

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Dr. Robert Tukey

This project will pursue studies with humanized UDP-glucuronosyltransferase 1 (UGT1) mice examining the contribution of environmental toxicant exposure on gene expression and the development of this new animal model as a biological sensor for the detection of agents that activate the family of xenobiotic receptors (XenRs). In humans, there are 19 functional UDP-glucuronosyltransferases with 9 being encoded by the UGT1 locus on chromosome 2. Since the UGT1A proteins participate in the majority of the detoxification processes involving environmental toxicant exposure, we have focused our efforts on humanizing mice with the UGT1 locus. Humanization UGT1 mice has recently been accomplished by first directing a targeted knockout to the murine Ugt1 locus. Interruption of the murine Ugt1 locus results in neonatal lethality caused severe hyperbilirubinemia. This results from inactivation of the murine Ugt1a1 gene, which is the sole UGT responsible for the glucuronidation of bilirubin. However, lethality could be rescued by placing the human UGT1 locus into the Ugt1-null background, resulting in humanized UGT1 (Tg(UGT1)Ugt1-/-) mice. Neonatal Tg(UGT1)Ugt1-/- mice display near toxic levels of total bilirubin (TB) that peak 14 days after birth. The high levels of serum bilirubin lead to bilirubin induced neurological dysfunction (BIND) and seizures in 10% of the neonatal mice (Figure 1). Preliminary findings indicate that hyperbilirubinemia in neonatal Tg(UGT1)Ugt1-/- mice can be controlled by induction of the human UGT1A1 gene, which is regulated by the family of XenRs. The ability to easily monitor serum TB as a marker of UGT1A1 expression during neonatal development and the functional regulation of the UGT1A genes in adult mice will be exploited to examine the impact of environmental toxicant exposure on gene regulation and function. Students and Postdoctoral fellows are examining the impact of environmental toxicant exposure towards regulation of the UGT1 locus both in a tissue specific XenR dependent fashion. The utilization of molecular and mouse genetics underlies the work that is being conducted. New genetic tools are being developed with expression of the human UGT1 locus in XenR-null backgrounds, in addition to regulating the murine Ugt1 locus in various tissues through conditional deletion of the Ugt1a genes. Collaborations are in place with other Superfund projects to investigate the role of environmental toxicant exposure on metabolism and disease.

Lab Members

Dr. Shujuan Chen (Project Scientist)
Dr. Mei-Fei Yueh (Project Scientist)
Dr. Ryoichi Fujiwara (Post Doc)
Camille Konopnicki (Grad Student)
Deirdre La Placa (Staff Research Associate)
Nghia Nguyen (Staff Research Associate)

 

Recent Publications and Documents

Yueh MF, Mellon PL, Tukey RH. Inhibition of Human UGT2B7 Gene Expression in Transgenic Mice by the Constitutive Androstane Receptor. Molecular Pharmacology 79(6):1053-60, 2011. PMC3102552 [Available on 2012/6/1]
PubMed ID: 21415305

Cai H, Nguyen N, Peterkin V, Young-Sun Y, Hotz K, Beaton-La Placa D, Chen S. Tukey RH, and Stevens JC. A humanized UGT1 mouse model expressing the UGT1A1*28 allele for assessing drug clearance by UGT1A1 dependent glucuronidation. Drug Metabol Dispos 38(5): 879-86, 2010. PMC2872941
PubMed ID: 20124398

Fujiwara R, Nguyen N, Chen S, Tukey RH. Developmental hyperbilirubinemia and CNS toxicity in mice humanized with the UDP-glucuronosyltransferase 1 (UGT1) locus. Proc Natl Acad Sci USA 107(11): 5024-5029, 2010. PMC2841904 (Avail 9/16/10)
PubMed ID: 20194756

Savas U, Machemer DE, Hsu MH, Gaynor P, Lasker JM, Tukey RH, Johnson EF. Opposing roles of peroxisome proliferator-activated receptor alpha and growth hormone in the regulation of CYP4A11 expression in a transgenic mouse model. J Biol Chem 284: 16541-16552, 2009. PMC2713544
PubMed ID: 19366684

Argikar UA, Senekeo-Effenberger K, Larson EE, Tukey RH, Remmel RP. Studies on induction of lamotrigine metabolism in transgenic UGT1 mice. Xenobiotica 39:826-835, 2009. PMC2891280
PubMed ID: 19845433

Nguyen, N., Bonzo, J.A., Chen, S., Chouinard, S., Kelner, M., Hardiman, G., Belanger, A., and Tukey, R.H. Disruption of the Ugt1 locus in mice resembles human Crigler-Najjar type I disease. J. Biol. Chem. 283:7901-7911, 2008.
PubMed ID: 18180294

Bonzo, J.A., Belanger, A., and Tukey, R.H. The role of chrysin and the Ah receptor in induction of the human UGT1A1 gene in vitro and in transgenic UGT1 mice. Hepatology, 45: 349-360, 2007.
PubMed ID: 17256720

Operaņa TN, Nguyen N, Chen S, Beaton D and Tukey RH. Human CYP1A1GFP expression in transgenic mice serves as a biomarker for environmental toxicant exposure. Toxicological Sciences 95: 98-107, 2007.
PubMed ID: 17065433

Senekeo-Effenberger, K., Chen, S., Yueh, M-F., Erace-Sinnokrak, E., Bonzo, J.A., Argikar, U., Kaeding, J., Trottier, T., Remmel, R.P., Ritter, J.K., Barbier, O., and Tukey, R.H. Expression of the human UGT1 locus in transgenic mice by 4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid (WY-14643) and implications on drug metabolism through peroxisome proliferator-activated receptor alpha activation. Drug Met. Disp. 35: 419-427, 2007.
PubMed ID: 17151188

Yueh, M-F. and Tukey, R.H. Nrf2-Keap1 signaling pathway regulates human UGT1A1 expression in vitro and in transgenic UGT1 mice. J. Biol. Chem. 282: 8749-8758, 2007.
PubMed ID: 17259171

Operana TN and Tukey RH. Oligomerization of the UDP-glucuronosyltranferase 1A proteins: homo- and heterodimerization analysis by fluorescence resonance energy transfer and co-immunoprecipitation. J Biol Chem 282: 4821-9, 2007. 
PubMed ID: 17179145

Verreault, M., Senekeo-Effenberger, K., Trottier, J., Bonzo, J.A., Belanger, J., Kaeding, J., Staels, B., Caron, P., Tukey, R.H. and Barbier, O. The liver X-receptor alpha controls hepatic expression of the human bile acid-glucuronidating UGT1A3 enzyme in human cells and transgenic mice. Hepatology, 44: 367-378, 2006. 
PubMed ID: 16871576

Bonzo JA, Chen S, Galijatovic A, Tukey RH. Arsenite inihibition of CYP1A1 induction by TCDD is independent of cell cycle arrest. Mol. Pharm. 67:  1247-1256, 2005.
PubMed ID: 15630080

Chen S, Beaton D, Nguyen N, Senekeo-Effenberger K, Brace-Sinnokrak E, Argikar U, Remmel RP, Trottier J, Barbier O, Ritter J, Tukey RH. Tissue-specific, inducible, and hormonal control of the human UDP-glucuronosyltranserase-1 (UGT1) locus. J. Biol. Chem. 280: 37547-37557, 2005.
PubMed ID: 16155002

Chen S, Operana T, Bonzo J, Nguyen N, Tukey RH. Erk kinase inhibition stabilizes the aryl hydrocarbon receptor. J. Biol. Chem. 280:  4350-4359, 2005.
PubMed ID: 15572374

Machemer DEW and Tukey RH. The role of protein kinase C in regulation of TCDD-mediated CYP1A1 gene expression. Toxicological Sciences 87:  27-37, 2005.
PubMed ID: 15947024