TitleIdentification of zebrafish ARNT1 homologs: 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity in the developing zebrafish requires ARNT1.
Publication TypeJournal Article
Year of Publication2006
AuthorsPrasch, AL, Tanguay, RL, Mehta, V, Heideman, W, Peterson, RE
JournalMol Pharmacol
Volume69
Issue3
Pagination776-87
Date Published2006 Mar
ISSN0026-895X
KeywordsAmino Acid Sequence, Animals, Aryl Hydrocarbon Receptor Nuclear Translocator, Cercopithecus aethiops, COS Cells, DNA, Complementary, Drug Resistance, Embryo, Nonmammalian, Molecular Sequence Data, Phylogeny, Polychlorinated Dibenzodioxins, Receptors, Aryl Hydrocarbon, RNA Splicing, Trans-Activators, Zebrafish, Zebrafish Proteins
Abstract

To use the zebrafish (Danio rerio) as a model to study 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) developmental toxicity, it is essential to know which proteins are involved in mediating toxicity. Previous work has identified zfAHR2 as the receptor that binds TCDD mediating downstream responses. Although zfARNT2b can form a functional heterodimer with zfAHR2 in vitro, zfarnt2 null mutants show no protection against endpoints of TCDD developmental toxicity, demonstrating that zfARNT2b cannot be the physiological dimerization partner for zfAHR2 mediating responses to TCDD in zebrafish embryos. The purpose of the current study was to identify an alternate dimerization partner(s) for zfAHR2 that may function to mediate TCDD developmental toxicity. By searching zebrafish genomic sequence and using the polymerase chain reaction-based rapid amplification of cDNA ends technique, three forms of cDNA that seem to be alternate mRNA splice variants of a zebrafish homolog of ARNT1 were detected. Analysis of the zfARNT1 proteins in vitro demonstrates that the two longest forms of zfARNT1, zfARNT1b and zfARNT1c, can form functional heterodimers with zfAHR2. However, the shortest form, zfARNT1a, seems to be nonfunctional with zfAHR2 in vitro. To determine whether a zfARNT1 protein functions with zfAHR2 in vivo, a morpholino targeted against the 5' end of zfARNT1 (zfarnt1-MO) was used. Injection of the zfarnt1-MO before TCDD treatment significantly decreases the induction of zfCYP1A mRNA and protein. In addition, zfarnt1 morphants show complete protection against TCDD-induced pericardial edema and show partial protection against reduced blood flow and craniofacial malformations caused by TCDD, demonstrating the role of zfARNT1 proteins in mediating these responses.

DOI10.1124/mol.105.016873
Alternate JournalMol. Pharmacol.
PubMed ID16306231
Grant ListT32-ES07015 / ES / NIEHS NIH HHS / United States
ES00210 / ES / NIEHS NIH HHS / United States
ES03850 / ES / NIEHS NIH HHS / United States
R01-ES10820 / ES / NIEHS NIH HHS / United States
R01-ES0127716 / ES / NIEHS NIH HHS / United States
R01 ES010820 / ES / NIEHS NIH HHS / United States
P30 ES000210 / ES / NIEHS NIH HHS / United States