title: Spatiotemporal expression and transcriptional regulation of heme oxygenase and biliverdin reductase genes in zebrafish (Danio rerio) suggest novel roles during early developmental periods of heightened oxidative stress.
abstract: Heme oxygenase 1 (HMOX1) degrades heme into biliverdin, which is subsequently converted to bilirubin by biliverdin reductase (BVRa or BVRb) in a manner analogous to the classic anti-oxidant glutathione-recycling pathway. To gain a better understanding of the potential antioxidant roles the BVR enzymes may play during development, the spatiotemporal expression and transcriptional regulation of zebrafish hmox1a, bvra and bvrb were characterized under basal conditions and in response to pro-oxidant exposure. All three genes displayed spatiotemporal expression patterns consistent with classic hematopoietic progenitors during development. Transient knockdown of Nrf2a did not attenuate the ability to detect bvra or bvrb by ISH, or alter spatial expression patterns in response to cadmium exposure. While hmox1a:mCherry fluorescence was documented within the intermediate cell mass, a transient location of primitive erythrocyte differentiation, expression was not fully attenuated in Nrf2a morphants, but real-time RT-PCR demonstrated a significant reduction in hmox1a expression. Furthermore, Gata-1 knockdown did not attenuate hmox1a:mCherry fluorescence. However, while there was a complete loss of detection of bvrb expression by ISH at 24hpf, bvra expression was greatly attenuated but still detectable in Gata-1 morphants. In contrast, 96 hpf Gata-1 morphants displayed increased bvra and bvrb expression within hematopoietic tissues. Finally, temporal expression patterns of enzymes involved in the generation and maintenance of NADPH were consistent with known changes in the cellular redox state during early zebrafish development. Together, these data suggest that Gata-1 and Nrf2a play differential roles in regulating the heme degradation enzymes during an early developmental period of heightened cellular stress.
authors.affiliation: Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Holowiecki
authors.affiliation: Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA.
authors.forename: Britton
authors.initials: B
authors.lastname: O'Shields
authors.affiliation: Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA. Electronic address: mjjenny@ua.edu.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Jenny
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001665:Binding Sites; D019187:Cadmium Compounds / Q000633:toxicity; D050982:GATA1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006410:Hematopoiesis; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D051267:NF-E2-Related Factor 2; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C019789:biliverdin reductase; D019187:Cadmium Compounds; D050982:GATA1 Transcription Factor; C494691:gata1a protein, zebrafish; C000605843:heme oxygenase 1, zebrafish; D051547:Heme Oxygenase-1; D009249:NADP; D051267:NF-E2-Related Factor 2; C495638:nfe2l2a protein, zebrafish; D044925:Oxidoreductases Acting on CH-CH Group Donors; D029961:Zebrafish Proteins
keywords: Biliverdin reductase; Cadmium; GATA-1; Hematopoiesis; Heme oxygenase; NRF2; Oxidative stress