Combination of Hypomorphic Mutations of the Drosophila Homologues of Aryl Hydrocarbon Receptor and Nucleosome Assembly Protein Family Genes Disrupts Morphogenesis, Memory and Detoxification

Abstract

Aryl hydrocarbon receptor is essential for biological responses to endogenous and exogenous toxins in mammals. Its Drosophila homolog spineless plays an important role in fly morphogenesis. We have previously shown that during morphogenesis spineless genetically interacts with CG5017 gene, which encodes a nucleosome assembly factor and may affect cognitive function of the fly. We now demonstrate synergistic interactions of spineless and CG5017 in pathways controlling oxidative stress response and long-term memory formation in Drosophila melanogaster. Oxidative stress was induced by low doses of X-ray irradiation of flies carrying hypomorphic mutation of spineless, mutation of CG5017, and their combination. To determine the sensitivity of these mutants to pharmacological modifiers of the irradiation effect, we irradiated flies growing on standard medium supplemented by radiosensitizer furazidin and radioprotector serotonin. The effects of irradiation were investigated by analyzing leg and antenna morphological structures and by using real-time PCR to measure mRNA expression levels for spineless, Cyp6g1 and Gst-theta genes. We also examined long-term memory in these mutants using conditioned courtship suppression paradigm. Our results show that the interaction of spineless and CG5017 is important for regulation of morphogenesis, long-term memory formation, and detoxification during oxidative stress. Since spineless and CG5017 are evolutionary conserved, these results must be considered when evaluating the risk of combining similar mutations in other organisms, including humans.

Understanding the Mechanisms Involved in the Regulation of Cytochrome P450 Gene Expression in Drosophila melanogaster (Diptera: Drosophilidae)

“…These proteins share extensive sequence identity, especially in their Basic Helix-Loop-Helix (bHLH) regions, and must share common ancestry, as several of the splice sites in the Ss and AhR genes are precisely conserved [47].…”

“…Consequently, cellular concentrations of FICZ levels are elevated considerably in response to ionizing radiation and this inevitably triggers elevated expression of the Ahr gene thereby leading to cellular reaction to toxin exposure, and, in particular, to ionizing radiation. This induces expression of detoxification-related genes Cyp6g1 and Cg1681, hence ss gene is necessary for this induction [47]. This protein can however bind to the XRE and stimulate transcription from genes containing this cis-acting element [49,53].…”

“…It is known to interact with Tango (Tgo), the fly homolog of mammalian ARNT and through this interaction the protein is transported to the nucleus from the cytoplasm where it binds another bHLH-PAS-protein, the Aryl hydrocarbon receptor nuclear translocator (ARNT). The Ss: Tgo heterodimer binds to a specific motif, XRE in the promoters of its target genes and regulates their transcription [47,55]. The Ss: Tgo heterodimer can both repress and activate explicit genes, demonstrating the heterodimer's interplay with other transcription or nucleosome assembly factors [47].…”

“…The Ss: Tgo heterodimer binds to a specific motif, XRE in the promoters of its target genes and regulates their transcription [47,55]. The Ss: Tgo heterodimer can both repress and activate explicit genes, demonstrating the heterodimer's interplay with other transcription or nucleosome assembly factors [47]. AhR gene is exceedingly conserved between vertebrates and invertebrates ( Figure 1) [47].…”

“…The Ss: Tgo heterodimer can both repress and activate explicit genes, demonstrating the heterodimer's interplay with other transcription or nucleosome assembly factors [47]. AhR gene is exceedingly conserved between vertebrates and invertebrates ( Figure 1) [47].…”