In vivo zygotic- and maternal-effect characterization of the Drosophila melanogaster gene, tango
Creators: name: Scanga, Vanessa Immacolata
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2004
Subjects: subject: Biology, Molecular.

description: This study involved the in vivo phenotypic characterization of the Drosophila melanogaster gene tango (tgo) through classification of both its zygotic-effect during CNS development and maternal-effect during early embryonic patterning. Particularly, this study involved characterization of the prd-repeat domain of the Tango protein, or its allelic equivalent, tgo 3. tgo has been previously isolated as a bHLH-PAS nuclear transcription factor required in the regulation of CNS development through its dimerization of the CNS master transcriptional regulatory gene, single-minded. Having performed an inter-allelic analysis, I grouped the CNS zygotic effects of tgo into various phenotypic classifications. The phenotypes exhibited a pleiotropy of CNS mutant effects and were classified as fused commissure, neurogenic, stalled or ambiguous nervous system defects. These phenotypes may possibly be attributed to different but partially overlapping functions of the various Tgo domains. Additionally, I analyzed the maternal-effect of tgo during precellular blastoderm development. Germline clonal analysis of the tgo3 allele revealed that tgo has an important role during early embryogenesis. Moreover, maternal tgo3 phenotypes resemble those of the more well-characterized maternal coordinate and gap segmentation genes. tgo3 germline clones were embryonic lethal and were classified as severe or intermediate, depending on the extent of deleterious effects on the resultant cuticular phenotype. Germline clones that showed a deletion of the entire anterior end, abdominal segments Al to A5 and missing the Filzkorper and spiracular opening in the posterior end were classified as severe and are comparable to the cuticular phenotypes of amorphic bicoid mutants and Kruppel ( Kr) phenotypes. Less severe deleterious effects, such as improper development of various anterior and posterior end structures or aberrant denticle band formation, were classified as intermediate tgo 3 germline clones, comparable to weaker bicoid alleles. Subsequent stainings to observe the effect on embryonic patterning through gap and pair-rule protein localization revealed alterations in spatial expression patterns. Alterations in both Kruppel and Even-skipped localization patterns in embryos mutant for maternal tgo3 suggest a role for tgo during early embryonic patterning, perhaps through the activity of its prd-repeat domain. Ectopic expression studies, employing the GAL4-UAS system, involved heat shock trials eliciting the ubiquitous expression of a truncated C-terminal Tgo protein (UAS-tgoDeltaC ) and both the ubiquitous land targeted expression of UAS- tgoDeltac. This targeted misexpression analysis revealed tgo as both a possible activator and repressor of Kr gap gene expression, in addition to affecting the protein distribution pattern of the later-acting segmentation gene, engrailed. Taken together, these germline clonal and ectopic expression studies suggest that the role of Tgo during early embryonic patterning may function through combinatorial interactions with maternal-effect and/or early-acting segmentation gene products. Moreover, this role may depend on the function(s) of the C-terminal sequences encoded by Tgo, including the prd repeat domain. Ultimately, this early embryonic role of tgo seems to be distinct from its role as a nuclear transcription factor.