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Novel roles for peroxisome-linked genes in Drosophila
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- Author / Creator
- Pridie, Conrad
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Peroxisomes are organelles responsible for processing lipids and managing reactive oxygen species. A conserved family of genes called peroxisome biogenesis factors (Peroxin, Pex) encode proteins necessary for peroxisome biogenesis and function. In yeast and mammals, PEROXIN7 (PEX7) acts as a cytosolic receptor protein that targets proteins containing a peroxisome targeting sequence 2 (PTS2) motif for peroxisome matrix import. The PTS2 motif is not present in the Drosophila melanogaster homologs of proteins that are trafficked by PEX7 in yeast or mammals. The fly genome does contain a Pex7 gene (CG6486) that is very similar to yeast and human PEX7. My work (Chapter 3) showed that Pex7 was expressed in tissue-specific patterns analogous to neurons in Drosophila embryos. I correlated this with a requirement for Pex7 in that cell lineage, as targeted somatic Pex7 knockout in embryonic neurons reduced survival. Pex7 over-expression in neurons caused lethality during the larval stage. Targeted somatic over-expression of a Pex7 transgene in neurons of Pex7 homozygous mutants resulted in a semi-lethal phenotype similar to targeted Pex7 knockout. These observations suggested tissue-specific requirements for Pex7 during Drosophila development.
Prior studies of the interactions between peroxisomes and microtubules uncovered a role for genes outside the Peroxin gene family in the regulation of peroxisome import competence, morphology and abundance. A genome-wide RNA interference (RNAi) screen identified seventeen such genes that qualitatively altered the peroxisome marker GFP-PTS1 in Schneider 2 cells. My work (Chapter 4) showed that transient knockdown of eight of these genes resulted in altered peroxisome abundance. Transient over-expression of eleven of these genes also resulted in altered peroxisome abundance. Of thirteen total genes with a demonstrated effect, eight have canonical roles in mitosis and two are involved in the regulation of non-muscle myosin motors. The effects of three genes encoding parts of the chromosome passenger complex - aurB, borr and Incenp - suggest cytokinesis and abscission function as cues for peroxisome proliferation. My studies showed that while peroxisomes are largely conserved in Drosophila, and that flies represent an effective model for identifying new aspects of peroxisome biogenesis, there are also substantial differences in Drosophila Peroxin function compared to other models.
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- Graduation date
- Fall 2020
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
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