title: Identification of a key role for permeability glycoprotein in enhancing the cellular defense mechanisms of fertilized oocytes.
abstract: Double strand breaks (DSBs) are highly damaging DNA lesions that can destabilize the genome and generate a suite of adverse physiological outcomes in the oocyte and early embryo. While it is therefore likely that these cells possess a sophisticated suite of protective mechanisms to ameliorate such damage, the precise nature of these defense systems are yet to be fully elucidated. This study characterizes the sensitivity of the oocyte to etoposide, a chemotherapeutic agent with the ability to elicit DSBs. We demonstrate significant developmental changes in etoposide vulnerability, with fertilization of the oocyte leading to an enhancement of its cellular defense machinery. Using a parthenogenic model we show that this response is mediated, at least in part, by permeability glycoprotein (PGP), an endogenous multidrug efflux transporter that is up-regulated, translocated to the oolemma and phosphorylated upon oocyte activation. Moreover, evidence from dye exclusion assays in the presence of a specific PGP pharmacological inhibitor (PSC833), illustrates that these events effectively increase oocyte efflux activity, thereby enhancing the ability of these cells to exclude genotoxicants capable of eliciting DSB formation.
authors.affiliation: Priority Research Centre for Reproductive Science, Discipline of Biological Sciences and Hunter Medical Research Institute, University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: jacinta.martin@newcastle.edu.au.
authors.forename: Jacinta H
authors.initials: JH
authors.lastname: Martin
authors.affiliation: Priority Research Centre for Reproductive Science, Discipline of Biological Sciences and Hunter Medical Research Institute, University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: brett.nixon@newcastle.edu.au.
authors.forename: Brett
authors.initials: B
authors.lastname: Nixon
authors.affiliation: Priority Research Centre for Reproductive Science, Discipline of Biological Sciences and Hunter Medical Research Institute, University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: tlord@vetmed.wsu.edu.
authors.forename: Tessa
authors.initials: T
authors.lastname: Lord
authors.affiliation: Priority Research Centre for Reproductive Science, Discipline of Biological Sciences and Hunter Medical Research Institute, University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: elizabeth.bromfield@newcastle.edu.au.
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Bromfield
authors.affiliation: Priority Research Centre for Reproductive Science, Discipline of Biological Sciences and Hunter Medical Research Institute, University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: john.aitken@newcastle.edu.au.
authors.forename: R John
authors.initials: RJ
authors.lastname: Aitken
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D003524:Cyclosporins / Q000494:pharmacology; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D005047:Etoposide / Q000493:pharmacokinetics* / Q000494:pharmacology*; D005260:Female; D005306:Fertilization; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009865:Oocytes / Q000166:cytology / Q000187:drug effects*; D010539:Permeability; D059005:Topoisomerase II Inhibitors / Q000494:pharmacology*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003524:Cyclosporins; D059005:Topoisomerase II Inhibitors; D005047:Etoposide; C070272:valspodar
keywords: DNA damage; Oocyte; Permeability glycoprotein; Zygote