Proceedings of The Physiological Society

Mitochondria: Form and function (London, UK) (2017) Proc Physiol Soc 38, PC14

Poster Communications

Oscillations in mitochondrial ROS production during the early cell cycles in Xenopus embryos

J. Iglesias-Gonzalez1, C. Thomson1, S. Ishibashi1, E. Amaya1

1. Cell-Matrix Research Dvision, Manchester University, Manchester, United Kingdom.

The ability to repair and regenerate tissues is an essential process for the survivability and development of the organisms. Amphibians excel on these processes and are invaluable models to study the molecular and cellular mechanisms underlying scar free wound healing and tissue regeneration. Among these, we have used the frog, Xenopus, as an animal model to study the role of reactive oxygen species (ROS) during the early embryonic development and appendage regeneration. Both embryonic development and tissue repair/regeneration require cell proliferation, which relies on the synchronized mechanisms that regulate the cell cycle [1]. The mitochondrion is the powerhouse of the cell but it is also involved in other processes such as cellular signaling and calcium buffering. However, the roles of mtROS during early vertebrate development have remained largely unknown. For this reason, our main aim is to understand how the mitochondria, metabolism and ROS are regulated during early development and tissue regeneration. We have recently shown using transgenic Xenopus frog embryos expressing the genetically encoded ROS indicator HyPer that mtROS is increased after fertilization and that it oscillates during each cell division. When we exposed the embryos to mitochondrial inhibitors we observed that complex II is the primary source of ROS in vivo and that the inhibitors differentially affect the oscillatory patterns of ROS production. Furthermore, in order to identify the source of mtROS in the electron transfer system, we performed a study of mitochondrial function in a cell-free system (i.e. egg extract) combining high-resolution respirometry, hydrogen peroxide production and membrane potential [2]. Our study reveals that the succinate dehydrogenase complex (CII), specifically the flavoprotein in the SdhA subunit, is the major source of mtROS when the mitochondria are fuelled by succinate. Also, we have found that the calcium acts upstream of ROS production from the mitochondria. Finally, we have discovered that the ATP levels also oscillate during the cell cycle and our results suggest that cellular metabolism alternates between aerobic glycolysis (Warburg Effect) and OXPHOS in association with the cell cycle. Our results highlight an entanglement between calcium, metabolism and ROS but further work is required to understand how these processes are related to the cell cycle and its relevance for the early development and tissue regeneration.

Where applicable, experiments conform with Society ethical requirements