1 Department of Comparative Biomedical Sciences, The Royal Veterinary College, University of London, London, United Kingdom; University College London Consortium for Mitochondrial Research, Royal College Street NW1 0TU, London, United Kingdom; Department of Biology, University of Rome-TorVergata, 00133 Rome, Italy; Regina Elena-National Cancer Institute, 00144 Rome, Italy. Electronic address: mcampanella@rvc.ac.uk.