Regulated mitochondrial DNA replication during oocyte maturation is essential for successful porcine embryonic development.

Cellular ATP is mainly generated through mitochondrial oxidative phosphorylation, which is dependent on mitochondrial DNA (mtDNA). We have previously demonstrated the importance of oocyte mtDNA for porcine and human fertilization. However, the role of nuclear-encoded mitochondrial replication factors during oocyte and embryo development is not yet understood. We have analyzed two key factors, mitochondrial transcription factor A (TFAM) and polymerase gamma (POLG), to determine their role in oocyte and early embryo development. Competent and incompetent oocytes, as determined by brilliant cresyl blue (BCB) dye, were assessed intermittently during the maturation process for TFAM and POLG mRNA using real-time RT-PCR, for TFAM and POLG protein using immunocytochemistry, and for mtDNA copy number using real-time PCR. Analysis was also carried out following treatment of maturing oocytes with the mtDNA replication inhibitor, 2',3'-dideoxycytidine (ddC). Following in vitro fertilization, preimplantation embryos were also analyzed. Despite increased levels of TFAM and POLG mRNA and protein at the four-cell stage, no increase in mtDNA copy number was observed in early preimplantation development. To compensate for this, mtDNA appeared to be replicated during oocyte maturation. However, significant differences in nuclear-encoded regulatory protein expression were observed between BCB(+) and BCB(-) oocytes and between untreated oocytes and those treated with ddC. These changes resulted in delayed mtDNA replication, which correlated to reduced fertilization and embryonic development. We therefore conclude that adherence to the regulation of the timing of mtDNA replication during oocyte maturation is essential for successful embryonic development

Risks for human and animal health related to the presence of phorbol esters in Jatropha kernel meal

The Panel wishes to thank the members of the Working Group on Phorbol Esters: Bruce Cottrill, Stefano Dall'Acqua, Johanna Fink-Gremmels, Harinder P.S. Makkar and Manfred Metzler for the preparatory work on this scientific opinion, and EFSA staff: Marco Binaglia, Karen Mackay and Rositsa Serafimova for the support provided to this scientific opinion.Peer reviewedPublisher PD

Acute health risks related to the presence of cyanogenic glycosides in raw apricot kernels and products derived from raw apricot kernels

Peer reviewedPublisher PD

Presence of microplastics and nanoplastics in food, with particular focus on seafood

The Panel wishes to thank the members of the Working Group on the presence of microplastics and nanoplastics in food, with particular focus on seafood: Francesco Cubadda, Christer Hogstrand, Peter Hollman, Hendrik Van Loveren, Anne-Katrine Lundebye and Annette Petersen for the preparatory work on this statement, the hearing expert: Stephanie Wright and EFSA staff member: Karen Mackay for the support provided to this statement.Peer reviewedPublisher PD