Reprod Dom Anim. 2018;1–10. wileyonlinelibrary.com/journal/rda | 1 © 2018 Blackwell Verlag GmbH 1 | INTRODUCTION Endogenous retroviruses (ERVs) belong to a major class of transpos‐ able elements which are integrated into the mammalian genome. These elements are thought to be originated from infectious retro‐ viruses that have infected germ cell precursors, germ cells or per‐ haps some somatic cells. Our understanding on the importance and function of ERVs have considerably evolved in the past decade, from assuming these elements as genome parasites to a realization that they control major cellular and developmental events (Chuong, Elde, & Feschotte, 2017). Numerous empirical studies indicate that ERVs are involved in cellular proliferation, pluripotency, tissue‐specific re‐ modelling and regulation of developmental processes. Specific families of bovine endogenous retroviruses (BERVs) have been characterized. The identified complete genomic or‐ ganization of BERV β3 family showed that the deduced open Received: 12 February 2018 | Revised: 16 June 2018 | Accepted: 23 June 2018 DOI: 10.1111/rda.13269 ORIGINAL ARTICLE Expression of endogenous retroviruses in pre‐implantation stages of bovine embryo Elaheh Khazaee 1 | Nima Farzaneh 1 | Pezhman Mirshokraei 1,2 | Seyed‐Elias Tabatabaeizadeh 3 | Hesam Dehghani 4,5 1 Department of Clinical Sciences, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad, Iran 2 Faculty of Veterinary Medicine, Center of Excellence in Ruminant Abortion and Neonatal Mortality, Ferdowsi University of Mashhad, Mashhad, Iran 3 Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran 4 Stem Cell Biology and Regenerative Medicine Research Group, Research Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran 5 Department of Basic Sciences, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad, Iran Correspondence Nima Farzaneh, Department of Clinical Sciences, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad, Iran. Email: farzaneh@um.ac.ir Hesam Dehghani, Stem Cell Biology and Regenerative Medicine Research Group, Research Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran. Email: dehghani@um.ac.ir Funding information This study was financially supported by grant number 3/26894 from Ferdowsi University of Mashhad. Abstract Endogenous retroviruses (ERVs) are involved in cellular proliferation, pluripotency, tissue‐specific remodelling and regulation of developmental processes. These ele‐ ments are transcriptionally active in mouse and human pre‐implantation embryos. Empirical evidence indicates that regulatory networks involved with ERV transcripts are responsible for pluripotency and totipotency at certain stages of mouse and human pre‐implantation development. Yet, the expression in pre‐implantation bo‐ vine embryo remains unidentified. To determine whether two members of bovine endogenous retroviruses, BERV‐K1 and BERV‐K2, are expressed in the pre‐implanta‐ tion bovine embryo, each embryonic stage developed in vitro and was subjected to RNA release, reverse transcription and quantitative PCR. We found that BERV‐K1 and BERV‐K2 are expressed throughout different stages of pre‐implantation devel‐ opment. The higher level of expression was detected in embryonic blastomeres with totipotent/pluripotent status (two‐cell to 16‐cell stages), while the more differenti‐ ated blastocyst stage showed significantly lower levels of ERVs expression. These findings suggest a possible role for endogenous retroviruses in the establishment of totipotent and pluripotent states in pre‐implantation bovine embryo, similar to func‐ tions which have been suggested for these elements in human and mouse embryos. KEYWORDS BERV‐K1, BERV‐K2, bovine, endogenous retroviruses, pre‐implantation embryo, RT‐qPCR