Original Scientific Article Fully-grown mammalian oocytes contain morphologically evident but transcriptionally inactive nucleoli called “nucleolus-like bodies” (NLBs). These nuclear structures are essential for early embryonic development. Removing oocyte NLBs (enucleolation) before their activation leads to developmental failure, mainly at the time point of embryonic genome activation. The present study examined the developmental and expression dynamics of embryos derived from intra- (pig) and interspecies (mouse) nucleolus (NLB) transferred porcine oocytes after parthenogenetic activation. Activation of rDNA transcription and pre-rRNA processing in NLB re-injected embryos was observed by real-time qRT-PCR analysis, targeting the expression rates of 45S rRNA and levels of 18S rRNA. Reinjection of NLBs from mouse or porcine GV oocytes into the enucleolated MII stage porcine oocytes supported the embryonic development up to the blastocyst stage after their activation. Intra- and intergeneric NLB transferred embryos demonstrated rDNA transcription initiation at the 8-cell stage, corresponding with the embryonic genome activation in porcine parthenogenetic embryos (control). The measured levels of 18S rRNA in these experimental embryos showed delayed initiation of pre-rRNA processing at the blastocysts stage compared with the control (8-cell stage). However, the porcine embryos with re-injected mouse NLB displayed significantly higher levels of 18S rRNA than the control and experimental intraspecies group. In conclusion, NLBs from different mammal species (mouse) can enhance the quality of enucleolated porcine oocytes and thus support their early embryonic development after activation. https://macvetrev.mk/LoadArticlePdf/361 2025-01-10 i vii https://doi.org/10.2478/macvetrev-2025-0011 nucleolus-like body oocyte pig mouse nucleolotransfer Martin Morovic false 1 Faculty of Natural Sciences, Constantine the Philosopher University in Nitra, Nabrezie Mladeze 91, 94974 Nitra, Slovak Republic AUTHOR Frantisek Strejcek fstrejcek@ukf.sk false 2 Faculty of Natural Sciences, Constantine the Philosopher University in Nitra, Nabrezie Mladeze 91, 94974 Nitra, Slovak Republic LEAD_AUTHOR Michal Benc false 3 Faculty of Natural Sciences, Constantine the Philosopher University in Nitra, Nabrezie Mladeze 91, 94974 Nitra, Slovak Republic AUTHOR Alexandra Rosenbaum Bartkova false 4 Faculty of Natural Sciences, Constantine the Philosopher University in Nitra, Nabrezie Mladeze 91, 94974 Nitra, Slovak Republic, Institute of Animal Physiology and Genetics; Czech Academy of Sciences, Rumburska 89, 277 21 Libechov, Czech Republic AUTHOR Sara Stachovicova false 5 Faculty of Natural Sciences, Constantine the Philosopher University in Nitra, Nabrezie Mladeze 91, 94974 Nitra, Slovak Republic; Université Paris-Saclay, Université de Versailles Saint-Quentin-en-Yvelines, INRAE, BREED, Jouy-en-Josas, France AUTHOR Florina Popovska-Percinic false 6 Faculty of Veterinary Medicine-Skopje, Ss. Cyril and Methodius University in Skopje, 1000 Skopje, North Macedonia AUTHOR Monika Dovenska false 7 Faculty of Veterinary Medicine-Skopje, Ss. Cyril and Methodius University in Skopje, 1000 Skopje, North Macedonia AUTHOR Jozef Laurincik false 8 Faculty of Natural Sciences, Constantine the Philosopher University in Nitra, Nabrezie Mladeze 91, 94974 Nitra, Slovak Republic AUTHOR Lavrentyeva, E., Shishova, K., Kagarlitsky, G., Zatsepina, O. (2015). Localisation of RNAs and proteins in nucleolar precursor bodies of early mouse embryos. Reprod Fert Develop. 29(3): 509-520. 1 https://doi.org/10.1071/RD15200 Shishova, K.V., Lavrentyeva, E.A., Dobrucki, J.W., Zatsepina, O.V. (2015). Nucleolus-like bodies of fully-grown mouse oocytes contain key nucleolar proteins but are impoverished for rRNA. Dev Biol. 397(2): 267-281. 2 https://doi.org/10.1016/j.ydbio.2014.11.022 Motlik, J., Fulka, J. (1986). Factors affecting meiotic competence in pig oocytes. 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