title: Activation of ribosomal RNA genes in preimplantation cattle and swine embryos.
abstract: Transcription of ribosomal RNA (rRNA) genes occurs in the nucleolus resulting in ribosome synthesis. In cattle and swine embryos, functional ribosome-synthesizing nucleoli become structurally recognizable towards the end of the fourth and third post-fertilization cell cycle, respectively. In cattle, a range of important nucleolar proteins become localized to the nucleolar anlage over several cell cycles and this localization is apparently completed towards the end of the fourth cell cycle. In swine, the localization of these proteins to the anlage is more synchronous and occurs towards the end of the third cell cycle and is apparently completed at the onset of the fourth. The rRNA gene activation and the associated nucleolus formation may be used as a marker for the activation of the embryonic genome in mammalian embryos and, thus, serve to evaluate the developmental potential of embryos originating from different embryo technological procedures. By this approach, we have demonstrated that in vitro produced porcine embryos display a lack of localization of nucleolar proteins to the nucleolar anlage as compared with in vivo developed counterparts. Similarly, bovine embryos produced by nuclear transfer from morulae display such deviations as compared with in vitro produced counterparts. Collectively, this information may help to explain the appearance of abnormalities seen in a certain proportion of offspring derived from in vitro produced embryos and after cloning.
authors.affiliation: Department of Anatomy and Physiology, The Royal Veterinary and Agricultural University, Gronnegaardsvej 7, DK-1870, Frederiksberg C, Denmark. poh@kvl.dk
authors.forename: P
authors.initials: P
authors.lastname: Hyttel
authors.forename: J
authors.initials: J
authors.lastname: Laurincik
authors.forename: D
authors.initials: D
authors.lastname: Viuff
authors.forename: T
authors.initials: T
authors.lastname: Fair
authors.forename: V
authors.initials: V
authors.lastname: Zakhartchenko
authors.forename: C
authors.initials: C
authors.lastname: Rosenkranz
authors.forename: B
authors.initials: B
authors.lastname: Avery
authors.forename: D
authors.initials: D
authors.lastname: Rath
authors.forename: H
authors.initials: H
authors.lastname: Niemann
authors.forename: P D
authors.initials: PD
authors.lastname: Thomsen
authors.forename: K
authors.initials: K
authors.lastname: Schellander
authors.forename: H
authors.initials: H
authors.lastname: Callesen
authors.forename: E
authors.initials: E
authors.lastname: Wolf
authors.forename: R L
authors.initials: RL
authors.lastname: Ochs
authors.forename: T
authors.initials: T
authors.lastname: Greve
mesh_terms: D000818:Animals; D002417:Cattle / Q000196:embryology*; D047108:Embryonic Development / Q000235:genetics*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D011247:Pregnancy; D012335:RNA, Ribosomal / Q000235:genetics*; D013552:Swine / Q000196:embryology*; D015533:Transcriptional Activation
chemical_list: D012335:RNA, Ribosomal