Nucleolus formation in pre-implantation cattle and swine embryos.
Transcription of ribosomal RNA (rRNA) genes occurs in the nucleolus resulting in ribosome synthesis. In bovine and porcine embryos functional ribosome-synthesizing nucleoli become structurally recognizable towards the end of the 4th and 3rd post-fertilization cell cycle, respectively. In cattle, a range of important nucleolar proteins become localized in the nucleolar anlage over several cell cycles and this localization is apparently completed towards the end of the 4th cell cycle. In swine, the localization of these proteins in the anlage is more synchronous and occurs towards the end of the 3rd cell cycle and is apparently completed at the onset of the 4th. 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.
Hyttel
P
P
Department of Anatomy and Physiology, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark. poh@kvl.dk
D000818:Animals; D002417:Cattle / Q000196:embryology*; D002466:Cell Nucleolus / Q000502:physiology* / Q000648:ultrastructure; D004622:Embryo, Mammalian / Q000648:ultrastructure; D047108:Embryonic Development; D005260:Female; D015870:Gene Expression; D011247:Pregnancy; D012335:RNA, Ribosomal / Q000235:genetics; D012270:Ribosomes / Q000502:physiology / Q000648:ultrastructure; D013552:Swine / Q000196:embryology*; D015053:Zygote / Q000648:ultrastructure
D012335:RNA, Ribosomal