Nucleolar development and allocation of key nucleolar proteins require de novo transcription in bovine embryos

TY - JOUR

T1 - Nucleolar development and allocation of key nucleolar proteins require de novo transcription in bovine embryos

AU - Svarcova, Olga

AU - Laurincik, Jozef

AU - Avery, Birthe

AU - Mlyncek, Milos

AU - Niemann, Heiner

AU - Maddox-Hyttel, Poul

PY - 2007

Y1 - 2007

N2 - The goal of the present study was to investigate whether key nucleolar proteins involved in ribosomal RNA (rRNA) transcription and processing are transcribed de novo or from maternally inherited messenger RNAs (mRNA) in bovine embryos, and to which extent de novo transcription of these proteins mRNA is required for the development of functional nucleoli during the major activation of the embryonic genome. Immunofluorescence for localization of key nucleolar proteins, autoradiography for detection of transcriptional activity, and transmission electron microscopy were applied to in vitro produc ed bovine embryos cultured from the 2-cell stage with or without (control groups) a-amanitin, which blocks the RNA plymerases II and III transcription and, thus the synthesis of mRNA. In the control groups, weak autoradiographic labelling was initially observed in the periphery of few nuclei at the 4-cell and the early 8-cell stage, and the entire nucleoplasm as well as nucleolus precursor bodies (NBBs) were prominently labelled in all late 8-cell stages. The NPBs displayed initial transformation into fibrillo-granular nucleoli. In the a-amanitin group, lack of autoradiographic labelling was seen at all developmental stages and disintegrated NPBs stage were found at the late 8-cell. Our immunofluorescence data indicate that RNA polymerase I, UBF, topoisomerase I and fibrillarin are transcribed de novo whereas nucleolin and nucleophosmin are maternally inherited as demonstrated by a-amanitin inhibition. However, localization of these two proteins to the nucleolar compartments was negatively affected by the a-aminitin treatment. Consequentl, functional nucleoli were not established.

AB - The goal of the present study was to investigate whether key nucleolar proteins involved in ribosomal RNA (rRNA) transcription and processing are transcribed de novo or from maternally inherited messenger RNAs (mRNA) in bovine embryos, and to which extent de novo transcription of these proteins mRNA is required for the development of functional nucleoli during the major activation of the embryonic genome. Immunofluorescence for localization of key nucleolar proteins, autoradiography for detection of transcriptional activity, and transmission electron microscopy were applied to in vitro produc ed bovine embryos cultured from the 2-cell stage with or without (control groups) a-amanitin, which blocks the RNA plymerases II and III transcription and, thus the synthesis of mRNA. In the control groups, weak autoradiographic labelling was initially observed in the periphery of few nuclei at the 4-cell and the early 8-cell stage, and the entire nucleoplasm as well as nucleolus precursor bodies (NBBs) were prominently labelled in all late 8-cell stages. The NPBs displayed initial transformation into fibrillo-granular nucleoli. In the a-amanitin group, lack of autoradiographic labelling was seen at all developmental stages and disintegrated NPBs stage were found at the late 8-cell. Our immunofluorescence data indicate that RNA polymerase I, UBF, topoisomerase I and fibrillarin are transcribed de novo whereas nucleolin and nucleophosmin are maternally inherited as demonstrated by a-amanitin inhibition. However, localization of these two proteins to the nucleolar compartments was negatively affected by the a-aminitin treatment. Consequentl, functional nucleoli were not established.

KW - Former LIFE faculty

KW - embryo

KW - maternal-embryonic transition

KW - nucleolus

KW - gene expression

KW - alpha-amanitin

U2 - 10.1002/mrd.20727

DO - 10.1002/mrd.20727

M3 - Journal article

C2 - 17410544

SN - 1040-452X

VL - 74

SP - 1428

EP - 1435

JO - Molecular Reproduction and Development

JF - Molecular Reproduction and Development

IS - 11

ER -