Nucleolar proteins and nuclear ultrastructure in preimplantation bovine embryos produced in vitro
The aim of the present investigation was to describe the basic cell biology of the postfertilization activation of rRNA genes using in vitro-produced bovine embryos as a model. We used immunofluorescence confocal laser scanning microscopy and transmission electron microscopy to study nucleolar devel...
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Published in | Biology of reproduction Vol. 62; no. 4; pp. 1024 - 1032 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Madison, WI
Society for the Study of Reproduction
01.04.2000
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Subjects | |
Online Access | Get full text |
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Summary: | The aim of the present investigation was to describe the basic cell biology of the postfertilization activation of rRNA genes
using in vitro-produced bovine embryos as a model. We used immunofluorescence confocal laser scanning microscopy and transmission
electron microscopy to study nucleolar development in the nuclei of embryos up to the fifth postfertilization cell cycle.
During the first cell cycle (1-cell stage), fibrillarin, upstream binding factor (UBF), nucleolin (C23), and RNA polymerase
I were localized to distinct foci in the pronuclei, and, ultrastructurally, compact spherical fibrillar masses were the most
prominent pronuclear finding. During the second cell cycle (2-cell stage), the findings were similar except for a lack of
nucleolin and RNA polymerase I labeling. During the third cell cycle (4-cell stage), fibrillarin, UBF, nucleophosmin, and
nucleolin were localized to distinct foci. Ultrastructurally, spherical fibrillar masses that developed a central vacuole
over the course of the cell cycle were observed. Early in the fourth cell cycle (8-cell stage), fibrillarin, nucleophosmin,
and nucleolin were localized to small bodies that with time developed a central vacuole. UBF and topoisomerase I were localized
to clusters of small foci. Ultrastructurally, spherical fibrillar masses with a large eccentric vacuole and later small peripheral
vacuoles were seen. Late in the fourth cell cycle, nucleophosmin and nucleolin were localized to large shell-like bodies;
and fibrillarin, UBF, topoisomerase I, and RNA polymerase I were localized to clusters of small foci. Ultrastructurally, a
presumptive dense fibrillar component (DFC) and fibrillar centers (FCs) were observed peripherally in the vacuolated spherical
fibrillar masses. Subsequently, the presumptive granular component (GC) gradually became embedded in the substance of this
entity, resulting in the formation of a fibrillo-granular nucleolus. During the fifth cell cycle (16-cell stage), a spherical
fibrillo-granular nucleolus developed from the start of the cell cycle. In conclusion, the nucleolar protein compartment in
in vitro-produced preimplantation bovine embryos is assembled over several cell cycles. In particular, RNA polymerase I and
topoisomerase I are detected for the first time late during the fourth embryonic cell cycle, which coincides with the first
recognition of the DFC, FCs, and GC at the ultrastructural level. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0006-3363 1529-7268 |
DOI: | 10.1095/biolreprod62.4.1024 |