Development of the nucleolus in early goat embryos

Chartrain, Isabelle; Niar, A.; King, W.A.; Picard, L.; St-Pierre, H.

doi:10.1002/mrd.1120180302

Cited by 23 publications

(8 citation statements)

References 27 publications

(10 reference statements)

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“…Likewise, in bovine embryos, extranucleolar RNA synthesis was initially detected in 2-cell embryos [22][23][24], while nucleolar RNA transcription was not detected until the 8-cell stage [12], in association with major qualitative changes in ␣-amanitin-sensitive protein synthesis [7,8,37,38]. These studies as well as similar studies in sheep [36], goats [40], pigs [18], and horses [13,39] confirm that the onset of nucleolar RNA synthesis is associated with ultrastructural features of nucleologenesis consistent with the major activation of the embryonic genome. Nevertheless, it is also apparent that genome activation is not a rapid, onestep process, but rather that a gradual activation of embryonic genes occurs during the course of preimplantation development, beginning as early as the 2-cell stage in bovine and primate embryos.…”

Section: Discussionmentioning

confidence: 54%

“…During this critical period, embryos experience species-specific blocks to development in the presence of ␣-amanitin and under various culture conditions in vitro, indicating that MET may be one of the most important events for successful development during preimplantation embryogenesis. The timing of various aspects of MET have been characterized in several species (mouse [20,34]; hamster [35]; sheep [36]; pig [10,18]; cow [7, 8, 11, 12, 22-24, 37, 38]; horse [13,39]; goat [40]), including humans [5,6,[14][15][16][17]41]. In the present study, we have used sensitive autoradiographic and immunocytochemical techniques to characterize the timing of the onset of nucleolar and extranucleolar transcription and expression of the nucleolar protein fibrillarin during MET in rhesus monkey embryos developing in vitro.…”

Section: Discussionmentioning

confidence: 99%

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Onset of Nucleolar and Extranucleolar Transcription and Expression of Fibrillarin in Macaque Embryos Developing In Vitro1

Schramm

Bavister

1999

Biology of Reproduction

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Specific aims were to characterize the onset of nucleolar and extranucleolar transcription and expression of the nucleolar protein fibrillarin during preimplantation development in vitro in macaque embryos using autoradiographic and immunocytochemical techniques. Autoradiography was performed on whole embryos cultured with [3H]uridine for assessment of nucleolar (rRNA) and extranucleolar (mRNA) transcription. Expression of fibrillarin was immunocytochemically assessed in whole embryos using a primary antibody against fibrillarin and a fluorescein isothiocyanate-conjugated secondary antibody. Extranucleolar incorporation of [3H]uridine was first detected in 2-cell embryos cultured 6-10 h with [3H]uridine. Culture with alpha-amanitin prevented incorporation of label in 2-cell embryos, and treatment with ribonuclease reduced the signal to background levels, indicating that [3H]uridine was incorporated into mRNA and not rRNA or DNA. Nucleolar incorporation of [3H]uridine was not evident in pronucleate-stage or 2- to 5-cell embryos, but it was detected in one 6-cell embryo and in all 8-cell to blastocyst-stage embryos. Fibrillarin was first expressed in some 6- to 7-cell embryos, but it was consistently expressed in all 8-cell embryos. Fibrillarin was localized to the perimeter of the nucleolar precursor bodies, forming a ring that completely encapsulated these structures. Fibrillarin was not expressed in 8- to 16-cell embryos cultured with alpha-amanitin, indicating that it is transcribed, rather than recruited, at the 8-cell stage. In conclusion, in in vitro-fertilized macaque embryos developing in vitro, extranucleolar synthesis of mRNA is initiated at the 2-cell stage while the onset of nucleolar transcription occurs at the 6- to 8-cell stage, coincident with expression of fibrillarin.

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Section: Discussionmentioning

confidence: 54%

Section: Discussionmentioning

confidence: 99%

Onset of Nucleolar and Extranucleolar Transcription and Expression of Fibrillarin in Macaque Embryos Developing In Vitro1

Schramm

Bavister

1999

Biology of Reproduction

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“…The studies on early mammalian embryos other than murine, e.g., those of rats and rabbits (Szollosi, 1971;VanBlerkom et al, 1973;Cotton et al, 1980) or particularly those of sheep (Calarco and McLaren, 1976) led to the idea of possible differences as to the timing during ontogenesis of the establishment of the embryonic rRNA synthetic machinery and so also of the protosynthetic apparatus. Recent experiments on early human embryos (TesaFik et al, 1986a(TesaFik et al, ,b, 1987 and on cow (KopeEny et al, 1985;King et al, 1985King et al, , 1988Camous et al, 1986), goat (Chartrain et al, 1987) and pig embryos (KopeEny et al, 1985;Tomanek et al, 1986) confirmed that they differ from the mouse model as well as among themselves. These studies enriched our understanding of differences among species in the association between ribosomal DNA and the nucleolar anlage, the nucleolar-precursor body (NPB), and especially the localization of this process in ontogenesis.…”

Section: Introductionmentioning

confidence: 93%

Nucleologenesis and the onset of transcription in the eight‐cell bovine embryo: Fine‐structural autoradiographic study

Kopečný¹,

Fléchon

Camous

et al. 1989

Molecular Reproduction Devel

158

105

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Eight-cell cow embryos were isolated and cultured in vitro in a medium enriched with 200 microCi of [5-3H]uridine for 20 min. Epon ultrathin sections of the embryos were investigated for the nucleolar morphology and for the appearance and localization of the sites of [5-3H]uridine incorporation by means of electron microscopic autoradiography. In addition to this, a general pattern of replicated embryonal DNA distribution was revealed by [methyl-3H]thymidine incorporation and light microscopic autoradiography. The essential phases of the transformation of the small nucleolus precursor body (NPB) into a vast, functionally fully active nucleolus, characterized by typical nucleolar substructural components, are taking place within the eight-cell stage. This process differed in its morphology from the nucleologenetic process in early embryogenesis of other mammals, especially of that in the mouse. The first sign of NPB transformation was the appearance of a large central vacuole followed later on by perinucleolar chromatin penetration into NPB, documented by both morphology and [3H]thymidine autoradiography. In some cases, concentration of dense fibrillar material forming clumps or stalks was seen in the central vacuole. The following rapid nucleolar development was characterized by the formation of secondary vacuoles concomitant with the onset of [5-3H]uridine incorporation into the dense fibrillar component and with the appearance of the first granules in the otherwise fibrillar structure of the nucleolus. During the late eight-cell stage, the still-rounded nucleolus developed features of a reticulated nucleolus known from somatic cells intensively synthesizing rRNA: a dense fibrillar component with associated labeling encircling fibrillar centers and a well-developed granular component. The labeled dense fibrillar component was observed mostly in the central area of the nucleolus; early embryonic NPB dense fibrous material not involved in transcription was disappearing rapidly. At the transition to the 16-cell stage the nucleoli lost their rounded shape because of the accumulation of a large amount of granular component, and they occupied a considerable part of the nucleus. In conclusion, the appearance of the nucleolar vacuole in eight-cell cow embryo is the starting point for following morphogenetic events linked with the onset of transcription.

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“…However the active nucleoli do not immediately develop after fertilization but at species-specific cleavage stages. The morphological features of nucleologenesis are well established in the mouse (Hillman and Tasca, 1969), sheep (Calarco and McLaren, 1976), goat (Chartrain et al, 1987), human (Tesařík et al, 1987), cattle (Kopečný, 1990), and equine embryo (Brinsko et al, 1995). Subsequent changes appear to involve the dispersion of the NPB compact fibrillar mass and its reorganization into a functional nucleolus.…”

Section: Introductionmentioning

confidence: 99%

Nucleolar substructures of rabbit cleaving embryos: An immunocytochemical study

et al. 1997

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The structure‐function relationships of the nucleolar substructures were studied in preimplantation rabbit embryos, where nucleologenesis is extending over the first four cell cycles and may not be synchronous in each blastomere. Immunocytochemical methods using light and electron microscopy were applied for protein and RNA localization as well as nick translation and terminal deoxynucleotidyl transferase techniques for DNA detection. DNA was gradually associated with the periphery of the compact nucleolar precursor bodies (NPBs) but was never found inside NPBs at the four‐cell stage. In 16‐cell embryos, some NPBs displayed a reticulated periphery forming the branching network of the dense fibrillar component (DFC) surrounding the “residual body” (remnant of NPB) in the process of activation. At the 32‐cell stage, fully reticulated nucleoli were observed in each blastomere. DNA was then associated with the DFC of reticulated nucleoli. RNA was first detected at the 16 cell‐stage in close contact with the DFC as well as inside the “residual body” which was not immunolabeled with the DNA antibodies used. When observed by light microscopy, fibrillarin, nucleolin, and protein B23 displayed a changing distribution pattern during nucleologenesis. At early stages (up to the 16‐cell stage), small dot‐ and spot‐like structures were distributed within the whole nuclei. In 16‐cell embryos, these proteins started to accumulate in an irregular thin layer around the NPBs in the process of activation. The reorganization process described may be in relation with the redistribution of chromatin and nuclear/nucleolar matrix components during the activation of rDNA transcription localized in the NPB shell. In conclusion, nucleologenesis is only achieved at the fourth cell cycle in the cleaving rabbit embryo at the corresponding time when the first detectable nucleolus‐associated RNA is detectable. Our results show a good correlation between the establishment of structure and function. Mol. Reprod. Dev. 48:34–44, 1997. © 1997 Wiley‐Liss, Inc.

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Development of the nucleolus in early goat embryos

Cited by 23 publications

References 27 publications

Onset of Nucleolar and Extranucleolar Transcription and Expression of Fibrillarin in Macaque Embryos Developing In Vitro1

Onset of Nucleolar and Extranucleolar Transcription and Expression of Fibrillarin in Macaque Embryos Developing In Vitro1

Nucleologenesis and the onset of transcription in the eight‐cell bovine embryo: Fine‐structural autoradiographic study

Nucleolar substructures of rabbit cleaving embryos: An immunocytochemical study

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