Differential expression of activin subunits, activin receptors and follistatin genes in bovine oocytes and preimplantation embryos

1998 ◽  
Vol 10 (3) ◽  
pp. 293 ◽  
Author(s):  
K. Yoshioka ◽  
M. Takata ◽  
T. Taniguchi ◽  
H. Yamanaka ◽  
K. Sekikawa
Keyword(s):  
In Vitro Maturation ◽  
Preimplantation Embryos ◽  
Bovine Embryos ◽  
Cell Stage ◽  
Α Subunit ◽  
Polymerase Chain ◽  
Bovine Oocytes ◽  
Activin Receptors ◽  
Inhibin Subunits

The presence of inhibin subunits (α, βA and βB), activin binding protein follistatin and activin receptors (ActR-I, ActR-IB, ActR-II and ActR-IIB) mRNA transcripts in bovine oocytes and preimplantation embryos was examined by reverse transcription-polymerase chain reaction. Immature and matured oocytes, zygotes, 2-cell, 3–4-cell, 5–8-cell, 9–16-cell embryos, morulae, blastocysts and hatched blastocysts were produced by in vitro maturation, fertilization and culture for this study. Activin βA subunit and follistatin transcripts were detected in all of the stages tested. However, α subunit transcripts were detected only in oocytes (immature and matured), blastocysts and hatched blastocysts, and no βB subunit transcripts were found in any of the stages. Whereas ActR-I transcripts were detectable in all stages, ActR-IB transcripts were not detectable in oocytes or embryos except in matured oocytes. Activin type II receptors (ActR-II and ActR-IIB) transcripts were detectable in oocytes and embryos except for ActR-IIB, which was not found in the 5–8-cell stage embryos. The results suggest that bovine embryos may produce activin A (homodimer of the βA subunits) at least from zygotes to morulae. Furthermore, bovine oocytes and embryos express the activin receptors mainly by the combination of ActR-I and either ActR-II or ActR-IIB.

Treatment with roscovitine and butyrolactone I prior to in vitro maturation alters blastocyst production

Zygote ◽  
2019 ◽  
Vol 28 (1) ◽  
pp. 24-31 ◽  
Author(s):  
Rosiara Rosária Dias Maziero ◽  
Carlos Renato de Freitas Guaitolini ◽  
Daniela Martins Paschoal ◽  
André Maciel Crespilho ◽  
Bianca Andriolo Monteiro ◽  
...  
Keyword(s):  
In Vitro Maturation ◽  
Study Groups ◽  
Embryo Cryopreservation ◽  
Control Group ◽  
Bovine Embryos ◽  
Nuclear Maturation ◽  
Oocyte Meiosis ◽  
Maturation Index ◽  
Bovine Oocytes

SummaryThis study evaluated the effects of oocyte meiosis inhibitors roscovitine (ROS) and butyrolactone I (BL-I) on in vitro production of bovine embryos. Bovine oocytes were maintained in pre in vitro maturation (pre-IVM) with 25 µM ROS or 100 µM BL-I for 24 h to delay meiosis and for 24 h in in vitro maturation (IVM). Following this treatment, the nuclear maturation index was evaluated. All embryos degenerated following this procedure. In the second set of experiments, oocytes were maintained for 6 or 12 h in pre-IVM with the following three treatments: ROS (25 µM or 12.5 µM), BL-I (100 µM or 50 µM) or a combination of both drugs (6.25 µM ROS and 12.5 µM BL-I). Oocytes were cultivated for 18 or 12 h in IVM. When a meiosis-inducing agent was used during pre-IVM for 24 h, more degenerated oocytes were observed at the end of the IVM period. This effect decreased when the meiotic blocking period was reduced to 6 or 12 h. No significant differences were observed in the blastocyst production rate of oocytes in pre-IVM for 6 h with ROS, BL-I, or ROS + BL-I compared with that of the control group (P > 0.05). However, inhibition of oocytes for 12 h resulted in decreased embryo production compared with that in the controls (P < 0.05). There was no difference in the post-vitrification embryo re-expansion rate between the study groups, showing that the meiotic inhibition for 6 or 12 h did not alter the embryo cryopreservation process.

315 SELECTION OF BOVINE OOCYTES BY BRILLIANT CRESYL BLUE BEFORE IN VITRO MATURATION IMPROVES BLASTOCYST DEVELOPMENT

2007 ◽  
Vol 19 (1) ◽  
pp. 273 ◽  
Author(s):  
A. Sugulle ◽  
S. Katakawa ◽  
S. Yamamoto ◽  
S. Oomori ◽  
I. Itou ◽  
...  
Keyword(s):  
Embryo Development ◽  
In Vitro Maturation ◽  
Control Group ◽  
Blastocyst Development ◽  
Cell Stage ◽  
Brilliant Cresyl Blue ◽  
Cresyl Blue ◽  
Bovine Oocytes ◽  
Selection Of

The morphological identification of immature oocytes has commonly been used to select the bovine oocytes for IVF. However, &lt;30% of the recovered oocytes reach the blastocyst stage after fertilization, and this is probably due to the quality of the oocytes at the beginning of maturation. The brilliant cresyl blue (BCB) stain determines the activity of glucose-6-phosphate dehydrogenase, an enzyme synthesized in growing oocytes. The aim of this study was to evaluate the effect of the BCB stain on the selection of bovine oocytes and on the subsequent embryo development for in vitro production (IVP). Cumulus–oocyte complexes (COCs) were collected by the aspiration of 2- to 6-mm follicles. A total of 559 oocytes were divided into 2 groups: (1) a control group, immediately cultured, and (2) a BCB-incubated group. After 90 min of BCB staining (Pujol et al. 2004 Theriogenology 61, 735–744), the oocytes were divided into oocytes with blue cytoplasm (BCB+) and oocytes without blue cytoplasm (BCB−). The COCs were matured for 20 h in TCM-199 supplemented with 5% calf serum (CS) and 0.02 mg mL−1 FSH at 38.5°C under an atmosphere of 5% CO2 in air. The matured COCs were inseminated with 5 × 106 sperm mL−1. After 18 h of gamete co-culture, the presumed zygotes were cultured in CR1aa supplemented with 5% CS for 9 days at 38.5°C under an atmosphere of 5% CO2, 5% O2, and 90% N2. Embryonic development was evaluated at 48 h after IVF (proportion of ≥5-cell stage, the total cleavage rates) and on Days 7 to 9 (blastocyst rate). The experiment was replicated 5 times, and the data were analyzed by a chi-square test and ANOVA. The results are presented in Table 1. The proportion of embryos with ≥5-cell stage was significantly higher (P &lt; 0.01) in the BCB+ group than in the BCB− group, but not in the control group. The total cleavage rate for the BCB+ embryos was significantly higher than that of either the BCB− or the control group (P &lt; 0.01). There were also significant differences (P &lt; 0.01) in the blastocyst development between the BCB+ and BCB− embryos and between the BCB− and the control embryos (P &lt; 0.05). This result showed that the selection of bovine oocytes by BCB staining before in vitro maturation may be useful for selecting oocytes that are developmentally competent up to Day 9 for IVP. Table 1.Effect of selection of oocytes by brilliant cresyl blue (BCB) staining on the subsequent embryo development of in vitro-matured/in vitro-fertilized bovine embryos

scholarly journals Nicotinamide Supplementation during the In Vitro Maturation of Oocytes Improves the Developmental Competence of Preimplantation Embryos: Potential Link to SIRT1/AKT Signaling

Cells ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1550 ◽  
Author(s):  
Marwa El Sheikh ◽  
Ahmed Atef Mesalam ◽  
Muhammad Idrees ◽  
Tabinda Sidrat ◽  
Ayman Mesalam ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
In Vitro Maturation ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Akt Signaling ◽  
Developmental Competence ◽  
Preimplantation Embryos ◽  
Vitamin B3 ◽  
Cell Stage

Nicotinamide (NAM), the amide form of vitamin B3, plays pivotal roles in regulating various cellular processes including energy production and maintenance of genomic stability. The current study aimed at deciphering the effect of NAM, when administered during in vitro maturation (IVM), on the developmental competence of bovine preimplantation embryos. Our results showed that low NAM concentrations reduced the oxidative stress and improved mitochondrial profile, total cleavage and 8–16 cell stage embryo development whereas the opposite profile was observed upon exposure to high NAM concentrations (10 mM onward). Remarkably, the hatching rates of day-7 and day-8 blastocysts were significantly improved under 0.1 mM NAM treatment. Using RT-qPCR and immunofluorescence, the autophagy-related (Beclin-1 (BECN1), LC3B, and ATG5) and the apoptotic (Caspases; CASP3 and 9) markers were upregulated in oocytes exposed to high NAM concentration (40 mM), whereas only CASP3 was affected, downregulated, following 0.1 mM treatment. Additionally, the number of cells per blastocyst and the levels of SIRT1, PI3K, AKT, and mTOR were higher, while the inner cell mass-specific transcription factors GATA6, SOX2, and OCT4 were more abundant, in day-8 embryos of NAM-treated group. Taken together, to our knowledge, this is the first study reporting that administration of low NAM concentrations during IVM can ameliorate the developmental competence of embryos through the potential regulation of oxidative stress, apoptosis, and SIRT1/AKT signaling.

Spent culture medium analysis from individually cultured bovine embryos demonstrates metabolomic differences

Zygote ◽  
2017 ◽  
Vol 25 (6) ◽  
pp. 662-674 ◽  
Author(s):  
Kayla J. Perkel ◽  
Pavneesh Madan
Keyword(s):  
Culture Medium ◽  
Physiological State ◽  
Proton Nuclear Magnetic Resonance ◽  
Preimplantation Embryos ◽  
Bovine Embryos ◽  
Cleavage Rate ◽  
Cell Stage ◽  
Isoleucine Leucine ◽  
H Nmr

SummarySpent culture medium can provide valuable information regarding the physiological state of a bovine preimplantation embryos through non-invasive analysis of the sum/depleted metabolite constituents. Metabolomics has become of great interest as an adjunct technique to morphological and cleavage-rate assessment, but more importantly, in improving our understanding of metabolism. In this study, in vitro produced bovine embryos developing at different rates were evaluated using proton nuclear magnetic resonance (1H NMR). Spent culture medium from individually cultured embryos (2-cell to blastocyst stage) were divided into two groups based on their cleavage rate fast growing (FG) and slow growing (SG; developmentally delayed by 12–24 h), then analyzed by a 600 MHz NMR spectrometer. Sixteen metabolites were detected and investigated for sum/depletion throughout development. Data indicate distinct differences between the 4-cell SG and FG embryos for pyruvate (P < 0.05, n = 9) and at the 16-cell stage for acetate, tryptophan, leucine/isoleucine, valine and histidine. Overall sum/depletion levels of metabolites demonstrated that embryos produced glutamate, but consumed histidine, tyrosine, glycine, methionine, tryptophan, phenylalanine, lysine, arginine, acetate, threonine, alanine, pyruvate, valine, isoleucine/leucine, and lactate with an overall trend of higher consumption of these metabolites by FG groups. Principal component analysis revealed distinct clustering of the plain medium, SG, and FG group, signifying the uniqueness of the metabolomic signatures of each of these groups. This study is the first of its kind to characterize the metabolomic profiles of SG and FG bovine embryos produced in vitro using 1H NMR. Elucidating differences between embryos of varying developmental rates could contribute to a better understanding of embryonic health and physiology.

The effect of vitrification of immature bovine oocytes to the subsequent in vitro development and gene expression

Zygote ◽  
2014 ◽  
Vol 23 (6) ◽  
pp. 933-942 ◽  
Author(s):  
Marwa S. Faheem ◽  
E. Baron ◽  
I. Carvalhais ◽  
A. Chaveiro ◽  
K. Pavani ◽  
...  
Keyword(s):  
Molecular Level ◽  
Blastocyst Stage ◽  
Developmental Competence ◽  
Cell Stage ◽  
Maturation Rate ◽  
Developmental Rates ◽  
Polymerase Chain ◽  
Vitro Development ◽  
Bovine Oocytes

SummaryImmature bovine oocytes were vitrified using the cryotop method and their post-warming survivability and capability to undergo in vitro maturation, fertilization and subsequent embryonic development were evaluated. In addition throughout the embryonic 2-cell, 4-cell, morula and blastocyst stages, the expression of four developmentally important genes (Cx43, CDH1, DNMT1 and HSPA14) was analysed using the real-time polymerase chain reaction (PCR). Immature oocytes (n = 550) were randomly assigned to non-vitrified (fresh) or cryotop vitrification groups using ethylene glycol (EG) with 1,2 propanediol (PROH) or dimethylsulphoxide (DMSO). After warming, oocytes survivability, embryo cleavage and embryonic developmental rates were not statistically different between the two cryoprotectants groups. However, the DMSO group had a lower (P < 0.05) oocyte maturation rate compared with the fresh and PROH groups. For morula and blastocyst rates, the DMSO group achieved a lower (P < 0.05) morula rate compared with the fresh group, while at the blastocyst stage, there were no differences between fresh and both cryoprotectants groups. For molecular analysis, at the 4-cell stage, most studied genes showed an inconsistent pattern of expression either from the PROH or DMSO groups. Noteworthily, these differences were limited at the morula and blastocyst stages. In conclusion, the cryotop method is sufficient for vitrification of immature bovine oocytes, both for embryonic developmental competence and at the molecular level. Moreover, PROH showed some advantage over DMSO as a cryoprotectant.

198 THE EFFECT OF SOURCE AND IN VITRO MATURATION ON THE ABUNDANCE OF MATERNAL mRNA OF SELECTED GENES IN FOLLICULAR BOVINE OOCYTES AND THEIR INFLUENCE ON IN VITRO DEVELOPMENT

2011 ◽  
Vol 23 (1) ◽  
pp. 199
Author(s):  
T. Somfai ◽  
K. Imai ◽  
M. Kaneda ◽  
S. Akagi ◽  
S. Haraguchi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Embryo Development ◽  
In Vitro Maturation ◽  
Blastocyst Stage ◽  
Cell Stage ◽  
In Vitro Development ◽  
Before And After ◽  
Vitro Development ◽  
Bovine Oocytes

The aim of the present study was to investigate the effect of oocyte source and in vitro maturation (IVM) on the expression of selected genes in bovine oocytes and their contribution to in vitro embryo development. Follicular oocytes were collected either by ovum pick-up from live cows or by the aspiration of ovaries of slaughtered cows following storage in Dulbecco’s PBS at 15°C for overnight. In vitro maturation was performed according to the method of (Imai et al. 2006 J. Reprod. Dev. 52, 19–29 suppl.). Gene expression was assessed before and after IVM by real-time PCR. The following genes were investigated: GAPDH, G6PDH, ACTB, H2A, CCNB1, MnSOD, OCT4, SOX2, CX43, HSP70, GLUT8, PAP, GDF9, COX1, ATP1A1, CDH1, CTNNB1, AQP3, DYNLL1, DYNC 1/1, and PMSB1. In brief, mRNA was extracted from 20 oocytes per sample using a Qiagen RNeasy Micro Kit (Qiagen, Valencia, CA). Gene expression was analysed by a Roche Light Cycler 480 device and software (Roche, Indianapolis, IN). Relative expression of each gene was normalized to CCNB1, which in preliminary experiments appeared the most stably expressed irrespective of oocyte source and meiotic stage. Three replications were performed. Data were analysed by paired t-test. In immature ovum pick-up oocytes, genes related to metabolism (GAPDH, G6PDH, GLUT8) and stress (MnSOD, HSP70), and also OCT4, ATP1A1, and DYNC1/1 showed significantly (P < 0.05) higher expression compared with immature oocytes collected from slaughtered-stored ovaries. The expression of GDF9, GLUT8, CTNNB1, and PMSB1 was significantly (P < 0.05) reduced during IVM irrespective of the oocyte source. In a second experiment, IVF IVM oocytes showing an early (at 22 to 25 h after IVF) or late (at 27 to 30 h after IVF) first cleavage were either cultured in vitro or analysed for gene expression at the 2-cell stage. A higher (P < 0.05) rate of early-cleaving oocytes developed to the blastocyst stage compared with the rate of late-cleaving ones (46.2% v. 15.6%, respectively). Nevertheless, only ATP1A1 showed significantly reduced (P < 0.05) expression in late-cleaving embryos compared with early-cleaving ones. Our results suggest that although removal and storage of ovaries and IVM caused a reduction in the relative abundance of several genes in oocytes, in most cases, this did not affect embryo development. Among the genes studied, only ATP1A1 was correlated with in vitro development.

170 EXPRESSION PATTERN OF THE Sox2 GENE IN BOVINE OOCYTES AND IN VITRO-DERIVED EMBRYOS

2008 ◽  
Vol 20 (1) ◽  
pp. 165 ◽  
Author(s):  
T. A. L. Brevini ◽  
S. Antonini ◽  
F. Cillo ◽  
G. Pennarossa ◽  
S. Colleoni ◽  
...  
Keyword(s):  
Expression Pattern ◽  
Inner Cell Mass ◽  
False Negative ◽  
Cell Mass ◽  
Preimplantation Embryos ◽  
Cell Stage ◽  
Developmental Potential ◽  
Sox2 Expression ◽  
Bovine Oocytes

Sox2 is a member of the Sox (SRY-related HMGbox) family. It acts to maintain developmental potential and marks the pluripotent lineage of the early mouse embryo; in particular, as in the case of Oct-4 and Nanog, Sox2 is expressed specifically in the inner cell mass (ICM) and in the epiblast of this species. Moreover, it plays an important role in the transcription network that maintains stem cell pluripotency, interacting with other factors such as Oct-4 and Nanog. Little information is available on this gene in bovine; therefore aims of the present study were: a) to identify and characterize the Sox2 expression profile in bovine oocytes and preimplantation embryos; and b) to investigate its expression pattern in ICM and trophectoderm (TE). Bovine oocytes and embryos were obtained by in vitro maturation and fertilization; blastocysts at Day 7 post-insemination underwent microsurgery to separate TE from ICM. mRNA was isolated from 3 pools, each consisting of 5 MII oocytes, 2-, 4-, 8-, and 16-cell embryos, morulae, blastocysts, ICMs, and TEs. Semi-quantitative analysis of Sox2 expression was performed in the exponential phase of PCR amplification using rabbit globin as exogenous control. Data were analyzed with one-way ANOVA, followed by multiple pairwise comparisons with Tukey test (SigmaStat 2.03, SPSS, Inc., Chicago, IL, USA). Values are presented as mean � SEM and differences of P ≤ 0.05 are considered significant. In order to rule out false negative results, PCR amplifications of isolated ICMs and TEs were extended to the plateau phase. Fragment identity was confirmed by sequencing. Comparison of bovine Sox2 cDNA sequence (EMBL AM774325) with databases revealed a 98%, 93%, and 87% homology with sheep, human, and mouse, respectively. Sox2 mRNA was detectable in oocytes as well as in embryos at the different developmental stages analyzed. Semi-quantitative expression studies revealed that Sox2 was present as both maternal and embryonic transcript; in particular, a statistically significant increase from the 8-cell stage, concomitant with embryo genome activation, was observed. Differently from the mouse, Sox2 was expressed in both bovine ICM and TE, resembling the profile previously shown for Oct-4 (van Eijk et al. 1999 Biol. Reprod. 60, 1093–1103), and suggesting that Sox2 expression might be regulated by Oct-4 also in bovine, as described in mouse and human. These findings also suggest that its expression may become restricted to the ICM only at the expanded hatched stage, as previously described for Oct-4 in pig embryos (Vejlsted et al. 2006 Mol. Reprod. Dev. 73, 709–718). This work was supported by PRIN 2006, FIRST 2005, TECLA-MIUR, and EUROSTELLS-ESF.

77 EFFECT OF HEAT SHOCK DURING IN VITRO MATURATION ON HETEROCHROMATIN COMPACTION IN BOVINE EMBRYOS AT 4- AND 8-CELL STAGES: PRELIMINARY STUDY

2015 ◽  
Vol 27 (1) ◽  
pp. 132
Author(s):  
L. S. A. Camargo ◽  
T. Aguirre-Lavin ◽  
P. Adenot ◽  
T. D. Araujo ◽  
E. D. Souza ◽  
...  
Keyword(s):  
Heat Shock ◽  
In Vitro Maturation ◽  
Gene Activation ◽  
Developmental Competence ◽  
Bovine Embryos ◽  
Cleavage Rate ◽  
Cell Stage ◽  
Morphological Criteria ◽  
Preliminary Study

High temperatures cause several reproductive losses in cattle. Under in vitro conditions, heat shock decreases oocyte developmental competence and influences embryonic gene expression (Gendelman and Roth 2012 Anim. Reprod. Sci. 134, 125–134). This preliminary study aimed to evaluate whether heat shock during oocyte in vitro maturation (IVM) could have any further effect on chromatin remodelling of fertilized embryos at 4- and 8-cell stages, once such modifications are required for the gene activation in bovine embryos. We evaluated the distribution of heterochromatin 1 (HP1β) and of histone H3 trimethylated at lysine 9 (H3K9me3), both reportedly correlated with heterochromatin formation, in 4- and 8-cell stage embryos derived from control (C) and heat-shocked (HS) bovine oocytes. Immature cumulus-oocyte complexes (COC) collected from crossbred cows in Brazil were exposed for 12 h to 38.8°C (C group) or 41.0°C (HS group) followed by 12 h at 38.8°C, totalizing 24 h of IVM at 5% CO2 in air. Oocytes were in vitro fertilized (IVF) with non-sexed sperm and denuded zygotes were in vitro cultured in CR2aa medium at 38.8°C and 5% CO2, 5% O2 and 90% N2. Four- and 8-cell embryos at 44 h post-IVF were fixed in 4% paraformaldehyde and stained with anti-mouse HP1β and anti-rabbit H3K9me3 first antibodies. Immunofluorescence was evaluated by confocal microscopy (Zeiss LSM 700, MIMA platform, INRA) and 3D images processed by ZEN Lite software (Zeiss, Jena, Germany). Three different distribution patterns of fluorescence were identified based on morphological criteria: diffuse, little clusters, and big clusters. Proportions of embryos in every distribution pattern were compared between C and HS groups by Chi-squared test. No difference (P > 0.05) on cleavage rate was found between C and HS groups until 44 h post-fertilization. Embryos at the 4-cell stage from HS group displayed an increased (P < 0.01) proportion of nuclei with H3K9m3 big clusters (44%, n = 7/16 embryos), whereas embryos from C group displayed only few nuclei with this pattern (5%, n = 1/18). At the 8-cell stage, distribution of H3K9m3 was similar (P > 0.05) between C and HS groups. For HP1β, embryos at the 4-cell stage from HS group displayed an increased (P < 0.05) proportion of nuclei with little clusters (81%, n = 13/16 embryos), whereas embryos from C group had low proportion of nuclei with this same pattern (40%, n = 7/18). Mostly 4-cell stage embryos from C group presented the diffuse pattern (61%, n = 11/18 v.18%, n = 3/16 in the HS group; P < 0.05). At the 8-cell stage, some embryos from the C group (31%, n = 5/16) still showed nuclei with diffuse distribution of HP1β, whereas no nucleus with this pattern was found for the HS group. These preliminary data suggest that bovine embryos derived from heat-shocked oocytes can display precocious heterochromatin compaction, represented by the accumulation of H3K9me3 and HP1β at the 4-cell stage, compared with embryos derived from non-heat-shocked oocytes, which may affect embryonic genome activation with consequences for further gene expression.Research was supported by CNPq, FAPEMIG, FAPES and Laboratoire d'Excellence Revive (Investissement d'Avenir, ANR-10-LABX-73).

scholarly journals Heat shock during in vitro maturation induces chromatin modifications in the bovine embryo

Reproduction ◽  
2019 ◽  
Vol 158 (4) ◽  
pp. 313-322
Author(s):  
Luiz Sergio Almeida Camargo ◽  
Tiphaine Aguirre-Lavin ◽  
Pierre Adenot ◽  
Thamiris Dornelas Araujo ◽  
Vivian Rachel Araujo Mendes ◽  
...  
Keyword(s):  
Heat Shock ◽  
In Vitro Maturation ◽  
Cell Number ◽  
Developmental Competence ◽  
Bovine Embryo ◽  
Cell Stage ◽  
Early Embryos ◽  
Further Development ◽  
Bovine Oocytes

Heat stress compromises bovine oocyte developmental competence, but the effects of high temperature during oocyte maturation on embryo chromatin organization is unknown. In this study bovine oocytes were exposed to heat shock (41°C) for 12 h during in vitro maturation and then submitted to in vitro fertilization. The heat shock did not affect (P > 0.05) the cleavage but reduced (P < 0.01) the blastocyst rate on Day 7 and Day 8. No effect (P > 0.05) on total cell number was found, but the heat shock increased (P < 0.05) the proportion of apoptotic cells in blastocysts at Day 8. Immunofluorescence analysis of H3K9me3 and HP1 was performed in embryos at 52 h post in vitro fertilization. An accumulation of H3K9me3 in the nuclei of embryos derived from heat-shocked oocytes at four-cell and eight-cell stages was found. Also, a non-expected higher proportion (P < 0.05) of four-cell stage embryos displaying nuclei with increased HP1 fluorescence was observed, suggesting an abnormal chromatin compaction in embryos from heat-shocked oocytes. Embryos at eight-cell stage derived from heat-shocked oocytes displayed lower (P < 0.05) relative amount of HSP40 transcripts than control ones. In conclusion, heat shock before fertilization has an effect on embryo chromatin, influencing the accumulation of H3K9me3 and HP1 in early embryos as well as further development.

scholarly journals Ribosomal RNA gene expression and chromosome aberrations in bovine oocytes and preimplantation embryos

Reproduction ◽  
2001 ◽  
pp. 21-30 ◽  
Author(s):  
P Hyttel ◽  
D Viuff ◽  
T Fair ◽  
J Laurincik ◽  
PD Thomsen ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Chromosome Aberrations ◽  
Rrna Genes ◽  
Preimplantation Embryos ◽  
Fertilization In Vitro ◽  
Bovine Embryos ◽  
Cell Stage ◽  
Oocyte Growth

This review focuses on the key features of development of the bovine oocyte and embryo, with comparisons of the developmental characteristics of embryos produced in vivo and in vitro. The oocyte is transcriptionally quiescent in the primordial and primary follicle. In the secondary follicle transcription is initiated in the oocyte and a ribosome-synthesizing nucleolus is established in this cell. Transcription and nucleolar activity are enhanced in the tertiary follicle during oocyte growth. When the oocyte reaches approximately 110 microm in diameter, corresponding to a follicle of about 3 mm in diameter, transcription ceases and the nucleolus is inactivated, forming a dense spherical remnant. During the final phase of follicular dominance this remnant becomes vacuolated and, in conjunction with resumption of meiosis, it disperses. The rRNA genes are apparently re-activated during the four-cell stage, that is, the third cell cycle after fertilization, but a nucleolus is not formed. During the subsequent cell cycle, that is, during the eight-cell stage, ribosome-synthesizing nucleoli are again established. Bovine embryos produced in vitro apparently display the same pattern of nucleolus development as that in embryos developed in vivo. Examination of the ploidy of embryonic cells using fluorescence in situ hybridization has revealed that the production of bovine embryos in vitro is associated with increased chromosome aberrations in the embryos. Blastocysts produced in vitro display a significantly higher rate of mixoploidy, that is, when the embryo consists of both normal diploid and abnormal polyploid cells, than that in embryos developed in vivo. The rate of mixoploidy among embryos produced in vitro increases with increasing developmental stage. Moreover, after fertilization in vitro, initially there is a high rate of 'true' polyploidy, that is, when all cells of the embryos are polyploid. However, the polyploid embryos are eliminated before they cleave beyond the eight-cell stage, the stage at which major activation of the embryonic genome occurs in cattle.

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