49 TRANSCRIPT LEVEL OF mRNA IN BOVINE CLONED OR RE-CLONED EMBRYOS

2007 ◽  
Vol 19 (1) ◽  
pp. 142
Author(s):  
G. Jang ◽  
H. Y. Jeon ◽  
K. H. Ko ◽  
H. J. Oh ◽  
H. J. Park ◽  
...  

Gene expression in embryos played important roles during preimplantation development and had the potential to be used as an indicator for embryo viability. The purpose of this study was (1) to compare the developmental competence of cloned, or re-cloned embryos (Experiment 1); (2) to analyze the transcripts level of the related implantation, metabolic, and imprinting genes in IVF, cloned and re-cloned embryos (Experiment 2). The SCNT was performed according to the established system in our laboratory (Theriogenology 2006 65, 1800–1812). For producing cloned embryos, fetal fibroblasts as donor cells were used and a viable cloned calf was born. Recloned embryos derived from ear fibroblasts of the cloned calf, genetically same with donor fetal donor cells, were produced. The couplets were fused, chemically activated, and cultured in modified synthetic oviduct fluid (mSOF) for up to 7 days. The developmental competence up to blastocysts was observed under a microscope. The implantation (Bax, E-cad, If-tau, Hsp 70, Igf2r, and DNMT1), metabolic [LDHA (Lactate Dehydrogenase A), G6PD (Glucose-6 Phosphate Dehydrogenase), PGK (Phosphogycerate Kinase), Na/K ATPase, and Glut-1], and imprinting [GNAS (guanine nucleotide binding protein, alpha stimulating), UBE3a (ubiquitin protein ligase E3A), Mest (mesoderm specific transcript), SNRPN (small nuclear ribonucleoprotein polypeptide N), and Ndn (necdin)] genes were selected. The relative abundance (ratio to GAPDH mRNA) of gene transcripts in blastocysts was measured by conventional semi-quantitive RT-PCR. In Experiment 1, development competence of SCNT pre-implantation embryo was not different between cloned or re-cloned embryos (26% vs. 22%). In Experiment 2, the relative expression of Bax, Hsp70, If-tau, and Igf2r transcript was not different in IVF, cloned, and re-cloned embryos. Expression of E-cad and DNMT1 was higher in re-cloned embryos than any other group. Transcripts levels of LDHA, Na/K ATPase, and Glut-1 showed the similar relative abundance in IVF, cloned and re-cloned embryos. Expression of G6PD and PGF was increased in re-cloned and cloned embryos, respectively. Compared to IVF and cloned embryos, in re-cloned embryos, relative abundance of related imprinting genes (Ube3a, Mest, SNRPN, and Ndn) was increased. In conclusion, this study demonstrated that, whereas developmental competence of cloned or re-cloned embryos was not different, gene transcript levels were observed differently. It was suggested that alteration of gene expression in the re-cloned embryos derived from the cloned calf, genetically same with initial donor cells, might have affected the fetal development and births of re-cloned offspring.

Zygote ◽  
2005 ◽  
Vol 13 (3) ◽  
pp. 187-195 ◽  
Author(s):  
Goo Jang ◽  
Hyun Yong Jeon ◽  
Kyung Hee Ko ◽  
Hee Jung Park ◽  
Sung Keun Kang ◽  
...  

This study compared the developmental competence of somatic cell nuclear transfer (SCNT) embryos reconstructed with different donor cells and analysed gene expression in the resulting embryos. Bovine fetal/adult ear fibroblasts and cumulus cells were used as donor cells and the developmental competence of the reconstructed embryos was monitored. The cell number and allocation in blastocysts were determined by differential staining. The Bax, E-cad, IF-tau, Hsp (heat shock protein) 70, Igf2r (insulin-like growth factor 2 receptor), DNMT (DNA methyltransferase) 1 and Mash (mammalian achaete-scute homologue) 2 genes were selected for gene expression analysis. The relative abundance (ratio to GAPDH mRNA) of gene transcripts in blastocysts was measured by semiquantitative reverse transcription-polymerase chain reaction. In experiment 1, development of SCNT preimplantation embryos and the cell numbers of inner cell masses and trophoblasts were not different among SCNT embryos derived from different cell types. In experiment 2, the relative expression of GAPDH and Hsp 70 transcripts was similar in all embryos. The expression of Bax, Igf2r and Mash2 transcripts was significantly increased in SCNT embryos reconstructed with adult fibroblasts. The E-cad transcript levels were reduced in SCNT embryos reconstructed with fetal fibroblasts. Relative abundance of DNMT1 in SCNT embryos derived from fetal fibroblasts was increased, and IF-tau expression in SCNT embryos derived from cumulus cells was increased. In conclusion, depending on the type of donor cells, preimplantation SCNT embryos displayed marked differences in gene expression. This may affect the developmental competence of SCNT embryos reconstructed with different cell types after implantation or during fetal growth in vivo.


2020 ◽  
Vol 32 (2) ◽  
pp. 135
Author(s):  
G. Vans Landschoot ◽  
V. Savy ◽  
L. D. Ratner ◽  
V. Alberio ◽  
D. F. Salamone

Somatic cell nuclear transfer (SCNT) is an assisted reproductive technology with potential for its application in agriculture, biomedicine, and biotechnology. However, the SCNT efficiency is low. Failure in embryo production by SCNT could be associated mainly with chemical activation treatments or the donor cell type. In this context, we compare the use of latrunculin A (LatA), instead of cytochalasin B during the activation with roscovitine (Rosco), versus the treatment of donor cells with demecolcine (D-cells) followed by activation just with Rosco to compare cloning efficiency. The aim of this study was to evaluate the invitro developmental competence as well as the gene expression pattern of key genes (CDX2, OCT4, SOX2, and NANOG) in blastocysts obtained from the two treatments. To do this, cumulus-oocyte complexes were collected from cow ovaries obtained from slaughterhouses and were IVM for 21h. After cumulus-cell removal, enucleation was performed as described by Gambini et al. (2014 PLoS ONE 9, e110998; https://doi.org/10.1371/journal.pone.0110998). The G0/G1 cells or D-cells were fused to the oocytes. For activation, reconstructed zygotes were treated with 5μM ionomycin for 4min followed by 5-h incubation into different randomly activation groups: D-cells + 50μM Rosco (SCNT-Demec), G0/G1 cells + 50μM Rosco/10μM LatA (SCNT-LatA), and G0/G1 cells + 50μM Rosco/5μgmL−1 cytochalasin B (SCNT-Ctrol). Parthenogenetic controls were also included: Part-Demec, Part-LatA, and Part-Ctrol. Activated oocytes were cultured in synthetic oviductal fluid with amino acids medium until blastocyst stage. Rates of cleavage, morulae, and blastocysts were evaluated at Days 2, 5, and 7 of invitro culture, respectively. Relative abundance of mRNA coding for the four genes was compared between SCNT-Demec, SCNT-LatA, SCNT-Ctrol, and IVF groups by RTqPCR. Data was analysed by Fisher's exact test for invitro culture (P<0.05) or by one-way analysis of variance followed by Tukey post-hoc test (P=0.05). Cleavage rates from SCNT-Demec (n=247, 88%) and SCNT-LatA (n=112, 88%) were significantly higher than those from SCNT-Ctrol (n=123, 76%; Table 1). However, higher blastocyst rates were observed for the SCNT-LatA (n=112, 29%) group than for SCNT-Demec (n=247, 10%) and SCNT-Ctrol (n=123, 14%) (P<0.05). No differences were found for the relative abundance of mRNAs coding for SOX2 and CDX2 between all groups. The NANOG expression was significantly decreased in SCNT-Ctrol and SCNT-LatA compared with IVF embryos (P<0.05). The SCNT-Demec group did not differ from IVF embryos, and OCT4 expression analysis showed no difference among groups. In conclusion, LatA activation improved significantly blastocyst rates, whereas it did not affect gene expression when compared with IVF embryos. Our results suggest that this group could improve full-term developmental efficiency of SCNT embryos. Table 1.Cleavage, morulae, and blastocyst rates among the groups Group1 Treatment n Cleavage (%) Morulae (%) Blastocyst (%) SCNT-Demec Rosco 247 218 (88,26)b 41 (16,60)a 24 (9,72)a SCNT-Ctrol CB/Rosco 123 93 (75,61)a 25 (20,33)a 17 (13,82)a SCNT-LatA LatA 10μM/Rosco 112 99 (88,39)b 42 (37,50)b 33 (29,46)bc Part-Demec Rosco 141 133 (94,33)b 35 (24,82)a 20 (14,18)a Part-Ctrol CB/Rosco 84 76 (90,48)b 22 (26,19)ab 19 (22,62)ab Part-LatA LatA 10μM/Rosco 73 67 (91,78)b 30 (41,10)b 28 (38,36)c a-cStatistical differences between treatments (Fisher's test P<0.05). 1Treatments: donor cells with demecolcine (D-cells) + 50μM roscovitine (Rosco) (SCNT-Demec), G0/G1 cells + 50μM Rosco/10μM latrunculin A (LatA) (SCNT-LatA), and G0/G1 cells + 50μM Rosco/5μgmL−1 cytochalasin B (CB) (SCNT-Ctrol). Parthenogenetic controls were also included: Part-Demec, Part-LatA, and Part-Ctrol.


2005 ◽  
Vol 17 (8) ◽  
pp. 751 ◽  
Author(s):  
Mona E. Pedersen ◽  
Øzen Banu Øzdas ◽  
Wenche Farstad ◽  
Aage Tverdal ◽  
Ingrid Olsaker

In this study the synthetic oviduct fluid (SOF) system with bovine oviduct epithelial cell (BOEC) co-culture is compared with an SOF system with common protein supplements. One thousand six hundred bovine embryos were cultured in SOF media supplemented with BOEC, fetal calf serum (FCS) and bovine serum albumin (BSA). Eight different culture groups were assigned according to the different supplementation factors. Developmental competence and the expression levels of five genes, namely glucose transporter-1 (Glut-1), heat shock protein 70 (HSP), connexin43 (Cx43), β-actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), analysed as mRNA by using reverse transcription–polymerase chain reaction, were measured on bovine embryos cultured for 9 days. Gene expression of these in vitro-produced embryos was compared with the gene expression of in vivo-produced embryos. There was no significant difference found in embryo developmental competence between the Day 9 embryos in BOEC co-culture, FCS and BSA supplements in SOF media. However, differences in gene expression were observed. With respect to gene expression in in vivo and in vitro embryos, BOEC co-culture affected the same genes as did supplementation with FCS and BSA. HSP was the only gene that differed significantly between in vitro and in vivo embryos. When the different in vitro groups were compared, a significant difference between the BOEC co-culture and the FCS supplementation groups due to Glut-1 expression was observed.


2006 ◽  
Vol 18 (2) ◽  
pp. 236
Author(s):  
B. Mohana Kumar ◽  
H.-F. Jin ◽  
J.-G. Kim ◽  
S. Balasubramanian ◽  
S.-Y. Choe ◽  
...  

Abnormal gene expression is frequently observed in nuclear transfer (NT) embryos and is one of the suggested causes of the low success rates of this approach. Recent study has suggested that adult stem cells may be better donor cells for NT, as their less differentiated state may ease epigenetic reprogramming by the oocyte (Kato et al. 2004 Biol. Reprod. 70, 415-418). In the present study, we investigated the expression profile of some selected genes involved in the development of the pre-implantation embryos of in vivo- and NT-derived origin using bone marrow mesenchymal stem cells (MSCs) and porcine fetal fibroblasts (pFF) as donors. Isolated population of MSCs from porcine bone marrow were characterized by cell-surface antigen profile (CD13pos, CD105pos, CD45neg, and CD133neg) and by their extensive consistent differentiation to multiple mesenchymal lineages (adipocytic, osteocytic and chondrocytic) under controlled in vitro conditions (Pittenger et al. 1999 Science 284, 143-147). Primary cultures of pFF from a female fetus at <30 days of gestation were established. for NT, donor cells at 3-4 passages were employed. Embryos cloned from MSCs showed enhanced developmental potential compared to pFF cloned embryos, indicated by higher rates of blastocyst formation (15.3% � 4.8 and 9.0% � 3.9, respectively) and total cell number (31.5 � 7.2 and 20.5 � 5.4, respectively) in Day 7 blastocysts. Total RNA was extracted from pools (triplicates) of 10 embryos each of 8-cell, morula, and blastocyst stages of in vivo and NT origin using Dynabeads� mRNA DIRECT" kit (Dynal, Oslo, Norway). Reverse transcription was performed with a Superscript" III cDNA synthesis kit (Invitrogen, Carlsbad, CA, USA). Real-time PCR was performed on a Light cycler� using FastStart DNA Master SYBR Green I (Roche Diagnostics, Mannheim, Germany). The expression profiles of genes involved in transcription (Oct-4, Stat3), DNA methylation (Dnmt1), de novo methylation (Dnmt3a), histone deacetylation (Hdac2), anti-apoptosis (Bcl-xL), and embryonic growth (Igf2r) were determined. The mRNA of H2a was employed to normalize the levels. Significant differences (P < 0.05) in the relative abundance of Stat3, Dnmt1, Dnmt3a, Bcl2, and Igf2r were observed in pFF NT embryos compared with in vivo-produced embryos, whereas embryos derived from MSCs showed expression patterns similar to those of in vivo-produced embryos. However, Oct-4 and Hdac2 revealed similar expression profiles in NT- and in vivo-produced embryos. These results indicate that MSC-derived NT embryos had enhanced embryonic development and their gene expression pattern more closely resembled that of in vivo-produced embryos. Hence, less differentiated MSCs may have a more flexible potential in improving the efficiency of the porcine NT technique. This work was supported by Grant No. R05-2004-000-10702-0 from KOSEF, Republic of Korea.


2006 ◽  
Vol 18 (2) ◽  
pp. 233
Author(s):  
J.-G. Kim ◽  
H.-F. Jin ◽  
B.-K. Mohana ◽  
H.-J. Song ◽  
Y.-J. Jeong ◽  
...  

The amount of information gathered on the kinetics and quantitative profile of gene expression in nuclear transferred (NT) pre-implantation embryos is still scarce and limited to a handful of genes in pig. In the present study, we compared the relative abundance (RA) of six development-related genes of pre-implantation embryos from different origins. Cumulus-oocyte complexes (COCs) were matured, fertilized and cultured by the method of Abeydeera et al. (2000 Theriogenology 54, 787-797). Parthenogenetic (PA) and NT embryos were produced as described by Kim et al. (2005 Mol. Rep. Dev. 70, 308-313). Sets of 10 embryos each at 4-cell, 8-16-cell, morula, and Day 7 blastocyst stages were used to extract total RNA for analyzing the expression pattern of Bax (pro-apoptotic), Bcl-xl (anti-apoptotic), Oct-4 (pluripotent transcription), Stat3 (cytoplasmic transcription), IFN-tau (implantation) and VEGF (vasculogenesis) genes (three replicates) with real-time quantitative PCR (LightCycler�; Roche Diagnostics, Mannheim, Germany) following RNA isolation (with Dynabeads� mRNA Direct" kit; Dynal, Oslo, Norway) and cDNA amplification (Oligo (dT)12-18 primer and Superscript" III cDNA synthesis kit; Invitrogen, Carlsbad, CA, USA). The expression of each gene was normalized to Histone H2A expression. Statistically significant (P < 0.05) differences in gene expression were analyzed by ANOVA. Oct-4, Stat3, Bax, and Bcl-xl were expressed at the 4-cell stage. However, IFN-tau and VEGF were expressed at the morula stage. The expression patterns of all genes throughout the embryonic development in all types of embryos were similar. However, the relative abundance (RA) of Bax in the 8-16 cell stage of NT and PA was significantly (P < 0.05) increased as compared to that in IVP counterparts. The RA of Oct-4 and Bcl-xl did not differ throughout all stages in NT and PA embryos. There were no significant differences in all types of embryos with respect to the RA of Oct-4 and Bcl-xl with exception of the blastocysts in NT (significantly decreased, P < 0.01). The RA of Stat3 was significantly (P < 0.05) increased in the 8-16 cell stage (NT and PA) and in blastocysts (NT). Similarly, the RA of IFN-tau was significantly (P < 0.05) increased in NT blastocysts. The RA of VEGF was not significantly different in all stages and types of embryos except NT blastocysts (decreased expression, P < 0.01). These results suggest that expression patterns of Bax, Bcl-xl, Oct-4, Stat3, IFN-tau, and VEGF can be used as markers to assess the developmental competence of porcine nuclear transfer embryos. This work was supported by Grant No. 1000520040020000 from Biogreen 21, Republic of Korea.


2007 ◽  
Vol 19 (1) ◽  
pp. 144
Author(s):  
J. G. Kim ◽  
E. J. Kang ◽  
M. K. Kim ◽  
S. Y. Choe ◽  
G. J. Rho

Adult stem cells are more desirable than somatic cells for nuclear transfer (NT) because of their easy reprogrammability to resemble the genome of the zygote (Zhu et al. 2004 Biol. Reprod. 70, 1088–1095). Mesenchymal stem cells (MSCs) are a heterogeneous population of uncommitted and lineage-committed cells and have a more flexible potential as donor cells for NT. The aim of this study was to compare the developmental potential of NT embryos using undifferentiated (MSCs) and differentiated cells in the same lineage (osteocyte, adipocyte, and chondrocyte) by assessing the cleavage and blastocyst rates. Fetal fibroblasts were used as NT control. MSCs obtained from the aspirated bone marrow of a neonatal pig were cultured in advanced-DMEM (ADMEM) supplemented with 5% FCS. The differentiation potential was demonstrated by culture of MSCs at passage 3 under the conditions that were favorable for adipogenic, osteogenic, and chondrogenic development (Pittenger et al. 1999 Science 284, 143–147). For NT, cells from passages 3–5 were transferred into the perivitelline space of enucleated MII oocytes that had been in vitro-matured after collection from slaughterhouse-derived ovaries. After fusion with a needle-type electrode, eggs were cultured in 7.5 µg mL−1 cytochalasin B for 3 h, and subsequently cultured in PZM-3 medium for 6 days. Statistical significance was tested using ANOVA with Bonferroni and Duncan tests. The results are presented in Table 1. The rates of cleavage and development to blastocyst stage of NT embryos varied among donor cell sources. Most eggs (92.2 ± 2.7%) cloned with MSCs cleaved, and 47.8% of eggs developed to the blastocyst stage. In contrast, NT eggs using differentiated MSCs—osteocytes, adipocytes, chondrocytes, and controls (fetal fibroblasts)—revealed significantly (P &lt; 0.05) lower cleavage (74.5, 63.4, 74.3, and 66.4%, respectively) and blastocyst development (33.7, 30.1, 36.5, and 25.5%, respectively) rates than those using undifferentiated MSCs. The results demonstrate that the genome of donor cells with different differentiated status supports embryonic development to various degrees, and multipotent MSCs might have a greater potential in producing viable cloned porcine embryos. Table 1.Development of NT embryos with undifferentiated and differentiated cells This work was supported by Grant No. R05-2004-000-10702-0 from KOSEF, Republic of Korea.


2015 ◽  
Vol 27 (1) ◽  
pp. 206
Author(s):  
J. M. K. Nielsen ◽  
C. Wrenzycki ◽  
P. Hyttel ◽  
F. Poppicht ◽  
L. Strøbech

The purpose was to examine effects of different media for bovine in vitro oocyte maturation (IVM) and in vitro embryo culture (IVC) on blastocyst rates, morpho-kinetics, and relative abundance of mRNA of 8 genes associated with critical processes and developmental competence in the embryo. Abattoir-derived cumulus-oocyte complexes (COC) were in vitro matured (IVM) in either TCM199 [+0.5% BSA and gonadotropins (Suigonan Vet 150 I.E. mL–1)] or in a novel commercially available media (Bo-IVM), and a total of 1196 presumptive zygotes, from 4 replicates, were submitted to in vitro culture (IVC) and cultured in either SOF (+0.5% BSA) or in a novel commercially available media (Bo-IVC). Blastocyst rates and morpho-kinetics were assessed on Day 8 after fertilization. The high-quality blastocysts from each group were analysed by RT-qPCR, on single blastocysts using earlier verified primers, for BAX, BCL2L1, DNMT3A, FASN, G6PD, HSPA1A, SLC2A1, and SLC2A3. Data on blastocyst rates were analysed for statistical differences using a linear regression model, using a binary reproach and general estimating equations. One-way ANOVA was used to detect differences in the relative abundance of mRNA between groups, whereas differences between maturation and culture media were analysed by a 2-way ANOVA. Blastocyst rates in the Bo-IVM/Bo-IVC (37%), TCM199/Bo-IVC (33%), Bo-IVM/SOF (26%), and TCM199/SOF (28%) groups were significantly different from each other (P < 0.0001). Specifically, the Bo-IVM/Bo-IVC group differed significantly from both SOF-cultured groups (P < 0.01). Subjectively, this group also had embryos of the highest quality and most advanced development. Significantly increased levels of mRNA transcripts were found for embryos cultured in Bo-IVC for all genes (P < 0.05) except BCL2L1. In conclusion, the developmental rates and gene expression of in vitro-produced bovine blastocysts were affected by the use of different culture media. Increased blastocyst rates, apparently superior embryo quality, and more abundant gene expression were achieved when blastocysts were cultured in Bo-IVC culture media compared with SOF.The project was supported by The Danish Council for Strategic Research.


2005 ◽  
Vol 17 (2) ◽  
pp. 166
Author(s):  
S.K. Cho ◽  
M.R. Park ◽  
D.N. Kwon ◽  
E.K. Lee ◽  
S.J. Kang ◽  
...  

The present study was conducted to investigate the developmental competence of male and female somatic cell derived nuclear transfer (NT) porcine embryos and also the production and survival efficiency of cloned male and female piglets. Maturation of porcine COCs was accomplished by incubation in NCSU-23 medium supplemented with 0.6 mM cysteine, 10% porcine follicular fluid, 1 mM dibutyryl cyclic adenosine monophosphate, and 0.1 IU/mL human menopausal gonadotrophin for 20 h and then culture without dbcAMP and hMG for another 18 to 24 h. Fetal cells were isolated from a male fetus and two female fetuses, and cultured in ES-DMEM medium containing 10% FCS. Enucleated oocytes were fused with fetal fibroblasts (passage 4 to 15). Reconstructed embryos were cultured in NCSU-23 with 4 mg/mL BSA under mineral oil at 39°C in 5% CO2 in air for up to 6 days. NT eggs that had been activated with electric pulses and cultured for 1 or 2 days were transported to the experimental station in modified NCSU-23 with antibiotics. NT embryos were surgically transferred into the oviducts of recipients between Day 27 and Day 30; pregnancy was determined by ultrasound. The potential of NT embryos to develop into blastocysts was not different among donor cells of different origins. However, the mean cell number of in vivo female and male blastocysts (83.8 ± 46.2 to 99.2 ± 55.7) was higher than in in vitro culture of NT groups (31.4 ± 8.29 to 33.2 ± 10.15). A total of 11,535 NT embryos (1- to 8-cell stage) were surgically transferred into 66 surrogate gilts. Among fourteen pregnant gilts, four recipients aborted during the period of conception. Five pregnant gilts delivered fifteen female piglets, 1.28 ± 0.33 kg (0.48∼1.83 kg) in female piglets and 0.84±0.25 kg (0.45∼1.25 kg) in male piglets. Nine live cloned female (60.0%) and four male piglets (18.2%) were produced. According to these results, survival rates and birth weights of female cloned piglets were higher than those of cloned male piglets (P < 0.05). This study suggests that use of female, compared with male, fetal fibroblast cells as nuclear donors may increase cloning outcomes. This work was supported in part by a grant program from RDA(Biogreen21) and Cho-A, Republic of Korea.


Zygote ◽  
2013 ◽  
Vol 23 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Xian-rong Xiong ◽  
Dao-liang Lan ◽  
Jian Li ◽  
Yong Wang ◽  
Jin-cheng Zhong

SummaryInterspecies somatic cell nuclear transfer (iSCNT), a powerful tool in basic scientific research, has been used widely to increase and preserve the population of endangered species. Yak (Bos grunniens) is one of these species. Development to term of interspecies cloned yak embryos has not been achieved, possibly due to abnormal epigenetic reprogramming. Previous studies have demonstrated that treatment of intraspecies cloned embryos with (NaBu) significantly improves nuclear–cytoplasmic reprogramming and viability in vitro. Therefore, in this study, we evaluated the effect of optimal NaBu concentration and exposure time on preimplantation development of yak iSCNT embryos and on the expression patterns of developmentally important genes. The results showed that 8-cell rate, blastocyst formation rate and total cell number increased significantly compared with their untreated counterparts when yak iSCNT embryos were treated with 5 nM NaBu for 12 h after activation, but that the 2-cell stage embryo rate was not significantly different. The treatment of NaBu also increased significantly the expression levels of Oct-4 and decreased the expression levels of HDAC-2, Dnmt-1 and IGF-1; the expression patterns of these genes were more similar to that of their bovine–yak in vitro fertilization (BY-IVF) counterparts. The results described above indicated that NaBu treatment improved developmental competence in vitro and ‘corrected’ the gene expression patterns of yak iSCNT embryos.


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