Effect of Sex of Embryo on Developmental Competence, Epigenetic Status, and Gene Expression in Buffalo (Bubalus bubalis) Embryos Produced by Hand-Made Cloning

Effects of epigenetic modifier on the developmental competence and quantitative expression of genes in male and female buffalo (Bubalus bubalis) cloned embryos

Adult male and female Murrah buffalo fibroblast cells were used as donors for the production of embryos using handmade cloning. Both donor cells and reconstructed embryos were treated with 50 nM trichostatin-A (TSA) and 7.5 nM 5-aza-2'-deoxycytidine (5-aza-dC). The blastocyst rate of both treated male (40.1% ± 2.05) and female (37.0% ± 0.83) embryos was significantly lower than in untreated control males (49.7% ± 3.80) and females (47.2% ± 2.44) but their apoptotic index was lower (male, control: 5.90 ± 0.48; treated: 4.96 ± 0.31): (female, control: 8.11 ± 0.67; treated: 6.65 ± 0.43) and epigenetic status in terms of global acetylation and methylation of histone was significantly improved. The expression level of hypoxanthine-guanine phosphoribosyltransferase (HPRT) was higher (P < 0.05) and that of PGK, G6PD, OCT 4, IFN-tau and CASPASE3 was significantly lower (P < 0.05) in treated male blastocyst than control and the expression levels of DNMT1, IGF1R and BCL-XL were not significantly different between the two groups. In the female embryos, the relative mRNA abundance of OCT4 was significantly higher (P < 0.05), and that of XIST and CASPASE3 was significantly lower (P < 0.05) in the epigenetic modifier-treated group compared with that of the control group, whereas the expression levels of HPRT, PGK, G6PD, DNMT1, IFN-tau, IGF1R and BCL-XL were not significantly different between the two groups. In both embryos, a similar effect of treatment was observed on genes related to growth and development, but the effect on the expression of X-linked genes varied. These results indicate that not all X-linked genes respond to TSA and 5-aza-dC treatment in the same manner.

In vitro production of desired sex ovine embryos modulating polarity of oocytes for sex-specific sperm binding during fertilization

The present study aimed to modulate the oxidative status-mediated polarity of the oocytes for sex-specific sperm fertilization to generate desired sex embryos. In vitro embryos were produced at different oxidative status, varying O₂ concentrations, and without/with l-carnitine in maturation and culture media. The majority of the embryos produced at high oxidative stress were males whereas; low oxidative status favoured female embryos production. Low O₂ doubled the proportion of female embryos (10.59 vs 21.95%); however, l-carnitine supplementation in media increased approximately seven-folds of the female embryos (12.26 vs. 77.62%) production. Oocytes matured at high oxidative status were in the repolarized state favouring positively charged Y sperm fertilization to produce significantly more male embryos. Low oxidative status favoured negatively charged X sperm fertilization to the oocytes in the depolarized state to produce more female embryos. Intracellular ROS was significantly low in female embryos than in males; however, female embryos were more stressful than males. The study concluded that the oxidative status-mediated alteration in pH of the medium to modulate the intracellular positive ions is the main critical factor to influence the sex of embryos through sex-specific sperms fertilization to the oocytes as per their polarity.

Effect of Dickkopf-1 and colony stimulating factor-2 on the developmental competence, quality, gene expression and live birth rate of buffalo (Bubalus bubalis) embryos produced by hand-made cloning

A functional canonical WNT signaling pathway exists in preimplantation embryos and inhibits embryonic development. Recent studies suggest that this pathway is over-expressed in nuclear transferred (NT), compared to IVF embryos. The present study investigated the effects of Dickkopf-1 (DKK1), an inhibitor of canonical WNT signaling pathway and colony stimulating factor-2 (CSF2), an embryokine, on the developmental competence, quality, gene expression and live birth rate of NT buffalo embryos produced by Hand-made cloning (HMC). Following supplementation of the in vitro culture medium on day 5 with DKK1 (100 ng/mL), CSF2 (10 ng/mL), DKK1+CSF2 or no supplementation (control), the blastocyst rate was higher (P < 0.05) with DKK1 and DKK1+CSF2 (42.6 ± 1.4% and 46.6 ± 0.9%, respectively) than with CSF2 or controls (40.6 ± 1.3% and 39.0 ± 1.3%, respectively). The apoptotic index of the blastocysts was lower (P < 0.05) for DKK1, CSF2 and DKK1+CSF2 groups (3.44 ± 0.14, 3.39 ± 0.11 and 3.11 ± 0.22, respectively) compared to controls (6.64 ± 0.25), and was similar to that of the IVF blastocysts (3.67 ± 0.18). Although the total cell number was similar for the DKK1, CSF2, DKK1+CSF2 and control groups (200.4 ± 3.05, 196.4 ± 3.73, 204.7 ± 3.71 and 205 ± 4.03, respectively), the inner cell mass:trophectoderm cell number ratio of DKK1, CSF2 and DKK1+CSF2 groups (0.21 ± 0.01, 0.17 ± 0.01 and 0.22 ± 0.02, respectively) was higher (P < 0.05) than controls (0.13 ± 0.01) and was similar to that of IVF blastocysts (0.19 ± 0.01). Treatment with DKK1 or CSF2 or both increased (P < 0.05) the expression level of OCT4, NANOG,SOX2, GATA6, BCL2, PTEN, P53, FGF4, GLUT1 and IFN-τ, and decreased that of C-MYC, CDX2, CASPASE, DNMT3a, TCF7 and LEF1 in blastocysts, compared to controls. Transfer of DKK1-treated embryos to 13 recipients resulted in 4 pregnancies (30.8%; 2 live births, one abortion and one currently at 9 months of pregnancy) whereas, transfer of DKK1+CSF2-treated embryos to 16 recipients, resulted in 4 pregnancies (25.0%), all of which resulted in live births. No pregnancy was obtained after transfer of control and CSF-treated embryos to 12 and 16 recipients, respectively. These results suggest that DKK1 treatment of NT embryos increases the blastocyst, conception and live birth rate, and improves their quality whereas, CSF2 treatment, does not affect the blastocyst, conception and live birth rate despite improvement in embryo quality.

Developmental dynamics of cloned Mexican bighorn sheep embryos using morphological quality standards

The developmental dynamics of cloned Mexican bighorn sheep (Ovis canadensis mexicana) embryos were evaluated based on morphological quality standards. Categories determined by standards were correlated with the embryonic development stage, number of nuclei and viability. The results showed no differences in the blastocyst rate between the experimental (cloned Mexican bighorn sheep embryos) and control (parthenogenetic domestic sheep embryos) groups (p > .05), while type IV fragmentation was higher in clones (p < .05). The standards allowed for the identification of embryos that divided at least once or fragmented after 24 hr of culture. The highest percentage of morulae appeared at 96 hr, the final stages of development: nonsegmented, blocked, fragmented and blastocysts appeared at 192 hr. Embryonic quality decreased over time, making 96 hr the ideal time point to predict the final morphological quality of embryos. Nuclear staining of the morulae and blastocysts showed that higher embryo quality was associated with a higher percentage of normal and viable blastomeres. The evaluated criteria allowed for descriptions of the dynamics, stage and quality of cloned Mexican bighorn sheep embryos with a high degree of reliability. In addition, developmental anomalies, including fragmentation, multinucleation and blocking, were identified.

Difference in Developmental Kinetics of Y-Specific Monoclonal Antibody Sorted Male and Female In Vitro Produced Bovine Embryos

Sex-related growth differences between male and female embryos remain an attractive subject for reproductive biologists. This study aimed to investigate the endogenous factors that play a crucial role in the pace of early development between male and female bovine embryos. Using sex pre-selected semen by Y-specific monoclonal antibodies for the production of bovine embryos, we characterized the critical endogenous factors that are responsible for creating the development differences, especially during the pre-implantation period between male and female embryos. Our results showed that at day seven, (57.8%) Y-sperm sorted in vitro cultured embryos reached the expanded blastocyst (BL) stage, whereas the X-sperm sorted group were only 25%. Y-BLs showed higher mRNA abundance of pluripotency and developmental competency regulators, such as Oct4 and IGF1-R. Interestingly, Y-sperm sorted BLs had a homogeneous mitochondrial distribution pattern, higher mitochondrial membrane potential (∆Ѱ_m), efficient OXPHOS (oxidative phosphorylation) system and well-encountered production of ROS (reactive oxygen species) level. Moreover, Y-blastocysts (BLs) showed less utilization of glucose metabolism relative to the X-BLs group. Importantly, both sexes showed differences in the timing of epigenetic events. All these factors directly or indirectly orchestrate the whole embryonic progression and may help in the faster and better quality yield of BL in the Y-sperm sorted group compared to the X counterpart group.

Sex affects immunolabeling for histone 3 K27me3 in the trophectoderm of the bovine blastocyst but not labeling for histone 3 K18ac

The mammalian embryo displays sexual dimorphism in the preimplantation period. Moreover, competence of the embryo to develop is dependent on the sire from which the embryo is derived and can be modified by embryokines produced by the endometrium such as colony stimulating factor 2 (CSF2). The preimplantation period is characterized by large changes in epigenetic modifications of DNA and histones. It is possible, therefore, that effects of sex, sire, and embryo regulatory molecules are mediated by changes in epigenetic modifications. Here it was tested whether global levels of two histone modifications in the trophectoderm of the bovine blastocyst were affected by sex, sire, and CSF2. It was found that amounts of immunolabeled H3K27me3 were greater (P = 0.030) for male embryos than female embryos. Additionally, labeling for H3K27me3 and H3K18ac depended upon the bull from which embryos were derived. Although CSF2 reduced the proportion of embryos developing to the blastocyst, there was no effect of CSF2 on labeling for H3K27me3 or H3K18ac. Results indicate that the blastocyst trophoctoderm can be modified epigenetically by embryo sex and paternal inheritance through alterations in histone epigenetic marks.

Effect of sex differences in donor foetal fibroblast on the early development and DNA methylation status of buffalo (Bubalus bubalis) nuclear transfer embryos

Low efficiency of somatic cell nuclear transfer (SCNT) embryos is largely attributable to imperfect reprogramming of the donor nucleus. The differences in epigenetic reprogramming between female and male buffalo cloned embryos remain unclear. We explored the effects of donor cell sex differences on the development of SCNT embryos. We and then compared the expression of DNA methylation (5-methylcytosine-5mC and 5-hydroxymethylcytosine-5hmC) and the expression level of relevant genes, and histone methylation (H3K9me2 and H3K9me3) level in SCNT-♀ and SCNT-♂ preimplantation embryos with in vitro fertilization (IVF) counterparts. In the study, we showed that developmental potential of SCNT-♀ embryos was greater than that of SCNT-♂ embryos (p < 0.05). 5mC was mainly expressed in SCNT-♀ embryos, whereas 5hmC was majorly expressed in SCNT-♂ embryos (p < 0.05). The levels of DNA methylation (5mC and 5hmC), Dnmt3b, TET1 and TET3 in the SCNT-♂ embryos were higher than those of SCNT-♀ embryos (p < 0.05). In addition, there were no significant differences in the expression of H3K9me2 at eight-stage of the IVF, SCNT-♀ and SCNT-♂embryos (p < 0.05). However, H3K9me3 was upregulated in SCNT-♂ embryos at the eight-cell stage (p < 0.05). Thus, KDM4B ectopic expression decreased the level of H3K9me3 and significantly improved the developmental rate of two-cell, eight-cell and blastocysts of SCNT-♂ embryos (p < 0.05). Overall, the lower levels of DNA methylation (5mC and 5hmC) and H3K9me3 may introduce the greater developmental potential in buffalo SCNT-♀ embryos than that of SCNT-♂ embryos.