Histone Demethylase KDM4D Could Improve the Developmental Competence of Buffalo (Bubalus Bubalis) Somatic Cell Nuclear Transfer (SCNT) Embryos

Zinc improves the developmental ability of bovine in vitro fertilization embryos through its antioxidative action

Zinc, an essential trace mineral, exerts a pivotal influence in various biological processes. Through zinc concentration analysis, we found that the zinc concentration in the bovine embryo in vitro culture (IVC) medium was significantly lower than that in bovine follicular fluid. Therefore, this study explored the impact of zinc sulfate on IVC bovine embryo development and investigated the underlying mechanism. The results revealed a significant decline in zygote cleavage and blastocyst development rates when zinc deficiency was induced using zinc chelator N, N, N', N'-Tetrakis (2-pyridylmethyl) ethylenediamine (TPEN) in culture medium during embryo in vitro culture. The influence of zinc-deficiency was time-dependent. Conversely, supplementing 0.8 μg/mL zinc sulfate to culture medium (CM) increased the cleavage and blastocyst formation rate significantly. Moreover, this supplementation reduced reactive oxygen species (ROS) levels, elevated the glutathione (GSH) levels in blastocysts, upregulated the mRNA expression of antioxidase-related genes, and activated the Nrf2-Keap1-ARE signaling pathways. Furthermore, 0.8 μg/mL zinc sulfate enhanced mitochondrial membrane potential, maintained DNA stability, and enhanced the quality of bovine (in vitro fertilization) IVF blastocysts. In conclusion, the addition of 0.8 μg/mL zinc sulfate to CM could enhance the antioxidant capacity, activates the Nrf2-Keap1-ARE signaling pathways, augment mitochondrial membrane potential, and stabilizes DNA, ultimately improving blastocyst quality and in vitro bovine embryo development.

Overexpression of BRG1 improves early development of porcine somatic cell nuclear transfer embryos

The epigenetic modification levels of donor cells directly affect the developmental potential of somatic cell nuclear transfer (SCNT) embryos. BRG1, as an epigenetic modifying enzyme, has not yet been studied in donor cells and SCNT embryos. In this study, BRG1 was overexpressed in porcine fetal fibroblasts (PFFs), its effect on chromatin openness and gene transcription was examined, subsequently, the development potential of porcine SCNT embryos was investigated. The results showed that compared with the control group, the percentage of G1 phase cells was significantly increased (32.3 % ± 0.87 vs 25.7 % ± 0.81, P < 0.05) in the experimental group. The qRT-PCR results showed that the expression of H3K9me3-related genes was significantly decreased (P < 0.05), HAT1 was significantly increased (P < 0.05). Assay of Transposase Accessible Chromatin sequencing (ATAC-seq) results revealed that SMARCA4、NANOG、SOX2、MAP2K6 and HIF1A loci had more open chromatin peaks in the experimental group. The RNA-seq results showed that the upregulated genes were mainly enriched in PI3K/AKT and WNT signaling pathways, and the downregulated genes were largely focused on disease development. Interestingly, the developmental rate of porcine SCNT embryos was improved (27.33 % ± 1.40 vs 17.83 % ± 2.02, P < 0.05), the expression of zygotic gene activation-related genes in 4-cell embryos, and embryonic development-related genes in blastocysts was significantly upregulated in the experimental group (P < 0.05). These results suggest that overexpression of BRG1 in donor cells is benefit for the developmental potential of porcine SCNT embryos.

Comparison of Umbilical Cord Mesenchymal Stem Cells and Fibroblasts as Donor Nuclei for Handmade Cloning in Sheep Using a Single-Cell Transcriptome

Oocytes are efficient at reprogramming terminally differentiated cells to a totipotent state. Nuclear transfer techniques can exploit this property to produce cloned animals. However, the overall efficiency is low. The use of umbilical cord mesenchymal stem cells (UC-MSCs) as donor nuclei may increase blastocyst rates, but the exact reasons for this remain unexplored. A single-cell transcriptomic approach was used to map the transcriptome profiles of eight-cell embryos that were in vitro-fertilized and handmade-cloned using umbilical cord mesenchymal stem cells and fibroblasts as nuclear donors. Differences were examined at the chromatin level, the level of differentially expressed genes, the level of histone modifications and the level of DNA methylation. This research provides critical information regarding the use of UC-MSCs as a preferred donor nucleus for nuclear transfer techniques. It also offers unique insights into the mechanism of cellular reprogramming.

Vitamin C down-regulates the H3K9me3-dependent heterochromatin in buffalo fibroblasts via PI3K/PDK1/SGK1/KDM4A signal axis

The success of reprogramming is dependent on the reprogramming factors enriched in the cytoplasm of recipient oocytes and the potential of donor nucleus to be reprogrammed. Histone 3 lysine 9 trimethylation (H3K9me3) was identified as a major epigenetic barrier impeding complete reprogramming. Treating donor cell with vitamin C (Vc) can enhance the developmental potential of cloned embryos, but the underlying mechanisms still need to be elucidated. In this study, we found that 20μg/mL Vc could promote proliferation and inhibit apoptosis of BFFs, as well as down-regulate the H3K9me3-dependent heterochromatin and increase chromatin accessibility. Inhibited the expression of KDM4A resulted in increasing apoptosis rate and the H3K9me3-dependent heterochromatin, which can be restored by Vc. Moreover, Vc up-regulated the expression of KDM4A through PI3K/PDK1/SGK1 pathway. Inhibiting any factor in the signal axis of this PI3K pathway not only suppressed the activity of KDM4A but also substantially increased the level of H3K9me3 modification and the expression of the HP1α protein. Finally, Vc can rescue those negative effects induced by the blocking the PI3K/PDK1/SGK1 pathway. Collectively, Vc can down-regulate the H3K9me3-dependent heterochromatin in BFFs via PI3K/PDK1/SGK1/KDM4A signal axis, suggesting that Vc can turn the chromatin status of donor cells to be reprogrammed more easily.

Individual variation in buffalo somatic cell cloning efficiency is related to glycolytic metabolism

Mammalian individuals differ in their somatic cell cloning efficiency, but the mechanisms leading to this variation is poorly understood. Here we found that high cloning efficiency buffalo fetal fibroblasts (BFFs) displayed robust energy metabolism, looser chromatin structure, high H3K9 acetylation and low heterochromatin protein 1α (HP1α) expression. High cloning efficiency BFFs had more H3K9ac regions near to the upstream of glycolysis genes by ChIP-seq, and involved more openness loci related to glycolysis genes through ATAC-seq. The expression of these glycolysis genes was also found to be higher in high cloning efficiency BFFs by qRT-PCR. Two key enzymes of glycolysis, PDKs and LDH, were confirmed to be associated with histone acetylation and chromatin openness of BFFs. Treatment of low cloning efficiency BFFs with PS48 (activator of PDK1) resulted in an increase in the intracellular lactate production and H3K9 acetylation, decrease in histone deacetylase activity and HP1α expression, less condensed chromatin structure and more cloning embryos developing to blastocysts. These results indicate that the cloning efficiency of buffalo somatic cells is associated with their glycolytic metabolism and chromatin structure, and can be improved by increasing glycolytic metabolism.

ELF4 is critical to zygotic gene activation and epigenetic reprogramming during early embryonic development in pigs

Zygotic gene activation (ZGA) and epigenetic reprogramming are critical in early embryonic development in mammals, and transcription factors are involved in regulating these events. However, the effects of ELF4 on porcine embryonic development remain unclear. In this study, the expression of ELF4 was detected in early porcine embryos and different tissues. By knocking down ELF4, the changes of H3K9me3 modification, DNA methylation and ZGA-related genes were analyzed. Our results showed that ELF4 was expressed at all stages of early porcine embryos fertilized in vitro (IVF), with the highest expression level at the 8-cell stage. The embryonic developmental competency and blastocyst quality decreased after ELF4 knockdown (20.70% control vs. 17.49% si-scramble vs. 2.40% si-ELF4; p < 0.001). Knockdown of ELF4 induced DNA damage at the 4-cell stage. Interfering with ELF4 resulted in abnormal increases in H3K9me3 and DNA methylation levels at the 4-cell stage and inhibited the expression of genes related to ZGA. These results suggest that ELF4 affects ZGA and embryonic development competency in porcine embryos by maintaining genome integrity and regulating dynamic changes of H3K9me3 and DNA methylation, and correctly activating ZGA-related genes to promote epigenetic reprogramming. These results provide a theoretical basis for further studies on the regulatory mechanisms of ELF4 in porcine embryos.

Current Progress and Prospects in Rabbit Cloning

Somatic cell nuclear transfer (SCNT) shows great value in the generation of transgenic animals, protection of endangered animals, and stem cell therapy. The combination of SCNT and gene editing has produced a variety of genetically modified animals for life science and medical research. Rabbits have unique advantages as transgenic bioreactors and human disease models; however, the low SCNT efficiency severely impedes the application of this technology. The difficulty in SCNT may be attributable to the abnormal reprogramming of somatic cells in rabbits. This review focuses on the abnormal reprogramming of cloned mammalian embryos and evaluates the progress and prospects of rabbit somatic cell cloning.

Current status of assisted reproductive technologies in buffaloes

Buffaloes are raised by small farm holders primarily as source of draft power owing to its resistance to hot climate, disease, and stress conditions. Over the years, transformation of these animals from draft to dairy was deliberately carried out through genetic improvement program leading to the development of buffalo-based enterprises. Buffalo production is now getting more attention and interest from buffalo raisers due to its socioeconomic impact as well as its contribution to propelling the livestock industry in many developing countries. Reproduction of buffaloes, however, is confronted with huge challenge and concern as being generally less efficient to reproduce compared with cattle due to both intrinsic and extrinsic factors such as poor estrus manifestation, silent heat, marked seasonal infertility, postpartum anestrus, long calving interval, delayed puberty, inherently low number of primordial follicles in their ovaries, high incidence of atresia, and apoptosis. Assisted reproductive technologies (ARTs) are major interventions for the efficient utilization of follicle reserve in buffaloes. The present review focuses on estrus and ovulation synchronization for fixed time artificial insemination, in vitro embryo production, intracytoplasmic sperm injection, cryopreservation of oocytes and embryos, somatic cell nuclear transfer, the factors affecting utilization in various ARTs, and future perspectives in buffaloes.