Suppression of keratin 18 gene expression in bovine blastocysts by RNA interference

RNA sequencing and gene co-expression network of in vitro matured oocytes and blastocysts of buffalo

In reproductive technologies, uncovering the molecular aspects of oocyte and embryo competence under different conditions is crucial for refining protocols and enhancing efficiency. RNA-seq generates high-throughput data and provides transcriptomes that can undergo additional computational analyses. This study presented the transcriptomic profiles of in vitro matured oocytes and blastocysts produced in vitro from buffalo crossbred (Bubalus bubalis), coupled with gene co-expression and module preservation analysis. Cumulus Oophorus Complexes, obtained from slaughterhouse-derived ovaries, were subjected to in vitro maturation to yield metaphase II oocytes (616) or followed in vitro fertilization and culture to yield blastocysts for sequencing (526). Oocyte maturation (72%, ±3.34 sd) and embryo development (21.3%, ±4.18 sd) rates were obtained from three in vitro embryo production routines following standard protocols. Sequencing of 410 metaphase II oocytes and 70 hatched blastocysts (grade 1 and 2) identified a total of 13,976 genes, with 62% being ubiquitously expressed (8,649). Among them, the differentially expressed genes (4,153) and the strongly variable genes with the higher expression (fold-change above 11) were highlighted in oocytes (BMP15, UCHL1, WEE1, NLRPs, KPNA7, ZP2, and ZP4) and blastocysts (APOA1, KRT18, ANXA2, S100A14, SLC34A2, PRSS8 and ANXA2) as representative indicators of molecular quality. Additionally, genes exclusively found in oocytes (224) and blastocysts (2,200) with specific biological functions were identified. Gene co-expression network and module preservation analysis revealed strong preservation of functional modules related to exosome components, steroid metabolism, cell proliferation, and morphogenesis. However, cell cycle and amino acid transport modules exhibited weak preservation, which may reflect differences in embryo development kinetics and the activation of cell signaling pathways between buffalo and bovine. This comprehensive transcriptomic profile serves as a valuable resource for assessing the molecular quality of buffalo oocytes and embryos in future in vitro embryo production assays.

How great thou ART: biomechanical properties of oocytes and embryos as indicators of quality in assisted reproductive technologies

Assisted Reproductive Technologies (ART) have revolutionized infertility treatment and animal breeding, but their success largely depends on selecting high-quality oocytes for fertilization and embryos for transfer. During preimplantation development, embryos undergo complex morphogenetic processes, such as compaction and cavitation, driven by cellular forces dependent on cytoskeletal dynamics and cell-cell interactions. These processes are pivotal in dictating an embryo's capacity to implant and progress to full-term development. Hence, a comprehensive grasp of the biomechanical attributes characterizing healthy oocytes and embryos is essential for selecting those with higher developmental potential. Various noninvasive techniques have emerged as valuable tools for assessing biomechanical properties without disturbing the oocyte or embryo physiological state, including morphokinetics, analysis of cytoplasmic movement velocity, or quantification of cortical tension and elasticity using microaspiration. By shedding light on the cytoskeletal processes involved in chromosome segregation, cytokinesis, cellular trafficking, and cell adhesion, underlying oogenesis, and embryonic development, this review explores the significance of embryo biomechanics in ART and its potential implications for improving clinical IVF outcomes, offering valuable insights and research directions to enhance oocyte and embryo selection procedures.

Proteomics approach reveals urinary markers for early pregnancy diagnosis in buffaloes

This study aimed to compare urine proteomics from non- and pregnant buffaloes in order to identify potential biomarkers of early pregnancy. Forty-four females underwent hormonal ovulation synchronization and were randomly divided into two experimental groups: inseminated (n = 30) and non-inseminated (n = 14). The pregnant females were further divided into two groups: pregnant at Day 12 (P12; n = 8) and at Day 18 (P18; n = 8) post-ovulation. The non-pregnant group was also subdivided into two groups: non-pregnant at Day 12 (NP12; n = 7) and at Day 18 (NP18; n = 7). Urine was collected from all females on Days 12 or 18. The samples were processed for proteomics. A total of 798 proteins were reported in the urine considering all groups. The differential proteins play essential roles during pregnancy, acting in cellular transport and metabolism, endometrial remodeling, embryonic protection, and degradation of defective proteins. We suggest that some proteins from our study can be considered biomarkers for early pregnancy diagnosis, since they were increased in pregnant buffaloes. SIGNIFICANCE: Macromolecules have been studied for early pregnancy diagnosis, aiming to increase reproductive efficiency in cattle and buffaloes. Direct methods such as rectal palpation and ultrasonography have been considered late. Thus, this study aimed to compare urine proteomics from non- and pregnant buffaloes to identify potential biomarkers of early pregnancy. The differential proteins found in our study play essential roles during pregnancy, acting in cellular transport and metabolism, endometrial remodeling, embryonic protection, and degradation of defective proteins. We suggest that these proteins can be considered possible biomarkers for early pregnancy diagnosis since they were increased in the pregnant buffaloes.

miR-1246 is implicated as a possible candidate for endometrium remodelling facilitating implantation in buffalo (Bubalus bubalis)

BACKGROUND

The microRNAs (miRs) secreted by the trophectoderm (TE) cells have recently been implicated in the conceptus-endometrial cross talk during implantation and placentation. These miRs modulate various cellular processes during conception and throughout the pregnancy by regulating the gene expression in the foetal and maternal tissues.

OBJECTIVES

This study was undertaken to elucidate the function of TE secreted miRNAs in the maternal-foetal cross-talk during implantation/placentation in buffalo.

METHODS

The in vitro produced blastocysts were cultured on a cumulus feeder layer for 21 days. The relative expression profiles of a selected panel of miRs was generated using the spent media collected on Days 0, 7, 12, 16, and 21. A custom-designed mirVana™ miRNA mimic was used to transfect the endometrial epithelial cells (EECs) in order to determine the role of miRNA exhibiting highest expression on Days 21 and 21.

RESULTS

The expression of miR-1246 (p < 0.001) and let-7b (p < 0.01) was found to be significantly higher on Day 21 of TE culture in comparison to the control (Day 0). This elevated expression indicated the involvement of these miRs in the maternal-foetal cross-talk. Interestingly, after the transfection of EECs with miRNA mimic for miR-1246 (a novel molecule vis-à-vis implantation), the expression of beta-catenin and mucin1 in these cells was found to be significantly (p < 0.05) downregulated vis-à-vis the control, that is, the IFN-τ primed EECs (before transfection).

CONCLUSIONS

The TE secreted miR-1246 appeared to lower the expression of the endometrial receptivity genes (mucin1 and beta-catenin) which apparently assists the endometrium in preparing for placentation.

Dynamic Changes in the Proteome of Early Bovine Embryos Developed In Vivo

Early embryo development is a dynamic process involving important molecular and structural changes leading to the embryonic genome activation (EGA) and early cell lineage differentiation. Our aim was to elucidate proteomic changes in bovine embryos developed in vivo. Eleven females were used as embryo donors and pools of embryos at the 4–6 cell, 8–12 cell, morula, compact morula and blastocyst stages were analyzed by nanoliquid chromatography coupled with label free quantitative mass spectrometry. A total of 2,757 proteins were identified, of which 1,950 were quantitatively analyzed. Principal component analysis of data showed a clear separation of embryo pools according to their developmental stage. The hierarchical clustering of differentially abundant proteins evidenced a first cluster of 626 proteins that increased in abundance during development and a second cluster of 400 proteins that decreased in abundance during development, with most significant changes at the time of EGA and blastocyst formation. The main pathways and processes overrepresented among upregulated proteins were RNA metabolism, protein translation and ribosome biogenesis, whereas Golgi vesicle transport and protein processing in endoplasmic reticulum were overrepresented among downregulated proteins. The pairwise comparison between stages allowed us to identify specific protein interaction networks and metabolic pathways at the time of EGA, morula compaction and blastocyst formation. This is the first comprehensive study of proteome dynamics in non-rodent mammalian embryos developed in vivo. These data provide a number of protein candidates that will be useful for further mechanistic and functional studies.

Proteomic profile of pre-implantational ovine embryos produced in vivo

The present study was conducted to decipher the proteome of in vivo-produced pre-implantation ovine embryos. Ten locally adapted Morana Nova ewes received hormonal treatment and were inseminated 12 hr after ovulation. Six days later, 54 embryos (morula and blastocyst developmental state) were recovered from eight ewes and pooled to obtain sufficient protein for proteomic analysis. Extracted embryo proteins were analysed by LC-MS/MS, followed by identification based on four database searches (PEAKS, Proteome Discoverer software, SearchGUI software, PepExplorer). Identified proteins were analysed for gene ontology terms, protein clusters and interactions. Genes associated with the ovine embryo proteome were screened for miRNA targets using data sets of TargetScan (http://www.targetscan.org) and mIRBase (http://www.mirbase.org) servers. There were 667 proteins identified in the ovine embryos. Biological processes of such proteins were mainly related to cellular process and regulation, and molecular functions, to binding and catalytic activity. Analysis of the embryo proteins revealed 49 enriched functional clusters, linked to energy metabolism (TCA cycle, pyruvate and glycolysis metabolism), zona pellucida (ZP), MAPK signalling pathway, tight junction, binding of sperm to ZP, translation, proteasome, cell cycle and calcium/phospholipid binding. Sixteen miRNAs were related to 25 pre-implantation ovine embryo genes, all conserved in human, bovine and ovine species. The interaction network generated by miRNet showed four key miRNAs (hsa-mir-106b-5p; hsa-mir-30-5p; hsa-mir-103a-5p and hsa-mir-106a-5p) with potential interactions with embryo-expressed genes. Functional analysis of the network indicated that miRNAs modulate genes related to cell cycle, regulation of stem cell and embryonic cell differentiation, among others. Retrieved miRNAs also modulate the expression of genes involved in cell signalling pathways, such as MAPK, Wnt, TGF-beta, p53 and Toll-like receptor. The current study describes the first major proteomic profile of 6-day-old ovine embryos produced in vivo, setting a comprehensive foundation for our understanding of embryo physiology in the ovine species.

Maternal Yes-Associated Protein Participates in Porcine Blastocyst Development via Modulation of Trophectoderm Epithelium Barrier Function

The establishment of a functional trophectoderm (TE) epithelium is an essential prerequisite for blastocyst formation and placentation. Transcription coactivator yes-associated protein (YAP), a downstream effector of the hippo signaling pathway, is required for specification of both the TE and epiblast lineages in mice. However, the biological role of YAP in porcine blastocyst development is not known. Here, we report that maternally derived YAP protein is localized to both the cytoplasm and nuclei prior to the morula stage and is then predominantly localized to the TE nuclei in blastocysts. Functionally, maternal YAP knockdown severely impeded blastocyst formation and perturbed the allocation of the first two lineages. The treatment of embryos with verteporfin, a pharmacological inhibitor of YAP, faithfully recapitulated the phenotype observed in YAP deleted embryos. Mechanistically, we found that maternal YAP regulates multiple genes which are important for lineage commitment, tight junction assembly, and fluid accumulation. Consistent with the effects on tight junction gene expression, a permeability assay revealed that paracellular sealing was defective in the trophectoderm epithelium. Lastly, YAP knockdown in a single blastomere at the 2-cell stage revealed that the cellular progeny of the YAP⁺ blastomere were sufficient to sustain blastocyst formation via direct complementation of the defective trophectoderm epithelium. In summary, these findings demonstrate that maternal YAP facilitates porcine blastocyst development through transcriptional regulation of key genes that are essential for lineage commitment, tight junction assembly, and fluid accumulation.

Bta-miR-10b Secreted by Bovine Embryos Negatively Impacts Preimplantation Embryo Quality

In a previous study, we found miR-10b to be more abundant in a conditioned culture medium of degenerate embryos compared to that of blastocysts. Here, we show that miR-10b mimics added to the culture medium can be taken up by embryos. This uptake results in an increase in embryonic cell apoptosis and aberrant expression of DNA methyltransferases (DNMTs). Using several algorithms, Homeobox A1 (HOXA1) was identified as one of the potential miR-10b target genes and dual-luciferase assay confirmed HOXA1 as a direct target of miR-10b. Microinjection of si-HOXA1 into embryos also resulted in an increase in embryonic cell apoptosis and downregulation of DNMTs. Cell progression analysis using Madin–Darby bovine kidney cells (MDBKs) showed that miR-10b overexpression and HOXA1 knockdown results in suppressed cell cycle progression and decreased cell viability. Overall, this work demonstrates that miR-10b negatively influences embryo quality and might do this through targeting HOXA1 and/or influencing DNA methylation.

Transcription factor AP-2γ is a core regulator of tight junction biogenesis and cavity formation during mouse early embryogenesis

The trophectoderm epithelium is the first differentiated cell layer to arise during mammalian development. Blastocyst formation requires the proper expression and localization of tight junction, polarity, ion gradient and H2O channel proteins in the outer cell membranes. However, the underlying transcriptional mechanisms that control their expression are largely unknown. Here, we report that transcription factor AP-2γ (Tcfap2c) is a core regulator of blastocyst formation in mice. Bioinformatics, chromatin immunoprecipitation and transcriptional analysis revealed that Tcfap2c binds and regulates a diverse group of genes expressed during blastocyst formation. RNA interference experiments demonstrated that Tcfap2c regulates genes important for tight junctions, cell polarity and fluid accumulation. Functional and ultrastructural studies revealed that Tcfap2c is necessary for tight junction assembly and paracellular sealing in trophectoderm epithelium. Aggregation of control eight-cell embryos with Tcfap2c knockdown embryos rescued blastocyst formation via direct contribution to the trophectoderm epithelium. Finally, we found that Tcfap2c promotes cellular proliferation via direct repression of p21 transcription during the morula-to-blastocyst transition. We propose a model in which Tcfap2c acts in a hierarchy to facilitate blastocyst formation through transcriptional regulation of core genes involved in tight junction assembly, fluid accumulation and cellular proliferation.

The Efficient Derivation of Trophoblast Cells from Porcine In Vitro Fertilized and Parthenogenetic Blastocysts and Culture with ROCK Inhibitor Y-27632

Trophoblasts (TR) are specialized cells of the placenta and play an important role in embryo implantation. The in vitro culture of trophoblasts provided an important tool to investigate the mechanisms of implantation. In the present study, porcine trophoblast cells were derived from pig in vitro fertilized (IVF) and parthenogenetically activated (PA) blastocysts via culturing in medium supplemented with KnockOut serum replacement (KOSR) and basic fibroblast growth factor (bFGF) on STO feeder layers, and the effect of ROCK (Rho-associated coiled-coil protein kinases) inhibiter Y-27632 on the cell lines culture was tested. 5 PA blastocyst derived cell lines and 2 IVF blastocyst derived cell lines have been cultured more than 20 passages; one PA cell lines reached 110 passages without obvious morphological alteration. The derived trophoblast cells exhibited epithelium-like morphology, rich in lipid droplets, and had obvious defined boundaries with the feeder cells. The cells were histochemically stained positive for alkaline phosphatase. The expression of TR lineage markers, such as CDX2, KRT7, KRT18, TEAD4, ELF5 and HAND1, imprinted genes such as IGF2, PEG1 and PEG10, and telomerase activity related genes TERC and TERF2 were detected by immunofluorescence staining, reverse transcription PCR and quantitative real-time PCR analyses. Both PA and IVF blastocysts derived trophoblast cells possessed the ability to differentiate into mature trophoblast cells in vitro. The addition of Y-27632 improved the growth of both PA and IVF blastocyst derived cell lines and increased the expression of trophoblast genes. This study has provided an alternative highly efficient method to establish trophoblast for research focused on peri-implantation and placenta development in IVF and PA embryos.

Gene silencing in bovine zygotes: siRNA transfection versus microinjection

The aim of this study was to compare gene silencing in bovine zygotes when small interfering RNAs (siRNAs) were introduced into bovine zygotes by microinjection or lipid-based transfection. In Experiment 1, E-cadherin siRNA was injected at 100 or 375 µM and compared with PBS-injected and non-injected controls. Embryos were then cultured in vitro for 7 days and periodically assessed for development. For transfection, zona-free zygotes were incubated in transfection medium with siRNA for 1 h at 39°C and then cultured to Day 7. Injection of PBS or 375 µM E-cadherin siRNA resulted in a decrease in the number of embryos reaching the 8-cell stage (51.5% and 45.5%) or the blastocyst stage (39.0 and 32.5%) compared with non-injected controls (62.9 and 45.0%, respectively; P < 0.05). Messenger RNA abundance was suppressed by 36 and 46% when siRNA targeting E-cadherin was injected at 100 and 375 µM, respectively, compared with controls (P < 0.05). Transfection with 100 nM E-cadherin siRNA decreased development to the 8-cell stage (20.3 versus 53.0%) and blastocyst stage (7.2 versus 18.2%) compared with controls (P < 0.05). Messenger RNA relative abundance was not different between controls (non-transfected or transfected with GAPDH or scrambled siRNA). However, transfection of zygotes with 100 and 200 nM E-cadherin siRNA led to a 72 and 38% reduction, respectively, in E-cadherin mRNA relative abundance in Day 7 blastocysts compared with controls (P < 0.05).