Stage-Specific Profiling of Transforming Growth Factor-β, Fibroblast Growth Factor and Wingless-int Signaling Pathways during Early Embryo Development in The Goat

Dynamics of The Expression of Pluripotency and Lineage Specific Genes in The Pre and Peri-Implantation Goat Embryo

Objective

Two critical points of early development are the first and second lineage segregations, which are regulated by a wide spectrum of molecular and cellular factors. Gene regulatory networks, are one of the important components which handle inner cell mass (ICM) and trophectoderm (TE) fates and the pluripotency status across different mammalian species. Considering the importance of goats in agriculture and biotechnology, this study set out to investigate the dynamics of expression of the core pluripotency markers at the mRNA and protein levels.

Materials and Methods

In this experimental study, the expression pattern of three pluripotency markers (Oct4, Nanog and Sox2) and the linage specific markers (Rex1, Gata4 and Cdx2) were quantitatively assessed in in vitro matured (MII) oocytes and embryos at three distinctive stages: 8-16 cell stage, day-7 (D7) blastocysts and D14 blastocysts. Moreover, expression of Nanog, Oct4, Sox2 proteins, and their localization in the goat blastocyst was observed through immunocytochemistry.

Results

Relative levels of mRNA transcripts for Nanog and Sox2 in D3 (8-16 cell) embryos were significantly higher than D7 blastocysts and mature oocytes, while Oct4 was only significantly higher than D7 blastocysts. However, the expression pattern of Rex1, as an epiblast linage marker, decreased from the oocyte to the D14 stage. The expression pattern of Gata4 and Cdx2, as extra embryonic linage markers, also showed a similar trend from oocyte to D3 while their expressions were up-regulated in D14 blastocysts.

Conclusion

Reduction in Nanog, Oct4, Sox2 mRNA transcription and a late increase in extra embryonic linage markers suggests that the developmental program of linage differentiation is retarded in goat embryos compared to previously reported data on mice and humans. This is likely related to late the implantation in goats.

MiR-449a regulates caprine endometrial stromal cell apoptosis and endometrial receptivity

In this study, an RT-qPCR analysis showed that the expression levels of miR-449a in the pre-receptive endometrium were lower compared to the receptive endometrium, which is consistent with previous sequencing data (previous investigations). To detect the role of miR-449a in endometrial receptivity, we transfected caprine endometrial stromal cells (ESCs) cultured in vitro with miR-449a mimics. The results revealed that miR-449a decreased the mRNA and protein levels of LGR4 by targeting its 3′-untranslated region. The miR-449a mimics significantly reduced the G₁ cell population from 52.56% (mimic NC) to 42.19% with a concordant increase in the G₂ and S cell populations from 47.44% (mimic NC) to 57.81%, suggesting that miR-449a caused ESC cell cycle arrest. In addition, the number of apoptotic cells was significantly higher in ESCs transfected with miR-449a mimics (P < 0.05) than in ESCs transfected with mimic NC. In vivo, rich pinopodes were observed on the endometrial surface in the miR-449a agomir group compared with the miR-449a antagomir group. The results of hematoxylin-eosin staining showed that endometrial thickness was significantly increased in the miR-449a agomir group compared with the miR-449a antagomir group. These results suggest that miR-449a could enhance endometrial receptivity.