Myostatin (MSTN), a member of the transforming growth factor-β superfamily, inhibits the activation of muscle satellite cells. However, the role and regulatory network of MSTN in equine muscle cells are not well understood yet. We discovered that MSTN knockdown significantly reduces the proliferation rate of equine muscle satellite cells. In addition, after the RNA sequencing of equine satellite cells transfected with MSTN-interference plasmid and control plasmid, an analysis of the differentially expressed genes was carried out. It was revealed that MSTN regulatory networks mainly involve genes related to muscle function and cell-cycle regulation, and signaling pathways, such as Notch, MAPK, and WNT. Subsequent real-time PCR in equine satellite cells and immunohistochemistry on newborn and adult muscle also verified the MSTN regulatory network found in RNA sequencing analysis. The results of this study provide new insight into the regulatory mechanism of equine MSTN.

During equine early gestation, trophectoderm forms chorion tissue, which is composed of two parts that one is covering allantoin, called allantochorion (AC) and another is covering yolk sac, which here we call vitelline-chorion (VC). Given that little is known about the equine trophoblast-derived chorion differentiation at an early stage, we first compared the transcriptome of AC and VC of day 30 equine conceptus based on RNA-sequencing. As a result, we found that compared to VC, there are 484 DEGs, including 305 up- and 179 down-regulated genes in AC. GO and KEGG analysis indicated that up-regulated genes in AC are mainly cell proliferation and cell adhesion-related genes, participating in allantois expansion and allantochorionic-placenta formation; dominant genes in VC are extracellular exosome and other cell adhesion-related genes implicated in direct and indirect conceptus-maternal communication. Additionally, as for the progenitor chorion tissue of equine chorionic gonadotropin secreting endometrium cup—the chorionic girdle (CG), which locates at the junction of the dilating AC and regressing VC, we revealed its unique gene expression pattern and the gene regulation during its further differentiation in vitro. Collectively, this study sheds light on the molecular events regarding the trophoblast differentiation and function at an early stage of the equine preimplantation conceptus.

Background: Typically, 60% of oocytes recovered from equine follicles are with expanded cumuli, 30% are with compact cumuli, and 10% are degenerated. Studies have proved that equine oocytes with expanded cumuli (Ex COCs) and oocytes with compact cumuli (Cp COCs) are of different developmental competence and therefore, need different maturation time in vitro. To better understand the gap in developmental competence, we compared the expression of some growth factors and hormone-related genes in Ex COCs and Cp COCs. Methods: We tested the expression of some hormones and growth factors in Ex- and Cp-COCs by qPCR and immunofluorescence, and the influence of the growth factors and hormones on equine IVM. Results: As a result, we found that the expression patterns of FSHR, LHR,IGF1R, IGF2R, ESR1, ESR2, BMPR1, BMPR2, and ALK5 are different in two types of COCs and among BMP15, GDF9, Estrogen, and IGF2, the addition of Estrogen and IGF2 are beneficial to equine IVM. Conclusions: This study indicates that the differential expression pattern of growth factors and hormone-related genes might be responsible for the difference in developmental capacity of two types of COCs. This work provides clues for improving the equine IVM system.

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