Study on the expression patterns and function of JUNO and CD9 in bovine oocytes during in vitro maturation

Fertilization proteins JUNO and CD9 play vital roles in sperm-egg fusion, but little is known about their expression patterns during in vitro maturation (IVM) and their function during in vitro fertilization (IVF) of bovine oocytes. In this study, qRT-PCR and immunofluorescence staining were used to detect the mRNA and protein expression levels of JUNO and CD9 genes in bovine oocytes and cumulus cells. Then, fertilization rate of MII oocytes treated with (i) JUNO antibody (1, 5 and 25 mu g/ml) or (ii) CD9 antibody (1, 5 and 25 mu g/ml) or (iii) CD9 antibody (5 mu g/ml) + JUNO antibody (5 mu g/ml) were recorded. Our results showed that the mRNA and protein expression levels of JUNO and CD9 genes significantly increased from bovine GV oocytes to MII oocytes, and similar mRNA expression patterns of JUNO and CD9 were also detected in cumulus cells. All groups of oocytes treated with CD9 antibody or JUNO antibody showed significantly decreased fertilization rates (p < .05). Particularly, the fertilization ability of oocytes treated with CD9 antibody (5 mu g/ml) + JUNO antibody (5 mu g/ml) sharply decreased to 3.48 +/- 0.11%. In conclusion, our study revealed the expression levels of JUNO and CD9 genes in oocytes and cumulus cells increased during IVM of bovine oocytes, with JUNO protein playing a major role in the fertilization of bovine oocytes.

Automated summary

A study investigated the expression patterns and functions of fertilization proteins JUNO and CD9 in bovine oocytes during in vitro maturation (IVM) and in vitro fertilization (IVF). The results showed that the mRNA and protein expression levels of JUNO and CD9 genes increased from bovine GV oocytes to MII oocytes, and similar expression patterns were observed in cumulus cells. Treatment with antibodies against JUNO or CD9 significantly reduced the fertilization rates of oocytes, with JUNO antibody showing a major impact on the fertilization ability of bovine oocytes.