Genomic expression profiles in cumulus cells derived from germinal vesicle and MII mouse oocytes

Abstract

Cumulus cells (CCs) are distinct from other granulosa cells and the mutual communication between CCs and oocytes is essential for the establishment of oocyte competence. In the present study we assessed genomic expression profiles in mouse CCs before and after oocyte maturation in vitro. Microarray analysis revealed significant changes in gene expression in CCs between the germinal vesicle (GV) and metaphase II (MII) stages, with 2615 upregulated and 2808 downregulated genes. Genes related to epidermal growth factor, extracellular matrix (Ptgs2, Ereg, Tnfaip6 and Efemp1), mitochondrial metabolism (Fdx1 and Aifm2), gap junctions and the cell cycle (Gja1, Gja4, Ccnd2, Ccna2 and Ccnb2) were highlighted as being differentially expressed between the two development stages. Real-time polymerase chain reaction confirmed the validity and reproducibility of the results for the selected differentially expressed genes. Similar expression patterns were identified by western blot analysis for some functional proteins, including EFEMP1, FDX1, GJA1 and CCND2, followed by immunofluorescence localisation. These genes may be potential biomarkers for oocyte developmental competence following fertilisation and will be investigated further in future studies.

In vivo and in vitro maturation of rabbit oocytes differently affects the gene expression profile, mitochondrial distribution, apoptosis and early embryo development

“…Conversely, PTGS2 is the key enzyme in prostaglandin E biosynthesis and is also involved in regulation of CC expansion during the ovulatory process in mice (Davis et al 1999;Jang et al 2015). In the present study, Ptgs2 mRNA transcripts were upregulated in CCs after oocyte maturation, as described previously for cattle (Nuttinck et al 2002), mice (Shao et al 2015) and humans (Feuerstein et al 2007;Wathlet et al 2011). The abundance of PTGS2 in CCs is positively correlated with oocyte competence in other species, including cattle (Assidi et al 2008), pigs (Kang et al 2012) andhumans (McKenzie et al 2004).…”

“…The findings of the present study show that Gja1 expression was significantly lower CCs surrounding in vivo-matured MII oocytes than in CCs enclosing immature or IVM oocytes, supporting previous results obtained in the bovine (Calder et al 2003), canine (Cho et al 2016) and in humans (Li et al 2015). The reduced expression of GJA1 in CCs after oocyte maturation is beneficial (Edry et al 2006) because it is related to cumulus expansion and decreased diffusion of cAMP and cGMP from the CCs to the oocyte, which is followed by the end of meiotic arrest and extrusion of the first polar body (Shao et al 2015). Conversely, PTGS2 is the key enzyme in prostaglandin E biosynthesis and is also involved in regulation of CC expansion during the ovulatory process in mice (Davis et al 1999;Jang et al 2015).…”

“…Gja1 and Ptgs2 were quantified only in CCs because their expression is related to cell-cell communication and cumulus expansion. According to Feuerstein et al (2007) and Shao et al (2015), the quantification of such genes can be used as a method to evaluate the quality of granulosa cells and indirectly as a biomarker of oocyte quality. Primer sequences and the approximate size of the amplified fragments for all transcripts are given in Table 1.…”

“…Consequently, gene expression analysis in CCs provides a non-invasive method for identification of the most competent oocytes for assisted reproductive technologies (ARTs). In recent years, several studies in animal models (Nivet et al 2013;Blaha et al 2015;Shao et al 2015) and humans (McKenzie et al 2004;Adriaenssens et al 2010;Assou et al 2010;Li et al 2015) have tried to identify candidate genes expressed in CCs that could be used as biomarkers of oocyte quality. In this sense, some studies have focused on identifying differences in gene expression between IVM and in vivo-matured cumulus-oocyte complexes (COCs) in many species, including dogs (Cho et al 2016), cattle (Tesfaye et al 2009;Adona et al 2016), mice (Cecconi et al 2010) and humans (Jones et al 2008;Ouandaogo et al 2012).…”

“…Nuclear maturation can be easily assessed because it is characterised by meiotic resumption, accompanied by CC expansion, meiotic progression until MII and release of the first polar body. Thereby, gene expression profiles of genes related to cumulus expansion, such as gap junction protein, alpha 1, 43 kDa (Gja1) and prostaglandinendoperoxide synthase 2 (Ptgs2), have been proposed as suitable biomarkers for predicting pregnancy (Feuerstein et al 2007;Hasegawa et al 2007;Li et al 2015;Shao et al 2015). However, molecular events and reorganisation of organelles that occur during cytoplasmic maturation are difficult to evaluate and deserve further investigation.…”