Expression Of Pig Oocytes In Vitro Maturation Of Cumulus Role Of Bmps

Oocyte is a special group of germ cells in female ovaries. It is the biggest cell in the body and after fertilization it produced the embryo and forms the new life of individuals. Before fertilization, the oocytes must undergo a complex developmental process to achieve maturation. A lot of follicular compartment cells, include cumulus cells, theca cells, granulosa cells cooperate with each other to facilitate the maturation of oocytes. A lot of genes, hormones and chemicals also involved in the somatic and germ cells interactions during the oocyte development. Characterization of the follicular compartment somatic cells and the functional studies of these important oocyte related factors may contribute a lot to the understanding of the mechanism of oocyte maturation and facilitate the utilization of oocyte for the subsequent manipulation for animal biotechnology.Several layers of cumulus cells surround the oocyte in the antral follicle and play an important support and regulation role in oocytes development and maturation via the intercellular communications and interactions between oocytes and cumulus cells. After several groups of cultivation, we found great differences in the rates ofmaturation, cleavage and blastocysts between the cumulus-oocyte complexes (COCs)and naked oocytes (NOs) Using differential display reverse transcriptase polymerasechain reaction (DD-RT-PCR) analysis of differential mRNA expression and semi-quantitative reverse transcriptase-polymerase chain reaction, we compared mRNA expression in porcine oocytes from two sources: COCs and NOs. Fourteen differentially expressed cDNAs were cloned, sequenced, and their expression patterns were verified by semi-quantitative RT-PCR. Four cDNAs, including three genes (PELP1, Myo5b and CAST) and a new EST were confirmed preferentially expressed in the oocytes of COCs than NOs. The studies of three differentially expressed genes suggested that they mainly involved in estrogen receptor regulation, membrane trafficking, organelle transport, cellular signaling and a variety of other cellular processes. These results suggest that the aberrant transcription patterns detected in the oocytes of NOs compared with COCs may explain their reduced qualities in term of development and maturation. In conclusion, these differentially transcripted cDNAs may involved in the cellular interactions between oocytes and cumulus cells and thus to be considered as essential genes for the competence of oocytes.In vitro oocyte growth is the essential technology which enables the growing oocytes at various stages to achieve maturation and acquire the competence for the followed manipulation. An increased body of evidence indicates the members of transforming growth factorβsuperfamily are expressed in a variety of cell types within the ovary in a developmental-stage related manner and function as crucial factors in oocyte growth and follicular development. However, the expression of TGF-βfamily members have been studied extensively in the follicular compartment cells in the ovaries while poorly explored in the cumulus-oocytes-complexes (COCs) in culture systems. Using semi-quantitative RT-PCR we have investigated the temporal and spatial expression patterns of several bone morphogenetic proteins (BMP-4, BMP-6, BMP-15 and GDF-9), as well as BMP receptors (BMPRIA, BMPRIB, BMPRII and ActRII) in porcine COCs throughout in vitro maturation (IVM). In oocytes, the transcription of BMP-6, BMP-15, GDF-9 and BMPRII were down-regulated while BMP-4, BMPRIA and BMPRIB remained unchanged during the IVM. In cumulus cells, BMP-4 mRNA expression increased significantly, while BMP-6 and ActRII was down-regulated during the IVM. Nevertheless, the mRNAs of BMPRIA, BMPRIB and BMPRII were constantly expressed in cumulus cells in the process. However, the BMP-15 was absent in cumulus cells and ActRII was not detected in oocytes. In addition, we hardly found any transcription of BMP-2, BMP-5, BMP-7, ActRIA in porcine COCs throughout IVM. These data demonstrate a complex of BMP signaling system member gene expression within porcine COCs during IVM and facilitate the further functional characterization of these factors during oocyte maturation.