Location: Livestock and Range Research LaboratoryTitle: Differential transcript profiles in cumulus-oocyte complexes originating from pre-ovulatory follicles of varied physiological maturity in beef cows
|MOOREY, SARAH - University Of Tennessee|
|MONNIG, JENNA - University Of Missouri|
|SMITH, MICHAEL - University Of Missouri|
|ORTEGA, M. SOFIA - University Of Missouri|
|GREEN, JONATHON - University Of Missouri|
|POHLER, KY - Texas A&M University|
|BRIDGES, G. ALAN - University Of Minnesota|
|BEHURA, SUSANTA - University Of Missouri|
Submitted to: Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2021
Publication Date: 6/10/2021
Citation: Moorey, S.E., Monnig, J.M., Smith, M.F., Ortega, M., Green, J.A., Pohler, K.G., Bridges, G., Behura, S.K., Geary, T.W. 2021. Differential transcript profiles in cumulus-oocyte complexes originating from pre-ovulatory follicles of varied physiological maturity in beef cows. Genes. 12(6):893. https://doi.org/10.3390/genes12060893.
Interpretive Summary: Current protocols are very good at synchronizing estrus and ovulation in cattle. This practice allows the use of semen from more valuable bulls to improve genetics among calves. Using this semen to breed cows is referred to as artificial insemination (AI). Pregnancy rates to timed AI are similar to those obtained by AI after detecting estrus. About 30% of cows develop and release an immature egg and have lower fertility. The reasons for reduced fertility have been the focus of our research. The immature egg is less able to provide the energy needed for early embryo development. The causes of reduced fertility among these cows are described in this paper.
Technical Abstract: Small dominant follicle diameter at induced ovulation, but not at spontaneous ovulation, decreased pregnancy rate, fertilization rate, and day 7 embryo quality in beef cows. We hypothesized that the physiological status of the follicle at GnRH-induced ovulation has a direct effect on the transcriptome of the cumulus-oocyte complex, thereby affecting oocyte competence and subsequent embryo development. The objective of this study was to determine if the transcriptome of oocytes and associated cumulus cells (CC) differed among small (=11.7mm) and large follicles (=12.7 mm) exposed to a GnRH-induced gonadotropin surge and follicles (11.7-14.0 mm) exposed to an endogenous gonadotropin surge (spontaneous follicles). RNA-sequencing data, from pools of 4 oocytes or their corresponding CC, revealed 69, 94, and 83 differentially expressed gene transcripts (DEG) among oocyte pools from small versus large, small versus spontaneous, and large versus spontaneous follicle classifications, respectively. An additional 128, 98, and 80 DEG were identified among small versus large, small versus spontaneous, and large versus spontaneous follicle CC pools, respectively. The biological pathway “oxidative phosphorylation” was significantly enriched with DEG from small versus spontaneous follicle oocyte pools (FDR<0.01); whereas the glycolytic pathway was significantly enriched with DEG from CC pools obtained from large versus small follicles (FDR<0.01). These findings collectively suggest that altered carbohydrate metabolism within the cumulus-oocyte complex likely contributes to the decreased competency of oocytes from small pre-ovulatory follicles exposed to an exogenous GnRH-induced gonadotropin surge.