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Comment |
Changes in granulosa cells gene expression associated with increased oocyte competence in bovine. Nivet AL et al. One of the challenges in mammalian reproduction is to understand basic physiology of oocyte quality. It is believed that the follicle status is linked to developmental competence of the enclosed oocyte. To explore the link between follicles and competence in cows, a previous experiment from our laboratory has developed an ovarian stimulation protocol that increases and then decreases oocyte quality according to the timing of oocyte recovery post FSH withdrawal (coasting). Using such protocol, we have obtained the granulosa cells associated with oocytes of different qualities at selected times of coasting. Transcriptome analysis was done with Embryogene microarray slides and validation by real-time PCR. Results shows that the major changes in gene expression occurred from 20h to 44h of coasting, when oocyte quality rising. Secondly, among up-regulated genes (20h to 44h), 25%were extracellular molecules, highlighting potential granulosa signaling cascades. Principal component analysis identified 2 patterns: one resembling the competence profile and another associated with follicle growth and atresia. Additionally, 3 major functional changes were identified: 1) the end of follicle growth (BMPR1B, IGF2, RELN), involving interactions with the extracellular matrix (TFPI2); angiogenesis (NRP1), including early hypoxia, and potentially oxidative stress (GFPT2, TF, VNN1) and 2) apoptosis (KCNJ8) followed by 3) inflammation (ANKRD1). This unique window of analysis indicates a progressive hypoxia during coasting mixed with an increase of apoptosis and inflammation. Potential signaling pathways leading to competence have been identified and will require downstream testing. This preliminary analysis supports the potential role of the follicular differentiation in oocyte quality both during competence increase and decrease phases.
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