Ernst EH, et al. – The purpose of this study is to determine whether specific transcriptome dynamics in human oocytes from primordial and primary follicles recognize novel pathways in oocyte activation. The transcriptomic profiles in oocytes from primordial and primary follicles, respectively, uncovered several new canonical pathways as putative mediators of oocyte dormancy and activation.

Methods

• For this research, they performed a class comparison study on human oocytes from primordial (n= 436) and primary (n = 182) follicles donated by three women having ovarian tissue cryopreserved before chemotherapy.
• RNA was extracted from oocytes from primordial and primary follicles isolated by Laser Capture Microdissection and submitted to the HiSeq Illumina platform.
• Information mapping, quality control, filtering and expression investigation were performed utilizing Tophat (2.0.4), Cufflinks (2.0.2), BWA (0.6.2) and software R.
• Modeling of complex biological systems was performed utilizing the IPA® software.
• Finally, qPCR and immunohistochemistry were employed to investigate expression and localization of selected genes and products in human ovarian tissue.

Results

• In this research, they found 223 and 268 genes down–regulated and up–regulated, respectively, in the oocytes amid the human primordial–to–primary follicle transition (P< 0.05 and/or FPKM fold–change >2).
• IPA® enrichment investigation uncovered known pathways (‘mTOR Signaling’, ‘PI3K/AKT Signaling’ and ‘PTEN Signaling’) and also enriched canonical pathways not previously connected with human ovarian follicle development such as ‘ErB Signaling’ and ‘NGF Signaling’ in the down–regulated category and ‘Regulation of eIF4 and P70S6K Signaling’ and ‘HER–2 Signaling in Breast Cancer’ in the up–regulated group.
• Additionally, immunohistochemistry on human ovarian tissue investigated the intraovarian localization of VASA, FOXO1 and eIF4E.