Transcriptional profiling of cumulus cells from fli-matured oocytes identifies junctional genes as key components in oocyte maturation
No Thumbnail Available
Authors
Meeting name
Sponsors
Date
Journal Title
Format
Thesis
Subject
Abstract
[EMBARGOED UNTIL 08/01/2026] The production of genetically engineered pigs for biomedical and agricultural purposes requires performing in vitro oocyte maturation and embryo culture. Additionally, in vitro maturation can play a key role in the preservation of important genetic lines and expanding the population of genetically valuable pigs. However, oocytes and embryos are exposed to a suboptimal in vitro environment, which can compromise their viability. Recent improvements to in vitro maturation media, including the addition of FGF2, LIF, and IGF1 (FLI), have increased the frequency of oocytes that reached the metaphase II stage, doubled the number of oocytes that reached the blastocyst stage, and quadrupled the number of piglets born after embryo transfer. Despite these benefits, the underlying cellular mechanisms remain poorly understood. Given the essential role of cumulus cells (CC) in oocyte maturation, we investigated how FLI affects CC gene expression. Cumulus-oocyte complexes (COC) were matured for 24 h in either control or FLI-supplemented media. CC originating from a single oocyte that reached the blastocyst stage was analyzed by using RNA sequencing. A total of 1,533 transcripts were differentially expressed. Of these, 511 were upregulated and 1,022 were downregulated in the FLI CC (adj-p < 0.05). Gene ontology analysis revealed cellular response to leukemia inhibitory factor was significantly upregulated in FLI-treated CC. The gene ontology term enriched among the downregulated genes in FLI matured CC was extracellular matrix organization. Notably, the CC from FLI matured oocytes showed differential gene expression related to junctional communication. Tight junction protein 2 (TJP2), cadherin 8 (CDH8), gap junction protein α5 (GJA5) and were upregulated in CC from FLI matured oocytes, while cadherin 9 (CDH9) and cadherin 22 (CDH22) were higher in control CC. To further investigate the effects of FLI on tight, gap, and adherens genes, we expanded our list of genes of interest to include tight junction protein 1 (TJP1), gap junction protein α1 (GJA1), and gap junction protein α4 (GJA4). Immunofluorescence confirmed the significantly elevated expression of tight junction proteins (TJP1, TJP2) and GJA4 in FLI-treated COCs, whereas GJA1 and GJA5 were more abundant in controls. However, adherens junction proteins CDH8, CDH9, and CDH22 did not differ significantly between groups. To evaluate cytoplasmic maturation, we assessed mitochondrial distribution, protein synthesis, and cortical granule localization. No significant differences were observed in mitochondrial intensity or protein synthesis between groups. However, cortical granule localization indicated a higher rate of exocytosis in FLI-treated COCs, potentially suggesting more advanced cytoplasmic maturation. These findings demonstrate that FLI supplementation modulates gene expression in CC, particularly those involved in cell-cell communication via junctional complexes. Furthermore, FLI may enhance cytoplasmic maturation as evidenced by cortical granule dynamics. These insights support the use of FLI to improve porcine IVM systems and provide a foundation for future research to increase oocyte developmental competence and embryo viability.
Table of Contents
PubMed ID
Degree
M.S.