Ganglioside GM3 is known as an inhibition factor of cell differentiation and proliferation via inhibition of epidermal growth factor receptor (EGFR) phosphorylation. Our previous study showed that the exogenous ganglioside GM3 reduced the meiotic maturation of porcine oocytes and induced apoptosis at 44 h of in vitro maturation (IVM). However, the role of ganglioside GM3 in the relationship between EGFR signaling and apoptosis during porcine oocyte maturation has not yet been studied. First, porcine cumulus-oocyte complexes (COCs) were cultured in the NCSU-23 medium with exogenous ganglioside GM3 according to maturation periods (non-treated, only IVM I: 0 - 22 h, only IVM II: 22 - 44 h and IVM I & II: 0 - 44 h). We confirmed that the proportion of germinal vesicle breakdown (GVBD) increased significantly in the IVM I treated group than in the control group. We also confirmed that the meiotic maturation until M II stage and polar body formation decreased significantly in the only IVM I treated group. Cumulus cell expansion and mRNA levels of the expansion-related factors (HAS2, TNFAIP6 and PTX3) decreased significantly in the IVM I treated group than in the control group. Protein levels of EGFR, p-EGFR, ERK1/2, and p-ERK1/2 decreased significantly in the GM3-treated groups, during the IVM I period. In addition, cellular apoptosis, determined using TUNEL assay, and protein levels of Cleaved caspase 3, were increased significantly in the GM3-treated COCs during the IVM I period. Based on these results, ganglioside GM3 exposure of porcine COCs during the IVM I period reduced meiotic maturation and cumulus cell expansion via inhibition of EGFR activity in pigs.

Abstract
 INTRODUCTION
 MATERIALS AND METHODS
  Chemicals
  In vitro maturation (IVM)
  Assessment of meiotic maturation and polar body extrusion
  Assessment of cumulus cells expansion
  RT-PCR
  Western blot analysis
  Statistical analysis
 RESULTS
  Changes in meiotic maturation and cumulus cells expansionin porcine COCs according to GM3 (10 μM) treatment timeduring IVM peri
  Protein levels of ST3GAL5 and EGFR-ERK1/2 signaling inporcine COCs according to GM3 treatment time
  Changes of cellular apoptosis in porcine COCs accordingto GM3 treatment timing
 DISCUSSION
 REFERENCES

• Jin-Woo Kim(Department of Biotechnology, College of Engineering, Daegu University)
• Hyo-Jin Park(Department of Biotechnology, College of Engineering, Daegu University)
• Jae-Min Jung(Department of Biotechnology, College of Engineering, Daegu University)
• Seul-Gi Yang(Department of Biotechnology, College of Engineering, Daegu University)
• Min-Ji Kim(Department of Biotechnology, College of Engineering, Daegu University)
• In-Su Kim(Department of Biotechnology, College of Engineering, Daegu University)
• Ho-Geun Jegal(Department of Biotechnology, College of Engineering, Daegu University)
• Deog-Bon Koo(Department of Biotechnology, College of Engineering, Daegu University) Correspondence