iTRAQ-based proteomic profiling of granulosa cells from lamb and ewe after superstimulation

The number of oocytes obtained from lambs after FSH treatment is far greater than those acquired from adult ewes. However, these oocytes typically have reduced viability in comparison with adult ewe oocytes. However, the molecular mechanisms of differences in viability between lamb and ewe oocytes remain unknown. In the present research, we applied iTRAQ coupled with LC-MS/MS proteomic analysis in order to investigate the proteomic expression profile of granulosa cells from lambs and ewes following stimulation with FSH. We detected 5649 proteins; 574 were differentially expressed between adults and juveniles. Based on Gene Ontology enrichment and KEGG pathway analysis, the majority of DEPs are participated in metabolic processes, ribosome and MAPK signaling pathways. Expression levels in ewes turned out to be lower than lambs. Protein interaction network analysis generated by STRING identified MAPK1, SMAD2, SMAD4, CDK1, FOS and ATM as the major findings among 54 significant differentially expressed of proteins. Quantitative real-time PCR analysis was applied to verify the proteomic analysis. These proteins which were identified in lambs may contribute to the reduction of oocyte quality compared to adults. The present research provides understanding of the molecular mechanism for follicle development in lambs.