Comparative proteomic analysis of mature and immature oocytes in domestic cats

Abstract

Objective: To evaluate changes of feline (Felis catus) oocytes proteins during in vitro maturation by using the proteomic approach. Methods: Immature oocytes (germinal vesicle) isolated from female cats were cultured and collected at 0 h and 24 h. After collection, oocytes were investigated into immature (germinal vesicle) and mature (metaphase II) stages. The qualitative profiles of the proteins at the immature and mature stages were determined by one-dimensional electrophoresis and liquid chromatography-mass spectrometry. Results: Our data revealed that following 24 h in vitro maturation the maturation rate (metaphase II stage) was 58.7%. Eighty-one of the 260 proteins analyzed were differentially expressed between the germinal vesicle stage and the metaphase II -arrest stage. Proteomic analysis of germinal vesicle and metaphase II oocytes showed abundant expression of proteins involved in transportation (10%), indicating that this was a major characteristic of germinal vesicle oocytes. Similarly, analysis of the proteome of metaphase II oocytes indicated that cell cycle proteins were overexpressed. Interestingly, proteins involved in DNA repair and apoptosis were only expressed in germinal vesicle oocytes and proteins involved in fertilization were only expressed in metaphase II oocytes. Conclusions: The overexpression of certain proteins in germinal vesicle and metaphase II is necessary for oocyte development and maturation. Our findings provide a valuable resource for further investigations into protein expression in oocytes at different developmental stages.