Abstract
Cep55 is a relatively novel member of the centrosomal protein family. Here, we show that Cep55 is expressed in mouse oocytes from the germinal vesicle (GV) to metaphase II (MII) stages. Immuostaining and confocal microscopy as well as time lapse live imaging after injection of mRNA encoding fusion protein of Cep55 and GFP identified that Cep55 was localized to the meiotic spindle, especially to the spindle poles at metaphase, while it was concentrated at the midbody in telophase in meiotic oocytes. Knockdown of Cep55 by specific siRNA injection caused the dissociation of γ-tubulin from the spindle poles, resulting in severely defective spindles and misaligned chromosomes, leading to metaphase I arrest and failure of first polar body (PB1) extrusion. Correspondingly, cyclin B accumulation and spindle assembly checkpoint (SAC) activation were observed in Cep55 knockdown oocytes. Our results suggest that Cep55 may act as an MTOC-associated protein regulating spindle organization, and thus cell cycle progression during mouse oocyte meiotic maturation.
Highlights
IntroductionCep[55], a coiled-coil protein whose gene is located in 10q23.33, is important for the completion of cytokinesis
After germinal vesicle breakdown (GVBD), Cep[55] gradually accumulated around the nuclear area, and it co-localized with α -tubulin of the spindle
Knockdown of Cep[55] in meiotic oocytes lead to spindle organization defects and chromosome misalignment, arresting the cell cycle in the MI phase. These results suggest that the main function of Cep[55] in meiosis is to organize microtubules to form the spindle
Summary
Cep[55], a coiled-coil protein whose gene is located in 10q23.33, is important for the completion of cytokinesis. It is located to the centrosomes, mitotic spindle, spindle midzone and midbody in somatic cells[12,13,14]. It recruits two components of the ESCRT machinery: the ESCRT-I complex and ALIX15,16, leading to the recruitment of ESCRT-III subunits, which are required for normal midbody morphology and are believed to have membrane scission activity[17,18,19]. Cep[55] is important for midbody integrity and cell abscission in cytokinesis[12,14,20,21,22]. We show that Cep[55] functions differently in meiotic oocytes than in mitotic cells
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