Spindle poles Biology Diagrams The universal features of meiotic spindle formation have yet to be determined; nonetheless, modulation of this process by the bouquet may occur in many eukaryotes. In higher eukaryotes, meiotic spindles can be nucleated from several different structures, including centrosomes, MTOCs, and complexes of motor proteins. Herein, we describe the recent advances in understanding the mechanisms controlling formation of the meiotic spindle in metaphase I (MI) and metaphase II (MII) in mammalian oocytes, and focus on the differences between mouse and human oocytes. Unlike mitotic cells, mammalian oocytes lack typical centrosomes that consist of two centrioles and
Expressed throughout meiotic progression, PLK1 promotes meiotic progression and is needed for high-quality meiotic spindle formation (Pahlavan et al., 2000; Solc et al., 2015). Overall, the important role of PLK1 in oocyte meiosis, its responsiveness to exogenous and endogenous signals, and the known adverse effects of these signals on meiotic
Telomeres and centromeres have interchangeable roles in promoting ... Biology Diagrams
ery—the oocyte meiotic spindle—that distinguish it from the mitotic spindle, and discuss recent progress in understanding the molecular mech-anisms that mediate spindle assembly early in oocyte meiosis I. Finally, we will review the spindle dynamics that align and segregate chromosomes later in meiosis I to produce a haploid genome. 2. Additionally, localized protein synthesis to support spindle formation is achieved in the spindle forming region, whilst protein synthesis is reduced elsewhere in the ooplasm. This is achieved through enrichment of spindle-related mRNAs in the spindle forming region combined with local PLK1-mediated phosphorylation and inactivation of the Meiotic spindle abnormality in human oocytes is a hallmark of maternal ageing [44], [196]. In conclusion, it is clear that there are gene products that are essential for control of spindle formation, chromosome cohesion and chromosome segregation in meiosis. These possibly present targets for chemicals that specifically interfere with
Centromere-telomere interchangeability in promoting meiotic spindle formation. Meiotic progression is represented from left to right. (A) In WT meiocytes, the movement of telomeres to the SPB promotes modification of Sad1 (yellow stars) or the NM surrounding Sad1, in turn promoting Sad1 accumulation and ensuring bipolar spindle formation. Although centrosome-mediated spindle formation is dominant in most mitotic cells, mitosis can still take place in the absence of centrosomes, showing that other centrosome-independent pathways can participate in spindle formation (Khodjakov et al., 2000; Basto et al., 2006; Azimzadeh et al., 2012; Bazzi and Anderson, 2014). These centrosome
