from Section 3 - Developmental biology
Published online by Cambridge University Press: 05 October 2013
Abstract
The formation of the meiotic spindle is a critical process to assure accurate chromosome segregation and subsequent embryo development. Coordinated formation and organization of microtubules, centrosomes, and chromosomes is important for meiotic spindle formation at the oocyte's center after germinal vesicle breakdown (GVBD), for the formation of the MI (meiosis I) spindle to segregate homologous chromosomes, and for the formation of the MII (meiosis II) spindle to segregate chromatids, resulting in oocyte haploidy. The human oocyte is particularly susceptible to errors in chromosome segregation which may be related to defective centrosome and microtubule organization and to defective chromosome attachment to kinetochore microtubules and loss of molecular surveillance factors. The present chapter is focused on (1) formation of central, MI and MII spindle, with focus on microtubules and centrosomes; (2) chromosome dynamics and segregation during MI and MII, with focus on molecular aspects and surveillance mechanisms; and (3) spindle abnormalities, environmental influences, and possible treatments to restore spindle integrity with implications for assisted reproductive technologies (ART).
Introduction
The formation of the meiotic spindle is a critical step during oocyte maturation and begins when the germinal vesicle breaks down (GVBD) as a result of stimulation by luteinizing hormone (LH). Spindle formation in most mammalian oocytes takes place at the oocyte's center and involves significant restructuring of the cytoskeleton that will impact subsequent cellular and molecular functions that are also important for later development [1]. Coordinated formation and organization of microtubules, centrosomes, and chromosomes begins directly after GVBD with remodeling of these major spindle components in the oocyte's center to form the meiotic spindle.
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