Meiotic spindle, spindle checkpoint and embryonic aneuploidy

In mitosis, a spindle checkpoint plays important roles at the metaphase-anaphase transition to ensure the formation of a bipolar spindle, the completion of connecting chromosomes to microtubules and the alignment of all chromosomes at the spindle equator before initiation of anaphase. Components of the spindle checkpoint were first identified through genetic screens in budding yeast and some checkpoint proteins later were found in a wide range of cells from yeast to human. However, the presence and function of the spindle checkpoint in mammalian meiosis, especially female meiosis, have long been disputed but evidence is now accumulating to support the existence. Recent studies indicate that a spindle checkpoint system participates in the regulation of mammalian female meiosis and prevention of embryonic aneuploidy. Here we review recent progress on checkpoint studies in both mitosis and meiosis, toward an understanding of the checkpoint signal transduction pathway and its role in preventing chromosome abnormalities during meiosis. Furthermore, the causes of embryonic aneuploidies and diagnosis are discussed.