During female meiosis, 3/4 of the chromosomes are eliminated and only 1/4 of the chromosomes are inherited by a single egg. In contrast, all chromosomes are distributed among 4 sperm during male meiosis. The elimination of 3/4 of the genome to allow inheritance of only 1/4 of the chromosomes is conserved in all animal phyla, suggesting some fundamental selective advantage. The long-term goals of this project are to elucidate the molecular mechanisms of chromosome elimination and elucidate the selective advantages of asymmetric meiotic division. Errors in meiosis lead to the absence of one chromosome (monosomy) or the presence of an extra chromosome (trisomy) in 10-30% of human conceptions with the majority of these aneuploidies leading to embryonic death. By elucidating the mechanisms of meiotic chromosome elimination in C. elegans, we will identify mechanisms likely to be defective during human meiosis. In this project we will pursue 3 specific aims: 1. Elucidate mechanisms that prevent the sperm from interacting with the oocyte meiotic spindle. 2. Determine how the meiotic spindle is attached at the cortex to facilitate extrusion of chromosomes into polar bodies. 3. Determine the mechanisms by which unpaired chromosomes are selectively extruded into polar bodies to correct trisomy.
These aims will be addressed by time-lapse imaging of fluorescent protein fusions within meiotic embryos that have been depleted of key cytoskeletal regulators and cell-cycle regulators by RNA interference.
The proposed research is relevant to public health because chromosomes are missing or an extra chromosome is present in 10-30% of human conceptions. The majority of these chromosomal abnormalities are caused by defects during female meiosis and these chromosomal abnormalities lead to embryonic death or cognitive disability. The proposed research will reveal mechanisms that may cause these abnormalities in humans and will suggest ways to prevent them.
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