Researchers have a new understanding of the process cells use to ensure that sperm and eggs begin life with exactly one copy of each chromosome a process that must be exquisitely regulated to prevent problems such as miscarriages and mental retardation. The new work reveals how gluelike protein complexes release pairs of chromosomes at precisely the moment of meiosis the specialized cell division process that produces sperm and eggs enabling them to separate properly.

The researchers, led by Howard Hughes Medical Institute investigator Angelika Amon, published their findings online May 3, 2006, in the journal Nature. Amon and her colleagues are at the Massachusetts Institute of Technology.

Most cells in the human body all those other than sperm and eggs contain 23 pairs of chromosomes. These cells divide through mitosis, a process that creates daughter cells with the same complement of chromosome pairs as the parent. Sperm and egg cells, on the other hand, must contain only half the chromosomes of their parent cells, so that the normal chromosome number will be restored when the sperm and egg unite during fertilization. To achieve this, they are produced through meiosis.

Gluelike protein complexes called cohesins, which hold the members of a chromosome pair together until just the right moment during cell division, are central to both processes. Bound together by cohesins, chromosome pairs must organize themselves in preparation for cell division before they can be released.

According to Amon, a deeper basic knowledge of the mechanism of cohesin loss during meiosis could ultimately improve understanding of the origins of miscarriages and mental retardation due to mis-segregation of chromosomes.

"We first need to understand the key regulatory players and the molecular mechanisms that cause chromosomes to segregate in this very unusual way during meiosis," she said. "Once we have a good enough understanding, then we
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Contact: Jennifer Michalowski
michalow@hhmi.org
301-215-8576
Howard Hughes Medical Institute
8-May-2006

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