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Miscounting Chromosomes

Age-dependent loss of a protein called Sgo2 in human egg cells causes susceptibility to chromosome number faults

02 February 2023

Miscounting Chromosomes

Egg cells or oocytes have unique characteristics that make them different from other cells. One of the main differences is the number of chromosomes – condensed structures of DNA. Most human cells have 46 – 23 pairs – but eggs (and sperm) have only 23. This number is critical because any more or less can lead to infertility and miscarriages. These errors occur during meiosis; specialised cell division that generates egg cells, and these errors become more common as women age, but we didn’t know why. By imaging oocytes from younger women (left) and older women (right), researchers have found that a protein called Sgo 2 (green) is vital to helping the chromosome pairs to line up correctly before being pulled apart by microtubules (orange). In older women, Sgo2 doesn’t localise to the right locations meaning that the chromosomes are not lined up correctly for the big divide, increasing the chances of older eggs not meeting that magic number of chromosomes.

Written by Sophie Arthur

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