Why human egg cells don't age well
Chromosomes are seen as red, and kinetochores are green. (A-B) Bivalent appears normal (green arrows). (C) Bivalent begins to hyperstretch (orange arrows). When egg cells form with an incorrect number of chromosomes--a problem that increases with age--the result is usually a miscarriage or a genetic disease such as Down syndrome. Now, researchers at the RIKEN Center for Developmental Biology in Japan have used a novel imaging technique to pinpoint a significant event that leads to these types of age-related chromosomal errors. Published in Nature Communications, the study shows that as egg cells mature in older women, paired copies of matching chromosomes often separate from each other at the wrong time, leading to early division of chromosomes and their incorrect segregation into mature egg cells.