Cohesin and the maternal age effect.

During meiosis in human oocytes, chromosome nondisjunction increases with maternal age, leading to disorders such as Down's syndrome. In a recent study in Nature Genetics, Hodges et al. (2005) show that mice with a mutation in the meiosis-specific cohesin protein SMC1beta exhibit age-dependent defects in meiosis. These defects are similar to those observed in oocytes of older human mothers. Their results implicate an age-dependent loss of function in SMC1beta (or related proteins) in the maternal age effect of humans.