Weakened Centromere Cohesion Is the Primary Cause of Age-Related Aneuploidy in Oocytes.

Meiosis: SUMO Keeps a Tight Grip on Sister Chromatids

“…Understanding the mechanisms by which chromosome cohesion is established and maintained is of acute importance in the mammalian oocyte. Recent experiments employing oocytes from mice of advanced age, as a model of human aging, have shown that meiotic chromosome cohesion in oocytes is progressively lost with age [9,10], an observation that has been confirmed directly in human oocytes [11], providing at least part of the explanation as to why oocytes from older females are more likely to be aneuploid. Whilst a reduction in Sgo2 has been noted in aged oocytes [10,12], some unwanted age-related cohesion loss may ensue after anaphase of meiosis-I [12].…”

Oogenesis: Ageing Oocyte Chromosomes Rely on Amazing Protein Stability

“…These papers and an earlier report showing that cohesin does not need to be newly synthesized postnatally to maintain sister chromatid cohesion [10] support the concept that an astonishing stability of selected chromosomeassociated proteins is key to chromosome inheritance during oogenesis: chromosome segregation in oocytes in the adult seems to rely on preexisting CENP-A and on cohesins that were produced prenatally. It is clear that even this amazing protein stability eventually fails, at least in the case of cohesin, since in old wild-type mice increased rates of loss of cohesion and increased inter-kinetochore distance are observed [11,12]. Thus, cohesin and perhaps CENP-A dosages seem to be important and need to be maintained.…”