The cohesion protein REC8 is involved in sister chromatid cohesion and aneuploidy in young versus old oocytes.

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– Claim (1-2 sentences), Evidence (1 paragraph), Explanation (1 paragraph)

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Bumwon Kwak (Brandon)

BICD 100

Prof. Mcdonnell

29 October 2017

Writing Assignment # 2

Claim: The cohesion protein REC8 is involved in sister chromatid cohesion and aneuploidy in young versus old oocytes.

Evidence: Aneuploidy is known to often result from chromosome misalignment at metaphases stages. From Fig. B, REC8 intensity is significantly decreased in old age. The deteriorated chromosome cohesion is a leading source of aneuploidy in oocytes in a natural aging mice model. In Fig. F, the interkinetochore distant apart, this happening at Metaphase I and II, showing decreased centromere cohesion. The levels of the meiotic cohesin protein REC8 are harshly decreased on chromosomes in oocytes from old (Jessberger, 2012).

Explanation: There is association among REC8, sister chromatid cohesion, and aneuploidy in young and old oocytes. In Fig. G, Oocytes show increased chromosome misalignment with age, as opposed to when oocytes have reduced misalignment to when young. Oocytes coming from young and aged SAM (senescence-accelerated mice) exhibit centromere linked protein-E (CENP-E) at centromeres of all chromosomes, comprising misaligned chromosomes from aged SAM. Oocytes are prone chromosome mis-segregation, and aneuploidy intensifies with age. As oocyte age surges sister chromatid cohesion is weakened or lost. Cohesion weakening seems to contribute considerably to age-dependent aneuploidy (Garcia-Cruz, 2010). Cohesion defects caused aneuploidies is showed through chromosome segregation dynamics at Anaphase I in live oocytes and counted chromosomes in the subsequent Metaphase II eggs. Age-related aneuploidies are due to weakened centromere cohesion. In conclusion, maternal age-associated upsurge in aneuploidy is habitually due to a failure to efficiently substitute cohesion proteins that are lost from chromosomes during aging.


Garcia-Cruz, R., Brieno, M. A., Roig, I., Grossmann, M., Velilla, E., Pujol, A., … & Garcia Caldes, M. (2010). Dynamics of cohesin proteins REC8, STAG3, SMC1 β and SMC3 are consistent with a role in sister chromatid cohesion during meiosis in human oocytes. Human reproduction25(9), 2316-2327.

Jessberger, R. (2012). Age‐related aneuploidy through cohesion exhaustion. EMBO reports13(6), 539-546.

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