Reproduction Abstracts

Chromosomes must be properly segregated during meiosis to transmit the correct set of the parental genome into gametes. Incorrect chromosome segregation produces aneuploid gametes, fertilization of which results in pregnancy loss and congenital diseases such as Down syndrome. However, it is known that the frequency incorrect chromosome segregation is extremely high at meiosis I in oocytes (20–40% in humans), compared to other cell divisions. Moreover, the frequency of the errors increases with maternal age. Why chromosome segregation is so error-prone and age-related in oocytes is not fully understood.

In this study, we established a high-throughput and high-resolution imaging of chromosome dynamics in live oocytes from naturally aged mice. Our 4D recording with automated microscopy detected nearly 100% of kinetochores and chromosomes at every timepoint from germinal vesicle breakdown to anaphase of meiosis I, at a high spatiotemporal resolution sufficient to robustly track all kinetochores and chromosomes. Our high-throughput approach yielded the datasets of >200 oocytes from aged mice, including >10 oocytes that underwent chromosome segregation errors at meiosis I. Thus, these datasets provide the first quantitative analysis of ‘at-risk’ single chromosome dynamics and a comprehensive resource to identify the major causes of age-related chromosome segregation errors at meiosis I in oocytes.