The Effect of Allelic Variation on Genetic Recombination and Oocyte Quality

Priya Kosana

Document Type

Article

Publication Date

Summer 2021

JAX Location

In: Student Reports, Summer 2021, The Jackson Laboratory

Abstract

Genetic recombination is a vital aspect of meiosis that allows for both genetic diversity and the proper segregation of chromosomes. However, little is known on how allelic variation plays a role in the efficiency of genetic recombination and how it impacts egg quality. To investigate this potential relationship, we analyzed the crossovers (CO) and chromosome synapsis across a panel of genetically diverse mouse strains including the founder and collaborative cross strains. Analyzing microspreads prepared from embryonic oocytes enriched for pachytene stage, we were able to point towards strains with a higher level of asynapsis. Using the MLH1 protein as a marker for CO and immunofluorescent imaging, we quantified crossover sites on the synaptonemal complex (SC). In fully synapsed pachytene oocytes all tested strains except A/J showed average number of COs ≥ 20. Interestingly, A/J strain also has a high percentage of oocytes with asynapsed chromosomes. In this study, we were unable to distinguish asynapsed from desynapsed chromosomes therefore there is a possibility that synapsed chromosomes lacking COs have desynapsed prematurely. Chromosomes lacking COs can be miss-segregated during meiotic divisions and result in an aneuploid egg. Together, our results indicate that undetermined allelic variants present in A/J strain affect recombination efficiency and increase the risk of aneuploidy in ovulated eggs.

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