Mathematical modeling of human oocyte aneuploidy

Area of Science:

• Reproductive biology
• Genetics
• Mathematical modeling

Background:

• Aneuploidy is a primary cause of pregnancy loss, birth defects, and IVF failure.
• Most aneuploidies are believed to stem from female meiotic errors, but quantitative data linking specific mechanisms to outcomes are scarce.

Purpose of the Study:

• To develop a mathematical framework for quantifying the contributions of various chromosome missegregation mechanisms to aneuploid egg production.
• To analyze aneuploidy data and identify patterns in female meiosis.

Main Methods:

• Developed a mathematical model incorporating probabilities of chromosome gain/loss from meiotic errors (meiosis I/II nondisjunction, PSSC, RS).
• Fitted the model to aneuploidy data from 11,157 human blastocyst-stage embryos.

Main Results:

• The model accurately reflects known aspects of female meiosis, including the maternal age effect on premature separation of sister chromatids (PSSC).
• Identified a novel pattern: increased frequency of meiosis II errors in eggs with prior meiosis I errors, suggesting a link between ploidy status and nondisjunction (NDJ).
• Demonstrated the model's utility in identifying IVF patients with high aneuploid embryo production.

Conclusions:

• The mathematical model provides a powerful tool for understanding chromosome missegregation mechanisms in human female meiosis.
• The findings offer insights into the relationship between sequential meiotic errors and aneuploidy.
• The model can aid in predicting assisted reproduction outcomes and identifying patient-specific risk factors.