Polar body-based preimplantation diagnosis for X-linked disorders

Area of Science:

• Reproductive genetics
• Molecular diagnostics
• Embryology

Background:

• Preimplantation genetic diagnosis (PGD) for X-linked disorders often relies on gender determination, leading to the unnecessary discarding of 50% of unaffected male embryos.
• This practice presents a significant limitation for couples seeking to avoid passing on serious genetic conditions.

Purpose of the Study:

• To introduce and evaluate preimplantation genetic diagnosis (PGD) using sequential first and second polar body analysis as an alternative to gender determination for X-linked disorders.
• To identify mutation-free embryos for transfer, thereby improving the efficiency and success rates of PGD.

Main Methods:

• A novel PGD method involving the analysis of both first and second polar bodies was applied to eight couples at risk for X-linked disorders.
• Oocytes were subjected to standard in vitro fertilization (IVF), followed by polar body removal and multiplex nested polymerase chain reaction (PCR) for simultaneous mutation and linked marker analysis.

Main Results:

• Thirteen PGD cycles resulted in the identification of 25 mutation-free embryos, which were transferred to patients.
• Four clinical pregnancies were achieved, leading to the birth of four children. Three children were unaffected, while one experienced misdiagnosis due to allele dropout (ADO), a predictable event for certain mutations like FMR1.

Conclusions:

• Sequential polar body analysis is a clinically useful alternative to PGD by gender determination for X-linked disorders.
• This method enhances the ability to select mutation-free embryos, offering a more effective approach for at-risk families.