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The science behind the breakthrough

The science behind the breakthrough

The new technique, called “early pronuclear transfer”, involves transplanting the nuclear DNA from a fertilised egg into a donated egg, which contains healthy mitochondria, on the day of fertilisation.

Extensive studies conducted in a collaboration between the Newcastle team and researchers from University of Oxford and the Francis Crick Institute indicated that embryos created using the new technique are indistinguishable from those created by conventional IVF.  Analysis of thousands of genes in single cells detected no difference between the two types of embryos. There was also no increase in chromosomal abnormalities, which can cause miscarriage and birth defects. These findings provide reassurance that the new procedure does not have a harmful effect on early embryonic development.

The research findings also indicate that the new technique will result in a minimal amount (less than 2%) carryover of disease-causing mitochondrial DNA to the embryos.  The importance of keeping carryover to a minimum is highlighted by studies on embryonic stem cell lines.

The team found that one of five stem cell lines derived from embryos created using the new technique showed an increase in the percentage of mitochondrial DNA carryover. While stem cells are very different from embryos, the observation raises the possibility that faulty mitochondrial DNA may persist in some cases. However, the research team is optimistic that the new technique will be effective in reducing the risk of disease in children of affected women.

A further important finding of the study is that the technique will work best if patient, rather than donor, eggs are frozen. It will therefore be possible for affected women to have their eggs frozen for future use. This is likely to increase the success of the treatment by helping to avoid the decline in egg quality as women get older.

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