Mitochondrial donation embryos appear to develop normally
Progress Educational Trust23 August 2022
Embryos produced using a method designed to allow women who are carriers of a mitochondrial condition to have genetic children without passing on their mitochondria, are similar to those produced using IVF with ICSI.
Cells from embryos created using a form of mitochondrial donation called maternal spindle transfer had comparable levels of aneuploidy and genetic expression to control embryos created using ICSI, a recent study published in PLOS Biology by researchers from Peking University, Beijing, China showed.
Professor Dusko Ilic, professor of stem cell science at King's College London, who was not involved in the research said: 'There is nothing surprising here. This study only further confirms that the spindle transfer is a safe technique for preventing transfer of mitochondrial mutations from mother to the embryo/child. The method has already been used in the clinic.'
Maternal spindle transfer is just one of the methods that can be used to avoid mitochondrial DNA in a mother's egg from being transmitted to the subsequent embryo. In this method, nuclear material from the mother's egg is transferred to an unfertilised donor egg, which is then fertilised before the embryo is transferred to the uterus. Other methods exist which involve moving nuclear material shortly after fertilisation, rather than shortly before.
The first baby born using maternal spindle transfer during IVF was born to a mother who was a carrier of Leigh Syndrome in 2016. Australia is the latest country to have legislated for the use of mitochondrial donation, having done so in March this year.
Cells from 24 embryos created using this method were studied and it was found that 22 percent were aneupolid, meaning they had the wrong number of chromosomes, compared to 17 percent of cells studied from the 22 control embryos, created using ICSI. This was 'comparable' rate of aneuploidy the authors said.
Cells taken from the three different layers of the blastocyst were also found to have RNA expression that was comparable to the control blastocysts created using ICSI, suggesting that the transcription of DNA was similar and not affected. DNA methylation levels were also similar in cells taken from the epiblast and primitive endoderm of the blastocysts of the embryos created using maternal spindle transfer when compared to the controls, but higher DNA methylation was observed in the trophectoderm. Authors suggested this could be due to a delay in methylation in embryos created using maternal spindle transfer, but proposed that the embryos could catch up.
The authors also called for further research to closely monitor the health of children born via maternal spindle transfer, to determine the safety of the technology.
Sources and References
16 August 2022. PLOS Biology
Single-cell multiomics analyses of spindle-transferred human embryos suggest a mostly normal embryonic development
16 August 2022. Phys Org
Pre-fertilization DNA transfer to avoid mitochondrial disease inheritance appears safe
17 August 2022. Genetic Engineering and Biotechnology News
Human embryos produced by spindle transfer develop (mostly) normally
17 August 2022. Genome Web
Mitochondrial replacement therapy embryos appear largely normal in single-cell 'omics analyses
Reproduced with permission from BioNews, an email and online sources of news, information and comment on assisted reproduction and genetics.