Good news!
"When the first baby to be conceived using a technique that mixes genetic material from three people was born, in 2016, scientists worried that the procedure had not been studied to show it was safe. Now, scientists in China have conducted the first comprehensive study of the technique in early-stage human embryos, and report that it does not seem to affect their development.
Techniques for using genetic material from three people to make embryos are designed to prevent mothers with defects in their mitochondria ... from passing them on to their children. Mitochondria contain their own DNA, and children inherit all of their mitochondria from their mother.
“Mitochondrial replacement therapy is a controversial field,” ...
... studied the safety of one of three main types of mitochondrial replacement therapy, called spindle transfer, which was used to make the first baby with genetic material from three people, who was born in Mexico in 2016. In this method, the nuclear DNA from the egg of a woman with faulty mitochondria is transferred to a donor egg with healthy mitochondria that has had its nuclear DNA removed. The egg is then fertilized with the father’s sperm in a test tube. The resulting embryo contains genes from both parents in addition to mitochondrial genes from the donor. ..."
... studied the safety of one of three main types of mitochondrial replacement therapy, called spindle transfer, which was used to make the first baby with genetic material from three people, who was born in Mexico in 2016. In this method, the nuclear DNA from the egg of a woman with faulty mitochondria is transferred to a donor egg with healthy mitochondria that has had its nuclear DNA removed. The egg is then fertilized with the father’s sperm in a test tube. The resulting embryo contains genes from both parents in addition to mitochondrial genes from the donor. ..."
From the abstract:
"Mitochondrial DNA (mtDNA) mutations are often associated with incurable diseases and lead to detectable pathogenic variants in 1 out of 200 babies. Uncoupling of the inheritance of mtDNA and the nuclear genome by spindle transfer (ST) can potentially prevent the transmission of mtDNA mutations from mother to offspring. However, no well-established studies have critically assessed the safety of this technique. Here, using single-cell triple omics sequencing method, we systematically analyzed the genome (copy number variation), DNA methylome, and transcriptome of ST and control blastocysts. The results showed that, compared to that in control embryos, the percentage of aneuploid cells in ST embryos did not significantly change. The epiblast, primitive endoderm, and trophectoderm (TE) of ST blastocysts presented RNA expression profiles that were comparable to those of control blastocysts. However, the DNA demethylation process in TE cells of ST blastocysts was slightly slower than that in the control blastocysts. Collectively, our results suggest that ST seems generally safe for embryonic development, with a relatively minor delay in the DNA demethylation process at the blastocyst stage."
Single-cell multiomics analyses of spindle-transferred human embryos suggest a mostly normal embryonic development (open access)
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