Study reveals how babies born from 3 parents are surprisingly similar to normal babies

Highlighting the similarities between gene expression levels in both normal and spindle transfer (ST) embryos, the researchers note in the paper, “we analyzed the differentially expressed genes (DEGs). The patterns of gene expression were nearly identical for all of the TE, EPI, and PE lineages between the ST and control embryos.”

The researchers analyzed the blastocyst stage in not just a few but over a dozen regular and ST embryos, and they didn’t notice any difference between them. Neither did they come across any factors that posed a risk to the health of the ST embryo. The researchers claim to have made the first detailed comparison of the two types of human embryos.

Stem cell expert and professor at Columbia University, Dietrich Egli believes that the comparison holds great importance since it analyzes the safety of spindle transfer embryos in depth. He suggests these findings could prove to be useful for authorities in analyzing the efficiency and safety of MRT.

However, the Chinese researchers have only taken the blastocyst stage into account, and therefore further research is required to understand the influence of ST on other embryonic development stages in humans.

The study is published in the journal PLOS Biology.

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.

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