There are several genetic diseases which originate not from mutations in the nuclear genome but mutations in the mitochondrial genome. In humans, the threshold for disease occurrence is if 60% of the mitochondria has mutated mitochondrial DNA (mtDNA) (a mixed mitochondrial origin is called heteroplasmy). There is currently no cure, and no good way to prevent these genetic diseases.
Since the source of the mitochondria is solely from the oocyte, a lot of effort is invested in trying to get rid of mutated mitochondria by in-vitro fertilization (IVF) procedures – thus preventing the disease in the offspring. Two methods have been tried so far – pronuclear transfer (PNT) and spindle-chromosome transfer (ST). The idea is to extract the nuclear genetic material of the oocyte or zygote and transfer it to an enucleated oocyte or zygote with healthy mitochondria. However, in both cases, there is still carry-over of some mutated mitochondria to levels that can be as high as 44%.
In this new paper published in Cell, a group of researchers from China suggest a different approach. Continue reading