Mitochondrial Manipulation Technology Unlikely in United States Anytime Soon

Ricki Lewis, PhD


February 27, 2015

In This Article

Lawmakers in the United Kingdom voted recently to allow fertility clinics to use mitochondrial manipulation technology (MMT) to enable women with mutations in mitochondrial genes to have genetically healthy children . But the US Food and Drug Administration (FDA) is being much more conservative and is awaiting results of further preclinical research before allowing clinical trials to begin. The technology is of concern because it manipulates the germline, something many countries prohibit.

Shortly before Parliament met, researchers at the Wellcome Trust Centre for Mitochondrial Research at Newcastle University published an updated estimate of the prevalence of mitochondrial disease carriers in the United Kingdom at 0.4%.[1] Extrapolating from population statistics on women in northeast England, including fertility rates, the researchers project that the average number of births per year for the 2473 women in the United Kingdom who carry mitochondrial mutations is 152, and the average number of births per year for the 12,423 women in the United States who carry these mutations is 778.

Two forms of MMT are under debate. One, called "maternal spindle transfer," moves the genetic material attached to the meiotic spindle from an oocyte of a woman who has a mitochondrial mutation into an enucleated oocyte from another woman whose mitochondria are normal. The oocyte is then fertilized using intracytoplasmic sperm injection. The second approach, pronuclear transfer, introduces genetic material from both an oocyte and a sperm (the putative parents) into an enucleated oocyte from a donor whose mitochondria are normal. The first technique is performed on human gametes, but the second intervenes as a fertilized ovum forms.

Both strategies are what the media has termed "three-person IVF," although the mitochondria contribute only 13 types of protein-encoding genes, compared with the 20,000 from each of the other two "parents." That is, the "third person" contributes far less than 1% to the DNA of the resulting fertilized ovum.

Preclinical work has been painstakingly slow because of the scarcity of human oocytes and ethical concerns about working with human embryos. Most research is done on nonhuman primates and on human embryos up to the blastocyst stage. In the United States, the Dickey-Wicker Amendment of 1995 prohibits the creation or destruction of human embryos used in research funded by the Department of Health and Human Services, which includes the National Institutes of Health.


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