Great joke I just heard: How many monkeys does it take to make a baby? Answer: Three. Two for chromosomal DNA, and one for mitochondrial DNA. Ha ha ha… Yeah…maybe it’s only funny to geneticists.
Scientists at the Oregon Health and Science University (OHSU) were able to produce the first primates with three biological parents. Four macaque monkeys were born through an in vitro fertilization process in which the DNA of two females and one male were combined. Of the two mothers, one provided all the chromosomal DNA while the other only provided mitochondrial DNA. This technique may eventually be developed into a treatment in humans so that women with defects in their mitochondria can have healthy offspring. The successful test also raises concerns about genetically engineered babies because the new monkeys will pass on the genetic alterations to their offspring.
The mitochondria organelle often gets called the power house of the cell because of its role in creating energy releasing molecules. However, it could also be called the ticking time bomb of the cell because as many as 1 in 4000 people develop illnesses due to defects in their mitochondrial DNA. Sometimes these defects can be passed on from a mother who has no outward signs of the condition. Those people with this type of genetic problem have risks for certain kinds of epilepsy, cancer, diabetes, heart disease, liver disease, deafness and blindness. The work at OHSU demonstrates that a carrier could pass on the 99% of her DNA that is healthy (chromosomal) and use a donor to fill in the missing 1%.
Shoukhrat Mitalipov from the Oregon National Primate Research Center lead the study. The four healthy macaque monkeys (named Mito, Tracker, Spindle, and Spindly) are a good first step in his plans to eventually bring the technique to humans. However, Mitalipov is quick to point out that a technique is not a treatment, and it will likely be several more years before human clinical trials could be considered. Additionally, he would need to see how the new monkeys produce offspring to see if there are any problems with the passing of genetically altered DNA to offspring.
The passing on of genetic alterations, called germline engineering, has raised a lot of interest for medical ethicists. Mitalipov’s work is a remarkably specialized case of germline engineering: only mitochondrial DNA was swapped out, and its goal is purely to avoid known defects. In the grander scheme of things though, germline engineering could lead to designer babies if applied to chromosomal DNA. Currently, the hoops it would take to produce an engineered human baby are many: USDA approval, using only private or state funds, and bypassing laws which forbid clinical trials using genetically modified embryos.
Similar laws are in place in the UK where Newcastle University is pursuing results closely related to the work done at OHSU. Scientists there have a similar technique (though it is reputedly less efficient and has DNA swaps occurring after insemination). And some British scientists are working to get exemptions from their Human Fertilization and Embryology Act (HFEA). That law prohibits implanted altered embryos into a womb.
The fact that four baby monkeys are raising such concern shows the importance of germline engineering. The OHSU work, which focuses on one day helping to cure a certain kind of DNA defects may also reveal how designer babies eventually find their way to market. Parents want the best for their children, genetically as well as environmentally. If their exists a way for them to avoid giving their child a few bad genes, they are likely to take it. As we’ve said before, parents are already selecting embryos for that very reason. It’s only a matter of time before swapping DNA between mothers stops being just monkey-business.
[photo credits: Nature]