Nova By Katherine J. Wu November 26, 2018
The first time Taosheng Huang saw the test results, he was sure there’d been a mistake. Even after a technician repeated the diagnostic, Huang didn’t believe it. “That’s impossible,†he said.
Huang, a pediatrician and geneticist at Cincinnati Children’s Hospital Medical Center, asked the patient to come back and provide fresh samples of blood, which Huang then split among several research labs to reduce any chance of error. It was a finding that Huang knew would break a central tenet of human genetics—but time and time again, the outcome was the same.
Huang’s patient, a four-year-old boy, was carrying two different sets of mitochondrial DNA: one from his mother, as expected—and another, from his father.
This was only the beginning. Using modern DNA sequencing technology, Huang and his colleagues have conclusively verified paternally-inherited mitochondrial DNA in 17 individuals spanning three unrelated families. Their work appears today in the journal PNAS.
“This is a really groundbreaking discovery,†says Xinnan Wang, a biologist at Stanford University who studies mitochondria but was not involved in the new findings. “It could open up an entirely new field... and change how we look for the cause of [certain] diseases.â€
Broadly speaking, we’re each a genetic mix of Mom and Dad. In the nucleus, which contains our chromosomes, this holds true. But the nucleus isn’t the only part of the cell that contains DNA. Cells contain power centers called mitochondria that also carry their own sets of DNA—and in nearly all known animals, mitochondrial DNA is inherited exclusively from the mother. This lopsided acquisition is so ingrained that researchers often analyze mitochondrial DNA to trace maternal lineages back in time.
Scientists still aren’t completely sure why this process has evolved to be strictly matrilineal, but a few theories have come to the forefront. For one, the mitochondria of sperm are believed to experience higher rates of mutation than those in eggs, making their input somewhat riskier. Additionally, having only one type of mitochondria makes it easier for the genomes in the nucleus and mitochondria to coordinate, as both generate the raw materials necessary for proper cellular function, explains Sophie Breton, a mitochondrial geneticist at the University of Montreal who did not participate in the study. The addition of another mitochondrial stakeholder, so the theory goes, could muddle this intimate two-way dialogue.
More:
https://www.pbs.org/wgbh/nova/article/dads-mitochondrial-dna/
