Not Your Mom’s Genes: Mitochondrial DNA Can Come from Dad

[Andy]

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.

https://www.pbs.org/wgbh/nova/article/dads-mitochondrial-dna/

 

[Alvin]

I'm not surprised, apparently intelligence only comes form the mother, another "finding" that is likely to be shattered eventually. Our understanding of DNA transfer and functions is at an early level and there will be many revisions till we get it right.

 

[Trish]

Curiosity led me to this paper from 20 years ago suggesting that the idea that we only inherit mitochondrial DNA from our mothers is false. Apparently there are some mitochodria in the tail of the sperm and in humans the whole sperm enters the egg at fertilization, so there is some paternal mitoDNA at that stage. The paper says there needs to be more research to see whether in some people some of this paternal mitoDNA survives. Looks like this new paper suggests it sometimes happens.

 

[Hutan]

Interesting. Amazing that this is only now a discovery - there's so much yet to discover about genetics.

@BeautifulDay - this finding is relevant to your speculation on the possibility of inheritance of ME/ME-like illness susceptibility via patrilineal lines.

Also, mixed mitochondrial DNA might possibly be a reason for mitochondria not working well under certain circumstances:

A handful of animals, including flies and mice, are known to occasionally “leak” paternal mitochondrial DNA into offspring alongside maternal input, but humans have historically been excluded from this club.

Whatever is driving maternal mitochondrial inheritance, it’s clear our cells have taken quite a few precautions to keep it that way. ...

The addition of another mitochondrial stakeholder, so the theory goes, could muddle this intimate two-way dialogue.

There's an interesting discussion about assisted reproduction where a woman with mitochondrial disease had the mitochondria in her eggs replaced with healthy mitochondria from another woman. There is speculation that turning off the processes that would normally prevent paternal mitochondria being transferred could, in the future, allow the father to contribute healthy mitochondria to the fertilised eggs.

 

[Ravn]

there's so much yet to discover about genetics

For example what health effects, if any, being a chimera might have. Chimera meaning having different DNA (ordinary DNA, not miDNA, I believe) in different tissues. It definitely isn't very helpful when trying to prove you're the mother of your own children:
https://abcnews.go.com/Primetime/shes-twin/story?id=2315693

The DNA test results challenged everything she knew about her family. Yes, her boyfriend was the father of the children, and, yes, they were all related, according to the DNA, except for Fairchild. She was told she wasn't the mother.

Fairchild was certain a mistake must have been made, but she recalled a social worker saying to her, "Nope. DNA is 100 percent foolproof and it doesn't lie."

Fairchild was not only denied government assistance for her young children, she was now suspected of possibly acting as a paid surrogate mother and committing welfare fraud. She was in danger of having her kids taken away for good.

 

[BeautifulDay]

Thanks @Hutan

Very interesting. At one of the UMDF (United Mitochondrial Disease Foundation) conferences I attended last year, one of the mito experts was asked about paternal inheritance. That was the first time I heard someone deviate from the maternal only inheritance pattern of mtDNA. The expert didn't elaborate, but left the door open to paternal inheritance. When pushed, she didn't provide further details -- and she wouldn't discount paternal inheritance as a possibility in mtDNA inheritance.

To me what was most telling was the reaction of the mito experts in the room. Not one looked up. Not one had a head turn. The experts having conversations in the corners of the room, didn't react at all. This group of experts perks up anytime something new, novel, or something one of them disagrees with is mentioned. At that point I knew there was some work going on behind the scenes and there was something they all knew. All of a sudden the standard science 101 lesson of mtDNA can only be inherited from your mother became much more fuzzy.

 

[ScottTriGuy]

For example what health effects, if any, being a chimera might have. Chimera meaning having different DNA (ordinary DNA, not miDNA, I believe) in different tissues. It definitely isn't very helpful when trying to prove you're the mother of your own children:
https://abcnews.go.com/Primetime/shes-twin/story?id=2315693

Wow.

I wonder how many other women (and men) have had / are having their children taken away for this reason. It can't be that common, but traumatically tragic nevertheless for those affected.

 

[Joel]

Other work shows that females as well as having cells with their own DNA (obviously inherited from both parents) they also have cells direct from their mother, and their own children if they have them (DNA gets swapped across the placenta) plus DNA from the father found in their bodies.

And of course, while males only get one X chromosome so it is the same from one cell to the next, females get two versions with one being switched off in each individual cell (meaning different X chromosomes in neighbouring cells). Plus the switching off is not total, some genes at the ends of the switched off X chromosome can still function.

It seems to be the case that females have more diversity of DNA in their bodies than males do.

X chromosome also contains more genes than Y.