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DNA Differences Observed Between Blood and Organs
Scrameustache writes "Researcher working on a rare type of aortic abnormality found that the DNA from diseased tissue did not match the DNA from the blood of the same patients So far it's unclear whether these differences in the blood and aortic tissue are the consequence of RNA editing, which changes the messenger RNA but not the gene, or DNA editing, which involves differences in the gene itself. Based on the evidence so far, the researchers believe the differences resulted from developmental rather than somatic DNA alterations. 'Traditionally when we have looked for genetic risk factors for, say, heart disease, we have assumed that the blood will tell us what's happening in the tissue,' lead author Bruce Gottlieb said in a statement. 'It now seems this is simply not the case.'"
Perhaps some of those patients were chimeras .
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
is there an end to the human body's complexity? first they tell us dna has all the answers, then they tell us its dna + environment, then they find out its genes + weird stuff everyone thought was garbage and didn't have any functions, now this? WILL IT EVER END?
weinersmith
what happened to the days of pre-history and we didnt need this, we just ate grass if we didnt feel good
Someday we'll hit the human carrying capacity. And the band will just play on.
... could something like this be overlooked over the past several decades? Wouldn't anybody think to check the DNA across the board, or are we just getting lazy?
Seems like a blindingly obvious discovery, DNA alterations to the blood producing cells don't always immediately and inevitably result in diagnosed Leukemia?
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
This is common to all human.
For e.g. a male homo sapiens sapiens the reproductive organs contain octopus DNA.
in what country's? there might be an external factor at play, besides cancer and chimeric cells. in mice there was an increase of foreign dna present in rats eating modified foods, this is for meat and vegetable products. also why the EU/china banned genetically modified foods.
... but would this discovery have any potential legal ramifications on DNA testing, potentially casting doubt on its validity? Their testing method has to be accurate, or else they could not observe the differences in DNA between blood and organ cells - but are the differences enough to cause one person's DNA to be mistaken for another, or are they small enough to not risk a false positive? I'm not a lawyer or a biologist, but thats the first thing that popped into my head.
DNA from diseased tissue did not match the DNA from the blood
And which (if either) matched DNA from the rest of the body?
Dr. House!
The researchers did NOT say, definitively, that the patients DNA varied between blood and aorta.
What they said was that the SEQUENCING showed a difference. The sequencer used cannot distinguish between messenger RNA and DNA differences.
While it is possible that micro-environment, such as being blood vs. being aorta could result in changes to DNA, it is far more likely to result in tweaks to messenger RNA.
Since they found the same SNPs in aortic tissue from the organ bank, it could just be a common adaptation for that tissue.
Wasn't there a House M.D. episode covering something just like this where the organs and the blood DNA didn't match?
The summary made no sense until I RTFA and found out that they sequenced cDNA, not genomic DNA. The "c" is important, people. It's like the "m" in "vim" or the "ba" in "bash" - if you omit it it's not too far wrong, but in certain contexts it makes a world of difference.
cDNA is a lab-made copy of RNA. That's what the RNA editing versus DNA editing confusion is about. Genomic DNA gets copied to RNA, and then it's further processed. The researchers isolated that processed RNA, and made a cDNA copy of it. This is NOT the conventional way DNA gets sequenced. 99% of the time if you talk about sequencing someone's genes, you're talking about sequencing the genomic DNA directly, without the intermediate RNA step.
People sometimes get mosaicism after stem cell transplants or organ transplants.
I saw an interesting example of mosaicism in a medical journal. An infant was born with half male genitals, half female genitals. The most obvious explanation was that he/she was born of two embryos, one male, the other female, that combined at an early stage (but not too early) and formed a mosaic individual, with patches of male and female cells. Mosaicism actually is pretty common in biology. Sometimes you get patches of skin that vary between 2 colors. The later the embryo recombines, the bigger the patches are.
But this raises the possibility that the DNA of the cells in one developmental branch -- the arteries, or the aorta -- goes through some epigenetic doubling, on a routine basis, because it happened in several samples, even healthy tissue. I wonder if it happens in mice.
My understanding of the article was that they sequenced DNA -- both strands -- not the RNA. But for reasons I don't understand, Schweitzer said it might be the consequences of RNA editing, to the messenger RNA.
Actually they got into chimerizaton at the end of TFA:
In an e-mail message to GenomeWeb Daily News, Navigenics Co-founder and Chief Science Officer Dietrich Stephan said the team's work is interesting and deserves further investigation.
"Differences between the germ-line genome and somatic cells is well established in cancer. It is also well described that chimeras can result from early DNA changes in early embryonic development that propagate to form regional differences in the genome across the body," Stephan noted.
I am not a doctor nor did I completely follow the article, but I assume the cell lifetimes differ between blood and organ tissues. Given this, would we not expect some some sort of micro-evolution going on in frequently-reproducing cell types?
For those who are interested, the original article is published in Human Mutation journal, and can be found here: DOI It requires access to the journal to read beyond the abstract.
My understanding of the article was that they sequenced DNA -- both strands -- not the RNA. But for reasons I don't understand, Schweitzer said it might be the consequences of RNA editing, to the messenger RNA.
From the paper published in the journal Human Genetics (subscription required), the authors sequenced the mRNA from aortic tissue and genomic DNA from the blood of individuals. To sequence mRNA, researchers must first extract the mRNA from cells and convert the mRNA into a DNA sequence (called complementary DNA or cDNA) using the enzyme Reverse Transcriptase. The reason why we do this is because DNA is much more stable than RNA (our bodies contain many enzymes that rapidly degrade RNA. These enzymes are secreted from our skin, so if you literaly touch an RNA sample it begins to degrade. I know because I work with RNA and it is a pain). Furthermore, sequencing procedures are optimized for sequencing DNA strands, not RNA strands. So, when the article refers to sequencing cDNA, it really means sequencing mRNA (indirectly).
Because the authors of the study looked only at the mRNA from the aortic tissue, they cannot exclude the possibility that the mutations in the mRNA arose from RNA editing, and not somatic mutation. It seems like it would have been fairly simple to sequence the genomic DNA from the aortic tissue, and I'm curious as to why the authors did not perform these analyses (perhaps they knew that other groups had made similar findings and wanted to rush the paper out before others could publish?).
I saw an interesting example of mosaicism in a medical journal. An infant was born with half male genitals, half female genitals. The most obvious explanation was that he/she was born of two embryos, one male, the other female, that combined at an early stage (but not too early) and formed a mosaic individual, with patches of male and female cells. Mosaicism actually is pretty common in biology. Sometimes you get patches of skin that vary between 2 colors. The later the embryo recombines, the bigger the patches are.
That has nothing to do with recombining of the embryo (don't know about the story You mention, there it can be an explanation, I am talking about the 2 color story, e.g. a cow or a dog, and mosaicism in general), the different patches exist because of mutations in one embryo. These mutated cells will divide just as the not mutated ones. And the sooner these mutations occur, the bigger the patches will be. And You don't need a stem cell or organ transplant to get mosaicism, You get it in the woomb.
'Because the authors of the study looked only at the mRNA from the aortic tissue, they cannot exclude the possibility that the mutations in the mRNA arose from RNA editing, and not somatic mutation. It seems like it would have been fairly simple to sequence the genomic DNA from the aortic tissue, and I'm curious as to why the authors did not perform these analyses'
Indeed. It's pretty hard to know what, if anything, to conclude from this paper as it's not making a like-for-like comparison. It seems quite possible that they're simply looking at RNA editing, and it isn't even possible to say whether this was tissue specific, because they didn't look at cDNA in the blood samples. Also, although the SNPs (sequence variants) turned up in cDNA from aneurysms, they were also present in cDNA from healthy aortic tissue, so there's no evidence that they are involved in any disease process.
Why is this rated a troll?? Are the producers of Idiocracy mods now? The post was well thought out and reasoned. quite the opposite of "troll"-like.
Well, if You weren't so hasty to call me an idiot and maybe gave your brain a second to process what I was saying, you would see that that was my point also. I never said that we should decide who should survive. I just said that ALL MUTATIONS ARE RANDOM and some will be beneficial while others are just mistakes. So, let me put that in simple words: say one day you are making coffee and, by mistake you add vanilla flavored sugar to it. You might like it, and repeat it often cos that would add some value to your cup of coffee. But, if instead of vanilla it was a salt you added, or even something toxic, you damn sure wouldn't continue to make it, cos that would make your coffee worst. What i was saying was that we shouldn't make people drink salty coffee just because someone made it by mistake.
Wasn't there a Russian claim that the serial killer, Chikatilo (sp?) had different sperm DNA than his blood or saliva,
thus causing a delay in his eventual capture?
Posts like this make me wish the troll mod took two votes to stick (although it only uses up the first mod point). I've had jokes modded troll due to people missing the sarcasm, but seeing insightful comments buried by someone with their own agenda is just wrong. I spend too many mod points undoing bad troll mods. At least /. could limit mods to one -1 for every 5 points they give out.
Yeah, this is offtopic, but if any mod sees this please mod up the "troll" first.
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