
Neurons Constantly Alter Their DNA (2015) - givan
http://www.hopkinsmedicine.org/news/media/releases/neurons_constantly_rewrite_their_dna
======
maxander
The use of "rewrite" is a bit misleading- what's being altered in this
mechanism is an epigenetic tag that sits "on top" of one of the standard DNA
bases; that an individual's epigenetics are altered as they go through life is
well known. But since the underlying cytosine is (as far as we know)
irrevocably bound to this tag, it has to be replaced by a different (but
identical) cytosine. Its more like going over your handwriting to hide an
errant punctuation mark than "rewriting."

~~~
kordless
Actually, it's been a thing for a while that we know the brain has somatic
mutations which cause the DNA to differ from cell to cell. While the
epigenetic tags are also affected, it goes beyond attaching tags. The brain
literally rewrites its own DNA.

[https://www.genomeweb.com/sequencing-technology/single-
neuro...](https://www.genomeweb.com/sequencing-technology/single-neuron-
sequencing-reveals-snvs-brain-cells-diverse-lineage)

~~~
astazangasta
Acquiring somatic mutations is not "rewriting its own DNA", it's just
acquiring mutations. You can't replicate a piece of DNA without the chance of
a mutation happening. The error rate in humans is about 1e-9 mutations/base,
so by the time you've grown a brain you're likely to have a whole bunch of
somatic mutations just by chance.

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astazangasta
This is a bit silly, eh. Every cell in your body does this kind of epigenetic
modification, there are a whole host of factors whose only job is to methylate
DNA. Furthermore, this is not really "altering DNA", the sequence doesn't
change, this is just a way to mask gene expression - if you methylate
cytosines near the promoter region of a gene, RNA polymerase has a harder time
sitting down and transcribing the gene, reducing its expression.

Neurons do this, germ cells do this, immune cells do this, every cell in the
body does this.

What's interesting here is the specific factor (Tet3), not the occurrence of
epigenetic modification. The perils of science journalism, as usual.

~~~
nickledave
Exactly. I should know better and I got caught up in the excitement of
"neurons editing their DNA". The Hopkins press release department was either
clueless or trying to make this paper sexier than necessary. The Tet3 finding
is cool; Wonder if that factor does the same thing in other cells besides
neurons, or if really just responds to synaptic activity.

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harveywi
Many years ago I attended a talk by Bernard Widrow (discovered/invented a
precursor to the backpropagation algorithm; i.e. the least mean squares
filter) [1]. He believed that long-term memories are stored in DNA [2]. At the
time, I and others thought he was completely wrong.

Maybe it is not such a crazy idea. Code is data, after all (especially if our
brains are written in LISP).

[1]
[https://en.wikipedia.org/wiki/Bernard_Widrow](https://en.wikipedia.org/wiki/Bernard_Widrow)
[2]
[https://web.stanford.edu/class/ee373b/cognitive_memory2.pdf](https://web.stanford.edu/class/ee373b/cognitive_memory2.pdf)

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starseeker
I knew it - our brains are written in Lisp!

~~~
DonaldFisk
[http://www.pgc.com/pgc/home-stuff/papers-archive/think-w-
dia...](http://www.pgc.com/pgc/home-stuff/papers-archive/think-w-diag/psych-
rea-lisp.html)

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spinPhysician
This is a pretty cool thing for electric amoeba colonies in skull aquariums to
be messing around with.

I'd wager white blood cells are a species apart, in this territory.

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ArtDev
Is this the mechanism responible?

[http://discovermagazine.com/2013/may/13-grandmas-
experiences...](http://discovermagazine.com/2013/may/13-grandmas-experiences-
leave-epigenetic-mark-on-your-genes)

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rdiddly
Is the word 'toggle' being used correctly in that article? Do they mean
'modulate' maybe? (If they're talking about a continuum, rather than a "one or
the other" polarity.)

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godembodied
If this is the case, then we have an intersting problem. Epigenetics change,
DNA - due to mutations can differ from cell to cell, people get injected with
completely different DNA in the case of organ transplant. New neural pathways
are created. Cells in the body are changed constantly. Memories are changed.
Things like height, weight, personality traits, name, disorders, spatial
location etc. can all be changed as well.

So, this raises the question of whether someone can seriously say: "I did
something 15 years ago" \- when many of the things that make up the human have
been changed plus the person saying it is most likely making up a story about
past(confabulation). What do you think?

~~~
gnaritas
> So, this raises the question of whether someone can seriously say: "I did
> something 15 years ago"

Only if you define "I" as something that doesn't match reality, just because
people change doesn't mean they aren't still themselves. "I" doesn't refer to
some ethereal unchanging thing, it merely refers to the self which is ever
changing.

~~~
godembodied
[removed]

~~~
gnaritas
Questions already well explored by philosophy; nothing in the article raises
any new questions about the nature of self.

