[DIYbio] Re: expressing your own DNA, autoimmune question

Hi Nathan!

No, this would *probably* not cause an autoimmune situation.  Changing a few base pairs will probably make a protein similar enough to the existing transporter, that the immune system will still see it as "self."  However, it really depends on the specific change made--does it make a big difference in the conformation?  Are you adding or subtracting cysteines, which tend to really influence the epitopes?  Does it change the cleavage sites by the proteosome? etc....

Same goes for expressing a lung protein in the liver...it will probably not cause autoimmune disease.  There's actually a kinda cool reason.  Epithelial cells in the thymus express the transcription factor AIRE, which causes them to express a whole bunch of organ-specific proteins.  So in the thymus there are lung proteins, liver proteins, etc.  Therefore developing Tcells are eliminated if they react against almost any organ.  Tcells ending up in the liver should be tolerant against the lung, too.  There's always a chance that when you introduce a new antigen to a new compartment something unexpected will happen, but in this case I think it's pretty small.

Inhaling naked DNA sounds cool, but I'm doubtful it would actually result in much gene expression.  I do some in vitro transfection of plasmid DNA into human and mouse cells, and there's 2 issues.  First, you need to get the DNA through the cell membrane--this can happen naturally at very low levels, like in the 1st paper you cited.  However, to get any significant percentage of the lung cells to express it, you will probably need some sort of transfection reagent, which tends to be toxic.   2nd, it's very difficult to get non-dividing cells to express genes from naked DNA (I've tried!).  My understanding is, the nuclear envelope breaks down during cells division, allowing extra DNA to get in and be transcribed.  In a resting cell, the DNA can't move into the nucleus.

Don't let me stop you exploring this though, I wouldn't be surprised if there's some researcher already trying to do what you're describing!

Mike



On Wednesday, January 29, 2014 5:44:04 PM UTC-5, Nathan McCorkle wrote:

We've talked before about GFP tattoos, insufflation of DNA showing up
in the liver and lymph nodes (1) and all the talk about different
phage vectors.

None of the questions have talked much about self-provided DNA (clonal).

In the case of Cystic Fibrosis, the ion channel gene is messed up.
Does changing a few basepairs to fix the gene, then re-introducing
that gene in some kind of degradable vector set off the non-self
immune system?

By degradable vector I mean it doesn't replicate or integrate, maybe
this is just naked DNA with some synthetic mods to resist immediate
degradation, or naked DNA with some protein packaging.

Seems like a daily inhaler-full of linear/plasmid DNA would be better
than percussion:
https://en.wikipedia.org/wiki/Cystic_fibrosis#Other_treatments_for_lung_disease
https://en.wikipedia.org/wiki/Percussion_(medicine)

Now assuming an inhaled DNA takes the same route as the insufflated,
rather than affecting the lungs, we move on to other genes. Maybe
vitamin-C genes, GULO is 19% different compared to a functional rat
gene (2), not sure how many bp would need to be tweaked to get human
form to function.

Now I don't know whether the GULO pseudogene is even currently
expressed, if not, then it seems that a semi-clonal functional copy
would show up as non-self. Seems that if you had some constitutively
*repressed* gene, the same logic would apply.

So my last question is, what if you simply want to over-express genes
already expressed in the body? Maybe they don't normally express in
the liver/lymph, or maybe their are multiple genes that normally
express in different organs or vesicles.

It would probably be bad (or maybe benign) to express a clonal lung
ion-transporter in your liver (I don't have cystic fibrosis, so I
assume it would show up as self), but would it lead to an autoimmune
situation?

1.
http://diyhpl.us/~bryan/papers2/bio/Nasal%20absorption%20and%20biodistribution%20of%20plasmid%20DNA.pdf

2.
http://www.ece.drexel.edu/gailr/group/drexel%20summer%20mentorship%20poster.ppt.pdf

--
-Nathan