Genetic Stem Cell Manipulation

Benedryl Patanol writes "A team at the University of Wisconsin has successfully deleted a 'disease gene' from human embryonic stem cells. This is a first for manipulating stem cell's genetic material because of the difficulty in culturing and controlling their development. With this new method, the genes can be manipulated so as to control the kind of tissue the cells form into and the research is already trying to recreate brain cells that die off with Parkinsons Disease. The article also talks about the resurgence of ethical inquiries that are making this technology a very intense debate in the US."

Obvious

[Y Ddraig Goch]

Here is the obligatory Mutant-X post. Can any one say genome-X?

Covered in the article, but...

[Sgt York]

This is not a first on the whole, only a first with human cells. The technology has been around for a long time (by molecular biology standards), and really isn't all that difficult, exceptionally tedious, but not very difficult. This just represents its first application to human stem cells, as opposed to mouse, rat, etc.

The guy points out that the genes responsible for graft rejection could be eliminated; this is problematic. First, it gets complicated when you try to remove several genes at once. Normally, if you want a mouse that lacks two genes, you make each knockout seperately, then breed them to get a double knockout. Second, some of those genes are the ones necessary for the body to recognize that a cell is infected with a virus or has become cancerous. Probably not a good idea to get rid of them.

Another point made is that this could bypass the moral issues surrounding therapeutic cloning, by allowing us to use the exsisting lines. However, these lines will not last forever, they are only good for a few passages, so the supply is quite limited. You still have a supply problem. The basic science aspect is great; I can think of three or four experiments I'd like to do with the technology right off the top of my head....

more details

[gene_tailor]

The scientific article about this is published in Nature Biotechnology. The abstract is available here [nature.com] and if you have a subscription you can access the full text...

This is the same basic technique that has been used to make knock-out mice, but apparently a lot of tweaking was necessary because the protocol used with mouse ES cells works very poorly with human ES cells. It sounds like this article is basically a proof-of-concept to share the method with other scientists.

Stem Cell Line Viability

[ktulus cry]

I don't know if the same can be done for stem cells, but human fibroblast cell lines are made 'immortal' by knocking out the rb gene, I believe. The become pseudo-cancer cells, and proliferate as long as you need them to, minus the uncontrolled growth of cancer cells. They're really handy to use as a control in squamous cell carcinoma research. Anyone have any idea if something similar could be done in stem cells? Or would that compromise other cell functions too much?

Re:Stem Cell Line Viability

[robslimo]

My understanding is that, in an organism, removing the RB gene causes the retinoblastoma cells do continue to divide uncontrolled such that they do cause tumors. The term 'immortal' is a stretch that (I think) scientists chose more for hype than accuracy. It's only related to mortality in reference to the normal senescence mechanisms which cause cells to stop replicating after just so many divisions.

I think regulation of the senescence mechanisms, not removal of them, might be the answer to longevity.

Re:Stem Cell Line Viability

[Cryect]

Human cells can be made 'immortal' through several various cancer genes. The rb gene is just a growth control gene in regulating the cell phases from G1 to S. An example of another gene that can be altered for the same effect is the Ras gene. But one thing you need to keep in mind in stem cells they are already 'immortal' plus they want to keep stem cells as normal as possible. That is one of the largest problems with using cancerous cells is due to they are no longer normal but they do grow quite nicely. Anyways a major part of a cell being immortal is to have those nice telomerase genes be activated since that is what eventually kills non-stem cells (after every time you copy DNA you lose like 50 bases or so and the telomerase just keeps attaching them on after every time you copy but non-stem cells don't have telomerase(unless you are cancer)).

Re:Modify genes, don't knock 'em out

[robslimo]

As I understand it, many or most deseases are the result of misfunctioning genes, not genes that are superfluous and inherently counter-life.

For example, the symptoms of diseases similar to Alzheimer's are caused by 'prions' which are protiens that are too long and/or with an incorrect structure such that they fold strangely and tend to clump together between the cells in the brain, interfering with neural signalling. Some of these prions are [most likely all?] caused by genes which are the script to manufacture a needed protien but contains unnecessarily long repititions of alleles (repeating amino acid sequences) that result in malformed protiens.

It stands to reason that trimming out portions of these repeating sequences, as apposed to simplying zapping a whole gene, would result in the correct form of the desired protien. Could the techinique described in the article be applied in that manner? Too bad I'm not a subscriber to Nature.

At the risk of losing more karma [of arguable value anyway], I've reposted my message. It was moderated 'overrated'. The original message was not *rated* in any way... twas just a message. However, it is also an informed opinion; if one finds fault in the assertions above, please reply and set the me straight.