Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: jnorris235 on 22/06/2015 18:11:00
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We have 35 trillion cells in our body, I am led to believe. And maybe I have an aberration in my genes that lends itself to cancer, Hemophilia, or some such. So a chromosome is switched on or off, or a gene spliced in and the new DNA injected into me. How does that then change the other 34,999,999 cells DNA?
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A genetic change only directly affects the cells in which the change is made.
So if someone has a mitochondrial disease, this is easiest to correct while the whole person is just a single egg cell. Then when the egg cell grows into an adult, every cell in the body will contain the "new" mitochondria.
In some other conditions, there are just a few cells in the body that express a certain gene, so it is sufficient to just target this specific region of the body. For example, it has been demonstrated in pigs that it is possible to create a living pacemaker to correct a damaged heart, by converting a group of normal heart muscle cells into specialised pacemaker heart cells.
There are glands which produce hormones affecting the whole body; in principle, a defect in this hormone affecting the whole body could be corrected by just targeting the gland that produces the hormone. You don't even need to affect every cell in the gland - just enough to produce an improvement in the condition, and reduce levels of medication.
Genetic surgery on egg cells is controversial, because it doesn't just affect the individual, but potentially affects their descendents, too.
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Thank you. I think I have understood, and I think I heard you say the following.
Concerning adults: So to correct a defect which is manifesting itself from a certain place such as the pancreas, obviously it is not possible to change the DNA of one cell and expect that change to replicate itself around the body wherever it is needed, the change would have to be made to a bunch of pancreatic cells in order for the pancreas to perform more correctly and replace some of the cells in the pancreas (i.e. that already knew they were pancreas cells). Again those few corrected cells would not magically affect others and slowly take over, you'd have to do enough cells to get the required effect.
If some protein is being expressed wrongly (and I presume this defect would be present in every cell in the body) then as you say, find the cells that actually regulate this defect and therefor perform the function and replace as many as you can to reduce the medication need to as close to zero as you wish.
I think I was not taking into account that defects are only active at certain places, as the cells differentiate in their correct positions and jobs.
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This is not correct. A retrovirus (including the lentiviridae) introduces entirely new code into the genome of the entire organism. That is true of both you and your little dog, the flowers in your garden, and the deadly black mamba. If it has DNA, a retrovirus can insert a new sequence of DNA into it.
For example, how does the AIDS virus persist? It is a retrovirus.
The human genome contains several such retroviral sequences now. Perhaps your ability to read this is the result of them, who knows? That is how you make GMO foods only "natural".
"Gammaretroviral and lentiviral vectors for gene therapy have been developed that mediate stable genetic modification of treated cells by chromosomal integration of the transferred vector genomes. This technology is of use, not only for research purposes, but also for clinical gene therapy aiming at the long-term correction of genetic defects, e.g., in stem and progenitor cells. Retroviral vector particles with tropism for various target cells have been designed. Gammaretroviral and lentiviral vectors have so far been used in more than 300 clinical trials, addressing treatment options for various diseases.[1][9] Retro viral mutations can be developed to make transgenic mouse models to study various cancers and their metastatic models."
[Wikipedia."Retrovirus"]
And...
"Lentivirus is primarily a research tool used to introduce a gene product into in vitro systems or animal models. Large-scale collaborative efforts are underway to use lentiviruses to block the expression of a specific gene using RNA interference technology in high-throughput formats.[2] The expression of short-hairpin RNA (shRNA) reduces the expression of a specific gene, thus allowing researchers to examine the necessity and effects of a given gene in a model system. These studies can be a precursor to the development of novel drugs which aim to block a gene-product to treat diseases.
Another common application is to use a lentivirus to introduce a new gene into human or animal cells. For example, a model of mouse hemophilia is corrected by expressing wild-type platelet-factor VIII, the gene that is mutated in human hemophilia.[3] Lentiviral infection has advantages over other gene-therapy methods including high-efficiency infection of dividing and non-dividing cells, long-term stable expression of a transgene, and low immunogenicity. Lentiviruses have also been successfully used for transfection of diabetic mice with the gene encoding PDGF (platelet-derived growth factor),[4] a therapy being considered for use in humans. These treatments, like most current gene therapy experiments, show promise but are yet to be established as safe and effective in controlled human studies. Gammaretroviral and lentiviral vectors have so far been used in more than 300 clinical trials, addressing treatment options for various diseases.[5]
[Wikipedia."Lentivirus"]
[1.] Kurth, Reinhard; Bannert, Norbert, eds. (2010). Retroviruses: Molecular Biology, Genomics and Pathogenesis. Horizon Scientific. ISBN 978-1-904455-55-4.
[2.]http://www.sigmaaldrich.com/Area_of_Interest/Life_Science/Functional_Genomics_and_RNAi/shRNA.html
[3.] Shi Q, Wilcox DA, Fahs SA et al. (February 2007). "Lentivirus-mediated platelet-derived factor VIII gene therapy in murine haemophilia A". J. Thromb. Haemost. 5 (2): 352–61. doi:10.1111/j.1538-7836.2007.02346.x. PMID 17269937.
[4.] Lee JA, Conejero JA, Mason JM et al. (August 2005). "Lentiviral transfection with the PDGF-B gene improves diabetic wound healing". Plast. Reconstr. Surg. 116 (2): 532–8. doi:10.1097/01.prs.0000172892.78964.49. PMID 16079687.
[5.] Kurth, R; Bannert, N, ed. (2010). Retroviruses: Molecular Biology, Genomics and Pathogenesis. Caister Academic Press. ISBN 978-1-904455-55-4.
[9.] Desport, M, ed. (2010). Lentiviruses and Macrophages: Molecular and Cellular Interactions. Caister Academic. ISBN 978-1-904455-60-8.
PS: Speak of this only in scientific jargon and don't let the cat out of the bag because if the Baptist mullahs in South Carolina (and their ilk) get wise, there will be great rending of clothing and gnashing of teeth about infernal research and the tree of life.