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Monday, December 3, 2012

Correcting trisomy in cells

We’re all supposed to have two of each chromosome (unless you’re a boy, in which case you have one mismatched pair of sex chromosomes). Having three of one chromosome (trisomy) is usually lethal in uteru, but can sometimes only cause the kind of severe health and cognitive problems seen in people with Down syndrome (the result of having three chromosome 21s, shown below). What if we could pluck one of those extraneous chromosomes right out of a cell? Thanks to the work of researchers led by Li Li of the University of Washington, Seattle, we’re one step closer to that goal.

The researchers generated some induced pluripotent stem cells with trisomy 21. One of those three chromosome 21s was genetically engineered to include a gene that was detrimental to the cell under certain conditions. Thus, the scientists were able to put selective pressure on the cells to lose that extra copy of chromosome 21. This is precisely what happened. Three quarters of the surviving cells had shed the malignant chromosome.

Obviously, we’re still far from being able to remove every extra chromosome in a Down syndrome patient’s body. However, we may be able to modify this technique to remove chromosomes in a few critical cells and then reintroduce them back into the person’s body. In addition, we may be able to rid stem cell cultures of the trisomies that frequently plague them. Either way, this method will probably continue to be used by molecular biologists.

Li, L., Chang, K., Wang, P., Hirata, R., Papayannopoulou, T., & Russell, D. (2012). Trisomy Correction in Down Syndrome Induced Pluripotent Stem Cells Cell Stem Cell, 11 (5), 615-619 DOI: 10.1016/j.stem.2012.08.004