Down syndrome: the genetic defect corrected in human cells in culture

Publié le : 16 November 2012

The journal Cell Stem Cell dated 2 November 2012 reveals that "researchers from the Department of Medicine of Washington University have succeeded in correcting the genetic defect corresponding to Down syndrome." In concrete terms, "instead of a 21st pair of chromosomes, the trisomic cells have three chromosomes 21." The experiment carried out by a team of researchers led by Li B. "consisted of removing this additional chromosome." This is a "veritable exploit which makes it possible to obtain human cells cultivated in a laboratory with their extra chromosome 21 removed."             
To achieve this result, the team of researchers had recourse to "a classic adenovirus as the vector of a gene called TKNEO. The main difficulty was how to insert the gene into the right place. In this case, we had to aim at the gene called APP which is on the longest arm of chromosome 21. There the foreign gene, the transgene, has the affect of provoking in the receiver cell a selection reaction. To survive, it has to get rid of the chromosome 21 on which the TKNEO gene was grafted." David Russel, a researcher in haematology and genetics, said that "a key advantage of this technique for getting rid of the entire extra chromosome [is this]: Once it was gone, nothing was left behind. Gene therapy researchers have to be careful that their approaches do not cause gene toxicity."

While the team points out: “we are certainly not proposing that the method we describe would lead to a treatment for Down syndrome," the article recognises that "their success nevertheless constitutes a remarkable advance in the field of genetic therapy," a "very promising field but one where success has had to wait since the exploit that provided treatment for bubble babies (deprived of their immune system at birth).
From the research point of view, "the ability to generate stem cells with and without trisomy 21 from the same person could lead to better understanding of how problems tied to Down’s syndrome originate. … Researchers could contrast, for example how the two cell lines formed brain nerve cells, to learn the effects of trisomy 21 on neuron development, which might offer insights into the lifelong cognitive impairments and adulthood mental decline of Down syndrome.

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