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Team ‘cuts’ chromosome from Down syndrome cells

U. WASHINGTON (US) — Scientists have successfully removed the extra copy of chromosome 21 in cell cultures derived from a person with Down syndrome.

The cells of people with the condition contain three copies of chromosome 21 rather than the usual pair.

A triplicate of any chromosome is a serious genetic abnormality called a trisomy. Trisomies account for almost one-quarter of pregnancy loss from spontaneous miscarriages, according to the research team.


An image of the Down syndrome trisomy, showing an extra chromosome 21. (Credit: NIH via U. Washington)

In a report in Cell Stem Cell, a team led by Li B. Li of the University of Washington department of medicine describes how they corrected trisomy 21 in human cell lines they grew in the lab.

The targeted removal of a human trisomy, they note, could have both clinical and research applications.

In live births, Down syndrome is the most frequent trisomy. The condition has characteristic eye, facial, and hand features, and can cause many medical problems, including heart defects, impaired intellect, premature aging, and dementia, and certain forms of leukemia, a type of blood cancer.

Besides Down syndrome (trisomy 21), some other human trisomies are extra Y or X chromosomes and Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13), both of which have extremely high newborn fatality rates.

“We are certainly not proposing that the method we describe would lead to a treatment for Down syndrome,” says David W. Russell, professor of medicine and biochemistry and a senior scientist on the project. “What we are looking at is the possibility that medical scientists could create cell therapies for some of the blood-forming disorders that accompany Down syndrome.”

For example, he says, someday Down syndrome leukemia patients might have stem cells derived from their own cells, and have the trisomy corrected in these lab-cultured cells. They could then receive a transplant of their own stem cells—minus the extra chromosome—or healthy blood cells created from their fixed stem cells and that therefore don’t promote leukemia, as part of their cancer care.

He adds that 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 syndrome originate.

The cell lines would be genetically identical, except for the extra chromosome. 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. Similar comparative approaches could seek the underpinnings of untimely aging or defective heart tissue in this genetic condition.

The formation of trisomies is also a problem in regenerative medicine research using stem cells. Russell and his team observed that their approach could also be used to revert the unwanted trisomies that often arise in creating stem cell cultures.

Horizon Discovery and the National Institutes of Health supported the research. The researchers declared no financial conflicts of interest.

Source: University of Washington

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