Down’s Syndrome Stem Cells Studied
Writing in the recent issue (January 26, 2002) of the British medical journal The Lancet, a team of scientists from the University of Cambridge, University College London, and the University of Wisconsin-Madison report findings from a genetic study based on stem cells derived from Down’s syndrome compared with normal fetal tissue.
The results illuminate some of the key cellular and molecular processes that give rise to Down’s syndrome, one of the most common causes of developmental disability in humans. The central finding of the study, according to Clive N. Svendsen, a UW-Madison professor of anatomy and neurology and coauthor of the report, is that serious deficits in specific genes in Down’s babies results in dramatic changes in the development of the cells that make up the early brain.
Most instances of Down’s syndrome, which affects nearly 350,000 people in the United States alone, results from an extra chromosome, chromosome 21, in the cells of those who have the condition. However, the precise genetic events that connect the extra chromosome to abnormal brain development of people with Down’s syndrome have not been understood.
“Until now, we have only had mouse models of Down’s syndrome, which have not been so faithful in reproducing all aspects of Down’s syndrome,” Svendsen says. “Now we have a complementary source of human stem cells with extra chromosome 21, and which can be grown indefinitely and used by a large number of scientists.” The study was made possible by advances that permit scientists to grow stem cells in culture, monitor gene activity within the cells, and observe the cells as they progress down the developmental pathway to becoming the cells that make up the human brain.
It was found that in the Down’s cells, there is a significant reduction in the percentage of cells that go on to form neurons compared with non-Down’s cells. Moreover, nerve fibers from the Down’s cells were shorter and misshapen.
Using techniques that permit scientists to see which genes are active in both a Down’s sample and a non-Down’s sample, the group was able to home in on some of the genes that seemed to be responsible.
“I think it is early in the game, but now we can work with a new model for Down’s syndrome which uses human cells rather than mouse cells,” says Svendsen. “If we can understand the loss of neurons in Down’s syndrome, I think it may lead to some novel treatments in the future.”
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