Down Syndrome

Stem Cell Research

The neurological signs and symptoms of Down syndrome are recognized during the prenatal and early postnatal period in humans. Stem cell research offers the generation of human neural tissue in culture—a novel model system to study alterations in developmental disorders such as Down syndrome. An article published in the Lancet in 2002 described an intriguing model used to study Down syndrome, devised at the University of Cambridge by Bahn and Emson.

Every fetus begins as one cell, which then divides repeatedly. These cells are pluripotent, that is, they have the capability to differentiate into multiple lineages of cells, virtually giving rise to all the cells in the body. Embryonic stem cells are often collected at a developmental stage when they are just about to differentiate into a particular cell lineage.

Bahn and Emson used stem cells from the developing human brain that are precursors to neural tissue and grew them as spherical aggregates called neurospheres. They used neurospheres from postmortem fetuses (with and without Down syndrome) that were biochemically induced to form neurons. The RNA proteins were extracted from the neurospheres and compared with the RNA proteins from normal neurospheres. Through vigorous experimental procedures, it was found that one specific protein was absent from the neurospheres of Down syndrome patients. The SCG10 gene was relatively or absolutely functionally deficient. Further investigation discovered that certain other genes were also underexpressed; namely, LI, Synapsin, and β4-tubulin. The neurons from the defective stem cells were shorter, had misshapen axons, and fewer den—drites projected from the main body of the neuron when compared with the control.

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