The learning and physical disabilities that affect people with Down syndrome may be due at least in part to defective stem cell regulation throughout the body, according to researchers at the Stanford University School of Medicine. (Agencies)
The defects in stem cell growth and self-renewal observed by the researchers can be alleviated by reducing the expression of just one gene on chromosome 21, they found.
Down syndrome is caused by an extra copy of chromosome 21. It causes both physical and cognitive problems.
The finding marks the first time Down syndrome has been linked to stem cells, and addresses some long-standing mysteries about the disorder. Although the gene, called Usp16, is unlikely to be the only contributor to the disease, the finding raises the possibility of an eventual therapy based on reducing its expression.
"There appear to be defects in stem cells in all the tissues that we tested, including the brain," said Michael Clarke, Stanford's Karel H and Avice N Beekhuis Professor in Cancer Biology. The researchers conducted their studies in both mouse and human cells.
"We believe Usp16 over expression is a major contributor to the neurological deficits seen in Down syndrome," he said.
While many of the physical issues, such as vulnerability to heart problems, can now be treated, no treatments exist for poor cognitive function.
The findings suggest answers to many long-standing mysteries about the condition, including why people with Down syndrome appear to age faster and exhibit early Alzheimer's disease.
According to co-author Craig Garner, the fact that people with Down syndrome have three copies of chromosome 21 and the
Usp16 gene accelerates the rate at which stem cells are used during early development, which likely exhausts stem cell pools and impairs tissue regeneration in adults with Down syndrome.
"As a result, their brains age faster and are susceptible to early onset neurodegenerative disorders," Garner said.
Other Stanford researchers involved in the work include postdoctoral scholars Shaheen Sikandar, Angera Kuo, and Marco Quarta; senior research scientist Siddhartha Mitra; and professor of cardiothoracic surgery and pediatrics Vadiyala Reddy, among various others. The study was published in the journal Nature.
The learning and physical disabilities that affect people with Down syndrome may be due at least in part to defective stem cell regulation throughout the body, according to researchers at the Stanford University School of Medicine.