Down Syndrome’s Extra Chromosome Silenced in Lab Cells - Bloomberg
Scientists silenced the extra copy of a chromosome that causes Down syndrome in laboratory stem cells, offering the first evidence that it may be possible to correct the genes responsible for the disorder.
Down syndrome slows physical and intellectual development. About 6,000 babies are born every year with the condition, which is caused by an extra copy of chromosome 21.
While some genetic disorders have been easier to study because a single gene drives them, Down syndrome is more complex, said Robert Nussbaum, chief of genomic medicine at the University of California, San Francisco.
“It’s a technical tour-de-force,” Nussbaum said of the research. “We don’t really understand why the extra copy of chromosome 21 causes the problems it does. So this might allow us to have a thorough description of what goes wrong.”
The Science! The Xist Gene
In today’s paper, researchers led by Jeanne Lawrence, a professor of the department of cell and developmental biology at the University of Massachusetts Medical School, used a gene called Xist. The gene creates a regulating piece of RNA that ordinarily quiets the second X chromosome in women. In women, the extra RNA makes copies that coat the whole second X chromosome, preventing it from producing proteins. The scientists wondered if this quieting effect could be used specifically to silence the third copy of chromosome 21.
The scientists used skin cells from a Down syndrome patient that had been tricked into reverting into stem cells that, like embryonic ones, can grow into any type of tissue. Then they inserted a copy of Xist into the extra chromosome using technology from Richmond, California-based Sangamo.
Once inserted into the stem cells, scientists switched on Xist using the antibiotic tetracycline, setting off a process that effectively silenced the extra chromosome, Lawrence said.
When the chromosome had been silenced, the cells grew better in the culture, Lawrence said. What’s more, they saw an increased rate of formation of cells that are precursors to neurons.