Embryonic stem cells with identical genomes grow into distinctive tissues, such as heart, bone, and brain. At one time, scientists believed the differences among cell types arose from various sets of genes switched on inside developing cells. Then, studies showed that adult neurons uniquely lack a protein that permanently turns off neuronal genes in the rest of the body’s cells.
Now, it turns out that precursor nerve cells contain that same repressive protein after all. In fact, the protein directs the complex network of genes that transforms an embryonic stem cell into a mature nerve cell, say Howard Hughes Medical Institute (HHMI) researchers.

“A single protein does it all,” said Gail Mandel, HHMI investigator at the State University of New York at Stony Brook. “It keeps the genes totally off in non-neuronal tissues, such as skin, where you don’t dare express a neuronal gene. But it also allows the full elaboration of the neuronal phenotype from the precursor cell.”

Source [www.news-medical.net/?id=10301]