A team led by developmental biologist Professor Christophe Marcelle of Monash University in Australia has determined the mechanism that causes stem cells in the embryo to differentiate into specialized cells that form the skeletal muscles of animals’ bodies. The scientists published their results online in Nature on May 15, 2011. Scientists worldwide are racing to pin down the complex molecular processes that cause stem cells in the early embryo to differentiate into specialist cells such as muscle or nerve cells. The field has the potential to revolutionize medicine by delivering therapies to regenerate tissue damaged by disease or injury. Differentiation happens soon after fertilization, when embryonic cells are dividing rapidly and migrating as the animal’s body takes shape. Professor Marcelle’s team analyzed the differentiation of muscle stem cells in chicken embryos. The mechanisms in birds are identical to those in mammals, so the chick is a good model species for understanding the mechanisms in humans, says team member and the paper’s lead author Anne Rios. The scientists investigated the effect of a known signaling pathway called NOTCH on muscle differentiation. They found that differentiation of stem cells to muscle was initiated when NOTCH signalling proteins touched some of the cells. These proteins were carried by passing cells migrating from a different tissue–the neural crest–the progenitor tissue of sensory nerve cells. Muscle formation in the target stem cells occurred only when the NOTCH pathway was triggered briefly by the migrating neural crest cells. “This kiss-and-run activation of a pathway is a completely novel mechanism of stem cell specification which explains why only some stem cells adopt a muscle cell fate,” Ms. Rios said.
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