The therapeutic promise of stem cells lies in the fact that they begin as undifferentiated cells, but can develop into any cell type in the body. Someday, doctors may be able to harness this process to grow replacement cells for patients who’ve lost tissues because of injury or disease.However, once a stem cell differentiates into a brain, heart, muscle or other body cell, there’s no turning back.Now, in experiments with mice, scientists believe they’ve discovered a new class of gene signals that either prevent or permit stem cells to develop into specific cell types, according to a report in the Feb. 24 issue of Nature.
