Destruction of a planarian's neoblasts, which occurs when scientists expose the animal to radiation in the laboratory, is devastating. "The animal will survive on the virtue of its differentiated cells," Sánchez Alvarado said, "but as the tissues begin to turn over and there are no stem cells to replace such tissues, the animal begins, basically, to fall apart." It degenerates in a very specific way, he explained, with the tip of the head beginning to regress, followed by a curling up of the sides of the body. Not surprisingly, worms without neoblasts also lose their ability to regenerate.
With their unparalleled capacity for regeneration and the many environmental cues that influence the division and differentiation of their neoblasts, Sánchez Alvarado considers planaria an excellent model to tease out the intricacies of adult stem cell biology. "I think they probably have a lot to teach us about how a population of stem cells is being regulated in vivo, rather than in a Petri dish," he said. So Sánchez Alvarado and his colleagues set out to understand exactly how neoblasts carry out the remarkable maintenance and recreation of the varied tissues that make up a flatworm.
Earlier this year, they got their first clues when they individually turned off 1,065 of the worm's genes, and found 240 that were involved in some aspect of regeneration. Importantly, Sánchez Alvarado noted, 85 percent of these genes are found in the genomes of other organisms, including humans. In the current study, the scientists zeroed in on o
Source:Howard Hughes Medical Institute