Stem Cell, Where Do You Come From? (September 11, 2008)

Michael K. Richardson writing in today's Nature refers readers to a paper by Jill Helms and her colleagues at Stanford University: "graft[ing] stem cells from one bone into another to see whether they would help repair fractures in the 'wrong' location stem cells transplanted from leg bones into fractured jaws failed to produce new bone (P. Leucht et al. Development 135, 2845–2854; 2008). Interestingly, the uncooperative stem cells continued to express a gene, Hoxa11, that acts as a kind of embryonic 'postcode' for the leg.

"[This] validate[s] the concept of non-equivalence — that seemingly identical cells differ if they come from different places in the embryo... if some stem cells also have positional memory, doctors may need to make sure that they take stem cells from the right location to heal damaged tissues."