Purpose. Limb regeneration as it occurs in amphibians has two basic requirements: a source of multipotent cells capable of generating various tissues, and reorganization of those cells to form the one and only pattern of tissue appropriate to restore the missing parts. In the current biomedical world, there is much work dedicated to tissue engineering and to the differentiation of stem cells into various mature cell types. Neither of these approaches however, will by themselves succeed in regenerating a complex structure such as a limb. In our lab, we decided to focus on the pattern organization side of the equation by testing the potential of mammalian limb bud tissue to change its positional identity, and to manipulate that potential. Method. We used mouse embryos for our mammalian model. Small groups of cells were transplanted from one region of the limb bud into another, and the resulting effect on the positional identity of those cells was assessed using molecular markers of the upper arm, forearm and hand. We knocked out a genetic regulator of cell fate named
