Bifurcation and segmentation in regenerating limb

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Frog limbs show important characteristics in regeneration potency between newt with complete regeneration potency and mammals with no rgeneration potency. Froglets of Xenopus lexis rgenerate cartilage rod, spike, after amputaion of limbs. The spike was found to be an incomplete regenerate without bifurcation and segmentation. Furthermore, the spike has no muscle tissues.To induce bifurcation in the spike, we examined the expression of BMP. No expression of BMP gene in the spike was observed, and implantation of beads contraining BMP protein into the spike induced the segment formation in the cartilage. THe induction of segmentation was completely blocked by the addition of chordin, a BMP inhibitor. These results suggest that BMP play a role in the segmentation of regenerates.The frequency of spike formation with bifurcation increased by the implantation of SHH protein.To induce muscke formation in the spike, Muscle precursor cells were transplanted into the spike. Differentiation of muscle tissue was observed in the spike by the cells producing hepatocyte growth factor, an attractant of myogenic cells. These results suggest that the lack of muscle tissues in the spike can be restored at least partially.