Msx-1 Acts as a Regulator for Blastema Growth

초록

Msx-1 is known to regulate ectoderm-mesenchyme and mesenchyme-mesenchyme tissue interactions in the developing vertebrate limb bud. In this study, the spatial and temporal expression pattern of Msx-1 in the regenerating limbs of axolotls (Ambystoma mexicanum) was examined by whole mount in Situ hybridization and RT-PCR. In addition, the effects of retinoic acid (RA) and denervation. on the Msx-1 expression were examined as well. In the regenerating normal limbs, the weak expression of Msx-1 was detected in the mesenchymal cells under the apical ectodermal cap. From the early bud stage, the elevated level of Msx-1 expression was maintained until the early digit stage. However, Msx-1 expression was rapidly declined by the completion of regeneration. Compared to the normal limb regeneration, Msx-1 expression in RA treated limb regenerates was low until 9 days after RA treatment but increased during blastema growth period both in the lower and the upper arm regenerates. These results suggest that the Msx-1 regulates the proliferation and growth of blastema cells, and its expression may not be responsible for the dedifferentiation process. On the other hand, high level of Msx-1 expression was noted in the limb stump tissue after denervation. This result indicates that Msx-1 is also related to the regression of denervated mature tissue.

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