EXPRESSION OF MSX-2 DURING DEVELOPMENT, REGENERATION, AND WOUND-HEALING IN AXOLOTL LIMBS

Msx genes are transcription factors that are expressed during embryoge nesis of developing appendages in regions of epithelial-mesenchymal in teractions. Various lines of evidence indicate that these genes functi on to maintain embryonic tissues in an undifferentiated, proliferative state. We have identified the axolotl homolog of Msx-2, and investiga ted its expression during limb development, limb regeneration, and wou nd healing. As in limb buds of higher vertebrates, axolotl Msx-2 is ex pressed in the apical epidermis and mesenchyme; however, its expressio n domain is more extensive, reflecting the broader region of the apica l epidermal cap in amphibians. Msx-2 expression is downregulated at la te stages of limb development, but is reexpressed within one hour afte r limb amputation. Msx-2 is also reexpressed during wound healing, and may be essential in the early stages of initiation of the limb regene ration cascade. (C) 1998 Wiley-Liss, Inc.