Spatial and temporal expression profiles suggest the involvement of gelatinase A and membrane type 1 matrix metalloproteinase in amphibian metamorphosis.

The matrix metalloproteinases (MMPs) are a family of proteases capable of degrading various components of the extracellular matrix (ECM). Among them, the membrane type MMP-1 (MT1-MMP) has been shown to participate in the activation of MMP gelatinase A (GelA), suggesting that they may function together in development and pathogenesis. Here, we have investigated the spatiotemporal expression profiles of Xenopus laevis MT1-MMP and GelA genes during thyroid-hormone-dependent metamorphosis. We have focused our studies on two organs: (1) the intestine, which undergoes first the degeneration of the tadpole epithelium through apoptosis and then the development of adult epithelium and other tissues, and (2) the tail, which completely resorbs through programmed cell death. We show that both MT1-MMP and GelA are upregulated in the intestine and tail when both organs undergo metamorphosis. Within the organs, MT1-MMP and GelA are coexpressed in the connective tissues during both natural and thyroid-hormone-induced metamorphosis. In addition, MT1-MMP (but not GelA) is also expressed in the longitudinal muscle cells of the metamorphosing intestine. These results suggest that MT1-MMP and GelA function together in the ECM degradation or remodeling associated with metamorphosis and that MT1-MMP has additional GelA-independent roles in the development of adult longitudinal muscle in the intestine.