Matrix metalloproteinases mediate the dismantling of mesenchymal structures in the tadpole tail during thyroid hormone-induced tail resorption.
It has been suggested that a family of tissue remodelling enzymes called matrix metalloproteinases (MMPs) play a causal role in the process of tail resorption during thyroid hormone-induced metamorphosis of the anuran tadpole; however, this hypothesis has never been directly substantiated. We cloned two new Xenopus MMPs, gelatinase A (MMP-2) and MT3-MMP (MMP-16), and the MMP inhibitor TIMP-2. These clones were used along with several others to perform a comprehensive expression study. We show that all MMPs and TIMP-2 are dramatically induced in the resorbing tail during spontaneous metamorphosis and are spatially coexpressed, primarily in the remodelling mesenchymal tissues. By Northern blotting, we show that all the examined MMPs/TIMP-2 are also induced by treatment of organ-cultured tails with thyroid hormone (T(3)). Using the organ culture model, we provide the first direct evidence that MMPs are required for T(3)-induced tail resorption by showing that a synthetic inhibitor of MMP activity/expression can specifically retard the resorption process. By gelatin zymography, we also show T(3) induction of a fifth MMP, preliminarily identified as gelatinase B (GelB; MMP-9). Moreover, T(3) not only induces MMP/TIMP expression but also MMP activation, and we provide evidence that TIMP-2 participates in the latter process. These findings suggest that MMPs and TIMPs act in concert to effect the dismantling of mesenchymal structures during T(3)-induced metamorphic tadpole tail resorption.
Jung
Jae-Chang
JC
New England Eye Center, Tufts University School of Medicine, 750 Washington Street, Box 450, Boston, MA 02111, USA.
Leco
Kevin J
KJ
Edwards
Dylan R
DR
Fini
M Elizabeth
ME
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D003001:Cloning, Molecular; D017077:Culture Media, Conditioned / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D015151:Immunoblotting; D017403:In Situ Hybridization; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D053504:Matrix Metalloproteinases, Membrane-Associated; D008648:Mesoderm / Q000201:enzymology / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000235:genetics; D008969:Molecular Sequence Data; D009924:Organ Culture Techniques; D011233:Precipitin Tests; D017386:Sequence Homology, Amino Acid; D013963:Thyroid Hormones / Q000378:metabolism*; D013997:Time Factors; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000235:genetics; D014981:Xenopus; D014982:Xenopus laevis
D017077:Culture Media, Conditioned; D018076:DNA, Complementary; D013963:Thyroid Hormones; D019716:Tissue Inhibitor of Metalloproteinase-2; D020782:Matrix Metalloproteinases; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases