Characterization of Xenopus tissue inhibitor of metalloproteinases-2: a role in regulating matrix metalloproteinase activity during development.
BACKGROUND
Frog metamorphosis is totally dependent on thyroid hormone (T3) and mimics the postembryonic period around birth in mammals. It is an excellent model to study the molecular basis of postembryonic development in vertebrate. We and others have shown that many, if not all, matrix metalloproteinases (MMPs), which cleave proteins of the extracellular matrix as well as other substrates, are induced by T3 and important for metamorphosis. MMP activity can be inhibited by tissue inhibitors of metalloproteinase (TIMPs). There are 4 TIMPs in vertebrates and their roles in postembryonic development are poorly studied.


RESULTS
We analyzed the TIMP2 genes in Xenopus laevis and the highly related species Xenopus tropicalis and discovered that TIMP2 is a single copy gene in Xenopus tropicalis as in mammals but is duplicated in Xenopus laevis. Furthermore, the TIMP2 locus in Xenopus tropicalis genome is different from that in human, suggesting an evolutionary reorganization of the locus. More importantly, we found that the duplicated TIMP2 genes were similarly regulated in the developing limb, remodeling intestine, resorbing tail during metamorphosis. Unexpectedly, like its MMP target genes, the TIMP2 genes were upregulated by T3 during both natural and T3-induced metamorphosis.


CONCLUSIONS
Our results indicate that TIMP2 is highly conserved among vertebrates and that the TIMP2 locus underwent a chromosomal reorganization during evolution. Furthermore, the unexpected upregulation of TIMP2 genes during metamorphosis suggests that proper balance of MMP activity is important for metamorphosis.
Section on Molecular Morphogenesis, Program in Cellular Regulation and Metabolism (PCRM), Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America.
Liezhen
L
Fu
Guihong
G
Sun
Maria
M
Fiorentino
Yun-Bo
YB
Shi
D000595:Amino Acid Sequence; D000818:Animals; D020440:Gene Duplication; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D056426:Genetic Loci / Q000235:genetics; D006801:Humans; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D008675:Metamorphosis, Biological / Q000187:drug effects; D008969:Molecular Sequence Data; D009928:Organ Specificity; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014284:Triiodothyronine / Q000494:pharmacology; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014982:Xenopus laevis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*
D029867:Xenopus Proteins; D014284:Triiodothyronine; D019716:Tissue Inhibitor of Metalloproteinase-2; D020782:Matrix Metalloproteinases