Uniform TitleThe role of matrix metalloproteinases in zebrafish (danio rerio) embryogenesis and their regulation by glucocorticoids
NameHillegass, Jedd Michael (author), Cooper, Keith (chair), White, Lori (internal member), Gordon, Marion (internal member), Uzumcu, Mehmet (internal member), Moorman, Stephen (outside member), Rutgers University, Graduate School - New Brunswick,
DescriptionMatrix metalloproteinases (MMPs) play a pivotal role during development due to their ability to remodel the extracellular matrix, a function necessary for proper cellular migration and tissue morphogenesis. Studies have demonstrated that MMP gene expression can be either inhibited or induced by glucocorticoids in a variety of model systems and that exposure to glucocorticoids causes developmental abnormalities in several species. We hypothesize that glucocorticoid-induced teratogenesis is mediated through the glucocorticoid receptor (GR) and results from altering the expression and activity of the MMPs. Using the zebrafish (Danio rerio) as a model of development, the data presented here demonstrate that embryonic exposure to the glucocorticoids dexamethasone or hydrocortisone (100 mg/L) increased expression of the gelatinases MMP-2 (~1.5 fold) and MMP-9 (7.6 to 9.0-fold), and the collagenase MMP-13 (2.5 to 4.9-fold) at 72 hours post fertilization (hpf). In situ hybridization experiments confirmed these increases in MMP expression and demonstrated that the majority of transcript was localized rostrally. Enzyme activity was also increased at 72 hpf for both MMP-2 and MMP-9 (~3-fold), and MMP-13 (~13-fold) following glucocorticoid treatment, and substrate specificity was confirmed via several MMP inhibitors. Acute exposure to glucocorticoids resulted in numerous developmental abnormalities, most commonly altered craniofacial morphogenesis. Morpholino knockdown studies demonstrated that appropriate expression of MMP-2, MMP-9, and MMP-13 are necessary for proper zebrafish embryogenesis since morphants exhibited deleterious alterations in phenotype, and revealed that MMP-2 may compensate for loss of MMP-9 function. Co-treatment of zebrafish embryos with each glucocorticoid and the GR antagonist RU486 resulted in attenuation of glucocorticoid-induced increases in MMP expression (52-84% decrease) and activity (41-94% decrease), as well as a partial rescue in the abnormal craniofacial phenotypes. Taken collectively, these data show that dysregulation of MMP-2, MMP-9, and MMP-13 during embryogenesis, whether increased (as with glucocorticoids) or decreased (as with morpholinos), can lead to irregular developmental phenotypes. The teratogenic effects resulting from prolonged treatment with glucocorticoids may stem from this dysregulation of the MMPs. Finally, these results suggest that in the embryonic zebrafish, dexamethasone and hydrocortisone function through the GR, and that activation of this receptor can modulate MMP expression.
NoteIncludes bibliographical references (p. 135-152).
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.