DEVELOPMENTAL EXPRESSION OF MOUSE STROMELYSIN-3 MESSENGER-RNA

We have used northern blot analysis and in situ hybridization to study the spatial distribution of stromelysin-3 (ST3) expression during mou se embryogenesis. ST3 mRNA was observed in trophoblastic cells at the site of embryonic implantation (7.5-8.5 days) and in a variety of deve loping embryonic tissues. In these tissues, the highest ST3 expression levels were observed during the development of the external features of limb, tail and snout, and during bone and spinal cord morphogenesis . In limb, tail and snout, ST3 expression was specifically detected in mesenchymal cells lining the basement membrane at the junction of pri mitive dermis and epidermis, and adjacent to epithelial cells undergoi ng proliferation and/or apoptosis. In bone, ST3 was expressed in invas ive mesenchymal cells and, in the spinal cord in neuroepithelial cells of the floor plate, at the time that this structure is crossed by com missural axons. Altogether, these observations suggest a role for ST3 during embryonic morphogenesis, in tissue remodeling processes associa ted with cell proliferation, death and/or invasion. Moreover, when com pared to urokinase and tissue plasminogen activators, the spatiotempor al pattern of ST3 expression shows some similarities, but was not comp letely superimposable, suggesting that these genes may cooperate in so me developing tissues and have specific functions in others.