DEVELOPMENTAL EXPRESSION OF MMP-9 (GELATINASE-B) MESSENGER-RNA IN MOUSE EMBRYOS

Considerable remodeling of the extracellular matrix as well as cellula r migration takes place during embryogenesis. Since the metalloprotein ase MMP-9 is implicated in these functions in cancer cells, we studied the patterns of expression of MMP-9 mRNA during the development of po st-implantation mouse embryos. MMP-9 mRNA was detected using the ribon uclease protection assay in poly A + RNA from 13 to 17 day embryos, bu t not at 11 days, In order to localize these transcripts, in situ hybr idization was performed on sections of murine embryos from 7.5 to 15 d ays of gestation. At the time of implantation, MMP-9 mRNA was localize d to the invading trophoblast cells, Strong signals were also seen in the yolk sac, No signal for MMP-9 mRNA was seen by in situ hybridizati on in the embryo until day 11 when detectable reaction was seen in the central nervous system. By day 15 strong signals were seen in the liv er, in the developing bronchial epithelium of time lungs and in the pr imordial alveoli, in the epithelium of the thyroid gland, in the thymu s, in the endochondrial plates of the bone, and in neural cells. The l iver from day 15 embryos contained gelatinase activity at 105 kDa cons istent with MMP-9. Thus, MMP-9 expression appears to be expressed in s pecific organs in a precise temporal sequence during development. (C) 1995 Wiley-Liss, Inc.