A complex interplay between enzymes involved in extracellular matrix formation and their inhibitors is thought to control organogenesis during mammalian development. Disturbance of this balance may result in a wide range of diseases, including macular degeneration, arthritis, and tumor metastases. In order to define elements which may be involved in regulating human tissue inhibitor of metalloproteinase 3 (TIMP3) expression, we isolated and sequenced a clone containing 1315 bp of the 5Π-upstream region of the human TIMP-3-encoding gene. A 1.2 kb fragment of this clone, which contains multiple motifs which are binding sites for known transcription factors, was used to drive expression of the lacZ reporter gene in multiple lines of transgenic mice. TIMP3 promoter activity, detected through β€-galactosidase histochemical assay, was observed at high levels in selected tissues, the identity of which varied according to developmental stage. TIMP3 promoter activity was detected at embryonic and early postnatal stages in tissues undergoing extensive remodeling, such as developing somites, bones and joints, choroid plexus, webs between the digits, and the spongiotrophoblastic portion of the placenta. In adulthood, TIMP3 promoter activity was restricted to a few tissues which exhibit high metabolic activity or rapid turnover. These include the retinal pigment epithelium (RPE), cells of the kidney cortex, hair follicles, gingiva, ovarian follicles, and testis. The results suggest that TIMP3 expression plays an active role in developmental patterning and in the maintenance of specific differentiated tissues.