EXPRESSION OF THE METASTASIS-ASSOCIATED MTS1 GENE DURING MOUSE DEVELOPMENT

The mts1 gene, a member of the S100 family, is specifically expressed in different metastatic tumor cell lines. After transfection in some n onmetastatic cell lines Mts1 can induce a metastatic phenotype, Mts1 p rotein can interact with non-muscle myosin, indicating that Mts1 plays a role in cell motility. In order to understand the function of this gene, we studied the expression of the mts1 mRNA and protein in vivo d uring mouse development, Both mRNA and protein were present in high co ncentrations from 12.5 to 18.5 days post coitum (dpc) in a variety of developing embryonic tissue of mesodermal origin, We found by double i mmunostaining with a macrophage-specific antibody that Mts1 protein wa s highly expressed in fetal macrophages throughout the embryonic mesen chyme and in macrophages colonizing developing lymphatic and non-lymph atic organs, Moreover, we found mts1 expression during differentiation and morphogenesis of mesenchymal tissues such as the mesenchyme surro unding the tips of digits, the mesenchyme underlying the epithelium of the bladder, and the mesenchyme between the primordia of the nasal ca psule and the skin as well as in the developing dermal papilla of hair and tooth follicle, In developing bone, Mts1 was expressed in invasiv e mesenchymal cells and in osteoclasts. The results presented here sug gest that Mts1 plays an important role in mouse development during dif ferentiation and function of macrophages and might be involved in diff erent processes associated with mesenchymal morphogenesis including me senchymal-epithelial interaction, tissue remodeling, and invasion. (C) 1997 Wiley-Liss, Inc.