Expression and localization of mRNA for the 16 KD subunit of V-ATPase in the rat embryo.

Vacuolar H(+)-ATPase (V-ATPase), an enzyme composed of multisubunits, is located in the membrane of intracellular organelles (e.g., lysosomes, and endosomes) and maintains the intraorganellar acidic pH by pumping protons across the membrane. Although there is growing evidence for some important role of V-ATPase in cell proliferation and differentiation, the functional significance of V-ATPase in vivo during mammalian development remains obscure. In the present study we investigated the expression and localization of mRNA for the 16 KD subunit of V-ATPase, an essential sector for enzymatic activity, in prenatal rat by Northern blot analysis and in situ hybridization with a specific oligonucleotide probe. With Northern blot analysis, consistent expression of the mRNA was observed in the embryos throughout the period examined (E14-E20). On in situ hybridization, mRNA signal was distributed with various intensities in both the epithelial and mesenchymal tissues at embryonic day 14 (E14). In E17 and E20 embryos, localization of strong signal became more restricted to distinct mesenchymal cells such as fibroblasts adjacent to the epithelia of skin, lung, and intestine, the cells of perichondrium, and myoblasts in the process of fusion. These results suggest that V-ATPase performs specific functions during the later stages of embryogenesis, especially at sites of mesenchymal differentiation and epithelium-mesenchyme interaction.