Hypoxia Induces the Tuftelin Gene (Brain and PC12) Via HIF1

Tuftelin is thought to play an important role during the development and mineralization of enamel. Our previous studies have shown that the tuftelin mRNA and protein are also expressed in various normal soft tissues, such as embryonic stem cells, peripheral nerve, brain and in several cancers. These data suggest that tuftelin may have a universal role and/or is multifunctional. Saarikoski et al (2002) showed that tuftelin was induced in vitro in different cancer cell lines during hypoxia. Objectives: of the present study was to examine the expression of the tuftelin gene in vivo in the mouse brain and in vitro in PC12 cell line, and the possible signaling pathway involved during hypoxia. Methods: Quantification of the tuftelin mRNA was performed using the real-time quantitative PCR (LightCycler, Roche). Mice were intra-peritoneal injected with CoCl2 (mimics hypoxia through HIF1 pathway in animals). To induce in-vitro oxygen deprivation, PC12 cells were introduced into a hypoxic device (1% oxygen) with normal DMEM medium. To check the possible tuftelin induction pathway during hypoxia (HIF1 or increasing cytosolic Ca2+ concentration), PC12 cells were pretreated with either Ca2+ free medium or chelethrine chloride (PKC inhibitor). Results: Tuftelin mRNA levels in the mouse brain and in PC12 cells increased significantly 12h and 12-24h respectively during hypoxia. Tuftelin was induced in the absence of extracellular Ca2+ as well as after inhibition of PKC during hypoxia. Conclusion: Our in vivo and in vitro experiments suggest that tuftelin is induced in hypoxia through HIF1 and not through cytosolic Ca2+ increase. Reduced oxygen tension was reported to be involved in mineralization of hard tissues. The present results and ongoing structural and functional studies will contribute to the understanding of the role of tuftelin in the normal, aging and diseased brain and possibly in cancer progression and in biomineralization of hard tissues. BSF-Grant-2003239