Identification and initial characterization of stathmin by the differential display method in nerve growth factor-treated PC12 cells

Department of Clinical Pathology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.

The differential display of mRNA is a new strategy to identify genes that are differentially expressed under altered conditions. We applied this method to determine differential gene expression in the rat pheochromocytoma cell line during differentiation induced by nerve growth factor (NGF). Three different mRNA species were isolated, and their differential expression was confirmed by RT-PCR. One of the mRNA species was identified as stathmin, a 19 kDa cytosolic protein attracting increasing interest for its role in signal transduction. In the NGF-treated PC12 cells, the expression of stathmin mRNA increased in a time-dependent manner, as assessed by northern blot analysis and RT-PCR. We also assessed by northern blot analysis how the expression of stathmin mRNA was altered in human pheochromocytomas (n = 5) compared with that in normal adrenal medulla tissue (n = 5). The mRNA concentrations were found to be significantly greater in the pheochromocytomas than in the normal tissues. It has been shown that stathmin mRNA concentrations are increased in various tumor cells. As pheochromocytomas are well-differentiated tumors of neural origin, it is not unexpected that stathmin mRNA is overexpressed in these tumors. Stathmin was isolated and identified as a differentially expressed gene by the differential display method in PC12 cells during differentiation induced by NGF. In addition, stathmin mRNA was found to be overexpressed in human pheochromocytomas. The mechanisms responsible for the up-regulation of stathmin mRNA during differentiation of PC12 cells and the significance of its overexpression in human pheochromocytomas remain to be determined.