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Identification of genetic networks involved in the cell growth arrest and differentiation of a rat astrocyte cell line RCG‐12

The purpose of the present study is to establish and characterize a conditionally immortalized astrocyte cell line and to clarify the genetic networks responsible for the cell growth arrest and differentiation. A conditionally immortalized astrocyte cell line, RCG‐12, was established by infecting primary cultured rat cortical glia cells with a temperature‐sensitive simian virus 40 large T‐antigen. At a permissive temperature of 33°C, the large T‐antigen was expressed and cells grew continuously. On the other hand, the down‐regulation of T‐antigen at a non‐permissive temperature of 39°C led to growth arrest and differentiation. The cells expressed astrocyte‐expressed genes such as glial fibrillary acidic protein. Interestingly, the differentiated condition induced by the non‐permissive temperature significantly elevated the expression levels of several astrocyte‐expressed genes. To identify the detailed mechanisms by which non‐permissive temperature‐induced cell growth arrest and differentiation, we performed high‐density oligonucleotide microarray analysis and found that 556 out of 15,923 probe sets were differentially expressed 2.0‐fold. A computational gene network analysis revealed that a genetic network containing up‐regulated genes such as RB, NOTCH1, and CDKN1A was associated with the cellular growth and proliferation, and that a genetic network containing down‐regulated genes such as MYC, CCNB1, and IGF1 was associated with the cell cycle. The established cell line RCG‐12 retains some characteristics of astrocytes and should provide an excellent model for studies of astrocyte biology. The present results will also provide a basis for understanding the detailed molecular mechanisms of the growth arrest and differentiation of astrocytes. J. Cell. Biochem. 102: 1472–1485, 2007. © 2007 Wiley‐Liss, Inc.