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Mental Table 1 was missing in the version of this article that Mental Table 1 was missing in the version of this article that was published as a Paper in Press on March 30, 2015. The supplemental table is now available. As part of a screen to identify novel genes that are induced by complement activation, we initially cloned Response Gene to Complement (RGC)-32 from rat oligodendrocytes by differential display (Badea et al., 1998). Human and mouse RGC-32 were subsequently cloned as well. RGC-32 expression has been detected in most tissues examined, and it has been found to be involved in cell cycle activation (Badea et al., 1998, 2002). RGC-32 forms a complex with cyclin B1/CDC2, thereby increasing its kinase activity (Badea et al., 2002). Overexpression in human aortic smooth muscle cells leads to S-phase and G2/M entry of unstimulated cells, and C5b-9 further increases the progression to G2/M (Badea et al., 2002). RGC-32 silencing in human aortic endothelial cells abolishes the DNA synthesis induced by C5b-9 and serum growth factors, indicating a requirement for RGC-32 activity for S-phase entry. RGC-32 siRNA-mediated knockdown also significantly reduces C5b-9induced CDC2 activation and Akt phosphorylation (Fosbrink et al., 2009). In addition, RGC-32 regulates the release of growth factors from these cells (Fosbrink et al., 2009) and is highly expressed by tumor cells. Taken together, these findings suggest that cell cycle induction by C5b-9 is RGC-32-dependent and that this process occurs in part through the regulation of Akt and growth factor release (Fosbrink et al., 2009). These observations using in vitro systems have indicated that RGC-32 may play an essential role in cell cycle proliferation. RGC-32 expression is also regulated by steroid hormones, IL-1, TGF-, and VEGF (An et al., 2009; Huang et al., 2009; Park et al., 2008; Vlaicu et al., 2008). An increased expression of RGC-32 has been found in peripheral blood mononuclear cells (PBMCs) and the CD14 cells of patients with hyperimmunoglobulin E (IgE) syndrome (Tanaka et al., 2005). In addition, increased levels of RGC-32 expression are found in the PBMCs and CD4 cells of patients with stable relapsing-remitting multiple sclerosis (MS), and their RGC-32 levels significantly decrease during relapses (Tegla et al., 2013). Thus far, little is known regarding the role of RGC-32 in cell cycle activation and the differentiation of T cells. To better understand the role of RGC-32 in cell proliferation, not only in cultured cells but also in complex organisms such as mice, we targeted the RGC-32 locus by homologous recombination in embryonic stem (ES) cells and generated a RGC-32 knockout mouse, testing its significance for cell cycle activation and its impact on mouse development. We further analyzed its role in cell cycle activation and the differentiation of T cells. Our data show that RGC-32 is involved in regulating the cell cycle activation by T-cell receptor/CD28 engagement in vivo, and this effect is mediated by IL-2 in a PI3K-dependent fashion.Exp Mol Pathol. Author manuscript; available in PMC 2016 October 12.Tegla et al.Page2. Materials and methods2.1. Construction of the targeting vector The RGC-32 genomic locus was isolated as a recombinant bacteriophage clone from a 129/Sv mouse genomic library using a mouse RGC-32 cDNA probe (Badea et al., 2002).