Although signal transducer and activator of transcription 3 (Stat3) plays crucial roles in the determination of neural stem cell (NSC) fate, Stat3 has multiple roles in NSC function Moreover, Stat3 plays important roles in neuronal survival and tumorigenesis. To investigate the overall effects of Stat3 on NSC fate, NSC were isolated from Stat3(flox/flox) mouse embryos (E14-15d), in which both Stat3 alleles are flanked by LoxP sites Isolated NSC was inoculated with an adenovirus vector expressing Cre recombinase (Ad nCre) or a control adenovirus vector expressing beta-galactosidase (Ad.nLz). Three days later, quantitative real-time PCR (qPCR) analysis revealed that treatment with Ad.nCre eliminated sun 3 mRNA expression in NSC Promoter assay confirmed that overexpression of nCre inhibited transactivation of acute responsive element (APRE) and blocked Stat3 function in NSC Moreover, Western blot analysis and immunocytochemical analysis revealed that elimination of Stat3 in NSC promoted neurogenesis and inhibited astrogliogenesis In addition, we investigated the effects of Stat3 elimination in NSC on the mRNA expression of Notch family members and bHLH factors Consequently, qPCR analysis showed that elimination of Stat3 in NSC promoted neurogenesis and inhibited astrogliogenesis through down-regulation of notch!, notch2 and hes5, but not hes1 mRNA expression (C) 2010 Elsevier Inc All rights reserved