Transcription factor RBP-J-mediated signaling represses the differentiation of neural stem cells into intermediate neural progenitors

Notch signaling is critical for multiple aspects of neurogenesis, but how it regulates the proliferation and differentiation of neural stem cells (NSCs) and intermediate neural progenitors (INPs) has not been well elucidated, especially in vivo. In this study, we conditionally ablated the transcription factor RBP-J, which mediates signalling from all four mammalian Notch receptors, in the basal forebrain and ventral midbrain using the RBP-J-floxed mouse and a newly established Nestin-Cre mouse. We found that at early stage neurogenesis (E11.5), the frequency of neurospheres increased significantly in the RBP-J-inactivated regions. The majority of the RBP-J deficient neurospheres were composed of INPs, suggesting the precocious differentiation of NSCs into INPs. Meanwhile, neuronal differentiation was reduced in the same regions at E11.5, inconsistent with the precocious differentiation phenotype in most Notch-related mutants. At late neurogenic stages (E17.5 and neonatal), as expected from precociously exhausted NSC pool, neurosphere frequency and NSCs decreased in the RBP-J-albated regions, accompanied by a significant increase of both neurons and glial cells. These results indicated that the RBP-J-mediated signaling might inhibit the differentiation of NSCS into INPs and support the generation of certain early born neurons at early neurogenic stages. (C); 2008 Elsevier Inc. All rights reserved.