Bone morphogenetic protein dominantly suppresses epidermal growth factor-induced proliferative expansion of adult forebrain neural precursors

Abstract

A single asymmetric division by an adult neural stem cell (NSC) ultimately generates dozens of differentiated progeny, a feat made possible by the proliferative expansion of transit-amplifying progenitor cells (TAPs). Although NSC activation and TAP expansion is determined by pro- and anti-proliferative signals found within the niche, remarkably little is known about how these cells integrate simultaneous conflicting signals. We investigated this question focusing on the subventricular zone (SVZ) niche of the adult murine forebrain. Using primary cultures of SVZ cells, we demonstrate that Epidermal Growth Factor (EGF) and Bone Morphogenetic Protein (BMP)-2 are particularly powerful pro- and anti-proliferative factors for SVZ-derived neural precursors. Dose-response experiments showed that when simultaneously exposed to both signals, BMP dominantly suppressed EGF-induced proliferation; moreover, this dominance extended to all parameters of neural precursor behavior tested, including inhibition of proliferation, modulation of cell cycle, promotion of differentiation, and increase of cell death. BMP's anti-proliferative effect did not involve inhibition of mTORC1 or ERK signaling, key mediators of EGF-induced proliferation, and had distinct stage-specific consequences, promoting TAP differentiation but NSC quiescence. In line with these in vitro data, in vivo experiments showed that exogenous BMP limits EGF-induced proliferation of TAPs while inhibition of BMP-SMAD signaling promotes activation of quiescent NSCs. These findings clarify the stage-specific effects of BMPs on SVZ neural precursors, and support a hierarchical model in which the anti-proliferative effects of BMP dominate over EGF proliferation signaling to constitutively drive TAP differentiation and NSC quiescence.

Enhanced lysosomal degradation maintains the quiescent state of neural stem cells

“…5b). mTORC1 is involved in downstream EGF signaling in neural progenitor cells 35,36 . To verify the involvement of TFEB in cell proliferation, we analyzed phospho-deficient mutants of TFEB, TFEB S141A (mt1), and TFEB S210A (mt2), which are constitutively active.…”

Genetic targeting of neurogenic precursors in the adult forebrain ventricular epithelium

“…Electroporation Adult brain electroporation was conducted as previously described (Barnabe-Heider et al, 2008;Hamilton et al, 2015;Joppe et al, 2015). Plasmids (Table 1) were amplified by using an endotoxin-free 40-min Fast Plasmid Maxiprep Kit (Biotool), and then purified and concentrated by ethanol precipitation.…”

“…Neurosphere assays Neurosphere cultures were generated from adult mouse striatum using 20 ng/ml EGF (Sigma-Aldrich) and a protocol based on Reynolds and Weiss (1992) as detailed previously (Bouab et al, 2011;Hamilton et al, 2015;Joppe et al, 2015). Cells were fed each week with EGF and B27 (2%; Invitrogen).…”

Adult Neurogenesis in the Songbird: Region-Specific Contributions of New Neurons to Behavioral Plasticity and Stability

“…During both critical periods, numerous factors increase new neuron numbers, 'rescuing' new neurons that would otherwise have died [Shors, 2008;Anderson et al, 2011;Curlik and Shors, 2011;Waddell et al, 2011]. At a mechanistic level, factors that rescue new neurons include neurotrophins such as BDNF [Alvarez-Borda et al, 2004], testosterone and its metabolites [Rasika et al, 1999;Yamamura et al, 2011;Alward et al, 2016] and other growth factors [Alshammari et al, 2015;Joppe et al, 2015;Bakos et al, 2016]. At a behavioral level, neuronal lifespan is influenced by exercise [van Praag et al, 1999;van Praag, 2008], stress [Gould et al, 1997], sleep [Guzman-Marin et al, 2005], social conditions [Lipkind et al, 2002;Alward et al, 2014;Holmes, 2016], learning [Shors et al, 2001[Shors et al, , 2002, and use of the brain region in the absence of learning [Li et al, 2000;Pytte et al, 2010].…”