Caspases and p53 modulate FOXO3A/Id1 signaling during mouse neural stem cell differentiation

iMed.UL, University of Lisbon, Portugal.
Journal of Cellular Biochemistry (Impact Factor: 3.37). 07/2009; 107(4):748-58. DOI: 10.1002/jcb.22172
Source: PubMed

ABSTRACT Neural stem cells (NSCs) differentiate into neurons and glia, and a large percentage undergoes apoptosis. The engagement and activity of apoptotic pathways may favor either cell death or differentiation. In addition, Akt represses differentiation by up-regulating the inhibitor of differentiation 1 (Id1), through phosphorylation of its repressor FOXO3A. The aim of this study was to investigate the potential cross-talk between apoptosis and proliferation during mouse NSC differentiation. We determined the time of neurogenesis and gliogenesis using neuronal beta-III tubulin and astroglial GFAP to confirm that both processes occurred at approximately 3 and 8 days, respectively. p-Akt, p-FOXO3A, and Id1 were significantly reduced throughout differentiation. Caspase-3 processing, p53 phosphorylation, and p53 transcriptional activation increased at 3 days of differentiation, with no evidence of apoptosis. Importantly, in cells exposed to the pancaspase inhibitor z-VAD.fmk, p-FOXO3A and Id1 were no longer down-regulated, p53 phosphorylation and transcriptional activation were reduced, while neurogenesis and gliogenesis were significantly delayed. The effect of siRNA-mediated silencing of p53 on FOXO3A/Id1 was similar to that of z-VAD.fmk only at 3 days of differentiation. Interestingly, caspase inhibition further increased the effect of p53 knockdown during neurogenesis. In conclusion, apoptosis-associated factors such as caspases and p53 temporally modulate FOXO3A/Id1 signaling and differentiation of mouse NSCs.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Reactive astrogliosis is one of the pathological hallmarks of neurodegenerative diseases. Inflammatory cytokines, such as TNF-α and IL-1β, have been shown to mediate the reactive astrogliosis in neurodegenerative diseases; however, the molecular mechanism remains unclear. In this study, we investigated the role of transcription factor FOXO3a on astrocyte proliferation, one primary aspect of severe reactive astrogliosis. Our results confirmed that TNF-α and IL-1β increased astrocyte proliferation, as determined by Ki67 and BrdU immunostaining. Furthermore, we found that cytokine-mediated astrocyte proliferation was accompanied by an increase of the phosphorylation and reduced nuclear expression of FOXO3a. Intracranial injection of TNF-α and IL-1β induced astrocyte proliferation and hypertrophy, which was associated with reduced nuclear expression of Foxo3a in astrocytes. To determine the function of FOXO3a in astrocyte proliferation, wild type FOXO3a was overexpressed with adenovirus, which subsequently upregulated p27Kip1 and Gadd45α, and significantly inhibited cytokine-induced astrocyte proliferation. In contrast, overexpression of dominant negative FOXO3a decreased p27Kip1, upregulated cyclin D1 and promoted astrocyte proliferation. Along the same line, astrocytes isolated from Foxo3a-null mice have higher proliferative potential. In response to intracranial injection of cytokines, Foxo3a-null mice manifested severe astrogliosis in vivo. In conclusion, FOXO3a is important in restraining astrocyte proliferation during proinflammatory cytokine stimulation and loss of function of FOXO3a may be responsible for the proliferation of astrocytes in the severe form of reactive astrogliosis. Understanding the key regulatory role of FOXO3a in reactive astrogliosis may provide a novel therapeutic target during neuroinflammation.
    Glia 04/2011; 59(4):641-54. DOI:10.1002/glia.21134 · 5.47 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Understanding the developmental mechanisms governing dopaminergic neuron generation and maintenance is crucial for the development of neuronal replacement therapeutic procedures, like in Parkinson's disease (PD), but also for research aimed at drug screening and pharmacology. In the present chapter, we review the present situation using stem cells of different origins (pluripotent and multipotent) and summarize current manipulations of stem cells for the enhancement of dopaminergic neuron generation, focusing on the actions of Bcl-X(L). Bcl-X(L) not only enhances dopaminergic neuron survival but also augments the expression of key developmental and maintenance genes, and, through the lengthening of the cell cycle early during differentiation, regulates cell fate decisions, producing a net enhancement of neurogenesis. The relevance of these findings is discussed in the context of basic neurogenesis and also for the development of efficient cell therapy in PD.
    Vitamins & Hormones 01/2011; 87:175-205. DOI:10.1016/B978-0-12-386015-6.00029-9 · 1.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Neuronal apoptosis sculpts the developing brain, and nearly all identified classes of neurons seem to be produced "in excess" during development. FoxO transcription factors regulate apoptosis in vitro in deprived of neurotrophins. It is unknown if FoxO3a is involved in the development of neurons. Here, we report a role of FoxO3a during neuronal development in zebrafish. By using in situ hybridization, we revealed that FoxO3a transcripts in zebrafish were gradually confined to regions of the central nervous system during embryonic development, including the forebrain, midbrain, midbrain-hindbrain boundary and hindbrain. By using FoxO3a morpholino antisense oligonucleotides, we observed that FoxO3a loss-of-function led to neural developmental defects, including increased neural apoptosis as detected by acridine orange and terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling. These defects could be partially rescued by the injection of FoxO3a mRNA. In this study, we found that FoxO3a loss-of-function resulted in the decreased expression of neuronal markers as determined by in situ hybridization and relative quantitative real-time PCR. Furthermore, the activation of FoxO3a was required for the maintenance of neuron survival but not necessary for the induction of neurogenesis. Our results indicated that FoxO3a might be essential for the maintenance of neural development in zebrafish. Therefore, this work provides novel evidence of FoxO3a in the embryonic neurodevelopment from zebrafish to other mammals.
    Neuroscience Letters 10/2010; 484(2):98-103. DOI:10.1016/j.neulet.2010.07.068 · 2.06 Impact Factor