Between gestational day E12 and 18, about half of the mitotic neuronal cells die in embryonal mouse forebrain due to apoptosis. Studies with caspase knockout mice have demonstrated that apoptosis is necessary to prevent hyperproliferation of neuronal stem cells and subsequent, severe brain malformation. It is not known, however, which factors selectively induce or prevent apoptosis in individual, differentiating neuronal stem cells. We have shown for the first time, that the peak time of apoptosis in embryonal mouse brain (E14.5) is concurrent with elevation of endogenous ceramide and activation of caspase 3. We have also shown that the concentration of ceramide is high enough to kill neuronal progenitor cells grown in culture. From these observations, we propose that elevation of ceramide may be critical for induction of apoptosis in differentiating neuronal stem cells. Recently, several studies have reported that the ceramide-mediated formation of an inhibitory complex between PAR-4 and atypical PKC ,induces apoptosis. Our own studies with in vitro differentiated embryonic stem (ES) cells have shown that induction of apoptosis by ceramide is concurrent with up-regulation of PAR-4. We propose that PAR-4 is one of probably several pro-apoptotic proteins that induce apoptosis when their expression and that of ceramide is elevated. Our main hypothesis is that simultaneous upregulation of endogenous ceramide and ceramide-associated proteins (CAPs) results in formation of a pro-apoptotic protein complex (PAC) that triggers apoptosis in mitotic neuronal stem cells by suppression of anti-apoptotic, cell survival signaling. We will test this hypothesis in three Specific Aims using murine ES cells as model system.
In Specific Aim 1, we will test the hypothesis that up-regulation of ceramide induces apoptosis specifically in mitotic neuronal stem cells.
In Specific Aim 2, we will test the hypothesis that ceramide/CAP-induced PAC formation results in activation of caspases.
In Specific Aim 3, we will test the hypothesis that elevation of ceramide and down-regulation of cell survival signaling is synchronized by the cell cycle and growth factors. In conclusion, this study will identify mechanisms for regulation of apoptosis by ceramide that are critical for normal brain development and/or the etiology of subsequent, pathological disorders in adulthood.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Molecular, Cellular and Developmental Neurosciences 2 (MDCN)
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Owens, David F
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Georgia Health Sciences University
Internal Medicine/Medicine
Schools of Medicine
United States
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Elsherbini, Ahmed; Bieberich, Erhard (2018) Ceramide and Exosomes: A Novel Target in Cancer Biology and Therapy. Adv Cancer Res 140:121-154
Wang, Guanghu; Spassieva, Stefka D; Bieberich, Erhard (2018) Ceramide and S1P Signaling in Embryonic Stem Cell Differentiation. Methods Mol Biol 1697:153-171
Dinkins, Michael B; Wang, Guanghu; Bieberich, Erhard (2017) Sphingolipid-Enriched Extracellular Vesicles and Alzheimer's Disease: A Decade of Research. J Alzheimers Dis 60:757-768
Bieberich, Erhard (2012) Ceramide and sphingosine-1-phosphate signaling in embryonic stem cell differentiation. Methods Mol Biol 874:177-92
Bieberich, Erhard (2012) Introduction to the fractality principle of consciousness and the sentyon postulate. Cognit Comput 4:13-28
Bieberich, Erhard (2011) There is more to a lipid than just being a fat: sphingolipid-guided differentiation of oligodendroglial lineage from embryonic stem cells. Neurochem Res 36:1601-11
Bieberich, Erhard (2011) Lipid vesicle-mediated affinity chromatography using magnetic activated cell sorting (LIMACS): a novel method to analyze protein-lipid interaction. J Vis Exp :
Wang, Guanghu; Krishnamurthy, Kannan; Bieberich, Erhard (2009) Regulation of primary cilia formation by ceramide. J Lipid Res 50:2103-10
Wang, Guanghu; Krishnamurthy, Kannan; Umapathy, Nagavedi S et al. (2009) The carboxyl-terminal domain of atypical protein kinase Czeta binds to ceramide and regulates junction formation in epithelial cells. J Biol Chem 284:14469-75
Wang, Guanghu; Krishnamurthy, Kannan; Chiang, Ying-Wei et al. (2008) Regulation of neural progenitor cell motility by ceramide and potential implications for mouse brain development. J Neurochem 106:718-33

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