| 1. |
- Enarsson, Maria, et al.
(author)
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Extracellular signal-regulated protein kinase signaling is uncoupled from initial differentiation of central nervous system stem cells to neurons
- 2002
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In: Molecular Cancer Research. - 1541-7786 .- 1557-3125. ; 1:2, s. 147-154
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Journal article (peer-reviewed)abstract
- Knowledge about signaling pathways in response to external signals is needed to understand the regulation of stem cell proliferation and differentiation toward particular cell fates. The Ras/extracellular signal-regulated kinase (ERK) pathway has been suggested to play an essential role in neuronal differentiation. We have examined ERK signaling in the transition from multipotent stem cell to post-mitotic progeny using primary stem cells from the rat embryonic cortex. Fibroblast growth factor-2 (FGF-2) is a stem cell mitogen, whereas platelet-derived growth factor AA (PDGF-AA) expands a pool of committed neuronal precursors from stem cells. When comparing ERK activation by these growth factors, we found that FGF-2 stimulates high and PDGF-AA lower levels of ERK phosphorylation in stem cells. Differentiation was monitored as down-regulation of the bHLH transcription factor mammalian achaete-scute homologue-1 (MASH1). Even in the absence of active ERK, MASH1 became down-regulated and microtubule-associated protein 2-positive cells could form. Thus, ERK activation seems dispensable for the earliest steps of CNS stem cell differentiation.
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| 2. |
- Erlandsson, Anna, et al.
(author)
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Immature neurons from CNS stem cells proliferate in response toplatelet-derived growth factor
- 2001
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In: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 21:10, s. 3483-3491
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Journal article (peer-reviewed)abstract
- Identifying external signals involved in the regulation of neural stem cell proliferation and differentiation is fundamental to the understanding of CNS development. In this study we show that platelet-derived growth factor (PDGF) can act as a mitogen for neural precursor cells. Multipotent stem cells from developing CNS can be maintained in a proliferative state under serum-free conditions in the presence of fibroblast growth factor-2 (FGF2) and induced to differentiate into neurons, astrocytes, and oligodendrocytes on withdrawal of the mitogen. PDGF has been suggested to play a role during the differentiation into neurons. We have investigated the effect of PDGF on cultured stem cells from embryonic rat cortex. The PDGF alpha-receptor is constantly expressed during differentiation of neural stem cells but is phosphorylated only after PDGF-AA treatment. In contrast, the PDGF beta-receptor is hardly detectable in uncommitted cells, but its expression increases during differentiation. We show that PDGF stimulation leads to c-fos induction, 5'-bromo-2'deoxyuridine incorporation, and an increase in the number of immature cells stained with antibodies to neuronal markers. Our findings suggest that PDGF acts as a mitogen in the early phase of stem cell differentiation to expand the pool of immature neurons.
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