Neurosphere

About: Neurosphere is a research topic. Over the lifetime, 5145 publications have been published within this topic receiving 321088 citations.

MELK-dependent FOXM1 phosphorylation is essential for proliferation of glioma stem cells.

Abstract: Glioblastoma multiforme (GBM) is a life-threatening brain tumor. Accumulating evidence suggests that eradication of glioma stem-like cells (GSCs) in GBM is essential to achieve cure. The transcription factor FOXM1 has recently gained attention as a master regulator of mitotic progression of cancer cells in various organs. Here, we demonstrate that FOXM1 forms a protein complex with the mitotic kinase MELK in GSCs, leading to phosphorylation and activation of FOXM1 in a MELK kinase-dependent manner. This MELK-dependent activation of FOXM1 results in a subsequent increase in mitotic regulatory genes in GSCs. MELK-driven FOXM1 activation is regulated by the binding and subsequent trans-phosphorylation of FOXM1 by another kinase PLK1. Using mouse neural progenitor cells (NPCs), we found that transgenic expression of FOXM1 enhances, while siRNA-mediated gene silencing diminishes neurosphere formation, suggesting that FOXM1 is required for NPC growth. During tumorigenesis, FOXM1 expression sequentially increases as cells progress from NPCs, to pretumorigenic progenitors and GSCs. The antibiotic Siomycin A disrupts MELK-mediated FOXM1 signaling with a greater sensitivity in GSC compared to neural stem cell. Treatment with the first-line chemotherapy agent for GBM, Temozolomide, paradoxically enriches for both FOXM1 (+) and MELK (+) cells in GBM cells, and addition of Siomycin A to Temozolomide treatment in mice harboring GSC-derived intracranial tumors enhances the effects of the latter. Collectively, our data indicate that FOXM1 signaling through its direct interaction with MELK regulates key mitotic genes in GSCs in a PLK1-dependent manner and thus, this protein complex is a potential therapeutic target for GBM.

Requirement for Foxd3 in the maintenance of neural crest progenitors

Abstract: Understanding the molecular mechanisms of stem cell maintenance is crucial for the ultimate goal of manipulating stem cells for the treatment of disease. Foxd3 is required early in mouse embryogenesis; Foxd3 -/- embryos fail around the time of implantation, cells of the inner cell mass cannot be maintained in vitro, and blastocyst-derived stem cell lines cannot be established. Here, we report that Foxd3 is required for maintenance of the multipotent mammalian neural crest. Using tissue-specific deletion of Foxd3 in the neural crest, we show that Foxd3flox/- ; Wnt1-Cre mice die perinatally with a catastrophic loss of neural crest-derived structures. Cranial neural crest tissues are either missing or severely reduced in size, the peripheral nervous system consists of reduced dorsal root ganglia and cranial nerves, and the entire gastrointestinal tract is devoid of neural crest derivatives. These results demonstrate a global role for this transcriptional repressor in all aspects of neural crest maintenance along the anterior-posterior axis, and establish an unprecedented molecular link between multiple divergent progenitor lineages of the mammalian embryo.

In vitro differentiation of size-sieved stem cells into electrically active neural cells

Abstract: Size-sieved stem (SS) cells isolated from human bone marrow and propagated in vitro are a population of cells with consistent marker typing, and can form bone, fat, and cartilage. In this experiment, we demonstrated that SS cells could be induced to differentiate into neural cells under experimental cell culture conditions. Five hours after exposure to antioxidant agents (beta-mercaptoethanol +/- retinoic acid) in serum-free conditions, SS cells expressed the protein for nestin, neuron-specific enolase (NSE), neuron-specific nuclear protein (NeuN), and neuron-specific tubulin-1 (TuJ-1), and the mRNA for NSE and Tau. Immunofluorescence showed that almost all the cells (>98%) expressed NeuN and TuJ-1. After 5 days of beta-mercaptoethanol treatment, the SS cells expressed neurofilament high protein but not mitogen-activated protein-2, glial filament acidic protein, and galactocerebroside. For such long-term-treated cells, voltage-sensitive ionic current could be detected by electrophysiological recording, and the intracellular calcium ion, Ca(2+), concentration can be elevated by high potassium (K(+)) buffer and glutamate. These findings suggest that SS cells may be an alternative source of undifferentiated cells for cell therapy and gene therapy in neural dysfunction.

Neurospheres: insights into neural stem cell biology.

Abstract: Neural stem cells (NSC) are a tissue-specific subtype of self-renewing and multipotent cells that can give rise to all neural populations. In this review, the importance of maintaining cell-cell contacts in the study of NSC is highlighted, and data obtained from some crucial single-cell studies is compared to results obtained from neurospheres, where aggregates of NSC are grown in suspension. In particular, results that indicate how this culture system may be well suited to analyze NSC plasticity, cell-cell, and cell-extracellular matrix (ECM) interactions are pointed out, and the hypothesis that cell-cell and cell-ECM contacts may be essential for NSC maintenance, survival, and proliferation is highlighted. Finally, it is suggested that neurospheres might play a role in the study of context-dependent behavior of NSC in niches by providing a system where NSC can be challenged chemically or biologically and analyzed in vitro, in a time- and context-dependent manner.