Project description:Stem cells are a potential key strategy for treating neurodegenerative diseases in which the generation of new neurons is critical. A better understanding of the characteristics and molecular properties of neural stem cells (NSC) and differentiated neurons can help in assessing neuronal maturity and possibly in devising better therapeutic strategies. We have therefore performed an in-depth gene expression profiling study of the C17.2 NSC line and primary neurons (PN) derived from embryonic mouse brains. Microarray analysis revealed a neuron-specific gene expression signature that distinguishes PN from NSCs, with elevated levels of transcripts involved in neuronal functions such as neurite development, axon guidance, in PN. The same comparison revealed decreased levels of multiple cytokine transcripts such as IFN, TNF, TGF, and IL. Among the differentially expressed genes, we found a statistically significant enrichment of genes in the ephrin, neurotrophin, CDK5 and actin pathways which control multiple neuronal-specific functions. Furthermore, genes involved in cell cycle were among the most significantly changed in PN. In order to better understand the role of cell cycle arrest in mediating NSCs differentiation, we blocked the cell cycle of NSCs with Mitomycin C (MMC) and examined cellular morphology and gene expression signatures. Although these MMC-treated NSCs displayed a neuronal morphology and expressed some neuronal differentiation marker genes, their gene expression patterns was very different from primary neurons. We conclude that: 1) Fully differentiated primary neurons display a specific neuronal gene expression signature; 2) cell-cycle block in NSC does not induce the formation of fully differentiated neurons; 3) Cytokines such as IFN, TNF, TGF and IL are part of normal NSC function and/or physiology; 4) Signaling pathways of ephrin, neurotrophin, CDK5 and actin, related to major neuronal features, are dynamically enriched in genes showing changes in expression level. Gene expression profiles in neuronal stem cell, mitomycin-treated neuronal stem cells and primary neuronal cultures were compared to examine cellular morphology and gene expression signatures during neuronal differentiation.

Project description:Congenital myasthenic syndromes (CMS) are a group of rare, inherited disorders characterised by compromised function of the neuromuscular junction (NMJ), manifesting with fatigable muscle weakness. Mutations in MYO9A were previously identified as causative for CMS but the precise pathomechanism remained to be characterised. Based on the role of MYO9A as a negative regulator of RhoA and an actin-based molecular motor, loss of MYO9A was hypothesised to affect the neuronal cytoskeleton, thus leading to impaired vesicular protein transport within the neuron. MYO9A-depleted NSC-34 cells (mouse motor neuron-derived cells) were used to assess the effect on the cytoskeleton revealing altered expression of a number of cytoskeletal proteins important for neuronal cell structure and intracellular transport. Based on these findings, the effect on vesicular protein transport was determined using a vesicular recycling assay revealing impaired recycling of neuronal relevant growth factor receptor. In addition, an unbiased approach utilising proteomic profiling of control and MYO9A-depleted NSC-34 cells was utilised to identify key players of the pathophysiology. Proteomic data support a role for defective vesicular transport and identified affected proteins which are also involved in the manifestation of other neuromuscular disorders. Prompted by the clear indication of perturbed protein transportation, further proteomics-based secretomic analysis of NSC-34 cells have been performed to identify whether secretion is similarly affected. Indeed, this led to the identification of a potential therapeutic target, agrin. Zebrafish lacking MYO9A orthologues (myo9aa/ab) were treated with "Agrin Biologic", an agrin compound, and amelioration of defects in neurite extension and in movement of the zebrafish was observed. Our combined data not only allow new insights into the pathophysiology of CMS and show that loss of MYO9A affects the neuronal cytoskeleton, leading to impaired transport and vesicular recycling of proteins, but on a more general note also represent a successful biomedical approach: from the identification of the underlying pathomechanism to the definition of a therapeutic intervention concept.

Project description:BACKGROUND: The polycomb group protein Ezh2 is an epigenetic repressor of transcription originally found to prevent untimely differentiation of pluripotent embryonic stem cells. We previously demonstrated that Ezh2 is also expressed in multipotent neural stem cells (NSCs). We showed that Ezh2 expression is downregulated during NSC differentiation into astrocytes or neurons. However, high levels of Ezh2 remained present in differentiating oligodendrocytes until myelinating. This study aimed to elucidate the target genes of Ezh2 in NSCs and in premyelinating oligodendrocytes (pOLs). METHODOLOGY/PRINCIPAL FINDINGS: We performed chromatin immunoprecipitation followed by high-throughput sequencing to detect the target genes of Ezh2 in NSCs and pOLs. We found 1532 target genes of Ezh2 in NSCs. During NSC differentiation, the occupancy of these genes by Ezh2 was alleviated. However, when the NSCs differentiated into oligodendrocytes, 393 of these genes remained targets of Ezh2. Analysis of the target genes indicated that the repressive activity of Ezh2 in NSCs concerns genes involved in stem cell maintenance, in cell cycle control and in preventing neural differentiation. Among the genes in pOLs that were still repressed by Ezh2 were most prominently those associated with neuronal and astrocytic committed cell lineages. Suppression of Ezh2 activity in NSCs caused loss of stem cell characteristics, blocked their proliferation and ultimately induced apoptosis. Suppression of Ezh2 activity in pOLs resulted in derangement of the oligodendrocytic phenotype, due to re-expression of neuronal and astrocytic genes, and ultimately in apoptosis. CONCLUSIONS/SIGNIFICANCE: Our data indicate that the epigenetic repressor Ezh2 in NSCs is crucial for proliferative activity and maintenance of neural stemness. During differentiation towards oligodendrocytes, Ezh2 repression continues particularly to suppress other neural fate choices. Ezh2 is completely downregulated during differentiation towards neurons and astrocytes allowing transcription of these differentiation programs. The specific fate choice towards astrocytes or neurons is apparently controlled by epigenetic regulators other than Ezh2. Examination of Ezh2 target sites in 2 different primary cells types

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