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Rossbach M.,Institute of Reconstructive Neurobiology
Current Molecular Medicine | Year: 2010

RNA interference (RNAi), an evolutionarily conserved sequence-specific post-transcriptional gene silencing mechanism, is triggered by double-stranded RNA (dsRNA) that results in the degradation of homologous mRNA or in the inhibition of mRNA translation. The naturally occurring triggers for the RNAi pathway are small regulatory RNAs, including small interfering RNAs (siRNAs), processed from longer dsRNAs by the RNAse III enzyme Dicer, and microRNAs (miRNAs), generated in a regulated multistep process from endogenous primary transcripts (pri-miRNA). These primary transcripts are capped, polyadenylated and spliced, thus resembling conventional mRNAs. It is estimated that miRNAs regulate more than one third of all cellular mRNAs, and bioinformatic data indicate that each miRNA can control hundreds of gene targets. Thus, there are likely to be few biological processes not regulated by miRNAs. Although the biological functions of miRNAs are not completely revealed, there is growing evidence that miRNA pathways are a new mechanism of gene regulation in both normal and diseased conditions. Recent evidence has shown that miRNA mutations or aberrant expression patterns correlate with various diseases, such as cancer, viral infections, cardiovascular or neurodegenerative diseases and indicates that miRNAs can function as tumor suppressors and oncogenes. MiRNAs have not only emerged as a powerful tool for gene regulation studies but also for the development of novel drugs. Since they do not encode proteins, they are not traditional therapeutic targets of small-molecule inhibitors and thus comprise a novel class of therapeutics. This article will focus on the current progress in drug discovery using the miRNA strategy. © 2010 Bentham Science Publishers Ltd.

PubMed | Ruhr University Bochum and Institute of Reconstructive Neurobiology
Type: Journal Article | Journal: Glia | Year: 2016

Chondroitin sulfate proteoglycans (CSPGs) have been proven to inhibit morphological maturation of oligodendrocytes as well as their myelination capabilities. Yet, it remained unclear, whether CSPGs and/or their respective chondroitin sulfate glycosaminoglycan (CS-GAG) side chains also regulate the oligodendrocyte lineage progression. Here, we initially show that CS-GAGs detected by the monoclonal antibody 473HD are expressed by primary rat NG2-positive oligodendrocyte precursor cells (OPCs) and O4-positive immature oligodendrocytes. CS-GAGs become down-regulated with ongoing oligodendrocyte differentiation. Enzymatic removal of the CS-GAG chains by the bacterial enzyme Chondroitinase ABC (ChABC) promoted spontaneous differentiation of proliferating rat OPCs toward O4-positive immature oligodendrocytes. Upon forced differentiation, the enzymatic removal of the CS-GAGs accelerated oligodendrocyte differentiation toward both MBP-positive and membrane forming oligodendrocytes. These processes were attenuated on enriched CSPG fractions, mainly consisting of Phosphacan/RPTP/ and to less extent of Brevican and NG2. To qualify CS-GAGs as universal regulators of oligodendrocyte biology, we finally tested the effect of CS-GAG removal on OPCs from different sources such as mouse cortical oligospheres, mouse spinal cord neurospheres, and most importantly human-induced pluripotent stem cell-derived radial glia-like neural precursor cells. For all culture systems used, we observed a similar inhibitory effect of CS-GAGs on oligodendrocyte differentiation. In conclusion, this study clearly suggests an important fundamental principle for complex CS-GAGs to regulate the oligodendrocyte lineage progression. Moreover, the use of ChABC in order to promote oligodendrocyte differentiation toward myelin gene expressing cells might be an applicable therapeutic option to enhance white matter repair.

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