Regulation of neural stem cells by the niche matrisome in Mus musculus\textit {Mus musculus}

In dieser Arbeit wurde der Einfluss des extrazellulären Matrixmoleküls Tenascin-C (Tnc) auf neurale Stammzellen während der Entwicklung und im adulten Organismus der Maus untersucht. Die adulten neuralen Stammzellen der subventrikulären Zone wurden per Videomikroskopie auf ihr Verhalten $\textit {in vitro}$ analysiert. Zellkulturen des Tnc-Knockouts (KO) deuteten hier auf eine reduzierte Stammzellzahl hin. Stammbaumanalysen der Stammzellen zeigten eine signifikant reduzierte Zellzyklusdauer bei den Tnc-defizienten Zellen im Vergleich zu wildtypischen Zellen. Die Migrationsstrecke der entstandenen Neuroblasten war signifikant erhöht, da die KO-Zellen über einen längeren Zeitraum migrierten als die Kontrollen. Auch die Präsentation der zwei Matrixmoleküle Laminin-1 und Tnc als Kultursubstrat hatte starken Einfluss auf den Zellteilungsablauf. Differenzierungs-Assays deuteten jedoch darauf hin, dass das Zellschicksal von beiden extrazellulären Matrixmolekülen nicht entscheidend verändert wurde

The extracellular matrix molecule tenascin-C modulates cell cycle progression and motility of adult neural stem/progenitor cells from the subependymal zone

Adult neurogenesis has been described in two canonical regions of the adult central nervous system (CNS) of rodents, the subgranular zone (SGZ) of the hippocampus and the subependymal zone (SEZ) of the lateral ventricles. The stem cell niche of the SEZ provides a privileged environment composed of a specialized extracellular matrix (ECM) that comprises the glycoproteins tenascin-C (Tnc) and laminin-1 (LN1). In the present study, we investigated the function of these ECM glycoproteins in the adult stem cell niche. Adult neural stem/progenitor cells (aNSPCs) of the SEZ were prepared from wild type $(Tnc^{+/+})$ and Tnc knockout $(Tnc^{-/-})$ mice and analyzed using molecular and cell biological approaches. A delayed maturation of aNSPCs in $Tnc^{−/−}$ tissue was reflected by a reduced capacity to form neurospheres in response to epidermal growth factor (EGF). To examine a potential influence of the ECM on cell proliferation, aNSPCs of both genotypes were studied by cell tracking using digital video microscopy. aNSPCs were cultivated on three different substrates, namely, poly-D-lysine (PDL) and PDL replenished with either LN1 or Tnc for up to 6 days in vitro. On each of the three substrates aNSPCs displayed lineage trees that could be investigated with regard to cell cycle length. The latter appeared reduced in $Tnc^{−/−}$ aNSPCs on PDL and LN1 substrates, less so on Tnc that seemed to compensate the absence of the ECM compound to some extent. Close inspection of the lineage trees revealed a subpopulation of late dividing $aNSPCs_{late}$ that engaged into cycling after a notable delay. $aNSPCs_{late}$ exhibited a clearly different morphology, with a larger cell body and conspicuous processes. $aNSPCs_{late}$ reiterated the reduction in cell cycle length on all substrates tested, which was not rescued on Tnc substrates. When the migratory activity of aNSPC-derived progeny was determined, $Tnc^{−/−}$ neuroblasts displayed significantly longer migration tracks. This was traced to an increased rate of migration episodes compared to the wild-type cells that rested for longer time periods. We conclude that Tnc intervenes in the proliferation of aNSPCs and modulates the motility of neuroblasts in the niche of the SEZ

Sulfation of glycosaminoglycans modulates the cell cycle of embryonic mouse spinal cord neural stem cells

In the developing spinal cord neural stem and progenitor cells (NSPCs) secrete and are surrounded by extracellular matrix (ECM) molecules that influence their lineage decisions. The chondroitin sulfate proteoglycan (CSPG) DSD-1-PG is an isoform of receptor protein tyrosine phosphatase-beta/zeta (RPTP$\beta$/$\zeta$), a $\it trans-$membrane receptor expressed by NSPCs. The chondroitin sulfate glycosaminoglycan chains are sulfated at distinct positions by sulfotransferases, thereby generating the distinct DSD-1-epitope that is recognized by the monoclonal antibody (mAb) 473HD. We detected the epitope, the critical enzymes and RPTP$\beta$/$\zeta$ in the developing spinal cord. To obtain insight into potential biological functions, we exposed spinal cord NSPCs to sodium chlorate. The reagent suppresses the sulfation of glycosaminoglycans, thereby erasing any sulfation code expressed by the glycosaminoglycan polymers. When NSPCs were treated with chlorate and cultivated in the presence of FGF2, their proliferation rate was clearly reduced, while NSPCs exposed to EGF were less affected. Time-lapse video microscopy and subsequent single-cell tracking revealed that pedigrees of NSPCs cultivated with FGF2 were strongly disrupted when sulfation was suppressed. Furthermore, the NSPCs displayed a protracted cell cycle length. We conclude that the inhibition of sulfation with sodium chlorate interferes with the FGF2-dependent cell cycle progression in spinal cord NSPCs