CNS lesions stimulate adult neurogenic niches. Endogenous neural stem/progenitor cells represent a potential resource for CNS regeneration. Here, we investigate the response to unilateral focal laser-lesions applied to the visual cortex of juvenile rats. Within 3 days post-lesion, an ipsilateral increase of actively cycling cells was observed in cortical layer one and in the callosal white matter within the lesion penumbra. The cells expressed the neural stem/progenitor cell marker Nestin and the 473HD-epitope. Tissue prepared from the lesion area by micro-dissection generated self-renewing, multipotent neurospheres, while cells from the contralateral visual cortex did not. The newly formed neural stem/progenitor cells in the lesion zone might support neurogenesis, as suggested by the expression of Pax6 and Doublecortin, a marker of newborn neurons. We propose that focal laser-lesions may induce the emergence of stem/progenitor cells with neurogenic potential. This could underlie the beneficial effects of laser application in neurosurgery.

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Tenascin-C (Tnc) is an astrocytic multifunctional extracellular matrix (ECM) glycoprotein that potentially promotes or inhibits neurite outgrowth. To investigate its possible functions for retinal development, explants from embryonic day 18 (E18) rat retinas were cultivated on culture substrates composed of poly-d-lysine (PDL), or PDL additionally coated with Tnc or laminin (LN)-1, which significantly increased fiber length. When combined with LN, Tnc induced axon fasciculation that reduced the apparent number of outgrowing fibers. In order to circumscribe the stimulatory region, Tnc-derived fibronectin type III (TNfn) domains fused to the human Ig-Fc-fragment TNfnD6-Fc, TNfnBD-Fc, TNFnA1A2-Fc and TNfnA1D-Fc were studied. The fusion proteins TNfnBD-Fc and to a lesser degree TNfnA1D-Fc were stimulatory when compared with the Ig-Fc-fragment protein without insert. In contrast, the combination TNfnA1A2-Fc reduced fiber outgrowth beneath the values obtained for the Ig-Fc domain, indicating potential inhibitory properties. The monoclonal J1/tn2 antibody (clone 578) that is specific for domain TNfnD blocked the stimulatory properties of the TNfn-Fc fusions. When postnatal day 7 retinal ganglion cells were used rather that explants, Tnc and Tnc-derived proteins proved permissive for neurite outgrowth. The present study highlights a strong retinal axon growth-promoting activity of the Tnc domain TNfnD, which is modulated by neighboring domains.

The regulation of protein phosphorylation plays an essential role in virtually all aspects of eukaryotic development. Beginning with the regulation of the cell cycle to cellular proliferation and differentiation, the delicate balance between the phosphorylating activity of kinases and the dephosphorylation by phosphatases controls the outcome of many signal transduction cascades. The generation of cellular diversity occurs in an environment that is structured by the extracellular matrix (ECM) which forms a surrounding niche for stem and progenitor cells. Cell-cell and cell-matrix interactions elicit specific signaling pathways that control cellular behavior. In pathological situations such as neural degenerating diseases, gene expression patterns and finally the composition of the ECM change dramatically. This leads to changes of cell behavior and finally results in the failure of regeneration and functional restoration in the adult central nervous system. In order to study the roles of tyrosine phosphatases and ECM in this context, we analyzed the effects of laser-induced retinal injury on the regulation of the receptor protein tyrosine phosphatases (RPTP) RPTPBr7, Phogrin and RPTPbeta/zeta. The latter occurs in several isoforms, including the soluble released chondroitin sulfate proteoglycan phosphacan that is expressed in the developing retina. The receptor variants RPTPbeta/zeta(long) and RPTPbeta/zeta(short) may serve as receptors of tenascin-proteins and serve as modulators of cell intrinsic signaling in response to the ECM. Using quantitative real-time RT-PCR analysis, we show here a time-dependent pattern of gene expression of these molecules following laser lesions of the retina.

Protein tyrosine phosphatases (PTPs) are key regulators of different processes during development of the central nervous system. However, expression patterns and potential roles of PTPs in the developing superior colliculus remain poorly investigated. In this study, a degenerate primer-based reverse transcription-polymerase chain reaction (RT-PCR) approach was used to isolate seven different intracellular PTPs and nine different receptor-type PTPs (RPTPs) from embryonic E15 mouse superior colliculus. Subsequently, the expression patterns of 11 PTPs (TC-PTP, PTP1C, PTP1D, PTP-MEG2, PTP-PEST, RPTPJ, RPTPε, RPTPRR, RPTPσ, RPTPκ and RPTPγ) were further analyzed in detail in superior colliculus from embryonic E13 to postnatal P20 stages by quantitative real-time RT-PCR, Western blotting and immunohistochemistry. Each of the 11 PTPs exhibits distinct spatiotemporal regulation of mRNAs and proteins in the developing superior colliculus suggesting their versatile roles in genesis of neuronal and glial cells and retinocollicular topographic mapping. At E13, additional double-immunohistochemical analysis revealed the expression of PTPs in collicular nestin-positive neural progenitor cells and RC-2-immunoreactive radial glia cells, indicating the potential functional importance of PTPs in neurogenesis and gliogenesis.Electronic supplementary materialThe online version of this article (doi:10.1007/s00221-009-1963-6) contains supplementary material, which is available to authorized users.