Tenascins in CNS lesions.

The tenascin family of glycoproteins comprises four members in vertebrates, of which tenascin-C (Tnc) and tenascin-R (Tnr) are particularly important in the context of lesions in the central nervous system (CNS). Tnc is expressed in the developing CNS, before it is down-regulated and mainly restricted to the adult neural stem cell niches. It regulates numerous processes including differentiation, adhesion, migration and neurite outgrowth. These aspects are critical in the developing organism, but also after damage. Interestingly, Tnc is indeed re-expressed in the injured CNS. Additionally, Tnc is an activator of the immune response, another important aspect after lesion. Tnr is part of perineuronal nets, a specialized form of extracellular matrix that enwraps subtypes of neurons and limits synaptic plasticity. We summarize the role of tenascins in the context of stem cell niches, barrier formation, synaptic plasticity and immune response in the damaged mammalian CNS.