Functional implications for the microtubule-associated protein tau: localization in oligodendrocytes.

Abstract

We present evidence that the microtubuleassociated protein tau is present in oligodendrocytes (OLGs), the central nervous system cells that make myelin. By showing that tau is distributed in a pattern similar to that of myelin basic protein, our results suggest a possible involvement of tau in some aspect of myelination. Tau protein has been identified in OLGs in situ and in vitro. In interfascicular OLGs, tau localization, revealed by monoclonal antibody Tau-5, was confined to the cell somata. However, in cultured ovine OLGs with an exuberant network of processes, tau was detected in cell somata, cellular processes, and membrane expansions at the tips of these processes. Moreover, in such cultures, tau appeared localized adjacent to or coincident with myelin basic protein in membrane expansions along and at the ends of the cellular processes. The presence of tau mRNA was documented using fluorescence in situ hybridization. The distribution of the tau mRNA was similar to that of the tau protein.Western blot analysis of cultured OLGs showed the presence of many tau isoforms. Together, these results demonstrate that tau is a genuine oligodendrocyte protein and pave the way for determining its functional role in these cells.

Absence of Tau triggers age‐dependent sciatic nerve morphofunctional deficits and motor impairment

“…In line with previous studies demonstrating an absence of axonal deficits in neurons of Tau−/− animals (Yuan et al ., 2008; Vossel et al ., 2010), there were no differences in mRNA levels of transcription factors that critically regulate myelination process and/or maintenance, for example, Krox20 and Oct6 (data not shown), suggesting no gross changes in myelin gene regulation of Tau−/− Schwann cells. Furthermore, supporting the involvement of Tau and other cytoskeletal elements in myelination process, previous evidence suggests that Tau strongly colocalizes with MBP in distal tips of oligodendrocytes (LoPresti et al ., 1995; Muller et al ., 1997), suggesting that transportation and/or local MBP translation may require microtubule cytoskeleton and might be controlled by Tau–Fyn interaction (Klein et al ., 2002). As recent evidence suggests that Tau is responsible to locate Fyn in spines and Fyn has a well‐described role in myelination of both CNS and PNS (Kramer‐Albers & White, 2011), the above Tau–Fyn–MBP complex could be disrupted in the absence of Tau protein, affecting myelination signaling and process.…”

The effect of amphetamine analogs on cleaved microtubule-associated protein-tau formation in the rat brain

“…However, additional studies are necessary to determine whether C-tau immunoreactivity in astrocytes results either from C-tau of neuronal origin that is scavenged by astrocytes, leading to its localization within these cells or from C-tau isoforms that always reside within astrocytes. Although tau is usually associated with the axons of neurons, tau has also been shown to be present in glial cells (Bloom et al, 1984, LoPresti et al, 1995, Yoshiyama et al, 2003. Tau accumulation in glia is the result of increased synthesis or reduced clearance of the molecule that results in tau fibrillization and degeneration of the affected cells (Yoshiyama et al, 2003).…”

Expression of tau mRNA and soluble tau isoforms in affected and non‐affected brain areas in Alzheimer's disease

“…Since glial cells are largely the most abundant cell population in the white matter, it is probable that this PCR product results from the amplification of mRNAs present in astrocytes and/or oligodendrocytes. Rodent oligodendrocytes have been reported to express tau proteins [25] and cultured rat oligodendrocytes express both 3R and 4R tau mRNA [26]. Cultured astrocytes [27] and astrocytes in situ [28] express tau proteins.…”