P. Litman et al., MICROTUBULES ARE INVOLVED IN THE LOCALIZATION OF TAU-MESSENGER-RNA INPRIMARY NEURONAL CELL-CULTURES, Neuron, 13(6), 1994, pp. 1463-1474
Subcellular localization of neuronal mRNAs contributes to the developm
ent of identifiable microdomains. In differentiated neurons, tau mRNA
is localized in the cell body and the proximal portion of the axon, an
d MAP2 mRNA is localized in the cell body and dendrites, whereas tubul
in mRNA is restricted to the cell body. To investigate the mechanism(s
) leading to segregation of mictrotubule-associated protein mRNA, we e
xamined the role of the cytoskeleton in this process. Detergent extrac
tion of primary neuronal cells in culture followed by in situ hybridiz
ation analysis demonstrated that tau mRNA remains bound to cytoskeleto
n of the treated cells. In addition, biochemical fractionation showed
that tau and MAP2 mRNAs are preferentially associated with the fractio
n of assembled microtubules. In contrast, mRNAs restricted to the neur
onal cell body, such as those of tubulin, the 68 kDa neurofilament, an
d mouse GAPDH, are preferentially found in the supernatant. Using cyto
skeletal inhibitors, we demonstrate that tau mRNA is associated with t
he microtubule system, and not with the actin filaments, thus supporti
ng the hypothesis that the mechanism of mRNA localization is a multist
ep pathway in which the microtubules play a crucial role.