ASSOCIATION OF POLY(A) MESSENGER-RNA WITH MICROTUBULES IN CULTURED NEURONS

The structural basis for the synthesis of specific proteins within dis tinct intraneuronal compartments is unknown. We studied the distributi on of poly(A) mRNA within cultured cerebrocortical neurons using high resolution in situ hybridization to identify cytoskeletal components t hat may anchor mRNA. After 1 day in culture, poly(A) mRNA was distribu ted throughout all of the initial neurites, including the axon-like pr ocess. At 4 days in culture, poly(A) mRNA was distributed throughout t he cell body and dendritic processes, but confined to the proximal seg ment of the axon. Poly(A) mRNA was bound to the cytoskeleton as demons trated by resistance to detergent extraction. Perturbation of microtub ules with colchicine resulted in a major reduction of dendritic poly(A ) mRNA; however, this distribution was unaffected by cytochalasin. Ult rastructural in situ hybridization revealed that poly(A) mRNA and asso ciated ribosomes were excluded from tightly bundled microtubules.