Polarity orientation of microtubules in hippocampal neurons: uniformity in the axon and nonuniformity in the dendrite.

TLDR

Microtubules in axons are uniformly polarized, with plus ends pointing away from the cell body toward the growth cone. In dendrites, microtubule polarity is nonuniform in the mid‑region—equal numbers of plus ends face toward and away from the cell body—yet becomes uniformly directed toward the growth cone near the tip, indicating a structural basis for differential organelle distribution between axons and dendrites.

Abstract

We have analyzed the polarity orientation of microtubules in the axons and dendrites of cultured rat hippocampal neurons. As previously reported of axons from other neurons, microtubules in these axons are uniform with respect to polarity; (+)-ends are directed away from the cell body toward the growth cone. In sharp contrast, microtubules in the mid-region of the dendrite, approximately 75 microns from the cell body, are not of uniform polarity orientation. Roughly equal proportions of these microtubules are oriented with (+)-ends directed toward the growth cone and (+)-ends directed toward the cell body. At distances within 15 micron of the growth cone, however, microtubule polarity orientation in dendrites is similar to that in axons; (+)-ends are uniformly directed toward the growth cone. These findings indicate a clear difference between axons and dendrites with respect to microtubule organization, a difference that may underlie the differential distribution of organelles within the neuron.