| Abstract: | Background: The microtubule network, upon which transport occurs in higher cells, is formed by the polymerization of α and β tubulin. The third major tubulin isoform, γ tubulin, is believed to serve a role in organizing this network by nucleating microtubule growth on microtubule-organizing centers, such as the centrosome. Research in vitro has shown that γ tubulin must be restored to stripped centrioles to regenerate the centrosomal functions of duplication and microtubule nucleation.Results We have re-examined the localization of γ tubulin in isolated and in situ mammalian centrosomes using a novel immunocytochemical technique that preserves antigenicity and morphology while allowing increased accessibility. As expected, α tubulin was localized in cytoplasmic and centriolar barrel microtubules and in the associated pericentriolar material. Foci of γ tubulin were observed at the periphery of the organized pericentriolar material, as reported previously, often near the termini of microtubules. A further and major location of γ tubulin was a structure within the proximal end of the centriolar barrel. The distributions were complementary, in that α tubulin was excluded from the core of the centriole, and γ tubulin was excluded from the microtubule barrel.Conclusion We have shown that γ tubulin is localized both in the pericentriolar material and in the core of the mammalian centriole. This result suggests that γ tubulin has a role in the centriolar duplication process, perhaps as a template for growth of the centriolar microtubules, in addition to its established role in the nucleation of astral microtubules. |
