Several developmental processes - for example, bicoid mRNA localisation during oogenesis and meiosis during germline development -involve special microtubule-organising centres (MTOCs). Now, on , Christiane Nüsslein-Volhard and colleagues propose that the cap structure of theγ-tubulin ring complex (γTuRC) is essential for the function of these special MTOCs. The γTuRC, which is required for microtubule nucleation, consists of a lockwasher-like structure and a globular cap. To study the function of the cap, the researchers analysed flies that contain mutations in the cap components Grip75 or Grip128. Animals with these mutations are viable but sterile, and their cells seem to containγTuRCs that nucleate the microtubules required for essential functions in somatic cells. By contrast, the distinct microtubules that are needed for bicoid mRNA localisation and germline meiosis do not form properly in the mutant flies. The researchers suggest, therefore, that Grip75 and Grip128 are needed to anchor the γTuRC at special MTOCs but are not essential for microtubule nucleation.
