Patronin/Shot Cortical Foci Assemble the Noncentrosomal Microtubule Array that Specifies the Drosophila Anterior-Posterior Axis

• Published in: Developmental cell 2016-07, Vol.38 (1), p.61-72
• Main Authors: Nashchekin, Dmitry, Fernandes, Artur Ribeiro, St Johnston, Daniel
• Format: Article
• Language: English
• Subjects: Animals; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - metabolism; Drosophila; Drosophila melanogaster - genetics; Drosophila melanogaster - growth & development; Drosophila melanogaster - metabolism; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Female; Glycogen Synthase Kinase 3 - genetics; Glycogen Synthase Kinase 3 - metabolism; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; Microtubules - metabolism; Oocytes - cytology; Oocytes - metabolism; Tubulin - genetics; Tubulin - metabolism
• ISSN: 1534-5807; 1878-1551
• DOI: 10.1016/j.devcel.2016.06.010

Noncentrosomal microtubules play an important role in polarizing differentiated cells, but little is known about how these microtubules are organized. Here we identify the spectraplakin, Short stop (Shot), as the cortical anchor for noncentrosomal microtubule organizing centers (ncMTOCs) in the Drosophila oocyte. Shot interacts with the cortex through its actin-binding domain and recruits the microtubule minus-end-binding protein, Patronin, to form cortical ncMTOCs. Shot/Patronin foci do not co-localize with γ-tubulin, suggesting that they do not nucleate new microtubules. Instead, they capture and stabilize existing microtubule minus ends, which then template new microtubule growth. Shot/Patronin foci are excluded from the oocyte posterior by the Par-1 polarity kinase to generate the polarized microtubule network that localizes axis determinants. Both proteins also accumulate apically in epithelial cells, where they are required for the formation of apical-basal microtubule arrays. Thus, Shot/Patronin ncMTOCs may provide a general mechanism for organizing noncentrosomal microtubules in differentiated cells. [Display omitted] •The Drosophila spectraplakin, Shot, recruits Patronin to form noncentrosomal MTOCs•The actin-binding domain of Shot anchors the ncMTOCs to the oocyte cortex•Par-1 excludes Shot from the posterior cortex to define the anterior-posterior axis•Shot/Patronin ncMTOCs lack γ-tubulin and grow MTs from stabilized minus-end stumps Many differentiated cell types lack centrosomes but still form highly polarized microtubule networks. Nashchekin et al. describe how the spectraplakin Shot and the microtubule minus-end-binding protein Patronin form a cortical noncentrosomal microtubule organizing center that acts a source of growing microtubules independently of γ-tubulin.