title: The NuMA-related Mud protein binds Pins and regulates spindle orientation in Drosophila neuroblasts.
abstract: Asymmetric cell division generates cell diversity during development and regulates stem-cell self-renewal in Drosophila and mammals. In Drosophila, neuroblasts align their spindle with a cortical Partner of Inscuteable (Pins)-G alpha i crescent to divide asymmetrically, but the link between cortical polarity and the mitotic spindle is poorly understood. Here, we show that Pins directly binds, and coimmunoprecipitates with, the NuMA-related Mushroom body defect (Mud) protein. Pins recruits Mud to the neuroblast apical cortex, and Mud is also strongly localized to centrosome/spindle poles, in a similar way to NuMA. In mud mutants, cortical polarity is normal, but the metaphase spindle frequently fails to align with the cortical polarity axis. When spindle orientation is orthogonal to cell polarity, symmetric division occurs. We propose that Mud is a functional orthologue of mammalian NuMA and Caenorhabditis elegans Lin-5, and that Mud coordinates spindle orientation with cortical polarity to promote asymmetric cell division.
authors.affiliation: Institute of Molecular Biology, Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA.
authors.forename: Karsten H
authors.initials: KH
authors.lastname: Siller
authors.forename: Clemens
authors.initials: C
authors.lastname: Cabernard
authors.forename: Chris Q
authors.initials: CQ
authors.lastname: Doe
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear; D018797:Cell Cycle Proteins; D002455:Cell Division; D016764:Cell Polarity; D018385:Centrosome; D004330:Drosophila; D029721:Drosophila Proteins / Q000378:metabolism* / Q000502:physiology*; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism / Q000502:physiology*; D009474:Neurons / Q000166:cytology; D034521:Nuclear Matrix-Associated Proteins; D011485:Protein Binding; D008941:Spindle Apparatus
chemical_list: D034961:Antigens, Nuclear; D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D008565:Membrane Proteins; C411670:Mud protein, Drosophila; C050045:NUMA1 protein, human; D009419:Nerve Tissue Proteins; D034521:Nuclear Matrix-Associated Proteins; C405164:Pins protein, Drosophila