Differential functions of G protein and Baz-aPKC signaling pathways in Drosophila neuroblast asymmetric division.
Drosophila melanogaster neuroblasts (NBs) undergo asymmetric divisions during which cell-fate determinants localize asymmetrically, mitotic spindles orient along the apical-basal axis, and unequal-sized daughter cells appear. We identified here the first Drosophila mutant in the Ggamma1 subunit of heterotrimeric G protein, which produces Ggamma1 lacking its membrane anchor site and exhibits phenotypes identical to those of Gbeta13F, including abnormal spindle asymmetry and spindle orientation in NB divisions. This mutant fails to bind Gbeta13F to the membrane, indicating an essential role of cortical Ggamma1-Gbeta13F signaling in asymmetric divisions. In Ggamma1 and Gbeta13F mutant NBs, Pins-Galphai, which normally localize in the apical cortex, no longer distribute asymmetrically. However, the other apical components, Bazooka-atypical PKC-Par6-Inscuteable, still remain polarized and responsible for asymmetric Miranda localization, suggesting their dominant role in localizing cell-fate determinants. Further analysis of Gbetagamma and other mutants indicates a predominant role of Partner of Inscuteable-Galphai in spindle orientation. We thus suggest that the two apical signaling pathways have overlapping but different roles in asymmetric NB division.
Laboratory for Cell Asymmetry, Center for Developmental Biology, RIKEN, 2-2-3 Minatojima-Minamimachi, Chuou-ku, Kobe 650-0047, Japan.
Yasushi
Y
Izumi
Nao
N
Ohta
Asako
A
Itoh-Furuya
Naoyuki
N
Fuse
Fumio
F
Matsuzaki
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000502:physiology*; D016764:Cell Polarity; D048429:Cell Size; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000502:physiology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000378:metabolism; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009479:Neuropeptides; D017354:Point Mutation; D011493:Protein Kinase C / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D015290:Second Messenger Systems / Q000502:physiology*; D008941:Spindle Apparatus / Q000378:metabolism
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D029721:Drosophila Proteins; D044387:GTP-Binding Protein beta Subunits; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D046911:Macromolecular Substances; C107613:Mira protein, Drosophila; D009479:Neuropeptides; D021122:Protein Subunits; D011506:Proteins; C400774:baz protein, Drosophila; C098678:insc protein, Drosophila; D011493:Protein Kinase C; D043802:GTP-Binding Protein alpha Subunits, Gq-G11