title: ASPM and CITK regulate spindle orientation by affecting the dynamics of astral microtubules.
abstract: Correct orientation of cell division is considered an important factor for the achievement of normal brain size, as mutations in genes that affect this process are among the leading causes of microcephaly. Abnormal spindle orientation is associated with reduction of the neuronal progenitor symmetric divisions, premature cell cycle exit, and reduced neurogenesis. This mechanism has been involved in microcephaly resulting from mutation of ASPM, the most frequently affected gene in autosomal recessive human primary microcephaly (MCPH), but it is presently unknown how ASPM regulates spindle orientation. In this report, we show that ASPM may control spindle positioning by interacting with citron kinase (CITK), a protein whose loss is also responsible for severe microcephaly in mammals. We show that the absence of CITK leads to abnormal spindle orientation in mammals and insects. In mouse cortical development, this phenotype correlates with increased production of basal progenitors. ASPM is required to recruit CITK at the spindle, and CITK overexpression rescues ASPM phenotype. ASPM and CITK affect the organization of astral microtubules (MT), and low doses of MT-stabilizing drug revert the spindle orientation phenotype produced by their knockdown. Finally, CITK regulates both astral-MT nucleation and stability. Our results provide a functional link between two established microcephaly proteins.
authors: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy marta.gai@unito.it ferdinando.dicunto@unito.it.
authors: Marta
authors: M
authors: Gai
authors: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors: Federico T
authors: FT
authors: Bianchi
authors: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors: Cristiana
authors: C
authors: Vagnoni
authors: Department of Biology and Biotechnologies "C. Darwin", Sapienza, Università di Roma, Rome, Italy.
authors: Fiammetta
authors: F
authors: Vernì
authors: Department of Biology and Biotechnologies "C. Darwin", Sapienza, Università di Roma, Rome, Italy.
authors: Silvia
authors: S
authors: Bonaccorsi
authors: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors: Selina
authors: S
authors: Pasquero
authors: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors: Gaia E
authors: GE
authors: Berto
authors: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors: Francesco
authors: F
authors: Sgrò
authors: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors: Alessandra Ma
authors: AM
authors: Chiotto
authors: Department of Medical Sciences, University of Turin, Turin, Italy.
authors: Laura
authors: L
authors: Annaratone
authors: Department of Medical Sciences, University of Turin, Turin, Italy.
authors: Anna
authors: A
authors: Sapino
authors: San Raffaele Rett Research Unit, Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy.
authors: Anna
authors: A
authors: Bergo
authors: San Raffaele Rett Research Unit, Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy.
authors: Nicoletta
authors: 0000-0003-0820-3155
authors: N
authors: Landsberger
authors: Leeds Institute of Biomedical and Clinical Sciences, University of Leeds, Leeds, UK.
authors: Jacqueline
authors: J
authors: Bond
authors: Max-Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
authors: Wieland B
authors: WB
authors: Huttner
authors: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy marta.gai@unito.it ferdinando.dicunto@unito.it.
authors: Ferdinando
authors: 0000-0001-9367-6357
authors: F
authors: Di Cunto
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004330:Drosophila; D000072159:Dynactin Complex / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D021381:Protein Transport; D034622:RNA Interference; D008941:Spindle Apparatus / Q000378:metabolism*
chemical_list: C512460:ASPM protein, mouse; D002148:Calmodulin-Binding Proteins; D000072159:Dynactin Complex; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; C115635:citron-kinase; D017346:Protein Serine-Threonine Kinases
keywords: astral microtubules; asymmetric division; microcephaly; mitotic spindle orientation; neurogenesis