Aspm specifically maintains symmetric proliferative divisions of neuroepithelial cells

The ASPM (abnormal spindle-like microcephaly-associated) protein has previously been implicated in the determination of human cerebral cortical size, but the cell biological basis of this regulation has not been studied. Here we investigate the role of Aspm in mouse embryonic neuroepithelial (NE) cells, the primary stem and progenitor cells of the mammalian brain. Aspm was found to be concentrated at mitotic spindle poles of NE cells and to be down-regulated with their switch from proliferative to neurogenic divisions. Upon RNA interference in telencephalic NE cells, Aspm mRNA is reduced, mitotic spindle poles lack Aspm protein, and the cleavage plane of NE cells is less frequently oriented perpendicular to the ventricular surface of the neuroepithelium. The alteration in the cleavage plane orientation of NE cells increases the probability that these highly polarized cells undergo asymmetric division, i.e., that apical plasma membrane is inherited by only one of the daughter cells. Concomitant with the resulting increase in abventricular cells in the ventricular zone, a larger proportion of NE cell progeny is found in the neuronal layer, implying a reduction in the number of NE progenitor cells upon Aspm knock-down relative to control. Our results demonstrate that Aspm is crucial for maintaining a cleavage plane orientation that allows symmetric, proliferative divisions of NE cells during brain development. These data provide a cell biological explanation of the primary microcephaly observed in humans with mutations in ASPM, which also has implications for the evolution of mammalian brains.

[1]  C. Woods,et al.  Cytoskeletal genes regulating brain size. , 2006, Current opinion in cell biology.

[2]  Wieland B Huttner,et al.  Symmetric versus asymmetric cell division during neurogenesis in the developing vertebrate central nervous system. , 2005, Current opinion in cell biology.

[3]  M. Götz,et al.  Developmental cell biology: The cell biology of neurogenesis , 2005, Nature Reviews Molecular Cell Biology.

[4]  A. Hyman,et al.  A cytokinesis furrow is positioned by two consecutive signals , 2005, Nature.

[5]  Vladimir Larionov,et al.  The microcephaly ASPM gene is expressed in proliferating tissues and encodes for a mitotic spindle protein. , 2005, Human molecular genetics.

[6]  G. Pfeifer,et al.  The Abnormal Spindle-like, Microcephaly-associated (ASPM) Gene Encodes a Centrosomal Protein , 2005, Cell cycle.

[7]  W. Huttner,et al.  Selective Lengthening of the Cell Cycle in the Neurogenic Subpopulation of Neural Progenitor Cells during Mouse Brain Development , 2005, The Journal of Neuroscience.

[8]  C. Woods,et al.  Autosomal recessive primary microcephaly (MCPH): a review of clinical, molecular, and evolutionary findings. , 2005, American journal of human genetics.

[9]  C. Walsh,et al.  Mitotic Spindle Regulation by Nde1 Controls Cerebral Cortical Size , 2004, Neuron.

[10]  Masako Kawano,et al.  Asymmetric production of surface-dividing and non-surface-dividing cortical progenitor cells , 2004, Development.

[11]  A. Wynshaw-Boris,et al.  Lis1 and doublecortin function with dynein to mediate coupling of the nucleus to the centrosome in neuronal migration , 2004, The Journal of cell biology.

[12]  W. Huttner,et al.  Asymmetric distribution of the apical plasma membrane during neurogenic divisions of mammalian neuroepithelial cells , 2004, The EMBO journal.

[13]  Winfried Denk,et al.  Neurons arise in the basal neuroepithelium of the early mammalian telencephalon: a major site of neurogenesis. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[14]  A. Kriegstein,et al.  Cortical neurons arise in symmetric and asymmetric division zones and migrate through specific phases , 2004, Nature Neuroscience.

[15]  Jianzhi Zhang,et al.  Evolution of the human ASPM gene, a major determinant of brain size. , 2003, Genetics.

[16]  C. Walsh,et al.  Protein-truncating mutations in ASPM cause variable reduction in brain size. , 2003, American journal of human genetics.

[17]  A. Kriegstein,et al.  Radial glia diversity: A matter of cell fate , 2003, Glia.

[18]  W. Huttner,et al.  Tissue-specific RNA interference in postimplantation mouse embryos with endoribonuclease-prepared short interfering RNA , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[19]  Alexander F. Markham,et al.  ASPM is a major determinant of cerebral cortical size , 2002, Nature Genetics.

[20]  U. Schwaab,et al.  Murine calmodulin binding protein 1 (Calmbp1): tissue-specific expression during development and in adult tissues , 2002, Mechanisms of Development.

[21]  N. Osumi,et al.  Manipulating gene expressions by electroporation in the developing brain of mammalian embryos. , 2002, Differentiation; research in biological diversity.

[22]  S. Bonaccorsi,et al.  The Drosophila Protein Asp Is Involved in Microtubule Organization during Spindle Formation and Cytokinesis , 2001, The Journal of cell biology.

[23]  Alexey Khodjakov,et al.  Centrosome-independent mitotic spindle formation in vertebrates , 2000, Current Biology.

[24]  W. Huttner,et al.  Expression of the antiproliferative gene TIS21 at the onset of neurogenesis identifies single neuroepithelial cells that switch from proliferative to neuron-generating division. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[25]  D. Glover,et al.  Abnormal spindle protein, Asp, and the integrity of mitotic centrosomal microtubule organizing centers. , 1999, Science.

[26]  S. Mcconnell,et al.  Intrinsic Polarity of Mammalian Neuroepithelial Cells , 1998, Molecular and Cellular Neuroscience.

[27]  W. Huttner,et al.  Prominin, a novel microvilli-specific polytopic membrane protein of the apical surface of epithelial cells, is targeted to plasmalemmal protrusions of non-epithelial cells. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[28]  P. Raymond,et al.  Nonradioactive in Situ Hybridization on Cryosections , 1997, Microscopy Today.

[29]  Michael Brand,et al.  Asymmetric division and polarity of neuroepithelial cells , 1997, Current Opinion in Neurobiology.

[30]  P. Rakic.  A small step for the cell, a giant leap for mankind: a hypothesis of neocortical expansion during evolution , 1995, Trends in Neurosciences.

[31]  S. Mcconnell,et al.  Cleavage orientation and the asymmetric inheritance of notchl immunoreactivity in mammalian neurogenesis , 1995, Cell.

[32]  E. Karsenti,et al.  Orientation of spindle axis and distribution of plasma membrane proteins during cell division in polarized MDCKII cells , 1994, The Journal of cell biology.

[33]  J. Ávila,et al.  A cell division mutant of drosophila with a functionally abnormal spindle , 1985, Cell.