Mitotic Spindle Orientation in Asymmetric and Symmetric Cell Divisions during Animal Development

Asymmetric cell division (ACD) is believed to be a physiological event that occurs during development and tissue homeostasis in a large variety of organisms. ACD produces two unequal daughter cells, one of which resembles a multipotent stem and/or progenitor cell, whereas the other has potential for differentiation. Although recent studies have shown that the balance between self-renewal and differentiation potentials is precisely controlled and that alterations in the balance may lead to tumorigenesis in Drosophila neuroblasts, it is largely unknown whether human cancer cells directly show ACD in an evolutionarily conserved manner. Here, we show that the conserved polarity/spindle protein NuMA is preferentially localized to one side of the cell cortex during cell division, generating unequal inheritance of fate-altering molecules in human neuroblastoma cell lines. We also show that the cells with a single copy of MYCN showed significantly higher percentages of ACD than those with MYCN amplification. Moreover, suppression of MYCN in MYCN-amplified cells caused ACD, whereas expression of MYCN in MYCN-nonamplified cells enhanced symmetric cell division. Furthermore, we demonstrate that centrosome inheritance follows a definite rule in ACD: The daughter centrosome with younger mother centriole is inherited to the daughter cell with NuMA preferentially localized to the cell cortex, whereas the mother centrosome with the older mother centriole migrates to the other daughter cell. Thus, the mechanisms of cell division of ACD or symmetric cell division and centrosome inheritance are recapitulated in human cancer cells, and these findings may facilitate studies on cancer stem cells.

Section: Mitosis | Cd133mentioning

confidence: 99%

Section: Mitosis | Cd133mentioning

confidence: 99%

Evidence of asymmetric cell division and centrosome inheritance in human neuroblastoma cells

Izumi

Kaneko

2012

“…The position of the mitotic spindle is regulated by pulling forces acting between the spindle poles and cortical microtubule attachment sites (1,2). The spindle position determines the cleavage plane and thereby influences the size and position of the newly forming daughter cells (3,4). A defined spatial organization of newly generated cells is crucial for creating complex 3D structures such as tubes, ducts, and vessels (5,6).…”

mentioning

confidence: 99%

Analysis and modeling of mitotic spindle orientations in three dimensions

Jüschke

Xie

Postiglione

et al. 2013

The orientation of the mitotic spindle determines the relative size and position of the daughter cells and influences the asymmetric inheritance of localized cell fate determinants. The onset of mammalian neurogenesis, for example, coincides with changes in spindle orientation. To address the functional implications of this and related phenomena, precise methods for determining the orientation of the mitotic spindle in complex tissues are needed. Here, we present methodology for the analysis of spindle orientation in 3D. Our method allows statistical analysis and modeling of spindle orientation and involves two parameters for horizontal and vertical bias that can unambiguously describe the distribution of spindle orientations in an experimental sample. We find that 3D analysis leads to systematically different results from 2D analysis and, surprisingly, truly random spindle orientations do not result in equal numbers of horizontal and vertical orientations. We show that our method can describe the distribution of spindle orientation angles under different biological conditions. As an example of biological application we demonstrate that the adapter protein Inscuteable (mInsc) can actively promote vertical spindle orientation in apical progenitors during mouse neurogenesis.

“…During development, asymmetric divisions coordinate cell growth with cell specification to determine tissue morphogenesis, while in adult life they sustain tissue homeostasis and regeneration (1). In asymmetric divisions specific cortical landmarks instruct the orientation of the mitotic spindle to promote unequal partitioning of fate determinants in cellular systems as diverse as Caenorhabditis elegans zygotes, Drosophila neuroblasts, as well as vertebrate skin and neural progenitors (2).…”

mentioning

confidence: 99%

“…Based on its interaction with both Par3 and LGN, Insc has been considered the molecular link between cortical Par proteins and NuMA∶LGN∶Gαi GDP complexes. This notion is mainly substantiated by imaging analyses conducted in fly neuroblasts and mouse skin progenitors showing that during asymmetric metaphases Par3, Insc, LGN, and NuMA colocalyze in a cortical region underlying one of the spindle poles (1,6,12). However, no proof has been provided for the simultaneous association of LGN with Insc and NuMA, which remains a key question to elucidate how force generators work.…”

mentioning

confidence: 99%

Inscuteable and NuMA proteins bind competitively to Leu-Gly-Asn repeat-enriched protein (LGN) during asymmetric cell divisions

Culurgioni

Alfieri

Pendolino

et al. 2011

Coupling of spindle orientation to cellular polarity is a prerequisite for epithelial asymmetric cell divisions. The current view posits that the adaptor Inscuteable (Insc) bridges between Par3 and the spindle tethering machinery assembled on NuMA∶LGN∶Gαi GDP , thus triggering apico-basal spindle orientation. The crystal structure of the Drosophila ortholog of LGN (known as Pins) in complex with Insc reveals a modular interface contributed by evolutionary conserved residues. The structure also identifies a positively charged patch of LGN binding to an invariant EPE-motif present on both Insc and NuMA. In vitro competition assays indicate that Insc competes with NuMA for LGN binding, displaying a higher affinity, and that it is capable of opening the LGN conformational switch. The finding that Insc and NuMA are mutually exclusive interactors of LGN challenges the established model of force generators assembly, which we revise on the basis of the newly discovered biochemical properties of the intervening components.A symmetric cell divisions regulate the position and the fate choice of daughter cells, with impact on numerous phenotypes of multicellular organisms. During development, asymmetric divisions coordinate cell growth with cell specification to determine tissue morphogenesis, while in adult life they sustain tissue homeostasis and regeneration (1). In asymmetric divisions specific cortical landmarks instruct the orientation of the mitotic spindle to promote unequal partitioning of fate determinants in cellular systems as diverse as Caenorhabditis elegans zygotes, Drosophila neuroblasts, as well as vertebrate skin and neural progenitors (2). Spindle coupling to polarity cues involves the recruitment at cortical sites of molecular devices, known as force generators, whose main task is to capture astral microtubules emanating from the spindle poles and to establish pulling forces. Core components of force generators are the evolutionary conserved NuMA∶LGN∶Gαi complexes, termed Mud∶Pins∶Gαi in flies. Topologically, tetratricopeptide repeats (TPR) present in the N-terminal portion of LGN mediate the interactions with NuMA, while GoLoco motifs at the C terminus serve as a docking platform for four Gαi GDP subunits anchored at the plasma membrane via a myristoyl group (3).LGN exclusively binds to GDPloaded Gαi (4). The association of cortical NuMA with the microtubule motor Dynein/Dynactin (5) provides a sliding anchorage for depolymerizing microtubules, whose shrinkage pulls towards the cortex the connected spindle pole. FRET studies revealed that LGN behaves as a conformational switch held in a closed form in interphase by head-to-tail interactions (3).An issue intimately related to how force generators are assembled is how they are recruited at sites of polarization. In polarized asymmetric divisions, the apico-basal polarity axis is established by the asymmetrical distribution of Par3∶Par6∶aPKC at the apical cortex, which are able to recruit NuMA∶LGN∶Gαi GDP via an adaptor named Inscuteable (Insc) (6). Insc w...