Abstract
During intrinsically asymmetric division, the spindle is oriented onto a polarized axis specified by a group of conserved PAR proteins. Extrinsic geometric asymmetry generated by cell shape also affects spindle orientation in some systems, but how intrinsic and extrinsic mechanisms coexist without interfering with each other is unknown. In some asymmetrically dividing cells of the wild-type Caenorhabditis elegans embryo, nuclear rotation directed toward the anterior cortex orients the forming spindle. We find that in such cells, a PAR-dependent mechanism dominates and causes rotation onto the polarized axis, regardless of cell shape. However, when geometric asymmetry is removed, free nuclear rotation in the center of the cell is observed, indicating that the anterior-directed nature of rotation in unaltered embryos is an effect of cell shape. This free rotation is inconsistent with the prevailing model for nuclear rotation, the specialized cortical site model. In contrast, in par-3 mutant embryos, a geometrydependent mechanism becomes active and causes directed nuclear rotation. These results lead to the model that in wild-type embryos both PAR-3 and PAR-2 are essential for nuclear rotation in asymmetrically dividing cells, but that PAR-3 inhibits geometry-dependent rotation in nonpolarized cells, thus preventing cell shape from interfering with spindle orientation.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 845-855 |
| Number of pages | 11 |
| Journal | Journal of Cell Biology |
| Volume | 160 |
| Issue number | 6 |
| DOIs | |
| State | Published - Mar 17 2003 |
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Keywords
- Asymmetric division
- LET-99
- PAR proreins
- Polarity
- Spindle orientation
ASJC Scopus subject areas
- Cell Biology
Cite this
PAR-dependent and geometry-dependent mechanisms of spindle positioning. / Tsou, Meng Fu Bryan; Ku, Wei; Hayashi, Adam; Rose, Lesilee S.
In: Journal of Cell Biology, Vol. 160, No. 6, 17.03.2003, p. 845-855.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - PAR-dependent and geometry-dependent mechanisms of spindle positioning
AU - Tsou, Meng Fu Bryan
AU - Ku, Wei
AU - Hayashi, Adam
AU - Rose, Lesilee S.
PY - 2003/3/17
Y1 - 2003/3/17
N2 - During intrinsically asymmetric division, the spindle is oriented onto a polarized axis specified by a group of conserved PAR proteins. Extrinsic geometric asymmetry generated by cell shape also affects spindle orientation in some systems, but how intrinsic and extrinsic mechanisms coexist without interfering with each other is unknown. In some asymmetrically dividing cells of the wild-type Caenorhabditis elegans embryo, nuclear rotation directed toward the anterior cortex orients the forming spindle. We find that in such cells, a PAR-dependent mechanism dominates and causes rotation onto the polarized axis, regardless of cell shape. However, when geometric asymmetry is removed, free nuclear rotation in the center of the cell is observed, indicating that the anterior-directed nature of rotation in unaltered embryos is an effect of cell shape. This free rotation is inconsistent with the prevailing model for nuclear rotation, the specialized cortical site model. In contrast, in par-3 mutant embryos, a geometrydependent mechanism becomes active and causes directed nuclear rotation. These results lead to the model that in wild-type embryos both PAR-3 and PAR-2 are essential for nuclear rotation in asymmetrically dividing cells, but that PAR-3 inhibits geometry-dependent rotation in nonpolarized cells, thus preventing cell shape from interfering with spindle orientation.
AB - During intrinsically asymmetric division, the spindle is oriented onto a polarized axis specified by a group of conserved PAR proteins. Extrinsic geometric asymmetry generated by cell shape also affects spindle orientation in some systems, but how intrinsic and extrinsic mechanisms coexist without interfering with each other is unknown. In some asymmetrically dividing cells of the wild-type Caenorhabditis elegans embryo, nuclear rotation directed toward the anterior cortex orients the forming spindle. We find that in such cells, a PAR-dependent mechanism dominates and causes rotation onto the polarized axis, regardless of cell shape. However, when geometric asymmetry is removed, free nuclear rotation in the center of the cell is observed, indicating that the anterior-directed nature of rotation in unaltered embryos is an effect of cell shape. This free rotation is inconsistent with the prevailing model for nuclear rotation, the specialized cortical site model. In contrast, in par-3 mutant embryos, a geometrydependent mechanism becomes active and causes directed nuclear rotation. These results lead to the model that in wild-type embryos both PAR-3 and PAR-2 are essential for nuclear rotation in asymmetrically dividing cells, but that PAR-3 inhibits geometry-dependent rotation in nonpolarized cells, thus preventing cell shape from interfering with spindle orientation.
KW - Asymmetric division
KW - LET-99
KW - PAR proreins
KW - Polarity
KW - Spindle orientation
UR - http://www.scopus.com/inward/record.url?scp=0345268758&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0345268758&partnerID=8YFLogxK
U2 - 10.1083/jcb.200209079
DO - 10.1083/jcb.200209079
M3 - Article
C2 - 12642612
AN - SCOPUS:0345268758
VL - 160
SP - 845
EP - 855
JO - Journal of Cell Biology
JF - Journal of Cell Biology
SN - 0021-9525
IS - 6
ER -