Limits...
Asymmetrically dividing Drosophila neuroblasts utilize two spatially and temporally independent cytokinesis pathways.

Roth M, Roubinet C, Iffländer N, Ferrand A, Cabernard C - Nat Commun (2015)

Bottom Line: In most metazoan cells, contractile ring placement is regulated by the mitotic spindle through the centralspindlin complex, and potentially also the chromosomal passenger complex (CPC).Drosophila neuroblasts, asymmetrically dividing neural stem cells, but also other cells utilize both spindle-dependent and spindle-independent cleavage furrow positioning pathways.However, the relative contribution of each pathway towards cytokinesis is currently unclear.

View Article: PubMed Central - PubMed

Affiliation: Biozentrum, University of Basel, Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland.

ABSTRACT
Precise cleavage furrow positioning is required for faithful chromosome segregation and cell fate determinant distribution. In most metazoan cells, contractile ring placement is regulated by the mitotic spindle through the centralspindlin complex, and potentially also the chromosomal passenger complex (CPC). Drosophila neuroblasts, asymmetrically dividing neural stem cells, but also other cells utilize both spindle-dependent and spindle-independent cleavage furrow positioning pathways. However, the relative contribution of each pathway towards cytokinesis is currently unclear. Here we report that in Drosophila neuroblasts, the mitotic spindle, but not polarity cues, controls the localization of the CPC component Survivin. We also show that Survivin and the mitotic spindle are required to stabilize the position of the cleavage furrow in late anaphase and to complete furrow constriction. These results support the model that two spatially and temporally separate pathways control different key aspects during asymmetric cell division, ensuring correct cell fate determinant segregation and neuroblast self-renewal.

No MeSH data available.


Related in: MedlinePlus

Survivin’s localization is independent of the polarity pathway.(a) Schematic representation of the genetic spindle rotation experiment to uncouple the orientation of the mitotic spindle in relation to the neuroblast intrinsic polarity axis (apical, blue; basal, red). (b) Image sequence of a representative mud4 mutant neuroblast expressing Survivin::GFP (top row) and Sqh::mCherry (Myo; second row), dividing symmetrically and forming a polar lobe (06:30; orange arrowhead). Blue arrowheads highlight Survivin localization at the spindle-induced furrow. (c) Quantification of Survivin appearance at polarity-dependent cleavage furrow (polar lobe). Number of cells scored is highlighted in bars. (d) Survivin was ectopically localized at the apical neuroblast cortex (green); intensity measurements were performed along the dashed yellow line from apical to basal. (e) Third instar larval neuroblast expressing ALD-Survivin::EGFP (top row; green) and Sqh::mCherry (bottom row; white). Intensity measurements (green, ALD-Survivin::EGFP; grey, sqh::mCherry) are shown below. (f) Quantification of ectopic furrowing and Myosin distribution. Number of cells scored is highlighted in bars. Ap, apical; Ba, basal. Time in min:s; scale bar, 5 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4544045&req=5

f4: Survivin’s localization is independent of the polarity pathway.(a) Schematic representation of the genetic spindle rotation experiment to uncouple the orientation of the mitotic spindle in relation to the neuroblast intrinsic polarity axis (apical, blue; basal, red). (b) Image sequence of a representative mud4 mutant neuroblast expressing Survivin::GFP (top row) and Sqh::mCherry (Myo; second row), dividing symmetrically and forming a polar lobe (06:30; orange arrowhead). Blue arrowheads highlight Survivin localization at the spindle-induced furrow. (c) Quantification of Survivin appearance at polarity-dependent cleavage furrow (polar lobe). Number of cells scored is highlighted in bars. (d) Survivin was ectopically localized at the apical neuroblast cortex (green); intensity measurements were performed along the dashed yellow line from apical to basal. (e) Third instar larval neuroblast expressing ALD-Survivin::EGFP (top row; green) and Sqh::mCherry (bottom row; white). Intensity measurements (green, ALD-Survivin::EGFP; grey, sqh::mCherry) are shown below. (f) Quantification of ectopic furrowing and Myosin distribution. Number of cells scored is highlighted in bars. Ap, apical; Ba, basal. Time in min:s; scale bar, 5 μm.

Mentions: We next wanted to test whether Survivin can also get recruited to spindle-independent furrows. For instance, we used mud mutants to uncouple the mitotic spindle from the neuroblast intrinsic polarity axis232425 (Fig. 4a), inducing a spatially and temporally separate polarity-induced cleavage furrow on the basal cortex, manifested in the formation of a polar lobe11. All neuroblasts developing a polarity-dependent cleavage furrow failed to localize Survivin to this ectopic location (100%; n=8; Fig. 4b,c). However, as soon as the spindle-dependent cleavage furrow forms, Survivin can be found to colocalize with Myosin at the spindle-dependent furrow (Fig. 4b). Thus, this experiment suggests that Survivin is not recruited to the polarity-dependent cleavage furrow and is dispensable for the initiation of furrowing.


Asymmetrically dividing Drosophila neuroblasts utilize two spatially and temporally independent cytokinesis pathways.

Roth M, Roubinet C, Iffländer N, Ferrand A, Cabernard C - Nat Commun (2015)

Survivin’s localization is independent of the polarity pathway.(a) Schematic representation of the genetic spindle rotation experiment to uncouple the orientation of the mitotic spindle in relation to the neuroblast intrinsic polarity axis (apical, blue; basal, red). (b) Image sequence of a representative mud4 mutant neuroblast expressing Survivin::GFP (top row) and Sqh::mCherry (Myo; second row), dividing symmetrically and forming a polar lobe (06:30; orange arrowhead). Blue arrowheads highlight Survivin localization at the spindle-induced furrow. (c) Quantification of Survivin appearance at polarity-dependent cleavage furrow (polar lobe). Number of cells scored is highlighted in bars. (d) Survivin was ectopically localized at the apical neuroblast cortex (green); intensity measurements were performed along the dashed yellow line from apical to basal. (e) Third instar larval neuroblast expressing ALD-Survivin::EGFP (top row; green) and Sqh::mCherry (bottom row; white). Intensity measurements (green, ALD-Survivin::EGFP; grey, sqh::mCherry) are shown below. (f) Quantification of ectopic furrowing and Myosin distribution. Number of cells scored is highlighted in bars. Ap, apical; Ba, basal. Time in min:s; scale bar, 5 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4544045&req=5

f4: Survivin’s localization is independent of the polarity pathway.(a) Schematic representation of the genetic spindle rotation experiment to uncouple the orientation of the mitotic spindle in relation to the neuroblast intrinsic polarity axis (apical, blue; basal, red). (b) Image sequence of a representative mud4 mutant neuroblast expressing Survivin::GFP (top row) and Sqh::mCherry (Myo; second row), dividing symmetrically and forming a polar lobe (06:30; orange arrowhead). Blue arrowheads highlight Survivin localization at the spindle-induced furrow. (c) Quantification of Survivin appearance at polarity-dependent cleavage furrow (polar lobe). Number of cells scored is highlighted in bars. (d) Survivin was ectopically localized at the apical neuroblast cortex (green); intensity measurements were performed along the dashed yellow line from apical to basal. (e) Third instar larval neuroblast expressing ALD-Survivin::EGFP (top row; green) and Sqh::mCherry (bottom row; white). Intensity measurements (green, ALD-Survivin::EGFP; grey, sqh::mCherry) are shown below. (f) Quantification of ectopic furrowing and Myosin distribution. Number of cells scored is highlighted in bars. Ap, apical; Ba, basal. Time in min:s; scale bar, 5 μm.
Mentions: We next wanted to test whether Survivin can also get recruited to spindle-independent furrows. For instance, we used mud mutants to uncouple the mitotic spindle from the neuroblast intrinsic polarity axis232425 (Fig. 4a), inducing a spatially and temporally separate polarity-induced cleavage furrow on the basal cortex, manifested in the formation of a polar lobe11. All neuroblasts developing a polarity-dependent cleavage furrow failed to localize Survivin to this ectopic location (100%; n=8; Fig. 4b,c). However, as soon as the spindle-dependent cleavage furrow forms, Survivin can be found to colocalize with Myosin at the spindle-dependent furrow (Fig. 4b). Thus, this experiment suggests that Survivin is not recruited to the polarity-dependent cleavage furrow and is dispensable for the initiation of furrowing.

Bottom Line: In most metazoan cells, contractile ring placement is regulated by the mitotic spindle through the centralspindlin complex, and potentially also the chromosomal passenger complex (CPC).Drosophila neuroblasts, asymmetrically dividing neural stem cells, but also other cells utilize both spindle-dependent and spindle-independent cleavage furrow positioning pathways.However, the relative contribution of each pathway towards cytokinesis is currently unclear.

View Article: PubMed Central - PubMed

Affiliation: Biozentrum, University of Basel, Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland.

ABSTRACT
Precise cleavage furrow positioning is required for faithful chromosome segregation and cell fate determinant distribution. In most metazoan cells, contractile ring placement is regulated by the mitotic spindle through the centralspindlin complex, and potentially also the chromosomal passenger complex (CPC). Drosophila neuroblasts, asymmetrically dividing neural stem cells, but also other cells utilize both spindle-dependent and spindle-independent cleavage furrow positioning pathways. However, the relative contribution of each pathway towards cytokinesis is currently unclear. Here we report that in Drosophila neuroblasts, the mitotic spindle, but not polarity cues, controls the localization of the CPC component Survivin. We also show that Survivin and the mitotic spindle are required to stabilize the position of the cleavage furrow in late anaphase and to complete furrow constriction. These results support the model that two spatially and temporally separate pathways control different key aspects during asymmetric cell division, ensuring correct cell fate determinant segregation and neuroblast self-renewal.

No MeSH data available.


Related in: MedlinePlus