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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

The mitotic spindle regulates furrow constriction through the CPC.(a) Image sequence of a representative rodH4.8 mutant neuroblast treated with colcemid, expressing Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). The mitotic spindle is completely depolymerized. (b) Diameter measurements of rodH4.8 and colcemid neuroblasts. The grey dashed line indicates the minimal diameter. (c) Corresponding constriction rates of rodH4.8 and colcemid neuroblasts. Averages and s.d. are shown (n=15). (d) Image sequence of a sas4 mutant neuroblast, expressing Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). (e) Diameter measurements and (f) constriction rates of sas4 mutant neuroblasts (n=10). (g) Image sequence of a representative neuroblasts, expressing RNAi against aurB, Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). (h) Diameter measurements and (i) constriction rates (n=4). Time in min:s; scale bar, 5 μm.
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f6: The mitotic spindle regulates furrow constriction through the CPC.(a) Image sequence of a representative rodH4.8 mutant neuroblast treated with colcemid, expressing Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). The mitotic spindle is completely depolymerized. (b) Diameter measurements of rodH4.8 and colcemid neuroblasts. The grey dashed line indicates the minimal diameter. (c) Corresponding constriction rates of rodH4.8 and colcemid neuroblasts. Averages and s.d. are shown (n=15). (d) Image sequence of a sas4 mutant neuroblast, expressing Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). (e) Diameter measurements and (f) constriction rates of sas4 mutant neuroblasts (n=10). (g) Image sequence of a representative neuroblasts, expressing RNAi against aurB, Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). (h) Diameter measurements and (i) constriction rates (n=4). Time in min:s; scale bar, 5 μm.

Mentions: Failure to constrict could be due to central spindle defects since scpo mutants have been reported to perturb central spindle formation18. We analysed central spindle organization using kymographs, and found that wild-type neuroblast MTs bundled up during anaphase, but scpo mutant MTs appeared dispersed (data not shown). Thus, we asked whether the mitotic spindle is involved in cleavage furrow assembly, initiation, progression or completion of furrow constriction. To this end, we removed the mitotic spindle with colcemid in the spindle-assembly checkpoint mutant rod to allow entry into anaphase (see also above). We confirmed the previous result that rod mutant neuroblasts treated with colcemid and thus lacking the mitotic spindle entirely, show normal apical clearing of Myosin and initiate cleavage furrow constriction (Fig. 6a; refs 11, 15 and Supplementary Movie 6). Similar to scpo mutant neuroblasts, ingressing cleavage furrows failed to complete constricting and reopened during anaphase (Fig. 6a–c; Table 1).


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)

The mitotic spindle regulates furrow constriction through the CPC.(a) Image sequence of a representative rodH4.8 mutant neuroblast treated with colcemid, expressing Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). The mitotic spindle is completely depolymerized. (b) Diameter measurements of rodH4.8 and colcemid neuroblasts. The grey dashed line indicates the minimal diameter. (c) Corresponding constriction rates of rodH4.8 and colcemid neuroblasts. Averages and s.d. are shown (n=15). (d) Image sequence of a sas4 mutant neuroblast, expressing Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). (e) Diameter measurements and (f) constriction rates of sas4 mutant neuroblasts (n=10). (g) Image sequence of a representative neuroblasts, expressing RNAi against aurB, Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). (h) Diameter measurements and (i) constriction rates (n=4). 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

f6: The mitotic spindle regulates furrow constriction through the CPC.(a) Image sequence of a representative rodH4.8 mutant neuroblast treated with colcemid, expressing Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). The mitotic spindle is completely depolymerized. (b) Diameter measurements of rodH4.8 and colcemid neuroblasts. The grey dashed line indicates the minimal diameter. (c) Corresponding constriction rates of rodH4.8 and colcemid neuroblasts. Averages and s.d. are shown (n=15). (d) Image sequence of a sas4 mutant neuroblast, expressing Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). (e) Diameter measurements and (f) constriction rates of sas4 mutant neuroblasts (n=10). (g) Image sequence of a representative neuroblasts, expressing RNAi against aurB, Sqh::GFP (green in overlay) and mCherry::Jupiter (white in overlay). (h) Diameter measurements and (i) constriction rates (n=4). Time in min:s; scale bar, 5 μm.
Mentions: Failure to constrict could be due to central spindle defects since scpo mutants have been reported to perturb central spindle formation18. We analysed central spindle organization using kymographs, and found that wild-type neuroblast MTs bundled up during anaphase, but scpo mutant MTs appeared dispersed (data not shown). Thus, we asked whether the mitotic spindle is involved in cleavage furrow assembly, initiation, progression or completion of furrow constriction. To this end, we removed the mitotic spindle with colcemid in the spindle-assembly checkpoint mutant rod to allow entry into anaphase (see also above). We confirmed the previous result that rod mutant neuroblasts treated with colcemid and thus lacking the mitotic spindle entirely, show normal apical clearing of Myosin and initiate cleavage furrow constriction (Fig. 6a; refs 11, 15 and Supplementary Movie 6). Similar to scpo mutant neuroblasts, ingressing cleavage furrows failed to complete constricting and reopened during anaphase (Fig. 6a–c; Table 1).

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