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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

Myosin is localized to the cleavage furrow prior to Survivin.(a) Third instar larval neuroblasts were imaged along the xy axis (horizontal) or (c) en-face (vertical); intensity measurements were performed along a line through the midplane or at the level of the ingressing cleavage furrow, respectively. (b) and (d) Image sequence of a wild-type neuroblast expressing Survivin::GFP (green in overlay) and Sqh::mCherry (Myo; magenta in overlay). Intensity plots (Survivin, green; Myosin, magenta) are shown underneath the corresponding images. Intensity curves exceeding the scale were cut off (horizontal grey line). The vertical dashed lines refer to the position of the cortex. For all subsequent figures, coloured squares refer to the mitotic stage indicated below. Yellow and red arrowheads highlight the level of Survivin on the contractile ring and the central spindle, respectively. (e) Fluorescence intensity was measured for Survivin::GFP and Sqh::mCherry to determine the time when Survivin (green) reaches the cortical position of the future cleavage furrow in relation to Myosin (magenta; n=7). (f) Kymograph along the division axis. Note that towards the end of mitosis, Survivin shifts basally. The light green line and measurement point refer to Survivin appearing at the central spindle (CS). The dark green line and measurement point indicate Survivin shifting basally to the midbody (MB). Time in min:s; scale bar, 5 μm.
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f1: Myosin is localized to the cleavage furrow prior to Survivin.(a) Third instar larval neuroblasts were imaged along the xy axis (horizontal) or (c) en-face (vertical); intensity measurements were performed along a line through the midplane or at the level of the ingressing cleavage furrow, respectively. (b) and (d) Image sequence of a wild-type neuroblast expressing Survivin::GFP (green in overlay) and Sqh::mCherry (Myo; magenta in overlay). Intensity plots (Survivin, green; Myosin, magenta) are shown underneath the corresponding images. Intensity curves exceeding the scale were cut off (horizontal grey line). The vertical dashed lines refer to the position of the cortex. For all subsequent figures, coloured squares refer to the mitotic stage indicated below. Yellow and red arrowheads highlight the level of Survivin on the contractile ring and the central spindle, respectively. (e) Fluorescence intensity was measured for Survivin::GFP and Sqh::mCherry to determine the time when Survivin (green) reaches the cortical position of the future cleavage furrow in relation to Myosin (magenta; n=7). (f) Kymograph along the division axis. Note that towards the end of mitosis, Survivin shifts basally. The light green line and measurement point refer to Survivin appearing at the central spindle (CS). The dark green line and measurement point indicate Survivin shifting basally to the midbody (MB). Time in min:s; scale bar, 5 μm.

Mentions: To this end, we used a functional genomic Survivin::GFP construct18 and performed live imaging experiments in third instar larval neuroblasts (see Methods). We found that Survivin localizes to centromeres/kinetochores in prometaphase and metaphase, respectively, before translocating to the cell poles on separating chromosomes. During anaphase, Survivin also appeared on interdigitating microtubules that form the central spindle, becoming more enriched as anaphase progressed and moved into telophase. At the onset of furrowing, Survivin can be detected in close proximity to the neuroblast cortex, either at the cell equator, but mostly in a slightly basally shifted position (Fig. 1a–d; Supplementary Fig. 1a,b; Supplementary Movies 1 and 2).


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)

Myosin is localized to the cleavage furrow prior to Survivin.(a) Third instar larval neuroblasts were imaged along the xy axis (horizontal) or (c) en-face (vertical); intensity measurements were performed along a line through the midplane or at the level of the ingressing cleavage furrow, respectively. (b) and (d) Image sequence of a wild-type neuroblast expressing Survivin::GFP (green in overlay) and Sqh::mCherry (Myo; magenta in overlay). Intensity plots (Survivin, green; Myosin, magenta) are shown underneath the corresponding images. Intensity curves exceeding the scale were cut off (horizontal grey line). The vertical dashed lines refer to the position of the cortex. For all subsequent figures, coloured squares refer to the mitotic stage indicated below. Yellow and red arrowheads highlight the level of Survivin on the contractile ring and the central spindle, respectively. (e) Fluorescence intensity was measured for Survivin::GFP and Sqh::mCherry to determine the time when Survivin (green) reaches the cortical position of the future cleavage furrow in relation to Myosin (magenta; n=7). (f) Kymograph along the division axis. Note that towards the end of mitosis, Survivin shifts basally. The light green line and measurement point refer to Survivin appearing at the central spindle (CS). The dark green line and measurement point indicate Survivin shifting basally to the midbody (MB). Time in min:s; scale bar, 5 μm.
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f1: Myosin is localized to the cleavage furrow prior to Survivin.(a) Third instar larval neuroblasts were imaged along the xy axis (horizontal) or (c) en-face (vertical); intensity measurements were performed along a line through the midplane or at the level of the ingressing cleavage furrow, respectively. (b) and (d) Image sequence of a wild-type neuroblast expressing Survivin::GFP (green in overlay) and Sqh::mCherry (Myo; magenta in overlay). Intensity plots (Survivin, green; Myosin, magenta) are shown underneath the corresponding images. Intensity curves exceeding the scale were cut off (horizontal grey line). The vertical dashed lines refer to the position of the cortex. For all subsequent figures, coloured squares refer to the mitotic stage indicated below. Yellow and red arrowheads highlight the level of Survivin on the contractile ring and the central spindle, respectively. (e) Fluorescence intensity was measured for Survivin::GFP and Sqh::mCherry to determine the time when Survivin (green) reaches the cortical position of the future cleavage furrow in relation to Myosin (magenta; n=7). (f) Kymograph along the division axis. Note that towards the end of mitosis, Survivin shifts basally. The light green line and measurement point refer to Survivin appearing at the central spindle (CS). The dark green line and measurement point indicate Survivin shifting basally to the midbody (MB). Time in min:s; scale bar, 5 μm.
Mentions: To this end, we used a functional genomic Survivin::GFP construct18 and performed live imaging experiments in third instar larval neuroblasts (see Methods). We found that Survivin localizes to centromeres/kinetochores in prometaphase and metaphase, respectively, before translocating to the cell poles on separating chromosomes. During anaphase, Survivin also appeared on interdigitating microtubules that form the central spindle, becoming more enriched as anaphase progressed and moved into telophase. At the onset of furrowing, Survivin can be detected in close proximity to the neuroblast cortex, either at the cell equator, but mostly in a slightly basally shifted position (Fig. 1a–d; Supplementary Fig. 1a,b; Supplementary Movies 1 and 2).

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