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A stable microtubule array drives fission yeast polarity reestablishment upon quiescence exit.

Laporte D, Courtout F, Pinson B, Dompierre J, Salin B, Brocard L, Sagot I - J. Cell Biol. (2015)

Bottom Line: Astonishingly, MTs are also stabilized and rearranged into a novel antiparallel bundle associated with the spindle pole body, named Q-MT bundle.Finally and importantly, we reveal that Q-MT bundle elongation is involved in polarity reestablishment upon quiescence exit and thereby the efficient return to the proliferative state.Our work demonstrates that quiescent S. pombe cells assemble specific cytoskeleton structures that improve the swiftness of the transition back to proliferation.

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Affiliation: Université de Bordeaux, Institut de Biochimie et Génétique Cellulaires, 33000 Bordeaux, France Centre National de la Recherche Scientifique, UMR5095 Bordeaux, 33077 Bordeaux, France.

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Q-MT bundle elongation allows cell polarity reestablishment upon quiescence exit. (A) Quiescence exit of cells expressing the indicated polarity markers was triggered in the absence or presence of MBC. Numbers indicate the percentage of cells with polarized markers at the cell tips (N = 2 experiments and n > 200). Time is in minutes. (B–F) Cell shape is drastically impaired when the Q-MT bundle elongation is inhibited. (B) Cell shape was analyzed before and after refeeding of 5-d-old WT cells in the absence or presence of MBC. Control experiments were done in proliferating cells. Representative cells are shown. (C) Upon quiescence exit, the alp14Δ mutant is unable to elongate the Q-MT bundle and display massive cell shape defects associated with Tea1-GFP mislocalization. Alp14Δ cells expressing either GFP-Atb2 or Tea1-GFP are shown before and after cell refeeding. Cell shape was analyzed before and after refeeding or as a control in proliferation. (D) Control experiment in which tubulin is revealed by immunofluorescence using Tat1 antibodies in both WT and alp14Δ mutant cells in quiescence (5 d) and 2 h after quiescence exit. (E) After 5 d in YPD, mto1Δ-expressing GFP-Atb2 cells display a long and dynamic MT structure that is destabilized by a cold treatment (4°C for 24 h). When mto1Δ cold-treated cells are shifted back to 30°C and then refed, they do not assemble cytoplasmic MT until cells undergo mitosis. Graphs illustrate the number of MT bundles per cell. Data shown are from a single representative experiment out of four repeats (with n > 200 for each time point). The corresponding images are shown. (F) Cell shape of cold-treated mto1Δ cells was monitored upon quiescence exit. For all graphs, means and SDs are indicated. Bars, 2 µm.
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fig7: Q-MT bundle elongation allows cell polarity reestablishment upon quiescence exit. (A) Quiescence exit of cells expressing the indicated polarity markers was triggered in the absence or presence of MBC. Numbers indicate the percentage of cells with polarized markers at the cell tips (N = 2 experiments and n > 200). Time is in minutes. (B–F) Cell shape is drastically impaired when the Q-MT bundle elongation is inhibited. (B) Cell shape was analyzed before and after refeeding of 5-d-old WT cells in the absence or presence of MBC. Control experiments were done in proliferating cells. Representative cells are shown. (C) Upon quiescence exit, the alp14Δ mutant is unable to elongate the Q-MT bundle and display massive cell shape defects associated with Tea1-GFP mislocalization. Alp14Δ cells expressing either GFP-Atb2 or Tea1-GFP are shown before and after cell refeeding. Cell shape was analyzed before and after refeeding or as a control in proliferation. (D) Control experiment in which tubulin is revealed by immunofluorescence using Tat1 antibodies in both WT and alp14Δ mutant cells in quiescence (5 d) and 2 h after quiescence exit. (E) After 5 d in YPD, mto1Δ-expressing GFP-Atb2 cells display a long and dynamic MT structure that is destabilized by a cold treatment (4°C for 24 h). When mto1Δ cold-treated cells are shifted back to 30°C and then refed, they do not assemble cytoplasmic MT until cells undergo mitosis. Graphs illustrate the number of MT bundles per cell. Data shown are from a single representative experiment out of four repeats (with n > 200 for each time point). The corresponding images are shown. (F) Cell shape of cold-treated mto1Δ cells was monitored upon quiescence exit. For all graphs, means and SDs are indicated. Bars, 2 µm.

Mentions: We then analyzed the effect of MAP encoding gene deletion on the Q-MT bundle shape, stability, and formation. None of the deletions tested resulted in the absence of MT bundle (Fig. 4 D) or its destabilization (Fig. S3 C). However, in some mutants, whereas the steady-state level of total α-tubulin remained constant (Fig. S3 B), the Q-MT bundle was either both thicker and longer (klp5Δklp6Δ, alp7Δ, and dis1Δ), just thinner (ase1Δ), or both shorter and thinner (mal3Δ and alp14Δ; Fig. 4, E and F). These results indicated that MAPs involved in interphase MT length regulation are also involved in shaping the Q-MT bundle in quiescence. Besides, mutants with an altered Q-MT shape did not display mortality in quiescence (Fig. S3 D) nor a cell shape defect upon quiescence exit (Fig. S3 E), with the exception of alp14Δ cells (see the following paragraph and Fig. 7 C).


A stable microtubule array drives fission yeast polarity reestablishment upon quiescence exit.

Laporte D, Courtout F, Pinson B, Dompierre J, Salin B, Brocard L, Sagot I - J. Cell Biol. (2015)

Q-MT bundle elongation allows cell polarity reestablishment upon quiescence exit. (A) Quiescence exit of cells expressing the indicated polarity markers was triggered in the absence or presence of MBC. Numbers indicate the percentage of cells with polarized markers at the cell tips (N = 2 experiments and n > 200). Time is in minutes. (B–F) Cell shape is drastically impaired when the Q-MT bundle elongation is inhibited. (B) Cell shape was analyzed before and after refeeding of 5-d-old WT cells in the absence or presence of MBC. Control experiments were done in proliferating cells. Representative cells are shown. (C) Upon quiescence exit, the alp14Δ mutant is unable to elongate the Q-MT bundle and display massive cell shape defects associated with Tea1-GFP mislocalization. Alp14Δ cells expressing either GFP-Atb2 or Tea1-GFP are shown before and after cell refeeding. Cell shape was analyzed before and after refeeding or as a control in proliferation. (D) Control experiment in which tubulin is revealed by immunofluorescence using Tat1 antibodies in both WT and alp14Δ mutant cells in quiescence (5 d) and 2 h after quiescence exit. (E) After 5 d in YPD, mto1Δ-expressing GFP-Atb2 cells display a long and dynamic MT structure that is destabilized by a cold treatment (4°C for 24 h). When mto1Δ cold-treated cells are shifted back to 30°C and then refed, they do not assemble cytoplasmic MT until cells undergo mitosis. Graphs illustrate the number of MT bundles per cell. Data shown are from a single representative experiment out of four repeats (with n > 200 for each time point). The corresponding images are shown. (F) Cell shape of cold-treated mto1Δ cells was monitored upon quiescence exit. For all graphs, means and SDs are indicated. Bars, 2 µm.
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fig7: Q-MT bundle elongation allows cell polarity reestablishment upon quiescence exit. (A) Quiescence exit of cells expressing the indicated polarity markers was triggered in the absence or presence of MBC. Numbers indicate the percentage of cells with polarized markers at the cell tips (N = 2 experiments and n > 200). Time is in minutes. (B–F) Cell shape is drastically impaired when the Q-MT bundle elongation is inhibited. (B) Cell shape was analyzed before and after refeeding of 5-d-old WT cells in the absence or presence of MBC. Control experiments were done in proliferating cells. Representative cells are shown. (C) Upon quiescence exit, the alp14Δ mutant is unable to elongate the Q-MT bundle and display massive cell shape defects associated with Tea1-GFP mislocalization. Alp14Δ cells expressing either GFP-Atb2 or Tea1-GFP are shown before and after cell refeeding. Cell shape was analyzed before and after refeeding or as a control in proliferation. (D) Control experiment in which tubulin is revealed by immunofluorescence using Tat1 antibodies in both WT and alp14Δ mutant cells in quiescence (5 d) and 2 h after quiescence exit. (E) After 5 d in YPD, mto1Δ-expressing GFP-Atb2 cells display a long and dynamic MT structure that is destabilized by a cold treatment (4°C for 24 h). When mto1Δ cold-treated cells are shifted back to 30°C and then refed, they do not assemble cytoplasmic MT until cells undergo mitosis. Graphs illustrate the number of MT bundles per cell. Data shown are from a single representative experiment out of four repeats (with n > 200 for each time point). The corresponding images are shown. (F) Cell shape of cold-treated mto1Δ cells was monitored upon quiescence exit. For all graphs, means and SDs are indicated. Bars, 2 µm.
Mentions: We then analyzed the effect of MAP encoding gene deletion on the Q-MT bundle shape, stability, and formation. None of the deletions tested resulted in the absence of MT bundle (Fig. 4 D) or its destabilization (Fig. S3 C). However, in some mutants, whereas the steady-state level of total α-tubulin remained constant (Fig. S3 B), the Q-MT bundle was either both thicker and longer (klp5Δklp6Δ, alp7Δ, and dis1Δ), just thinner (ase1Δ), or both shorter and thinner (mal3Δ and alp14Δ; Fig. 4, E and F). These results indicated that MAPs involved in interphase MT length regulation are also involved in shaping the Q-MT bundle in quiescence. Besides, mutants with an altered Q-MT shape did not display mortality in quiescence (Fig. S3 D) nor a cell shape defect upon quiescence exit (Fig. S3 E), with the exception of alp14Δ cells (see the following paragraph and Fig. 7 C).

Bottom Line: Astonishingly, MTs are also stabilized and rearranged into a novel antiparallel bundle associated with the spindle pole body, named Q-MT bundle.Finally and importantly, we reveal that Q-MT bundle elongation is involved in polarity reestablishment upon quiescence exit and thereby the efficient return to the proliferative state.Our work demonstrates that quiescent S. pombe cells assemble specific cytoskeleton structures that improve the swiftness of the transition back to proliferation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Université de Bordeaux, Institut de Biochimie et Génétique Cellulaires, 33000 Bordeaux, France Centre National de la Recherche Scientifique, UMR5095 Bordeaux, 33077 Bordeaux, France.

Show MeSH
Related in: MedlinePlus