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Paired arrangement of kinetochores together with microtubule pivoting and dynamics drive kinetochore capture in meiosis I.

Cojoc G, Florescu AM, Krull A, Klemm AH, Pavin N, Jülicher F, Tolić IM - Sci Rep (2016)

Bottom Line: Our theory describes paired kinetochores on homologous chromosomes as a single object, as well as angular movement of microtubules and their dynamics.For the experimentally measured parameters, the model reproduces the measured capture kinetics and shows that the paired configuration of kinetochores accelerates capture, whereas microtubule pivoting and dynamics have a smaller contribution.Kinetochore pairing may be a general feature that increases capture efficiency in meiotic cells.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.

ABSTRACT
Kinetochores are protein complexes on the chromosomes, whose function as linkers between spindle microtubules and chromosomes is crucial for proper cell division. The mechanisms that facilitate kinetochore capture by microtubules are still unclear. In the present study, we combine experiments and theory to explore the mechanisms of kinetochore capture at the onset of meiosis I in fission yeast. We show that kinetochores on homologous chromosomes move together, microtubules are dynamic and pivot around the spindle pole, and the average capture time is 3-4 minutes. Our theory describes paired kinetochores on homologous chromosomes as a single object, as well as angular movement of microtubules and their dynamics. For the experimentally measured parameters, the model reproduces the measured capture kinetics and shows that the paired configuration of kinetochores accelerates capture, whereas microtubule pivoting and dynamics have a smaller contribution. Kinetochore pairing may be a general feature that increases capture efficiency in meiotic cells.

No MeSH data available.


Related in: MedlinePlus

KCs move and are captured in pairs.All data shown in this figure were obtained by using the strains GC03 and GC04. The zygotes expressed α-tubulin-mCherry, shown in magenta, and Ndc80-GFP, shown in green. (A) Normalized averaged fraction of free KCs as a function of time (mean ± s.e.m., n = 102, time bin = 45 seconds). An exponential fit to the equation  (green line) yielded a half-life t1/2 = 2.31 ± 0.09 minutes. (B) Time-lapse images and corresponding drawings representing KCs forming 3 pairs. In the second image the first pair is captured and moved to the SPB. Scale bar is 2 μm. (C) Correlation between the distances KC-SPB for each pair (in green). On the x-axis is the distance between the first captured KC in a pair and the SPB, and on the y-axis the distance between the second captured KC and the corresponding SPB. In the inset, no correlation between KC-SPB distances of KC’s from different pairs (black). On the x-axis is the distance between a KC and the SPB, and on y-axis is the distance between each KC from other pairs and SPB. (D) Mean squared displacement of the KC pair. A weighted fit to the equation MSD = 4DKCΔt + offset (green line) yielded a diffusion coefficient of KC pair DKC = 3.9 ± 0.2 *10−4 μm/s (mean ± SD, n = 51). KCs were tracked with subpixel resolution (Methods) and the center of mass of a pair was calculated. Grey denotes the area corresponding to subpixel movement. (E) Time-lapse images representing the capture and retrieval of a KC pair. First, one KC is captured and pulled toward the SPB (white area). The second KCin this pair does not move for about 15 seconds (4 frames), but afterwards starts to move towards the SPB. Time difference between frames Δt = 3.85 seconds. Scale bar is 1 μm. (F) Top: distance between each KC and the SPB. Circles, squares and triangles mark different KC pairs, see legend. Bottom: distance between the KCs from the same pair. The magenta dashed lines represent the capture event of the first KC in each pair. (G) Box plots of the delay capture time between pairs (left) and delay capture time between KCs inside each pair (right).
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f1: KCs move and are captured in pairs.All data shown in this figure were obtained by using the strains GC03 and GC04. The zygotes expressed α-tubulin-mCherry, shown in magenta, and Ndc80-GFP, shown in green. (A) Normalized averaged fraction of free KCs as a function of time (mean ± s.e.m., n = 102, time bin = 45 seconds). An exponential fit to the equation (green line) yielded a half-life t1/2 = 2.31 ± 0.09 minutes. (B) Time-lapse images and corresponding drawings representing KCs forming 3 pairs. In the second image the first pair is captured and moved to the SPB. Scale bar is 2 μm. (C) Correlation between the distances KC-SPB for each pair (in green). On the x-axis is the distance between the first captured KC in a pair and the SPB, and on the y-axis the distance between the second captured KC and the corresponding SPB. In the inset, no correlation between KC-SPB distances of KC’s from different pairs (black). On the x-axis is the distance between a KC and the SPB, and on y-axis is the distance between each KC from other pairs and SPB. (D) Mean squared displacement of the KC pair. A weighted fit to the equation MSD = 4DKCΔt + offset (green line) yielded a diffusion coefficient of KC pair DKC = 3.9 ± 0.2 *10−4 μm/s (mean ± SD, n = 51). KCs were tracked with subpixel resolution (Methods) and the center of mass of a pair was calculated. Grey denotes the area corresponding to subpixel movement. (E) Time-lapse images representing the capture and retrieval of a KC pair. First, one KC is captured and pulled toward the SPB (white area). The second KCin this pair does not move for about 15 seconds (4 frames), but afterwards starts to move towards the SPB. Time difference between frames Δt = 3.85 seconds. Scale bar is 1 μm. (F) Top: distance between each KC and the SPB. Circles, squares and triangles mark different KC pairs, see legend. Bottom: distance between the KCs from the same pair. The magenta dashed lines represent the capture event of the first KC in each pair. (G) Box plots of the delay capture time between pairs (left) and delay capture time between KCs inside each pair (right).

Mentions: To quantify the kinetics of KC capture, we measured the decrease in number of free KCs over time. Free KCs were defined as KCs that freely move within the nucleoplasm without being connected to any MT or to SPBs. A KC was considered captured when the signals from the KC and MT overlap and the KC starts to move toward the SPBs. The time reference was chosen as the frame when the first capture was observed. For this system, the process of capturing lasts, on average, for about 12 minutes and only for one cell, we observed that the process of capturing took more than 15 minutes. The average number of the free KCs was halved within 2.31 ± 0.09 minutes (Fig. 1A), which defines the typical capture time in this system.


Paired arrangement of kinetochores together with microtubule pivoting and dynamics drive kinetochore capture in meiosis I.

Cojoc G, Florescu AM, Krull A, Klemm AH, Pavin N, Jülicher F, Tolić IM - Sci Rep (2016)

KCs move and are captured in pairs.All data shown in this figure were obtained by using the strains GC03 and GC04. The zygotes expressed α-tubulin-mCherry, shown in magenta, and Ndc80-GFP, shown in green. (A) Normalized averaged fraction of free KCs as a function of time (mean ± s.e.m., n = 102, time bin = 45 seconds). An exponential fit to the equation  (green line) yielded a half-life t1/2 = 2.31 ± 0.09 minutes. (B) Time-lapse images and corresponding drawings representing KCs forming 3 pairs. In the second image the first pair is captured and moved to the SPB. Scale bar is 2 μm. (C) Correlation between the distances KC-SPB for each pair (in green). On the x-axis is the distance between the first captured KC in a pair and the SPB, and on the y-axis the distance between the second captured KC and the corresponding SPB. In the inset, no correlation between KC-SPB distances of KC’s from different pairs (black). On the x-axis is the distance between a KC and the SPB, and on y-axis is the distance between each KC from other pairs and SPB. (D) Mean squared displacement of the KC pair. A weighted fit to the equation MSD = 4DKCΔt + offset (green line) yielded a diffusion coefficient of KC pair DKC = 3.9 ± 0.2 *10−4 μm/s (mean ± SD, n = 51). KCs were tracked with subpixel resolution (Methods) and the center of mass of a pair was calculated. Grey denotes the area corresponding to subpixel movement. (E) Time-lapse images representing the capture and retrieval of a KC pair. First, one KC is captured and pulled toward the SPB (white area). The second KCin this pair does not move for about 15 seconds (4 frames), but afterwards starts to move towards the SPB. Time difference between frames Δt = 3.85 seconds. Scale bar is 1 μm. (F) Top: distance between each KC and the SPB. Circles, squares and triangles mark different KC pairs, see legend. Bottom: distance between the KCs from the same pair. The magenta dashed lines represent the capture event of the first KC in each pair. (G) Box plots of the delay capture time between pairs (left) and delay capture time between KCs inside each pair (right).
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Related In: Results  -  Collection

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f1: KCs move and are captured in pairs.All data shown in this figure were obtained by using the strains GC03 and GC04. The zygotes expressed α-tubulin-mCherry, shown in magenta, and Ndc80-GFP, shown in green. (A) Normalized averaged fraction of free KCs as a function of time (mean ± s.e.m., n = 102, time bin = 45 seconds). An exponential fit to the equation (green line) yielded a half-life t1/2 = 2.31 ± 0.09 minutes. (B) Time-lapse images and corresponding drawings representing KCs forming 3 pairs. In the second image the first pair is captured and moved to the SPB. Scale bar is 2 μm. (C) Correlation between the distances KC-SPB for each pair (in green). On the x-axis is the distance between the first captured KC in a pair and the SPB, and on the y-axis the distance between the second captured KC and the corresponding SPB. In the inset, no correlation between KC-SPB distances of KC’s from different pairs (black). On the x-axis is the distance between a KC and the SPB, and on y-axis is the distance between each KC from other pairs and SPB. (D) Mean squared displacement of the KC pair. A weighted fit to the equation MSD = 4DKCΔt + offset (green line) yielded a diffusion coefficient of KC pair DKC = 3.9 ± 0.2 *10−4 μm/s (mean ± SD, n = 51). KCs were tracked with subpixel resolution (Methods) and the center of mass of a pair was calculated. Grey denotes the area corresponding to subpixel movement. (E) Time-lapse images representing the capture and retrieval of a KC pair. First, one KC is captured and pulled toward the SPB (white area). The second KCin this pair does not move for about 15 seconds (4 frames), but afterwards starts to move towards the SPB. Time difference between frames Δt = 3.85 seconds. Scale bar is 1 μm. (F) Top: distance between each KC and the SPB. Circles, squares and triangles mark different KC pairs, see legend. Bottom: distance between the KCs from the same pair. The magenta dashed lines represent the capture event of the first KC in each pair. (G) Box plots of the delay capture time between pairs (left) and delay capture time between KCs inside each pair (right).
Mentions: To quantify the kinetics of KC capture, we measured the decrease in number of free KCs over time. Free KCs were defined as KCs that freely move within the nucleoplasm without being connected to any MT or to SPBs. A KC was considered captured when the signals from the KC and MT overlap and the KC starts to move toward the SPBs. The time reference was chosen as the frame when the first capture was observed. For this system, the process of capturing lasts, on average, for about 12 minutes and only for one cell, we observed that the process of capturing took more than 15 minutes. The average number of the free KCs was halved within 2.31 ± 0.09 minutes (Fig. 1A), which defines the typical capture time in this system.

Bottom Line: Our theory describes paired kinetochores on homologous chromosomes as a single object, as well as angular movement of microtubules and their dynamics.For the experimentally measured parameters, the model reproduces the measured capture kinetics and shows that the paired configuration of kinetochores accelerates capture, whereas microtubule pivoting and dynamics have a smaller contribution.Kinetochore pairing may be a general feature that increases capture efficiency in meiotic cells.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.

ABSTRACT
Kinetochores are protein complexes on the chromosomes, whose function as linkers between spindle microtubules and chromosomes is crucial for proper cell division. The mechanisms that facilitate kinetochore capture by microtubules are still unclear. In the present study, we combine experiments and theory to explore the mechanisms of kinetochore capture at the onset of meiosis I in fission yeast. We show that kinetochores on homologous chromosomes move together, microtubules are dynamic and pivot around the spindle pole, and the average capture time is 3-4 minutes. Our theory describes paired kinetochores on homologous chromosomes as a single object, as well as angular movement of microtubules and their dynamics. For the experimentally measured parameters, the model reproduces the measured capture kinetics and shows that the paired configuration of kinetochores accelerates capture, whereas microtubule pivoting and dynamics have a smaller contribution. Kinetochore pairing may be a general feature that increases capture efficiency in meiotic cells.

No MeSH data available.


Related in: MedlinePlus