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Live imaging-based model selection reveals periodic regulation of the stochastic G1/S phase transition in vertebrate axial development.

Sugiyama M, Saitou T, Kurokawa H, Sakaue-Sawano A, Imamura T, Miyawaki A, Iimura T - PLoS Comput. Biol. (2014)

Bottom Line: This G1/S transition did not occur in a synchronous manner, but rather exhibited a stochastic process, since a mixed population of red and green cells was always inserted between newly formed red (G1) notochordal cells and vacuolating green cells.To obtain a better understanding of this regulatory mode, we constructed a mathematical model and performed a model selection by comparing the results obtained from the models with those from the experimental data.This approach may have implications for the characterization of the pathophysiological tissue growth mode.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Cell Function and Dynamics, Advanced Technology Development Group, Brain Science Institute, RIKEN, Wako-city, Saitama, Japan.

ABSTRACT
In multicellular organism development, a stochastic cellular response is observed, even when a population of cells is exposed to the same environmental conditions. Retrieving the spatiotemporal regulatory mode hidden in the heterogeneous cellular behavior is a challenging task. The G1/S transition observed in cell cycle progression is a highly stochastic process. By taking advantage of a fluorescence cell cycle indicator, Fucci technology, we aimed to unveil a hidden regulatory mode of cell cycle progression in developing zebrafish. Fluorescence live imaging of Cecyil, a zebrafish line genetically expressing Fucci, demonstrated that newly formed notochordal cells from the posterior tip of the embryonic mesoderm exhibited the red (G1) fluorescence signal in the developing notochord. Prior to their initial vacuolation, these cells showed a fluorescence color switch from red to green, indicating G1/S transitions. This G1/S transition did not occur in a synchronous manner, but rather exhibited a stochastic process, since a mixed population of red and green cells was always inserted between newly formed red (G1) notochordal cells and vacuolating green cells. We termed this mixed population of notochordal cells, the G1/S transition window. We first performed quantitative analyses of live imaging data and a numerical estimation of the probability of the G1/S transition, which demonstrated the existence of a posteriorly traveling regulatory wave of the G1/S transition window. To obtain a better understanding of this regulatory mode, we constructed a mathematical model and performed a model selection by comparing the results obtained from the models with those from the experimental data. Our analyses demonstrated that the stochastic G1/S transition window in the notochord travels posteriorly in a periodic fashion, with doubled the periodicity of the neighboring paraxial mesoderm segmentation. This approach may have implications for the characterization of the pathophysiological tissue growth mode.

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Scoring of the mode of the G1/S transition in the notochordal cells.(A) Binarized images of notochordal cells at three different time points (t = 50 min, 150 min and 250 min). Cells in the G1 and S phases are indicated by red and green points, respectively. (B) The dynamics of cell cycle progression are represented by a two-dimensional map on the plane of time and space (the anterior-posterior axis). The upper and lower sequences along the anterior-posterior axis are drawn individually. (C) Total number of red (G1) and green (S) cells as a function of time. The green and red lines, and the dark-green and orange lines denote the total number of S and G1 cells of the upper and lower sequences, respectively.
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pcbi-1003957-g002: Scoring of the mode of the G1/S transition in the notochordal cells.(A) Binarized images of notochordal cells at three different time points (t = 50 min, 150 min and 250 min). Cells in the G1 and S phases are indicated by red and green points, respectively. (B) The dynamics of cell cycle progression are represented by a two-dimensional map on the plane of time and space (the anterior-posterior axis). The upper and lower sequences along the anterior-posterior axis are drawn individually. (C) Total number of red (G1) and green (S) cells as a function of time. The green and red lines, and the dark-green and orange lines denote the total number of S and G1 cells of the upper and lower sequences, respectively.

Mentions: Based on this method, we next plotted the binary valued cellular states of the upper (dorsal) and lower (ventral) columns of cells in a single dimension of the anterior to posterior position (Figure 2A, Movie S2). This plotting was then applied to succeeding time lapse images. Therefore, the second dimension was introduced in order to demonstrate the temporal dynamics of the G1/S transition (Figure 2B). Notably, the spatial positions of the G1/S transition were observed to overtly progress posteriorly, although the transition in each cell did not occur in the exact order of their position, but rather in a stochastic fashion. When the total number of green and red cells was scored at each time point, it was obvious that the stochastic G1/S transition progressed posteriorly as time progressed (Figure 2C), although the modes of the upper and lower cells were not entirely synchronized.


Live imaging-based model selection reveals periodic regulation of the stochastic G1/S phase transition in vertebrate axial development.

Sugiyama M, Saitou T, Kurokawa H, Sakaue-Sawano A, Imamura T, Miyawaki A, Iimura T - PLoS Comput. Biol. (2014)

Scoring of the mode of the G1/S transition in the notochordal cells.(A) Binarized images of notochordal cells at three different time points (t = 50 min, 150 min and 250 min). Cells in the G1 and S phases are indicated by red and green points, respectively. (B) The dynamics of cell cycle progression are represented by a two-dimensional map on the plane of time and space (the anterior-posterior axis). The upper and lower sequences along the anterior-posterior axis are drawn individually. (C) Total number of red (G1) and green (S) cells as a function of time. The green and red lines, and the dark-green and orange lines denote the total number of S and G1 cells of the upper and lower sequences, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256085&req=5

pcbi-1003957-g002: Scoring of the mode of the G1/S transition in the notochordal cells.(A) Binarized images of notochordal cells at three different time points (t = 50 min, 150 min and 250 min). Cells in the G1 and S phases are indicated by red and green points, respectively. (B) The dynamics of cell cycle progression are represented by a two-dimensional map on the plane of time and space (the anterior-posterior axis). The upper and lower sequences along the anterior-posterior axis are drawn individually. (C) Total number of red (G1) and green (S) cells as a function of time. The green and red lines, and the dark-green and orange lines denote the total number of S and G1 cells of the upper and lower sequences, respectively.
Mentions: Based on this method, we next plotted the binary valued cellular states of the upper (dorsal) and lower (ventral) columns of cells in a single dimension of the anterior to posterior position (Figure 2A, Movie S2). This plotting was then applied to succeeding time lapse images. Therefore, the second dimension was introduced in order to demonstrate the temporal dynamics of the G1/S transition (Figure 2B). Notably, the spatial positions of the G1/S transition were observed to overtly progress posteriorly, although the transition in each cell did not occur in the exact order of their position, but rather in a stochastic fashion. When the total number of green and red cells was scored at each time point, it was obvious that the stochastic G1/S transition progressed posteriorly as time progressed (Figure 2C), although the modes of the upper and lower cells were not entirely synchronized.

Bottom Line: This G1/S transition did not occur in a synchronous manner, but rather exhibited a stochastic process, since a mixed population of red and green cells was always inserted between newly formed red (G1) notochordal cells and vacuolating green cells.To obtain a better understanding of this regulatory mode, we constructed a mathematical model and performed a model selection by comparing the results obtained from the models with those from the experimental data.This approach may have implications for the characterization of the pathophysiological tissue growth mode.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Cell Function and Dynamics, Advanced Technology Development Group, Brain Science Institute, RIKEN, Wako-city, Saitama, Japan.

ABSTRACT
In multicellular organism development, a stochastic cellular response is observed, even when a population of cells is exposed to the same environmental conditions. Retrieving the spatiotemporal regulatory mode hidden in the heterogeneous cellular behavior is a challenging task. The G1/S transition observed in cell cycle progression is a highly stochastic process. By taking advantage of a fluorescence cell cycle indicator, Fucci technology, we aimed to unveil a hidden regulatory mode of cell cycle progression in developing zebrafish. Fluorescence live imaging of Cecyil, a zebrafish line genetically expressing Fucci, demonstrated that newly formed notochordal cells from the posterior tip of the embryonic mesoderm exhibited the red (G1) fluorescence signal in the developing notochord. Prior to their initial vacuolation, these cells showed a fluorescence color switch from red to green, indicating G1/S transitions. This G1/S transition did not occur in a synchronous manner, but rather exhibited a stochastic process, since a mixed population of red and green cells was always inserted between newly formed red (G1) notochordal cells and vacuolating green cells. We termed this mixed population of notochordal cells, the G1/S transition window. We first performed quantitative analyses of live imaging data and a numerical estimation of the probability of the G1/S transition, which demonstrated the existence of a posteriorly traveling regulatory wave of the G1/S transition window. To obtain a better understanding of this regulatory mode, we constructed a mathematical model and performed a model selection by comparing the results obtained from the models with those from the experimental data. Our analyses demonstrated that the stochastic G1/S transition window in the notochord travels posteriorly in a periodic fashion, with doubled the periodicity of the neighboring paraxial mesoderm segmentation. This approach may have implications for the characterization of the pathophysiological tissue growth mode.

Show MeSH
Related in: MedlinePlus