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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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Systematic analyses of binarized images of the G1/S transition.(A) Two quantitative indices, the anterior-most red cell (ARC) and posterior-most green cell (PGC), are introduced as illustrated. (B) The positions of the ARC and PGC as a function of time. The upper and lower sequences of notochordal cells along the anterior-posterior axis are drawn individually. (C) The total number of green (S) cells in the G1/S transition window, defined as seven cells anterior to the PGC, as well as the PGC (total: 8 cells) (also demonstrated in Figure S1), as a function of time. The blue and green lines with ‘+’ markers indicate the upper and lower sequence data, respectively. (D) Number of green cell pairs in the G1/S transition window as a function of time. The red ‘+’ markers indicate the data obtained from the experiments. The black and blue lines indicate data obtained using random and biased simulation, respectively (see Methods).
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pcbi-1003957-g003: Systematic analyses of binarized images of the G1/S transition.(A) Two quantitative indices, the anterior-most red cell (ARC) and posterior-most green cell (PGC), are introduced as illustrated. (B) The positions of the ARC and PGC as a function of time. The upper and lower sequences of notochordal cells along the anterior-posterior axis are drawn individually. (C) The total number of green (S) cells in the G1/S transition window, defined as seven cells anterior to the PGC, as well as the PGC (total: 8 cells) (also demonstrated in Figure S1), as a function of time. The blue and green lines with ‘+’ markers indicate the upper and lower sequence data, respectively. (D) Number of green cell pairs in the G1/S transition window as a function of time. The red ‘+’ markers indicate the data obtained from the experiments. The black and blue lines indicate data obtained using random and biased simulation, respectively (see Methods).

Mentions: In order to further investigate the mode of this stochastic G1/S transition in more detail, we focused on spatiotemporal changes in a mixed population of red and green cells that demarcated the stochastic G1/S transition window. We scored the positions of the anterior-most red cell (ARC) and posterior-most green cell (PGC), which demarcate the anterior and posterior positions of the stochastic G1/S transition window, respectively, at each time point of observation (Figure 3A, Figure S1). Scoring of the position of the ARC and PGC showed a pattern of step-wise progression in which the position of the ARC (indicated by the red lines in Figure 3B and Figures S2A and S3A) followed and occasionally caught up to that of the PGC (green lines in Figure 3B and Figures S2A and S3A). Therefore, the stochastic G1/S transition window appeared to repeatedly widen and shorten its width (see the space enclosed by the green and red lines in the graphs shown in Figure 3B and Figures S2A and S3A).


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)

Systematic analyses of binarized images of the G1/S transition.(A) Two quantitative indices, the anterior-most red cell (ARC) and posterior-most green cell (PGC), are introduced as illustrated. (B) The positions of the ARC and PGC as a function of time. The upper and lower sequences of notochordal cells along the anterior-posterior axis are drawn individually. (C) The total number of green (S) cells in the G1/S transition window, defined as seven cells anterior to the PGC, as well as the PGC (total: 8 cells) (also demonstrated in Figure S1), as a function of time. The blue and green lines with ‘+’ markers indicate the upper and lower sequence data, respectively. (D) Number of green cell pairs in the G1/S transition window as a function of time. The red ‘+’ markers indicate the data obtained from the experiments. The black and blue lines indicate data obtained using random and biased simulation, respectively (see Methods).
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1003957-g003: Systematic analyses of binarized images of the G1/S transition.(A) Two quantitative indices, the anterior-most red cell (ARC) and posterior-most green cell (PGC), are introduced as illustrated. (B) The positions of the ARC and PGC as a function of time. The upper and lower sequences of notochordal cells along the anterior-posterior axis are drawn individually. (C) The total number of green (S) cells in the G1/S transition window, defined as seven cells anterior to the PGC, as well as the PGC (total: 8 cells) (also demonstrated in Figure S1), as a function of time. The blue and green lines with ‘+’ markers indicate the upper and lower sequence data, respectively. (D) Number of green cell pairs in the G1/S transition window as a function of time. The red ‘+’ markers indicate the data obtained from the experiments. The black and blue lines indicate data obtained using random and biased simulation, respectively (see Methods).
Mentions: In order to further investigate the mode of this stochastic G1/S transition in more detail, we focused on spatiotemporal changes in a mixed population of red and green cells that demarcated the stochastic G1/S transition window. We scored the positions of the anterior-most red cell (ARC) and posterior-most green cell (PGC), which demarcate the anterior and posterior positions of the stochastic G1/S transition window, respectively, at each time point of observation (Figure 3A, Figure S1). Scoring of the position of the ARC and PGC showed a pattern of step-wise progression in which the position of the ARC (indicated by the red lines in Figure 3B and Figures S2A and S3A) followed and occasionally caught up to that of the PGC (green lines in Figure 3B and Figures S2A and S3A). Therefore, the stochastic G1/S transition window appeared to repeatedly widen and shorten its width (see the space enclosed by the green and red lines in the graphs shown in Figure 3B and Figures S2A and S3A).

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