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Repulsive cues combined with physical barriers and cell-cell adhesion determine progenitor cell positioning during organogenesis.

Paksa A, Bandemer J, Hoeckendorf B, Razin N, Tarbashevich K, Minina S, Meyen D, Biundo A, Leidel SA, Peyrieras N, Gov NS, Keller PJ, Raz E - Nat Commun (2016)

Bottom Line: Using primordial germ cells that participate in gonad formation, we present the developmental mechanisms maintaining a motile progenitor cell population at the site where the organ develops.Employing high-resolution live-cell microscopy, we find that repulsive cues coupled with physical barriers confine the cells to the correct bilateral positions.This analysis revealed that cell polarity changes on interaction with the physical barrier and that the establishment of compact clusters involves increased cell-cell interaction time.

View Article: PubMed Central - PubMed

Affiliation: Institute for Cell Biology, ZMBE, Von-Esmarch-Street 56, 48149 Muenster, Germany.

ABSTRACT
The precise positioning of organ progenitor cells constitutes an essential, yet poorly understood step during organogenesis. Using primordial germ cells that participate in gonad formation, we present the developmental mechanisms maintaining a motile progenitor cell population at the site where the organ develops. Employing high-resolution live-cell microscopy, we find that repulsive cues coupled with physical barriers confine the cells to the correct bilateral positions. This analysis revealed that cell polarity changes on interaction with the physical barrier and that the establishment of compact clusters involves increased cell-cell interaction time. Using particle-based simulations, we demonstrate the role of reflecting barriers, from which cells turn away on contact, and the importance of proper cell-cell adhesion level for maintaining the tight cell clusters and their correct positioning at the target region. The combination of these developmental and cellular mechanisms prevents organ fusion, controls organ positioning and is thus critical for its proper function.

No MeSH data available.


Related in: MedlinePlus

Boundary conditions and cell–cell adhesion level control cell cluster size and positioning.The steady-state distribution of 14 particles across the gonad region (black box in the schematic zebrafish embryo; five cell diameter wide) that is confined by non-reflective (a) or reflective boundaries (b) for different cell–cell adhesion levels (ɛ=0–0.3 (a.u.)). The y axes in the graphs represent the probability density to find a given particle at a certain position at the site of gonad. Snapshots from Supplementary Movies 9–10 (t=4850, min) for different ɛ values are provided on the right in a and b, respectively. (c) The distribution of cells at the gonad site in 24–25 hpf zebrafish embryos. N is the number of embryos and n that of PGCs.
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f7: Boundary conditions and cell–cell adhesion level control cell cluster size and positioning.The steady-state distribution of 14 particles across the gonad region (black box in the schematic zebrafish embryo; five cell diameter wide) that is confined by non-reflective (a) or reflective boundaries (b) for different cell–cell adhesion levels (ɛ=0–0.3 (a.u.)). The y axes in the graphs represent the probability density to find a given particle at a certain position at the site of gonad. Snapshots from Supplementary Movies 9–10 (t=4850, min) for different ɛ values are provided on the right in a and b, respectively. (c) The distribution of cells at the gonad site in 24–25 hpf zebrafish embryos. N is the number of embryos and n that of PGCs.

Mentions: To investigate whether differences between PGC–PGC and PGC–gut interactions could play a role in cluster formation and maintenance, we first compared the durations of such events. Interestingly, at the time of cell clustering, PGCs interact with each other for an extended time (109 min), as compared with the average duration of the PGC–gut contact (34 min; Fig. 6f; Supplementary Movie 8, sections 2 and 3). These observations suggest that PGCs maintain contact on interaction, a behaviour not observed on interaction with the gut. To quantitatively study the effects of these cellular features on the generation and positioning of cell clusters within the gonad region, we employed a simple (minimal) model, using two-dimensional particle-based simulations (Fig. 7a,b; Supplementary Movies 9–10; see methods section for details). In these simulations, the number and size of cells, their velocity, rate of change in migration direction and the dimensions of the region, as experimentally measured, were used. Each cell is represented by a particle that is interacting with the other particles (cells), with the up–down boundaries in periodic channel geometry and with the left–right boundaries as described below. The particles in the model are point-like objects that exert mutual attraction at a defined distance between them (representing cell–cell adhesion). A repulsive core prevents the particles from occupying the same position when compressed against each other. This attractive isotropic interaction potential between cells is quantified by the parameter ɛ in the model. The dynamics of the particles obeys persistent random walk behaviour44, whereby free self-propelled particles move at a constant velocity of 0.6 μm min−1, while the direction of motion is diffusing randomly with a rotational diffusion coefficient of Dr=1/(60 min). The path of such a particle maintains directional persistence for an average duration of . For simplicity, we modelled the region where the gonad develops as a chamber consisting of rigid left–right boundaries, which cells cannot penetrate. We considered two possible scenarios following cell contact with the boundaries: (i) the direction of cell motility is unaffected (non-reflective boundary), and (ii) the direction of motion of the cells is immediately changed to move perpendicularly away from the boundaries (reflective boundary). The reflective boundary acts on the cells in the same manner as contact inhibition of locomotion4546. For both of these scenarios, we examined how altering the cell–cell adhesion strength (ɛ) affected the generation and positioning of cell clusters within the chamber.


Repulsive cues combined with physical barriers and cell-cell adhesion determine progenitor cell positioning during organogenesis.

Paksa A, Bandemer J, Hoeckendorf B, Razin N, Tarbashevich K, Minina S, Meyen D, Biundo A, Leidel SA, Peyrieras N, Gov NS, Keller PJ, Raz E - Nat Commun (2016)

Boundary conditions and cell–cell adhesion level control cell cluster size and positioning.The steady-state distribution of 14 particles across the gonad region (black box in the schematic zebrafish embryo; five cell diameter wide) that is confined by non-reflective (a) or reflective boundaries (b) for different cell–cell adhesion levels (ɛ=0–0.3 (a.u.)). The y axes in the graphs represent the probability density to find a given particle at a certain position at the site of gonad. Snapshots from Supplementary Movies 9–10 (t=4850, min) for different ɛ values are provided on the right in a and b, respectively. (c) The distribution of cells at the gonad site in 24–25 hpf zebrafish embryos. N is the number of embryos and n that of PGCs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837475&req=5

f7: Boundary conditions and cell–cell adhesion level control cell cluster size and positioning.The steady-state distribution of 14 particles across the gonad region (black box in the schematic zebrafish embryo; five cell diameter wide) that is confined by non-reflective (a) or reflective boundaries (b) for different cell–cell adhesion levels (ɛ=0–0.3 (a.u.)). The y axes in the graphs represent the probability density to find a given particle at a certain position at the site of gonad. Snapshots from Supplementary Movies 9–10 (t=4850, min) for different ɛ values are provided on the right in a and b, respectively. (c) The distribution of cells at the gonad site in 24–25 hpf zebrafish embryos. N is the number of embryos and n that of PGCs.
Mentions: To investigate whether differences between PGC–PGC and PGC–gut interactions could play a role in cluster formation and maintenance, we first compared the durations of such events. Interestingly, at the time of cell clustering, PGCs interact with each other for an extended time (109 min), as compared with the average duration of the PGC–gut contact (34 min; Fig. 6f; Supplementary Movie 8, sections 2 and 3). These observations suggest that PGCs maintain contact on interaction, a behaviour not observed on interaction with the gut. To quantitatively study the effects of these cellular features on the generation and positioning of cell clusters within the gonad region, we employed a simple (minimal) model, using two-dimensional particle-based simulations (Fig. 7a,b; Supplementary Movies 9–10; see methods section for details). In these simulations, the number and size of cells, their velocity, rate of change in migration direction and the dimensions of the region, as experimentally measured, were used. Each cell is represented by a particle that is interacting with the other particles (cells), with the up–down boundaries in periodic channel geometry and with the left–right boundaries as described below. The particles in the model are point-like objects that exert mutual attraction at a defined distance between them (representing cell–cell adhesion). A repulsive core prevents the particles from occupying the same position when compressed against each other. This attractive isotropic interaction potential between cells is quantified by the parameter ɛ in the model. The dynamics of the particles obeys persistent random walk behaviour44, whereby free self-propelled particles move at a constant velocity of 0.6 μm min−1, while the direction of motion is diffusing randomly with a rotational diffusion coefficient of Dr=1/(60 min). The path of such a particle maintains directional persistence for an average duration of . For simplicity, we modelled the region where the gonad develops as a chamber consisting of rigid left–right boundaries, which cells cannot penetrate. We considered two possible scenarios following cell contact with the boundaries: (i) the direction of cell motility is unaffected (non-reflective boundary), and (ii) the direction of motion of the cells is immediately changed to move perpendicularly away from the boundaries (reflective boundary). The reflective boundary acts on the cells in the same manner as contact inhibition of locomotion4546. For both of these scenarios, we examined how altering the cell–cell adhesion strength (ɛ) affected the generation and positioning of cell clusters within the chamber.

Bottom Line: Using primordial germ cells that participate in gonad formation, we present the developmental mechanisms maintaining a motile progenitor cell population at the site where the organ develops.Employing high-resolution live-cell microscopy, we find that repulsive cues coupled with physical barriers confine the cells to the correct bilateral positions.This analysis revealed that cell polarity changes on interaction with the physical barrier and that the establishment of compact clusters involves increased cell-cell interaction time.

View Article: PubMed Central - PubMed

Affiliation: Institute for Cell Biology, ZMBE, Von-Esmarch-Street 56, 48149 Muenster, Germany.

ABSTRACT
The precise positioning of organ progenitor cells constitutes an essential, yet poorly understood step during organogenesis. Using primordial germ cells that participate in gonad formation, we present the developmental mechanisms maintaining a motile progenitor cell population at the site where the organ develops. Employing high-resolution live-cell microscopy, we find that repulsive cues coupled with physical barriers confine the cells to the correct bilateral positions. This analysis revealed that cell polarity changes on interaction with the physical barrier and that the establishment of compact clusters involves increased cell-cell interaction time. Using particle-based simulations, we demonstrate the role of reflecting barriers, from which cells turn away on contact, and the importance of proper cell-cell adhesion level for maintaining the tight cell clusters and their correct positioning at the target region. The combination of these developmental and cellular mechanisms prevents organ fusion, controls organ positioning and is thus critical for its proper function.

No MeSH data available.


Related in: MedlinePlus