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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

Expression patterns of cxcl12a and lpp variants.(a) cxcl12a is expressed at the site where the gonad develops within a 24 hpf embryo (green box and red arrowhead in the inset in the left panel), but not in 28 hpf embryos (right panel). Higher expression level of cxcl12a is detected in the lateral line (blue arrows). Scale bar, 50 μm. (b) lpp1 (variants X1 and X2) and lpp3 are expressed in the somites and developing vessels. See also Supplementary Fig. 3.
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f2: Expression patterns of cxcl12a and lpp variants.(a) cxcl12a is expressed at the site where the gonad develops within a 24 hpf embryo (green box and red arrowhead in the inset in the left panel), but not in 28 hpf embryos (right panel). Higher expression level of cxcl12a is detected in the lateral line (blue arrows). Scale bar, 50 μm. (b) lpp1 (variants X1 and X2) and lpp3 are expressed in the somites and developing vessels. See also Supplementary Fig. 3.

Mentions: Zebrafish PGCs are directed towards their target by the attractant Cxcl12a that is produced by somatic cells along the migration route1730. Considering that the PGCs are motile after arrival at the gonad region, a mechanism for confining the cells to this domain could involve continuous restricted expression of cxcl12a at the target area. However, whereas a low level of cxcl12a transcripts could still be detected at the gonad region in 24 hpf embryos (Fig. 2a, red arrowhead; Supplementary Fig. 1a, magenta bracket upper panel), the level of mRNA expression progressively decreased. Even when employing RNAscope31, a sensitive and quantitative method to detect RNA expression, no specific signal was detectable by 28 hpf, (Fig. 2a, right panel; Supplementary Fig. 1a, magenta bracket lower panel), while nearby structures showed very strong expression (for example, the lateral line that is located about 60 μm from the PGC cluster; Fig. 2a, blue arrow in the right panel; Supplementary Fig. 1a, white arrows). The lack of cxcl12a expression at the gonad region at 28 hpf, coupled with the absence of detectable transcripts of cxcl12b encoding for a weaker Cxcr4b ligand32 (Supplementary Fig. 1b; left panel) and the fact that the PGCs apparently do not respond to nearby strong sources of Cxcl12a, call for other mechanisms that would confine the cells to the site where the gonad develops.


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)

Expression patterns of cxcl12a and lpp variants.(a) cxcl12a is expressed at the site where the gonad develops within a 24 hpf embryo (green box and red arrowhead in the inset in the left panel), but not in 28 hpf embryos (right panel). Higher expression level of cxcl12a is detected in the lateral line (blue arrows). Scale bar, 50 μm. (b) lpp1 (variants X1 and X2) and lpp3 are expressed in the somites and developing vessels. See also Supplementary Fig. 3.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Expression patterns of cxcl12a and lpp variants.(a) cxcl12a is expressed at the site where the gonad develops within a 24 hpf embryo (green box and red arrowhead in the inset in the left panel), but not in 28 hpf embryos (right panel). Higher expression level of cxcl12a is detected in the lateral line (blue arrows). Scale bar, 50 μm. (b) lpp1 (variants X1 and X2) and lpp3 are expressed in the somites and developing vessels. See also Supplementary Fig. 3.
Mentions: Zebrafish PGCs are directed towards their target by the attractant Cxcl12a that is produced by somatic cells along the migration route1730. Considering that the PGCs are motile after arrival at the gonad region, a mechanism for confining the cells to this domain could involve continuous restricted expression of cxcl12a at the target area. However, whereas a low level of cxcl12a transcripts could still be detected at the gonad region in 24 hpf embryos (Fig. 2a, red arrowhead; Supplementary Fig. 1a, magenta bracket upper panel), the level of mRNA expression progressively decreased. Even when employing RNAscope31, a sensitive and quantitative method to detect RNA expression, no specific signal was detectable by 28 hpf, (Fig. 2a, right panel; Supplementary Fig. 1a, magenta bracket lower panel), while nearby structures showed very strong expression (for example, the lateral line that is located about 60 μm from the PGC cluster; Fig. 2a, blue arrow in the right panel; Supplementary Fig. 1a, white arrows). The lack of cxcl12a expression at the gonad region at 28 hpf, coupled with the absence of detectable transcripts of cxcl12b encoding for a weaker Cxcr4b ligand32 (Supplementary Fig. 1b; left panel) and the fact that the PGCs apparently do not respond to nearby strong sources of Cxcl12a, call for other mechanisms that would confine the cells to the site where the gonad develops.

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