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Mechanisms of endoderm formation in a cartilaginous fish reveal ancestral and homoplastic traits in jawed vertebrates.

Godard BG, Coolen M, Le Panse S, Gombault A, Ferreiro-Galve S, Laguerre L, Lagadec R, Wincker P, Poulain J, Da Silva C, Kuraku S, Carre W, Boutet A, Mazan S - Biol Open (2014)

Bottom Line: Comparisons across vertebrates support the conclusion that endoderm is specified in two distinct temporal phases in the catshark as in all major osteichthyan lineages, in line with an ancient origin of a biphasic mode of endoderm specification in gnathostomes.They also highlight unexpected similarities with amniotes, such as the occurrence of cell ingressions from the superficial layer prior to gastrulation.These similarities may correspond to homoplastic traits fixed separately in amniotes and chondrichthyans and related to the increase in egg yolk mass.

View Article: PubMed Central - PubMed

Affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 7150, 29688 Roscoff, France.

No MeSH data available.


Cell internalizations from the superficial layer at the center of the blastoderm from stages 9 to 10 in S. canicula.(A) Scheme showing the experimental procedure and plane and location of the sections shown in panels C–E (red dotted lines). (B–E) DAPI staining (blue) and DiI fluorescence detection (red) on sections of embryos labeled as in panel A. (B) Example of a control stage 10 labeled embryo, cultured for one hour following DiI application. (C) Mid-sagittal section of an embryo labeled in the center of the blastoderm at stage 9 and cultured for 24 hours after DiI application. (C′) Higher magnification of the territory boxed in panel C showing labeled internalized cells. (D,E) Respectively para-sagittal and mid-sagittal sections of an embryo labeled in the center of the blastoderm at stage 10 and cultured for 24 hours after DiI application. (D′,E′) Higher magnification of the territories boxed in panels D and E showing labeled internalized cells. White arrowheads point to DiI labeled cells in the deep mesenchyme.
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f04: Cell internalizations from the superficial layer at the center of the blastoderm from stages 9 to 10 in S. canicula.(A) Scheme showing the experimental procedure and plane and location of the sections shown in panels C–E (red dotted lines). (B–E) DAPI staining (blue) and DiI fluorescence detection (red) on sections of embryos labeled as in panel A. (B) Example of a control stage 10 labeled embryo, cultured for one hour following DiI application. (C) Mid-sagittal section of an embryo labeled in the center of the blastoderm at stage 9 and cultured for 24 hours after DiI application. (C′) Higher magnification of the territory boxed in panel C showing labeled internalized cells. (D,E) Respectively para-sagittal and mid-sagittal sections of an embryo labeled in the center of the blastoderm at stage 10 and cultured for 24 hours after DiI application. (D′,E′) Higher magnification of the territories boxed in panels D and E showing labeled internalized cells. White arrowheads point to DiI labeled cells in the deep mesenchyme.

Mentions: In order to gain insight into the mode of formation of the deep mesenchyme, we next conducted a histological description, based on analysis of semi-thin sections from stage 9 to stage 11. This analysis highlighted the presence of several populations of inner cells, differing by their morphology. At stage 9, all cells appeared round shaped, with thin randomly oriented protrusions (Fig. 2A,B). At stages 10–10+, this cell morphology persisted in the anterior part of the blastoderm, lying underneath the superficial layer (Fig. 2C,D,G; see also Fig. 2K at stage 11) but cells showing an altered morphology appeared in the posterior part of the blastoderm, close to the posterior margin (Fig. 2F,I,I′). At these stages, the superficial layer of the posterior part of the blastoderm displayed a columnar morphology (Fig. 2E,H), as previously reported (Coolen et al., 2007) and cells exhibiting apical constrictions suggestive of internalizations could frequently be observed (Fig. 2E). At stage 11, two novel cell morphologies could be observed in the deep mesenchyme, (i) flattened cells lying beneath the superficial layer at the extreme anterior part of the blastoderm (Fig. 2J) and (ii) elongated cells located adjacent to, and anterior to the involuting layer, close to the yolk cell (Fig. 2L,M). The latter exhibited protrusions oriented along the AP (antero-posterior) axis, perpendicular to those of the adjacent AME involuting layer (compare Fig. 2M,N). These cell morphologies suggest that the formation of the deep mesenchyme may involve single cell internalizations and migrations from the superficial layer and posterior margin. To directly address this possibility, we used DiI cell labeling to track cells originating from these locations from mid-blastula to early gastrula stages (Fig. 3, Fig. 4). After one hour of culture following local applications of the DiI solution either at the posterior margin or at the center of the blastoderm (Fig. 3A, Fig. 4A; supplementary material Tables S1 and S2), labeled cells formed a single, superficial territory comprising 5 to 20 fluorescent cells (Fig. 3B, Fig. 4B) and were never observed either in the deep mesenchyme or involuting mesendoderm (supplementary material Tables S1 and S2). Labeled embryos were then cultured for 24 hours after DiI application and the location of fluorescent cells was examined on histological sections. In the youngest embryos injected at the posterior margin (stage 8–9; stage 10 after culture; n = 4), all fluorescent cells were found internalized as a cluster of mesenchymal cells, close to the site of injection (Fig. 3C,D; supplementary material Table S1). A marked change in the organization of fluorescent cells was observed when DiI was applied at the posterior margin at subsequent stages (stages 10/11). In these embryos, labeled cells were found displaced within the involuting mesendoderm layer as a highly coherent group but never observed in the deep mesenchyme (Fig. 3F,H; supplementary material Table S1; n = 4). DiI application at the center of the blastoderm at stages 8 (mid-blastula) to 10 (late blastula) also led to the presence of labeled cells in the deep mesenchyme in all embryos studied after culture (Fig. 4C–E,C′–E′; supplementary material Table S2; n = 6). In this case however, the superficial layer remained heavily labeled at the site of dye application, which was not observed when the dye was applied at the level of the posterior margin. Of note is that during early gastrulation, application of the dye at lateral levels of the margin resulted in an organization of fluorescent daughter cells similar to the one observed at the posterior midline at earlier stages (Fig. 3E,G). Thus, as development proceeds, cell internalizations progress laterally along the posterior margin, following the same succession of distinct cell behaviors as observed in the midline (Fig. 3I).


Mechanisms of endoderm formation in a cartilaginous fish reveal ancestral and homoplastic traits in jawed vertebrates.

Godard BG, Coolen M, Le Panse S, Gombault A, Ferreiro-Galve S, Laguerre L, Lagadec R, Wincker P, Poulain J, Da Silva C, Kuraku S, Carre W, Boutet A, Mazan S - Biol Open (2014)

Cell internalizations from the superficial layer at the center of the blastoderm from stages 9 to 10 in S. canicula.(A) Scheme showing the experimental procedure and plane and location of the sections shown in panels C–E (red dotted lines). (B–E) DAPI staining (blue) and DiI fluorescence detection (red) on sections of embryos labeled as in panel A. (B) Example of a control stage 10 labeled embryo, cultured for one hour following DiI application. (C) Mid-sagittal section of an embryo labeled in the center of the blastoderm at stage 9 and cultured for 24 hours after DiI application. (C′) Higher magnification of the territory boxed in panel C showing labeled internalized cells. (D,E) Respectively para-sagittal and mid-sagittal sections of an embryo labeled in the center of the blastoderm at stage 10 and cultured for 24 hours after DiI application. (D′,E′) Higher magnification of the territories boxed in panels D and E showing labeled internalized cells. White arrowheads point to DiI labeled cells in the deep mesenchyme.
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f04: Cell internalizations from the superficial layer at the center of the blastoderm from stages 9 to 10 in S. canicula.(A) Scheme showing the experimental procedure and plane and location of the sections shown in panels C–E (red dotted lines). (B–E) DAPI staining (blue) and DiI fluorescence detection (red) on sections of embryos labeled as in panel A. (B) Example of a control stage 10 labeled embryo, cultured for one hour following DiI application. (C) Mid-sagittal section of an embryo labeled in the center of the blastoderm at stage 9 and cultured for 24 hours after DiI application. (C′) Higher magnification of the territory boxed in panel C showing labeled internalized cells. (D,E) Respectively para-sagittal and mid-sagittal sections of an embryo labeled in the center of the blastoderm at stage 10 and cultured for 24 hours after DiI application. (D′,E′) Higher magnification of the territories boxed in panels D and E showing labeled internalized cells. White arrowheads point to DiI labeled cells in the deep mesenchyme.
Mentions: In order to gain insight into the mode of formation of the deep mesenchyme, we next conducted a histological description, based on analysis of semi-thin sections from stage 9 to stage 11. This analysis highlighted the presence of several populations of inner cells, differing by their morphology. At stage 9, all cells appeared round shaped, with thin randomly oriented protrusions (Fig. 2A,B). At stages 10–10+, this cell morphology persisted in the anterior part of the blastoderm, lying underneath the superficial layer (Fig. 2C,D,G; see also Fig. 2K at stage 11) but cells showing an altered morphology appeared in the posterior part of the blastoderm, close to the posterior margin (Fig. 2F,I,I′). At these stages, the superficial layer of the posterior part of the blastoderm displayed a columnar morphology (Fig. 2E,H), as previously reported (Coolen et al., 2007) and cells exhibiting apical constrictions suggestive of internalizations could frequently be observed (Fig. 2E). At stage 11, two novel cell morphologies could be observed in the deep mesenchyme, (i) flattened cells lying beneath the superficial layer at the extreme anterior part of the blastoderm (Fig. 2J) and (ii) elongated cells located adjacent to, and anterior to the involuting layer, close to the yolk cell (Fig. 2L,M). The latter exhibited protrusions oriented along the AP (antero-posterior) axis, perpendicular to those of the adjacent AME involuting layer (compare Fig. 2M,N). These cell morphologies suggest that the formation of the deep mesenchyme may involve single cell internalizations and migrations from the superficial layer and posterior margin. To directly address this possibility, we used DiI cell labeling to track cells originating from these locations from mid-blastula to early gastrula stages (Fig. 3, Fig. 4). After one hour of culture following local applications of the DiI solution either at the posterior margin or at the center of the blastoderm (Fig. 3A, Fig. 4A; supplementary material Tables S1 and S2), labeled cells formed a single, superficial territory comprising 5 to 20 fluorescent cells (Fig. 3B, Fig. 4B) and were never observed either in the deep mesenchyme or involuting mesendoderm (supplementary material Tables S1 and S2). Labeled embryos were then cultured for 24 hours after DiI application and the location of fluorescent cells was examined on histological sections. In the youngest embryos injected at the posterior margin (stage 8–9; stage 10 after culture; n = 4), all fluorescent cells were found internalized as a cluster of mesenchymal cells, close to the site of injection (Fig. 3C,D; supplementary material Table S1). A marked change in the organization of fluorescent cells was observed when DiI was applied at the posterior margin at subsequent stages (stages 10/11). In these embryos, labeled cells were found displaced within the involuting mesendoderm layer as a highly coherent group but never observed in the deep mesenchyme (Fig. 3F,H; supplementary material Table S1; n = 4). DiI application at the center of the blastoderm at stages 8 (mid-blastula) to 10 (late blastula) also led to the presence of labeled cells in the deep mesenchyme in all embryos studied after culture (Fig. 4C–E,C′–E′; supplementary material Table S2; n = 6). In this case however, the superficial layer remained heavily labeled at the site of dye application, which was not observed when the dye was applied at the level of the posterior margin. Of note is that during early gastrulation, application of the dye at lateral levels of the margin resulted in an organization of fluorescent daughter cells similar to the one observed at the posterior midline at earlier stages (Fig. 3E,G). Thus, as development proceeds, cell internalizations progress laterally along the posterior margin, following the same succession of distinct cell behaviors as observed in the midline (Fig. 3I).

Bottom Line: Comparisons across vertebrates support the conclusion that endoderm is specified in two distinct temporal phases in the catshark as in all major osteichthyan lineages, in line with an ancient origin of a biphasic mode of endoderm specification in gnathostomes.They also highlight unexpected similarities with amniotes, such as the occurrence of cell ingressions from the superficial layer prior to gastrulation.These similarities may correspond to homoplastic traits fixed separately in amniotes and chondrichthyans and related to the increase in egg yolk mass.

View Article: PubMed Central - PubMed

Affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 7150, 29688 Roscoff, France.

No MeSH data available.