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NG2 glia are required for vessel network formation during embryonic development.

Minocha S, Valloton D, Brunet I, Eichmann A, Hornung JP, Lebrand C - Elife (2015)

Bottom Line: Interestingly, their appearance temporally coincides with the establishment of blood vessel network in the embryonic brain.NG2(+) glia are closely apposed to developing cerebral vessels by being either positioned at the sprouting tip cells or tethered along the vessel walls.By revealing a novel and fundamental role for NG2(+) glia, our study brings new perspectives to mechanisms underlying proper vessels network formation in embryonic brains.

View Article: PubMed Central - PubMed

Affiliation: Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland.

ABSTRACT
The NG2(+) glia, also known as polydendrocytes or oligodendrocyte precursor cells, represent a new entity among glial cell populations in the central nervous system. However, the complete repertoire of their roles is not yet identified. The embryonic NG2(+) glia originate from the Nkx2.1(+) progenitors of the ventral telencephalon. Our analysis unravels that, beginning from E12.5 until E16.5, the NG2(+) glia populate the entire dorsal telencephalon. Interestingly, their appearance temporally coincides with the establishment of blood vessel network in the embryonic brain. NG2(+) glia are closely apposed to developing cerebral vessels by being either positioned at the sprouting tip cells or tethered along the vessel walls. Absence of NG2(+) glia drastically affects the vascular development leading to severe reduction of ramifications and connections by E18.5. By revealing a novel and fundamental role for NG2(+) glia, our study brings new perspectives to mechanisms underlying proper vessels network formation in embryonic brains.

No MeSH data available.


Related in: MedlinePlus

Macrophages and tip cells are not affected in Nkx2-1Cre+/Rosa-DTA mice.(A–B) Double immunohistochemistry for Isolectin and Ter119, to visualize erythrocytes, on 250-μm-thick coronal of corpus callosum (CC) and cingulate bundle (CI) sections in wild-type (A1–A4) (n=5) and Nkx2.1-cre+/Rosa-DTA (B1–B4) (n=5) mice at E18.5. In the CC and the CI (B1–B2) of Nkx2.1-cre+/Rosa-DTA mice, the blood vessels have a twisted shape and the erythrocytes are clustered (white arrowheads in B1 and B2) compared to the wild-type vessels that formed a regular network (white arrowheads in A1 and A2). In the CC and the CI of both wild-type (A3–A4) and Nkx2.1-cre+/Rosa-DTA mice (B3–B4), guidepost macrophages labeled by the isolectin (white arrowheads in A3–A4 and B3–B4) are found in the close vicinity of the tip cells (white arrows in A3–A4 and B3–B4). The tip cells exhibit the same morphology and the same number of filopodia with similar length in both circumstances. Bar = 60 μm in A1, B1; 40 μm in A2, B2, A3, A4, B3, B4.DOI:http://dx.doi.org/10.7554/eLife.09102.017
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fig6: Macrophages and tip cells are not affected in Nkx2-1Cre+/Rosa-DTA mice.(A–B) Double immunohistochemistry for Isolectin and Ter119, to visualize erythrocytes, on 250-μm-thick coronal of corpus callosum (CC) and cingulate bundle (CI) sections in wild-type (A1–A4) (n=5) and Nkx2.1-cre+/Rosa-DTA (B1–B4) (n=5) mice at E18.5. In the CC and the CI (B1–B2) of Nkx2.1-cre+/Rosa-DTA mice, the blood vessels have a twisted shape and the erythrocytes are clustered (white arrowheads in B1 and B2) compared to the wild-type vessels that formed a regular network (white arrowheads in A1 and A2). In the CC and the CI of both wild-type (A3–A4) and Nkx2.1-cre+/Rosa-DTA mice (B3–B4), guidepost macrophages labeled by the isolectin (white arrowheads in A3–A4 and B3–B4) are found in the close vicinity of the tip cells (white arrows in A3–A4 and B3–B4). The tip cells exhibit the same morphology and the same number of filopodia with similar length in both circumstances. Bar = 60 μm in A1, B1; 40 μm in A2, B2, A3, A4, B3, B4.DOI:http://dx.doi.org/10.7554/eLife.09102.017

Mentions: Remarkably, we observed that vessels stained for vessel markers (NG2, PECAM or Isolectin) formed a poorly developed vascular network in multiple telencephalic regions, such as the septum and the cerebral cortices of Nkx2.1-cre+/Rosa-DTA mice (n=4 for PECAM at E14.5 and E16.5; n=3 for NG2; n=4 for PECAM; n=5 for isolectin at E18.5) compared to WT mice (n=4 for PECAM at E14.5 and E16.5, n=6 for NG2; n=8 for PECAM; n= 5 for isolectin at E18.5) as soon as E16.5 and becoming fully evident by E18.5 in all the rostrocaudal levels (Figure 4B, Figure 5B, Figure 6B, Figure 5—figure supplement 1D and Figure 5—figure supplement 2B). No defects were visualized prior to E16.5 (Figure 5—figure supplement 1B). Cortical vessels of Nkx2.1-cre+/Rosa-DTA mice exhibited a drastic and significant reduction of intersections (nodes), connections and of the density of the vascular network (reduction of nodes: 14.1 ± 4.8% , p<0.05; reduction of branches: 14.7 ± 4.9% , p<0.05; reduction of the total volume of the vascular network: 17.78 ± 4.33% , p<0.05; Figure 5B,G and Table 1; n=4; unpaired Student’s t-test). Due to the defects observed in branching pattern and connectivity, the regular vascular pattern was not observed any more in mutants, and vessels formed only isolated units (Figure 5B and Figure 5—figure supplement 1D). After co-staining for Isolectin and lymphocyte antigen LY-76 marker (Ter119) (Figure 6) and DAB staining allowing the visualization of erythrocytes (Figure 5), our analyses revealed that, in addition, cortical vessels lost their regular diameter and erythrocytes accumulated at the level of enlarged vessel segments (Figure 5E and 5H, Figure 6B and Table 2; n=5; unpaired Student’s t-test). These results are strongly suggestive of brain vessel dysfunction in the mutant mice. Finally, observations made at high magnification after Isolectin and F4/80 staining in both mutant mice did not reveal any defect in tip cell induction and in macrophage recruitment, two processes required for vessels anastomosis (Adams and Alitalo, 2007; Fantin et al., 2010) (Figure 6B and not shown). Quantifications revealed that the number of macrophages was not altered in the Nkx2.1-cre+/Rosa-DTA mice compared to control mice, excluding the direct involvement of macrophages in generating the observed defects (not shown).10.7554/eLife.09102.012Figure 5.Blood vessel branching is similarly impaired in Nkx2.1Cre+/Rosa-DTA and Cspg4-cre+/Rosa-DTA mice.


NG2 glia are required for vessel network formation during embryonic development.

Minocha S, Valloton D, Brunet I, Eichmann A, Hornung JP, Lebrand C - Elife (2015)

Macrophages and tip cells are not affected in Nkx2-1Cre+/Rosa-DTA mice.(A–B) Double immunohistochemistry for Isolectin and Ter119, to visualize erythrocytes, on 250-μm-thick coronal of corpus callosum (CC) and cingulate bundle (CI) sections in wild-type (A1–A4) (n=5) and Nkx2.1-cre+/Rosa-DTA (B1–B4) (n=5) mice at E18.5. In the CC and the CI (B1–B2) of Nkx2.1-cre+/Rosa-DTA mice, the blood vessels have a twisted shape and the erythrocytes are clustered (white arrowheads in B1 and B2) compared to the wild-type vessels that formed a regular network (white arrowheads in A1 and A2). In the CC and the CI of both wild-type (A3–A4) and Nkx2.1-cre+/Rosa-DTA mice (B3–B4), guidepost macrophages labeled by the isolectin (white arrowheads in A3–A4 and B3–B4) are found in the close vicinity of the tip cells (white arrows in A3–A4 and B3–B4). The tip cells exhibit the same morphology and the same number of filopodia with similar length in both circumstances. Bar = 60 μm in A1, B1; 40 μm in A2, B2, A3, A4, B3, B4.DOI:http://dx.doi.org/10.7554/eLife.09102.017
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Related In: Results  -  Collection

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fig6: Macrophages and tip cells are not affected in Nkx2-1Cre+/Rosa-DTA mice.(A–B) Double immunohistochemistry for Isolectin and Ter119, to visualize erythrocytes, on 250-μm-thick coronal of corpus callosum (CC) and cingulate bundle (CI) sections in wild-type (A1–A4) (n=5) and Nkx2.1-cre+/Rosa-DTA (B1–B4) (n=5) mice at E18.5. In the CC and the CI (B1–B2) of Nkx2.1-cre+/Rosa-DTA mice, the blood vessels have a twisted shape and the erythrocytes are clustered (white arrowheads in B1 and B2) compared to the wild-type vessels that formed a regular network (white arrowheads in A1 and A2). In the CC and the CI of both wild-type (A3–A4) and Nkx2.1-cre+/Rosa-DTA mice (B3–B4), guidepost macrophages labeled by the isolectin (white arrowheads in A3–A4 and B3–B4) are found in the close vicinity of the tip cells (white arrows in A3–A4 and B3–B4). The tip cells exhibit the same morphology and the same number of filopodia with similar length in both circumstances. Bar = 60 μm in A1, B1; 40 μm in A2, B2, A3, A4, B3, B4.DOI:http://dx.doi.org/10.7554/eLife.09102.017
Mentions: Remarkably, we observed that vessels stained for vessel markers (NG2, PECAM or Isolectin) formed a poorly developed vascular network in multiple telencephalic regions, such as the septum and the cerebral cortices of Nkx2.1-cre+/Rosa-DTA mice (n=4 for PECAM at E14.5 and E16.5; n=3 for NG2; n=4 for PECAM; n=5 for isolectin at E18.5) compared to WT mice (n=4 for PECAM at E14.5 and E16.5, n=6 for NG2; n=8 for PECAM; n= 5 for isolectin at E18.5) as soon as E16.5 and becoming fully evident by E18.5 in all the rostrocaudal levels (Figure 4B, Figure 5B, Figure 6B, Figure 5—figure supplement 1D and Figure 5—figure supplement 2B). No defects were visualized prior to E16.5 (Figure 5—figure supplement 1B). Cortical vessels of Nkx2.1-cre+/Rosa-DTA mice exhibited a drastic and significant reduction of intersections (nodes), connections and of the density of the vascular network (reduction of nodes: 14.1 ± 4.8% , p<0.05; reduction of branches: 14.7 ± 4.9% , p<0.05; reduction of the total volume of the vascular network: 17.78 ± 4.33% , p<0.05; Figure 5B,G and Table 1; n=4; unpaired Student’s t-test). Due to the defects observed in branching pattern and connectivity, the regular vascular pattern was not observed any more in mutants, and vessels formed only isolated units (Figure 5B and Figure 5—figure supplement 1D). After co-staining for Isolectin and lymphocyte antigen LY-76 marker (Ter119) (Figure 6) and DAB staining allowing the visualization of erythrocytes (Figure 5), our analyses revealed that, in addition, cortical vessels lost their regular diameter and erythrocytes accumulated at the level of enlarged vessel segments (Figure 5E and 5H, Figure 6B and Table 2; n=5; unpaired Student’s t-test). These results are strongly suggestive of brain vessel dysfunction in the mutant mice. Finally, observations made at high magnification after Isolectin and F4/80 staining in both mutant mice did not reveal any defect in tip cell induction and in macrophage recruitment, two processes required for vessels anastomosis (Adams and Alitalo, 2007; Fantin et al., 2010) (Figure 6B and not shown). Quantifications revealed that the number of macrophages was not altered in the Nkx2.1-cre+/Rosa-DTA mice compared to control mice, excluding the direct involvement of macrophages in generating the observed defects (not shown).10.7554/eLife.09102.012Figure 5.Blood vessel branching is similarly impaired in Nkx2.1Cre+/Rosa-DTA and Cspg4-cre+/Rosa-DTA mice.

Bottom Line: Interestingly, their appearance temporally coincides with the establishment of blood vessel network in the embryonic brain.NG2(+) glia are closely apposed to developing cerebral vessels by being either positioned at the sprouting tip cells or tethered along the vessel walls.By revealing a novel and fundamental role for NG2(+) glia, our study brings new perspectives to mechanisms underlying proper vessels network formation in embryonic brains.

View Article: PubMed Central - PubMed

Affiliation: Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland.

ABSTRACT
The NG2(+) glia, also known as polydendrocytes or oligodendrocyte precursor cells, represent a new entity among glial cell populations in the central nervous system. However, the complete repertoire of their roles is not yet identified. The embryonic NG2(+) glia originate from the Nkx2.1(+) progenitors of the ventral telencephalon. Our analysis unravels that, beginning from E12.5 until E16.5, the NG2(+) glia populate the entire dorsal telencephalon. Interestingly, their appearance temporally coincides with the establishment of blood vessel network in the embryonic brain. NG2(+) glia are closely apposed to developing cerebral vessels by being either positioned at the sprouting tip cells or tethered along the vessel walls. Absence of NG2(+) glia drastically affects the vascular development leading to severe reduction of ramifications and connections by E18.5. By revealing a novel and fundamental role for NG2(+) glia, our study brings new perspectives to mechanisms underlying proper vessels network formation in embryonic brains.

No MeSH data available.


Related in: MedlinePlus