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Erg is a crucial regulator of endocardial-mesenchymal transformation during cardiac valve morphogenesis.

Vijayaraj P, Le Bras A, Mitchell N, Kondo M, Juliao S, Wasserman M, Beeler D, Spokes K, Aird WC, Baldwin HS, Oettgen P - Development (2012)

Bottom Line: Four share a common translational start site encoded by exon 3 (Ex3) and are enriched in chondrocytes.The other three have a separate translational start site encoded by Ex4 and are enriched in endothelial cells.We show that Erg is required for the maintenance of the core EnMT regulatory factors that include Snail1 and Snail2 by binding to their promoter and intronic regions.

View Article: PubMed Central - PubMed

Affiliation: Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.

ABSTRACT
During murine embryogenesis, the Ets factor Erg is highly expressed in endothelial cells of the developing vasculature and in articular chondrocytes of developing bone. We identified seven isoforms for the mouse Erg gene. Four share a common translational start site encoded by exon 3 (Ex3) and are enriched in chondrocytes. The other three have a separate translational start site encoded by Ex4 and are enriched in endothelial cells. Homozygous Erg(ΔEx3/ΔEx3) knockout mice are viable, fertile and do not display any overt phenotype. By contrast, homozygous Erg(ΔEx4/ΔEx4) knockout mice are embryonic lethal, which is associated with a marked reduction in endocardial-mesenchymal transformation (EnMT) during cardiac valve morphogenesis. We show that Erg is required for the maintenance of the core EnMT regulatory factors that include Snail1 and Snail2 by binding to their promoter and intronic regions.

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lacZ expression pattern during development of ErgΔEx3/+ and ErgΔEx4/+ mouse embryos. (A) lacZ staining corresponding to ErgEx3 was observed in the somites and limbs corresponding to developing articular cartilage starting at E9.5. By contrast, ErgEx4 expression was detected in the blood islands at E7.5 and then in all embryonic vasculature. (B,D,F) lacZ staining of whole-mount preparations of the head (B), heart (D) and somites (F) from E10.5 embryos displaying a clear endothelial restricted pattern in the brain vasculature, endocardium and intersomitic vessels, respectively. (C,E,G) lacZ staining of sectioned E10.5 embryos. lacZ-positive cells are seen in the vitelline artery (C), endocardium of the heart (E) and in ECs lining the dorsal aorta (G).
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Figure 3: lacZ expression pattern during development of ErgΔEx3/+ and ErgΔEx4/+ mouse embryos. (A) lacZ staining corresponding to ErgEx3 was observed in the somites and limbs corresponding to developing articular cartilage starting at E9.5. By contrast, ErgEx4 expression was detected in the blood islands at E7.5 and then in all embryonic vasculature. (B,D,F) lacZ staining of whole-mount preparations of the head (B), heart (D) and somites (F) from E10.5 embryos displaying a clear endothelial restricted pattern in the brain vasculature, endocardium and intersomitic vessels, respectively. (C,E,G) lacZ staining of sectioned E10.5 embryos. lacZ-positive cells are seen in the vitelline artery (C), endocardium of the heart (E) and in ECs lining the dorsal aorta (G).

Mentions: To further define the role of exon 3- and exon 4-specific isoforms during development, we generated ErgΔEx3/ΔEx3 and ErgΔEx4/ΔEx4 knockout mice using standard gene targeting strategies. In brief, we designed a targeting vector to replace either the ATG of exon 3 or exon 4 with a lacZ-Neo cassette (Fig. 2A,C). Targeting of these exons blocks protein expression of Erg isoforms 1-4 and 5-7, respectively, which is replaced by expression of lacZ. Mouse ES cells were transfected with the linearized targeting vectors and neomycin-resistant ES cell clones were picked and screened. Successful homologous recombination was verified by PCR and Southern blot analysis (Fig. 2B,D). ErgΔEx3/+ and ErgΔEx4/+ ES cells were used to produce ErgΔEx3/+ and ErgΔEx4/+ heterozygous knockout mice, respectively. lacZ staining was first observed in the ErgΔEx3/+ mice at E9.5 and in ErgΔEx4/+ mice at E7.5 (Fig. 3A).


Erg is a crucial regulator of endocardial-mesenchymal transformation during cardiac valve morphogenesis.

Vijayaraj P, Le Bras A, Mitchell N, Kondo M, Juliao S, Wasserman M, Beeler D, Spokes K, Aird WC, Baldwin HS, Oettgen P - Development (2012)

lacZ expression pattern during development of ErgΔEx3/+ and ErgΔEx4/+ mouse embryos. (A) lacZ staining corresponding to ErgEx3 was observed in the somites and limbs corresponding to developing articular cartilage starting at E9.5. By contrast, ErgEx4 expression was detected in the blood islands at E7.5 and then in all embryonic vasculature. (B,D,F) lacZ staining of whole-mount preparations of the head (B), heart (D) and somites (F) from E10.5 embryos displaying a clear endothelial restricted pattern in the brain vasculature, endocardium and intersomitic vessels, respectively. (C,E,G) lacZ staining of sectioned E10.5 embryos. lacZ-positive cells are seen in the vitelline artery (C), endocardium of the heart (E) and in ECs lining the dorsal aorta (G).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472597&req=5

Figure 3: lacZ expression pattern during development of ErgΔEx3/+ and ErgΔEx4/+ mouse embryos. (A) lacZ staining corresponding to ErgEx3 was observed in the somites and limbs corresponding to developing articular cartilage starting at E9.5. By contrast, ErgEx4 expression was detected in the blood islands at E7.5 and then in all embryonic vasculature. (B,D,F) lacZ staining of whole-mount preparations of the head (B), heart (D) and somites (F) from E10.5 embryos displaying a clear endothelial restricted pattern in the brain vasculature, endocardium and intersomitic vessels, respectively. (C,E,G) lacZ staining of sectioned E10.5 embryos. lacZ-positive cells are seen in the vitelline artery (C), endocardium of the heart (E) and in ECs lining the dorsal aorta (G).
Mentions: To further define the role of exon 3- and exon 4-specific isoforms during development, we generated ErgΔEx3/ΔEx3 and ErgΔEx4/ΔEx4 knockout mice using standard gene targeting strategies. In brief, we designed a targeting vector to replace either the ATG of exon 3 or exon 4 with a lacZ-Neo cassette (Fig. 2A,C). Targeting of these exons blocks protein expression of Erg isoforms 1-4 and 5-7, respectively, which is replaced by expression of lacZ. Mouse ES cells were transfected with the linearized targeting vectors and neomycin-resistant ES cell clones were picked and screened. Successful homologous recombination was verified by PCR and Southern blot analysis (Fig. 2B,D). ErgΔEx3/+ and ErgΔEx4/+ ES cells were used to produce ErgΔEx3/+ and ErgΔEx4/+ heterozygous knockout mice, respectively. lacZ staining was first observed in the ErgΔEx3/+ mice at E9.5 and in ErgΔEx4/+ mice at E7.5 (Fig. 3A).

Bottom Line: Four share a common translational start site encoded by exon 3 (Ex3) and are enriched in chondrocytes.The other three have a separate translational start site encoded by Ex4 and are enriched in endothelial cells.We show that Erg is required for the maintenance of the core EnMT regulatory factors that include Snail1 and Snail2 by binding to their promoter and intronic regions.

View Article: PubMed Central - PubMed

Affiliation: Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.

ABSTRACT
During murine embryogenesis, the Ets factor Erg is highly expressed in endothelial cells of the developing vasculature and in articular chondrocytes of developing bone. We identified seven isoforms for the mouse Erg gene. Four share a common translational start site encoded by exon 3 (Ex3) and are enriched in chondrocytes. The other three have a separate translational start site encoded by Ex4 and are enriched in endothelial cells. Homozygous Erg(ΔEx3/ΔEx3) knockout mice are viable, fertile and do not display any overt phenotype. By contrast, homozygous Erg(ΔEx4/ΔEx4) knockout mice are embryonic lethal, which is associated with a marked reduction in endocardial-mesenchymal transformation (EnMT) during cardiac valve morphogenesis. We show that Erg is required for the maintenance of the core EnMT regulatory factors that include Snail1 and Snail2 by binding to their promoter and intronic regions.

Show MeSH
Related in: MedlinePlus