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Embryonic vascular endothelial cells are malleable to reprogramming via Prox1 to a lymphatic gene signature.

Kim H, Nguyen VP, Petrova TV, Cruz M, Alitalo K, Dumont DJ - BMC Dev. Biol. (2010)

Bottom Line: Overexpression of Prox1 in vascular endothelial cells during embryonic development results in the reprogramming of genes to that of a more lymphatic signature.Alterations in junctional proteins resulting in an increase in vascular permeability upon Prox1 overexpression may contribute to the complications found during embryonic development.Furthermore, Prox1 reprograms vascular endothelial cells in vivo by creating a molecular signature to that of a lymphatic endothelial cell.

View Article: PubMed Central - HTML - PubMed

Affiliation: Sunnybrook Research Institute University of Toronto 2075 Bayview Avenue Toronto, Ontario M4N 3M5, Canada. dan.dumont@sri.utoronto.ca

ABSTRACT

Background: In vivo studies demonstrate that the Prox1 transcription factor plays a critical role in the development of the early lymphatic system. Upon Prox1 expression, early lymphatic endothelial cells differentiate from the cardinal vein and begin to express lymphatic markers such as VEGFR-3, LYVE-1 and Podoplanin. Subsequent in vitro studies have found that differentiated vascular endothelial cells can be reprogrammed by Prox1 to express a lymphatic gene profile, suggesting that Prox1 can initiate the expression of a unique gene signature during lymphangiogenesis. While the in vitro data suggest that gene reprogramming occurs upon Prox1 expression, it is not clear if this is a direct result of Prox1 in vascular endothelial cells in vivo.

Results: Overexpression of Prox1 in vascular endothelial cells during embryonic development results in the reprogramming of genes to that of a more lymphatic signature. Consequent to this overexpression, embryos suffer from gross edema that results in embryonic lethality at E13.5. Furthermore, hemorrhaging and anemia is apparent along with clear defects in lymph sac development. Alterations in junctional proteins resulting in an increase in vascular permeability upon Prox1 overexpression may contribute to the complications found during embryonic development.

Conclusion: We present a novel mouse model that addresses the importance of Prox1 in early embryonic lymphangiogenesis. It is clear that there needs to be a measured pattern of expression of Prox1 during embryonic development. Furthermore, Prox1 reprograms vascular endothelial cells in vivo by creating a molecular signature to that of a lymphatic endothelial cell.

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Bigenic model for Prox1 overexpression. (A) The prox1:tetOS transgene is driven by the tissue specific tie1:tTA promoter. Open circle: tTA, closed circle: Prox1 protein. (B) The expression of Prox1 in E10.5 embryos displays a polarized expression pattern specifically from the cardinal vein. (C) In contrast, overexpression of Prox1 in the double transgenic (DT) embryos display an increase in Prox1 positive cells from the cardinal vein. Significantly, Prox1 is also present on the dorsal aorta, which is normally negative for Prox1 expression. Orientation arrows for B and C: D- Dorsal, L- Lateral. Scale bar: 50 μm.
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Figure 1: Bigenic model for Prox1 overexpression. (A) The prox1:tetOS transgene is driven by the tissue specific tie1:tTA promoter. Open circle: tTA, closed circle: Prox1 protein. (B) The expression of Prox1 in E10.5 embryos displays a polarized expression pattern specifically from the cardinal vein. (C) In contrast, overexpression of Prox1 in the double transgenic (DT) embryos display an increase in Prox1 positive cells from the cardinal vein. Significantly, Prox1 is also present on the dorsal aorta, which is normally negative for Prox1 expression. Orientation arrows for B and C: D- Dorsal, L- Lateral. Scale bar: 50 μm.

Mentions: In order to investigate whether Prox1 is necessary and sufficient in regulating cell fate, we have generated a mouse model that forces the expression of Prox1 specifically in vascular endothelial cells. Our transgenic model takes advantage of a bigenic expression system driven by the tie1 promoter (Figure 1a). This model results in targeted expression within vascular compartments such as the cardinal vein as well as the dorsal aorta (Figure 1b and 1c, see Additional file 1). While the expression of Prox1 in DT embryos is also found on both arteries and veins, both these vascular structures appear to differentially overexpress Prox-1 throughout development in our model suggesting that arterial and venous endothelial cells may regulate Prox-1 RNA/protein levels in a different fashion. While the directionality of the budding lymphatic endothelial cells appear to be more tightly regulated in control embryos, DT embryos appear to display more Prox1 positive cells in the periphery. These results suggest that normally, Prox1 expression and lymphatic endothelial cell budding are tightly controlled and can be disrupted by the overexpression of Prox1 in the developing vasculature.


Embryonic vascular endothelial cells are malleable to reprogramming via Prox1 to a lymphatic gene signature.

Kim H, Nguyen VP, Petrova TV, Cruz M, Alitalo K, Dumont DJ - BMC Dev. Biol. (2010)

Bigenic model for Prox1 overexpression. (A) The prox1:tetOS transgene is driven by the tissue specific tie1:tTA promoter. Open circle: tTA, closed circle: Prox1 protein. (B) The expression of Prox1 in E10.5 embryos displays a polarized expression pattern specifically from the cardinal vein. (C) In contrast, overexpression of Prox1 in the double transgenic (DT) embryos display an increase in Prox1 positive cells from the cardinal vein. Significantly, Prox1 is also present on the dorsal aorta, which is normally negative for Prox1 expression. Orientation arrows for B and C: D- Dorsal, L- Lateral. Scale bar: 50 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2909156&req=5

Figure 1: Bigenic model for Prox1 overexpression. (A) The prox1:tetOS transgene is driven by the tissue specific tie1:tTA promoter. Open circle: tTA, closed circle: Prox1 protein. (B) The expression of Prox1 in E10.5 embryos displays a polarized expression pattern specifically from the cardinal vein. (C) In contrast, overexpression of Prox1 in the double transgenic (DT) embryos display an increase in Prox1 positive cells from the cardinal vein. Significantly, Prox1 is also present on the dorsal aorta, which is normally negative for Prox1 expression. Orientation arrows for B and C: D- Dorsal, L- Lateral. Scale bar: 50 μm.
Mentions: In order to investigate whether Prox1 is necessary and sufficient in regulating cell fate, we have generated a mouse model that forces the expression of Prox1 specifically in vascular endothelial cells. Our transgenic model takes advantage of a bigenic expression system driven by the tie1 promoter (Figure 1a). This model results in targeted expression within vascular compartments such as the cardinal vein as well as the dorsal aorta (Figure 1b and 1c, see Additional file 1). While the expression of Prox1 in DT embryos is also found on both arteries and veins, both these vascular structures appear to differentially overexpress Prox-1 throughout development in our model suggesting that arterial and venous endothelial cells may regulate Prox-1 RNA/protein levels in a different fashion. While the directionality of the budding lymphatic endothelial cells appear to be more tightly regulated in control embryos, DT embryos appear to display more Prox1 positive cells in the periphery. These results suggest that normally, Prox1 expression and lymphatic endothelial cell budding are tightly controlled and can be disrupted by the overexpression of Prox1 in the developing vasculature.

Bottom Line: Overexpression of Prox1 in vascular endothelial cells during embryonic development results in the reprogramming of genes to that of a more lymphatic signature.Alterations in junctional proteins resulting in an increase in vascular permeability upon Prox1 overexpression may contribute to the complications found during embryonic development.Furthermore, Prox1 reprograms vascular endothelial cells in vivo by creating a molecular signature to that of a lymphatic endothelial cell.

View Article: PubMed Central - HTML - PubMed

Affiliation: Sunnybrook Research Institute University of Toronto 2075 Bayview Avenue Toronto, Ontario M4N 3M5, Canada. dan.dumont@sri.utoronto.ca

ABSTRACT

Background: In vivo studies demonstrate that the Prox1 transcription factor plays a critical role in the development of the early lymphatic system. Upon Prox1 expression, early lymphatic endothelial cells differentiate from the cardinal vein and begin to express lymphatic markers such as VEGFR-3, LYVE-1 and Podoplanin. Subsequent in vitro studies have found that differentiated vascular endothelial cells can be reprogrammed by Prox1 to express a lymphatic gene profile, suggesting that Prox1 can initiate the expression of a unique gene signature during lymphangiogenesis. While the in vitro data suggest that gene reprogramming occurs upon Prox1 expression, it is not clear if this is a direct result of Prox1 in vascular endothelial cells in vivo.

Results: Overexpression of Prox1 in vascular endothelial cells during embryonic development results in the reprogramming of genes to that of a more lymphatic signature. Consequent to this overexpression, embryos suffer from gross edema that results in embryonic lethality at E13.5. Furthermore, hemorrhaging and anemia is apparent along with clear defects in lymph sac development. Alterations in junctional proteins resulting in an increase in vascular permeability upon Prox1 overexpression may contribute to the complications found during embryonic development.

Conclusion: We present a novel mouse model that addresses the importance of Prox1 in early embryonic lymphangiogenesis. It is clear that there needs to be a measured pattern of expression of Prox1 during embryonic development. Furthermore, Prox1 reprograms vascular endothelial cells in vivo by creating a molecular signature to that of a lymphatic endothelial cell.

Show MeSH
Related in: MedlinePlus