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HOXA13 Is essential for placental vascular patterning and labyrinth endothelial specification.

Shaut CA, Keene DR, Sorensen LK, Li DY, Stadler HS - PLoS Genet. (2008)

Bottom Line: Notably, pro-vascular genes, including Tie2 and Foxf1, exhibited reduced expression in the mutant endothelia, which also exhibited elevated expression of genes normally expressed in lymphatic or sinusoidal endothelia.ChIP analysis of HOXA13-DNA complexes in the placenta confirmed that HOXA13 binds the Tie2 and Foxf1 promoters in vivo.Taken together, these findings demonstrate that HOXA13 directly regulates Tie2 and Foxf1 in the placental labyrinth endothelia, providing a functional explanation for the mid-gestational lethality exhibited by Hoxa13 mutant embryos as well as a novel transcriptional program necessary for the specification of the labyrinth vascular endothelia.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, United States of America.

ABSTRACT
In eutherian mammals, embryonic growth and survival is dependent on the formation of the placenta, an organ that facilitates the efficient exchange of oxygen, nutrients, and metabolic waste between the maternal and fetal blood supplies. Key to the placenta's function is the formation of its vascular labyrinth, a series of finely branched vessels whose molecular ontogeny remains largely undefined. In this report, we demonstrate that HOXA13 plays an essential role in labyrinth vessel formation. In the absence of HOXA13 function, placental endothelial cell morphology is altered, causing a loss in vessel wall integrity, edema of the embryonic blood vessels, and mid-gestational lethality. Microarray analysis of wild-type and mutant placentas revealed significant changes in endothelial gene expression profiles. Notably, pro-vascular genes, including Tie2 and Foxf1, exhibited reduced expression in the mutant endothelia, which also exhibited elevated expression of genes normally expressed in lymphatic or sinusoidal endothelia. ChIP analysis of HOXA13-DNA complexes in the placenta confirmed that HOXA13 binds the Tie2 and Foxf1 promoters in vivo. In vitro, HOXA13 binds sequences present in the Tie2 and Foxf1 promoters with high affinity (K(d) = 27-42 nM) and HOXA13 can use these bound promoter regions to direct gene expression. Taken together, these findings demonstrate that HOXA13 directly regulates Tie2 and Foxf1 in the placental labyrinth endothelia, providing a functional explanation for the mid-gestational lethality exhibited by Hoxa13 mutant embryos as well as a novel transcriptional program necessary for the specification of the labyrinth vascular endothelia.

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Labyrinth vessel branching is reduced in Hoxa13 homozygous mutants.(A–D) PECAM-1 immunostaining of E13.5 hemisected placentas revealed extensive branching of the primary labyrinth vessel in wild-type and heterozygous mutants, whereas homozygous mutant littermates exhibited poor branching of the primary labyrinth vessels (E, F). (G) Quantitation of the labyrinth vascular branches confirmed that the homozygous mutants labyrinths contained an average of 33 branches per 400 mm2 grid, whereas wild-type and heterozygous mutant controls contained an average of 56 and 55 branches, respectively, in the same unit area. Bars represent the standard deviation of six independent assessments.
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pgen-1000073-g005: Labyrinth vessel branching is reduced in Hoxa13 homozygous mutants.(A–D) PECAM-1 immunostaining of E13.5 hemisected placentas revealed extensive branching of the primary labyrinth vessel in wild-type and heterozygous mutants, whereas homozygous mutant littermates exhibited poor branching of the primary labyrinth vessels (E, F). (G) Quantitation of the labyrinth vascular branches confirmed that the homozygous mutants labyrinths contained an average of 33 branches per 400 mm2 grid, whereas wild-type and heterozygous mutant controls contained an average of 56 and 55 branches, respectively, in the same unit area. Bars represent the standard deviation of six independent assessments.

Mentions: Indeed, while the initial vascular invasion of the chorionic plate at E10.5 appears normal in Hoxa13 homozygous mutants, there is a qualitative reduction in the level of PECAM-1 staining of the labyrinth vasculature as early as E11.5 (Figure S1). Quantitation of the vascular branches in the mutant and control placental labyrinths at E13.5 confirmed that the number of branches is reduced in the Hoxa13 homozygous mutants which exhibited 33 (±6.3) branches per 400 mm2 grid analyzed, whereas wild type and heterozygous mutant controls contained 56 (±12.7) and 55 (±9.7) vessel branches respectively (Figure 5). Qualitatively, the reduction in labyrinth vascularity in homozygous mutants was persistent throughout labyrinth development which is complete by E14.5, suggesting that decreased vessel branching is phenotypic of the loss of HOXA13 function rather than a delay in the labyrinth maturation (Figures 3, 5, and S1) [48]. Next, because changes in vessel branching can also affect the overall size of the labyrinth, we examined whether the labyrinth region was smaller in Hoxa13 mutant placentas. Analysis of labyrinth sections taken from E13.5 wild type and Hoxa13 homozygous mutants confirmed that the mutant labyrinths were nearly half the thickness as their age-matched controls (800±200 µm vs. 1600±250 µm) (Figure 6).


HOXA13 Is essential for placental vascular patterning and labyrinth endothelial specification.

Shaut CA, Keene DR, Sorensen LK, Li DY, Stadler HS - PLoS Genet. (2008)

Labyrinth vessel branching is reduced in Hoxa13 homozygous mutants.(A–D) PECAM-1 immunostaining of E13.5 hemisected placentas revealed extensive branching of the primary labyrinth vessel in wild-type and heterozygous mutants, whereas homozygous mutant littermates exhibited poor branching of the primary labyrinth vessels (E, F). (G) Quantitation of the labyrinth vascular branches confirmed that the homozygous mutants labyrinths contained an average of 33 branches per 400 mm2 grid, whereas wild-type and heterozygous mutant controls contained an average of 56 and 55 branches, respectively, in the same unit area. Bars represent the standard deviation of six independent assessments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2367452&req=5

pgen-1000073-g005: Labyrinth vessel branching is reduced in Hoxa13 homozygous mutants.(A–D) PECAM-1 immunostaining of E13.5 hemisected placentas revealed extensive branching of the primary labyrinth vessel in wild-type and heterozygous mutants, whereas homozygous mutant littermates exhibited poor branching of the primary labyrinth vessels (E, F). (G) Quantitation of the labyrinth vascular branches confirmed that the homozygous mutants labyrinths contained an average of 33 branches per 400 mm2 grid, whereas wild-type and heterozygous mutant controls contained an average of 56 and 55 branches, respectively, in the same unit area. Bars represent the standard deviation of six independent assessments.
Mentions: Indeed, while the initial vascular invasion of the chorionic plate at E10.5 appears normal in Hoxa13 homozygous mutants, there is a qualitative reduction in the level of PECAM-1 staining of the labyrinth vasculature as early as E11.5 (Figure S1). Quantitation of the vascular branches in the mutant and control placental labyrinths at E13.5 confirmed that the number of branches is reduced in the Hoxa13 homozygous mutants which exhibited 33 (±6.3) branches per 400 mm2 grid analyzed, whereas wild type and heterozygous mutant controls contained 56 (±12.7) and 55 (±9.7) vessel branches respectively (Figure 5). Qualitatively, the reduction in labyrinth vascularity in homozygous mutants was persistent throughout labyrinth development which is complete by E14.5, suggesting that decreased vessel branching is phenotypic of the loss of HOXA13 function rather than a delay in the labyrinth maturation (Figures 3, 5, and S1) [48]. Next, because changes in vessel branching can also affect the overall size of the labyrinth, we examined whether the labyrinth region was smaller in Hoxa13 mutant placentas. Analysis of labyrinth sections taken from E13.5 wild type and Hoxa13 homozygous mutants confirmed that the mutant labyrinths were nearly half the thickness as their age-matched controls (800±200 µm vs. 1600±250 µm) (Figure 6).

Bottom Line: Notably, pro-vascular genes, including Tie2 and Foxf1, exhibited reduced expression in the mutant endothelia, which also exhibited elevated expression of genes normally expressed in lymphatic or sinusoidal endothelia.ChIP analysis of HOXA13-DNA complexes in the placenta confirmed that HOXA13 binds the Tie2 and Foxf1 promoters in vivo.Taken together, these findings demonstrate that HOXA13 directly regulates Tie2 and Foxf1 in the placental labyrinth endothelia, providing a functional explanation for the mid-gestational lethality exhibited by Hoxa13 mutant embryos as well as a novel transcriptional program necessary for the specification of the labyrinth vascular endothelia.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, United States of America.

ABSTRACT
In eutherian mammals, embryonic growth and survival is dependent on the formation of the placenta, an organ that facilitates the efficient exchange of oxygen, nutrients, and metabolic waste between the maternal and fetal blood supplies. Key to the placenta's function is the formation of its vascular labyrinth, a series of finely branched vessels whose molecular ontogeny remains largely undefined. In this report, we demonstrate that HOXA13 plays an essential role in labyrinth vessel formation. In the absence of HOXA13 function, placental endothelial cell morphology is altered, causing a loss in vessel wall integrity, edema of the embryonic blood vessels, and mid-gestational lethality. Microarray analysis of wild-type and mutant placentas revealed significant changes in endothelial gene expression profiles. Notably, pro-vascular genes, including Tie2 and Foxf1, exhibited reduced expression in the mutant endothelia, which also exhibited elevated expression of genes normally expressed in lymphatic or sinusoidal endothelia. ChIP analysis of HOXA13-DNA complexes in the placenta confirmed that HOXA13 binds the Tie2 and Foxf1 promoters in vivo. In vitro, HOXA13 binds sequences present in the Tie2 and Foxf1 promoters with high affinity (K(d) = 27-42 nM) and HOXA13 can use these bound promoter regions to direct gene expression. Taken together, these findings demonstrate that HOXA13 directly regulates Tie2 and Foxf1 in the placental labyrinth endothelia, providing a functional explanation for the mid-gestational lethality exhibited by Hoxa13 mutant embryos as well as a novel transcriptional program necessary for the specification of the labyrinth vascular endothelia.

Show MeSH
Related in: MedlinePlus