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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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Analysis of ventricular wall thickness in Hoxa13 mutants.(A, B) Analysis of hematoxylin and eosin–stained sections (7 µm) from heterozygous control and homozygous mutant hearts at E14.5 embryos reveal qualitatively thicker ventricular walls in the heterozygous control embryos. RV = right ventricle; LV = left ventricle. Boxes represent the enlarged regions shown in (C) and (D). (C, D) Quantitative analysis of the left ventricular wall thicknesses revealed homozygous mutants possess an average of 3.6 (±1.1) cells per linear assessment versus 6.3 (±0.8) cells in heterozygous controls, confirming that the E14.5 Hoxa13 homozygous mutants possess a thinner left ventricular wall compared to age-matched heterozygous controls. White arrows depict the sites assessed for ventricular wall thickness using the hematoxylin-stained nuclei to determine cell number. The measurements were taken from the trabecular wall (T) to the outer ventricular wall (VW) for each assessment.
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pgen-1000073-g008: Analysis of ventricular wall thickness in Hoxa13 mutants.(A, B) Analysis of hematoxylin and eosin–stained sections (7 µm) from heterozygous control and homozygous mutant hearts at E14.5 embryos reveal qualitatively thicker ventricular walls in the heterozygous control embryos. RV = right ventricle; LV = left ventricle. Boxes represent the enlarged regions shown in (C) and (D). (C, D) Quantitative analysis of the left ventricular wall thicknesses revealed homozygous mutants possess an average of 3.6 (±1.1) cells per linear assessment versus 6.3 (±0.8) cells in heterozygous controls, confirming that the E14.5 Hoxa13 homozygous mutants possess a thinner left ventricular wall compared to age-matched heterozygous controls. White arrows depict the sites assessed for ventricular wall thickness using the hematoxylin-stained nuclei to determine cell number. The measurements were taken from the trabecular wall (T) to the outer ventricular wall (VW) for each assessment.

Mentions: Taken together, these results suggest that placental insufficiency caused by decreased labyrinth vascularity and size may be causing the mid-gestational lethality associated with the loss of HOXA13 function. To test this hypothesis we examined the developing heart, an organ that does not express Hoxa13 but is severely affected by placental insufficiency [28], [29], [49]–[53]. Analysis of E14.5 hearts from heterozygous control and homozygous mutants revealed a substantial thinning of the right and left ventricular walls in homozygous mutants (Figure 8). Quantitation of the left ventricular wall thicknesses confirmed nearly a 43% reduction in wall thicknesses in homozygous mutants which contained an average of 3.6 (±1.1) cells per wall section measurement versus 6.3 (±0.8) cells in the comparable sections of age-matched heterozygous controls (Figure 8C and 4D).


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

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

Analysis of ventricular wall thickness in Hoxa13 mutants.(A, B) Analysis of hematoxylin and eosin–stained sections (7 µm) from heterozygous control and homozygous mutant hearts at E14.5 embryos reveal qualitatively thicker ventricular walls in the heterozygous control embryos. RV = right ventricle; LV = left ventricle. Boxes represent the enlarged regions shown in (C) and (D). (C, D) Quantitative analysis of the left ventricular wall thicknesses revealed homozygous mutants possess an average of 3.6 (±1.1) cells per linear assessment versus 6.3 (±0.8) cells in heterozygous controls, confirming that the E14.5 Hoxa13 homozygous mutants possess a thinner left ventricular wall compared to age-matched heterozygous controls. White arrows depict the sites assessed for ventricular wall thickness using the hematoxylin-stained nuclei to determine cell number. The measurements were taken from the trabecular wall (T) to the outer ventricular wall (VW) for each assessment.
© Copyright Policy
Related In: Results  -  Collection

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

pgen-1000073-g008: Analysis of ventricular wall thickness in Hoxa13 mutants.(A, B) Analysis of hematoxylin and eosin–stained sections (7 µm) from heterozygous control and homozygous mutant hearts at E14.5 embryos reveal qualitatively thicker ventricular walls in the heterozygous control embryos. RV = right ventricle; LV = left ventricle. Boxes represent the enlarged regions shown in (C) and (D). (C, D) Quantitative analysis of the left ventricular wall thicknesses revealed homozygous mutants possess an average of 3.6 (±1.1) cells per linear assessment versus 6.3 (±0.8) cells in heterozygous controls, confirming that the E14.5 Hoxa13 homozygous mutants possess a thinner left ventricular wall compared to age-matched heterozygous controls. White arrows depict the sites assessed for ventricular wall thickness using the hematoxylin-stained nuclei to determine cell number. The measurements were taken from the trabecular wall (T) to the outer ventricular wall (VW) for each assessment.
Mentions: Taken together, these results suggest that placental insufficiency caused by decreased labyrinth vascularity and size may be causing the mid-gestational lethality associated with the loss of HOXA13 function. To test this hypothesis we examined the developing heart, an organ that does not express Hoxa13 but is severely affected by placental insufficiency [28], [29], [49]–[53]. Analysis of E14.5 hearts from heterozygous control and homozygous mutants revealed a substantial thinning of the right and left ventricular walls in homozygous mutants (Figure 8). Quantitation of the left ventricular wall thicknesses confirmed nearly a 43% reduction in wall thicknesses in homozygous mutants which contained an average of 3.6 (±1.1) cells per wall section measurement versus 6.3 (±0.8) cells in the comparable sections of age-matched heterozygous controls (Figure 8C and 4D).

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