Effect of endoglin overexpression during embryoid body development

Exp Hematol. 2012 Oct;40(10):837-46. doi: 10.1016/j.exphem.2012.06.007. Epub 2012 Jun 19.

Abstract

Increasing evidence points to endoglin (Eng), an accessory receptor for the transforming growth factor-β superfamily commonly associated with the endothelial lineage, as an important regulator of the hematopoietic lineage. We have shown that lack of Eng results in reduced numbers of primitive erythroid colonies as well as downregulation of key hematopoietic genes. To determine the effect of Eng overexpression in hematopoietic development, we generated a doxycycline-inducible embryonic stem cell line. Our results demonstrate that induction of Eng during embryoid body differentiation leads to a significant increase in the frequency of hematopoietic progenitors, in particular, the erythroid lineage, which correlated with upregulation of Scl, Gata1, Runx1, and embryonic globin. Interestingly, activation of the hematopoietic program happened at the expense of endothelial and cardiac cells, as differentiation into these mesoderm lineages was compromised. Eng-induced enhanced erythroid activity was accompanied by high levels of Smad1 phosphorylation. This effect was attenuated by addition of a bone morphogenetic protein (BMP) signaling inhibitor to these cultures. Among the BMPs, BMP4 is well known for its role in hematopoietic specification from mesoderm by promoting expression of several hematopoietic genes, including Scl. Because Scl is considered the master regulator of the hematopoietic program, we investigated whether Scl would be capable of rescuing the defective hematopoietic phenotype observed in Eng(-/-) embryonic stem cells. Scl expression in Eng-deficient embryonic stem cells resulted in increased erythroid colony-forming activity and upregulation of Gata1 and Gata2, positioning Eng upstream of Scl. Taken together, these findings support the premise that Eng modulates the hematopoietic transcriptional network, most likely through regulation of BMP4 signaling.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Bone Morphogenetic Protein 4 / genetics
  • Bone Morphogenetic Protein 4 / metabolism
  • Cell Differentiation / physiology*
  • Cell Lineage / physiology*
  • Core Binding Factor Alpha 2 Subunit / genetics
  • Core Binding Factor Alpha 2 Subunit / metabolism
  • Embryoid Bodies / cytology
  • Embryoid Bodies / metabolism*
  • Endoglin
  • GATA1 Transcription Factor / genetics
  • GATA1 Transcription Factor / metabolism
  • GATA2 Transcription Factor / genetics
  • GATA2 Transcription Factor / metabolism
  • Gene Expression Regulation / physiology*
  • Gene Expression Regulation, Developmental / physiology*
  • Globins / genetics
  • Globins / metabolism
  • HEK293 Cells
  • Hematopoiesis / physiology*
  • Humans
  • Intracellular Signaling Peptides and Proteins / biosynthesis*
  • Intracellular Signaling Peptides and Proteins / genetics
  • Mice
  • Mice, Knockout
  • Phosphorylation / physiology
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism
  • Signal Transduction / physiology
  • Smad1 Protein / genetics
  • Smad1 Protein / metabolism
  • T-Cell Acute Lymphocytic Leukemia Protein 1

Substances

  • Basic Helix-Loop-Helix Transcription Factors
  • Bmp4 protein, mouse
  • Bone Morphogenetic Protein 4
  • Core Binding Factor Alpha 2 Subunit
  • Endoglin
  • Eng protein, mouse
  • GATA1 Transcription Factor
  • GATA2 Transcription Factor
  • Gata1 protein, mouse
  • Gata2 protein, mouse
  • Intracellular Signaling Peptides and Proteins
  • Proto-Oncogene Proteins
  • Runx1 protein, mouse
  • Smad1 Protein
  • Smad1 protein, mouse
  • T-Cell Acute Lymphocytic Leukemia Protein 1
  • Tal1 protein, mouse
  • Globins