Fibulin-1 suppresses endothelial to mesenchymal transition in the proximal outflow tract

Keerthi Harikrishnan, Marion Anne Cooley, Yukiko Sugi, Jeremy L. Barth, Lars M. Rasmussen, Christine B. Kern, Kelley M. Argraves, W. Scott Argraves

Research output: Contribution to journalArticle

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Abstract

Endothelial to mesenchymal transition (EMT) that occurs during cardiac outflow tract (OFT) development is critical for formation of the semilunar valves. Fibulin-1 (Fbln1) is an extracellular matrix protein that is present at several sites of EMT, including the OFT (i.e., E9.5-10.5). The aim of this study was to determine the role of Fbln1 in EMT during the earliest events of OFT development. Examination of proximal OFT cushions in Fbln1 null embryos detected hypercellularity at both E9.5 (93% increase; p = 0.002) and E10.5 (43% increase; p = 0.01) as compared to wild type, suggesting that Fbln1 normally suppresses OFT endocardial cushion EMT. This was supported by studies of proximal OFT cushion explants, which showed that explants from Fbln1 null embryos displayed a 58% increase in cells migrating from the explants as compared to wild type (p = 0.005). We next evaluated the effects of Fbln1 deficiency on the expression of factors that regulate proximal OFT EMT. At E9.5, Fbln1 null proximal OFT endocardium and EMT-derived mesenchyme showed increased TGFβ2 (58% increase; p = 0.01) and increased Snail1-positive nuclei (27% increase; p = 0.0003). Histological examination of OFT cushions in Fbln1 null embryos (E9.5) also detected cells present in the cushion that were determined to be erythrocytes based on round morphology, autofluorescence, and positive staining for hemoglobin. Erythrocytes were also detected in Fbln1 null OFT cushions at E10.5. Together, the findings indicate that Fbln1 normally suppresses proximal OFT EMT preventing proximal cushion hypercellularity and blood cell accumulation.

Original languageEnglish (US)
Pages (from-to)123-132
Number of pages10
JournalMechanisms of Development
Volume136
DOIs
StatePublished - May 1 2015

Fingerprint

Embryonic Structures
Endocardial Cushions
Erythrocytes
fibulin
Endocardium
Extracellular Matrix Proteins
Mesoderm
Blood Cells
Hemoglobins
Staining and Labeling

Keywords

  • EMT
  • Endocardial barrier
  • Endocardial cushions
  • Endothelial barrier
  • Extracellular matrix
  • Fibulin-1
  • Proximal outflow tract

ASJC Scopus subject areas

  • Embryology
  • Developmental Biology

Cite this

Harikrishnan, K., Cooley, M. A., Sugi, Y., Barth, J. L., Rasmussen, L. M., Kern, C. B., ... Argraves, W. S. (2015). Fibulin-1 suppresses endothelial to mesenchymal transition in the proximal outflow tract. Mechanisms of Development, 136, 123-132. https://doi.org/10.1016/j.mod.2014.12.005

Fibulin-1 suppresses endothelial to mesenchymal transition in the proximal outflow tract. / Harikrishnan, Keerthi; Cooley, Marion Anne; Sugi, Yukiko; Barth, Jeremy L.; Rasmussen, Lars M.; Kern, Christine B.; Argraves, Kelley M.; Argraves, W. Scott.

In: Mechanisms of Development, Vol. 136, 01.05.2015, p. 123-132.

Research output: Contribution to journalArticle

Harikrishnan, K, Cooley, MA, Sugi, Y, Barth, JL, Rasmussen, LM, Kern, CB, Argraves, KM & Argraves, WS 2015, 'Fibulin-1 suppresses endothelial to mesenchymal transition in the proximal outflow tract', Mechanisms of Development, vol. 136, pp. 123-132. https://doi.org/10.1016/j.mod.2014.12.005
Harikrishnan, Keerthi ; Cooley, Marion Anne ; Sugi, Yukiko ; Barth, Jeremy L. ; Rasmussen, Lars M. ; Kern, Christine B. ; Argraves, Kelley M. ; Argraves, W. Scott. / Fibulin-1 suppresses endothelial to mesenchymal transition in the proximal outflow tract. In: Mechanisms of Development. 2015 ; Vol. 136. pp. 123-132.
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abstract = "Endothelial to mesenchymal transition (EMT) that occurs during cardiac outflow tract (OFT) development is critical for formation of the semilunar valves. Fibulin-1 (Fbln1) is an extracellular matrix protein that is present at several sites of EMT, including the OFT (i.e., E9.5-10.5). The aim of this study was to determine the role of Fbln1 in EMT during the earliest events of OFT development. Examination of proximal OFT cushions in Fbln1 null embryos detected hypercellularity at both E9.5 (93{\%} increase; p = 0.002) and E10.5 (43{\%} increase; p = 0.01) as compared to wild type, suggesting that Fbln1 normally suppresses OFT endocardial cushion EMT. This was supported by studies of proximal OFT cushion explants, which showed that explants from Fbln1 null embryos displayed a 58{\%} increase in cells migrating from the explants as compared to wild type (p = 0.005). We next evaluated the effects of Fbln1 deficiency on the expression of factors that regulate proximal OFT EMT. At E9.5, Fbln1 null proximal OFT endocardium and EMT-derived mesenchyme showed increased TGFβ2 (58{\%} increase; p = 0.01) and increased Snail1-positive nuclei (27{\%} increase; p = 0.0003). Histological examination of OFT cushions in Fbln1 null embryos (E9.5) also detected cells present in the cushion that were determined to be erythrocytes based on round morphology, autofluorescence, and positive staining for hemoglobin. Erythrocytes were also detected in Fbln1 null OFT cushions at E10.5. Together, the findings indicate that Fbln1 normally suppresses proximal OFT EMT preventing proximal cushion hypercellularity and blood cell accumulation.",
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AU - Kern, Christine B.

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AU - Argraves, W. Scott

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AB - Endothelial to mesenchymal transition (EMT) that occurs during cardiac outflow tract (OFT) development is critical for formation of the semilunar valves. Fibulin-1 (Fbln1) is an extracellular matrix protein that is present at several sites of EMT, including the OFT (i.e., E9.5-10.5). The aim of this study was to determine the role of Fbln1 in EMT during the earliest events of OFT development. Examination of proximal OFT cushions in Fbln1 null embryos detected hypercellularity at both E9.5 (93% increase; p = 0.002) and E10.5 (43% increase; p = 0.01) as compared to wild type, suggesting that Fbln1 normally suppresses OFT endocardial cushion EMT. This was supported by studies of proximal OFT cushion explants, which showed that explants from Fbln1 null embryos displayed a 58% increase in cells migrating from the explants as compared to wild type (p = 0.005). We next evaluated the effects of Fbln1 deficiency on the expression of factors that regulate proximal OFT EMT. At E9.5, Fbln1 null proximal OFT endocardium and EMT-derived mesenchyme showed increased TGFβ2 (58% increase; p = 0.01) and increased Snail1-positive nuclei (27% increase; p = 0.0003). Histological examination of OFT cushions in Fbln1 null embryos (E9.5) also detected cells present in the cushion that were determined to be erythrocytes based on round morphology, autofluorescence, and positive staining for hemoglobin. Erythrocytes were also detected in Fbln1 null OFT cushions at E10.5. Together, the findings indicate that Fbln1 normally suppresses proximal OFT EMT preventing proximal cushion hypercellularity and blood cell accumulation.

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