TY - JOUR
T1 - Endoglin and Alk5 regulate epithelial-mesenchymal transformation during cardiac valve formation
AU - Mercado-Pimentel, Melania E.
AU - Hubbard, Antony D.
AU - Runyan, Raymond B.
PY - 2007/4/1
Y1 - 2007/4/1
N2 - Endoglin is an accessory receptor for TGFβ and can associate with Alk5 or Alk2. Although prior studies indicated that endoglin and Alk5 were not directly involved in epithelial-mesenchymal transformation (EMT) in the heart, the expression pattern of endoglin prompted a re-examination. We here show that loss of endoglin expression mediated by either antisense DNA or siRNA results in a direct perturbation of EMT and reduced expression of EMT markers including slug, runx2, RhoA, and latrophilin-2. An examination of BrdU incorporation shows that, while endoglin regulates proliferation at an early stage, reduced endothelial cell proliferation does not account for the loss of mesenchyme. As Alk5 interacts with endoglin, we utilized siRNA and a specific inhibitor, HTS466284 (HTS), to perturb this receptor as well. Alk5 inhibition produced similar effects to the inhibition of endoglin. There was a reduction in mesenchymal cell formation and loss of EMT marker expression similar to that seen with endoglin. Alk5 kinase inhibition produced a similar loss of EMT marker expression but showed a contrasting upregulation of the proliferation and remodeling markers, Cyclin B2 and β-catenin. Alk5 and endoglin both mediate endothelial cell proliferation in younger explants but, by stage 16, loss of endoglin no longer alters proliferation rates. These data show that both Alk5 and endoglin are directly involved in the process of EMT, that they interact with both TGFβ-regulated activation and invasion pathways and that the roles of these receptors change during cardiac development.
AB - Endoglin is an accessory receptor for TGFβ and can associate with Alk5 or Alk2. Although prior studies indicated that endoglin and Alk5 were not directly involved in epithelial-mesenchymal transformation (EMT) in the heart, the expression pattern of endoglin prompted a re-examination. We here show that loss of endoglin expression mediated by either antisense DNA or siRNA results in a direct perturbation of EMT and reduced expression of EMT markers including slug, runx2, RhoA, and latrophilin-2. An examination of BrdU incorporation shows that, while endoglin regulates proliferation at an early stage, reduced endothelial cell proliferation does not account for the loss of mesenchyme. As Alk5 interacts with endoglin, we utilized siRNA and a specific inhibitor, HTS466284 (HTS), to perturb this receptor as well. Alk5 inhibition produced similar effects to the inhibition of endoglin. There was a reduction in mesenchymal cell formation and loss of EMT marker expression similar to that seen with endoglin. Alk5 kinase inhibition produced a similar loss of EMT marker expression but showed a contrasting upregulation of the proliferation and remodeling markers, Cyclin B2 and β-catenin. Alk5 and endoglin both mediate endothelial cell proliferation in younger explants but, by stage 16, loss of endoglin no longer alters proliferation rates. These data show that both Alk5 and endoglin are directly involved in the process of EMT, that they interact with both TGFβ-regulated activation and invasion pathways and that the roles of these receptors change during cardiac development.
KW - EMT
KW - Runx2
KW - TGFbeta 3
KW - TRβRI
UR - http://www.scopus.com/inward/record.url?scp=33947095941&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33947095941&partnerID=8YFLogxK
U2 - 10.1016/j.ydbio.2006.12.038
DO - 10.1016/j.ydbio.2006.12.038
M3 - Article
C2 - 17250821
AN - SCOPUS:33947095941
SN - 0012-1606
VL - 304
SP - 420
EP - 432
JO - Developmental biology
JF - Developmental biology
IS - 1
ER -