Myocardin-like protein 2 regulates TGFβ signaling in embryonic stem cells and the developing vasculature.
The molecular mechanisms that regulate and coordinate signaling between the extracellular matrix (ECM) and cells contributing to the developing vasculature are complex and poorly understood. Myocardin-like protein 2 (MKL2) is a transcriptional co-activator that in response to RhoA and cytoskeletal actin signals physically associates with serum response factor (SRF), activating a subset of SRF-regulated genes. We now report the discovery of a previously undescribed MKL2/TGFβ signaling pathway in embryonic stem (ES) cells that is required for maturation and stabilization of the embryonic vasculature. Mkl2(-/-) null embryos exhibit profound derangements in the tunica media of select arteries and arterial beds, which leads to aneurysmal dilation, dissection and hemorrhage. Remarkably, TGFβ expression, TGFβ signaling and TGFβ-regulated genes encoding ECM are downregulated in Mkl2(-/-) ES cells and the vasculature of Mkl2(-/-) embryos. The gene encoding TGFβ2, the predominant TGFβ isoform expressed in vascular smooth muscle cells and embryonic vasculature, is activated directly via binding of an MKL2/SRF protein complex to a conserved CArG box in the TGFβ2 promoter. Moreover, Mkl2(-/-) ES cells exhibit derangements in cytoskeletal organization, cell adhesion and expression of ECM that are rescued by forced expression of TGFβ2. Taken together, these data demonstrate that MKL2 regulates a conserved TGF-β signaling pathway that is required for angiogenesis and ultimately embryonic survival.
University of Pennsylvania Cardiovascular Institute, University of Pennsylvania, Philadelphia, PA 19104-4283, USA.
Jian
J
Li
Nina
N
Bowens
Lan
L
Cheng
Xiaohong
X
Zhu
Mary
M
Chen
Sridhar
S
Hannenhalli
Thomas P
TP
Cappola
Michael S
MS
Parmacek
D000818:Animals; D001164:Arteriovenous Fistula / Q000196:embryology / Q000235:genetics; D001808:Blood Vessels / Q000196:embryology* / Q000378:metabolism; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D053595:Embryonic Stem Cells / Q000378:metabolism* / Q000502:physiology; D005328:Fetal Viability / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D006470:Hemorrhage / Q000196:embryology / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D053781:Transforming Growth Factor beta2 / Q000235:genetics* / Q000378:metabolism
C509042:Tgfb2 protein, mouse; D014157:Transcription Factors; D053781:Transforming Growth Factor beta2; C576273:myocardin-like protein 2, mouse