The Cerebral Cavernous Malformation Pathway Controls Cardiac Development via Regulation of Endocardial MEKK3 Signaling and KLF Expression

Abstract

SUMMARY The cerebral cavernous malformation (CCM) pathway is required in endothelial cells for normal cardiovascular development and to prevent postnatal vascular malformations, but its molecular effectors are not well defined. Here we show that loss of CCM signaling in endocardial cells results in mid-gestation heart failure associated with premature degradation of cardiac jelly. CCM deficiency dramatically alters endocardial and endothelial gene expression, including increased expression of the Klf2 and Klf4 transcription factors and the Adamts4 and Adamts5 proteases that degrade cardiac jelly. These changes in gene expression result from increased activity of MEKK3, a mitogen-activated protein kinase that binds CCM2 in endothelial cells. MEKK3 is both necessary and sufficient for expression of these genes, and partial loss of MEKK3 rescues cardiac defects in CCM-deficient embryos. These findings reveal a molecular mechanism by which CCM signaling controls endothelial gene expression during cardiovascular development that may also underlie CCM formation.

The force within: endocardial development, mechanotransduction and signalling during cardiac morphogenesis

“…The severe endocardial defects and loss of endocardial cushion formation in CCM mutants can be explained by an earlier finding that the inhibition of Notch signalling causes increased Bmp6 expression; this, in turn, triggers pathological endMT (Maddaluno et al, 2013). It was recently shown that the loss of CCM proteins in mice activates the mitogen-activated protein kinase kinase kinase 3 (Map3k3; also known as Mekk3) signalling pathway, resulting in increased expression of ADAM metallopeptidase with thrombospondin type 1 motif 4/5 (Adamts4/5) proteases, which degrade cardiac jelly, and increased levels of Klf2 (Zhou et al, 2015). Furthermore, it was found that the endocardial CCM mutant phenotypes in zebrafish are the result of the overexpression of Klf2a and Klf2b, which are activated by β1 integrin in a blood flow-independent manner (Renz et al, 2015).…”

“…Klf2 expression is also controlled by the cerebral cavernous malformations (CCM) complex in mice and zebrafish (Renz et al, 2015;Zhou et al, 2015). CCM complex components play a role in controlling the response of β1 integrin signalling to blood flow in endothelial cells (Macek Jilkova et al, 2014), and the loss of CCM proteins in mouse and zebrafish results in severe cardiovascular defects (Boulday et al, 2009;Hogan et al, 2008;Kleaveland et al, 2009;Mably et al, 2003Mably et al, , 2006Renz et al, 2015;Yoruk et al, 2012;Zheng et al, 2010;Zhou et al, 2015).…”

“…CCM complex components play a role in controlling the response of β1 integrin signalling to blood flow in endothelial cells (Macek Jilkova et al, 2014), and the loss of CCM proteins in mouse and zebrafish results in severe cardiovascular defects (Boulday et al, 2009;Hogan et al, 2008;Kleaveland et al, 2009;Mably et al, 2003Mably et al, , 2006Renz et al, 2015;Yoruk et al, 2012;Zheng et al, 2010;Zhou et al, 2015). Although Klf2 signalling has mainly been associated with vasoprotective functions within endothelial cells in response to shear stress (Dekker et al, 2006;Lee et al, 2006;Parmar et al, 2006), or with the control of cardiac valve morphogenesis in response to reversible flows (Heckel et al, 2015;Vermot et al, 2009), it has another important function: it promotes proangiogenic signalling during zebrafish aortic arch blood vessel development (Nicoli et al, 2010).…”

“…We then review the role of endocardial-myocardial signalling and the impact of blood flow during cardiac morphogenesis. We also highlight how dysregulated blood flow responses within the endocardium can have pathological consequences (Renz et al, 2015;Zhou et al, 2015).…”

Suberanilohydroxamic Acid as a Pharmacological Kruppel‐Like Factor 2 Activator That Represses Vascular Inflammation and Atherosclerosis

“…Experimental studies have demonstrated that shear stress11 along with small molecules such as lipid‐lowering statins10, 12 and resveratrol are capable of exerting vasoprotective effects by promoting KLF2 activation 4, 12, 13. The molecular mechanisms involved in the regulation of endothelial KLF2 expression includes the AMP‐activated protein kinase/dual specificity mitogen‐activated protein kinase kinase 5/extracellular‐signal related kinase 5/MEF2 (myocyte enhancing factor 2) pathway and the histone deacetylase (HDAC) 5 pathway 1, 14, 15. Recent studies have demonstrated that deletion of 1 KLF2 allele in mice increases atherosclerosis,16 and KLF2 controls endothelial and vascular integrity 17.…”