PROJECT SUMMARY
Supravalvular aortic stenosis (SVAS) is a developmental cardiovascular disease, occurring alone or in
Williams Beuren Syndrome (WBS), and results in excessive arterial smooth muscle cell (SMC) proliferation
and lumen obstruction. Our long-term objective is to elucidate how this pathology can be attenuated.
Heterozygous loss-of-function mutations or deletions of the elastin gene ELN cause SVAS. Eln(-/-) embryos and
Eln(+/-) neonatal mice develop arterial disease with features similar to human SVAS4-6. Elastin forms the major
component of the elastic lamellae in arteries. Defective lamellae are associated with excessive developmental
SMC proliferation in SVAS. If untreated, SVAS results in heart failure and an increased risk of sudden death,
and major surgery, which carries substantial risk, is the only treatment. Medical therapies are lacking because
mechanisms linking defective elastin and SMC hypermuscularization are incompletely defined. We aim to
elucidate molecular and cellular mechanisms underlying elastin aortopathy.
The Notch pathway is critical in regulating SMC biology, and we recently reported a role for Notch in
SVAS pathogenesis (JCI, 2022). Signaling via Notch ligand Jagged1 (JAG1) and NOTCH3 receptor in SMCs
activates proliferation. Our studies reveal that JAG1-NOTCH3 pathway components are upregulated after
elastin depletion. Importantly, we determined that inhibiting the NOTCH3 pathway in Eln(-/-) embryos attenuates
aortic hypermuscularization and stenosis and reverses established hypermuscularization in Eln(+/-) pups.
Epigenetic modifications influence gene expression by altering chromatin accessibility but prior to our
JCI paper, have not been explored in elastin deficiency. Our initial data indicate that elastin deficient aortas
and SMCs display reduced DNA methylation, elevated histone acetylation and reduced expression of DNA
methyltransferase 1 (DNMT1) and histone deacetylase 1 (HDAC1). We hypothesize that elastin deficiency
attenuates DNMT1- and HDAC1-mediated repression of Notch pathway genes to promote aortic
hypermuscularization and stenosis. The proposed studies use cell culture, mouse models, de-identified human
samples and advanced genomic and epigenetic techniques to uncover mechanisms of SVAS that can be
therapeutically targeted. We will test our hypothesis in two aims. Aim 1 will determine how elastin deficiency
alters epigenetic mediators and the epigenetic landscape in human and murine SMCs, including 1a) identifying
elastin-regulated epigenetic enzymes, 1b) determining mechanisms by which elastin deficiency modulates
epigenetic regulators, 1c) an integrated genome-wide epigenetic and transcriptomic analysis to identify new
regulatory mechanisms and 1d) characterization of epigenetic enzymes and marks in human samples. Aim 2
will elucidate the relationship between elastin, chromatin remodeling and the Notch pathway, including 2a)
identifying causal epigenetic mechanisms, 2b) kinetics and 2c) testing HAT inhibition as a therapy in mouse
models of SVAS. These studies promise to yield new treatments for this lethal genetic disease.