Intrinsic Gata4 expression sensitizes the aortic root to dilation in a Loeys-Dietz syndrome mouse model

Loeys-Dietz syndrome (LDS) is a hereditary aneurysm disorder caused by mutations that impair transforming growth factor- (TGF-) signaling. Although LDS patients develop aneurysms throughout the arterial tree, the aortic root is a site of increased risk. In order to identify molecular determinants of this regional vulnerability, we investigated the transcriptional heterogeneity of vascular smooth muscle cells (VSMCs) in the aorta of Tgfbr1M318R/+ LDS mouse models by single cell RNA sequencing (scRNAseq) and spatial transcriptomics. Downregulation of transcripts coding for components of the extracellular matrix-receptor mechanosensing apparatus and upregulation of transcripts related to stress and inflammation were observed in all Tgfbr1M318R/+ VSMCs. However, regardless of genotype, a subset of Gata4-expressing VSMCs predominantly located in the aortic root intrinsically displayed a less differentiated, pro-inflammatory transcriptional profile. A similar population was also identified in a published scRNAseq dataset of the aorta of LDS patients via the Coordinated Gene Activity in Pattern Sets (CoGAPS)/ProjectR pipeline. Postnatal VSMC-specific Gata4 deletion resulted in reduced aortic root dilation in LDS mice, in association with decreased levels of Agtr1a and other pro-inflammatory regulators. We propose that widespread dysregulation of mechanosensitive pathways may act on regionally restricted factors that prime specific aortic locations to increased risk of aneurysm. Tgfbr1+/+ and Tgfbr1M318R/+ (The Jackson Laboratory, strain #036511) mice, some bearing the EGFP-L10a (The Jackson Laboratory, strain #024750) conditional tracer allele and a CNC-specific CRE recombinase expressed under the control of Wnt2 promoter (The Jackson Laboratory, strain #003829) were used for scRNAseq at 16 weeks of age. All mice were maintained on a 129-background strain (Taconic, 129SVE).