VEGFA Stop-Gained Variant Deteriorates Cardiac Remodeling in Myocardial Infarction.

Background: A sustained dosage of VEGFA (vascular endothelial growth factor A) is crucial for angiogenesis in both homeostasis and cardiovascular diseases. Start codon CUG-initiated alternative translation is a conserved mechanism for producing mature VEGFA. Genetic surveys have identified stop-gained variants predicted to prematurely terminate CUG-initiated translation without affecting start codon ATG-initiated translation. However, the impacts of these variants on the vasculature in steady-state and disease conditions remain unknown.

Methods: Using CRISPR/Cas9 genome editing, we established the allele (Q150X), a mouse genetic model that mimics the human VEGFA stop-gained variant. The effects of this variant were tested in both adult homeostatic conditions and the acute myocardial infarction (MI) model. We analyzed and quantified cardiac vasculature structure using immunofluorescence and light-sheet imaging. Furthermore, we characterized cellular heterogeneity, cell-cell interactions, and gene regulation using single-nucleus RNA sequencing, as well as cell type-specific transcriptomics and epigenomics.

Results: Homozygous mice carrying the stop-gained variant were viable. VEGFA dosage was reduced to 70% in the Q150X homeostatic heart, with no significant alteration in cardiac function or vasculature. In the MI model, VEGFA dosage in Q150X was reduced to about 40% within the first week post-infarction, leading to functional deterioration in the post-MI hearts. Significant changes in cellular composition were observed 3 days post-MI. In particular, endothelial cells in Q150X diverged into a state that showed a higher level of hypoxia stress, an elevated inflammatory response, and increased extracellular matrix secretion. In addition, we observed an increase in Nppb stressed cardiomyocytes in both 3 days post-MI and homeostasis. Finally, proinflammatory macrophages, neutrophils, and Cd8T cells were enriched in the ischemic zone of Q150X hearts.

Conclusions: CUG-initiated translation contributes significantly to the production of mature VEGFA in ischemic hearts. VEGFA dosage is critical in determining the cellular microenvironment during ischemic injury.