KRAS and Patent ductus arteriosus: The engineered AAV for PDA initiation includes a U6 promoter-driven expression of an sgRNA targeting exon2 of Kras (U6-sgKras), a 2.1Kb Kras genomic template with the codon 12 glycine-to-aspartic acid mutation (KrasG12D) flanked by diverse combinations of synonymous mutations that serve as molecular barcodes for lineage tracing and a set of sgKras-resistant synonymous mutations, and PGK-Cre (Figure 2B).