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To efficiently distribute blood flow to cardiac muscle, the coronary artery tree must follow a specific branching pattern over the heart. How this pattern arises in humans is unknown due to the limitations of studying human heart development. Here, we leveraged a natural variation of coronary artery anatomy, known as coronary dominance, in genetic association studies to identify the first known driver of human coronary developmental patterning. Coronary dominance refers to whether the right, left, or both coronary arteries branch over the posterior left ventricle, but whether this variability is heritable and how it would be genetically regulated was completely unknown. By conducting the first large-scale, multi-ancestry genome-wide association study (GWAS) of coronary dominance in 61,043 participants of the VA Million Veteran Program, we observed moderate heritability (27.7%) with ten loci reaching genome wide significance. An exceptionally strong association mapped DNA variants to a non-coding region near the chemokine CXCL12 in both European and African ancestries, which overlapped with variants associated with coronary artery disease. Genomic analyses predicted these variants to impact CXCL12 levels, and imaging revealed dominance to develop during fetal life coincident with CXCL12 expression. Reducing Cxcl12 in mice to model the human genetics altered septal artery dominance patterns and caused coronary branches to develop away from Cxcl12 expression domains. Cxcl12 heterozygosity did not compromise overall artery coverage as seen with full deletion, but instead changed artery patterning, reminiscent of the human scenario. Together, our data support CXCL12 as a critical determinant of human coronary artery growth and patterning and lay a foundation for the utilization of developmental pathways to guide future precision 'medical revascularization' therapeutics., Competing Interests: Competing interests: A.K. is on the scientific advisory board of SerImmune, TensorBio and OpenTargets, and a consultant with Arcadia Science and Inari Agriculture. A.K. was a scientific co-founder of RavelBio, a paid consultant with Illumina, was on the SAB of PatchBio and owns shares in DeepGenomics, Immunai, Freenome, and Illumina. All other authors declare they have no competing interests.

Endocardial cells lining the heart lumen are coronary vessel progenitors during embryogenesis. Re-igniting this developmental process in adults could regenerate blood vessels lost during cardiac injury, but this requires additional knowledge of molecular mechanisms. Here, we use mouse genetics and scRNA-seq to identify regulators of endocardial angiogenesis and precisely assess the role of CXCL12/CXCR4 signaling. Time-specific lineage tracing demonstrated that endocardial cells differentiated into coronary endothelial cells primarily at mid-gestation. A new mouse line reporting CXCR4 activity-along with cell-specific gene deletions-demonstrated it was specifically required for artery morphogenesis rather than angiogenesis. Integrating scRNA-seq data of endocardial-derived coronary vessels from mid- and late-gestation identified a Bmp2-expressing transitioning population specific to mid-gestation. Bmp2 stimulated endocardial angiogenesis in vitro and in injured neonatal mouse hearts. Our data demonstrate how understanding the molecular mechanisms underlying endocardial angiogenesis can identify new potential therapeutic targets promoting revascularization of the injured heart., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Inc. All rights reserved.)

O-Linked β-N -acetylglucosamine (O-GlcNAc) is a monosaccharide that plays an essential role in cellular signaling throughout the nucleocytoplasmic proteome of eukaryotic cells. Strategies for selectively increasing O-GlcNAc levels on a target protein in cells would accelerate studies of this essential modification. Here, we report a generalizable strategy for introducing O-GlcNAc into selected target proteins in cells using a nanobody as a proximity-directing agent fused to O-GlcNAc transferase (OGT). Fusion of a nanobody that recognizes GFP (nGFP) or a nanobody that recognizes the four-amino acid sequence EPEA (nEPEA) to OGT yielded nanobody-OGT constructs that selectively delivered O-GlcNAc to a series of tagged target proteins (e.g., JunB, cJun, and Nup62). Truncation of the tetratricopeptide repeat domain as in OGT(4) increased selectivity for the target protein through the nanobody by reducing global elevation of O-GlcNAc levels in the cell. Quantitative chemical proteomics confirmed the increase in O-GlcNAc to the target protein by nanobody-OGT(4). Glycoproteomics revealed that nanobody-OGT(4) or full-length OGT produced a similar glycosite profile on the target protein JunB and Nup62. Finally, we demonstrate the ability to selectively target endogenous α-synuclein for O-GlcNAcylation in HEK293T cells. These first proximity-directed OGT constructs provide a flexible strategy for targeting additional proteins and a template for further engineering of OGT and the O-GlcNAc proteome in the future. The use of a nanobody to redirect OGT substrate selection for glycosylation of desired proteins in cells may further constitute a generalizable strategy for controlling a broader array of post-translational modifications in cells.