CXCL12 regulates coronary artery dominance in diverse populations and links development to disease.

Mammalian cardiac muscle is supplied with blood by right and left coronary arteries that form branches covering both ventricles of the heart. Whether branches of the right or left coronary arteries wrap around to the inferior side of the left ventricle is variable in humans and termed right or left dominance. Coronary dominance is likely a heritable trait, but its genetic architecture has never been explored. Here, we present the first large-scale multi-ancestry genome-wide association study of dominance in 61,043 participants of the VA Million Veteran Program, including over 10,300 Africans and 4,400 Admixed Americans. Dominance was moderately heritable with ten loci reaching genome wide significance. The most significant mapped to the chemokine CXCL12 in both Europeans and Africans. Whole-organ imaging of human fetal hearts revealed that dominance is established during development in locations where CXCL12 is expressed. In mice, dominance involved the septal coronary artery, and its patterning was altered with Cxcl12 deficiency. Finally, we linked human dominance patterns with coronary artery disease through colocalization, genome-wide genetic correlation and Mendelian Randomization analyses. Together, our data supports CXCL12 as a primary determinant of coronary artery dominance in humans of diverse backgrounds and suggests that developmental patterning of arteries may influence one's susceptibility to ischemic heart disease.

Endocardium-to-coronary artery differentiation during heart development and regeneration involves sequential roles of Bmp2 and Cxcl12/Cxcr4.

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.

Depletion of aneuploid cells in human embryos and gastruloids.

Chromosomal instability leading to aneuploidy is pervasive in early human embryos1-3 and is considered as a major cause of infertility and pregnancy wastage4,5. Here we provide several lines of evidence that blastocysts containing aneuploid cells are worthy of in vitro fertilization transfer. First, we show clinically that aneuploid embryos can lead to healthy births, suggesting the presence of an in vivo mechanism to eliminate aneuploidy. Second, early development and cell specification modelled in micropatterned human 'gastruloids' grown in confined geometry show that aneuploid cells are depleted from embryonic germ layers, but not from extraembryonic tissue, by apoptosis in a bone morphogenetic protein 4 (BMP4)-dependent manner. Third, a small percentage of euploid cells rescues embryonic tissue in mosaic gastruloids when mixed with aneuploid cells. Finally, single-cell RNA-sequencing analysis of early human embryos revealed a decline of aneuploidy beginning on day 3. Our findings challenge two current dogmas: that a single trophectoderm biopsy at blastocyst stage to perform prenatal genetic testing can accurately determine the chromosomal make-up of a human embryo, and that aneuploid embryos should be withheld from embryo transfer in association with in vitro fertilization.

Engineering a Proximity-Directed O-GlcNAc Transferase for Selective Protein O-GlcNAcylation in Cells.

O-Linked ß-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.