Convergence of coronary artery disease genes onto endothelial cell programs.

Linking variants from genome-wide association studies (GWAS) to underlying mechanisms of disease remains a challenge1-3. For some diseases, a successful strategy has been to look for cases in which multiple GWAS loci contain genes that act in the same biological pathway1-6. However, our knowledge of which genes act in which pathways is incomplete, particularly for cell-type-specific pathways or understudied genes. Here we introduce a method to connect GWAS variants to functions. This method links variants to genes using epigenomics data, links genes to pathways de novo using Perturb-seq and integrates these data to identify convergence of GWAS loci onto pathways. We apply this approach to study the role of endothelial cells in genetic risk for coronary artery disease (CAD), and discover 43 CAD GWAS signals that converge on the cerebral cavernous malformation (CCM) signalling pathway. Two regulators of this pathway, CCM2 and TLNRD1, are each linked to a CAD risk variant, regulate other CAD risk genes and affect atheroprotective processes in endothelial cells. These results suggest a model whereby CAD risk is driven in part by the convergence of causal genes onto a particular transcriptional pathway in endothelial cells. They highlight shared genes between common and rare vascular diseases (CAD and CCM), and identify TLNRD1 as a new, previously uncharacterized member of the CCM signalling pathway. This approach will be widely useful for linking variants to functions for other common polygenic diseases.

Compatibility rules of human enhancer and promoter sequences.

Gene regulation in the human genome is controlled by distal enhancers that activate specific nearby promoters1. A proposed model for this specificity is that promoters have sequence-encoded preferences for certain enhancers, for example, mediated by interacting sets of transcription factors or cofactors2. This 'biochemical compatibility' model has been supported by observations at individual human promoters and by genome-wide measurements in Drosophila3-9. However, the degree to which human enhancers and promoters are intrinsically compatible has not yet been systematically measured, and how their activities combine to control RNA expression remains unclear. Here we design a high-throughput reporter assay called enhancer × promoter self-transcribing active regulatory region sequencing (ExP STARR-seq) and applied it to examine the combinatorial compatibilities of 1,000 enhancer and 1,000 promoter sequences in human K562 cells. We identify simple rules for enhancer-promoter compatibility, whereby most enhancers activate all promoters by similar amounts, and intrinsic enhancer and promoter activities multiplicatively combine to determine RNA output (R2 = 0.82). In addition, two classes of enhancers and promoters show subtle preferential effects. Promoters of housekeeping genes contain built-in activating motifs for factors such as GABPA and YY1, which decrease the responsiveness of promoters to distal enhancers. Promoters of variably expressed genes lack these motifs and show stronger responsiveness to enhancers. Together, this systematic assessment of enhancer-promoter compatibility suggests a multiplicative model tuned by enhancer and promoter class to control gene transcription in the human genome.

Genome-wide enhancer maps link risk variants to disease genes.

Genome-wide association studies (GWAS) have identified thousands of noncoding loci that are associated with human diseases and complex traits, each of which could reveal insights into the mechanisms of disease1. Many of the underlying causal variants may affect enhancers2,3, but we lack accurate maps of enhancers and their target genes to interpret such variants. We recently developed the activity-by-contact (ABC) model to predict which enhancers regulate which genes and validated the model using CRISPR perturbations in several cell types4. Here we apply this ABC model to create enhancer-gene maps in 131 human cell types and tissues, and use these maps to interpret the functions of GWAS variants. Across 72 diseases and complex traits, ABC links 5,036 GWAS signals to 2,249 unique genes, including a class of 577 genes that appear to influence multiple phenotypes through variants in enhancers that act in different cell types. In inflammatory bowel disease (IBD), causal variants are enriched in predicted enhancers by more than 20-fold in particular cell types such as dendritic cells, and ABC achieves higher precision than other regulatory methods at connecting noncoding variants to target genes. These variant-to-function maps reveal an enhancer that contains an IBD risk variant and that regulates the expression of PPIF to alter the membrane potential of mitochondria in macrophages. Our study reveals principles of genome regulation, identifies genes that affect IBD and provides a resource and generalizable strategy to connect risk variants of common diseases to their molecular and cellular functions.

A Comprehensive Survey of 2024 Funding for Radiation Oncology Visiting Medical Student Electives.

Visiting electives provide an opportunity for medical students to engage with radiation oncology (RO) programs, likely influencing residency match outcomes. However, some student's out-of-pocket costs may be prohibitive, and in attempts to offset the financial burden of visiting electives, particularly for students underrepresented in medicine (URiM), some institutions offer scholarships. Here, we characterized the current domestic landscape of funded RO electives. Visiting electives were identified through the FREIDA and VSLO databases in April 2024. Funded elective availability and departmental characteristics were identified via internet search by two independent reviewers. Fisher's exact test was used to determine whether there was a difference in the distribution of scholarships across the US due to the small sample size. Ninety-two visiting electives were identified, with 40 programs offering URiM elective scholarships (43.5%). Twelve (30%) were funded specifically by RO departments, and 28 (70%) were part of broader institutional URiM scholarship initiatives. The median stipend provided was $2000 (IQR $500), range $1000-$5000. Analysis of scholarships by US census division and metro area revealed unequal distribution. Electives in New England, Mountain, and East North Central divisions had higher funding proportion compared to electives in the East South Central, West South Central, and Middle Atlantic divisions. Only 1/9 electives in New York City were funded compared with 4/6 in Los Angeles. Departments with funded electives had more faculty physicians and medical residents. In our review of the 2024 landscape, over 40% of RO electives offer financial support. However, we identified geographical disparities in the distribution of scholarships, highlighting the need for interventions to address unequal access to a wide array of training programs. Our study represents a valuable resource for students interested in RO and highlights the continued need to positively contribute to increasing diversity in the field. Future work exploring the impact of funded electives is needed.

HyPR-seq: Single-cell quantification of chosen RNAs via hybridization and sequencing of DNA probes.

Single-cell quantification of RNAs is important for understanding cellular heterogeneity and gene regulation, yet current approaches suffer from low sensitivity for individual transcripts, limiting their utility for many applications. Here we present Hybridization of Probes to RNA for sequencing (HyPR-seq), a method to sensitively quantify the expression of hundreds of chosen genes in single cells. HyPR-seq involves hybridizing DNA probes to RNA, distributing cells into nanoliter droplets, amplifying the probes with PCR, and sequencing the amplicons to quantify the expression of chosen genes. HyPR-seq achieves high sensitivity for individual transcripts, detects nonpolyadenylated and low-abundance transcripts, and can profile more than 100,000 single cells. We demonstrate how HyPR-seq can profile the effects of CRISPR perturbations in pooled screens, detect time-resolved changes in gene expression via measurements of gene introns, and detect rare transcripts and quantify cell-type frequencies in tissue using low-abundance marker genes. By directing sequencing power to genes of interest and sensitively quantifying individual transcripts, HyPR-seq reduces costs by up to 100-fold compared to whole-transcriptome single-cell RNA-sequencing, making HyPR-seq a powerful method for targeted RNA profiling in single cells.

Cohesin-mediated 3D contacts tune enhancer-promoter regulation.

Enhancers are key drivers of gene regulation thought to act via 3D physical interactions with the promoters of their target genes. However, genome-wide depletions of architectural proteins such as cohesin result in only limited changes in gene expression, despite a loss of contact domains and loops. Consequently, the role of cohesin and 3D contacts in enhancer function remains debated. Here, we developed CRISPRi of regulatory elements upon degron operation (CRUDO), a novel approach to measure how changes in contact frequency impact enhancer effects on target genes by perturbing enhancers with CRISPRi and measuring gene expression in the presence or absence of cohesin. We systematically perturbed all 1,039 candidate enhancers near five cohesin-dependent genes and identified 34 enhancer-gene regulatory interactions. Of 26 regulatory interactions with sufficient statistical power to evaluate cohesin dependence, 18 show cohesin-dependent effects. A decrease in enhancer-promoter contact frequency upon removal of cohesin is frequently accompanied by a decrease in the regulatory effect of the enhancer on gene expression, consistent with a contact-based model for enhancer function. However, changes in contact frequency and regulatory effects on gene expression vary as a function of distance, with distal enhancers (e.g., >50Kb) experiencing much larger changes than proximal ones (e.g., <50Kb). Because most enhancers are located close to their target genes, these observations can explain how only a small subset of genes - those with strong distal enhancers - are sensitive to cohesin. Together, our results illuminate how 3D contacts, influenced by both cohesin and genomic distance, tune enhancer effects on gene expression.

Genomic profile of Pancoast syndrome due to hepatocellular carcinoma: A case report.

Hepatocellular carcinoma (HCC) is a common cancer and is frequently diagnosed at a late and unresectable stage with limited effective treatment options. Here, we present the fifth reported case of a 77 year-old male with metastatic HCC presenting as a symptomatic superior sulcus lung tumor and discuss the genomic profile of this rare presentation of HCC for the first time, which included multiple classic mutations in HCC such as TERT, TP53, and WNT/ß-catenin signaling as well as in the DNA repair gene ATM. The patient was treated with palliative radiotherapy to the Pancoast tumor followed by atezolizumab plus bevacizumab and passed away 6 months after diagnosis. This rare case highlights the need for effective treatment in aggressive and unresectable HCC and the utility of early genomic studies to allow for targeted therapy such as poly (ADP-ribose) polymerase (PARP)-inhibitors.

Genome-Scale DNA Methylation Analysis Identifies Repeat Element Alterations that Modulate the Genomic Stability of Melanocytic Nevi.

Acquired melanocytic nevi grow and persist in a stable form into adulthood. Using genome-wide methylation profiling, we evaluated 32 histopathologically and dermoscopically characterized nevi to identify the key epigenetic regulatory mechanisms involved in nevogenesis. Benign (69% globular and 31% nonspecific dermoscopic pattern) and dysplastic (95% reticular/nonspecific dermoscopic pattern) nevi were dissimilar, with only two shared differentially methylated loci. Benign nevi showed an increase in both genome-scale methylation and methylation of Alu/LINE-1 retrotransposable elements, a marker of genomic stability, as well as global methylation. In contrast, dysplastic nevi showed evidence for genomic instability through the hypomethylation of Alu/LINE-1 (Alu: P = 0.00019; LINE-1: P = 0.000035). Using dermoscopic classifications, reticular/nonspecific patterned nevi had 59,572 5'-C-phosphate-G-3' differentially methylated loci (Q < 0.05), whereas globular nevi had no significant differentially methylated loci. In reticular/nonspecific patterned nevi, the tumor suppressor PTEN had the greatest proportion of hypermethylated 5'-C-phosphate-G-3' loci in its promoter region than all other assayed gene promoters. The relative activity of reticular/nonspecific nevi was evidenced by 50,720 hypomethylated loci being enriched for accessible chromatin and 8,852 hypermethylated loci strongly enriched, for example, marks of active gene promoters, which suggests that gain of DNA methylation observed in these nevus types plays a role in gene regulation.

Prioritizing disease and trait causal variants at the TNFAIP3 locus using functional and genomic features.

Genome-wide association studies have associated thousands of genetic variants with complex traits and diseases, but pinpointing the causal variant(s) among those in tight linkage disequilibrium with each associated variant remains a major challenge. Here, we use seven experimental assays to characterize all common variants at the multiple disease-associated TNFAIP3 locus in five disease-relevant immune cell lines, based on a set of features related to regulatory potential. Trait/disease-associated variants are enriched among SNPs prioritized based on either: (1) residing within CRISPRi-sensitive regulatory regions, or (2) localizing in a chromatin accessible region while displaying allele-specific reporter activity. Of the 15 trait/disease-associated haplotypes at TNFAIP3, 9 have at least one variant meeting one or both of these criteria, 5 of which are further supported by genetic fine-mapping. Our work provides a comprehensive strategy to characterize genetic variation at important disease-associated loci, and aids in the effort to identify trait causal genetic variants.

Activity-by-contact model of enhancer-promoter regulation from thousands of CRISPR perturbations.

Enhancer elements in the human genome control how genes are expressed in specific cell types and harbor thousands of genetic variants that influence risk for common diseases1-4. Yet, we still do not know how enhancers regulate specific genes, and we lack general rules to predict enhancer-gene connections across cell types5,6. We developed an experimental approach, CRISPRi-FlowFISH, to perturb enhancers in the genome, and we applied it to test >3,500 potential enhancer-gene connections for 30 genes. We found that a simple activity-by-contact model substantially outperformed previous methods at predicting the complex connections in our CRISPR dataset. This activity-by-contact model allows us to construct genome-wide maps of enhancer-gene connections in a given cell type, on the basis of chromatin state measurements. Together, CRISPRi-FlowFISH and the activity-by-contact model provide a systematic approach to map and predict which enhancers regulate which genes, and will help to interpret the functions of the thousands of disease risk variants in the noncoding genome.