Systematic characterization of regulatory variants of blood pressure genes.

High blood pressure (BP) is the major risk factor for cardiovascular disease. Genome-wide association studies have identified genetic variants for BP, but functional insights into causality and related molecular mechanisms lag behind. We functionally characterize 4,608 genetic variants in linkage with 135 BP loci in vascular smooth muscle cells and cardiomyocytes by massively parallel reporter assays. High densities of regulatory variants at BP loci (i.e., ULK4, MAP4, CFDP1, PDE5A) indicate that multiple variants drive genetic association. Regulatory variants are enriched in repeats, alter cardiovascular-related transcription factor motifs, and spatially converge with genes controlling specific cardiovascular pathways. Using heuristic scoring, we define likely causal variants, and CRISPR prime editing finally determines causal variants for KCNK9, SFXN2, and PCGF6, which are candidates for developing high BP. Our systems-level approach provides a catalog of functionally relevant variants and their genomic architecture in two trait-relevant cell lines for a better understanding of BP gene regulation.

A noncoding single-nucleotide polymorphism at 8q24 drives IDH1-mutant glioma formation.

Establishing causal links between inherited polymorphisms and cancer risk is challenging. Here, we focus on the single-nucleotide polymorphism rs55705857, which confers a sixfold greater risk of isocitrate dehydrogenase (IDH)-mutant low-grade glioma (LGG). We reveal that rs55705857 itself is the causal variant and is associated with molecular pathways that drive LGG. Mechanistically, we show that rs55705857 resides within a brain-specific enhancer, where the risk allele disrupts OCT2/4 binding, allowing increased interaction with the Myc promoter and increased Myc expression. Mutating the orthologous mouse rs55705857 locus accelerated tumor development in an Idh1R132H-driven LGG mouse model from 472 to 172 days and increased penetrance from 30% to 75%. Our work reveals mechanisms of the heritable predisposition to lethal glioma in ~40% of LGG patients.

Microsatellite mutation frequencies in river otters (Lontra Canadensis) from the Athabasca Oil Sands region are correlated to polycyclic aromatic compound tissue burden.

Mining activities in the Athabasca oil sands region (AOSR) have contributed to an increase of polycyclic aromatic compounds (PACs) locally. However, many PACs found in the AOSR, and the combined effects of PAC mixtures have not been evaluated for genotoxicity in wildlife. Here, we examine whether mutation frequencies in AOSR river otters are correlated to PAC tissue burdens. We used single-molecule polymerase chain reaction (SM-PCR) to measure the mutant frequency of unstable DNA microsatellite loci in the bone marrow of wild river otters (n = 11) from the AOSR. Microsatellite mutation frequencies were regressed against liver PAC burden (total, low/high molecular weight [LMW/HMW], and parent/alkylated PACs), and to the distances from where the samples were collected to nearby bitumen upgraders. We found that microsatellite mutation frequency was positively correlated with total liver PAC burden. LMW and alkylated PACs were detected at higher levels and had a stronger positive relationship with mutation frequency than HMW (alkylated and parent) PACs. There were no significant relationships detected between mutation frequency and LMW parent PACs or the distance from bitumen upgraders. Furthermore, pyrogenic and petrogenic signatures suggest PACs in animals with high mutation frequencies were associated with combustion processes; although further investigation is warranted, due to limitations of diagnostic ratio determination with biotic models. Our findings support the hypothesis that PACs found in the AOSR increase mutation frequency in wildlife. Further investigation is required to determine if the elevated PAC levels associated with higher mutation frequency are due to natural exposure or elevated human activity.

Comparative genomic analysis of the 3' UTR of human MDM2 identifies multiple transposable elements, an RLP24 pseudogene and a cluster of novel repeat sequences that arose during primate evolution.

The MDM2 oncogene is a negative regulator of the p53 tumour suppressor. This relationship appears to have originated over a billion years ago. The human MDM2 gene encodes a variety of mRNAs with exceptionally long 3'UTRs (up to 5.7 kb); however, it was unclear whether MDM2 3'UTRs from other species are similarly long or conserved at the sequence level. Here, we report that all but one of the primate species most closely related to humans (greater and lesser apes) have similarly long 3'UTRs with high sequence similarity across their entire length. More distantly related species (Old world monkeys and new world monkeys) tend to have shorter MDM2 3'UTRs homologous to the corresponding position of the human MDM2 3'UTR while non-primate species exhibit little similarity at all. Remarkably, DNA sequences downstream of the shorter primate 3'UTRs are syntenic with distal regions in the human and other ape MDM2 3'UTRs. These homologous non-transcribed intergenic and transcribed 3'UTR-encoding regions are comprised of a variety of transposable elements, an RLP24 pseudogene and a cluster of novel repeat sequences suggestive of another unknown transposable element. Our analysis suggests that the primary difference between long and short MDM2 3'UTRs is a switch in polyA site usage to include conserved transposable elements that remain intergenic in more distantly related primates. It will be important to determine the relative contribution of these elements to post-transcriptional and translational regulation of MDM2 and hence p53-mediated tumour suppression.