Retinoblastoma-associated protein 140 as a candidate for a novel etiological gene to hypertension

Functional Captures of Multiple Human Quantitative Trait Loci Regulating Blood Pressure with the Use of Orthologs in Genetically Defined Rat Models

BACKGROUND

Most signals from human genome-wide association studies (GWAS) for blood pressure (BP) are single-nucleotide polymorphisms (SNPs). It was unknown if such SNPs can functionally affect BP. Because BP is similar between humans and rodents, unraveling basic mechanisms from rodents can reveal the same BP-modulating mechanisms in humans originating from their common ancestors while overcoming limitations in human epidemiology.

METHODS

For the first time, we used quantitative trait loci (QTLs) from Dahl salt-sensitive (DSS) rats as functional surrogates to capture human BP QTLs.

RESULTS

A total of 107 human GWAS genes may be classified into 2 common pathways of hypertension pathogeneses. Among them, 4 DSS BP QTLs correspond to 4 human GWAS genes. Each of them independently showed a major impact on BP in vivo and thus functional redundancy. BP was altered by each of these 4 QTLs, but human GWAS SNPs marking these QTLs do not exist in the rat. They cannot be responsible for physiological changes in BP caused by these QTLs and are genome signposts marking positions of the QTLs nearby, rather than being QTLs themselves. These SNPs appeared during primate evolution, independently of BP regulation. Because the functional dosage of QTLs, not their gene dose, determined hypertension pathogenesis, a role for the noncoding GWAS SNPs in BP via regulating gene expressions can be discounted.

CONCLUSIONS

The human QTLs may function in a common pathway, with each involved in a different step in the pathway leading to BP control. These results may be conceptually paradigm shifting.

Modularity/non-cumulativity of quantitative trait loci on blood pressure

Large numbers of quantitative trait loci (QTLs) for blood pressure (BP) exist and have long been thought to function by accumulating their individual miniscule effects. Recent experimental evidence in the functional biology of BP control has tested this intuitive assumption. A new paradigm has emerged that BP is biologically determined in modularity by multiple QTLs. Functionally, when a master regulator is taken out, distinct epistatic modules organize biological 'blocks' into a genetic architecture, and serve as basic functional cores from which numerous QTLs act together to physiologically formulate BP. An epistatic module refers to the grouping of QTLs that perform their functions epistatically to one another and influence BP as a group. The modularity mechanism framework indicates that BP as a quantitatively-measured trait is not cumulatively determined and implies that the QTLs in the same epistatic module may participate in the same pathway leading to the BP control, and the QTLs from separate epistatic modules may act in divergent but parallel pathways. This mechanistic conceptualization and subsequent validations synergize with anticipated demands from current human epidemiological studies, since the outcome from them primarily implicates single nucleotide polymorphisms with unknown functions. Eventually, functional understandings of the human results have to be realized by their pathogenic directionality and mechanisms biologically controlling BP.

Towards Precision Medicine for Hypertension: A Review of Genomic, Epigenomic, and Microbiomic Effects on Blood Pressure in Experimental Rat Models and Humans

Compelling evidence for the inherited nature of essential hypertension has led to extensive research in rats and humans. Rats have served as the primary model for research on the genetics of hypertension resulting in identification of genomic regions that are causally associated with hypertension. In more recent times, genome-wide studies in humans have also begun to improve our understanding of the inheritance of polygenic forms of hypertension. Based on the chronological progression of research into the genetics of hypertension as the "structural backbone," this review catalogs and discusses the rat and human genetic elements mapped and implicated in blood pressure regulation. Furthermore, the knowledge gained from these genetic studies that provide evidence to suggest that much of the genetic influence on hypertension residing within noncoding elements of our DNA and operating through pervasive epistasis or gene-gene interactions is highlighted. Lastly, perspectives on current thinking that the more complex "triad" of the genome, epigenome, and the microbiome operating to influence the inheritance of hypertension, is documented. Overall, the collective knowledge gained from rats and humans is disappointing in the sense that major hypertension-causing genes as targets for clinical management of essential hypertension may not be a clinical reality. On the other hand, the realization that the polygenic nature of hypertension prevents any single locus from being a relevant clinical target for all humans directs future studies on the genetics of hypertension towards an individualized genomic approach.

Genome-wide association analysis identifies novel blood pressure loci and offers biological insights into cardiovascular risk

Elevated blood pressure is the leading heritable risk factor for cardiovascular disease worldwide. We report genetic association of blood pressure (systolic, diastolic, pulse pressure) among UK Biobank participants of European ancestry with independent replication in other cohorts, and robust validation of 107 independent loci. We also identify new independent variants at 11 previously reported blood pressure loci. In combination with results from a range of in silico functional analyses and wet bench experiments, our findings highlight new biological pathways for blood pressure regulation enriched for genes expressed in vascular tissues and identify potential therapeutic targets for hypertension. Results from genetic risk score models raise the possibility of a precision medicine approach through early lifestyle intervention to offset the impact of blood pressure-raising genetic variants on future cardiovascular disease risk.