Drug-induced loss of imprinting revealed using bioluminescent reporters of Cdkn1c.

Genomic imprinting is an epigenetically mediated mechanism that regulates allelic expression of genes based upon parent-of-origin and provides a paradigm for studying epigenetic silencing and release. Here, bioluminescent reporters for the maternally-expressed imprinted gene Cdkn1c are used to examine the capacity of chromatin-modifying drugs to reverse paternal Cdkn1c silencing. Exposure of reporter mouse embryonic stem cells (mESCs) to 5-Azacytidine, HDAC inhibitors, BET inhibitors or GSK-J4 (KDM6A/B inhibitor) relieved repression of paternal Cdkn1c, either selectively or by inducing biallelic effects. Treatment of reporter fibroblasts with HDAC inhibitors or GSK-J4 resulted in similar paternal Cdkn1c activation, whereas BET inhibitor-induced loss of imprinting was specific to mESCs. Changes in allelic expression were generally not sustained in dividing cultures upon drug removal, indicating that the underlying epigenetic memory of silencing was maintained. In contrast, Cdkn1c de-repression by GSK-J4 was retained in both mESCs and fibroblasts following inhibitor removal, although this impact may be linked to cellular stress and DNA damage. Taken together, these data introduce bioluminescent reporter cells as tools for studying epigenetic silencing and disruption, and demonstrate that Cdkn1c imprinting requires distinct and cell-type specific chromatin features and modifying enzymes to enact and propagate a memory of silencing.

Cardiovascular Risk Factors and MRI Markers of Cerebral Small Vessel Disease: A Mendelian Randomization Study.

OBJECTIVE-: Cardiovascular risk factors have been implicated in the etiology of Cerebral Small Vessel Disease (CSVD), however whether the associations are causal remains unclear in part due to the susceptibility of observational studies to reverse causation and confounding. Here we use Mendelian randomization (MR) to determine which cardiovascular risk factors are likely to be involved in the etiology of CSVD. METHODS-: We used data from large scale genome-wide association studies (GWAS) of European ancestry to identify genetic proxies for blood pressure, blood lipids, body mass index (BMI), type-II diabetes, smoking initiation, cigarettes per day and alcohol consumption. MR was performed to assess their association with three neuroimaging features which are altered in CSVD (white matter hyperintensities (WMH), fractional anisotropy (FA) and mean diffusivity (MD)) using genetic summary data from UK Biobank (N=31,855). Our primary analysis used inverse-weighted median (IVW) MR, with validation using weighted median, MR-Egger and a pleiotropy-minimizing approach. Finally, multivariable MR was performed to study the effects of multiple risk factors jointly. RESULTS-: MR analysis showed consistent associations across all methods for higher genetically proxied systolic and diastolic blood pressure with WMH, FA, and MD; and for higher genetically proxied BMI with WMH. There was weaker evidence for associations between total cholesterol, LDL, smoking initiation, pulse pressure and type-II diabetes liability and at least one CSVD imaging feature, but these associations were not reproducible across all validation methods used. Multivariable MR analysis for blood pressure traits found that the effect was primarily through genetically proxied diastolic blood pressure across all CSVD traits. CONCLUSION-: Genetic predisposition to higher blood pressure, primarily diastolic blood pressure, and higher BMI is associated with a higher burden of CSVD, suggesting a causal role. Improved management and treatment of these risk factors could reduce the burden of CSVD.

Hypertension genetics past, present and future applications.

Essential hypertension is a complex trait where the underlying aetiology is not completely understood. Left untreated it increases the risk of severe health complications including cardiovascular and renal disease. It is almost 15 years since the first genome-wide association study for hypertension, and after a slow start there are now over 1000 blood pressure (BP) loci explaining ∼6% of the single nucleotide polymorphism-based heritability. Success in discovery of hypertension genes has provided new pathological insights and drug discovery opportunities and translated to the development of BP genetic risk scores (GRSs), facilitating population disease risk stratification. Comparing highest and lowest risk groups shows differences of 12.9 mm Hg in systolic-BP with significant differences in risk of hypertension, stroke, cardiovascular disease and myocardial infarction. GRSs are also being trialled in antihypertensive drug responses. Drug targets identified include NPR1, for which an agonist drug is currently in clinical trials. Identification of variants at the PHACTR1 locus provided insights into regulation of EDN1 in the endothelin pathway, which is aiding the development of endothelin receptor EDNRA antagonists. Drug re-purposing opportunities, including SLC5A1 and canagliflozin (a type-2 diabetes drug), are also being identified. In this review, we present key studies from the past, highlight current avenues of research and look to the future focusing on gene discovery, epigenetics, gene-environment interactions, GRSs and drug discovery. We evaluate limitations affecting BP genetics, including ancestry bias and discuss streamlining of drug target discovery and applications for treating and preventing hypertension, which will contribute to tailored precision medicine for patients.

Metabolic Signatures of Gestational Weight Gain and Postpartum Weight Loss in a Lifestyle Intervention Study of Overweight and Obese Women.

BACKGROUND: Overweight and obesity amongst women of reproductive age are increasingly common in developed economies and are shown to adversely affect birth outcomes and both childhood and adulthood health risks in the offspring. Metabolic profiling in conditions of overweight and obesity in pregnancy could potentially be applied to elucidate the molecular basis of the adverse effects of gestational weight gain (GWG) and postpartum weight loss (WL) on future risks for cardiovascular disease (CVD) and other chronic diseases. METHODS: Biofluid samples were collected from 114 ethnically diverse pregnant women with body mass index (BMI) between 25 and 40 kg/m2 from Chicago (US), as part of a randomized lifestyle intervention trial (Maternal Offspring Metabolics: Family Intervention Trial; NCT01631747). At 15 weeks, 35 weeks of gestation, and at 1 year postpartum, the blood plasma lipidome and metabolic profile of urine samples were analyzed by liquid chromatography mass spectrometry (LC-MS) and 1H nuclear magnetic resonance spectroscopy (1H NMR) respectively. RESULTS: Urinary 4-deoxyerythronic acid and 4-deoxythreonic acid were found to be positively correlated to BMI. Seventeen plasma lipids were found to be associated with GWG and 16 lipids were found to be associated with WL, which included phosphatidylinositols (PI), phosphatidylcholines (PC), lysophospholipids (lyso-), sphingomyelins (SM) and ether phosphatidylcholine (PC-O). Three phospholipids found to be positively associated with GWG all contained palmitate side-chains, and amongst the 14 lipids that were negatively associated with GWG, seven were PC-O. Six of eight lipids found to be negatively associated with WL contained an 18:2 fatty acid side-chain. CONCLUSIONS: Maternal obesity was associated with characteristic urine and plasma metabolic phenotypes, and phospholipid profile was found to be associated with both GWG and postpartum WL in metabolically healthy pregnant women with overweight/obesity. Postpartum WL may be linked to the reduction in the intake of linoleic acid/conjugated linoleic acid food sources in our study population.