8 research outputs found
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Affinity-optimizing enhancer variants disrupt development
Enhancers control the location and timing of gene expression and contain the majority of variants associated with disease1-3. The ZRS is arguably the most well-studied vertebrate enhancer and mediates the expression of Shh in the developing limb4. Thirty-one human single-nucleotide variants (SNVs) within the ZRS are associated with polydactyly4-6. However, how this enhancer encodes tissue-specific activity, and the mechanisms by which SNVs alter the number of digits, are poorly understood. Here we show that the ETS sites within the ZRS are low affinity, and identify a functional ETS site, ETS-A, with extremely low affinity. Two human SNVs and a synthetic variant optimize the binding affinity of ETS-A subtly from 15% to around 25% relative to the strongest ETS binding sequence, and cause polydactyly with the same penetrance and severity. A greater increase in affinity results in phenotypes that are more penetrant and more severe. Affinity-optimizing SNVs in other ETS sites in the ZRS, as well as in ETS, interferon regulatory factor (IRF), HOX and activator protein 1 (AP-1) sites within a wide variety of enhancers, cause gain-of-function gene expression. The prevalence of binding sites with suboptimal affinity in enhancers creates a vulnerability in genomes whereby SNVs that optimize affinity, even slightly, can be pathogenic. Searching for affinity-optimizing SNVs in genomes could provide a mechanistic approach to identify causal variants that underlie enhanceropathies
Exercise, vascular stiffness, and tissue transglutaminase
Background: Vascular aging is closely associated with increased vascular stiffness. It has recently been demonstrated that decreased nitric oxide (NO)-induced S-nitrosylation of tissue transglutaminase (TG2) contributes to age-related vascular stiffness. In the current study, we tested the hypothesis that exercise restores NO signaling and attenuates vascular stiffness by decreasing TG2 activity and cross-linking in an aging rat model. Methods and Results: Rats were subjected to 12 weeks of moderate aerobic exercise. Aging was associated with diminished phosphorylated endothelial nitric oxide synthase and phosphorylated vasodilator-stimulated phosphoprotein abundance, suggesting reduced NO signaling. TG2 cross-linking activity was significantly increased in old animals, whereas TG2 abundance remained unchanged. These alterations were attenuated in the exercise cohort. Simultaneous measurement of blood pressure and pulse wave velocity (PWV) demonstrated increased aortic stiffness in old rats, compared to young, at all values of mean arterial pressure (MAP). The PWV-MAP correlation in the old sedentary and old exercise cohorts was similar. Tensile testing of the vessels showed increased stiffness of the aorta in the old phenotype with a modest restoration of mechanical properties toward the young phenotype with exercise. Conclusions: Increased vascular stiffness during aging is associated with decreased TG2 S-nitrosylation, increased TG2 crosslinking activity, and increased vascular stiffness likely the result of decreased NO bioavailability. In this study, a brief period of moderate aerobic exercise enhanced NO signaling, attenuated TG cross-linking activity, and reduced ex vivo tensile properties, but failed to reverse functional vascular stiffness in vivo, as measured by PWV.10 page(s
Increased tissue transglutaminase activity contributes to central vascular stiffness in eNOS knockout mice
Nitric oxide (NO) can modulate arterial stiffness by regulating both functional and structural changes in the arterial wall. Tissue transglutaminase (TG2) has been shown to contribute to increased central aortic stiffness by catalyzing the cross-linking of matrix proteins. NO S-nitrosylates and constrains TG2 to the cytosolic compartment and thereby holds its cross-linking function latent. In the present study, the role of endothelial NO synthase (eNOS)-derived NO in regulating TG2 function was studied using eNOS knockout mice. Matrix-associated TG2 and TG2 crosslinking function were higher, whereas TG2 S-nitrosylation was lower in the eNOS-/- compared with wild-type (WT) mice. Pulse-wave velocity (PWV) and blood pressure measured noninvasively were elevated in the eNOS-/- compared with WT mice. Intact aortas and decellularized aortic tissue scaffolds of eNOS-/- mice were significantly stiffer, as determined by tensile testing. The carotid arteries of the eNOS-/- mice were also stiffer, as determined by pressuredimension analysis. Invasive methods to determine the PWV-mean arterial pressure relationship showed that PWV in eNOS-/- and WT diverge at higher mean arterial pressure. Thus eNOS-derived NO regulates TG2 localization and function and contributes to vascular stiffness