The progeroid phenotype of Ku80 deficiency Is dominant over DNA-PK CS deficiency

Ku80 and DNA-PKCS are both involved in the repair of double strand DNA breaks via the nonhomologous end joining (NHEJ) pathway. While ku80-/- mice exhibit a severely reduced lifespan and size, this phenotype is less pronounced in dna-pkcs -/- mice. However, these observations are based on independent studies with varying genetic backgrounds. Here, we generated ku80-/-, dna-pkcs -/- and double knock out mice in a C57Bl6/J*FVB F1 hybrid background and compared their lifespan, end of life pathology and mutation frequency in liver a

Deletion of individual Ku subunits in mice causes an NHEJ-independent phenotype potentially by altering apurinic/apyrimidinic site repair

Ku70 and Ku80 form a heterodimer called Ku that forms a holoenzyme with DNA dependent-protein kinase catalytic subunit (DNA-PKCS) to repair DNA double strand breaks (DSBs) through the nonhomologous end joining (NHEJ) pathway. As expected mutating these genes in mice caused a similar DSB repair-defective phenotype. However, ku70-/- cells and ku80 -/- cells also appeared to have a defect in base excision repair (BER). BER corrects base lesions, apurinic/apyrimidinic (AP) sites and single stand breaks (SSBs) utilizing a variety of proteins including glycosylases, AP endonuclease 1 (APE1) and DNA Polymerase β (Pol β). In addition, deleting Ku70 was not equivalent to deleting Ku80 in cells and mice. Therefore, we hypothesized that free Ku70 (not bound to Ku80) and/or free Ku80 (not bound to Ku70) possessed activity that influenced BER. To further test this hypothesis we performed two general sets of experiments. The first set showed that deleting either Ku70 or Ku80 caused an NHEJ-independent defect. We found ku80-/- mice had a shorter life span than dna-pkcs-/- mice demonstrating a phenotype that was greater than deleting the holoenzyme. We also found Ku70-deletion induced a p53 response that reduced the level of small mutations in the brain suggesting defective BER. We further confirmed that Ku80-deletion impaired BER via a mechanism that was not epistatic to Pol β. The second set of experiments showed that free Ku70 and free Ku80 could influence BER. We observed that deletion of either Ku70 or Ku80, but not both, increased sensitivity of cells to CRT0044876 (CRT), an agent that interferes with APE1. In addition, free Ku70 and free Ku80 bound to AP sites and in the case of Ku70 inhibited APE1 activity. These observations support a novel role for free Ku70 and free Ku80 in altering BER. © 2014 Choi et al

Common Variants in the Type 2 Diabetes KCNQ1 Gene Are Associated with Impairments in Insulin Secretion During Hyperglycaemic Glucose Clamp

Background: Genome-wide association studies in Japanese populations recently identified common variants in the KCNQ1 gene to be associated with type 2 diabetes. We examined the association of these variants within KCNQ1 with type 2 diabetes in a Dutch population, investigated their effects on insulin secretion and metabolic traits and on the risk of developing complications in type 2 diabetes patients. Methodology: The KCNQ1 variants rs151290, rs2237892, and rs2237895 were genotyped in a total of 4620 type 2 diabetes patients and 5285 healthy controls from the Netherlands. Data on macrovascular complications, nephropathy and retinopathy were available in a subset of diabetic patients. Association between genotype and insulin secretion/action was assessed in the additional sample of 335 individuals who underwent a hyperglycaemic clamp. Principal Findings: We found that all the genotyped KCNQ1 variants were significantly associated with type 2 diabetes in our Dutch population, and the association of rs151290 was the strongest (OR 1.20, 95% CI 1.07-1.35, p = 0.002). The risk C-allele of rs151290 was nominally associated with reduced first-phase glucose-stimulated insulin secretion, while the non-risk T-allele of rs2237892 was significantly correlated with increased second-phase glucose-stimulated insulin secretion (p = 0.025 and 0.0016, respectively). In addition, the risk C-allele of rs2237892 was associated with higher LDL and total cholesterol levels (p = 0.015 and 0.003, respectively). We found no evidence for an association of KCNQ1 with diabetic complications. Conclusions: Common variants in the KCNQ1 gene are associated with type 2 diabetes in a Dutch population, which can be explained at least in part by an effect on insulin secretion. Furthermore, our data suggest that KCNQ1 is also associated with lipid metabolism

Abstract 510: Dietary Restriction Improves Vasodilator Dysfunction Caused by Accelerated Vascular Aging Due to Genomic Instability

Objective Recently we discovered that genomic instability is associated with accelerated vascular aging in humans and mouse models, and that DNA repair-defective mice ( ERCC1 -/ Δ 7 ) display accelerated age-dependent deterioration of endothelium-dependent and vascular smooth muscle dilator function (Durik M. et al. Circulation 2012). Dietary restriction ( DR ) is known to slow aging. We explored whether DR would inhibit accelerated vascular aging caused by genomic instability by measuring vasodilator function in both male and female ERCC1 -/ Δ 7 mice vs. wild-type (WT) littermates. Methods WT and ERCC1 -/ Δ 7 were fed with DR (increasing 10 to 30% nutrient restriction) or ad libitum ( AL ) diets for 9 weeks, whereafter thoracic aortas were isolated and used for ex vivo organ bath experiments. To investigate endothelial and vascular smooth muscle dilator function, aorta preconstricted with U44619 (thromboxane analogue) was exposed to acetylcholine (Ach: 10 -9 -10 -5 M) and sodium nitroprusside (SNP: 10 -9 -10 -4 M), respectively. Maximal dilator responses (mean+/-SEM) are shown between brackets, and were calculated as % decrease of precontraction. Significance values are those of dose-related responses tested by general linear model for repeated measures. Results In ERCC1 -/ Δ 7 mice fed AL both ACh and SNP responses were significantly smaller than in WT (Ach: 66.89+/-8.9% (n=8) vs. 41.45+/-4.74% (n=11); SNP: 80.27+/-4.89% (n=5) vs. 59.35+/-3.32% (n=5), p &lt;0.0001, WT vs. ERCC1 -/ Δ 7 ) with no gender differences. Whilst without effect in WT, DR normalized the SNP responses of ERCC1 -/ Δ 7 (79.60+/-7.09% (n=6)) to that of WT gender-independently. ACh responses were also improved (from 41.45+/-4.74% AL (n=11) to 56.02+/-4.73% DR (n=11)), but most pronounced in female ERCC1 -/ Δ 7 (38.33+/-8.39% AL (n=4) vs. -67.31+/-6.22% DR (n=4) , p &lt;0.0001). Conclusion In ERCC1 -/Δ7 mice, DR improved vasodilator response in both genders. Endothelial function might be improved only efficiently in female mice, whilst the NO-mediated dilation of VSMC is improved equally well in both genders. Therefore, DR is beneficial for vascular function during vascular aging caused by genomic instability, and its impact on EC versus VSMC appears to be gender-dependent. </jats:p

The progeroid phenotype of Ku80 deficiency Is dominant over DNA-PK CS deficiency

Ku80 and DNA-PKCS are both involved in the repair of double strand DNA breaks via the nonhomologous end joining (NHEJ) pathway. While ku80-/- mice exhibit a severely reduced lifespan and size, this phenotype is less pronounced in dna-pkcs -/- mice. However, these observations are based on independent studies with varying genetic backgrounds. Here, we generated ku80-/-, dna-pkcs -/- and double knock out mice in a C57Bl6/J*FVB F1 hybrid background and compared their lifespan, end of life pathology and mutation frequency in liver a

Human TP53 polymorphism (rs1042522) modelled in mouse does not affect glucose metabolism and body composition

Variation in TP53 has been associated with cancer. The pro-allele of a TP53 polymorphism in codon 72 (rs1042522) has been associated with longevity. Recently, we showed that the same allele might be involved in preservation of glucose metabolism, body composition and blood pressure during ageing. Here, we assessed glucose tolerance and body composition in mice carrying the human polymorphism. Our data do not support the previous findings in humans, suggesting that this polymorphism does not play a major role in development of glucose metabolism and body composition during ageing. Alternatively, the mouse model may not be suitable to validate these rs1042522-associated traits up to the age tested