Susceptibility to coronary artery disease (CAD) is claimed to be 40% to 60% inherited, but until recently genetic risk factors predisposing to CAD have been elusive. Comprehensive prevention of CAD ...requires manipulation of genetic risk. The availability of microarrays of single-nucleotide polymorphisms enabling genome-wide association studies (GWAS) led to the discovery of 33 genetic risk variants for CAD. Surprisingly, 23 risk variants mediate their risk through unknown mechanisms, with only 10 associating with hypertension or lipids. Thus, there are several mechanisms contributing to the pathogenesis of CAD yet to be elucidated. The first risk variant discovered by GWAS was 9p21.3, which occurs in 75% of all populations except African, with a mean increased risk of 25% per copy. Of the 33 variants for CAD, the increased risk varies from 6% to 92% with a mean increased risk of 18%, occurring on average in 47% of the population. The maximum number of risk alleles per individual would be 66. In the CARDIoGRAM (Coronary Artery Disease Genome-wide Replication and Meta Analysis) study of 23 variants, the average per individual was 17, the minimum 7, and the maximum 37. The top 10th percentile has an odds ratio of 1.88 and the lowest percentile an odds ratio of 0.55. Routine genetic screening is unlikely until management is improved by genetic testing. Risk variants should provide pathophysiological insights and targets for novel therapy. While risk variants are less potent predictors of CAD, compared with biomarkers, they have the advantage of not changing in one's lifetime and are unaffected by diet, sex, age, or medication.
Collapse of endocannabinoid (eCB) signaling in the amygdala contributes to stress-induced anxiety, but the mechanisms of this effect remain unclear. eCB production is tied to the function of the ...glutamate receptor mGluR5, itself dependent on tyrosine phosphorylation. Herein, we identify a novel pathway linking eCB regulation of anxiety through phosphorylation of mGluR5. Mice lacking LMO4, an endogenous inhibitor of the tyrosine phosphatase PTP1B, display reduced mGluR5 phosphorylation, eCB signaling, and profound anxiety that is reversed by genetic or pharmacological suppression of amygdalar PTP1B. Chronically stressed mice exhibited elevated plasma corticosterone, decreased LMO4 palmitoylation, elevated PTP1B activity, reduced amygdalar eCB levels, and anxiety behaviors that were restored by PTP1B inhibition or by glucocorticoid receptor antagonism. Consistently, corticosterone decreased palmitoylation of LMO4 and its inhibition of PTP1B in neuronal cells. Collectively, these data reveal a stress-responsive corticosterone-LMO4-PTP1B-mGluR5 cascade that impairs amygdalar eCB signaling and contributes to the development of anxiety.
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•Mice with ablation of an endogenous PTP1B inhibitor LMO4 have anxiety•PTP1B dephosphorylates mGluR5 and impairs mGluR5-mediated eCB production•Glucocorticoids impair LMO4 palmitoylation and increase PTP1B activity•PTP1B inhibition in the amygdala restores eCBs and relieves stress-induced anxiety
Collapse of endocannabinoid signaling in the amygdala underlies stress-induced anxiety. Qin et al. present a mechanism whereby stress (glucocorticoid) causes loss of LMO4-dependent inhibition of tyrosine phosphatase PTP1B that impairs mGluR5-mediated endocannabinoid production. Suppressing amygdalar PTP1B rescues stress-induced anxiety.
We have investigated the functional significance of conserved sequences within the 9p21.3 risk locus for coronary artery disease (CAD) and determined the relationship of 9p21.3 to expression of ANRIL ...and to whole genome gene expression.
We demonstrate that a conserved sequence within the 9p21.3 locus has enhancer activity and that the risk variant significantly increases reporter gene expression in primary aortic smooth muscle cells. Whole blood RNA expression of the short variants of ANRIL was increased by 2.2-fold whereas expression of the long ANRIL variant was decreased by 1.2-fold in healthy subjects homozygous for the risk allele. Expression levels of the long and short ANRIL variants were positively correlated with that of the cyclin-dependent kinase inhibitor, CDKN2B (p15) and TDGF1 (Cripto), respectively. Relevant to atherosclerosis, genome-wide expression profiling demonstrated upregulation of gene sets modulating cellular proliferation in carriers of the risk allele.
These findings are consistent with the hypothesis that the 9p21.3 risk allele contains a functional enhancer, the activity of which is altered in carriers of the risk allele. 9p21.3 may promote atherosclerosis by regulating expression of ANRIL, which in turn is associated with altered expression of genes controlling cellular proliferation pathways.
Individuals with autism spectrum disorder (ASD) have social interaction deficits and difficulty filtering information. Inhibitory interneurons filter information at pyramidal neurons of the anterior ...cingulate cortex (ACC), an integration hub for higher-order thalamic inputs important for social interaction. Humans with deletions including LMO4, an endogenous inhibitor of PTP1B, display intellectual disabilities and occasionally autism. PV-Lmo4KO mice ablate Lmo4 in PV interneurons and display ASD-like repetitive behaviors and social interaction deficits. Surprisingly, increased PV neuron-mediated peri-somatic feedforward inhibition to the pyramidal neurons causes a compensatory reduction in (somatostatin neuron-mediated) dendritic inhibition. These homeostatic changes increase filtering of mediodorsal-thalamocortical inputs but reduce filtering of cortico-cortical inputs and narrow the range of stimuli ACC pyramidal neurons can distinguish. Simultaneous ablation of PTP1B in PV-Lmo4KO neurons prevents these deficits, indicating that PTP1B activation in PV interneurons contributes to ASD-like characteristics and homeostatic maladaptation of inhibitory circuits may contribute to deficient information filtering in ASD.
Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a circulating protein that promotes degradation of the low density lipoprotein (LDL) receptor. Mutations that block PCSK9 secretion reduce ...LDL-cholesterol and the incidence of myocardial infarction (MI). However, it remains unclear whether elevated plasma PCSK9 associates with coronary atherosclerosis (CAD) or more directly with rupture of the plaque causing MI.
Plasma PCSK9 was measured by ELISA in 645 angiographically defined controls (<30% coronary stenosis) and 3,273 cases of CAD (>50% stenosis in a major coronary artery) from the Ottawa Heart Genomics Study. Because lipid lowering medications elevated plasma PCSK9, confounding association with disease, only individuals not taking a lipid lowering medication were considered (279 controls and 492 with CAD). Replication was sought in 357 controls and 465 with CAD from the Emory Cardiology Biobank study. PCSK9 levels were not associated with CAD in Ottawa, but were elevated with CAD in Emory. Plasma PCSK9 levels were elevated in 45 cases with acute MI (363.5±140.0 ng/ml) compared to 398 CAD cases without MI (302.0±91.3 ng/ml, p = 0.004) in Ottawa. This finding was replicated in the Emory study in 74 cases of acute MI (445.0±171.7 ng/ml) compared to 273 CAD cases without MI (369.9±139.1 ng/ml, p = 3.7×10(-4)). Since PCSK9 levels were similar in CAD patients with or without a prior (non-acute) MI, our finding suggests that plasma PCSK9 is elevated either immediately prior to or at the time of MI.
Plasma PCSK9 levels are increased with acute MI.
Diminished serum paraoxonase and arylesterase activities (measures of paraoxonase-1 PON-1 function) in humans have been linked to heightened systemic oxidative stress and atherosclerosis risk. The ...clinical prognostic use of measuring distinct PON-1 activities has not been established, and the genetic determinants of PON-1 activities are not known.
We established analytically robust high-throughput assays for serum paraoxonase and arylesterase activities and measured these in 3668 stable subjects undergoing elective coronary angiography without acute coronary syndrome and were prospectively followed for major adverse cardiovascular events (MACE= death, myocardial infarction, stroke) over 3 years. Low serum arylesterase and paraoxonase activities were both associated with increased risk for MACE, with arylesterase activity showing greatest prognostic value (quartile 4 versus quartile 1; hazard ratio 2.63; 95% CI, 1.97-3.50; P<0.01). Arylesterase remained significant after adjusting for traditional risk factors, C-reactive protein, and creatinine clearance (hazard ratio, 2.20; 95% CI, 1.60-3.02; P<0.01), predicted future development of MACE in both primary and secondary prevention populations, and reclassified risk categories incrementally to traditional clinical variables. A genome-wide association study identified distinct single nucleotide polymorphisms within the PON-1 gene that were highly significantly associated with serum paraoxonase (1.18×10(-303)) or arylesterase (4.99×10(-116)) activity but these variants were not associated with either 3-year MACE risk in an angiographic cohort (n=2136) or history of either coronary artery disease or myocardial infarction in the Coronary Artery Disease Genome-Wide Replication and Meta-Analysis consortium (n≈80 000 subjects).
Diminished serum arylesterase activity, but not the genetic determinants of PON-1 functional measures, provides incremental prognostic value and clinical reclassification of stable subjects at risk of developing MACE.
Left-sided congenital heart disease (CHD) encompasses a spectrum of malformations that range from bicuspid aortic valve to hypoplastic left heart syndrome. It contributes significantly to infant ...mortality and has serious implications in adult cardiology. Although left-sided CHD is known to be highly heritable, the underlying genetic determinants are largely unidentified. In this study, we sought to determine the impact of structural genomic variation on left-sided CHD and compared multiplex families (464 individuals with 174 affecteds (37.5%) in 59 multiplex families and 8 trios) to 1,582 well-phenotyped controls. 73 unique inherited or de novo CNVs in 54 individuals were identified in the left-sided CHD cohort. After stringent filtering, our gene inventory reveals 25 new candidates for LS-CHD pathogenesis, such as SMC1A, MFAP4, and CTHRC1, and overlaps with several known syndromic loci. Conservative estimation examining the overlap of the prioritized gene content with CNVs present only in affected individuals in our cohort implies a strong effect for unique CNVs in at least 10% of left-sided CHD cases. Enrichment testing of gene content in all identified CNVs showed a significant association with angiogenesis. In this first family-based CNV study of left-sided CHD, we found that both co-segregating and de novo events associate with disease in a complex fashion at structural genomic level. Often viewed as an anatomically circumscript disease, a subset of left-sided CHD may in fact reflect more general genetic perturbations of angiogenesis and/or vascular biology.
Schizophrenia is a debilitating disorder affecting young adults displaying symptoms of cognitive impairment, anxiety, and early social isolation prior to episodes of auditory hallucinations. Cannabis ...use has been tied to schizophrenia-like symptoms, indicating that dysregulated endogenous cannabinoid signaling may be causally linked to schizophrenia. Previously, we reported that glutamatergic neuron-selective ablation of Lmo4, an endogenous inhibitor of the tyrosine phosphatase PTP1B, impairs endocannabinoid (eCB) production from the metabotropic glutamate receptor mGluR5. These Lmo4-deficient mice display anxiety-like behaviors that are alleviated by local shRNA knockdown or pharmacological inhibition of PTP1B that restores mGluR5-dependent eCB production in the amygdala. Here, we report that these Lmo4-deficient mice also display schizophrenia-like behaviors: impaired working memory assessed in the Y maze and defective sensory gating by prepulse inhibition of the acoustic startle response. Modulation of inhibitory inputs onto layer 2/3 pyramidal neurons of the prefrontal cortex relies on eCB signaling from the brain-derived neurotrophic factor receptor trkB, rather than mGluR5, and this mechanism was defective in Lmo4-deficient mice. Genetic ablation of PTP1B in the glutamatergic neurons lacking Lmo4 restored tyrosine phosphorylation of trkB, trkB-mediated eCB signaling, and ameliorated schizophrenia-like behaviors. Pharmacological inhibition of PTP1B with trodusquemine also restored trkB phosphorylation and improved schizophrenia-like behaviors by restoring eCB signaling, since the CB1 receptor antagonist 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide blocked this effect. Thus, activation of PTP1B in pyramidal neurons contributes to schizophrenia-like behaviors in Lmo4-deficient mice and genetic or pharmacological intervention targeting PTP1B ameliorates schizophrenia-related deficits.
Alzheimer's disease (AD) is the most common neurodegenerative disorder, resulting in the progressive decline of cognitive function in patients. Familial forms of AD are tied to mutations in the ...amyloid precursor protein, but the cellular mechanisms that cause AD remain unclear. Inflammation and amyloidosis from amyloid β (Aβ) aggregates are implicated in neuron loss and cognitive decline. Inflammation activates the protein-tyrosine phosphatase 1B (PTP1B), and this could suppress many signaling pathways that activate glycogen synthase kinase 3β (GSK3β) implicated in neurodegeneration. However, the significance of PTP1B in AD pathology remains unclear. Here, we show that pharmacological inhibition of PTP1B with trodusquemine or selective ablation of PTP1B in neurons prevents hippocampal neuron loss and spatial memory deficits in a transgenic AD mouse model with Aβ pathology (hAPP-J20 mice of both sexes). Intriguingly, while systemic inhibition of PTP1B reduced inflammation in the hippocampus, neuronal PTP1B ablation did not. These results dissociate inflammation from neuronal loss and cognitive decline and demonstrate that neuronal PTP1B hastens neurodegeneration and cognitive decline in this model of AD. The protective effect of PTP1B inhibition or ablation coincides with the restoration of GSK3β inhibition. Neuronal ablation of PTP1B did not affect cerebral amyloid levels or plaque numbers, but reduced Aβ plaque size in the hippocampus. In summary, our preclinical study suggests that targeting PTP1B may be a new strategy to intervene in the progression of AD.
Familial forms of Alzheimer's disease (AD) are tied to mutations in the amyloid precursor protein, but the cellular mechanisms that cause AD remain unclear. Here, we used a mouse model expressing human amyloid precursor protein bearing two familial mutations and asked whether activation of a phosphatase PTP1B participates in the disease process. Systemic inhibition of this phosphatase using a selective inhibitor prevented cognitive decline, neuron loss in the hippocampus, and attenuated inflammation. Importantly, neuron-targeted ablation of PTP1B also prevented cognitive decline and neuron loss but did not reduce inflammation. Therefore, neuronal loss rather than inflammation was critical for AD progression in this mouse model, and that disease progression could be ameliorated by inhibition of PTP1B.
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