Characterization of direct and/or indirect genetic associations for multiple traits in longitudinal studies of disease progression.

When quantitative longitudinal traits are risk factors for disease progression and subject to random biological variation, joint model analysis of time-to-event and longitudinal traits can effectively identify direct and/or indirect genetic association of single nucleotide polymorphisms (SNPs) with time-to-event. We present a joint model that integrates: (1) a multivariate linear mixed model describing trajectories of multiple longitudinal traits as a function of time, SNP effects, and subject-specific random effects and (2) a frailty Cox survival model that depends on SNPs, longitudinal trajectory effects, and subject-specific frailty accounting for dependence among multiple time-to-event traits. Motivated by complex genetic architecture of type 1 diabetes complications (T1DC) observed in the Diabetes Control and Complications Trial (DCCT), we implement a 2-stage approach to inference with bootstrap joint covariance estimation and develop a hypothesis testing procedure to classify direct and/or indirect SNP association with each time-to-event trait. By realistic simulation study, we show that joint modeling of 2 time-to-T1DC (retinopathy and nephropathy) and 2 longitudinal risk factors (HbA1c and systolic blood pressure) reduces estimation bias in genetic effects and improves classification accuracy of direct and/or indirect SNP associations, compared to methods that ignore within-subject risk factor variability and dependence among longitudinal and time-to-event traits. Through DCCT data analysis, we demonstrate feasibility for candidate SNP modeling and quantify effects of sample size and Winner's curse bias on classification for 2 SNPs identified as having indirect associations with time-to-T1DC traits. Joint analysis of multiple longitudinal and multiple time-to-event traits provides insight into complex traits architecture.

Acute ACAT1/SOAT1 Blockade Increases MAM Cholesterol and Strengthens ER-Mitochondria Connectivity.

Cholesterol is a key component of all mammalian cell membranes. Disruptions in cholesterol metabolism have been observed in the context of various diseases, including neurodegenerative disorders such as Alzheimer's disease (AD). The genetic and pharmacological blockade of acyl-CoA:cholesterol acyltransferase 1/sterol O-acyltransferase 1 (ACAT1/SOAT1), a cholesterol storage enzyme found on the endoplasmic reticulum (ER) and enriched at the mitochondria-associated ER membrane (MAM), has been shown to reduce amyloid pathology and rescue cognitive deficits in mouse models of AD. Additionally, blocking ACAT1/SOAT1 activity stimulates autophagy and lysosomal biogenesis; however, the exact molecular connection between the ACAT1/SOAT1 blockade and these observed benefits remain unknown. Here, using biochemical fractionation techniques, we observe cholesterol accumulation at the MAM which leads to ACAT1/SOAT1 enrichment in this domain. MAM proteomics data suggests that ACAT1/SOAT1 inhibition strengthens the ER-mitochondria connection. Confocal and electron microscopy confirms that ACAT1/SOAT1 inhibition increases the number of ER-mitochondria contact sites and strengthens this connection by shortening the distance between these two organelles. This work demonstrates how directly manipulating local cholesterol levels at the MAM can alter inter-organellar contact sites and suggests that cholesterol buildup at the MAM is the impetus behind the therapeutic benefits of ACAT1/SOAT1 inhibition.

Pattern of tamoxifen-induced Tie2 deletion in endothelial cells in mature blood vessels using endo SCL-Cre-ERT transgenic mice.

Tyrosine-protein kinase receptor Tie2, also known as Tunica interna Endothelial cell Kinase or TEK plays a prominent role in endothelial responses to angiogenic and inflammatory stimuli. Here we generated a novel inducible Tie2 knockout mouse model, which targets mature (micro)vascular endothelium, enabling the study of the organ-specific contribution of Tie2 to these responses. Mice with floxed Tie2 exon 9 alleles (Tie2floxed/floxed) were crossed with end-SCL-Cre-ERT transgenic mice, generating offspring in which Tie2 exon 9 is deleted in the endothelial compartment upon tamoxifen-induced activation of Cre-recombinase (Tie2ΔE9). Successful deletion of Tie2 exon 9 in kidney, lung, heart, aorta, and liver, was accompanied by a heterogeneous, organ-dependent reduction in Tie2 mRNA and protein expression. Microvascular compartment-specific reduction in Tie2 mRNA and protein occurred in arterioles of all studied organs, in renal glomeruli, and in lung capillaries. In kidney, lung, and heart, reduced Tie2 expression was accompanied by a reduction in Tie1 mRNA expression. The heterogeneous, organ- and microvascular compartment-dependent knockout pattern of Tie2 in the Tie2floxed/floxed;end-SCL-Cre-ERT mouse model suggests that future studies using similar knockout strategies should include a meticulous analysis of the knockout extent of the gene of interest, prior to studying its role in pathological conditions, so that proper conclusions can be drawn.

Two-phase sample selection strategies for design and analysis in post-genome-wide association fine-mapping studies.

Post-GWAS analysis, in many cases, focuses on fine-mapping targeted genetic regions discovered at GWAS-stage; that is, the aim is to pinpoint potential causal variants and susceptibility genes for complex traits and disease outcomes using next-generation sequencing (NGS) technologies. Large-scale GWAS cohorts are necessary to identify target regions given the typically modest genetic effect sizes. In this context, two-phase sampling design and analysis is a cost-reduction technique that utilizes data collected during phase 1 GWAS to select an informative subsample for phase 2 sequencing. The main goal is to make inference for genetic variants measured via NGS by efficiently combining data from phases 1 and 2. We propose two approaches for selecting a phase 2 design under a budget constraint. The first method identifies sampling fractions that select a phase 2 design yielding an asymptotic variance covariance matrix with certain optimal characteristics, for example, smallest trace, via Lagrange multipliers (LM). The second relies on a genetic algorithm (GA) with a defined fitness function to identify exactly a phase 2 subsample. We perform comprehensive simulation studies to evaluate the empirical properties of the proposed designs for a genetic association study of a quantitative trait. We compare our methods against two ranked designs: residual-dependent sampling and a recently identified optimal design. Our findings demonstrate that the proposed designs, GA in particular, can render competitive power in combined phase 1 and 2 analysis compared with alternative designs while preserving type 1 error control. These results are especially evident under the more practical scenario where design values need to be defined a priori and are subject to misspecification. We illustrate the proposed methods in a study of triglyceride levels in the North Finland Birth Cohort of 1966. R code to reproduce our results is available at github.com/egosv/TwoPhase_postGWAS.

The X factor: A robust and powerful approach to X-chromosome-inclusive whole-genome association studies.

The X-chromosome is often excluded from genome-wide association studies because of analytical challenges. Some of the problems, such as the random, skewed, or no X-inactivation model uncertainty, have been investigated. Other considerations have received little to no attention, such as the value in considering nonadditive and gene-sex interaction effects, and the inferential consequence of choosing different baseline alleles (i.e., the reference vs. the alternative allele). Here we propose a unified and flexible regression-based association test for X-chromosomal variants. We provide theoretical justifications for its robustness in the presence of various model uncertainties, as well as for its improved power when compared with the existing approaches under certain scenarios. For completeness, we also revisit the autosomes and show that the proposed framework leads to a more robust approach than the standard method. Finally, we provide supporting evidence by revisiting several published association studies. Supporting Information for this article are available online.

Primary myxoid and epithelioid mesenchymal tumor of the kidney with a novel GLI1-FOXO4 fusion.

To our knowledge, we describe the first mesenchymal tumor with a novel GLI1-FOXO4 fusion gene. This well-circumscribed kidney tumor displayed variably myxoid and epithelioid histologic features with a focally nodular growth pattern. The tumor cells showed bland, round to ovoid nuclei, with no overt high-grade features. The tumor showed focal immunopositivity for smooth muscle actin and Melan-A, which raised the possibility of a relationship with a perivascular epithelioid cell tumor. The clinical and morphologic features appear distinct from other reported neoplasms harboring GLI1 or FOXO4 gene rearrangements. The patient underwent radical nephrectomy and is without evidence of disease during a relatively short clinical follow-up period. However, the features of this tumor likely warrant long-term follow-up to monitor for the possibility of a late recurrence or metastasis. In addition to reporting this novel fusion-positive tumor, we also provide a brief review of GLI1 and FOXO4 gene functions in both normal and neoplastic contexts.

Molecular mechanisms of psychiatric diseases.

For most psychiatric diseases, pathogenetic concepts as well as paradigms underlying neuropsychopharmacologic approaches currently revolve around neurotransmitters such as dopamine, serotonin, and norepinephrine. However, despite the fact that several generations of neurotransmitter-based psychotropics including atypical antipsychotics, selective serotonin reuptake inhibitors, and serotonin-norepinephrine reuptake inhibitors are available, the effectiveness of these medications is limited, and relapse rates in psychiatric diseases are relatively high, indicating potential involvement of other pathogenetic pathways. Indeed, recent high-throughput studies in genetics and molecular biology have shown that pathogenesis of major psychiatric illnesses involves hundreds of genes and numerous pathways via such fundamental processes as DNA methylation, transcription, and splicing. Current review summarizes these and other molecular mechanisms of such psychiatric illnesses as schizophrenia, major depressive disorder, and alcohol use disorder and suggests a conceptual framework for future studies.

The Role of PTEN in Neurodevelopment.

PTEN is a lipid and protein phosphatase that regulates cell growth and survival. Mutations to PTEN are highly penetrant for autism spectrum disorder (ASD). Here, we briefly review the evidence linking PTEN mutations to ASD and the mouse models that have been used to study the role of PTEN in neurodevelopment. We then focus on the cellular phenotypes associated with PTEN loss in neurons, highlighting the role PTEN plays in neuronal proliferation, migration, survival, morphology, and plasticity.

EphB1 interaction with caveolin-1 in endothelial cells modulates caveolae biogenesis.

Caveolae, the cave-like structures abundant in endothelial cells (ECs), are important for multiple signaling processes such as production of nitric oxide and caveolae-mediated intracellular trafficking. Using superresolution microscopy, fluorescence resonance energy transfer, and biochemical analysis, we observed that the EphB1 receptor tyrosine kinase constitutively interacts with caveolin-1 (Cav-1), the key structural protein of caveolae. Activation of EphB1 with its ligand Ephrin B1 induced EphB1 phosphorylation and the uncoupling EphB1 from Cav-1 and thereby promoted phosphorylation of Cav-1 by Src. Deletion of Cav-1 scaffold domain binding (CSD) motif in EphB1 prevented EphB1 binding to Cav-1 as well as Src-dependent Cav-1 phosphorylation, indicating the importance of CSD in the interaction. We also observed that Cav-1 protein expression and caveolae numbers were markedly reduced in ECs from EphB1-deficient (EphB1-/-) mice. The loss of EphB1 binding to Cav-1 promoted Cav-1 ubiquitination and degradation, and hence the loss of Cav-1 was responsible for reducing the caveolae numbers. These studies identify the crucial role of EphB1/Cav-1 interaction in the biogenesis of caveolae and in coordinating the signaling function of Cav-1 in ECs.

The relationship between neurocognitive decline and the heart-lung machine.

Surgery involving the use of cardiopulmonary bypass (CPB) has long been associated with cerebral changes and may also contribute to adverse neurocognitive outcomes. However, there is a debate as to whether bypass itself is responsible for these changes. We conducted a systematic literature review on PubMed, supplementing our work with recent articles from other sources to examine the current evidence on neurocognitive decline associated with CPB. While surgeries involving CPB appear to be associated with cerebral changes and potentially with neurocognitive decline, it is unclear as to whether decline is related to the procedure itself. It is possible that the impacts of CPB can be more readily observed among individuals with preoperative cognitive impairment. It is thus important to screen for subtle and more apparent preoperative cognitive impairment as a risk factor for adverse outcomes. Further research, comparing on-pump and off-pump cohorts and involving intensive screening of preoperative cognitive decline, is indicated to elucidate the true neurocognitive consequences of the heart-lung machine.

Bayesian model averaging for the X-chromosome inactivation dilemma in genetic association study.

X-chromosome is often excluded from the so called "whole-genome" association studies due to the differences it exhibits between males and females. One particular analytical challenge is the unknown status of X-inactivation, where one of the two X-chromosome variants in females may be randomly selected to be silenced. In the absence of biological evidence in favor of one specific model, we consider a Bayesian model averaging framework that offers a principled way to account for the inherent model uncertainty, providing model averaging-based posterior density intervals and Bayes factors. We examine the inferential properties of the proposed methods via extensive simulation studies, and we apply the methods to a genetic association study of an intestinal disease occurring in about 20% of cystic fibrosis patients. Compared with the results previously reported assuming the presence of inactivation, we show that the proposed Bayesian methods provide more feature-rich quantities that are useful in practice.

Lymph node conduits transport virions for rapid T cell activation.

Despite intense interest in antiviral T cell priming, the routes by which virions move in lymph nodes (LNs) are imperfectly understood. Current models fail to explain how virus-infected cells rapidly appear within the LN interior after viral infection. To better understand virion trafficking in the LN, we determined the locations of virions and infected cells after administration to mice of vaccinia virus or Zika virus. Notably, many rapidly infected cells in the LN interior were adjacent to LN conduits. Through the use of confocal and electron microscopy, we clearly visualized virions within conduits. Functionally, CD8+ T cells rapidly and preferentially associated with vaccinia virus-infected cells in the LN paracortex, which led to T cell activation in the LN interior. These results reveal that it is possible for even large virions to flow through LN conduits and infect dendritic cells within the T cell zone to prime CD8+ T cells.

The endoscopic retromuscular repair of ventral hernia: the eTEP technique and early results.

PURPOSE: The aim of this article is to describe the technique and early follow-up results of abdominal wall reconstruction (AWR) by minimally invasive surgery (MIS); it concerns the already described endoscopic (retromuscular) Rives procedure (e-Rives) and posterior component separation with transversus abdominis release (TAR) by endoscopic approach (eTEP-TAR). METHOD: This is a prospective study which consists of 60 patients operated on between May 2016 and December 2017 by a single surgeon and monitored until July 2018. This is a heterogenic cohort with different hernia types (lateral, median, combined) which were also treated with different meshes. This material includes physiological and biomechanical issues related to the abdominal wall, the key stages of the operation including port placement strategy. RESULTS: The group of patients are 55% male, having a mean age of 53.3 years old, mean BMI of 29.3 and median ASA score of 1.83. The majority of the hernia types is represented by incisional hernia (61.7%) located especially on the median side of the abdomen (80%); more than half of them (60%) are reducible. There were 6 (10%) intraoperative complications that lead to four conversions to open or traditional laparoscopic techniques. Postoperative re-admission-two cases: one case with small bowel obstruction, solved by laparoscopic surgery and one case with hemorrhagic gastritis because of non-steroidal anti-inflammatory treatment that required only medical treatment. Quality of life (assessed on a 0-10 scale) evaluating the postoperative pain, normal activity and aesthetics, shows a significant improvement after 2 weeks and 3 months postoperatively compared to the preoperative level. 93.3% of the patients have been monitored and no recurrences after a mean of 15 months have been reported. CONCLUSION: A thorough understanding of the anatomy and surgical technique is mandatory. The eTEP approach is a feasible and safe option in MIS ventral hernia repair.

Phorbol esters induce PLVAP expression via VEGF and additional secreted molecules in MEK1-dependent and p38, JNK and PI3K/Akt-independent manner.

Endothelial diaphragms are subcellular structures critical for mammalian survival with poorly understood biogenesis. Plasmalemma vesicle associated protein (PLVAP) is the only known diaphragm component and is necessary for diaphragm formation. Very little is known about PLVAP regulation. Phorbol esters (PMA) are known to induce de novo PLVAP expression and diaphragm formation. We show that this induction relies on the de novo production of soluble factors that will act in an autocrine manner to induce PLVAP transcription and protein expression. We identified vascular endothelial growth factor-A (VEGF-A) signalling through VEGFR2 as a necessary but not sufficient downstream event as VEGF-A inhibition with antibodies and siRNA or pharmacological inhibition of VEGFR2 only partially inhibit PLVAP upregulation. In terms of downstream pathways, inhibition of MEK1/Erk1/2 MAP kinase blocked PLVAP upregulation, whereas inhibition of p38 and JNK MAP kinases or PI3K and Akt had no effect on PMA-induced PLVAP expression. In conclusion, we show that VEGF-A along with other secreted proteins act synergistically to up-regulate PLVAP in MEK1/Erk1/2 dependent manner, bringing us one step further into understanding the genesis of the essential structures that are endothelial diaphragms.

Spatially controlled assembly of affinity ligand and enzyme cargo enables targeting ferritin nanocarriers to caveolae.

One of the goals of nanomedicine is targeted delivery of therapeutic enzymes to the sub-cellular compartments where their action is needed. Endothelial caveolae-derived endosomes represent an important yet challenging destination for targeting, in part due to smaller size of the entry aperture of caveolae (ca. 30-50 nm). Here, we designed modular, multi-molecular, ferritin-based nanocarriers with uniform size (20 nm diameter) for easy drug-loading and targeted delivery of enzymatic cargo to these specific vesicles. These nanocarriers targeted to caveolar Plasmalemmal Vesicle-Associated Protein (Plvap) deliver superoxide dismutase (SOD) into endosomes in endothelial cells, the specific site of influx of superoxide mediating by such pro-inflammatory signaling as some cytokines and lipopolysaccharide (LPS). Cell studies showed efficient internalization of Plvap-targeted SOD-loaded nanocarriers followed by dissociation from caveolin-containing vesicles and intracellular transport to endosomes. The nanocarriers had a profound protective anti-inflammatory effect in an animal model of LPS-induced inflammation, in agreement with the characteristics of their endothelial uptake and intracellular transport, indicating that these novel, targeted nanocarriers provide an advantageous platform for caveolae-dependent delivery of biotherapeutics.

Flexible Nanoparticles Reach Sterically Obscured Endothelial Targets Inaccessible to Rigid Nanoparticles.

Molecular targeting of nanoparticle drug carriers promises maximized therapeutic impact to sites of disease or injury with minimized systemic effects. Precise targeting demands addressing to subcellular features. Caveolae, invaginations in cell membranes implicated in transcytosis and inflammatory signaling, are appealing subcellular targets. Caveolar geometry has been reported to impose a ≈50 nm size cutoff on nanocarrier access to plasmalemma vesicle associated protein (PLVAP), a marker found in caveolae in the lungs. The use of deformable nanocarriers to overcome that size cutoff is explored in this study. Lysozyme-dextran nanogels (NGs) are synthesized with ≈150 or ≈300 nm mean diameter. Atomic force microscopy indicates the NGs deform on complementary surfaces. Quartz crystal microbalance data indicate that NGs form softer monolayers (≈60 kPa) than polystyrene particles (≈8 MPa). NGs deform during flow through microfluidic channels, and modeling of NG extrusion through porous filters yields sieving diameters less than 25 nm for NGs with 150 and 300 nm hydrodynamic diameters. NGs of 150 and 300 nm diameter target PLVAP in mouse lungs while counterpart rigid polystyrene particles do not. The data in this study indicate a role for mechanical deformability in targeting large high-payload drug-delivery vehicles to sterically obscured targets like PLVAP.

Targeting superoxide dismutase to endothelial caveolae profoundly alleviates inflammation caused by endotoxin.

Inflammatory mediators binding to Toll-Like receptors (TLR) induce an influx of superoxide anion in the ensuing endosomes. In endothelial cells, endosomal surplus of superoxide causes pro-inflammatory activation and TLR4 agonists act preferentially via caveolae-derived endosomes. To test the hypothesis that SOD delivery to caveolae may specifically inhibit this pathological pathway, we conjugated SOD with antibodies (Ab/SOD, size ~10nm) to plasmalemmal vesicle-associated protein (Plvap) that is specifically localized to endothelial caveolae in vivo and compared its effects to non-caveolar target CD31/PECAM-1. Plvap Ab/SOD bound to endothelial cells in culture with much lower efficacy than CD31 Ab/SOD, yet blocked the effects of LPS signaling with higher efficiency than CD31 Ab/SOD. Disruption of cholesterol-rich membrane domains by filipin inhibits Plvap Ab/SOD endocytosis and LPS signaling, implicating the caveolae-dependent pathway(s) in both processes. Both Ab/SOD conjugates targeted to Plvap and CD31 accumulated in the lungs after IV injection in mice, but the former more profoundly inhibited LPS-induced pulmonary inflammation and elevation of plasma level of interferon-beta and -gamma and interleukin-27. Taken together, these results indicate that targeted delivery of SOD to specific cellular compartments may offer effective, mechanistically precise interception of pro-inflammatory signaling mediated by reactive oxygen species.

Growth Differentiation Factor 6 Promotes Vascular Stability by Restraining Vascular Endothelial Growth Factor Signaling.

OBJECTIVE: The assembly of a functional vascular system requires a coordinated and dynamic transition from activation to maturation. High vascular endothelial growth factor activity promotes activation, including junction destabilization and cell motility. Maturation involves junctional stabilization and formation of a functional endothelial barrier. The identity and mechanism of action of prostabilization signals are still mostly unknown. Bone morphogenetic protein receptors and their ligands have important functions during embryonic vessel assembly and maturation. Previous work has suggested a role for growth differentiation factor 6 (GDF6; bone morphogenetic protein 13) in vascular integrity although GDF6's mechanism of action was not clear. Therefore, we sought to further explore the requirement for GDF6 in vascular stabilization. APPROACH AND RESULTS: We investigated the role of GDF6 in promoting endothelial vascular integrity in vivo in zebrafish and in cultured human umbilical vein endothelial cells in vitro. We report that GDF6 promotes vascular integrity by counteracting vascular endothelial growth factor activity. GDF6-deficient endothelium has increased vascular endothelial growth factor signaling, increased vascular endothelial-cadherin Y658 phosphorylation, vascular endothelial-cadherin delocalization from cell-cell interfaces, and weakened endothelial cell adherence junctions that become prone to vascular leak. CONCLUSIONS: Our results suggest that GDF6 promotes vascular stabilization by restraining vascular endothelial growth factor signaling. Understanding how GDF6 affects vascular integrity may help to provide insights into hemorrhage and associated vascular pathologies in humans.

Ascending Vasa Recta Are Angiopoietin/Tie2-Dependent Lymphatic-Like Vessels.

Urinary concentrating ability is central to mammalian water balance and depends on a medullary osmotic gradient generated by a countercurrent multiplication mechanism. Medullary hyperosmolarity is protected from washout by countercurrent exchange and efficient removal of interstitial fluid resorbed from the loop of Henle and collecting ducts. In most tissues, lymphatic vessels drain excess interstitial fluid back to the venous circulation. However, the renal medulla is devoid of classic lymphatics. Studies have suggested that the fenestrated ascending vasa recta (AVRs) drain the interstitial fluid in this location, but this function has not been conclusively shown. We report that late gestational deletion of the angiopoietin receptor endothelial tyrosine kinase 2 (Tie2) or both angiopoietin-1 and angiopoietin-2 prevents AVR formation in mice. The absence of AVR associated with rapid accumulation of fluid and cysts in the medullary interstitium, loss of medullary vascular bundles, and decreased urine concentrating ability. In transgenic reporter mice with normal angiopoietin-Tie2 signaling, medullary AVR exhibited an unusual hybrid endothelial phenotype, expressing lymphatic markers (prospero homeobox protein 1 and vascular endothelial growth factor receptor 3) as well as blood endothelial markers (CD34, endomucin, platelet endothelial cell adhesion molecule 1, and plasmalemmal vesicle-associated protein). Taken together, our data redefine the AVRs as Tie2 signaling-dependent specialized hybrid vessels and provide genetic evidence of the critical role of AVR in the countercurrent exchange mechanism and the structural integrity of the renal medulla.

Two-phase designs for joint quantitative-trait-dependent and genotype-dependent sampling in post-GWAS regional sequencing.

We evaluate two-phase designs to follow-up findings from genome-wide association study (GWAS) when the cost of regional sequencing in the entire cohort is prohibitive. We develop novel expectation-maximization-based inference under a semiparametric maximum likelihood formulation tailored for post-GWAS inference. A GWAS-SNP (where SNP is single nucleotide polymorphism) serves as a surrogate covariate in inferring association between a sequence variant and a normally distributed quantitative trait (QT). We assess test validity and quantify efficiency and power of joint QT-SNP-dependent sampling and analysis under alternative sample allocations by simulations. Joint allocation balanced on SNP genotype and extreme-QT strata yields significant power improvements compared to marginal QT- or SNP-based allocations. We illustrate the proposed method and evaluate the sensitivity of sample allocation to sampling variation using data from a sequencing study of systolic blood pressure.