Visual experience is not necessary for the development of face-selectivity in the lateral fusiform gyrus

The fusiform face area responds selectively to faces and is causally involved in face perception. How does face-selectivity in the fusiform arise in development, and why does it develop so systematically in the same location across individuals? Preferential cortical responses to faces develop early in infancy, yet evidence is conflicting on the central question of whether visual experience with faces is necessary. Here, we revisit this question by scanning congenitally blind individuals with fMRI while they haptically explored 3D-printed faces and other stimuli. We found robust face-selective responses in the lateral fusiform gyrus of individual blind participants during haptic exploration of stimuli, indicating that neither visual experience with faces nor fovea-biased inputs is necessary for face-selectivity to arise in the lateral fusiform gyrus. Our results instead suggest a role for long-range connectivity in specifying the location of face-selectivity in the human brain.

A role of stochastic phenotype switching in generating mosaic endothelial cell heterogeneity

Previous studies have shown that biological noise may drive dynamic phenotypic mosaicism in isogenic unicellular organisms. However, there is no evidence for a similar mechanism operating in metazoans. Here we show that the endothelial-restricted gene, von Willebrand factor (VWF), is expressed in a mosaic pattern in the capillaries of many vascular beds and in the aorta. In capillaries, the mosaicism is dynamically regulated, with VWF switching between ON and OFF states during the lifetime of the animal. Clonal analysis of cultured endothelial cells reveals that dynamic mosaic heterogeneity is controlled by a low-barrier, noise-sensitive bistable switch that involves random transitions in the DNA methylation status of the VWF promoter. Finally, the hearts of VWF-null mice demonstrate an abnormal endothelial phenotype as well as cardiac dysfunction. Together, these findings suggest a novel stochastic phenotype switching strategy for adaptive homoeostasis in the adult vasculature.

Abstract 44: Organ-specific Stochastic Phenotype Switching is Required for Endothelial Health

Among unicellular organisms, stochastic phenotype switching is a documented strategy for survival. These populations "hedge their bets": while the majority of their cells are adapted to their present environment, a minority remains poised to thrive under drastically different conditions. Bet hedging has also been described in metazoan cells, primarily in vitro. However, its role in tissue homeostasis has yet to be established. Here, we show that von Willebrand factor (vWF) is expressed in a spatially heterogeneous manner in a small fraction of capillary endothelial cells in the heart, skeletal muscle, lung and brain. Moreover, these mosaic patterns are dynamic, in that vWF expression stochastically toggles ON/OFF over time. By contrast, expression of vWF in the aorta and liver is static in time. In cultured primary endothelial cells, biological noise resulted in mosaic vWF heterogeneity through a promoter-level DNA methylation switch. Finally, vWF-/- mice demonstrated extensive endothelial cell damage in capillaries of the heart and impaired cardiac function, but not kidney or aorta. Taken together, these findings suggest that dynamic mosaicism of vWF expression is functionally relevant and that bet hedging represents a previously unrecognized strategy for adaptive, organ-specific homeostasis.

PGC-1α induces SPP1 to activate macrophages and orchestrate functional angiogenesis in skeletal muscle

RATIONALE

Mechanisms of angiogenesis in skeletal muscle remain poorly understood. Efforts to induce physiological angiogenesis hold promise for the treatment of diabetic microvascular disease and peripheral artery disease but are hindered by the complexity of physiological angiogenesis and by the poor angiogenic response of aged and patients with diabetes mellitus. To date, the best therapy for diabetic vascular disease remains exercise, often a challenging option for patients with leg pain. Peroxisome proliferation activator receptor-γ coactivator-1α (PGC-1α), a powerful regulator of metabolism, mediates exercise-induced angiogenesis in skeletal muscle.

OBJECTIVE

To test whether, and how, PGC-1α can induce functional angiogenesis in adult skeletal muscle.

METHODS AND RESULTS

Here, we show that muscle PGC-1α robustly induces functional angiogenesis in adult, aged, and diabetic mice. The process involves the orchestration of numerous cell types and leads to patent, nonleaky, properly organized, and functional nascent vessels. These findings contrast sharply with the disorganized vasculature elicited by induction of vascular endothelial growth factor alone. Bioinformatic analyses revealed that PGC-1α induces the secretion of secreted phosphoprotein 1 and the recruitment of macrophages. Secreted phosphoprotein 1 stimulates macrophages to secrete monocyte chemoattractant protein-1, which then activates adjacent endothelial cells, pericytes, and smooth muscle cells. In contrast, induction of PGC-1α in secreted phosphoprotein 1(-/-) mice leads to immature capillarization and blunted arteriolarization. Finally, adenoviral delivery of PGC-1α into skeletal muscle of either young or old and diabetic mice improved the recovery of blood flow in the murine hindlimb ischemia model of peripheral artery disease.

CONCLUSIONS

PGC-1α drives functional angiogenesis in skeletal muscle and likely recapitulates the complex physiological angiogenesis elicited by exercise.

FOXO1-mediated activation of Akt plays a critical role in vascular homeostasis

RATIONALE

Forkhead box-O transcription factors (FoxOs) transduce a wide range of extracellular signals, resulting in changes in cell survival, cell cycle progression, and several cell type-specific responses. FoxO1 is expressed in many cell types, including endothelial cells (ECs). Previous studies have shown that Foxo1 knockout in mice results in embryonic lethality at E11 because of impaired vascular development. In contrast, somatic deletion of Foxo1 is associated with hyperproliferation of ECs. Thus, the precise role of FoxO1 in the endothelium remains enigmatic.

OBJECTIVE

To determine the effect of endothelial-specific knockout and overexpression of FoxO1 on vascular homeostasis.

METHODS AND RESULTS

We show that EC-specific disruption of Foxo1 in mice phenocopies the full knockout. Although endothelial expression of FoxO1 rescued otherwise Foxo1-null animals, overexpression of constitutively active FoxO1 resulted in increased EC size, occlusion of capillaries, elevated peripheral resistance, heart failure, and death. Knockdown of FoxO1 in ECs resulted in marked inhibition of basal and vascular endothelial growth factor-induced Akt-mammalian target of rapamycin complex 1 (mTORC1) signaling.

CONCLUSIONS

Our findings suggest that in mice, endothelial expression of FoxO1 is both necessary and sufficient for embryonic development. Moreover, FoxO1-mediated feedback activation of Akt maintains growth factor responsive Akt/mTORC1 activity within a homeostatic range.

Abstract 195: Characterization of DNA Modules in Regulating VWF Vascular Bed--Specific Expression

Expression of von Willebrand Factor (vWF) in the endothelium is regulated by vascular bed-specific pathways. A region of the human vWF gene between -843 and -620 was previously shown to direct expression in the endothelium of capillaries and a subset of larger blood vessels in the heart and skeletal muscle. Here, our goal was to further delineate the responsible DNA sequences. A series of constructs containing 5’-deletions, internal deletions or point mutations of the vWF promoter coupled to LacZ were targeted to the Hprt locus of mice using homologous recombination, and the resulting animals were analyzed for reporter gene expression. The findings demonstrate that a three-base-pair fragment within vWF promoter is necessary for expression in capillary but not large vessel endothelium in heart and skeletal muscle. Although the sequence does not conform to established DNA binding sites, it bound to nuclear protein as determined by elecrophoretic mobility shift assay. Mass spectrometry of the DNA-protein complex revealed several potential binding transcription factors. The heart- and skeletal muscle-specific promoter region did not response to shear stress or mechanical stress. Bisulfite sequencing revealed differential methylation of the human vWF promoter in endothelial cells from expressing and non-expressing vascular beds. These differences were altered by the mutation at the short cis-element. Together, these data support a model of modular gene regulation in which distinct DNA sequences in the vWF promoter direct expression in different vascular beds.

Abstract 531: Role of Rna Splicing In Mediating Lineage-specific Expression of the Von Willebrand Factor Gene in the Endothelium

We previously demonstrated that the first intron of the human von Willebrand factor (vWF) is required for gene expression in the endothelium of transgenic mice. Based on this finding, we hypothesized that RNA splicing plays a role in mediating vWF expression in the vasculature. To address this question, we employed transient transfection assays in human endothelial cells and megakaryocytes with intron-containing and intronless human vWF promoter-luciferase constructs. Next, we generated knockin mice in which LacZ was targeted to the endogenous mouse vWF locus in the absence or presence of the native first intron or heterologous introns from the human beta-globin, mouse DSCR-1 or hagfish coagulation factor X genes. In both the in vitro assays and the knockin mice, the loss of the first intron of vWF resulted in a significant reduction of reporter gene expression in endothelial cells, but not megakaryocytes. This effect was rescued to varying degrees by the introduction of a heterologous intron. Intron-mediated enhancement of expression was mediated at a post-transcriptional level. Together, these findings implicate a role for intronic splicing in mediating lineage-specific expression of vWF in the endothelium.

Copper Sensing with a Prion Protein Modified Nanopipette

Protein-metal interactions determine and regulate many biological functions. Nanopipettes functionalized with peptide moieties can be used as sensors for metal ions in solution.

Erg is a crucial regulator of endocardial-mesenchymal transformation during cardiac valve morphogenesis

During murine embryogenesis, the Ets factor Erg is highly expressed in endothelial cells of the developing vasculature and in articular chondrocytes of developing bone. We identified seven isoforms for the mouse Erg gene. Four share a common translational start site encoded by exon 3 (Ex3) and are enriched in chondrocytes. The other three have a separate translational start site encoded by Ex4 and are enriched in endothelial cells. Homozygous Erg^ΔEx3/ΔEx3 knockout mice are viable, fertile and do not display any overt phenotype. By contrast, homozygous Erg^ΔEx4/ΔEx4 knockout mice are embryonic lethal, which is associated with a marked reduction in endocardial-mesenchymal transformation (EnMT) during cardiac valve morphogenesis. We show that Erg is required for the maintenance of the core EnMT regulatory factors that include Snail1 and Snail2 by binding to their promoter and intronic regions.

Abstract 514: Endothelial Cell-Specific Molecule 1 or Endocan Is Required for Postnatal Cardiac Function

Introduction: Endothelial specific molecule 1 (ESM1) or Endocan is an endothelial secreted dermatan sulphate proteoglycan whose function remains elusive. ESM-1 is detected at a level of approximately 1 ng/ml in the plasma of healthy individuals and is significantly elevated in diseased states like cancer and sepsis. ESM1 expression in vivo is limited while its expression is up regulated in tumor neovessels. However there have been no in vivo studies of ESM1 function to date.

Objective: The aim of this study was to understand the function of ESM1 in vivo using a global ESM1 knockout (KO) mouse model.

Methods and results: ESM1 KO mice were generated by deleting the exon 1 containing the coding region of the mouse gene. Mice were backcrossed in C57BL/6 background for more than 10 generations. Targeted deletion of ESM1 was confirmed by real time quantitative RT-PCR (qRT-PCR). Analysis of ESM1 KO embryos and yolk sac at different time points (E12.5, E15.5) showed normal vasculature compared to WT controls. ESM1 KO mice were born at the normal mendelian but they showed 50% perinatal mortality by postnatal day 3 (P3). Pathological analysis of mice that died at P2 revealed dilated atria engorged with blood and thrombi indicative of possible defect in cardiac contractility. Pulmonary congestion was also observed indicative of possible cardiac failure. Fetal genes associated with cardiac stress response including atrial natriuretic peptide (Nppa), brain natriuretic pepetide (Nppb) and beta-myosin heavy chain (Myh7) were significantly up regulated in ESM1 KO postnatal (P2) hearts compared to controls.

Conclusion: Our findings demonstrate for the first time that ESM1 is required for postnatal cardiac function. Future studies are aimed at understanding the mechanisms leading to impaired cardiac function in ESM1 KO mice.

Normal levels of anticoagulant heparan sulfate are not essential for normal hemostasis

Endothelial cell production of anticoagulant heparan sulfate (HS(act)) is controlled by the Hs3st1 gene, which encodes the rate-limiting enzyme heparan sulfate 3-O-sulfotransferase-1 (3-OST-1). In vitro, HS(act) dramatically enhances the neutralization of coagulation proteases by antithrombin. The in vivo role of HS(act) was evaluated by generating Hs3st1(-/-) knockout mice. Hs3st1(-/-) animals were devoid of 3-OST-1 enzyme activity in plasma and tissue extracts. Nulls showed dramatic reductions in tissue levels of HS(act) but maintained wild-type levels of tissue fibrin accumulation under both normoxic and hypoxic conditions. Given that vascular HS(act) predominantly occurs in the subendothelial matrix, mice were subjected to a carotid artery injury assay in which ferric chloride administration induces de-endothelialization and occlusive thrombosis. Hs3st1(-/-) and Hs3st1(+/+) mice yielded indistinguishable occlusion times and comparable levels of thrombin.antithrombin complexes. Thus, Hs3st1(-/-) mice did not show an obvious procoagulant phenotype. Instead, Hs3st1(-/-) mice exhibited genetic background-specific lethality and intrauterine growth retardation, without evidence of a gross coagulopathy. Our results demonstrate that the 3-OST-1 enzyme produces the majority of tissue HS(act). Surprisingly, this bulk of HS(act) is not essential for normal hemostasis in mice. Instead, 3-OST-1-deficient mice exhibited unanticipated phenotypes suggesting that HS(act) or additional 3-OST-1-derived structures may serve alternate biologic roles.

Fish-oil fatty acid supplementation in active rheumatoid arthritis. A double-blinded, controlled, crossover study

STUDY OBJECTIVE

to determine the efficacy of fish-oil dietary supplements in active rheumatoid arthritis and their effect on neutrophil leukotriene levels.

DESIGN

nonrandomized, double-blinded, placebo-controlled, crossover trial with 14-week treatment periods and 4-week washout periods.

SETTING

academic medical center, referral-based rheumatology clinic.

PATIENTS

forty volunteers with active, definite, or classical rheumatoid arthritis. Five patients dropped out, and two were removed for noncompliance.

INTERVENTIONS

treatment with nonsteroidal anti-inflammatory drugs, slow-acting antirheumatic drugs, and prednisone was continued. Twenty-one patients began with a daily dosage of 2.7 g of eicosapaentanic acid and 1.8 g of docosahexenoic acid given in 15 MAX-EPA capsules (R.P. Scherer, Clearwater, Florida), and 19 began with identical-appearing placebos. The background diet was unchanged.

MEASUREMENTS AND MAIN RESULTS

the following results favored fish oil placebo after 14 weeks: mean time to onset of fatigue improved by 156 minutes (95% confidence interval, 1.2 to 311.0 minutes), and number of tender joints decreased by 3.5 (95% Cl, -6.0 to -1.0). Other clinical measures favored fish oil as well but did reach statistical significance. Neutrophil leukotriene B4 production was correlated with the decrease in number of tender joints (Spearman rank correlation r=0.53; p less than 0.05). There were no statistically significant differences in hemoglobin level, sedimentation rate, or presence of rheumatoid factor or in patient-reported adverse effects. An effect from the fish oil persisted beyond the 4-week washout period.

CONCLUSIONS

fish-oil ingestion results in subjective alleviation of active rheumatoid arthritis and reduction in neutrophil leukotriene B4 production. Further studies are needed to elucidate mechanisms of action and optimal dose and duration of fish-oil supplementation.

Circular dichroism spectroscopy of heparin-antithrombin interactions

We have utilized circular dichroism spectroscopy to examine the interaction of antithrombin with heparin-derived oligosaccharides and mucopolysaccharides of various sizes. Our studies demonstrate that the various complexes exhibit two major types of chiral absorption spectra. The first of these patterns is seen when octasaccharide, decasaccharide, dodecasaccharide, or tetradecasaccharide fragments bind to the protease inhibitor. The circular dichroism spectra of these complexes when compared to the spectrum of free antithrombin show several distinguishing characteristics. On the one hand, there is a marked general increase in positive chiral absorption that is maximal at 296 and 288 nm and 290 and 282.5 nm. These observations indicate perturbation of "buried" and "exposed" tryptophan residues. On the other hand, a significant augmentation in circular dichroism that peaks at 269.5 and 263 nm is noted. These findings are probably due to the summed positive and negative contributions arising from tryptophan residue(s), disulfide bridge(s), and phenylalanine residue(s). Given that these heparin fragments are able to accelerate factor Xa-antithrombin interactions but not thrombin-antithrombin interactions, the above spectral transitions must be associated with either the binding of a critical domain of the oligosaccharides to the protease inhibitor or the "activation" of the protease inhibitor with respect to factor Xa neutralization. The second of these patterns is apparent when octadecasaccharide, low molecular weight heparin (6,500), and high molecular weight heparin (22,000) interact with antithrombin. The circular dichroism spectra of these complexes compared to the spectrum of free protease inhibitor are similar to the first pattern except for changes within the 292- to 282-nm and 275- to 255-nm regions. The subtraction of the first pattern from the second pattern reveals a shallow negative band between 300 and 275 nm with potential negative minima at 290 and 283 nm as well as a deep negative band between 275 and 255 nm with possible negative minima at 268 and 262 nm. This chiral absorption profile is most likely to arise from conformational changes of a disulfide bridge(s). However, we cannot completely exclude the possibility that the above circular dichroism difference curve might be explained on the basis of transitions originating from a tryptophan residue(s). Given our method for generating the above data, these spectral alterations must be associated with the binding of a second critical domain of the mucopolysaccharide to antithrombin that is required for rapid complex formation with thrombin or the activation of the protease inhibitor with respect to the neutralization of the latter enzyme.

Fractionation of low molecular weight heparin species and their interaction with antithrombin

Preparations of low molecular weight porcine heparin with an average specific anticoagulant activity of 94 units/mg were fractionated into "active" and "relatively inactive" forms of the mucopolysaccharide of approximately 6000 daltons each. The active fraction was further subdivided into various species with descending but significant affinities for the protease inhibitor as well as decreasing but substantial anticoagulatn potencies. "Highly active" heparin (approximately 8% of the low molecular weight pool) possesses a specific anticoagulant activity of 350 +/- 10 units/mg. The relatively inactive fraction (67% of the low molecular weight pool) exhibits a specific anticoagulant activity of 4 +/- 1 units/mg. The binding of highly active heparin to antithrombin is accurately described by a single-site binding model with a KHep-ATDISS of approximately 1 X 10(-7) M. Variations in this binding parameter secondary to changes in environmental variables indicate that charge-charge interactions as well as an increase in entropy are critical to the formation of the highly active heparin-antithrombin complex. The interaction of relatively inactive heparin with the protease inhibitor is characterized by an apparent KHep-ATDISS of 1 X 10(-4) M. In large measure, this is due to small amounts of residual active mucopolysaccharide (0.5%). The ability of the highly active heparin to accelerate the thrombin-antithrombin interaction was also examined. We were able to demonstrate that the mucopolysaccharide acts as a catalyst in this process and is able to initiate multiple rounds of enzyme-inhibitor complex formation. The rate of enzyme neutralization is increased to a maximum of 2300-fold as the concentration of heparin is raised until the inhibitor is saturated with mucopolysaccharide. Further increases in heparin concentration result in a reduction in the speed of enzyme neutralization. This appears to be due to the formation of thrombin-heparin complexes. A mathematical model is given which provides a relationship between the initial velocity of enzyme neutralization and reactant concentrations.