An antiangiogenic neurokinin-B/thromboxane A2 regulatory axis

Establishment of angiogenic circuits that orchestrate blood vessel development and remodeling requires an exquisite balance between the activities of pro- and antiangiogenic factors. However, the logic that permits complex signal integration by vascular endothelium is poorly understood. We demonstrate that a “neuropeptide,” neurokinin-B (NK-B), reversibly inhibits endothelial cell vascular network assembly and opposes angiogenesis in the chicken chorioallantoic membrane. Disruption of endogenous NK-B signaling promoted angiogenesis. Mechanistic analyses defined a multicomponent pathway in which NK-B signaling converges upon cellular processes essential for angiogenesis. NK-B−mediated ablation of Ca2+ oscillations and elevation of 3′–5′ cyclic adenosine monophosphate (cAMP) reduced cellular proliferation, migration, and vascular endothelial growth factor receptor expression and induced the antiangiogenic protein calreticulin. Whereas NK-B initiated certain responses, other activities required additional stimuli that increase cAMP. Although NK-B is a neurotransmitter/ neuromodulator and NK-B overexpression characterizes the pregnancy-associated disorder preeclampsia, NK-B had not been linked to vascular remodeling. These results establish a conserved mechanism in which NK-B instigates multiple activities that collectively oppose vascular remodeling

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Molecular Hallmarks of Endogenous Chromatin Complexes Containing Master Regulators of Hematopoiesis▿ †

Combinatorial interactions among trans-acting factors establish transcriptional circuits that orchestrate cellular differentiation, survival, and development. Unlike circuits instigated by individual factors, efforts to identify gene ensembles controlled by multiple factors simultaneously are in their infancy. A paradigm has emerged in which the important regulators of hematopoiesis GATA-1 and GATA-2 function combinatorially with Scl/TAL1, another key regulator of hematopoiesis. The underlying mechanism appears to involve preferential assembly of a multimeric complex on a composite DNA element containing WGATAR and E-box motifs. Based on this paradigm, one would predict that GATA-2 and Scl/TAL1 would commonly co-occupy such composite elements in cells. However, chromosome-wide analyses indicated that the vast majority of conserved composite elements were occupied by neither GATA-2 nor Scl/TAL1. Intriguingly, the highly restricted set of GATA-2-occupied composite elements had characteristic molecular hallmarks, specifically Scl/TAL1 occupancy, a specific epigenetic signature, specific neighboring cis elements, and preferential enhancer activity in GATA-2-expressing cells. Genes near the GATA-2-Scl/TAL1-occupied composite elements were regulated by GATA-2 or GATA-1, and therefore these fundamental studies on combinatorial transcriptional mechanisms were also leveraged to discover novel GATA factor-mediated cell regulatory pathways

Friend of GATA-1–independent transcriptional repression: a novel mode of GATA-1 function

The GATA-1–interacting protein Friend Of GATA-1 (FOG-1) is essential for the proper transcriptional activation and repression of numerous GATA-1 target genes. Although FOG-1–independent activation by GATA-1 has been described, all known examples of GATA-1–mediated repression are FOG-1 dependent. In the GATA-1–null G1E cell line, estrogen receptor ligand binding domain (ER) chimeras of either wild-type GATA-1 or a FOG-1–binding defective mutant of GATA-1 repressed several genes similarly upon activation with β-estradiol. Repression also occurred in a FOG-1–null cell line expressing ER–GATA-1 and during ex vivo erythropoiesis. At the Lyl1 and Rgs18 loci, we found highly restricted occupancy by GATA-1 and GATA-2, indicating that these genes are direct targets of GATA factor regulation. The identification of genes repressed by GATA-1 independent of FOG-1 defines a novel mode of GATA-1–mediated transcriptional regulation

Relocalizing Genetic Loci into Specific Subnuclear Neighborhoods*

A poorly understood problem in genetics is how the three-dimensional organization of the nucleus contributes to establishment and maintenance of transcriptional networks. Genetic loci can reside in chromosome “territories” and undergo dynamic changes in subnuclear positioning. Such changes appear to be important for regulating transcription, although many questions remain regarding how loci reversibly transit in and out of their territories and the functional significance of subnuclear transitions. We addressed this issue using GATA-1, a master regulator of hematopoiesis implicated in human leukemogenesis, which often functions with the coregulator Friend of GATA-1 (FOG-1). In a genetic complementation assay in GATA-1-null cells, GATA-1 expels FOG-1-dependent target genes from the nuclear periphery during erythroid maturation, but the underlying mechanisms are unknown. We demonstrate that GATA-1 induces extrusion of the β-globin locus away from its chromosome territory at the nuclear periphery, and extrusion precedes the maturation-associated transcriptional surge and morphological transition. FOG-1 and its interactor Mi-2β, a chromatin remodeling factor commonly linked to repression, were required for locus extrusion. Erythroid Krüppel-like factor, a pivotal regulator of erythropoiesis that often co-occupies chromatin with GATA-1, also promoted locus extrusion. Disruption of transcriptional maintenance did not restore the locus subnuclear position that preceded activation. These results lead to a model for how a master developmental regulator relocalizes a locus into a new subnuclear neighborhood that is permissive for high level transcription as an early step in establishing a cell type-specific genetic network. Alterations in the regulatory milieu can abrogate maintenance without reversion of locus residency back to its original neighborhood