Myoblasts and macrophages share molecular components that contribute to cell–cell fusion

Cell–cell fusion is critical to the normal development of certain tissues, yet the nature and degree of conservation of the underlying molecular components remains largely unknown. Here we show that the two guanine-nucleotide exchange factors Brag2 and Dock180 have evolutionarily conserved functions in the fusion of mammalian myoblasts. Their effects on muscle cell formation are distinct and are a result of the activation of the GTPases ARF6 and Rac, respectively. Inhibition of ARF6 activity results in a lack of physical association between paxillin and β1-integrin, and disruption of paxillin transport to sites of focal adhesion. We show that fusion machinery is conserved among distinct cell types because Dock180 deficiency prevented fusion of macrophages and the formation of multinucleated giant cells. Our results are the first to demonstrate a role for a single protein in the fusion of two different cell types, and provide novel mechanistic insight into the function of GEFs in the morphological maturation of multinucleated cells

Optimal Brain MRI Protocol for New Neurological Complaint

Background/Purpose Patients with neurologic complaints are imaged with MRI protocols that may include many pulse sequences. It has not been documented which sequences are essential. We assessed the diagnostic accuracy of a limited number of sequences in patients with new neurologic complaints. Methods: 996 consecutive brain MRI studies from patients with new neurological complaints were divided into 2 groups. In group 1, reviewers used a 3-sequence set that included sagittal T1-weighted, axial T2-weighted fluid-attenuated inversion recovery, and axial diffusion-weighted images. Subsequently, another group of studies were reviewed using axial susceptibility-weighted images in addition to the 3 sequences. The reference standard was the study's official report. Discrepancies between the limited sequence review and the reference standard including Level I findings (that may require immediate change in patient management) were identified. Results: There were 84 major findings in 497 studies in group 1 with 21 not identified in the limited sequence evaluations: 12 enhancing lesions and 3 vascular abnormalities identified on MR angiography. The 3-sequence set did not reveal microhemorrhagic foci in 15 of 19 studies. There were 117 major findings in 499 studies in group 2 with 19 not identified on the 4-sequence set: 17 enhancing lesions and 2 vascular lesions identified on angiography. All 87 Level I findings were identified using limited sequence (56 acute infarcts, 16 hemorrhages, and 15 mass lesions). Conclusion: A 4-pulse sequence brain MRI study is sufficient to evaluate patients with a new neurological complaint except when contrast or angiography is indicated

Cytoplasmic p53 couples oncogene-driven glucose metabolism to apoptosis and is a therapeutic target in glioblastoma.

Cross-talk among oncogenic signaling and metabolic pathways may create opportunities for new therapeutic strategies in cancer. Here we show that although acute inhibition of EGFR-driven glucose metabolism induces only minimal cell death, it lowers the apoptotic threshold in a subset of patient-derived glioblastoma (GBM) cells. Mechanistic studies revealed that after attenuated glucose consumption, Bcl-xL blocks cytoplasmic p53 from triggering intrinsic apoptosis. Consequently, targeting of EGFR-driven glucose metabolism in combination with pharmacological stabilization of p53 with the brain-penetrant small molecule idasanutlin resulted in synthetic lethality in orthotopic glioblastoma xenograft models. Notably, neither the degree of EGFR-signaling inhibition nor genetic analysis of EGFR was sufficient to predict sensitivity to this therapeutic combination. However, detection of rapid inhibitory effects on [18F]fluorodeoxyglucose uptake, assessed through noninvasive positron emission tomography, was an effective predictive biomarker of response in vivo. Together, these studies identify a crucial link among oncogene signaling, glucose metabolism, and cytoplasmic p53, which may potentially be exploited for combination therapy in GBM and possibly other malignancies

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Regenerative strategies for craniofacial disorders

Craniofacial disorders present markedly complicated problems in reconstruction because of the complex interactions of the multiple, simultaneously affected tissues. Regenerative medicine holds promise for new strategies to improve treatment of these disorders. This review addresses current areas of unmet need in craniofacial reconstruction and emphasizes how craniofacial tissues differ from their analogs elsewhere in the body. We present a problem-based approach to illustrate current treatment strategies for various craniofacial disorders, to highlight areas of need, and to suggest regenerative strategies for craniofacial bone, fat, muscle, nerve, and skin. For some tissues, current approaches offer excellent reconstructive solutions using autologous tissue or prosthetic materials. Thus, new regenerative approaches would need to offer major advantages in order to be adopted. In other tissues, the unmet need is great, and we suggest the greatest regenerative need is for muscle, skin, and nerve. The advent of composite facial tissue transplantation and the development of regenerative medicine are each likely to add important new paradigms to our treatment of craniofacial disorders

Human ARF Specifically Inhibits Epimorphic Regeneration in the Zebrafish Heart

The Alternative Reading Frame (ARF) protein is a tumor suppressor encoded by the Cyclin Dependent Kinase Inhibitor 2A gene in mammals but not lower regenerative vertebrates, and has been previously implicated as a context-sensitive suppressor of regeneration in murine skeletal muscle and humanized ARF-expressing zebrafish fins. This study extends our investigation of the role of ARF in the regeneration of other solid tissues, including the zebrafish heart and the mammalian digit. Heart regeneration after cryoinjury was used to mimic massive myocardial infarction. ARF gene expression was upregulated during the cardiac regenerative process and slowed the rate of morphological recovery. ARF specifically impacts cardiomyocytes, neovascularization, and the endothelial-mesenchymal transition, while not affecting epicardial proliferation. This suggests that in the context of regeneration, ARF is specifically expressed in cells undergoing dedifferentiation. To investigate ARF as a suppressor of epimorphic regeneration in mammalian systems, we also tested whether the absence of ARF was permissive for murine digit regeneration, but found that ARF absence alone was insufficient to significantly alter digit restoration. These findings provide additional evidence that ARF suppresses epimorphic regeneration, but suggests that modulation of ARF alone is insufficient to permit regeneration

Reprogramming to a muscle fate by fusion recapitulates differentiation

Fusion of mammalian cells to form stable, non-dividing heterokaryons results in nuclear reprogramming without the exchange of genetic material. In this report, we show that reprogramming in somatic cell heterokaryons involves activation of the canonical skeletal muscle transcription factors as well as contraction-excitation genes. Thus, the effect of heterokaryon formation on gene expression is to induce a recapitulation of differentiation. Heterokaryons formed with a relatively refractory cell type, the hepatocyte cell line HepG2, revealed the importance of both MyoD expression and other unidentified cytoplasmic components, neither of which are sufficient for efficient muscle gene activation, but are synergistic. We provide evidence that de-repression by transient histone deacetylase inhibition can induce MyoD expression and increase the extent and efficiency of muscle gene transcription. Taken together, the results suggest that understanding the mechanistic basis, using a combination of approaches, and taking into account cell history, will facilitate an increase in the efficiency and fidelity of conversion from one differentiated phenotype to another desired cell type. Inherent advantages of the heterokaryon system merit further investigation in the pursuit of directed cloning

Myoblasts and macrophages share molecular components that contribute to cell-cell fusion.

Cell-cell fusion is critical to the normal development of certain tissues, yet the nature and degree of conservation of the underlying molecular components remains largely unknown. Here we show that the two guanine-nucleotide exchange factors Brag2 and Dock180 have evolutionarily conserved functions in the fusion of mammalian myoblasts. Their effects on muscle cell formation are distinct and are a result of the activation of the GTPases ARF6 and Rac, respectively. Inhibition of ARF6 activity results in a lack of physical association between paxillin and beta(1)-integrin, and disruption of paxillin transport to sites of focal adhesion. We show that fusion machinery is conserved among distinct cell types because Dock180 deficiency prevented fusion of macrophages and the formation of multinucleated giant cells. Our results are the first to demonstrate a role for a single protein in the fusion of two different cell types, and provide novel mechanistic insight into the function of GEFs in the morphological maturation of multinucleated cells