Deleterious variants in TRAK1 disrupt mitochondrial movement and cause fatal encephalopathy

This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record.The corrigendum to this article is in ORE: http://hdl.handle.net/10871/33588Cellular distribution and dynamics of mitochondria are regulated by several motor proteins and a microtubule network. In neurons, mitochondrial trafficking is crucial because of high energy needs and calcium ion buffering along axons to synapses during neurotransmission. The trafficking kinesin proteins (TRAKs) are well characterized for their role in lysosomal and mitochondrial trafficking in cells, especially neurons. Using whole exome sequencing, we identified homozygous truncating variants in TRAK1 (NM_001042646:c.287-2A > C), in six lethal encephalopathic patients from three unrelated families. The pathogenic variant results in aberrant splicing and significantly reduced gene expression at the RNA and protein levels. In comparison with normal cells, TRAK1-deficient fibroblasts showed irregular mitochondrial distribution, altered mitochondrial motility, reduced mitochondrial membrane potential, and diminished mitochondrial respiration. This study confirms the role of TRAK1 in mitochondrial dynamics and constitutes the first report of this gene in association with a severe neurodevelopmental disorder.D.M.E. and J.K. are supported by the Office of Naval Research (ONR) Grant N000141410538. M.S. is supported by the BBSRC (BB/K006231/1), a Wellcome Trust Institutional Strategic Support Award (WT097835MF, WT105618MA), and a Marie Curie Initial Training Network (ITN) action PerFuMe (316723). M.C.V.M., J.S., H.P., C.F., T.V. and W.A.G. are supported by the NGHRI Intramural Research Program. G.R. is supported by the Kahn Family Foundation and the Israeli Centers of Excellence (I-CORE) Program (ISF grant no. 41/11)

HGF/SF Increases Tumor Blood Volume: A Novel Tool for the In Vivo Functional Molecular Imaging of Met

Molecular functional and metabolic imaging allows visualization of disease-causing processes in living organisms. Here we present a new approach for the functional molecular imaging (FMI) of endogenous tyrosine kinase receptor activity using Met and its ligand, hepatocyte growth factor/scatter factor (HGF/SF), as a model. HGF/SF and Met play significant roles in the biology and pathogenesis of a wide variety of cancers and, therefore, may serve as potential targets for cancer prognosis and therapy. We have previously shown that Met activation by HGF/SF increases oxygen consumption in vitro and results in substantial alteration of blood oxygenation levels in vivo, as measured by blood oxygenation level-dependent magnetic resonance imaging. Using contrast medium (CM) ultrasound imaging, we demonstrate here that HGF/SF induces an increase in tumor blood volume. This increase is evident in small vessels, including vessels that were not detected before HGF/SF treatment. The specificity of the effect was validated by its inhibition using anti-HGF/SF antibodies. This change in tumor hemodynamics, induced by HGF/SF and measured by CM ultrasound, is further used as a tool for Met FMI in tumors. This novel noninvasive molecular imaging technique may be applied for the in vivo diagnosis, prognosis, and therapy of Met-expressing tumors

In Vivo Direct Molecular Imaging of Early Tumorigenesis and Malignant Progression Induced by Transgenic Expression of GFP-Met

The tyrosine kinase receptor Met and its ligand, hepatocyte growth factor/scatter factor (HGF/SF), play an important role in normal developmental processes, as well as in tumorigenicity and metastasis. We constructed a green fluorescent protein (GFP) Met chimeric molecule that functions similarly to the wild-type Met receptor and generated GFP-Met transgenic mice. These mice ubiquitously expressed GFP-Met in specific epithelial and endothelial cells and displayed enhanced GFP-Met fluorescence in sebaceous glands. Thirty-two percent of males spontaneously developed adenomas, adenocarcinomas, and angiosarcomas in their lower abdominal sebaceous glands. Approximately 70% of adenocarcinoma tumors metastasized to the kidneys, lungs, or liver. Quantitative subcellular-resolution intravital imaging revealed very high levels of GFP-Met in tumor lesions and in single isolated cells surrounding them, relative to normal sebaceous glands. These single cells preceded the formation of local and distal metastases. Higher GFP-Met levels correlated with earlier tumor onset and aggressiveness, further demonstrating the role of Met-HGF/SF signaling in cellular transformation and acquisition of invasive and metastatic phenotypes. Our novel mouse model and high-resolution intravital molecular imaging create a powerful tool that enables direct real-time molecular imaging of receptor expression and localization during primary events of tumorigenicity and metastasis at single-cell resolution

Off-pump surgery is not a contraindication for patients with a severely decreased ejection fraction

Background: A severely impaired left ventricular ejection fraction (EF) (30%) increases the risk of surgical myocardial revascularization. We evaluated the safety and feasibility of off-pump coronary artery bypass (OPCAB) surgery in patients with a severely decreased EF.Methods: We compared 79 patients with an EF ≤30% (group A) with 863 patients with an EF >30% (group B) who underwent myocardial revascularization between 2003 and 2008. The relationship between EF and outcome after OPCAB was assessed by univariate and logistic regression analyses. A composite end point was constructed from 30-day mortality, renal failure, length of stay in the intensive care unit (ICU) >2 days, neurologic complications, and use of an intra-aortic balloon pump (IABP). Additionally, the completeness of revascularization was assessed.Results: The mortality rates for groups A and B were comparable (1.3% and 2.0%, respectively; P = .55), and the 2 groups did not differ with regard to serious postoperative complications, such as stroke (2.5% versus 1.4% for groups A and B, respectively; P = .42), peripheral neurologic complications (2.5% versus 0.7%, P = .14), renal failure (0% versus 1.1%, P = 1.00), use of an IABP (1.3% versus 0.8%, P = .50), ICU length of stay >2 days (17.7% versus 19.6%, P = .77). Similarly, groups A and B did not differ with regard to ventilation time (11.2 ± 12.7 hours versus 12.4 ± 15.5 hours, P = .82), indicating similar postoperative courses for the 2 groups of patients. In contrast, the composite end point occurred significantly more frequently in group A (43.0% versus 29.7%, P = .02), a result driven by the increased rate of rethoracotomy for bleeding in that group (11.4% versus 2.9%, P = .001). The 2 groups were similar with respect to the total number of grafts used per patient (3.82 ± 0.89 versus 3.63 ± 1.01, P = .10) and the completeness of revascularization (94% versus 93%, P = .49).Conclusion: A standardized OPCAB approach is safe for patients with a severely decreased EF, and its use does not come at the cost of less complete revascularization