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ß-tubulin isotypes exhibit similar sequences but different activities, suggesting that limited sequence divergence is functionally important. We investigated this hypothesis for TUBB3/ß3, a ß-tubulin linked to aggressive cancers and chemoresistance in humans. We created mutant yeast strains with ß-tubulin alleles that mimic variant residues in ß3 and find that residues at the lateral interface are sufficient to alter microtubule dynamics and response to microtubule targeting agents. In HeLa cells, ß3 overexpression decreases the lifetime of microtubule growth, and this requires residues at the lateral interface. These microtubules exhibit a shorter region of EB binding at the plus end, suggesting faster lattice maturation, and resist stabilization by paclitaxel. Resistance requires the H1-S2 and H2-S3 regions at the lateral interface of ß3. Our results identify the mechanistic origins of the unique activity of ß3 tubulin and suggest that tubulin isotype expression may tune the rate of lattice maturation at growing microtubule plus ends in cells.
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The exon junction complex (EJC), nucleated by EIF4A3, is indispensable for mRNA fate and function throughout eukaryotes. We discover that EIF4A3 directly controls microtubules, independent of RNA, which is critical for neural wiring. While neuronal survival in the developing mouse cerebral cortex depends upon an intact EJC, axonal tract development requires only Eif4a3. Using human cortical organoids, we show that EIF4A3 disease mutations also impair neuronal growth, highlighting conserved functions relevant for neurodevelopmental pathology. Live imaging of growing neurons shows that EIF4A3 is essential for microtubule dynamics. Employing biochemistry and competition experiments, we demonstrate that EIF4A3 directly binds to microtubules, mutually exclusive of the EJC. Finally, in vitro reconstitution assays and rescue experiments demonstrate that EIF4A3 is sufficient to promote microtubule polymerization and that EIF4A3-microtubule association is a major contributor to axon growth. This reveals a fundamental mechanism by which neurons re-utilize core gene expression machinery to directly control the cytoskeleton.
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Axônios , Citoesqueleto , Fator de Iniciação 4A em Eucariotos , Microtúbulos , Fator de Iniciação 4A em Eucariotos/metabolismo , Fator de Iniciação 4A em Eucariotos/genética , Animais , Humanos , Microtúbulos/metabolismo , Axônios/metabolismo , Camundongos , Citoesqueleto/metabolismo , Neurônios/metabolismo , Ligação Proteica , Proteínas de Ligação a RNA/metabolismo , Proteínas de Ligação a RNA/genética , RNA Helicases DEAD-boxRESUMO
BACKGROUND AND OBJECTIVES: Recent data link exposure to repetitive head impacts (RHIs) from American football with increased white matter hyperintensity (WMH) burden. WMH might have unique characteristics in the context of RHI beyond vascular risk and normal aging processes. We evaluated biological correlates of WMH in former American football players, including markers of amyloid, tau, inflammation, axonal injury, neurodegeneration, and vascular health. METHODS: Participants underwent clinical interviews, MRI, and lumbar puncture as part of the Diagnostics, Imaging, and Genetics Network for the Objective Study and Evaluation of Chronic Traumatic Encephalopathy Research Project. Structural equation modeling tested direct and indirect effects between log-transformed total fluid-attenuated inversion recovery (FLAIR) lesion volumes (TLV) and the revised Framingham stroke risk profile (rFSRP), MRI-derived global metrics of cortical thickness and fractional anisotropy (FA), and CSF levels of amyloid ß1-42, p-tau181, soluble triggering receptor expressed on myeloid cells 2 (sTREM2), and neurofilament light. Covariates included age, race, education, body mass index, APOE ε4 carrier status, and evaluation site. Models were performed separately for former football players and a control group of asymptomatic men unexposed to RHI. RESULTS: In 180 former football players (mean age = 57.2, 36% Black), higher log(TLV) had direct associations with the following: higher rFSRP score (B = 0.26, 95% CI 0.07-0.40), higher p-tau181 (B = 0.17, 95% CI 0.01-0.43), lower FA (B = -0.28, 95% CI -0.42 to -0.13), and reduced cortical thickness (B = -0.25, 95% CI -0.45 to -0.08). In 60 asymptomatic unexposed men (mean age = 59.3, 40% Black), there were no direct effects on log(TLV) (rFSRP: B = -0.03, 95% CI -0.48 to 0.57; p-tau181: B = -0.30, 95% CI -1.14 to 0.37; FA: B = -0.07, 95% CI -0.48 to 0.42; or cortical thickness: B = -0.28, 95% CI -0.64 to 0.10). The former football players showed stronger associations between log(TLV) and rFSRP (1,069% difference in estimates), p-tau181 (158%), and FA (287%) than the unexposed men. DISCUSSION: Risk factors and biological correlates of WMH differed between former American football players and asymptomatic unexposed men. In addition to vascular health, p-tau181 and diffusion tensor imaging indices of white matter integrity showed stronger associations with WMH in the former football players. FLAIR WMH may have specific risk factors and pathologic underpinnings in RHI-exposed individuals.
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Futebol Americano , Substância Branca , Masculino , Humanos , Pessoa de Meia-Idade , Peptídeos beta-Amiloides , Imagem de Tensor de Difusão , Substância Branca/diagnóstico por imagem , Fatores de Risco , BiomarcadoresRESUMO
Objective: Memory problems are frequently endorsed in Veterans following mild traumatic brain injury (mTBI), but subjective complaints are poorly associated with objective memory performance. Few studies have examined associations between subjective memory complaints and brain morphometry. We investigated whether self-reported memory problems were associated with objective memory performance and cortical thickness in Veterans with a history of mTBI. Methods: 40 Veterans with a history of remote mTBI and 29 Veterans with no history of TBI completed the Prospective-Retrospective Memory Questionnaire (PRMQ), PTSD Checklist (PCL), California Verbal Learning Test-2nd edition (CVLT-II), and 3 T T1 structural magnetic resonance imaging. Cortical thickness was estimated in 14 a priori frontal and temporal regions. Multiple regressions adjusting for age and PCL scores examined associations between PRMQ, CVLT-II scores, and cortical thickness within each Veteran group. Results: Greater subjective memory complaints on the PRMQ were associated with lower cortical thickness in the right middle temporal gyrus (ß = 0.64, q = .004), right inferior temporal gyrus (ß = 0.56, q = .014), right rostral middle frontal gyrus (ß = 0.45, q = .046), and right rostral anterior cingulate gyrus (ß = 0.58, q = .014) in the mTBI group but not the control group (q's > .05). These associations remained significant after adjusting for CVLT-II learning. CVLT-II performance was not associated with PRMQ score or cortical thickness in either group. Conclusions: Subjective memory complaints were associated with lower cortical thickness in right frontal and temporal regions, but not with objective memory performance, in Veterans with histories of mTBI. Subjective complaints post-mTBI may indicate underlying brain morphometry independently of objective cognitive testing.
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Glioblastoma ranks among the most lethal of primary brain malignancies, with glioblastoma stem cells (GSCs) at the apex of tumor cellular hierarchies. Here, to discover novel therapeutic GSC targets, we interrogated gene expression profiles from GSCs, differentiated glioblastoma cells (DGCs), and neural stem cells (NSCs), revealing EYA2 as preferentially expressed by GSCs. Targeting EYA2 impaired GSC maintenance and induced cell cycle arrest, apoptosis, and loss of self-renewal. EYA2 displayed novel localization to centrosomes in GSCs, and EYA2 tyrosine (Tyr) phosphatase activity was essential for proper mitotic spindle assembly and survival of GSCs. Inhibition of the EYA2 Tyr phosphatase activity, via genetic or pharmacological means, mimicked EYA2 loss in GSCs in vitro and extended the survival of tumor-bearing mice. Supporting the clinical relevance of these findings, EYA2 portends poor patient prognosis in glioblastoma. Collectively, our data indicate that EYA2 phosphatase function plays selective critical roles in the growth and survival of GSCs, potentially offering a high therapeutic index for EYA2 inhibitors.
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Neoplasias Encefálicas/metabolismo , Glioblastoma/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Células-Tronco Neoplásicas/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Tirosina Fosfatases/metabolismo , Animais , Encéfalo/metabolismo , Morte Celular/fisiologia , Diferenciação Celular/fisiologia , Linhagem Celular Tumoral , Feminino , Regulação Neoplásica da Expressão Gênica/fisiologia , Humanos , Masculino , Camundongos , Células-Tronco Neurais/metabolismoRESUMO
Traumatic brain injury (TBI) is common among military personnel and the civilian population and is often followed by a heterogeneous array of clinical, cognitive, behavioral, mood, and neuroimaging changes. Unlike many neurological disorders that have a characteristic abnormal central neurologic area(s) of abnormality pathognomonic to the disorder, a sufficient head impact may cause focal, multifocal, diffuse or combination of injury to the brain. This inconsistent presentation makes it difficult to establish or validate biological and imaging markers that could help improve diagnostic and prognostic accuracy in this patient population. The purpose of this manuscript is to describe both the challenges and opportunities when conducting military-relevant TBI research and introduce the Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Military Brain Injury working group. ENIGMA is a worldwide consortium focused on improving replicability and analytical power through data sharing and collaboration. In this paper, we discuss challenges affecting efforts to aggregate data in this patient group. In addition, we highlight how "big data" approaches might be used to understand better the role that each of these variables might play in the imaging and functional phenotypes of TBI in Service member and Veteran populations, and how data may be used to examine important military specific issues such as return to duty, the late effects of combat-related injury, and alteration of the natural aging processes.
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Lesões Encefálicas Traumáticas , Militares , Transtornos de Estresse Pós-Traumáticos , Veteranos , Lesões Encefálicas Traumáticas/diagnóstico por imagem , Humanos , Imageamento por Ressonância MagnéticaRESUMO
OBJECTIVE: The number of older adults with alcohol use disorder (AUD) is expected to significantly increase in the coming years. Both aging and AUD have been associated with compromised white matter microstructure, although the extent of combined AUD and aging effects is unclear. This study investigated interactions between aging and AUD in cerebral white matter integrity using diffusion tensor imaging (DTI). METHOD: All participants (44 recently detoxified participants with AUD and 28 healthy controls; ages 31-64 years) completed neurocognitive testing and a DTI scan. Regions of interests were identified on Tract-Based Spatial Statistics images. Hierarchical multiple regression was used to examine interactions between age and AUD status on DTI values [e.g., fractional anisotropy (FA)]. RESULTS: Significant Age × AUD interactions were found across several prefrontal white matter regions (R(2)Δ = 5%-9%). Regional FA was negatively associated with age in the AUD group (rs = -.33 - -.53) but not in the control group (rs = .18 - -.32). This pattern remained after adjusting for lifetime history of drinking and recent drinking. Lifetime alcohol consumption negatively correlated with frontal white matter integrity in the AUD group (rs = -.33 - -.40). Finally, processing speed was significantly slower in the AUD group versus controls (p = .001) and was positively correlated with FA values in frontal white matter regions (rs = .34-.53). CONCLUSIONS: Cumulative alcohol consumption may affect frontal white matter integrity, and persons with AUD may be more prone to reductions in frontal white matter integrity with advancing age. These reductions in frontal white matter integrity may contribute to reductions in processing speed.