Yoori Choi

Intracellular domains of amyloid precursor-like protein 2 interact with CP2 transcription factor in the nucleus and induce glycogen synthase kinase-3beta expression.

Amyloid precursor protein (APP) is a member of a gene family that includes two APP-like proteins, APLP1 and 2. Recently, it has been reported that APLP1 and 2 undergo presenilin-dependent γ-secretase cleavage, as does APP, resulting in the release of an ∼6 kDa intracellular C-terminal domain (ICD), which can translocate into the nucleus. In this study, we demonstrate that the APLP2-ICDs interact with CP2/LSF/LBP1 (CP2) transcription factor in the nucleus and induce the expression of glycogen synthase kinase 3β (GSK-3β), which has broad-ranged substrates such as τ- and β-catenin. The significance of this finding is substantiated by the in vivo evidence of the increase in the immunoreactivities for the nuclear C-terminal fragments of APLP2, and for GSK-3β in the AD patients’ brain. Taken together, these results suggest that APLP2-ICDs contribute to the AD pathogenesis, by inducing GSK-3β expression through the interaction with CP2 transcription factor in the nucleus.

Swedish amyloid precursor protein mutation increases phosphorylation of eIF2α in vitro and in vivo

Swedish double mutation (KM670/671NL) of amyloid precursor protein (Swe‐APP), a prevailing cause of familial Alzheimers disease (FAD), is known to increase in Aβ production both in vitro and in vivo, but its underlying molecular basis leading to Alzheimers disease (AD) pathogenesis remains to be elucidated, especially for the early phase of disease. We have confirmed initially that the expression of Swe‐APP mutant transgene reduced cell viability via ROS production but this effect was eliminated by an anti‐oxidative agent, vitamin E. We also found that eukaryotic translation initiation factor‐2α (eIF2α), which facilitates binding of initiator tRNA to ribosomes to set on protein synthesis, was phosphorylated in cultured cells expressing Swe‐APP. This increase in phosphorylated eIF2α was also attenuated significantly by treatment with vitamin E. The finding that eIF2α became highly phosphorylated by increased production of Aβ was substantiated in brain tissues of both an AD animal model and AD patients. Although an increase in Aβ production would result in cell death eventually (in late‐phase of the disease), the altered phosphorylation state of eIF2α evoked by Aβ may account for the decreased efficacy of mRNA translation and de novo protein synthesis required for synaptic plasticity, and may consequently be one of molecular causes for impairment of cognitive functions exhibited in the early phase of AD patients.

Swedish Amyloid Precursor Protein Mutation Increases Cell Cycle-Related Proteins In Vitro and In Vivo

Reactivation of the cell cycle, including DNA replication, might play a major role in Alzheimers disease. In this study, we report that the expressions of Swedish double mutation of amyloid precursor protein (Swe‐APP) or of the APP intracellular domain (AICD) into nerve growth factor (NGF)‐differentiated PC12 cells or rat primary cortical neurons increased mRNA and protein levels of cyclin D1 and cyclin B1. Treatment with lithium chloride (a glycogen synthase kinase‐3β inhibitor) down‐regulated cyclin B1 induced by Swe‐APP expression but up‐regulated cyclin D1 expression induced by Swe‐APP, suggesting that glycogen synthase kinase‐3β activity is involved in these expression changes of cyclins D1 and B1. Swe‐APP, which is a prevailing cause of familial Alzheimers disease, is well known to increase amyloid beta peptide production both in vitro and in vivo, but the underlying molecular means whereby it leads to the pathogenesis of AD remains unknown. The finding that cyclin D1 and B1 expressions were up‐regulated by Swe‐APP in in vitro cultured cells was substantiated in the brain tissues of Tg2576 mice, which harbor the Swe‐APP mutation. These results suggest that some disturbances in cell cycle regulation may be involved in Swe‐APP or AICD‐induced neurodegeneration and that these contribute to the pathogenesis of AD.

Neuritin Attenuates Cognitive Function Impairments in Tg2576 Mouse Model of Alzheimer's Disease

Neuritin, also known as CPG15, is a neurotrophic factor that was initially discovered in a screen to identify genes involved in activity-dependent synaptic plasticity. Neuritin plays multiple roles in the process of neural development and synaptic plasticity, although its binding receptor(s) and downstream signaling effectors remain unclear. In this study, we found that the cortical and hippocampal expression of neuritin is reduced in the brains of Alzheimers disease (AD) patients and demonstrated that viral-mediated expression of neuritin in the dentate gyrus of 13-month-old Tg2576 mice, an AD animal model, attenuated a deficit in learning and memory as assessed by a Morris water maze test. We also found that neuritin restored the reduction in dendritic spine density and the maturity of individual spines in primary hippocampal neuron cultures prepared from Tg2576 mice. It was also shown that viral-mediated expression of neuritin in the dentate gyrus of 7-week-old Sprague-Dawley rats increased neurogenesis in the hippocampus. Taken together, our results demonstrate that neuritin restores the reduction in dendritic spine density and the maturity of individual spines in primary hippocampal neurons from Tg2576 neurons, and also attenuates cognitive function deficits in Tg2576 mouse model of AD, suggesting that neuritin possesses a therapeutic potential for AD.

Maturation of metabolic connectivity of the adolescent rat brain

Neuroimaging has been used to examine developmental changes of the brain. While PET studies revealed maturation-related changes, maturation of metabolic connectivity of the brain is not yet understood. Here, we show that rat brain metabolism is reconfigured to achieve long-distance connections with higher energy efficiency during maturation. Metabolism increased in anterior cerebrum and decreased in thalamus and cerebellum during maturation. When functional covariance patterns of PET images were examined, metabolic networks including default mode network (DMN) were extracted. Connectivity increased between the anterior and posterior parts of DMN and sensory-motor cortices during maturation. Energy efficiency, a ratio of connectivity strength to metabolism of a region, increased in medial prefrontal and retrosplenial cortices. Our data revealed that metabolic networks mature to increase metabolic connections and establish its efficiency between large-scale spatial components from childhood to early adulthood. Neurodevelopmental diseases might be understood by abnormal reconfiguration of metabolic connectivity and efficiency. DOI: http://dx.doi.org/10.7554/eLife.11571.001

Detection of intra-brain cytoplasmic 1 (BC1) long noncoding RNA using graphene oxide-fluorescence beacon detector.

Detection of cellular expression of long noncoding RNAs (lncRNAs) was elusive due to the ambiguity of exposure of their reactive sequences associated with their secondary/tertiary structures and dynamic binding of proteins around lncRNAs. Herein, we developed graphene-based detection techniques exploiting the quenching capability of graphene oxide (GO) flakes for fluorescent dye (FAM)-labeled single-stranded siRNAs and consequent un-quenching by their detachment from GO by matching lncRNAs. A brain cytoplasmic 1 (BC1) lncRNA expression was significantly decreased by a siRNA, siBC1–1. GO quenched the FAM-labeled siBC1–1 peptide nucleic acid (PNA) probe, and this quenching was recovered by BC1. While FAM-siBC1–1-PNA-GO complex transfected spontaneously mouse or human neural stem cells, fluorescence was recovered only in mouse cells having high BC1 expression. Fluorescent dye-labeled single-stranded RNA-GO probe could detect the reactive exposed nucleic acid sequence of a cytoplasmic lncRNA expressing in the cytoplasm, which strategy can be used as a detection method of lncRNA expression.

Transgenic Mouse Expressing Optical MicroRNA Reporter for Monitoring MicroRNA-124 Action during Development

MicroRNAs (miRNAs) fine-tune target protein synthesis by suppressing gene expression, temporally changing along development and possibly in pathological conditions. A method to monitor the action of miRNAs in vivo shall help understand their dynamic behavior during development. In this study, we established a transgenic mouse harboring miR-124 responsive element in their luciferase-eGFP reporter transgenes which enabled monitoring the action of miR-124 in the brain and other organs in vivo by the bioluminescence imaging. The mouse model was produced and verified by imaging ex vivo so that luminescence by luciferase shone and then reduced during development with miR-124 expression. Bioluminescence dramatically decreased in the brain between embryonic day 13 and 16 as endogenous miR-124 expression increased, which sustained into adulthood. The inverse relationship of miR-124 expression was observed with luciferase bioluminescence and activity ex vivo as well as in vivo. Taken together, one can use this microRNA-transgenic mouse to investigate the temporal changes of microRNA action in vivo in the brain as well as in other organs.

Fluorescence imaging of in vivo miR-124a-induced neurogenesis of neuronal progenitor cells using neuron-specific reporters

BackgroundFacilitation of the differentiation of the stem cells toward neuronal lineage is crucial for enhancing the differentiation efficacy of grafted stem cells for the possible treatment of neurodegenerative disorders. MicroRNA124a (miR-124a) has been considered as a neuronal lineage regulator, possessing the capability to activate neuronal differentiation. In this study, using a neuronal promoter-based reporter and live-cell fluorescence imaging, we visualized in vitro and in vivo the enhanced neuronal differentiation of neuronal progenitor cells with miR-124a overproduction.MethodsThe neuron specific alpha1 tubulin promoter-driven RFP reporter (pTa1-RFP) was used to trace the miR-124a-induced neuronal differentiation in live cell condition. MiR-124a or miR-scramble in 10 % glucose buffer was mixed with in vivo-jetPEITM and in vivo fluorescence images were obtained daily using Maestro spectral fluorescent imager.ResultsNeurite outgrowth was clearly seen in F11 cells after miR-124a transfection, and immunofluorescence staining showed increase of Tuj1 and NF at 48 hours. When pTa1-RFP-transfected F11 cells were implanted simultaneously with miR-124a into the nude mice, gradually increasing reporter signals and morphological changes indicated neuronal differentiation for 48 hours in live cells in vitro. The miR-124a-treated F11 cells showed higher reporter signals on in vivo fluorescence imaging than miR-scramble-treated cells, which were verified by ex vivo confirmation of Tuj1 and NF expression.ConclusionsThese results indicated that neuronal reporter-based neurogenesis imaging can be used for monitoring miR-124a acting as neuronal activator when miRNA was injected in in vivo PEI-coated form for miRNA-mediated regenerative therapy.

Development of tau PET Imaging Ligands and their Utility in Preclinical and Clinical Studies

The pathological features of Alzheimer’s disease are senile plaques which are aggregates of β-amyloid peptides and neurofibrillary tangles in the brain. Neurofibrillary tangles are aggregates of hyperphosphorylated tau proteins, and these induce various other neurodegenerative diseases, such as progressive supranuclear palsy, corticobasal degeneration, frontotemporal lobar degeneration, frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), and chronic traumatic encephalopathy. In the case of Alzheimer’s disease, the measurement of neurofibrillary tangles associated with cognitive decline is suitable for differential diagnosis, disease progression assessment, and to monitor the effects of therapeutic treatment. This review discusses considerations for the development of tau ligands for imaging and summarizes the results of the first-in-human and preclinical studies of the tau tracers that have been developed thus far. The development of tau ligands for imaging studies will be helpful for differential diagnosis and for the development of therapeutic treatments for tauopathies including Alzheimer’s disease.

Various lengths of C-terminal fragments of amyloid precursor protein induce neurotoxicity, not only C31

with serum free medium for another 24 h (starvation). Results: The N2a cells overexpressing tau were more resistent to serum withdrawal-induced apoptosis. The protective effect was positively correlated with the relatively increased phosphrylation level of tau. We also found that the Akt was activated in cells overexpressing tau. Simultaneously, the phosphorylation level of FOXO3 increased (representing decreased activity) and the expression of p53 and Bax decreased. The antiapoptotic effects of tau almost disappeared by inhibition of Akt. Upon serum starvation, the expression level of catalytic subunit of PI3K (p110) increased significantly in cells overexpressing tau, whereas the relative level of the phosphorylated p85 was not changed. Conclusions: Our findings suggest that tau leads the cells to escape apoptosis by activating PI3K/Akt pathway and the activation of PI3K.