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Traumatic brain injury (TBI) is a major public health problem. Here, we developed a novel model of non-invasive TBI induced by laser irradiation in the telencephalon of adult zebrafish (Danio rerio) and assessed their behavior and neuromorphology to validate the model and evaluate potential targets for neuroreparative treatment. Overall, TBI induced hypolocomotion and anxiety-like behavior in the novel tank test, strikingly recapitulating responses in mammalian TBI models, hence supporting the face validity of our model. NeuN-positive cell staining was markedly reduced one day, but not seven days, after TBI, suggesting increased neuronal damage immediately after the injury, and its fast recovery. The brain-derived neurotrophic factor (Bdnf) level in the brain dropped immediately after the trauma, but fully recovered seven days later. A marker of microglial activation, Iba1, was elevated in the TBI brain, albeit decreasing from Day 3. The levels of hypoxia-inducible factor 1-alpha (Hif1a) increased 30 min after the injury, and recovered by Day 7, further supporting the construct validity of the model. Collectively, these findings suggest that our model of laser-induced brain injury in zebrafish reproduces mild TBI and can be a useful tool for TBI research and preclinical neuroprotective drug screening. © 2022 by the authors. Saint Petersburg State University, SPbU: 73026081; Russian Science Foundation, RSF: 20-65-46006 We thank Alisa S. Belova for technical support in experimental manipulations and cortisol assay. We also thank Anatoly A. Maslov for the idea of using laser radiation to introduce brain damage. A.V.K. lab is supported by St. Peterburg State University funds (Pure ID 73026081). This study was funded by Russian Science Foundation (grant No. 20-65-46006).

Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness and cataplexy (a sudden weakening of posture muscle tone usually triggered by emotion) caused by the loss of orexin neurons in the hypothalamus. Autoimmune mechanisms are implicated in narcolepsy by increased frequency of specific HLA alleles and the presence of specific autoantibody (anti-Tribbles homolog 2 (TRIB2) antibodies) in the sera of patients with narcolepsy. Presently, we passively transferred narcolepsy to naïve mice by injecting intra-cerebra-ventricularly (ICV) pooled IgG positive for anti-TRIB2 antibodies. Narcolepsy-IgG-injected mice had a loss of the NeuN (neuronal marker), synaptophysin (synaptic marker) and orexin-positive neurons in the lateral hypothalamus area in narcolepsy compared to control-IgG-injected mice and these changes were associated with narcolepsy-like immobility attacks at four weeks post injection and with hyperactivity and long term memory deficits in the staircase and novel object recognition tests. Similar behavioral and cognitive deficits are observed in narcoleptic patients. This is the first report of passive transfer of experimental narcolepsy to naïve mice induced by autoantibodies and supports the autoimmune pathogenesis in narcolepsy. © 2013 Elsevier Ltd.

Anti-NeuN (Neuronal Nuclei) is a monoclonal antibody used extensively to specifically detect post-mitotic neurons. Anti-NeuN reactivity is predominantly nuclear; by western it detects multiple bands ranging in molecular weight from 45 kDa to >75 kDa. Expression screening putatively identified R3hdm2 as NeuN; however immunoprecipitation and mass spectrometry of the two major NeuN species at 45-50 kDa identified both as the RNA binding protein Rbfox3 (a member of the Fox family of alternative splicing factors), confirming and extending the identification of the 45 kDa band as Rbfox3 by Kim et al. Mapping of the anti-NeuN reactive epitopes in both R3hdm2 and Rbfox3 reveals a common proline- and glutamine-rich domain that lies at the N-terminus of the Rbfox3 protein. Our data suggests that alternative splicing of the Rbfox3 pre-mRNA itself leads to the production of four protein isoforms that migrate in the 45-50 kDa range, and that one of these splicing choices regulates Rbfox3/NeuN sub-cellular steady-state distribution, through the addition or removal of a short C-terminal extension containing the second half of a bipartite hydrophobic proline-tyrosine nuclear localization signal. Rbfox3 regulates alternative splicing of the Rbfox2 pre-mRNA, producing a message encoding a dominant negative form of the Rbfox2 protein. We show here that nuclear Rbfox3 isoforms can also enhance the inclusion of cryptic exons in the Rbfox2 mRNA, resulting in nonsense-mediated decay of the message, thereby contributing to the negative regulation of Rbfox2 by Rbfox3 through a novel mechanism. Refereed/Peer-reviewed