Symposium

Symposium 23 Next-generation neurotrophic factor research: new findings, application of optogenetics and bioluminescence, and expectation of drug discovery シンポジウム23 次世代神経栄養因子研究：新規メカニズムの発見から遺伝子発現の可視化および光遺伝学の応用による新展開と創薬への期待

SY23-1 Genetic dissection of p75 neurotrophin receptor signaling in mouse models of Alzheimer’s Disease Ibanez Carlos F.^1,2,3，Yi Chenju^1,2，Goh Ket Yin^1,2 ¹Department of Physiology, National University of Singapore, Singapore ²Life Sciences Institute, National University of Singapore, Singapore ³Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden The p75 neurotrophin receptor (p75ntr) is a member of the Tumor Necrosis Factor Receptor (TNFR) Superfamily of “death receptors”. Neurotrophin binding to p75ntr can induce neuronal death, neurite dystrophy, synapse elimination and synaptic long term depression (LTD) . It has therefore been regarded as a prominent contributor to neurodegenerative processes, such as those undergoing in Alzheimer’s Disease (AD) . The role of p75ntr in AD is unclear, as it has been reported to contribute to both Aβ peptide clearance as well as Aβ-mediated neurodegeneration. This presentation will summarize the latest results of our team using mice carrying different alleles of p75ntr lacking distinct functions. Through this approach, we have been able to dissect the positive and negative roles played by p75ntr in the development of AD neuropathology.		SY23-2 The role of a novel BDNF subtype BDNF pro-peptide in brain aging and neurological diseases 加齢にともに増加する新しい神経栄養因子サブタイプと神経変性疾患 Kojima Masami（小島正己） Biomedical Research Institute, AIST, Osaka, Japan We have now studied the in vivo role of the BDNF pro-peptide, which is produced together with BDNF by a post-translational mechanism of BDNF, proteolytic processing of precursor BDNF, in brain because the BDNF pro-peptide has an ability to enhance a synaptic depression mechanism, long-term depression (LTD) in hippocampal slices. In the present study, we investigated the protein levels of the BDNF pro-peptide in some brain regions of aged mice. Interestingly, in aged mice (104 weeks or 1.5 years old), the BDNF pro-peptide level was pronouncedly higher than that of 13 weeks old mice, showing that the biological action of the BDNF pro-peptide is enhanced with aging. By contrast, mature form of BDNF showed no significant change or decrease in its levels with aging (13-104 weeks), suggesting the BDNF action may diminish with age. Notably, in line with that of the BDNF pro-peptide, Tau, a microtubule-associated principal component of neurofibrillary tangles in Alzheimer’s disease (AD), exhibited a hyperphosphorylation in the tissue samples from 104 weeks old mice. These data suggest the role of the BDNF pro-peptide in the progression of AD. Furthermore, as with the studies of BDNF and its pro-peptide, we examined the protein levels of p75 a receptor component involved in the BDNF pro-peptide biological action and an AD brain protein Tau. In addition to these in vivo studies, we will show the in vitro data, which would support the findings of in vivo studies.

SY23-3 Visualization of changes in BDNF gene expression in vivo and construction of drug screening using luciferase-based bioluminescence ホタル発光酵素ルシフェラーゼを用いたBDNF遺伝子発現モニタリングマウスの開発と創薬への応用 Fukuchi Mamoru（福地守） Lab. of Mol. Neurosci., Fac. of Pharmacy, Takasaki Univ, of Health & Welfare BDNF (Brain-derived neurotrophic factor), a member of neurotrophin family, plays a crucial role in expressing a variety of neural functions such as memory consolidation. In addition, alterations in BDNF level has been reported in psychiatric and neurodegenerative diseases including depression and Alzheimer’s disease, suggesting that BDNF could be a biomarker and drug target for these diseases. Here, we generated a novel transgenic mouse strain termed “BDNF-Luc mouse” to measure the changes in BDNF gene expression using firefly luciferase as an imaging probe. We detected the bioluminescence signal from living BDNF-Luc mice after intraperitoneal administration of D-luciferin. Despite high levels of BDNF-Luc expression in the brain, it was difficult to detect a signal from the brain region, probably because of its poorly penetrable (short-wavelength) bioluminescence. However, we could detect the changes in the bioluminescence signal in the brain region using a luciferin analogue generating a near-infrared wavelength of bioluminescence. These results show that changes in BDNF expression can be visualized using living mice, and that the Tg mouse could be a powerful tool for clarification of the role of BDNF expression in pathophysiological and physiological conditions. Recently, we also constructed a screening assay to detect activators of BDNF gene transcription by measuring luciferase activity of each well, using primary cultures of cortical cells prepared from BDNF-Luc mouse embryos in 96-well plate format. I would like to introduce this method and discuss the potential for therapeutic strategy for neural diseases.		SY23-4 Optical activation of neural plasticity 光による神経可塑性の活性化 Umemori Jyuzo（梅森十三）¹，Wnkle Frederike¹，Didio Giuliano¹，Llach Pou Maria¹，Antila Hanna¹，Buj Chloe²，Guirado Ramon³，Taila Tomi^1,4，Lauri Sari⁵，Castren Eero¹ ¹Neuroscience center, Department of HiLife, University of Helsinki, Finland ²Neurobiologie, Neurophysiologie, Neuropathologie, Aix-Marseille University, France ³Neurobiology Unit, Department of Cell Biology, BIOTECMED, Universitat de Valencia, Spain ⁴Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Finland ⁵Division of Physiology and Neuroscience, Department of Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland We have so far demonstrated that antidepressant drug treatment induces a juvenile critical period-like plasticity (iPlasticity) in the adult visual cortex, amygdala, and hippocampus, and its combination with training, rehabilitation, or psychotherapy consequently ameliorates neuropsychiatric symptoms. We have shown that BDNF/TrkB signaling is a key factor, but it is not still clear which and how neuronal networks are involved in iPlasticity. In order to address these questions, we developed lentiviruses expressing a photoactivatable TrkB (optoTrkB), where full length TrkB is conjugated with photolyase homology region that dimerizes upon blue LED light exposure and can be activated at arbitrary timing in specific neuronal-subpopulations. Here we report its plastic effects using behavioral paradigms in fear erasure and shift of ocular dominance.We infected optoTrkB lentivirus into CA1 region of the ventral hippocampus of mice with specific expression in pyramidal neurons, and optically stimulated the optoTrkB during fear extinction training after fear conditioning. The activation of TrkB promoted fear erasure especially in context-dependent manner, indicating a hippocampal TrkB activation dependent mechanism in long term fear erasure. Next, optoTrkB lentivirus directing specifially in Parvalbumin-positive (PV) GABAergic interneurons was infected into the visual cortex of adult mice that were optically stimulated during monocular deprivation of the dominant eye. The activation shifts ocular dominance towards the non-deprived eye, showing a new plastic effect and opposing role of intracortical inhibition regulated by PV interneurons in ocular dominance. Our optTrkB can be proposed as a new tool to investigate future treatments neuropsychological disorders.