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Activated microglia inhibit axonal regeneration by RGMa
Abstracts / Neuroscience Research 71S (2011) e108–e415
investigating the expression pattern and function of candidate molecules that contribute to form the correct trajectories of the dorsal spinal nerve. We never give up our study although our laboratory is 57 km (35 miles) away from the damaged Fukushima Daiichi nuclear power plant. Research fund: KAKENHI21590218. doi:10.1016/j.neures.2011.07.1474
P4-f04 The effect of olfactory stimuli during development on the innate circuit formation Takahiro Yamazaki , Hitoshi Sakano Dept. of Biophysics & Biochemistry, Grad. Sch. of Sci, The Univ. of Tokyo, Japan Innate behaviors are essential for survival in the competitive environment. Mice show innate behaviors, aversive behavior and freezing behavior, towards their predators. It has been reported that the dorsal part of the main olfactory bulb (OB) processes the innate circuits. We focus on the innate circuit for freezing behavior towards predators, because the ligand to elicit the freezing behavior has been identified as TMT and the behavior is specific. It is assumed that the innate circuits are formed solely by genetic information, and the innate circuits are invariant. During the postnatal 2 weeks, however, the brain is still developing and the environmental stimuli is crucial for the development. This indicates that it is possible that the environmental stimuli make some influence on the innate neural circuit formation. To examine this possibility, labeling the innate circuits is inevitable. Here, we evaluate the effect of olfactory stimuli during development on the freezing behavior, and show the method to visualize the second order neurons connecting the specific glomerulus in order to visualize the innate circuit. Research fund: Grant-in-Aid for JSPS Fellows, Grant-in-Aid for Specially Promoted Research. doi:10.1016/j.neures.2011.07.1475
P4-f05 Activated microglia inhibit axonal regeneration by RGMa Mari Kitayama 1 Yamashita 1
, Masaki
Ueno 1 , Toru
Itakura 2 , Toshihide
1 Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, Osaka 2 Department Neurological Surgery, Wakayama Medical University, Wakayama
Spinal cord injury can damage neural network, causing motor and sensory dysfunction. Functional recovery needs axonal regrowth and regeneration of neural network. Divergent effects of activated microglia to neurons have been reported, suggesting that activated microglia might affect axonal regeneration after spinal cord injury. In this study, we show that activated microglia inhibit axonal growth by repulsive guidance molecule a (RGMa). In vitro study, primary cortical neurons harvested from embryonic mice (E18) were co-cultured with primary microglia. It was found that activated microglia by LPS significantly inhibited neurite outgrowth. The outgrowth inhibition was not induced in co-culture with transwell plate, suggesting that adhesion molecules expressed in activated microglia might be involved in this process. We hypothesized that activated microglia inhibited neurite outgrowth by RGMa. Interestingly, the addition of RGMa antibody rescued neurite outgrowth inhibition by activated microglia. Furthermore, minocycline, an inhibitor for activation of microglia, limited neurite outgrowth inhibition with the reduction of RGMa expression. As an in vivo model, we investigated activated microglia-mediated axonal dieback after spinal cord injury in mice. Administration of minocycline reduced microglial numbers and RGMa expression, and diminished the dieback of corticospinal tract. These results indicate that activated microglia inhibit axonal gowth and regeneration by RGMa. doi:10.1016/j.neures.2011.07.1476
P4-f06 p75 neurotrophin receptor mediates ephrin-B3 signaling for axonal growth inhibition Noriko Uesugi , Masaki Ueno, Yuki Fujita, Toshihide Yamashita Dept. of Mol. Neurosci., Grad. Sch. of Med., Osaka Univ., Osaka, Japan p75 neurotrophin receptor, a member of the TNF (tumor necrosis factor) receptor family, is known as a key molecule for axonal growth inhibition in the central nervous system (CNS). Axon elongation in CNS is inhibited by molecules expressed in oligodendrocytes, e.g. MAG, Nogo, OMgp. These inhibitory molecules bind to p75 receptor indirectly, activate RhoA, known
e337
as a cytoskeletal regulator, thus suppress axonal elongation. It has been reported that ephrin-B3, a member of the ephrin family, is also expressed in oligodendrocytes in CNS and inhibits axonal elongation in vitro. Here we report that p75 neurotrophin receptor mediates the signal of ephrinB3 for axonal growth inhibition. The axonal growth of cortical neurons was inhibited on ephrin-B3 coated dishes. This inhibitory effect of ephrin-B3 was reversed by treatment with Pep5, an inhibitory peptide of the signal transduction of p75 receptor. Furthermore, immunoprecipitation assays showed that EphA4, one of the receptors for ephrin-B3, associates with p75 receptor, suggesting that p75 receptor mediates ephrin-B3 signal by forming receptor complex with EphA4. Our results reveal a novel signaling cascade of ephrin-B3-induced axonal growth inhibition via p75 receptor. Research fund: JSPS Research Fellowships for Young Scientists. doi:10.1016/j.neures.2011.07.1477
P4-f07 Identification of a functional domain in endogenous Nogo66 receptor antagonist LOTUS Yuji Kurihara 1,2 , Masumi Iketani 1 , Hiromu Itoh 1 , Kuniyuki Nishiyama 1 , Fumio Nakamura 1 , Nobuhisa Mizuki 2 , Yoshio 1 1 Goshima , Kohtaro Takei 1 Dept. of Mol. Pharmacol. & Neurobiol., Grad. Sch. of Med., Yokohama City Univ., Yokohama, Japan 2 Dept. of Ophthalmol., Grad. Sch. of Med., Yokohama City Univ., Yokohama, Japan
Axonal regeneration after injury in the mammalian adult central nervous system (CNS) is limited by myelin-derived axon growth inhibitors, such as Nogo. Nogo66 receptor (NgR1) is a common receptor of these inhibitors. Recently, we have found that lateral olfactory tract usher substance (LOTUS), which is identified as a novel key molecule for LOT formation, suppresses Nogo66–NgR1 binding and thereby Nogo66-induced growth cone collapse. However, which region of LOTUS is involved in the antagonistic action to NgR1 has not been determined. In this study, we examined the functional domain of LOTUS by using the deletion mutants. We found that two Cterminal domains of LOTUS was the binding site to NgR1. The C-terminal domains, named UCa, co-expressed with NgR1 on COS7 cells completely inhibited binding of Nogo66 to NgR1. Furthermore, UCa domain overexpressed in chick dorsal root ganglion neurons suppressed Nogo66-induced growth cone collapse. These results suggest that UCa domain of LOTUS acts as a functional domain in antagonism to NgR1. In therapeutic approaches for the CNS injury, UCa domain might help to promote neural regeneration. doi:10.1016/j.neures.2011.07.1478
P4-f08 Importance of lesion scars in the tissue healing and inhibition of axonal regeneration after traumatic injury of the brain
Nozomu Yoshioka 1,2 , Hiroaki Asou 3 , Junko Kimura-Kuroda 1 , Shin-ichi Hisanaga 2 , Hitoshi Kawano 1 1
Tokyo Met Inst of Med Sci 2 Tokyo Metro Univ 3 Keio Univ
Although glial scar has been considered as an obstacle to axonal regeneration in the damaged central nervous system (CNS), recent evidence indicates that reactive astrocytes play a crucial role in the repair of the blood–brain barrier (BBB). At 3 days after injury of the mouse brain, destruction of the BBB was observed around the lesion site where astrocytes were absent and NG2positive glial progenitors proliferated. These NG2-positive cells expressed the astrocyte lineage marker Camsap1. At 10 days, Camsap1-positive astrocytes which acquired GFAP and lost NG2 formed the glial scar around the lesion site, and the BBB was restored around the lesion site. These results suggest that NG2-positive cells became astrocyte precursors and involved in the CNS healing. We have examined the mouse brain with a unilateral transection of nigrostriatal dopaminergic pathway and demonstrated that a fibrotic scar formed by invading meningeal fibroblasts in the lesion site is another impediment for axonal regeneration. The fibrotic scar formation is suppressed by the inhibitor of transforming growth factor- (TGF-) receptor kinase in the lesioned brain. In these mice, repair of the BBB was not disturbed and regeneration of dopaminergic axons was promoted. These results suggest that the fibrotic scar elimination would be a reliable strategy to repair the injured CNS. doi:10.1016/j.neures.2011.07.1479
investigating the expression pattern and function of candidate molecules that contribute to form the correct trajectories of the dorsal spinal nerve. We never give up our study although our laboratory is 57 km (35 miles) away from the damaged Fukushima Daiichi nuclear power plant. Research fund: KAKENHI21590218. doi:10.1016/j.neures.2011.07.1474
P4-f04 The effect of olfactory stimuli during development on the innate circuit formation Takahiro Yamazaki , Hitoshi Sakano Dept. of Biophysics & Biochemistry, Grad. Sch. of Sci, The Univ. of Tokyo, Japan Innate behaviors are essential for survival in the competitive environment. Mice show innate behaviors, aversive behavior and freezing behavior, towards their predators. It has been reported that the dorsal part of the main olfactory bulb (OB) processes the innate circuits. We focus on the innate circuit for freezing behavior towards predators, because the ligand to elicit the freezing behavior has been identified as TMT and the behavior is specific. It is assumed that the innate circuits are formed solely by genetic information, and the innate circuits are invariant. During the postnatal 2 weeks, however, the brain is still developing and the environmental stimuli is crucial for the development. This indicates that it is possible that the environmental stimuli make some influence on the innate neural circuit formation. To examine this possibility, labeling the innate circuits is inevitable. Here, we evaluate the effect of olfactory stimuli during development on the freezing behavior, and show the method to visualize the second order neurons connecting the specific glomerulus in order to visualize the innate circuit. Research fund: Grant-in-Aid for JSPS Fellows, Grant-in-Aid for Specially Promoted Research. doi:10.1016/j.neures.2011.07.1475
P4-f05 Activated microglia inhibit axonal regeneration by RGMa Mari Kitayama 1 Yamashita 1
, Masaki
Ueno 1 , Toru
Itakura 2 , Toshihide
1 Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, Osaka 2 Department Neurological Surgery, Wakayama Medical University, Wakayama
Spinal cord injury can damage neural network, causing motor and sensory dysfunction. Functional recovery needs axonal regrowth and regeneration of neural network. Divergent effects of activated microglia to neurons have been reported, suggesting that activated microglia might affect axonal regeneration after spinal cord injury. In this study, we show that activated microglia inhibit axonal growth by repulsive guidance molecule a (RGMa). In vitro study, primary cortical neurons harvested from embryonic mice (E18) were co-cultured with primary microglia. It was found that activated microglia by LPS significantly inhibited neurite outgrowth. The outgrowth inhibition was not induced in co-culture with transwell plate, suggesting that adhesion molecules expressed in activated microglia might be involved in this process. We hypothesized that activated microglia inhibited neurite outgrowth by RGMa. Interestingly, the addition of RGMa antibody rescued neurite outgrowth inhibition by activated microglia. Furthermore, minocycline, an inhibitor for activation of microglia, limited neurite outgrowth inhibition with the reduction of RGMa expression. As an in vivo model, we investigated activated microglia-mediated axonal dieback after spinal cord injury in mice. Administration of minocycline reduced microglial numbers and RGMa expression, and diminished the dieback of corticospinal tract. These results indicate that activated microglia inhibit axonal gowth and regeneration by RGMa. doi:10.1016/j.neures.2011.07.1476
P4-f06 p75 neurotrophin receptor mediates ephrin-B3 signaling for axonal growth inhibition Noriko Uesugi , Masaki Ueno, Yuki Fujita, Toshihide Yamashita Dept. of Mol. Neurosci., Grad. Sch. of Med., Osaka Univ., Osaka, Japan p75 neurotrophin receptor, a member of the TNF (tumor necrosis factor) receptor family, is known as a key molecule for axonal growth inhibition in the central nervous system (CNS). Axon elongation in CNS is inhibited by molecules expressed in oligodendrocytes, e.g. MAG, Nogo, OMgp. These inhibitory molecules bind to p75 receptor indirectly, activate RhoA, known
e337
as a cytoskeletal regulator, thus suppress axonal elongation. It has been reported that ephrin-B3, a member of the ephrin family, is also expressed in oligodendrocytes in CNS and inhibits axonal elongation in vitro. Here we report that p75 neurotrophin receptor mediates the signal of ephrinB3 for axonal growth inhibition. The axonal growth of cortical neurons was inhibited on ephrin-B3 coated dishes. This inhibitory effect of ephrin-B3 was reversed by treatment with Pep5, an inhibitory peptide of the signal transduction of p75 receptor. Furthermore, immunoprecipitation assays showed that EphA4, one of the receptors for ephrin-B3, associates with p75 receptor, suggesting that p75 receptor mediates ephrin-B3 signal by forming receptor complex with EphA4. Our results reveal a novel signaling cascade of ephrin-B3-induced axonal growth inhibition via p75 receptor. Research fund: JSPS Research Fellowships for Young Scientists. doi:10.1016/j.neures.2011.07.1477
P4-f07 Identification of a functional domain in endogenous Nogo66 receptor antagonist LOTUS Yuji Kurihara 1,2 , Masumi Iketani 1 , Hiromu Itoh 1 , Kuniyuki Nishiyama 1 , Fumio Nakamura 1 , Nobuhisa Mizuki 2 , Yoshio 1 1 Goshima , Kohtaro Takei 1 Dept. of Mol. Pharmacol. & Neurobiol., Grad. Sch. of Med., Yokohama City Univ., Yokohama, Japan 2 Dept. of Ophthalmol., Grad. Sch. of Med., Yokohama City Univ., Yokohama, Japan
Axonal regeneration after injury in the mammalian adult central nervous system (CNS) is limited by myelin-derived axon growth inhibitors, such as Nogo. Nogo66 receptor (NgR1) is a common receptor of these inhibitors. Recently, we have found that lateral olfactory tract usher substance (LOTUS), which is identified as a novel key molecule for LOT formation, suppresses Nogo66–NgR1 binding and thereby Nogo66-induced growth cone collapse. However, which region of LOTUS is involved in the antagonistic action to NgR1 has not been determined. In this study, we examined the functional domain of LOTUS by using the deletion mutants. We found that two Cterminal domains of LOTUS was the binding site to NgR1. The C-terminal domains, named UCa, co-expressed with NgR1 on COS7 cells completely inhibited binding of Nogo66 to NgR1. Furthermore, UCa domain overexpressed in chick dorsal root ganglion neurons suppressed Nogo66-induced growth cone collapse. These results suggest that UCa domain of LOTUS acts as a functional domain in antagonism to NgR1. In therapeutic approaches for the CNS injury, UCa domain might help to promote neural regeneration. doi:10.1016/j.neures.2011.07.1478
P4-f08 Importance of lesion scars in the tissue healing and inhibition of axonal regeneration after traumatic injury of the brain
Nozomu Yoshioka 1,2 , Hiroaki Asou 3 , Junko Kimura-Kuroda 1 , Shin-ichi Hisanaga 2 , Hitoshi Kawano 1 1
Tokyo Met Inst of Med Sci 2 Tokyo Metro Univ 3 Keio Univ
Although glial scar has been considered as an obstacle to axonal regeneration in the damaged central nervous system (CNS), recent evidence indicates that reactive astrocytes play a crucial role in the repair of the blood–brain barrier (BBB). At 3 days after injury of the mouse brain, destruction of the BBB was observed around the lesion site where astrocytes were absent and NG2positive glial progenitors proliferated. These NG2-positive cells expressed the astrocyte lineage marker Camsap1. At 10 days, Camsap1-positive astrocytes which acquired GFAP and lost NG2 formed the glial scar around the lesion site, and the BBB was restored around the lesion site. These results suggest that NG2-positive cells became astrocyte precursors and involved in the CNS healing. We have examined the mouse brain with a unilateral transection of nigrostriatal dopaminergic pathway and demonstrated that a fibrotic scar formed by invading meningeal fibroblasts in the lesion site is another impediment for axonal regeneration. The fibrotic scar formation is suppressed by the inhibitor of transforming growth factor- (TGF-) receptor kinase in the lesioned brain. In these mice, repair of the BBB was not disturbed and regeneration of dopaminergic axons was promoted. These results suggest that the fibrotic scar elimination would be a reliable strategy to repair the injured CNS. doi:10.1016/j.neures.2011.07.1479