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CNS myelination is inhibited in the absence of the tumor overexpressed gene protein in oligodendrocytes
Abstracts / Int. J. Devl Neuroscience 47 (2015) 1–131
most sensitive markers of brain structure alterations associated with development and maturation. With this model, we can now extend the investigations to pathological conditions, opening new avenues for discovery of novel prognostic and diagnostic markers of brain disorders. http://dx.doi.org/10.1016/j.ijdevneu.2015.04.273 ISDN2014 0327 CNS myelination is inhibited in the absence of the tumor overexpressed gene protein in oligodendrocytes M.J. Maggipinto ∗ , J. Ford, H. Le, J. Weyman-Tutolo, E. Barbarese University of Connecticut Health Center, Farmington, CT, USA Tumor overexpressed gene (TOG) protein is found in RNA granules that contain mRNAs for myelin basic protein (MBP). It is also found in the myelin compartment in the CNS where MBP mRNA is translated. Knocking out (KO) TOG in immature oligodendrocytes in vivo results in mice with motor deficits resembling those of homozygous shiverer mutant mice. The motor deficits in the TOG KO are already apparent at the time of weaning just like in the shiverer suggesting severe dysmyelination. Only 20% of optic nerve axons are myelinated and thinly myelinated at that in the TOG KO despite the presence of a normal number of axons of normal caliber. The number of corpus callosum oligodendrocytes is also normal in these animals. The dysmyelination phenotype is compatible with the reduction in MBP protein that is seen by immunocytochemistry and Western blot analysis of the TOG KO brain. While shiverer do not express MBP because of a large deletion in the MBP gene, the reduction in MBP protein in the TOG KO is most likely due to failure to translate MBP transcripts. MBP transcripts are found in normal amount in the KO brain but may not assemble into transport/translation RNA granules from which MBP mRNA is translated in the myelin compartment normally. Similarly to shiverer, the severe dysmyelination leads to death of the TOG KO less than 5 months after birth. The motor, cellular and biochemical phenotype of the TOG KO mouse suggests that TOG is essential for the translation of MBP. http://dx.doi.org/10.1016/j.ijdevneu.2015.04.274 ISDN2014 0328 New mechanism for CGG repeat expansion disorders Rene Norman ∗ , Elisa Barbarese, John H. Carson University of Connecticut Health Center, Farmington, CT, USA The human exome contains over 200 genes with 6 or more CGG repeats, which are clustered near translation start codons. Many CGG repeat RNAs encode proteins that regulate translation and calcium homeostasis. CGG repeats can undergo expansions, which are often associated with late onset neurological and neuromuscular disorders. CGG repeat RNAs bind to hnRNP A2 and are incorporated into ribonucleoprotein complexes called granules. Experiments in vitro, in microinjected mouse neurons and in human fibroblasts indicate that CGG repeat expansions in one RNA can form duplexes with other CGG repeat RNAs in the same granule, resulting in overall inhibition of granule translation and dysregulation of calcium homeostasis. TMPyP4 is a porphyrin ring compound that binds to
101
CGG repeat RNAs, disrupts duplex formation, and rescues granule translation and calcium homeostasis. Based on these results we propose a novel “RNA duplex” hypothesis whereby duplex formation between CGG repeat expansion RNA and other CGG repeat RNAs in the same granule causes chronic inhibition of granule translation and dysregulation of calcium transients during development of neural and/or muscle cells, which can be rescued by blocking duplex formation with TMPyP4. This may represent a potential pathogenic mechanism and therapeutic strategy for late onset neurological and neuromuscular disorders associated with CGG repeat expansions. http://dx.doi.org/10.1016/j.ijdevneu.2015.04.275 ISDN2014 0329 MnTM-4-PyP protects cortical neurons against oxidative stress via induction of cellular antioxidant responses Kuoyuan Cheng, Fei Guo, Jiaqi Lu, Yuanzhao Cao, Qing Xia ∗ Department of Chemical Biology and State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, #38 Xueyuan Rd., Haidian Dist., Beijing 100191, PR China E-mail address: [email protected] (Q. Xia). Compromised cellular redox homeostasis and oxidative stress cause injuries in many diseases of the central nervous system. Among various antioxidant strategies, Manganese porphyrins (MnPs), designed as superoxide dismutase (SOD) mimics, were intensively investigated in various CNS disease models, and beneficial effects were observed. However their intracellular redox activities were complex and the mechanisms underlying their efficacies were not fully understood. Based on our previous studies, we further explored the mechanisms of a MnP (MnTM-4-PyP)’s protection against H2 O2 -induced oxidative stress in primary rat cortical neurons by investigating its influence on cellular antioxidant systems. MnTM-4-PyP pretreatment increased cell viability with reduced intracellular ROS level, while levels and activities of SODs but not catalase were elevated. The increased sod2 expression was independent of NF-B and AP-1. MnTM-4-PyP also induced Sirt3, a mitochondrial deacetylase important in antioxidant response, concomitantly increase in deacetylated and activated form of SOD2 was observed. This study highlights the regulation of endogenous antioxidant systems on different levels by MnTM-4-PyP, which possibly plays a significant role in its antioxidant effect. Thus the findings may promote further studies into the interaction of MnPs with endogenous redox systems and the mechanisms underlying their biomedical efficacies. http://dx.doi.org/10.1016/j.ijdevneu.2015.04.276
most sensitive markers of brain structure alterations associated with development and maturation. With this model, we can now extend the investigations to pathological conditions, opening new avenues for discovery of novel prognostic and diagnostic markers of brain disorders. http://dx.doi.org/10.1016/j.ijdevneu.2015.04.273 ISDN2014 0327 CNS myelination is inhibited in the absence of the tumor overexpressed gene protein in oligodendrocytes M.J. Maggipinto ∗ , J. Ford, H. Le, J. Weyman-Tutolo, E. Barbarese University of Connecticut Health Center, Farmington, CT, USA Tumor overexpressed gene (TOG) protein is found in RNA granules that contain mRNAs for myelin basic protein (MBP). It is also found in the myelin compartment in the CNS where MBP mRNA is translated. Knocking out (KO) TOG in immature oligodendrocytes in vivo results in mice with motor deficits resembling those of homozygous shiverer mutant mice. The motor deficits in the TOG KO are already apparent at the time of weaning just like in the shiverer suggesting severe dysmyelination. Only 20% of optic nerve axons are myelinated and thinly myelinated at that in the TOG KO despite the presence of a normal number of axons of normal caliber. The number of corpus callosum oligodendrocytes is also normal in these animals. The dysmyelination phenotype is compatible with the reduction in MBP protein that is seen by immunocytochemistry and Western blot analysis of the TOG KO brain. While shiverer do not express MBP because of a large deletion in the MBP gene, the reduction in MBP protein in the TOG KO is most likely due to failure to translate MBP transcripts. MBP transcripts are found in normal amount in the KO brain but may not assemble into transport/translation RNA granules from which MBP mRNA is translated in the myelin compartment normally. Similarly to shiverer, the severe dysmyelination leads to death of the TOG KO less than 5 months after birth. The motor, cellular and biochemical phenotype of the TOG KO mouse suggests that TOG is essential for the translation of MBP. http://dx.doi.org/10.1016/j.ijdevneu.2015.04.274 ISDN2014 0328 New mechanism for CGG repeat expansion disorders Rene Norman ∗ , Elisa Barbarese, John H. Carson University of Connecticut Health Center, Farmington, CT, USA The human exome contains over 200 genes with 6 or more CGG repeats, which are clustered near translation start codons. Many CGG repeat RNAs encode proteins that regulate translation and calcium homeostasis. CGG repeats can undergo expansions, which are often associated with late onset neurological and neuromuscular disorders. CGG repeat RNAs bind to hnRNP A2 and are incorporated into ribonucleoprotein complexes called granules. Experiments in vitro, in microinjected mouse neurons and in human fibroblasts indicate that CGG repeat expansions in one RNA can form duplexes with other CGG repeat RNAs in the same granule, resulting in overall inhibition of granule translation and dysregulation of calcium homeostasis. TMPyP4 is a porphyrin ring compound that binds to
101
CGG repeat RNAs, disrupts duplex formation, and rescues granule translation and calcium homeostasis. Based on these results we propose a novel “RNA duplex” hypothesis whereby duplex formation between CGG repeat expansion RNA and other CGG repeat RNAs in the same granule causes chronic inhibition of granule translation and dysregulation of calcium transients during development of neural and/or muscle cells, which can be rescued by blocking duplex formation with TMPyP4. This may represent a potential pathogenic mechanism and therapeutic strategy for late onset neurological and neuromuscular disorders associated with CGG repeat expansions. http://dx.doi.org/10.1016/j.ijdevneu.2015.04.275 ISDN2014 0329 MnTM-4-PyP protects cortical neurons against oxidative stress via induction of cellular antioxidant responses Kuoyuan Cheng, Fei Guo, Jiaqi Lu, Yuanzhao Cao, Qing Xia ∗ Department of Chemical Biology and State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, #38 Xueyuan Rd., Haidian Dist., Beijing 100191, PR China E-mail address: [email protected] (Q. Xia). Compromised cellular redox homeostasis and oxidative stress cause injuries in many diseases of the central nervous system. Among various antioxidant strategies, Manganese porphyrins (MnPs), designed as superoxide dismutase (SOD) mimics, were intensively investigated in various CNS disease models, and beneficial effects were observed. However their intracellular redox activities were complex and the mechanisms underlying their efficacies were not fully understood. Based on our previous studies, we further explored the mechanisms of a MnP (MnTM-4-PyP)’s protection against H2 O2 -induced oxidative stress in primary rat cortical neurons by investigating its influence on cellular antioxidant systems. MnTM-4-PyP pretreatment increased cell viability with reduced intracellular ROS level, while levels and activities of SODs but not catalase were elevated. The increased sod2 expression was independent of NF-B and AP-1. MnTM-4-PyP also induced Sirt3, a mitochondrial deacetylase important in antioxidant response, concomitantly increase in deacetylated and activated form of SOD2 was observed. This study highlights the regulation of endogenous antioxidant systems on different levels by MnTM-4-PyP, which possibly plays a significant role in its antioxidant effect. Thus the findings may promote further studies into the interaction of MnPs with endogenous redox systems and the mechanisms underlying their biomedical efficacies. http://dx.doi.org/10.1016/j.ijdevneu.2015.04.276