Role of RhoA in activity-dependent cortical axon branching.
During development, axon branching is influenced by sensory-evoked and spontaneous neural activity. We studied the molecular mechanism that underlies activity-dependent branch formation at horizontally elongating axons (horizontal axons) in the upper cortical layers, focusing on Rho family small GTPases. Axonal labeling with enhanced yellow fluorescent protein showed that horizontal axons formed several branches in organotypic slice cultures. This branch formation was considerably increased by introducing constitutively active RhoA and was slightly inhibited by dominant-negative RhoA. Activators and inhibitors of endogenous RhoA signaling also promoted and inhibited branching, respectively. Daily imaging of horizontal axon growth further demonstrated that constitutively active RhoA increased the dynamic addition and loss of branches. Moreover, the amount of active RhoA relative to the total amount of RhoA was examined by a pull-down assay in cortical slices treated with sodium channel or glutamate receptor blockers to reduce neural activity. Activity blockade significantly decreased active RhoA compared with normal culture conditions, in which spontaneous firing is prominent. These findings suggest that RhoA signaling acts as a positive regulator for activity-dependent axon branching in cortical neurons.
Ohnami
Soichiro
S
Laboratory of Cellular and Molecular Neurobiology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan.
Endo
Mitsuharu
M
Hirai
Satoshi
S
Uesaka
Naofumi
N
Hatanaka
Yumiko
Y
Yamashita
Toshihide
T
Yamamoto
Nobuhiko
N
D000577:Amides / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018274:Electroporation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology; D018613:Microscopy, Confocal / Q000379:methods; D009474:Neurons / Q000166:cytology*; D009778:Occipital Lobe / Q000166:cytology*; D009924:Organ Culture Techniques; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000502:physiology*
D000577:Amides; D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D008164:Luminescent Proteins; D008246:Lysophospholipids; D011725:Pyridines; D026941:Sodium Channel Blockers; C054562:yellow fluorescent protein, Bacteria; C108830:Y 27632; D013779:Tetrodotoxin; D020742:rhoA GTP-Binding Protein; C032881:lysophosphatidic acid
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