Mouse cerebellar granule cell differentiation: electrical activity regulates the GABAA receptor alpha 6 subunit gene.
GABAA receptor alpha6 subunit gene expression marks cerebellar granule cell maturation. To study this process, we used the Deltaalpha6lacZ mouse line, which has a lacZ reporter inserted into the alpha6 gene. At early stages of postnatal cerebellar development, alpha6-lacZ expression is mosaic; expression starts at postnatal day 5 in lobules 9 and 10, and alpha6-lacZ is switched on inside-out, appearing first in the deepest postmigratory granule cells. We looked for factors regulating this expression in cell culture. Membrane depolarization correlates inversely with alpha6-lacZ expression: granule cells grown in 25 mM [K+]o for 11-15 d do not express the alpha6 gene, whereas cultures grown for the same period in 5 mM [K+]o do. This is influenced by a critical early period: culturing for >/=3 d in 25 mM [K+]o curtails the ability to induce the alpha6 gene on transfer to 5 mM [K+]o. If the cells start in 5 mM [K+]o, however, they still express the alpha6-lacZ gene in 25 mM [K+]o. In contrast to granule cells grown in 5 mM [K+]o, cells cultured in 25 mM [K+]o exhibit no action potentials, mEPSCs, or mIPSCs. In chronic 5 mM [K+]o, factors may therefore be released that induce alpha6. Blockade of ionotropic and metabotropic GABA and glutamate receptors or L-, N-, and P/Q-type Ca2+ channels did not prevent alpha6-lacZ expression, but inhibition of action potentials with tetrodotoxin blocked expression in a subpopulation of cells.
Mellor
J R
JR
Medical Research Council Laboratory of Molecular Biology, Cambridge, CB2 2QH, United Kingdom.
Merlo
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D
Jones
A
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Wisden
W
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Randall
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AD
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000737:chemistry / Q000166:cytology*; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D007763:Lac Operon; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009414:Nerve Growth Factors / Q000494:pharmacology; D009474:Neurons / Q000737:chemistry* / Q000166:cytology; D010721:Phosphinic Acids / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000235:genetics* / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D019208:Brain-Derived Neurotrophic Factor; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D009414:Nerve Growth Factors; D010721:Phosphinic Acids; D010852:Picrotoxin; D011188:Potassium; D011412:Propanolamines; D011963:Receptors, GABA-A; D013779:Tetrodotoxin; D014284:Triiodothyronine; C085075:CGP 55845A