title: A critical and cell-autonomous role for MeCP2 in synaptic scaling up.
abstract: Rett syndrome (Rett) is the leading genetic cause of mental retardation in females. Most cases of Rett are caused by loss-of-function mutations in the gene coding for the transcriptional regulator methyl-CpG binding protein 2 (MeCP2), but despite much effort, it remains unclear how a loss of MeCP2 function generates the neurological deficits of Rett. Here we show that MeCP2 plays an essential and cell-autonomous role in homeostatic synaptic scaling up in response to reduced firing or reduced sensory drive in rat visual cortical pyramidal neurons. We found that acute RNAi knockdown of MeCP2 blocked synaptic scaling within targeted neocortical pyramidal neurons. Furthermore, MeCP2 knockdown decreased excitatory synapse number without affecting basal mEPSC amplitude or AMPAR accumulation at spared synapses, demonstrating that MeCP2 acts cell-autonomously to maintain both excitatory synapse number and synaptic scaling in individual neocortical neurons. Finally, we used a mouse model of Rett to show that MeCP2 loss prevents homeostatic synaptic scaling up in response to visual deprivation in vivo, demonstrating for the first time that MeCP2 loss disrupts homeostatic plasticity within the intact developing neocortex. Our results establish MeCP2 as a critical mediator of synaptic scaling and raise the possibility that some of the neurological defects of Rett arise from a disruption of homeostatic plasticity.
authors.affiliation: Department of Biology and Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454, USA.
authors.forename: Melissa P
authors.initials: MP
authors.lastname: Blackman
authors.forename: Biljana
authors.initials: B
authors.lastname: Djukic
authors.forename: Sacha B
authors.initials: SB
authors.lastname: Nelson
authors.forename: Gina G
authors.initials: GG
authors.lastname: Turrigiano
mesh_terms: D000704:Analysis of Variance; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D066298:In Vitro Techniques; D008297:Male; D051783:Methyl-CpG-Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011810:Quinoxalines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D018091:Receptors, AMPA / Q000378:metabolism; D018709:Statistics, Nonparametric; D013569:Synapses / Q000235:genetics / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D014162:Transfection; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
chemical_list: D000779:Anesthetics, Local; D018691:Excitatory Amino Acid Antagonists; C497394:Mecp2 protein, rat; D051783:Methyl-CpG-Binding Protein 2; D011810:Quinoxalines; D034741:RNA, Small Interfering; D018091:Receptors, AMPA; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D013779:Tetrodotoxin; C056723:FG 9041; C104722:glutamate receptor ionotropic, AMPA 2