title: Homeostatic responses fail to correct defective amygdala inhibitory circuit maturation in fragile X syndrome.
abstract: Fragile X syndrome (FXS) is a debilitating neurodevelopmental disorder thought to arise from disrupted synaptic communication in several key brain regions, including the amygdala, a central processing center for information with emotional and social relevance. Recent studies reveal defects in both excitatory and inhibitory neurotransmission in mature amygdala circuits in Fmr1(-/y) mutants, the animal model of FXS. However, whether these defects are the result of altered synaptic development or simply faulty mature circuits remains unknown. Using a combination of electrophysiological and genetic approaches, we show the development of both presynaptic and postsynaptic components of inhibitory neurotransmission in the FXS amygdala is dynamically altered during critical stages of neural circuit formation. Surprisingly, we observe that there is a homeostatic correction of defective inhibition, which, despite transiently restoring inhibitory synaptic efficacy to levels at or beyond those of control, ultimately fails to be maintained. Using inhibitory interneuron-specific conditional knock-out and rescue mice, we further reveal that fragile X mental retardation protein function in amygdala inhibitory microcircuits can be segregated into distinct presynaptic and postsynaptic components. Collectively, these studies reveal a previously unrecognized complexity of disrupted neuronal development in FXS and therefore have direct implications for establishing novel temporal and region-specific targeted therapies to ameliorate core amygdala-based behavioral symptoms.
authors.affiliation: Center for Neuroscience Research, Children's National Medical Center, Washington, DC 20010, USA.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Vislay
authors.forename: Brandon S
authors.initials: BS
authors.lastname: Martin
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Olmos-Serrano
authors.forename: Sebila
authors.initials: S
authors.lastname: Kratovac
authors.forename: David L
authors.initials: DL
authors.lastname: Nelson
authors.forename: Joshua G
authors.initials: JG
authors.lastname: Corbin
authors.forename: Molly M
authors.initials: MM
authors.lastname: Huntsman
mesh_terms: D000679:Amygdala / Q000473:pathology*; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D004195:Disease Models, Animal; D005600:Fragile X Syndrome / Q000235:genetics* / Q000503:physiopathology*; D006706:Homeostasis / Q000235:genetics*; D053444:Inhibitory Postsynaptic Potentials / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009415:Nerve Net / Q000502:physiology*; D009433:Neural Inhibition / Q000235:genetics*; D009924:Organ Culture Techniques