Doll CA, Broadie K. Neuron class-specific requirements for Fragile X Mental Retardation Protein in critical period development of calcium signaling in learning and memory circuitry. Neurobiol Dis. 2016 May;89:76-87. PMID: 26851502; PMCID: PMC4785039.
From the abstract: "... Fragile X Mental Retardation Protein (FMRP), the gene product lost in Fragile X syndrome (FXS), acts as an activity sensor during critical period development, both as an RNA-binding translation regulator and channel-binding excitability regulator. Here, we employ a Drosophila FXS disease model to assay calcium signaling dynamics with a targeted transgenic GCaMP reporter during critical period development of the mushroom body (MB) learning/memory circuit. We find FMRP regulates depolarization-induced calcium signaling in a neuron-specific manner within this circuit, suppressing activity-dependent calcium transients in excitatory cholinergic MB input projection neurons and enhancing calcium signals in inhibitory GABAergic MB output neurons. ... These results show FMRP shapes neuron class-specific calcium signaling in excitatory vs. inhibitory neurons in developing learning/memory circuitry, and that FMRP mediates activity-dependent regulation of calcium signaling specifically during the early-use critical period."
Doll CA, Broadie K. Activity-dependent FMRP requirements in development of the neural circuitry of learning and memory. Development. 2015 Apr 1;142(7):1346-56. PMID: 25804740; PMCID: PMC4378248.
From the abstract: "... Here, we use optogenetic tools in the Drosophila FXS disease model to test activity-dependent dendritogenesis in two extrinsic neurons of the mushroom body (MB) learning and memory brain center: (1) the input projection neuron (PN) innervating Kenyon cells (KCs) in the MB calyx microglomeruli and (2) the output MVP2 neuron innervated by KCs in the MB peduncle. Both input and output neuron classes exhibit distinctive activity-dependent critical period dendritic remodeling. MVP2 arbors expand in Drosophila mutants null for fragile X mental retardation 1 (dfmr1), as well as following channelrhodopsin-driven depolarization during critical period development, but are reduced by halorhodopsin-driven hyperpolarization. ... results show that dfmr1 acts in a neuron type-specific activity-dependent manner for sculpting dendritic arbors during early-use, critical period development of learning and memory circuitry in the Drosophila brain."