FMRP cooperates with miRISC components to repress translation and regulate neurite morphogenesis in Drosophila.

Fragile X Syndrome (FXS) is the most common inherited form of intellectual disability and is caused by mutations in the gene encoding the Fragile X messenger ribonucleoprotein (FMRP). FMRP is an evolutionarily conserved and neuronally enriched RNA-binding protein (RBP) with functions in RNA editing, RNA transport, and protein translation. Specific target RNAs play critical roles in neurodevelopment, including the regulation of neurite morphogenesis, synaptic plasticity, and cognitive function. The different biological functions of FMRP are modulated by its cooperative interaction with distinct sets of neuronal RNA and protein-binding partners. Here, we focus on interactions between FMRP and components of the microRNA (miRNA) pathway. Using the Drosophila S2 cell model system, we show that the Drosophila ortholog of FMRP (dFMRP) can repress translation when directly tethered to a reporter mRNA. This repression requires the activity of AGO1, GW182, and MOV10/Armitage, conserved proteins associated with the miRNA-containing RNA-induced silencing complex (miRISC). Additionally, we find that untagged dFMRP can interact with a short stem-loop sequence in the translational reporter, a prerequisite for repression by exogenous miR-958. Finally, we demonstrate that dFmr1 interacts genetically with GW182 to control neurite morphogenesis. These data suggest that dFMRP may recruit the miRISC to nearby miRNA binding sites and repress translation via its cooperative interactions with evolutionarily conserved components of the miRNA pathway.

Breast Implant-Associated Anaplastic Large Cell Lymphoma Awareness: An Analysis of the Responses to an Institutional Campaign and Global Recall.

BACKGROUND: We performed an assessment of patient response rates and clinical outcomes to the global recall for textured breast implants and to our institution's letters informing them of their risk of breast implant-associated anaplastic large cell lymphoma (BIA-ALCL). METHODS: A retrospective review of patients who had textured implants placed at our institution was completed. Outcome measures included patient response rates to either the global recall or our institution's letters, rate of textured implant removal, and type of subsequent revision surgery. RESULTS: A total of 1176 patients with textured implants were reviewed for this study. In total, 374 patients (31.8%) reached out to discuss their risk of BIA-ALCL, and 297 (25.3%) eventually presented to the clinic. One hundred twenty eight patients (34.2%) responded after the letter but before the US Food and Drug Administration (FDA) ban of macrotextured BIOCELL implants, 186 (49.7%) after the FDA ban, and 48 (12.8%) after the manufacturer's multichannel campaign. One hundred eighteen patients with textured implants (11.6%) proceeded with surgery. Most underwent exchange with smooth implants (76 patients [64.4%]) after textured implant removal. CONCLUSIONS: A significant portion of patients (31.8%) responded to our letters, the FDA ban, and the manufacturer's campaign. Despite the low incidence of BIA-ALCL and the ongoing recommendation for observation in the setting of no symptoms, 11.6% of our patients still elected to proceed with implant removal. Exchange to smooth implants was the most popular surgical option at 64.4%.

Amnestic drugs in the odor span task: Effects of flunitrazepam, zolpidem and scopolamine.

The odor span task is an incrementing non-matching-to-sample procedure designed to provide an analysis of working memory capacity in rodents. The procedure takes place in an arena apparatus and rats are exposed to a series of odor stimuli in the form of scented lids with the selection of new stimuli reinforced. This procedure makes it possible to study drug effects as a function of the number of stimuli to remember. In the present study, the non-selective positive allosteric GABAA receptor modulator flunitrazepam impaired odor span performance at doses that did not affect a control odor discrimination. In contrast, the alpha-1 selective positive GABAA receptor modulator zolpidem and the cholinergic receptor antagonist scopolamine only impaired odor span at doses that produced more global impairment, including decreased accuracy in the control discrimination and increased response omissions in the both the odor span and control discrimination procedures. Even though the effects of flunitrazepam were selective to odor span performance, they did not depend on the number of stimuli to remember-the same degree of impairment occurred regardless of the memory load. These findings suggest that flunitrazepam interfered selectively with conditional discrimination performance rather than working memory and tentatively suggest that flunitrazepam's selective effects in the odor span task relative to the control odor discrimination are mediated by one or more non-alpha1 GABAA receptor subtypes.

Repeated reversals of concurrent olfactory discriminations in rats: A search for functional equivalence.

Equivalence class formation has been difficult to demonstrate in nonhumans, but one method that has been successful is a simple discrimination procedure in which contingencies associated with two sets of arbitrary discriminative stimuli are repeatedly reversed. Pigeons and sea lions shift responding after encountering the newly-reversed contingency with only a few set members, showing evidence of functional equivalence. We used this strategy to determine whether similar findings would occur in rats using olfactory stimuli. Rats were trained to nose-poke in the presence of six stimuli arbitrarily designated as members of the positive set; responses to the six members of the negative set were not reinforced. When discriminative performance was established, contingencies associated with each set were reversed and re-reversed each time subjects met a performance criterion. All subjects successfully acquired the concurrent simple discriminations and were exposed to between 12 and 60 reversals, but none showed clear evidence of functional class formation until a final procedure in which the stimulus sets that had been in place were arbitrarily rearranged. Acquisition with these new stimulus sets was impaired, showing that class membership generated by the original stimulus sets interfered with learning the new ones, thus providing evidence of functional equivalence.

Successive incrementing non-matching-to-samples in rats: An automated version of the odor span task.

The odor span task is a procedure frequently used to study remembering of multiple stimuli in rodents. A large arena is used and odor stimuli are presented using scented cups. Selection of each odor is reinforced when first presented, but not on subsequent presentations; correct selections depend on remembering which stimuli were previously presented. The use of an arena setting with manual stimulus presentation makes the odor span task labor-intensive and limits experimental control; thus, an automated version of the task would be of value. The present study used an operant chamber equipped with an olfactometer and trained rats using successive conditional discrimination procedures under an incrementing non-matching-to-samples contingency. High rates of responding developed to odor stimuli when they were session-novel with low rates of responding to subsequent presentations of that odor. Additional experiments assessed variations of the procedure to determine the role of the frequency of odor presentation and the retention interval separating sample and comparison. Discrimination was impaired with long retention intervals suggesting the importance of this variable. These findings confirmed that rats differentiate between stimuli that are session-novel and those previously encountered and support the use of an automated procedure as an alternative to the odor span task.