Intranasal siRNA administration reveals IGF2 deficiency contributes to impaired cognition in Fragile X syndrome mice
Marta Pardo, … , Richard S. Jope, Eleonore Beurel
Marta Pardo, … , Richard S. Jope, Eleonore Beurel
Published March 23, 2017
Citation Information: JCI Insight. 2017;2(6):e91782. https://doi.org/10.1172/jci.insight.91782.
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Research Article Neuroscience

Intranasal siRNA administration reveals IGF2 deficiency contributes to impaired cognition in Fragile X syndrome mice

Abstract

Molecular mechanisms underlying learning and memory remain imprecisely understood, and restorative interventions are lacking. We report that intranasal administration of siRNAs can be used to identify targets important in cognitive processes and to improve genetically impaired learning and memory. In mice modeling the intellectual deficiency of Fragile X syndrome, intranasally administered siRNA targeting glycogen synthase kinase-3β (GSK3β), histone deacetylase-1 (HDAC1), HDAC2, or HDAC3 diminished cognitive impairments. In WT mice, intranasally administered brain-derived neurotrophic factor (BDNF) siRNA or HDAC4 siRNA impaired learning and memory, which was partially due to reduced insulin-like growth factor-2 (IGF2) levels because the BDNF siRNA– or HDAC4 siRNA–induced cognitive impairments were ameliorated by intranasal IGF2 administration. In Fmr1–/– mice, hippocampal IGF2 was deficient, and learning and memory impairments were ameliorated by IGF2 intranasal administration. Therefore intranasal siRNA administration is an effective means to identify mechanisms regulating cognition and to modulate therapeutic targets.

Authors

Marta Pardo, Yuyan Cheng, Dmitry Velmeshev, Marco Magistri, Hagit Eldar-Finkelman, Ana Martinez, Mohammad A. Faghihi, Richard S. Jope, Eleonore Beurel

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Figure 1

Intranasal treatment with L803-mts or glycogen synthase kinase-3β (GSK3β) siRNA alleviates cognitive impairments in Fmr1–/– mice.

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Intranasal treatment with L803-mts or glycogen synthase kinase-3β (GSK3β...
Mice were treated intranasally with the GSK3 inhibitor L803-mts or with GSK3β siRNA followed by 4 measures of learning and memory (novel object recognition, temporal ordering, and coordinate and categorical spatial processing) to test if cognition was improved in Fmr1–/– mice, which model Fragile X syndrome and are known to display cognitive impairments, or if cognition was affected in WT mice. WT and Fmr1–/– mice received (A–D) intranasal vehicle (Veh) or L803-mts (L803; 60 μg/mouse), or (E–H) intranasal scrambled siRNA (S) or 2 different sequences of GSK3β siRNA (B1, sequence 1, or B2, sequence 2; 10 μg/mouse/day) daily for 3 consecutive days prior to testing and daily throughout the behavioral testing. Discrimination index is shown for (A) novel object recognition (n = 8–14; F(3,39) = 6.49, P < 0.01) (**P < 0.01 compared with vehicle-treated WT mice; *P < 0.01 compared with vehicle-treated Fmr1–/– mice) and (B) temporal ordering (n = 8–14; F(3,39) = 5.87, P < 0.01) (**P < 0.01 compared with vehicle-treated WT mice; *P < 0.05 compared with vehicle-treated Fmr1–/– mice). Exploration ratio is shown for (C) coordinate spatial processing (n = 8–14; F(3,39) = 9.07, P < 0.01) (**P < 0.01 compared with vehicle-treated WT mice; *P < 0.01 compared with vehicle-treated Fmr1–/– mice) and (D) categorical spatial processing (n = 8–14; F(3,39) = 7.38, P < 0.01) (**P < 0.01 compared with vehicle-treated WT mice; *P < 0.01 compared with vehicle-treated Fmr1–/– mice). Discrimination index is shown for (E) novel object recognition (n = 7–9; F(5,52) = 4.34, P < 0.01) (**P < 0.01 compared with scrambled siRNA–treated WT mice; *P < 0.01 compared with scrambled siRNA–treated Fmr1–/– mice) and (F) temporal ordering (n = 7–9; F(5,51) = 3.51, P < 0.01) (**P < 0.01 compared with scrambled siRNA–treated WT mice; *P < 0.05 compared with scrambled siRNA–treated Fmr1–/– mice). Exploration ratio is shown for (G) coordinate spatial processing (n = 7–9; F(5,52) = 5.42, P < 0.01) (**P < 0.01 compared with scrambled siRNA–treated WT mice; *P < 0.01 compared with scrambled siRNA–treated Fmr1–/– mice) and (H) categorical spatial processing (n = 7–9; F(5,52) = 3.89, P < 0.01) (**P < 0.01 compared with scrambled siRNA–treated WT mice; *P < 0.01 compared with scrambled siRNA–treated Fmr1–/– mice). One-way ANOVA (genotype × treatment) for each behavioral test followed by post hoc Dunnett’s multiple comparison test. (I) Mice received intranasally scrambled siRNA coupled or not to fluorescein (FAM), and 24 hours after injection, mean fluorescence intensity (MFI) was measured in the hippocampus and the cerebellum. *P < 0.05 (Student’s t test). Each symbol represents the value from an individual mouse. Values are means ± SEM.