Elevated protein synthesis in microglia causes autism-like synaptic and behavioral aberrations

Mutations that inactivate negative translation regulators cause autism spectrum disorders (ASD), which predominantly affect males and exhibit social interaction and communication deficits and repetitive behaviors. However, the cells that cause ASD through elevated protein synthesis resulting from these mutations remain unknown. Here we employ conditional overexpression of translation initiation factor eIF4E to increase protein synthesis in specific brain cells. We show that exaggerated translation in microglia, but not neurons or astrocytes, leads to autism-like behaviors in male mice. Although microglial eIF4E overexpression elevates translation in both sexes, it only increases microglial density and size in males, accompanied by microglial shift from homeostatic to a functional state with enhanced phagocytic capacity but reduced motility and synapse engulfment. Consequently, cortical neurons in the mice have higher synapse density, neuroligins, and excitation-to-inhibition ratio compared to control mice. We propose that functional perturbation of male microglia is an important cause for sex-biased ASD.


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Baoji Xu
Feb 25, 2020 Image Studio Lite Ver 4.0 (Western blot); EthoVision XT (Behavior); NIS-Elements Confocal v4.6(Immunoflourescence); pCLAMP 10 (Electrophysiology) Image Studio Lite Ver 4.0 (Western blot); Stereo Investigator 10 (cell counting), Amira 6.0 (3D microglial reconstruction and microglia engulfment); NIS-Elements Advanced Research v4.6(Immunoflourescence); EthoVision XT (Behavior); Image J version 1.52h and Fiji version 1.52i plugins TrakEM2 software (SB-SEM); RStudio Version 1. Exclusion criteria for experimental data points were pre-determined as follows. For electrophysiology, only neurons with Ra < 25 M# were recorded. For serial block-face scanning electron microscopy experiment, we avoided all dendritic segments with few or no spines (so that our analysis was restricted to pyramidal neurons). Outliers for behavioral testings were identified as being greater than two and a half standard deviations from the mean and excluded from statistical analysis. One mouse with stereotaxic injection of FAM-A" was excluded due to no A" aggregates were found in the hippocampus.
Multiple mice (n) were used for every experiment. All data in this study were collected from more than 3 independent experiments, and were reliably reproduced.
For behavioral tests, mice were chosen based on genotypes. For microglial and neuronal morphology studies, cells from each mouse were randomly selected.
Wherever possible (i.e. with the exception of Western Blotting experiments, where samples were grouped by genotypes), analyses were performed by blinded observers and/or software-automated analyses.