Hersh, Samuel

Abstract We have previously reported the therapeutic effect of depletion and regeneration of endogenous microglia on autism spectrum disorder-like behaviors in offspring from the dams under maternal immune activation (MIA) by dampening their neuritogenic activation. Here we show a long-lasting pathological effect by MIA, leading to abnormal behaviors in offspring mice in a sex-specific manner at 3 months of age. MIA was induced by injecting Polyinosinic:polycytidylic acid [Poly(I:C)] at 10mg/kg at E9.5 with preselected dams based on the immunoreactivity to low-dose Poly(I:C) injection. MIA offspring show impairments in sociability, repetitive behavior, and spatial working and associative memories in both sexes, whereas only male offspring show social novelty deficit. MIA has no effect on anxiety-like behavior nor sensori-motor or locomotor activity. Administering colony stimulating factor receptor (CSF1R) inhibitor in young adult MIA offspring regenerates microglia and ameliorates sociability deficits in males and spatial working and associative memory impairments in both sexes without effect on social novelty impairments. Transcriptomic analysis of prefrontal cortex and hippocampal tissues reveals MIA and sex-specific pathways and highlights potential key genes involved in the corrective effect of microglial regeneration in MIA offspring. Our results underscore the potential of the sex-specific therapeutic applications of CSF1R inhibitor for MIA-related social and cognitive disorders.

AbstractBackgroundMicroglia, the resident brain immune cells, play a critical role in brain homeostasis and disease progression. In neurodegenerative conditions, microglia acquire the neurodegenerative phenotype (MGnD), whose function is poorly understood. MicroRNA‐155 (miR‐155), enriched in immune cells, critically regulates MGnD. However, its role in Alzheimer’s disease (AD) pathogenesis remains unclear.MethodsWe used RNAseq and immunohistochemistry (n = 6‐8 per sex per group) to investigate the gene expression profile and AD pathology. We further utilized single‐cell RNAseq (n = 5 per group) to identify microglial clusters. Whole‐tissue proteomics (n = 4) was applied to detect the protein changes in brain milieu. Moreover, we used spontaneous alternation and forced alternation tests to evaluate the cognition (n = 33‐36).ResultWe report that microglial deletion of miR‐155 induces a pre‐MGnD activation state via interferon‐g (IFNg) signaling and blocking IFNg signaling attenuates MGnD induction and microglial phagocytosis. Single‐cell RNAseq analysis of microglia from AD mouse model identifies Stat1 and Clec2d as pre‐MGnD markers. This phenotypic transition enhances amyloid plaque compaction, reduces dystrophic neurites, attenuates plaque‐associated synaptic degradation, and improves cognition.ConclusionOur study demonstrates a novel miR‐155‐mediated regulatory mechanism of MGnD and the beneficial role of IFNg‐responsive pre‐MGnD in restricting neurodegenerative pathology and preserving cognitive function in an AD mouse model, highlighting miR‐155 and IFNg as potential therapeutic targets for AD.

AbstractAlzheimer's disease (AD) is a pervasive neurodegeneration disease with high heritability. In this study, we employed CRISPR‐Cas9‐engineered technology to investigate the effects of a rare mutation (rs144662445) in the A kinase anchoring protein 9 (AKAP9) gene, which is associated with AD in African Americans (AA), on tau pathology and the tau interactome in SH‐SY5Y P301L neuron‐like cells. The mutation significantly increased the level of phosphorylated tau, specifically at the site Ser396/Ser404. Moreover, analyses of the tau interactome measured by affinity purification‐mass spectrometry revealed that differentially expressed tau‐interacting proteins in AKAP9 mutant cells were associated with RNA translation, RNA localization and oxidative activity, recapitulating the tau interactome signature previously reported with human AD brain samples. Importantly, these results were further validated by functional studies showing a significant reduction in protein synthesis activity and excessive oxidative stress in AKAP9 mutant compared with wild type cells in a tau‐dependent manner, which are mirrored with pathological phenotype frequently seen in AD. Our results demonstrated specific effects of rs14462445 on mis‐processing of tau and suggest a potential role of AKAP9 in AD pathogenesis.

AbstractBackgroundAlzheimer’s disease (AD) is a pervasive neurodegeneration disease with high heritability. Whole exome sequencing study identified two rare African American (AA)‐specific variants in AKAP9, a kinase anchor protein 9, (rs144662445 and rs149979685), that increased the odds of AD more than 2.75‐fold. However, the functional impact of the AKAP9 rs144662445 (I2558M) mutation in the central nervous system and the underlying mechanism in AD remain unclear.MethodAKAP9 I2558M mutation was introduced by CRISPR‐mediated knock‐in and validated by Sanger sequence in SH‐SY5Y cells stably expressing P301L Tau (SH‐SY5Y P301L cells), which was further differentiated into neuronal cells. Tau phosphorylated level between AKAP9 WT and I2558M cells was evaluated by immunocytochemistry and ELISA assay. Moreover, we analyzed the tau interactome in AKAP9 I2558M cells by affinity purification‐mass spectrometry. In silico analysis was performed to compare the differences between AKAP9 WT and mutation in tau‐interacting proteins. The protein synthesis and oxidative activity in SH‐SY5Y P301L neurons with and without I2558M were measured by using the Click‐iT protein synthesis kit and CellRox dye, respectively.ResultNo difference in the neuronal cell morphology was observed between differentiated WT and mutant SH‐SY5Y P301L cells. The AD‐associated AKAP9 I2558M mutation resulted in a significant increase in phosphorylated tau protein at residues S396 and S404 site in a differentiated SH‐SY5Y P301L cell line. The presence of this mutation altered the composition of tau‐interacting proteins, by increasing interaction of proteins associated with translation, RNA localization and oxidative activity. Importantly, functional studies showed a significant reduction in protein synthesis activity and excessive oxidative stress in AKAP9 mutant compared to wild type cells.ConclusionOur results demonstrated specific effects of rs14462445 on mis‐processing of tau and suggest a potential role of AKAP9 in AD pathogenesis.