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Sex‐specific accelerated decay in time/activity‐dependent plasticity and associative memory in an animal model of Alzheimer's disease

ABSTRACT: In a series of slice electrophysiology experiments, we demonstrated that female APPSwe-Psen1dE9 Alzheimer's disease model mice show greater impairments in hippocampal synaptic plasticity than male mice of the same age and genotype. Female APP/PS1 mice also showed greater impairments in behavioural associative memory, higher amyloid plaque burden and increased microglial activation in the hippocampus than males at age 4-5 months. We thus profiled hippocampal mRNA from these mice to investigate the underlying molecular mechanisms. Compared to wild-type mice of the same sex, we found that female APP/PS1 mice showed a greater upregulation of microglial and inflammatory genes than males. Moreover, downregulation of genes associated with memory and plasticity was observed uniquely in female APP/PS1 mice. These data provide insight into the potential mechanisms of the greater prevalence and faster progression of AD in females.

ORGANISM(S): Mus musculus

PROVIDER: GSE186710 | GEO | 2021/10/30

REPOSITORIES: GEO

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Project description:Microglia, the brain’s principal immune cells, have been implicated in the pathogenesis of Alzheimer’s disease (AD), a condition shown to affect more females than males. Although sex differences in microglial function and transcriptomic programming have been described across development and in disease models of AD, no studies have comprehensively identified the sex divergences that emerge in the aging mouse hippocampus. Further, existing models of AD generally develop pathology (amyloid plaques and tau tangles) early in life and fail to recapitulate the aged brain environment associated with late-onset AD. Here, we examined and compared the transcriptomic and translatomic sex effects in young and old murine hippocampal microglia. Hippocampal tissue from C57BL6/N and microglial NuTRAP mice of both sexes were collected at young (5-6 month-old [mo]) and old (22-25 mo) ages. Cell sorting and affinity purification techniques were used to isolate the microglial transcriptome and translatome for RNA-sequencing and differential expression analyses. Flow cytometry, qPCR, and imaging approaches were used to confirm the transcriptomic findings. There were marginal sex differences identified in the young hippocampal microglia, with most differentially expressed genes (DEGs) restricted to the sex chromosomes. Both sex chromosomally- and autosomally-encoded sex differences emerged with aging. These sex DEGs identified at old age were primarily female-biased and enriched in senescent and disease-associated microglial signatures. Pathway analyses identified upstream regulators induced to a greater extent in females than in males, including inflammatory mediators IFNG, TNF, and IL1B, as well as AD-risk genes TREM2 and APP. These data suggest that female microglia adopt disease-associated and senescent phenotypes in the aging mouse hippocampus, even in the absence of disease pathology, to a greater extent than males. This sexually divergent microglial phenotype may explain the difference in susceptibility and disease progression in the case of AD pathology. Future studies will need to explore sex differences in microglial heterogeneity in response to AD pathology and determine how sex-specific regulators (i.e., sex chromosomal or hormonal) elicit these sex effects.

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Sex‐specific accelerated decay in time/activity‐dependent plasticity and associative memory in an animal model of Alzheimer's disease

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