The Smarcal1-Usp37 locus modulates glycogen aggregation in astrocytes of the aged hippocampus

In aged humans and mice, hypobranched glycogen aggregates, known as polyglucosan bodies (PGBs), accumulate in hippocampal astrocytes. While PGBs are linked to cognitive decline in neurological diseases, they remain largely unstudied in the context of typical aging. We show that PGBs arise in autophagy-dysregulated astrocytes in the aged hippocampus, with substantial variation among 32 inbred BXD mouse strains. Genetic mapping through quantitative trait locus analysis identified a major locus (Pgb1) that modulates hippocampal PGB burden. Extensive transcriptomic and proteomic datasets were produced for the aged hippocampus of the BXD family to investigate the mechanism by which the Pgb1 locus modulates PGB burden. We identified that Pgb1 contains allelic Smarcal1 and Usp37 variants and influences PGB burden through trans-regulation of mRNA and protein expression levels, including abundance of glycogen-mobilizing factor PYGB. Furthermore, comprehensive phenome-wide association scans, transcriptomic analyses, and direct behavioral testing demonstrated that cognition remains intact despite age-related PGB burden. A record of this paper's transparent peer review process is included in the supplemental information.