GRN and Gliosis: Specifically, PGRN deficiency in the FVB mouse strain leads to an earlier onset and more pronounced phenotypes, including gliosis, lysosomal defects, and TDP-43 pathology, as well as more significant alterations of gene and protein expression, compared to the B6 mouse strain (Fig. 1-Figs. 5 and 10, and Fig. 11).