Figure 4.

Serotonin staining is decreased in aged Ubqln2^−/−tissues. A, GO-term enrichment analysis was performed on brains, hippocampus, and lumbar spinal cords from aged and young mice (from Fig. 2) to identify pathways that were altered upon Ubqln2 loss. Color corresponds to the significance of pathway enrichment as measured by the -log₁₀(adjusted p-value) and is either red, for pathways enriched upon Ubqln2 loss (Up in KO), or blue, for pathways downregulated upon Ubqln2 loss (Up in WT). Notable significantly enriched pathways were selected from Table S5 for graphic representation. B, GO-term enrichment of brain hemispheres from aged WT and Ubqln2^−/− animals (shown as KO) reveals a decrease in expression of proteins involved in neurotransmitter signaling. Nine significantly altered proteins from the Molecular Function (MF) GO-term:0005326 neurotransmitter transporter activity were highlighted to demonstrate differences between WT and Ubqln2^−/− counterparts. Color represents protein abundance as measured by mass spectrometry, scaled independently for each protein. C, lumbar spinal cords from approximately 1-year-old animals were prepared for histological quantitation of serotonin-positive neuronal projections via serotonin staining. Shown are representative images of spinal cord cross section (left) and zoomed in area (right) highlighting neuronal projections. The scale bar represents 100 μm. D, quantification of serotonin positivity as a proportion of area from (C) using thresholding. n=8 to 9 animals. E, coronal sections of brains from young animals were prepared for histological quantitation of serotonin-positive neuronal projections. The scale bar represents 1 mm. F, quantification of serotonin positivity as a proportion of area using thresholding to determine serotonin positivity. n = 7 animals. Statistical significance for (D and F) was determined using an unpaired, two-tailed Student's t test. BP, Biological Process; CC, Cellular Component.