Fig. 3: Ceramides and related sphingolipids in extracts from the spleens and livers of 21-week-old P361R-SMA mice.

a Summary of a portion of sphingolipid metabolic pathways with gene names for select enzymes. Corresponding enzyme names are listed below. Shorthand notation for some sphingolipid families are also shown. Arrows show potential for interconversion. Note that reverse activity of ceramidases utilizing sphingosine has only been shown in vitro. b–k Levels of the indicated sphingolipids were measured in spleen homogenates by mass spectrometry. Ceramide data is highlighted with red bars. Total levels were calculated by adding up molar amounts of individually measured acyl-chain variants. Values for individual mice are shown as dots (wild-type (WT), n = 11 mice; P361R-SMA, n = 10 mice), sex is differentiated using different colors (blue for male and red for female), bars throughout represent the mean and error bars show standard error of the mean. Total levels were compared using a Welch’s t test, ***p < 0.001, **p < 0.01 and *p < 0.05. Sphingosine [d20:1], sphingosine-1-phosphate, and sulfatides were not detected. l Heatmap of the relative abundance in spleen extracts of selected acyl-chain variants of the indicated sphingolipid families. Data were compared using a two-way analysis of variance with Šidák’s multiple comparison test; statistically significant (p < 0.05) differences are indicated with a red outline. m–v Sphingolipid levels, as specified, were assessed in liver homogenates. Data is presented and compared as described for (b–k). w Relative abundance of select acyl-chain variants of the specified sphingolipid families in liver extracts were calculated and are displayed as a heatmap. Data was compared, and statistical significance displayed, as described for (l). The gene names in (a) correspond to the following enzymes: CERS1-6 ceramide synthases 1 through 6, DEGS1/2 dihydroceramide desaturase 1 and 2, ASAH1 acid ceramidase, ASAH2 neutral ceramidase, ACER1-3 alkaline ceramidases 1 through 3, GBA β-glucocerebrosidase, GALC galactosylceramidase, SPMD1 acid sphingomyelinase, CERK ceramide kinase, SPHK1/2 sphingosine kinase 1 and 2, ARSA arylsulfatase A, GLA α-galactosidase A.