Fig. 2.

Spatial cross-correlation heatmaps. x- and y-axes are the same and represent a selection of 70 m/z values (supplemental Table S3), classified by lipid class. Per lipid class, the lipids are sorted from low to high m/z value. A:. Average heatmap of all 106 tissue sections, showing a correlation within lipid classes and showing a moderate correlation between LPCs, PCs, and SMs and also between DGs and TGs. B:. Individual heatmaps of the six representative sections shown in Fig. 1. Heatmaps of sections 1 and 3 show moderate positive correlation between PC and SM lipids, whereas section 2 shows a negative between these lipids. CE, cholesterol ester; DG, diacylglycerol; LPC, lysophosphatidylcholine; PC, phosphatidylcholines; SM, sphingomyelin; TG, triacylglycerol.