Sphingomyelin localization in the intestinal crypt surface.

Macroscopic lipid observation in the organs of living small animals has not been realized. Here, we visualized sphingomyelin (SM) in the intestines of living mice using an SM-binding protein (EqtII-EGFP-His) under two-photon microscopy. The SM was identified as 10 μm spots in glands of the lamina propria of the mucosa in the large and small intestines. The spots vertically penetrated from the serosa toward the mucosal side. At the edge of the mucosal side in the small intestine, these spots connected with each other and formed horizontal lines. For the large intestine, the horizontal lines became a surface, indicating that SM covered the whole crypt membrane. Detailed observation revealed thin SM-positive lines that connected the spots and the blood vessels in the small intestine. Thus, SM exists at crypt surfaces and inside crypts of the intestines and can regulate the functions of the digestion system.