The intestinal tuft cell nanostructure in 3D.

Once referred to as "peculiar," tuft cells are enigmatic epithelial cells. Here, we reasoned that future functional studies could be derived from a complete account of the tuft cell ultrastructure. We identified and documented the volumetric ultrastructure at nanometer resolution (4-5 nm/pixel) of specific intestinal tuft cells. The techniques used were Serial Block-Face (SBF) and Automated Tape-collecting Ultra-Microtome (ATUM) Scanning Electron Microscopy (SEM). Our results exposed a short (15 µm) basal cytoplasmic process devoid of secretory vesicles. Volume rendering of serial sections unveiled several thin cytospinules (1 µm). These cytospinules project from the tuft cell into the nuclei of neighboring epithelial cells. Volume rendering also revealed within the tuft cell an elegant network of interconnected tubules. The network forms a passage from the base of the microvilli to the rough endoplasmic reticulum. Based on their location and microanatomy, the tuft cells' cytospinules, and tubular network, might facilitate the exchange of molecular cargo with nuclei of neighboring cells, and the gut lumen.