Organization of a cytoskeletal superstructure in the apical domain of intestinal tuft cells.

Tuft cells are a rare epithelial cell type that play important roles in sensing and responding to luminal antigens. A defining morphological feature of this lineage is the actin-rich apical "tuft," which contains large fingerlike protrusions. However, details of the cytoskeletal ultrastructure underpinning the tuft, the molecules involved in building this structure, or how it supports tuft cell biology remain unclear. In the context of the small intestine, we found that tuft cell protrusions are supported by long-core bundles that consist of F-actin crosslinked in a parallel and polarized configuration; they also contain a tuft cell-specific complement of actin-binding proteins that exhibit regionalized localization along the bundle axis. Remarkably, in the sub-apical cytoplasm, the array of core actin bundles interdigitates and co-aligns with a highly ordered network of microtubules. The resulting cytoskeletal superstructure is well positioned to support subcellular transport and, in turn, the dynamic sensing functions of the tuft cell that are critical for intestinal homeostasis.