Gerbe et al. define a new type of secretory cell in the intestine.
The intestinal epithelium consists of four main specialized cell lineages: absorptive enterocytes and three secretory cell types known as enteroendocrine, Paneth, and goblet cells. But a rare, fifth type of intestinal cell called tuft cells also exists. Defined by the thick brush of long microvilli that project from their apical surface, tuft cells are seen in several epithelial tissues, yet little is known about their function due to a lack of tuft cell–specific markers.
Gerbe et al. identified several proteins uniquely expressed by tuft cells, including DCLK1, a kinase that was previously thought to mark a population of quiescent intestinal stem cells. Like other intestinal cell types, tuft cells turned over rapidly and were replaced by the differentiation of proliferative stem cells' progeny in the intestinal crypts. This differentiation was blocked in the absence of ATOH1—a transcription factor required for the development of all intestinal secretory lineages. Yet tuft cell differentiation didn't require other transcription factors that specify enteroendocrine, Paneth, and goblet cells, suggesting that tuft cells represent a distinct lineage of intestinal secretory cells.
Gerbe et al. found that tuft cells secrete opioids and produce enzymes that synthesize prostaglandins. The latter observation suggests that tuft cells may promote inflammation and tumorigenesis. Indeed, the researchers identified tuft cell–like cells in several early stage intestinal tumors. To really understand tuft cells' function, however, author Philippe Jay hopes to identify transcription factors uniquely required for their development in order to generate mice that specifically lack tuft cells from their intestinal epithelium.