Intestinal stem and progenitor cells replicate and differentiate in distinct compartments, influenced by Wnt, BMP, and other sub-epithelial cues. The cellular sources of these signals were long obscure because intestinal mesenchyme was insufficiently characterized. In this Review, we discuss how recent mRNA profiles of mouse and human intestinal sub-mucosa, coupled with fine-resolution microscopy and gene and cell disruptions, reveal a coherent picture of an organized tissue carrying cells with distinct molecular properties and functions.
