Live-Cell Imaging in Human Colonic Monolayers Reveals Erk Waves Limit the Stem Cell Compartment to Maintain Epithelial Homeostasis

Abstract

The establishment and maintenance of different cellular compartments in tissues is a universal requirement across all metazoans. Maintaining the correct ratio of cell types in time and space allows tissues to form patterned compartments and perform complex functions. Patterning is especially evident in the human colon, where tissue homeostasis is maintained by stem cells in crypt structures that balance proliferation and differentiation. Here we developed a 2D patient derived organoid (PDO) screening platform to study tissue patterning and kinase pathway dynamics in single cells across hundreds of conditions. Using this system, we discovered that waves of Erk signaling induced by apoptotic cells play a critical role in maintaining tissue patterning and homeostasis. If Erk is activated acutely across all cells instead of in wavelike patterns, then tissue patterning, and stem cell maintenance are lost. Conversely, if Erk activity is inhibited, then stem cells become unrestricted and expand dramatically. This work demonstrates that the colonic epithelium requires coordinated Erk signaling dynamics to maintain patterning and tissue homeostasis. Our work reveals how Erk can antagonize stem cells yet support cell replacement and the function of the gut.