Specific Labeling of Stem Cell Activity in Human Colorectal Organoids Using an ASCL2-Responsive Minigene.

Organoid technology provides the possibility of culturing patient-derived colon tissue and colorectal cancers (CRCs) while maintaining all functional and phenotypic characteristics. Labeling stem cells, especially in normal and benign tumor organoids of human colon, is challenging and therefore limits maximal exploitation of organoid libraries for human stem cell research. Here, we developed STAR (stem cell Ascl2 reporter), a minimal enhancer/promoter element that reports transcriptional activity of ASCL2, a master regulator of LGR5+ intestinal stem cells. Using lentiviral infection, STAR drives specific expression in stem cells of normal organoids and in multiple engineered and patient-derived CRC organoids of different genetic makeup. STAR reveals that differentiation hierarchies and the potential for cell fate plasticity are present at all stages of human CRC development. Organoid technology, in combination with the user-friendly nature of STAR, will facilitate basic research into human adult stem cell biology.