1. Absorptive cells Enterocyte: nutrient absorption Secretory cells Goblet cell: mucus secretion Paneth cells: antimicrobial product secretion Enteroendocrine cells: hormone secretion Other Tuft cells M-cells Cells proposed to be derived from ISCs at the crypt base

2. Colon similar to small intestine: Similar cell types are derived from ISCs at the crypt base

3. Labeling proliferating cells and following their migration: ~5 days from birth to death

4. ISCs – Crypt base columnar (CBC) cells or +4 cells? +4 cells were proliferating, label-retaining cells: proposed to possess an immortal DNA strand maintained by asymmetric cell division CBC cells were traced to all the lineages and formed crypts when cultured ex vivo

5. Barker N. et al, Nature 449:1003, 2007 Lgr5 expression Marks CBCs Lgr5 expression restricted to CBC cells

6. Use of an Lgr5-GFP-Cre transgene to mark Lgr5-expressing cells and their descendents

7. 1 5 60 days following Cre activation Use of an Lgr5-GFP-Cre transgene to mark Lgr5-expressing cells and their descendents CBC stem cells mapping below +4

8. T Sato et al. Nature 000, 1-4 (2009) doi:10.1038/nature07935 Single Lgr5 + cells generate crypt–villus structures.

9. T Sato et al. Nature 000, 1-4 (2009) doi:10.1038/nature07935 Composition of single stem cell-derived organoids.

10. Barker N. et al, Nature 449:1003, 2007 Fun facts: Lgr5 ISCs do not undergo asymmetric division – they divide symmetrically, producing either 2 TA cells or 2 ISCs. No evidence of an immortal DNA strand in Lgr5 ISCs obtained

11. An Lgr5-Diptheria toxin receptor fusion gene can trigger the elimination of Lgr5-expressing cells Tian et al. Nature 2011

12. Crypts develop normally even when Lgr5 cells depleted Tian et al. Nature 2011

13. Bmi1-positive “+4 ISCs” expand when Lgr5 cells depleted

14. Lineage tracing shows Bmi1 cells contribute cells to the crypt and this contribution increases when Lgr5 cells are eliminated

15. Are there two ISC populations?

16. How many cells can serve as stem cells in the injured tissue?

17. Contribution of epithelial cells to IBD