1. Chromatin remodelling ATPase Brg-1 is an essential factor for the maintenance of the intestinal crypt stem cell and adenoma formation
Aliaksei Holik

2. BRG-1 and cancer
BRG-1 mutations are found in human cancer cell lines and in primary cancers
Heterozygous deletion of Brg-1 in mice promotes tumourigenesis via Brg-1 haploinsufficiency
Restoration of BRG-1 function leads to the reversion of a cancer phenotype

3. Suggested mechanisms of BRG1 role in tumourigenesis
p53
BRCA1
RB/p21
BRG-1
c-Fos
Wnt-pathway

4. Wnt pathway
Willert K., Jones K. A. Genes Dev. 2006;20:

5. Small intestine architecture
Villus
Transit amplifying cells
Crypt
Stem cell

6. Generation of conditional knock-out using Cre-loxP techniques
loxP strategy

7. Brg-1-deficient cells in small intestine are repopulated with wild-type cells
AhCre-ERT
BRG-1
Day 3
Day 5
Day 7

8. Brg-1-deficient small intestinal epithelium appears to be normal at day 4 post induction
Control
BRG-1
Brg1fl/fl
VillinCre-ERT

9. Brg1-deficient small intestinal epithelium displays no difference in mitosis and apoptosis levels
VillinCre-Brg1fl/fl
VillinCre+Brg1fl/fl
p-values:
Mitosis – 0.629
Apoptosis – 0.057

10. Brg1-deficient small intestinal epithelium displays no difference in mitosis and apoptosis levels
VillinCre-Brg1fl/fl
VillinCre+Brg1fl/fl

11. Inactivation of Brg-1 in small intestinal epithelium leads to rapid crypt loss
Control
Day 4
Day 5
Day 7
Brg1fl/fl

12. Brg-1 loss leads to the failure of the crypt stem cell
Transit amplifying cells
Active stem cell

13. Loss of Brg-1 results in reduced expression of intestinal stem cell markers
VillinCre-Brg1fl/fl
VillinCre+Brg1fl/fl
p-value < 0.05

14. Generation of double knock-out using Cre-loxP techniques

15. Brg-1/Apc double mutant cells are selectively eliminated in small intestine
-catenin
BRG-1
Small intestine of Brg1fl/fl/Apcfl/fl mouse at day 7 post induction

16. Median survival Apcfl/fl=8 Brg1fl/flApcfl/fl=14, P=0.0010
Brg-1-deficiency rescues lethal phenotype of Apc deletion in double knock-out mice
Control
Brg1fl/flApcfl/fl
Apcfl/fl
Brg1fl/fl
Median survival Apcfl/fl=8 Brg1fl/flApcfl/fl=14, P=0.0010

17. Brg-1 deletion removes a portion of Apc-deficient cells decreasing tumour burden
Brg1-/Apc-

18. Brg-1 deletion removes a portion of Apc-deficient cells decreasing tumour burden
Brg1-/Apc-

19. Adenoma progression depends on the cell of origin
Microadenoma
Transit amplifying cells
Stem cell
Adenoma

20. Conclusions
Brg-1 is a crucial factor for the maintenance of the adult tissue stem cell in small intestine.
Brg-1 loss is incompatible with activation of the Wnt pathway in the murine small intestine
Targeting the intestinal stem cell provides an attractive concept for the removal of potentially malignant lesions in individuals with genetic predisposition to colorectal cancer

21. Acknowledgements The Darwin Trust of Edinburgh Alan Clarke
Boris Shorning
ARC group