Adult stem cells in the gut Flashcards
How can we identify stem cells?
Look at the expression of stem genes by staining or in situ hybridisation. Take sections from embryonic tissues and use probes
What is the gene which is only expressed in the stem cells and none of daughter progenitors
Found this gene through studies of removing elements of signalling pathways- armadillo is a key component of the Wnt signalling pathway
What was the effect of k/o elements of the Wnt signalling pathway
It became apparent that they are vital in maintaining stem cells in their niches. Wnt signalling confers stemness
What is the gut crypt?
Tube of cells with stem like cells in a niche at the distal end and differentiated cells at the proximal end. Each villi has one.
What are cells in the crypt responding to?
Wnt/BMP/JAKSTAT there is a rim of stem cells at the bottom of the crypt to the actual tip of the crypt. They are surrounded by other cells called Paneth cells (support cells)
Why do we need a gut stem cells population?
When you digest, pathogens also enter the small intestine which could be harmful to the body. The small intestines are continuously replacing the damages cells- almost like a treadmilling effect
What are the first progenitors from the crypt called?
Transit amplifying cells
Which signal is expressed at very high levels in the crypt?
Wnt- It is expressed in an around the base of the crypt. There is a Wnt target gene calles LGR5 which is expressed in stem cells
What is the name of the cells in the crypt
Crypt base columnar cells
What experiments were conducted to show LGR5 cell is the stem cell?
Ectopically transplant and observe cell behavior- should be able to self-renew and produce villi
Lineage mapping using transgenic reporter lines (can’t do in situ). LGR5 is expressed
What to do once you have identified the LGR5 cells?
Dissect them out and then lineage trace the daughter cells
What is the advantage of using fluorescent markers?
Only the stem cell will fluoresce- can separate them and make a pure sample of stem cells. Can also produce organoids out of these tissues which are important for drug studies
