BIOL 303 Lecture Notes - Cre Recombinase, Paneth Cell, Goblet Cell
Chapter 22: Stem Cells & Tissue Renewal
Lecture I
• Recall the process of intestinal cell migration from crypts to villi, and where cell types
are located (slide 4).
• Crypts include the stem cells at the very bottom. Villi are the spaces between the
crypts. Paneth cells are at the bottom of the crypt. The stem cells migrate via Cre
recombinase and Lac-Z up the walls to the Villi.
• Match the type of intestinal cell with its function (slide 5).
• Absorptive cells (aka brush/border cells, enterocytes): majority of cells,
microvilli extend into lumen, absorb nutrients and produce hydrolytic enzymes.
• Goblet cells: secrete mucus into lumen that coats guts epithelium
• Paneth cells: part of innate immune system - kill bacteria.
• Enteroendocrine cells: secrete serotonin and hormones that act on gut neurons &
gut cells to regulate digestion and cell proliferation.
• Describe how clonal analysis revealed that intestinal stem cells divide by independent
choice rather than asymmetric division, and how these two strategies work (slides 6-8).
• Stem cells can divide and become either a stem cell or a differentiated cell. Stem
cell will divide and become two different cells and each cell will become one or
the other.
• Independent choice – divide randomly and not asymmetrically. 50% chance in a
test tube scenario.
• Asymmetric division – determining protein within stem cell that drives it to
become one or the other. One side has more, and one has other. The one with
more will stay stem cell and the other will differentiate.
• Used clonal analysis to reveal which type of division the gut used. This revealed
independent choice due to the Cre recombinase (protein driven by stem cells) and
tamoxifen and LacZ which was only expressed when Cre recombinase was
around. After this they did post-hoc staining and revealed stem cells were
responsible for both the stem and differentiated cells at about a 50% chance.
Lecture I Part Deux
• Describe how clonal analysis revealed that intestinal stem cells divide into transit
amplifying cells by independent choice (slides 6-8) – talked about this again here.
• Used clonal analysis to reveal which type of division the gut used. This revealed
independent choice due to the Cre recombinase (protein driven by stem cells) and
tamoxifen and LacZ which was only expressed when Cre recombinase was
around. After this they did post-hoc staining and revealed stem cells were
responsible for both the stem and differentiated cells at about a 50% chance.
• Recall the differences between independent choice and asymmetric stem cell division
(slides 9-10).
• Independent choice – divide randomly and not asymmetrically. 50% chance in a
test tube scenario.
• Asymmetric division – determining protein within stem cell that drives it to
become one or the other. One side has more, and one has other. The one with
more will stay stem cell and the other will differentiate.
• Briefly describe how Paneth cells and Goblet cells maintain cell fate through R-spondin
and Notch signaling (slides 11-13).
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