Alexis Carulli CCB Project
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Transcript of Alexis Carulli CCB Project
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Alexis CarulliCCB Project
Notch Regulation of Intestinal Crypt Dynamics
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The Intestinal Crypt: Proliferative Zone
Transit-AmplifyingProgenitor(TA)
Stem CellNotch?
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Experimental Observations HypothesisAsymmetric Cell Division
Symmetric Cell Division
Notch Inhibition
5 day Notch inhibition1 day Notch inhibition
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Continuous Compartmental Model of Crypt Dynamics
α1
α2
α3
β1
β2
β3
γ
apoptosis apoptosis
renewal renewal
differentiation differentiation sloughing-off N0Stem
N1TA
N2Diff
WITH FEEDBACK: = (α3 – α1 – α2)N0 –
k0N20
1 + m0N0
dN0
dt
k0N20
1 + m0N0 = (β3 – β1 – β2)N1 –
k1N21
1 + m1N1
dN1
dt + α2N0 +
= – γN2 + β2N1 + k1N2
1 1 + m1N1
dN2
dt
Johnston et al. PNAS 2007
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Continuous Compartmental Model of Crypt Dynamics
α1
α2
α3
β1
β2
β3
γ
apoptosis apoptosis
renewal renewal
differentiation differentiation sloughing-off N0Stem
N1TA
N2Diff
WITH FEEDBACK: = (α3 – α1 – α2)N0 –
k0N20
1 + m0N0
dN0
dt
k0N20
1 + m0N0 = (β3 – β1 – β2)N1 –
k1N21
1 + m1N1
dN1
dt + α2N0 +
= – γN2 + β2N1 + k1N2
1 1 + m1N1
dN2
dt
Johnston et al. PNAS 2007
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Continuous Model: α2 and α3 analysis
1 day Notch inhibition 5 day Notch inhibition
α2 = 1α3 = 0
α2 = 3α3 = 0.586
Homeostatic rates: α2 = 0.3, α3 = 0.586
α2 = 5α3 = 0.001
N2
N0
N1
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Continuous Compartmental Model of Crypt Dynamics
α1
α2
α3
β1
β2
β3
γ
apoptosis apoptosis
renewal renewal
differentiation differentiation sloughing-off N0Stem
N1TA
N2Diff
Even if N0=0 there is still a population of N1 and N2 cells:
Johnston et al. PNAS 2007
N2
N0
N1
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Continuous Model: β3 analysisHomeostatic rate: β3 = 0.732
1 day Notch inhibition 5 day Notch inhibition
Β3 = 0α2 = 1α3 = 0.3
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D(t+1) = D + 0.6T2 – γ
T1(t+1) = 3XS TT(t+1) = T1 + T2
T2(t+1) = 4T1
S(t+1) = S + (1-X)S + R
Discrete Compartmental Model of Crypt Dynamics
X
R
γ
ASSUMPTION: When crypt is in homeostasis, apoptosis is negligible in S and T compartments
renewal
differentiation amplification Sloughoff S
Stem T1TA
DDiff
T2TA
differentiation
X= Stem cell division symmetryX=0: completely symmetric, towards SX=1: completely asymmetric, equal S and TTX=2: completely symmetric, towards TT
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Discrete Model: X analysis
X=0
X=1
X=2Maximum is 60% increased from TTi
NOTE: In my experiment I saw a 60% increase in proliferating cells after 1 day of Notch inhibition
S grows exponentially, TT crashes
Homeostasis
TTS
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Discrete Model; x=1.5 1 day Notch inhibition 5 day Notch inhibition
No stem cell renewal
Constant stem cell renewal
Notch-dependent stem cell renewal
TTS
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Discrete Model: Alternate hypothesis
Notch inhibition may result in stem cell apoptosis and the rebound stem cell overpopulation, without affecting differentiation rate of
STT
1 day Notch inhibition 5 day Notch inhibitionTTS
Stem cell loss
Stem cell rebound
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Future Directions
X
R
γS
Stem T1TA
DDiff
T2TA
T3TA
T4TA
1) Test different permutations of amplification scheme
2) Design hybrid model- Neither discrete nor continuous is likely correct - Adapt discrete model to ODEs with feedback, but maintain dependence on S compartment
3) Do more experiments!- Check intermediate time points for proliferation drop
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Thanks!Many thanks to the course instructors
(Especially Greg!) and the TAs.
It was great to meet all of you. Safe travels home and may you have many Science/Nature/Cell
publications in the future