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The first morphological segmentation of the gut divides it into what divisions?
foregut, midgut, hindgut
Subdivision of the endoderm into broad domains occurs when?
during or directly after gastrulation
What transcription factor is selectively expressed in the caudal endoderm immediately after gastrulation?
Cdx2
Deletion of cdx2 has what effect on the embryo?
gut truncation and anterior transformation of the hindgut
subdivision of the gut into more refined, organ forming domains appears to be dependent on _____________ and ____________.
elongation of the gut tube, repression of anterior gut fate
Axial elongation of the gut tube is dependent on signaling of what gene?
Wnt
What is the canonical Wnt signaling pathway?
Wnt is a secreted factor that binds to plasma membrane receptor Frizzled, causes increased b-Catenin and translocation of b-cateninfrom cytoplasm to nucleus --> gene transcription
The primitive gut tube becomes surrounded by the __________ during radial patterning.
splanchnic mesoderm
The splanchnic mesoderm gives rise to what tissues?
connective tissue, smooth muscle, vasculature
The autonomic ganglia and enteric nervous system are derived from _________ which is itself derived from the _________ layer.
neural crest, ectoderm
The epithelia of the lung, gut, and gut associated organs is derived from what layer?
endoderm
The _______ layer produces signals to an ___dermal tyrosine kinase receptor that mediates neural crest migration.
mesodermal, ecto
Defective colonization of the gut by neural crest results in what condition?
Hirschprung's Disease
The sonic hedgehog and indian hedgehog are secreted factors from the __________ layer that signal to receptors in the ______ layer.
endoderm, mesoderm
Sonic hedgehog has two membrane proteins that are required for its transactivation, and this is mediated through the ________ family of transcription factors.
Gli
In the absence of Shh and Ihh, what is the effect on the mesoderm?
does not proliferate/differentiate
What structural features are common for shh and ihh null mice?
tracheal esophageal fistulas (septum from splanchnic mesoderm), persistant cloaca (urorectal spetum from splanchinc mesoderm)
incomplete inhibition of hedgehog signaling at late stages of gestation has what effect on the cytology of the gut?
disruption of the crypt-villus architecture, proliferation, and upward differentiation
Along the crypt-villus axis is a gradient of ______ expression.
Wnt
In the absence of Wnt signaling, what happens?
gut epithelium is depleted
Which downstream signal of Wnt has been shown to mark intestinal stem cells?
Lgr5
New evidence shows that _______ form the niche for stem cells in intestinal crypts.
paneth cells
What factors in the destruction complex are responsible for ubiquitinating and degrading b-catenin in the absense of Wnt ligand?
Axin, APC, Gsk3
80% of colorectal cancers have mutations in what gene?
APC
x of y cards