BIO230H1 Lecture Notes - Lecture 5: Transmembrane Protein, Model Organism, Morphogen
BIO230
Lecture 5
!
Within an embryo, 4 processes play out at the cellular and tissue level to essentially create the
final organism. These processes are
a) cell proliferation;
b) cell specialization;
c) cell interaction;
d) cell movement.
!
2"main"mechanisms"of"cell"differentiation:"
1) Asymmetric*division:"sister"cells"born"different"(intrinsic'mechanism'–"two"cells"
have"different"collections"of"proteins);"
2) Symmetric*division:"sister"cells"born"the"same"but"become"different"as"a"result"of"
environmental"factors"influencing"them"(extrinsic'mechanism);"
"
Cell*Fate*–"the"ultimate"differentiated"state"to"which"a"cell"has"become"committed""
Cell*Fate*Determination"–"intrinsic"and"extrinsic"mechanisms"which"are"required"for"cell"
differentiation""
"
C.elegans"is"an"adult"worm,"a"great"model"organism"to"study"cell"differentiation"during"
embryonic"development."
"
Extrinsic"mechanisms"of"cell"differentiation:"
"""
1) Direct*lateral*inhibition""
"
Lateral*inhibition*–"the"ability"of"the"cell"to"inhibit"its"neighbours"or"cells"that"their"
neighbours"excite."
"
Ex:"Notch"signalling"
Delta"–"transmembrane"protein"on"one"cell"that"binds"(contact-dependent"signal)"to"
the"Notch"receptor"on"the"neighbouring"cell"and"activates"it.""
Notch*–"transmembrane"protein"on"the"neighbouring"cell"that"once"activated"a)"
inhibits"the"exptession"of"delta"on"the"same"cell"and"b)"inhibits"cell"differentiation"
Fly!sensory!bristle!development"provides"a"model"for"studying"lateral"inhibition."
Because"the"bristle-producing"cells"are"differentiated"(=specialized),"that"means"
that"Notch"is"inactive"."
"
"
"
"
2) Induction*of*diffusible*signals""
Active"Notch'means"that"the"cell"will"NOT"be"differentiated"and"will"NOT"have"
many"Delta"
Inactive"Notch"means"that"the"cell"WILL"be"differentiated"and"WILL"have"
many"Delta"
"
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BIO230H1 Full Course Notes
Verified Note
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Document Summary
Within an embryo, 4 processes play out at the cellular and tissue level to essentially create the final organism. These processes are: cell proliferation, cell specialization, cell interaction, cell movement. Cell fate the ultimate differentiated state to which a cell has become committed. Cell fate determination intrinsic and extrinsic mechanisms which are required for cell differentiation. C. elegans is an adult worm, a great model organism to study cell differentiation during embryonic development. Extrinsic mechanisms of cell differentiation: direct lateral inhibition. Lateral inhibition the ability of the cell to inhibit its neighbours or cells that their neighbours excite. Delta transmembrane protein on one cell that binds (contact-dependent signal) to the notch receptor on the neighbouring cell and activates it. Notch transmembrane protein on the neighbouring cell that once activated a) inhibits the exptession of delta on the same cell and b) inhibits cell differentiation. Active notch means that the cell will not be differentiated and will not have many delta.
