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Cell Fate Specification
Definitions:
Differentiation—changes involved in the progressive diversification of the structure and
function of cells
Acquisition of the characteristics that allow different cell types to perform their
functions.
Cell fate—what a cell will become (if left alone).
Potency—what a cell could become
Commitment—restriction in potency
Specification—labile state where a cell has reversibly acquired fate (potency > fate)
Determination—state where a cell has irreversibly acquired fate (potency = fate)
Determinant—a molecule that regulates cell fate
Morphogen—a molecule forms a gradient and regulates cell fate in a concentration
dependent manner.
I. Types of Specificaton
A. Autonomous Specification
• Remove a cell and the cell types normally derived from that cell will not form.
• Isolate a cell and it will form the cell types it normally would have.
B. Conditional Specification
• Remove a cell and the cell types normally formed by that cell will be contributed
by other cells (compensation)
C. Syncitial Specification
• Important in insects
II. Autonomous Specification
• Asymmetric distribution and inheritance of determinants
• Determinants typically cytoplasmic (Fig. 3.10).
• Determinants usually RNAs or proteins
e.g. 1. MACHO mRNA localized in yellow cytoplasm of tunicate embryo
o Antisense blocks muscle formation (=necessary)
o Injected mRNA induces animal pole to form muscle (=sufficient)
•
e.g. 2. SKN-1 protein localized in C. elegans EMS cell (pharynx derived from
EMS)
o skn-1 loss-of-function mutant produces no pharynx (necessary)
Fucus contains cell wall determinants (handout)
III. Conditional Specification
• A cell’s fate is determined by its environment
A. Cell interactions.
• Contact with neighboring cells influence cell fate
e.g. sea urchin (fig 8.14)
o Animal pole cells alone produce ectoderm only
o Animal pole cells plus micromeres produce cell types normally derived
from vegetal pole cells
Stem Cells—cells that divide to maintain a self-renewing population, and contribute
daughters that will differentiate.
Can get progressive commitment.