What Are Cell Differentiation and Cell Specification?

What Are Cell Differentiation and Cell Specification?

? Development of differentiated cell types

? different in function, cell shape, internal structures, proteins and biochemical pathways

? Preceded by commitment to fate

? Specification: can differentiate in neutral environment, but reversible in new environment

? Determination: irreversible even in new environment

What Are the Different Modes of Specification?

? Autonomous Specification

? Independent of other cells in embryo (selfdifferentiating parts)

? Determined by internal cytoplasmic factors ? If cleavage patterns are invariant, then cell fates will be

invariant ? "Mosaic" development ? Characteristic of invertebrates

What Are the Different Modes of Specification?

? Conditional Specification ("Non-Autonomous")

? Depends on conditions (cell interactions) ? More variable (variations in which cells are assigned

which fates) ? Capacity to "regulate" ? Characteristic of vertebrates (and some invertebrates)

What Are the Different Modes of Specification?

? Syncitial Specification

? Interactions between regions of cells before cellularization

? Cells have no specific cell fate before cellularization ? After cellularization, mostly conditional specification ? Most insects

Chabry's Experiment 1887

? Mollusc ? Certain cells

form trochoblasts (ciliated) ? In isolation ? autonomous

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