Molecular Patterning During Development Flashcards
State the principles governing cell differentiation
Generative program
Regulatory proteins work together to form a ‘committee’ to control the expression of a eukaryotic gene.
Combinations of a few gene regulatory proteins can generate many different cell types during development.
Describe what the embryo contains
The embryo does not contain a description of the adult, rather it contains a generative program for making it.
Cell differentiation
Process by which embryonic cells become different from one another.
What does cell differentiation involve ?
Involves the emergence of cell types such as muscle, nerve, skin and fat cells.
It is the achievement of a stable terminally differentiated state (not just transitory differences).
How are differentiated cells characterised ?
Characterised by the profile of proteins in that cell.
Describe cells just after fertilisation
Totipotent
- can form every cell in the body
- placenta too
Potency
The entire repertoire of cell types a particular cell can give rise to in all possible environments.
Toti
Whole cell
Totipotent
Cells of the very early mammalian embryo
Identical and unrestricted
Can give rise to any cell of the body
EMBRYONIC
Describe cells that go on to form the embryo
Pluripotent
- Can’t form placental tissues
Pluri
More
Pluripotent
Inner cells of blastocyst
Less potent
Can give rise to many cell types but not all
EMBRYONIC
Multi
Many
Multipotent
EXAMPLE:
Blood stem cells
They give rise to cells that have a particular function (e.g. red or white blood cells)
ADULT
Order of stem cells and potency
Totipotent
Pluripotent
Multipotent
Commitment
Each decision that restricts cell fate
- cells are committed
Key feature of commitment
Occurs in 2 stages
1. Specification (reversible)
2. Determination (irreversible)
Describe the 1st stage of commitment
Specification (reversible)
Cells are capable of differentiating autonomously if placed in isolation BUT can be respecified if exposed to certain chemicals/ signals.
Describe the 2nd stage of commitment
Determination (Irreversible)
Cells will differentiate autonomously, even when exposed to other factors or placed in a different part of the embryo.
How does a naive cell become specified ?
Intrinsic and Extrinsic Signals
Intrinsic signals
Cell autonomous signal tells the cell ‘who it is’
Extrinsic signal
A chemical or molecule in the environment gives the cell spatial information, tells the cell ‘where it is’
Describe cell fate
The fate of a cell describes what it will become in the course of normal development.
What does determination imply ?
Implies a stable change - the fate of determined cells does not change.