Developmental committment Flashcards
Committed vs not committed
- see figure
How do cells become committed to form a tissue?
- through the process of differentiation
cell fate
- what a cell or tissue develop into
- early committed cell is not phynotypically different from uncommitted cell
- normal fate does not mean cell develops the same in every environment
potency
- potential to differentiate
commitment
- state in which a cells developmental fate becomes restricted
- not displaying big changes in biochemistry or function
specification
- group of cells gain a bias toward certain cell fate
- if isolated and cultured, develop according to that fate
- flexible process, can still be altered due to signals
determination
- cell fate irreversible
- stable change in internal state of a cell, fate is now fixed
- CANNOT develop into another type in response to signals
developmental stages
- see figure
acquisition of committment
- cells receive signals that cause them to develop down a certain pathway… asymmetrical signals determine fate
- internal signals
- external signals
- see figure
induction
- instructive signals from one cell or tissue
- cause change in cellular behavior of responding cells
competence
- cells in presence of the signal must be competent to respond for a change to occur
Draw normal vs lack of induction/competence
–
how are cells differentially induced
- morphogen gradient
- lateral inhibition
morphogen gradients
- cells respond to signals in a concentration-dependent manner
- concentrations of activin leads to different types of mesodermal cells…
- see figure
use of morphagens to give positional information
- see graph
induction
- one cell produces a molecule that causes adjacent cells to differentiate with a specific fate
morphogens
- form concentration gradient to determine fate of cell
general lessons of morphogen gradients
- 1) morphogen concentration dependent induction of gene expression
- 2) both activators and repressors determine expression patterns
- 3) combinatorial gene control mechanisms
- 4) regulatory gene hierarchy
morphagen concentration dependent induction of gene expression
- ## see figure
both activators and repressors determine expression patterns
- ## figure
combinatorial gene control mechanisms
- combo gene control occurs when gene expression requires presence or absence of particular combo of regulatory proteins
- TF’s used in different combos to regulate
- creates complex networks
- see figure
regulatory gene hierarchy
- see figure
early gradients activate gap genes
- cascade begins when signals from maternal proteins activate gap genes…
- each gap gene is expressed in specific domain in embryo
- further refined through pair rule genes
what controls composition and function of the positional info that patterns embryos?
- combinatorial interactions
- negative feedback
central idea to differentiation of tissues and organization?
- morphogen concept
- diffusible signaling molecules are proposed to coordinate cell fate specification and tissue formation using concentration dependent mechanisms
Morphogen gradiants
- not static
- change with time.,.. time is a critical parameter
lateral inhibition
- one cell produces an inhibitor that prevents neighboring cells from differentiating with a particular fate
ex: drosophila cells express brown, become ectoderm, inhibit neighboring cells from doing the same thing
lateral inhibition in the determination of cell fate
- cell starts off as equivalent
- stochastic event causes one cell to produce more of a singla molecule at some critical time
- difference is amplified until cell becomes different types
lateral inhibition in patterning
- gibing tissues a cell spacing pattern (figure)
ex: neurons and glial cells
