2nd year recap Flashcards
What is neurogenesis?
The growth and development of the nervous tissue
When does neural patterning and neurogenesis occur?
When is this process in humans?
After the formation of the neural tube from the neural plate
Between 4-12 weeks
How does the neural plate roll up to become the neural tube?
At what somite stage?
NOT uniform:
- First to roll up becomes the HINDBRAIN
- Lots of morphogenesis
0-3 somite stage
What is spinal bifida?
When the spinal cord doesn’t close
Where is the neural tube wider? Why?
At the BRAIN - due to more cell proliferation
What breaks the symmetry of the neural tube?
Differential proliferation (more are the brain)
How do neurons form?
What is this governed by?
What does this determine?
Same as cell differentiation in any part of the body:
- Cells become DIFFERENT from each other and ACQUIRE SPECIALISED properties
- Governed by CHANGES in GENE EXPRESSION, which dictate the REPERTOIRE of protein synthesised
- REPERTOIRE of proteins translated dictate a cells BEHAVIOUR (eg. proliferation, migration etc)
How do CHANGES in GENE EXPRESSION dictate the REPERTOIRE of protein synthesised?
Determine which proteins are transcribed and translated into protein and determine which proteins are actively repressed
What happens to the potency of a cell over time? Why?
Potency is REDUCED - cells become more specialised/differentiated as repertoire of protein changes
What 2 things are gene expression (repertoire of proteins/genes) in a cell governed by?
1) EXTRINSIC factors (morphogens and signals)
2) INTRINSIC factors (transcription factors)
When does differentiation occur?
Over TIME as CELLS DIVIDE
What cells are neurons born from?
Progenitor cells
What are progenitor cells?
Cells that are slightly more specialised than stem cells but aren’t fully committed (have lost some potency)
Tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its “target” cell
Where is the action of TF important?
In progenitor cells
As progression of a cell occurs, what does the cell become dependant on?
TF (switch from morphogens)
What causes the differentiation of neurons?
Secreted morphogens and intrinsic transcription factors
What does ISH of shh mRNA in the neural tube show?
Shh is NOT INITIALLY expressed in the neural tube itself
1) INITIALLY expressed in a rod of mesoderm that lies beneath the ventral midline of the neural tube
2) Then shh is expressed in a triangular shaped region at the ventral midline (floor plate)
What does shh code for?
A SECRETED protein
What experimental procedure allows to see protein?
Antibody labelling experiment (make antibody against the protein)
What does an antibody labelling experiment of shh show?
- Shh expressed in the notochord and floor plate and in cells next to the floor plate (extending dorsally)
Shows shh:
- Is secreted from cells making it and extends dorsally
What type of molecule does shh act as?
What does this do?
Acts as a MORPHOGEN
To induce different progenitor cells along the dorso-ventral axis of the future spinal cord
What is a morphogen?
A SECRETED protein which establishes a CONCENTRATION GRADIENT
How do cells respond to a morphogen gradient?
Cells respond DIFFERENT THRESHOLDS of morphogen and respond DIFFERENTLY by eliciting DIFFERENT programmes of GENE EXPRESSION - make cells different
What is the difference between a stem cell and a progenitor cell?
PC only has a LIMITED NUMBER of cell divisions that it can make before it eventually differentiates
