Making a Neuron Flashcards
Formation of nervous system
- Specification of neuroectoderm
- Specification of neruoblast
- Division and migration
- Differentiation
- Innervation of target tissue: axon guidance
- Synapse formation
- Pruning
What does the neuroectoderm of the Drosophila gastrula givers to?
The CNS of the larva
What are the small groups of cells in the neuroectoderm called?
Proneural clusters
What do the cells in each cluster form?
An equivalence group - all have potential to be differentiated into neuroblasts
How many cells in each cluster become a neuroblast?
Only one
What is the secondary fate of cells in proneural clusters
Epidermis
How is it that only one cell in each pronerual cluster becomes a neuroblast?
Lateral inhibition
What is lateral inhibition mediated by?
Delta-Notch signalling
What type of signalling is Delta-Notch signalling an example of?
Juxtacrine signalling
Delta is a _______ ______
Transmembrane ligand
Notch is a ________ _____
Transmembrane receptor
Do all the cells in the equivalence group express Delta and Notch?
Yes
What is an equivalence group?
Set of unspecified cells that have the same developmental potential or ability to adopt various fates
What happens in terms of Delta and Notch expression when one cell is differentiating into a neuroblast?
- One cell will start expression Delta more strongly so other cell’s Notch more active
- This cell inhibits other cells’ Delta expression
What does a homozygous loss-of-function mutation in either Notch or Delta result in?
All cells in the pro neural clusters become neuroblasts
Neuroblast cell behaviour
Delamination and asymmetric division
Process of making a neuron? maybe
Neuroblast delaminates form the neuroectoderm and into embryo
Undergoes asymmetric division to form a ganglion mother cell which inherits the Numb protein and neuroblast cell
Segregation of cytoplasmic factors into one daughter cell (i.e. Numb)
Neuroblast splits and creates more ganglion mother cells
A neuroblast undergoes asymmetric division to form what?
A ganglion moter cell and a neuroblast cell
What does the ganglion mother cell inherit?
Numb protein
Drosophila have what which are sensitive to mechanical movement?
Mechanosensory bristles
What is each sensory bristle organ a clone of?
Four cells derived from a sensory organ precursor (SOP_
What are the components of a mechanosensory bristle?
- Hair cell (trichogen)
- Socket cell
- Sheath cell (thecogen)
- Sensory neuron
What do sensory bristles in Drosophila arise from originally?
Proneural clusters
What does a cell in the pro neural cluster differentiate into instead of a neuroblast for the fate of becoming a bristle?
Sensory organ precursors (SOPs)
How are SOPs singled out?
By lateral inhibition from pro neural clusters. Involves Delta-Notch signalling
When does a SOP form 4 neurones?
When there is either a loss-of-Notch-function or overxpression of Numb
What happens when there is either a loss-of-Notch-function or over expression of Numb?
SOP divides into four neurones
Why does the over expression of Numb have the same effect as a loss of Notch function?
Numb inhibits Notch
Neuronal differentiation
Axon outgrowth and patfinding
How do neurones pathfind?
Growth cone at tip of axon
What are neural connections refined by?
Pruning and cell death
Examples of long-range cues
- Chemoattractants
- Chemorepellants
Examples of short range cues
- Contact attraction
- Contact repulsion
