Lecture 14 - Drosophila neurogenesis Flashcards
How does drosophila neurogenesis occur?
lots of homology/analogy to centre rate neurogenesis
- the mesoderm invaginate - then the ventral midline is directly below it, which contains nerves
In vertebrates, the neural tube develops on what side?
the DORSAL side
What is BMP/Dpp?
a Bone morphogenetic protein (BMP)/decapentaplegic signal (Dpp) signal
What is BMP/Dpp important for?
- important for patterning DORSAL in Drosophila
- important for patterning VENTRAL in vertebrates
When does inversion occur?
- after the Echinoderms have split off.
- Deuterostomes - inversion hasn’t taken place
BMP & DPP conserved - already present in ancestor of deuterostomes and protostomes
What are homologous genes?
although the names differ somewhat, genes that were found to be important for defining different neural domains in Drosophila, fulfil similar roles in a mouse - a mammal like use
How does neurogenesis occur?
- not all cells in the fly neuroectoderm will become neurones - some will remain ectodermal
- single neuronal cells are selected from a group of equivalent cells - A PRONEURAL CLUSTER
- this process uses a highly important patterning mechanism that you will come across in mice/humans - lateral inhibition
What highly important patterning mechanism process is used in mice, humans and drosophila in the selection of single neuronal cells from the PRONEURAL CLUSTER?
lateral inhibition
What sets up a proneural cluster?
The Achaete/Scute genes (pro neural genes)
What signalling pathways ensures selection of a single cell out of the cluster?
Notch/Delta
What do Achaete/Scute proteins do?
promote Delta expression
What is Delta?
- a transmembrane ligand (weird) - it can only influence neighbouring cells
- Delta binds & activates Notch receptors
What does a strong Notch signal do?
DOWNREGULATE Achaete/Scute
What does high & continuous Achaete/Scute expression do?
activates NEURAL GENES - the ‘losing cell’ reverts to epidermal fate
How many proneural clusters are there per segment?
8 - most clusters - most clusters are already single cell
How can a Zebrafish embryo be used to research neural development?
Stained for vsx1 - a marker for a particular type of neurone.
- One is wild type
- Other 2 have Notch signal BLOCKED or ACTIVATED
What occurs if there is a lot of Notch singalling?
you will not become a neuron
What occurs if you have a little bit of Notch signalling and a lot of delta?
you will become the neuron
What occurs after selection of a neuroblast?
it will generate a number of neuronal & glial cells in a very stereotypical manner
- the process that is employed is interesting because it also happens in various different tissues & organisms (mammals) - Asymmetric Cell Division
What process generates neuronal & glial cells?
asymmetric cell division
What occurs to the cell after selection of neuroblast?
cell will drop down from the epithelium into the anterior of the embryo
What inherent polarity do all cells in the Drosophila epidermis have?
Apico-Basal polarity
What signals are found in the apical side of Drosophila epidermis?
Bazooka (Par 3 in mammals)
What signals are found in the basal side of Drosophila epidermis?
Numb
How are a number of neural & glial cells generated?
The memory consists of a localised protein complex
- Bazooka (Par3 in mammals) and Insc/Pins are part of this
What does the localised protein complex do in the generation of neural & glial cells?
the protein complex directs the localisation of proteins and certain RNAs on the opposite side of the cell - ‘Numb’ is an important part of this
What similar processes & gens are used to specify adult sensory neurons?
there are proneural clusters in the imaginal disk
