Lecture 14 - Drosophila neurogenesis

Question 1

How does drosophila neurogenesis occur?

Answer 1

lots of homology/analogy to centre rate neurogenesis
- the mesoderm invaginate - then the ventral midline is directly below it, which contains nerves

Question 2

In vertebrates, the neural tube develops on what side?

Answer 2

the DORSAL side

Question 3

What is BMP/Dpp?

Answer 3

a Bone morphogenetic protein (BMP)/decapentaplegic signal (Dpp) signal

Question 4

What is BMP/Dpp important for?

Answer 4

• important for patterning DORSAL in Drosophila
• important for patterning VENTRAL in vertebrates

Question 5

When does inversion occur?

Answer 5

• after the Echinoderms have split off.
• Deuterostomes - inversion hasn’t taken place

BMP & DPP conserved - already present in ancestor of deuterostomes and protostomes

Question 6

What are homologous genes?

Answer 6

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

Question 7

How does neurogenesis occur?

Answer 7

• 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

Question 8

What highly important patterning mechanism process is used in mice, humans and drosophila in the selection of single neuronal cells from the PRONEURAL CLUSTER?

Answer 8

lateral inhibition

Question 9

What sets up a proneural cluster?

Answer 9

The Achaete/Scute genes (pro neural genes)

Question 10

What signalling pathways ensures selection of a single cell out of the cluster?

Answer 10

Notch/Delta

Question 11

What do Achaete/Scute proteins do?

Answer 11

promote Delta expression

Question 12

What is Delta?

Answer 12

• a transmembrane ligand (weird) - it can only influence neighbouring cells
• Delta binds & activates Notch receptors

Question 13

What does a strong Notch signal do?

Answer 13

DOWNREGULATE Achaete/Scute

Question 14

What does high & continuous Achaete/Scute expression do?

Answer 14

activates NEURAL GENES - the ‘losing cell’ reverts to epidermal fate

Question 15

How many proneural clusters are there per segment?

Answer 15

8 - most clusters - most clusters are already single cell

Question 16

How can a Zebrafish embryo be used to research neural development?

Answer 16

Stained for vsx1 - a marker for a particular type of neurone.
- One is wild type
- Other 2 have Notch signal BLOCKED or ACTIVATED

Question 17

What occurs if there is a lot of Notch singalling?

Answer 17

you will not become a neuron

Question 18

What occurs if you have a little bit of Notch signalling and a lot of delta?

Answer 18

you will become the neuron

Question 19

What occurs after selection of a neuroblast?

Answer 19

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

Question 20

What process generates neuronal & glial cells?

Answer 20

asymmetric cell division

Question 21

What occurs to the cell after selection of neuroblast?

Answer 21

cell will drop down from the epithelium into the anterior of the embryo

Question 22

What inherent polarity do all cells in the Drosophila epidermis have?

Answer 22

Apico-Basal polarity

Question 23

What signals are found in the apical side of Drosophila epidermis?

Answer 23

Bazooka (Par 3 in mammals)

Question 24

What signals are found in the basal side of Drosophila epidermis?

Answer 24

Numb

Question 25

How are a number of neural & glial cells generated?

Answer 25

The memory consists of a localised protein complex
- Bazooka (Par3 in mammals) and Insc/Pins are part of this

Question 26

What does the localised protein complex do in the generation of neural & glial cells?

Answer 26

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

Question 27

What similar processes & gens are used to specify adult sensory neurons?

Answer 27

there are proneural clusters in the imaginal disk