Lecture 11 (5b) - Neurogenesis in Invertebrates and Axonal Pathfinding Flashcards Preview

Cell Bio & Developmental Genetics > Lecture 11 (5b) - Neurogenesis in Invertebrates and Axonal Pathfinding > Flashcards

Flashcards in Lecture 11 (5b) - Neurogenesis in Invertebrates and Axonal Pathfinding Deck (24):
1

Neural stem cells have evolved

independently in arthropods and vertebrates

2

Insect and vertebrate neural stem cell development and regulation are

different
Insects
• neural stem cell proliferation
• asymmetric division in epithelium
• formation of postmitotic neurons

Vertebrates
• neuroblast formation
• neuroblast delamination
• formation of postmitotic neurons

3

Similar to vertebrate neural stem cells, Daphnia magna neuroblasts

remain in the epithelium

4

Morphology of Daphnia magna embryo during neurogenesis

neuroblast formation = smooth w/ slits
differentiation of neurons = slits bump out, formation of axonal tracts

5

Homologues of Drosophila neural genes are

expressed in Daphnia magna neurogenesis

6

In Daphnia, no proneural cluster -->

ring of neuroblasts
(Drosophila has proneural clusters so different regions w/ clusters)

7

sna --> ASH in

both Daphnia and Drosophila

8

ASH not that important in

neuroblast formation

9

The differences in the morphology of neuroblast formation are reflected in the

gene expression patterns

10

Vertebrates show a similar sequence of gene expression

neural cell formation -->
MASH, Notch signalling -->
MASH, Prox1

in vertebrates, ASH not needed for neural stem cells
MASH switches on Prox1
Prox1 for asymmetrical divisions --> neurons

11

Notch keeps cells

in transition phase so there's enough neural stem cells

12

Most neuroblasts do not generate GMCs before

NS4 = ~ 10 hours delay
• most neuroblasts form very early (NS2) but don't form GMC until late

13

The members of Notch signalling pathway are expressed in

neuroblasts
• Notch also needed in limb development

14

Inactivation of Notch signalling leads to

over-expression of Dam sna and Dam pros in al cells of the ventral neuroectoderm
• DAPT inhibits Notch

15

Inactivation of Notch signalling leads to

premature generation of GMCs
• immediately divide GMCs --> neurons early w/o Notch
• inactivation of Notch signalling also leads to ectopic formation of neuroblasts

16

GMC

ganglion mother cell

17

Notch signalling is required for

binary cell fate decisions in crustaceans
• the restriction of neuroblast formation to the ring-like domain results in a limited number of neuroblasts (typical feature of euarthropods)

• Notch needed in Daphnia
keeping neuroblasts silent (no division)

18

Model for neuroblast regulation in D. magna

• neuroblast generation and division (sna+)
• transition (n+, DI+, Hes+, ASH+, sna+)
• GMC production (DI++, pros+, ASH++, sna+)

19

Neurogenesis can be subdivided into 4 processes

1. generation of neural precursors
2. establishment of neural precursor identity
3. differentiation of neural precursors
4. establishment of neuronal networks

20

The generation of neuronal processes occurs at

the growth cone
• filopodia of actin

21

What is the function of neuronal growth cones?

1. growth cones navigate the developing axon/dendrite through the developing embryo towards the target cell
2. Growth cones form the developing axon/dendrite
3. Growth cones form the pre- and postsynaptic structure

22

Growth cones contain

actin and microtubuli
• actin make filopodia
• p = peripheral
• c = core regions
• n = neurite

23

Filopodia

touch/sense signal, stabilize
• made of actin

24

The different structures of the peripheral domain of the growth cones

philopodia --> lamellipodium