Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Dev Neurobiology extra > Lecture 12 Axon guidance 2 > Flashcards

Lecture 12 Axon guidance 2 Flashcards

1
Q

How are neurites selected in vitro

A

MT stability
Competition between neurites
Feedback loop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

When is neuron polarity established in vivo?

+ example

A

As neurons are born
Suggests neurite selection is based and influenced by the cellular environment
e.g. radial glia already polarised apical to basal and polarity preserved as cell divide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Growth cones of what organism are easier to image?

A

Aplysia

GC sits down more

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the three domains of growth cones?

A

C DOMAIN - central
T ZONE - transitional
P DOMAIN - peripheral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are made from different types of F-actin?

A

filopodia and lammelipodia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are filopodia?

A

Type of protrusion

  • Finger-like projections
  • Core of long, bundled actin filaments
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are lamellipodia?

A

Type of protrusion

  • Sheet-like structures
  • Crosslinks into a net
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the action of F-actin in growth cones?

A

Treadmills in resting growth cone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe actin treadmilling

A

Tubulin is dragged sporadically into Filopedia
Flow from periphery to centre
Filaments break up and recycled to tip

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens to F-actin treadmilling when the cell experiences attractive cue?

A

Tubulin are dragged more dramatically to filopedia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do growth cones change direction?

A 
They do not turn 
They reorganise their MT
1. GC contacts attractive cue 
2. F actin treadmilling slows 
3. F actin accumulates
4. This stabilises filopodium and drags MT to back of filopodium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Is a substrate sufficient enough to drive forward movement?

A

NO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What else is needed to drive movement forward?

A

Stimulus of cue to rearrange cytoskeleton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What part of filopodium is attached to substrate

A

C domain = palm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Discuss actin treadmilling process before and after attractive cue encountered

A
  1. slow undirected growth - resting - max actin flow
  2. Growth cue encountered - filopedia extension and reorientation of MT - fast directed growth. Accumulation of F actin to stabilise filopodium and drag MT to back of filopodium
    - MOLECULAR CLUTCH - slows rearward (back) treadmilling
    - ACTIN-TUBULIN LINK - pulls microtubules into the wake of extending filopodium (i.e. back into filopodium)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can cues do to growth cones? + experiment

A

attract and repel them

e.g. mix RGC and SN - fasiculate only with own type due to repulsion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens when growth cones encounter repelling cue?

A

Growth cone collapse - STILL ATTACH - retreat and reorganise

F actin is destabilised and get decrease in F actin (opposite to attractive cue)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Example of family of inhibitory cues? Found by?

A

Semaphorins

Biochem pur of retina showing collapse of sensory axons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Semaphorin types

A
  1. membrane bound

2. secreted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Example secreted semaphorin

A

Sema 3A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What do semaphorins cause?

A

Collapse of F actin

22
Q

What is essential for axon growth? How was this shown

A

axon attachment via palm

Embryonic chick DRG neurons cell bodies and axons - Polyornithine sticky, palladium non-sticky

23
Q

Relationships between adhesion and outgrowth

A

NO RELATIONSHIP

24
Q

What ECM component does DRG stick better to (adhesion)

A

Collagen

25
Q

What ECM component is DRG growth better on

A

Laminin

26
Q

What can permissive factors do? Example

A

Can define substrate paths in the embryo

Laminin allows RGC to enter tectum - promoting ECM in optic nerve

27
Q

Other name for permissive factors

A

Contact attractants

28
Q

What do permissive factors not dictate? Shown by

A

direction - only allow growth

  1. block laminin R –> decrease in retinal growth but direction unchanged
  2. Gradients of laminin in vitro don’t alter growth (if in certain range)
29
Q

Permissive factors are x2

A

Permissive to allow growth

Not instructive to alter direction

30
Q

What are non-permissive factors often called?

A

Contact repellents

31
Q

What can non-permissive factors do?

A

Channel axon growth

32
Q

What does outgrowth depend on in presence of non-permissive factors

A

Permissive factors

33
Q

Example of non-permissive factor and its function

A
  • semaphorins
  • tell an axon it can’t grow there
    e. g. Grasshopper limb bud Ti1 –> Cx1 turns at semaphoring zones
34
Q

What occurs in mice lacking Sema 3A

A

End in wrong territories

35
Q

Therefore, what is axon growth a balance between?

A

permissive and non-permissive factors

36
Q

What are ephrins?

A

non-permissive factors used in early patterning and to guide axons

37
Q

What are ephs?

A

cell surface molecules detected by receptors

38
Q

What do ephs and ephrins cause?

A

REPULSION between cell

39
Q

What are the ephs and ephrins important for?

A
  • compartmentalisation in early development into distinct domains e.g. rhombomeres
  • late dev for keeping axon out of specific areas as do semaphorins
  • making topographic maps - reciprocal patterning
40
Q

Where are ephs restricted to in vertebrate

A

Proximal distal limb tips

41
Q

Where are ephrins restricted to in vertebrate

A

Middle

42
Q

What does the floor plate secrete that effects axon growth?

A

Netrin

43
Q

What do we know key patterning organisers secrete?

A

ong distance guiding molecules - chemoattractant and chemorepellents
These guide the axons (where as short distant just say where can and cant go)

44
Q

What does netrin do?

A

act as a chemoattractant for axons - makes axons grow towards it

45
Q

Where is netrin expressed

A

Vert midline of NS

46
Q

What do floor plate cells and cells expressing netrin gene turn on

A

Commissural axons

47
Q

What does the roof plate secrete that affects axon growth?

A

a chemorepellent in the form of a BMP - doesn’t allow axons to gorw in that direction

48
Q

What does BMP7 cause

A

Growth cone collapse

49
Q

A combination of what causes axon growth towards floor plate?

A

Push factor = BMP

Pull factor = Netrin

50
Q

Example of long and short cues working together

A

Sema 1 cells surface - blocking with AB means axon stays in wrong are
Sema 2 secreted - disrupts Ti guidance

Dev Neurobiology extra (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions