Growth Cone

Question 1

What did Ramon y Cajal do?

Answer 1

He studied the growth cone and described it as protoplasm of conical form that is soft and flexible, but contains motility where it pushes aside obstacles until reaches the region of its peripheral temrination

Question 2

What did Harrison do?

Answer 2

In 1907, Harrison showed in tissue culture experiments that growth cone is indeed motile

Question 3

What did Speidel do?

Answer 3

In 1933, Speidel also confirmed motility by in vivo live observation of growth cones in tadpole tails.

Question 4

What did Yamada do?

Answer 4

In 1970, Yamada revealed the cytoskeletal structures and their importance by EM studies.

Question 5

What is the definition of the neuronal growth cone?

Answer 5

It is a highly motile structure at the tip of growing axons and dendrites. It recognizes guidance information/cues in the embryonic environment and transduces it into directed movement towards the target cell.

Question 6

What are growth cone functions?

Answer 6

1. Sensing
2. Signaling
3. Be motile and do directional movement

Question 7

What are molecular components of sensing?

Answer 7

receptors for cues

Question 8

What are molecular components of signaling

Answer 8

signaling enzymes (kinases and RHO GTPases)

Question 9

What are molecular components of motility?

Answer 9

cytoskeletal and associated proteins

Question 10

What is filopodium?

Answer 10

spiky parts of growth cone where F-actin sticks out

Question 11

What is lamellipodium?

Answer 11

flat f-actin meshwork of growth cone

Question 12

What are the three major regions of growth cone?

Answer 12

A) Peripheral Domain (F-actin rich)
B) Transition zone
C) Central Domain (microtubule rich)

Question 13

Size and morphology depend on a number of factors, such as:

Answer 13

1. neuronal cell type
2. species
3. substrate and cell culture conditions

Question 14

How do filopodia and lamellipodia explore their space?

Answer 14

extension and retraction

Question 15

What do retinal ganglion cells cross to go into the brain

Answer 15

Optic Tectum

Question 16

What are the different F-actin structures?

Answer 16

1. filopodial actin bundles
2. lamellipodial networks
3. transverse actin arcs in transition zone (keep microtubules in central domain)
4. ruffles (intrapodia) in transition zone

Question 17

Where do you find microtubules

Answer 17

Mainly in the C domain, although dynamic MTs in P domain

Question 18

Where do you find F-actin?

Answer 18

mainly in the P domain

Question 19

What do they use to quantify cytoskeletal dynamics?

Answer 19

(FSM) - Fluorescent Speckle Microscopy

Question 20

What allows motility?

Answer 20

Actin filaments attach to substrate. Myosin which attached to microtubule attempts to pull f-actin back but instead pulls microtubule forward

Question 21

What drug blocks actin assembly

Answer 21

Cytochalasin B, it slows down growth

Question 22

What is the role of F-actin vs microtubules?

Answer 22

They are both important for growth cone guidance. F actin is more for motility. While microtubules for axonal outgrowth.