Unit 3: The neural crest

Question 1

What is neural crest (3) ?

Answer 1

• Cell type only found in vertebrates (4th germ layer ?)
• Migratory cell
• Can differentiate into many different cell types

Question 2

Where does neural crest develop from ?

Answer 2

From the dorsal neural tube, along the hole A-P axis

Question 3

When does neural crest induction happen ?

Answer 3

Towards the end of neurulation

Question 4

Explain neural crest induction (4)

Answer 4

1) Ectoderm at edge of neural groove expresses genes Wnt6 and Bmp4
2) Dorsal neural tube then expresses FoxD3 and Slug
3) Slug binds to E-boxes on promotors of specific genes
4) As neural tube forms, edges become dorsal part of tube

Question 5

What is slug ?

Answer 5

• Transcriptional repressor
• Binds to E-boxes on the promotors of specific genes

Question 6

What is neural crest delamination ?

Answer 6

• When neural crest cells are formed at the edges of the neural tube and separated from the surrounding ectoderm
• Neural crest escapes on ECM

Question 7

What are the 3 derivatives of neural crest ?

Answer 7

1) The PNS
2) Pigment cells- melanocytes
3) Bone, cartilage and connective tissue (In head)

Question 8

How do sensory neurons develop ?

Answer 8

1) Neural crest migrates into the somite
2) It then differentiates into sensory neurons (DRG)

Question 9

How does the sympathetic nervous system develop ?

Answer 9

Neural crest migrates ventrally to sit near the dorsal aorta

Question 10

How does the parasympathetic nervous system develop ?

Answer 10

Neural crest migrates further ventrally to sit near gut, adrenal, heart and other tissues

Question 11

What are 3 advantages of having a PNS ?

Answer 11

1) Can detect changes in the environment
2) Can detect if being attacked
3) Can respond to changes and attack swiftly and in a coordinated manner

Question 12

What are 3 advantages of pigmentation ?

Answer 12

1) Camouflage
2) Attracting a mate
3) Protection from UV

Question 13

What is a melanocyte ?

Answer 13

Melanin cells that are derived from neural crest

Question 14

How does the chordates (amphioxus) neural crest differ from vertebrates ?

Answer 14

1) Their PNS is a loose net of epidermal neurons- no SNS or PNS so cannot respond to changes
2) Pigmentation only in nerve cord (retina and brain)- Vulnerable to being prayed upon
3) No skeleton so vulnerable to being squashed

Question 15

What are the 3 advantages of a head skeleton ?

Answer 15

1) Protection
2) Feeding and catching prey
3) Breathing