Early Spinal Cord and PNS Patterning

Question 1

What is the effect of grafting a notochord into a different embryo?

Answer 1

Induces ectopic floor plate - notochord is organising centre

Question 2

What is the effect of grafting a floor plate into a different embryo?

Answer 2

Induces ectopic MNs

Question 3

Which signalling molecule mediates ventral induction and what is its concentration gradient?

Answer 3

Sonic hedgehog (Shh)
High ventrally, low dorsally

Question 4

What is the effect of Shh on a multipotent stem cell?

Answer 4

Becomes post-mitotic unipotent progenitor

Question 5

Which type of genes does Shh inhibit and where are they expressed more?

Answer 5

Class I transcription factors

Expressed more dorsally

Question 6

Which type of genes does Shh activate and where are they expressed less?

Answer 6

Class II transcription factors

Expressed more ventrally

Question 7

What is the purpose of cross repression of progenitor homeodomain proteins?

Answer 7

Sharpens boundaries

Question 8

How does cross repression work?

Answer 8

Class I and II transcription factors inhibit each other - no cells express both

Question 9

What type of transcription factor is Nkx6 and what does it generate?

Answer 9

Class II

Motor neurons

Question 10

Along which axis do migrating neural crest cells have different fates?

Answer 10

Rostro-caudal axis

Question 11

What do cranial neural crest cells form?

Answer 11

Connective tissue and bone of face
Schwann cells
Odontoblasts

Question 12

What do vagal neural crest cells form?

Answer 12

Enteric NS

Question 13

What do trunk neural crest cells form?

Answer 13

Schwann cells

Sensory and sympathetic ganglia

Question 14

What do lumbo-sacral neural crest cells form?

Answer 14

Enteric NS

Question 15

What is the organising centre for dorsal spinal cell types and through which molecules does it act?

Answer 15

Roof plate

BMP and Wnt