Neural Crest

Question 1

What induces neural crest into non-neuronal ectoderm?

Answer 1

• BMPs and Wnts

- inhibitory actions of noggin and chordin

Question 2

What induces neural crest from mesoderm?

Answer 2

-FGF-8

Question 3

While in the neural tube, neural crest cells are what? What helps form tight junctions?

Answer 3

• epithelial

- cadherins and other CAMs are important in forming tight junctions

Question 4

What are the factors involved in neural crest breaking free?

Answer 4

• CAMs are lost and remain downregulated during migration but may be reexpressed at the end of migration
• Snail -1, Snail-2, and Foxd3 are important in allowing cells to break free

Question 5

What are the three migratory pathways of neural crest migration?

Answer 5

• ventral/sympathoadrenal path: first emigrating cells
• ventrolateral path: second wave of emigrating cells
• dorsolateral path: last wave of emigrating cells

Question 6

What are the migratory neural crest substrates? Ligand/receptors?

Answer 6

-basal lamina is preferable

-extracellular matrix components
+fibronectin
+laminin
+type IV collagen

-ligand/receptor pair guidance molecules
+Robo/Slit
+neuropilin/semaphorin
+ephrin/eph

Question 7

Early migratory neural crest cells:

Answer 7

-have most potential for differentiation

Question 8

Later migratory neural crest cells:

Answer 8

-can only differentiate into cells characteristic of more dorsal locations
+spinal ganglia

Question 9

Late migratory neural crest cells:

Answer 9

-can only form melanoblasts

Question 10

What are the neural crest cell divisions?

Answer 10

-trunk neural crest
+sympathoadrenal lineage
+sensory lineage
+melanocyte lineage

• cranial neural crest
• circumpharyngeal neural crest
• cardiac neural crest
• vagal crest

Question 11

Neural crest pathways extend from where?

Answer 11

-somite 6 caudally

Question 12

Outline the sympathoadrenal pathway.

Answer 12

-follows intersomitic blood vessels around and between somites

Question 13

Outline the ventrolateral pathway.

Answer 13

-neural crest cells enter and pass through anterior sclerotome compartments
+repulsed from posterior compartment by interaction of semaphorinA3F and neuropilin-2

+passage is facilitated via thrombospondin

Question 14

Outline the dorsolateral pathway.

Answer 14

-migrate just beneath ectoderm

Question 15

What happens to neural crest cells that take the sympathoadrenal lineage?

Answer 15

-gives rise to:
+adrenal chromatin cells

+adrenergic sympathetic neurons

+cholinergic sympathetic neurons

Question 16

What happens to neural crest from the sensory/ventrolateral lineage?

Answer 16

• dorsal root ganglia

- Schwann cells

Question 17

What happens to neural crest from the melanocyte/dorsolateral lineage?

Answer 17

-melanocytes

Question 18

Cranial neural crest are thought to have been involved in evolution of what? Where do they arise from?

Answer 18

Vertebrate head

-cells arise from region of prosomere 1-3 and migrate as a continuous sheet over much of the head

Question 19

What inhibits neural crest cells from arising anterior to diencephalon?

Answer 19

-Dickkopf-1

Question 20

Cells arising from diencephalon posteriorly through R3 do not express what?

Answer 20

-Hox genes

Question 21

Cells from R4 and posteriorly DO express what?

Answer 21

-Hox genes

Question 22

Neural crest cells from R1-R2 -> pharyngeal arch 1

Answer 22

• does not require Hox influence

Question 23

Neural crest cells from R4 -> pharyngeal arch 2

Answer 23

-requires Hoxa2 to keep it from becoming first arch

Question 24

Neural crest cells from R6-R7 -> pharyngeal arch 3

Answer 24

-requires Hox3

Question 25

Where does circumpharyngeal neural crest arise from?

Answer 25

-areas of somites 1-7

Question 26

What does the circumpharyngeal ridge do?

Answer 26

- arc shaped aggregation of cells passing behind 6th arch - cells migrate centrally and then cranially to provide pathways for CN XII and related musculature - most neural crest cells from somites 1-3 -> pass into pharyngeal arches 4 and 6 or form cardiac crest - neural crest cells from R4-7 -> make up vagal crest and form parasympathetic innervation for digestive tract

Question 27

Where does cardiac neural crest arise from?

Answer 27

-somites 1-3

Question 28

Cardiac neural crest migrate toward the heart and give rise to what?

Answer 28

- septa that divide conus arteriosus into aortic and pulmonary arteries - leaflets of semilunar valves - thymus, thyroid, parathyroid glands

Question 29

Where does vagal neural crest come from?

Answer 29

-arises from circumpharyngeal crest and exit from levels of somites 1-7

Question 30

What is vagal neural crest associated with?

Answer 30

- gut enteric system (parasympathetic) - dorsal root ganglia - few sympathetic ganglia

Question 31

What is Waardenburg's syndrome?

Answer 31

-genetic disorder most often characterized by varying degrees of deafness, minor defects in structures arising from neural crest and pigmentation anomalies

Question 32

What is DiGeorge syndrome?

Answer 32

- deletion of small piece of chromosome 22 | - associated with truncus arteriosus and tetralogy of Fallot

Question 33

What are neurofibromas?

Answer 33

-a benign nerve sheath tumor in the peripheral nervous system

Question 34

Neural crest cells originate from where? What are they initially?

Answer 34

- lateral margins of the neural plate | - neural crest cells are initially epithelial in nature and then transform into mesenchymal cells for migratory purposes