neural crest

Question 1

The neural crest cells (NC) are present in which part of the neural tube at the time of closure and what happen to these cells after the neural tube closes?

Answer 1

In the dorsal region of the neural tube; they migrate away from the neural tube into surrounding tissues.

Question 2

The NC cells form the most significant cell types which are:

Answer 2

1. neurons and glia of the sensory and autonomic systems (motor neurons are derived from shh)
2. adrenal medulla and calcitonin cells of thyroid
3. pigment cells (excluding pigment retina)
4. skeletal tissues of the head
5. part of cardiac outflow tract

Question 3

The direction of movement of NC cells is:

Answer 3

anterior-posterior movement

Question 4

Studying the NC cells movement, two techniques are used:

Answer 4

1. cell tracing
2. explants, grafts and ablations
3. mutational analysis

Question 5

Some crest cells are pluripotent while others are limited. Cell tracing is greatly facilitated by the use of cross-species chimeras such as:

Answer 5

quail/chick or xenopus laevis/borealis

Question 6

From the organizer, the notochord, repressing signals of the BMPS are secreted. What are some of these signals/.

Answer 6

noggin, chordin, follistatin

Question 7

strong BMP signals induce the specification of?

Answer 7

epidermis

Question 8

moderate levels of BMP induce the specification of?

Answer 8

neural plate border

Question 9

BMPs and Wnts continue to be expressed in the dorsal region of the closed neural tube, and this may be required for:

Answer 9

the maintenance and proliferation of the crest cells

Question 10

The three main migration routes of cranial neural crest cells:

Answer 10

1. Anterior cells migrate in the developing head and face, giving rise to facial mesenchyme that will form dermal bones, connective tissue surrounding the eye, eye’s ciliary and pupillary muscles, and dermis of the face
2. Hindbrain neural crest migrates predominantly to the pharyngeal arches
3. some hindbrain crest migrate laterally to form the cranial ganglia.

Question 11

What does cardiac crest do?

Answer 11

located in the posterior region of hindbrain and has the ability to form endothelial tissue of the aortic arch and the septum

Question 12

At around the time of neural plate closure the neural crest cells undergo a what transition?

Answer 12

epithelial to mesenchymal transition

Question 13

cranial neural crest cells are located where?

Answer 13

mid brain and hindbrain

Question 14

In the hindbrain, what is the dominant segmental units of the neural tube?

Answer 14

rhombomeres

Question 15

In the trunk, what is the dominant segmental unit? and what does this give rise to?

Answer 15

somites; axial skeleton

Question 16

The fate of the trunk NC cells are not determined during closure of neural plate. The grafted cells are respecified at their new position by signals from?

Answer 16

the paraxial mesoderm

Question 17

In most vertebrates, the first pair of pharyngeal arches give rise to:

Answer 17

jaws

Question 18

The positional identity of the neural crest cells is specified by expression of what genes?

Answer 18

Hox genes

Question 19

trunk neural crest can be divided into two groups:

Answer 19

1. anteroposterior axis form the dorsal root ganglia, sympathetic chain ganglia and melanocytes
2. vagal-sacral levels form the enteric ganglia of the alimentary canal

Question 20

mutations in the vagal-sacral level forming the enteric ganglia can result in:

Answer 20

“mega colon”. This condition is called Hirschsprung’s disease

Question 21

Trunk NC cells have two migration pathways:

Answer 21

1. The ventral pathway passes directly through the schlerotome of the adjacent somites
2. The dorsal lateral pathway passes between the epidermis and the somite. This is the route of melanocytes

Question 22

Early and later migration cells each follow which pathway?

Answer 22

early: ventral
later: dorsal lateral pathway

Question 23

Which transcription factor is able to control the migration of NC cells?

Answer 23

slug. When slug is inhibited, neural crest cells are unable to migrate

Question 24

How is slug able to control Nc migration?

Answer 24

regulate certain genes encoding cell adhesion molecules

Question 25

Cadherins are a type of cell adhesion molecule. Where are they generally expressed and what happen to them during NC cells migration?

Answer 25

dorsal neural tube. They are downreulated when cells are migrating, so that they don’t settle for any tissue parts yet (no adhesion). This allows continuous migration; they are once again expressed when NC cells have reached their destination.

Question 26

An intracellular protein involved in remodeling the cytoskeleton and required for neural crest migration isL

Answer 26

Rho

Question 27

Three growth factors in the neural tube that influence the fate of NC cellsL

Answer 27

1. Neuregulin (glial growth factor) –> Schwaan cells
2. TGF-beta–> smooth muscle
3. BMP2 and BMP4–> autonomic neurons

Question 28

What do the trunk NC cells form?

Answer 28

(Ventral, through anterior somite): dorsal root ganglia, sympathetic chain ganglia, adrenal medulla, glial cells in PNS,
(dorsolateral, around inside of epidermis): melanocytes
(vagal.sacral trunk crest, ventral, through anterior somite): enteric ganglia

Question 29

Melanocytes are only formed in the TNC, is this true or false?

Answer 29

False, it also forms in the Cranial NC.

Question 30

Which structures are formed by both the TNC and CNC?

Answer 30

melanocytes, glial cells in the peripheral nervous system.

Question 31

Some Nc cells migrate ventrally and stay in the schlerotomes. What do these form?

Answer 31

dorsal root ganglia

Question 32

What are glial cells?

Answer 32

support cells of the PNS; differentiate after the neuronal component; contact with axon is important in specification

Question 33

The NC cells differentiate into precursor schwann cell, immature schwann cell, and lastly divide into two groups:

Answer 33

Myelinating and non myelinating schwann cell

Question 34

Schwann cell progenitors continue to travel when they meet axons. True of false?

Answer 34

False. they stop

Question 35

Where are neuregulin expressed?

Answer 35

the motor neurons of the peripheral ganglia

Question 36

Neuregulin is a morphogen. What are it’s receptors on schwann cell precursor called?

Answer 36

ErbB receptors

Question 37

A single NC cell can differentiate into different cell types depending on its location. True of False?

Answer 37

True

Question 38

What cells are Not formed by the TNC cells?

Answer 38

odontoblasts