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?
In the dorsal region of the neural tube; they migrate away from the neural tube into surrounding tissues.
The NC cells form the most significant cell types which are:
- neurons and glia of the sensory and autonomic systems (motor neurons are derived from shh)
- adrenal medulla and calcitonin cells of thyroid
- pigment cells (excluding pigment retina)
- skeletal tissues of the head
- part of cardiac outflow tract
The direction of movement of NC cells is:
anterior-posterior movement
Studying the NC cells movement, two techniques are used:
- cell tracing
- explants, grafts and ablations
- mutational analysis
Some crest cells are pluripotent while others are limited. Cell tracing is greatly facilitated by the use of cross-species chimeras such as:
quail/chick or xenopus laevis/borealis
From the organizer, the notochord, repressing signals of the BMPS are secreted. What are some of these signals/.
noggin, chordin, follistatin
strong BMP signals induce the specification of?
epidermis
moderate levels of BMP induce the specification of?
neural plate border
BMPs and Wnts continue to be expressed in the dorsal region of the closed neural tube, and this may be required for:
the maintenance and proliferation of the crest cells
The three main migration routes of cranial neural crest cells:
- 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
- Hindbrain neural crest migrates predominantly to the pharyngeal arches
- some hindbrain crest migrate laterally to form the cranial ganglia.
What does cardiac crest do?
located in the posterior region of hindbrain and has the ability to form endothelial tissue of the aortic arch and the septum
At around the time of neural plate closure the neural crest cells undergo a what transition?
epithelial to mesenchymal transition
cranial neural crest cells are located where?
mid brain and hindbrain
In the hindbrain, what is the dominant segmental units of the neural tube?
rhombomeres
In the trunk, what is the dominant segmental unit? and what does this give rise to?
somites; axial skeleton
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?
the paraxial mesoderm
In most vertebrates, the first pair of pharyngeal arches give rise to:
jaws
The positional identity of the neural crest cells is specified by expression of what genes?
Hox genes
trunk neural crest can be divided into two groups:
- anteroposterior axis form the dorsal root ganglia, sympathetic chain ganglia and melanocytes
- vagal-sacral levels form the enteric ganglia of the alimentary canal
mutations in the vagal-sacral level forming the enteric ganglia can result in:
“mega colon”. This condition is called Hirschsprung’s disease
Trunk NC cells have two migration pathways:
- The ventral pathway passes directly through the schlerotome of the adjacent somites
- The dorsal lateral pathway passes between the epidermis and the somite. This is the route of melanocytes
Early and later migration cells each follow which pathway?
early: ventral
later: dorsal lateral pathway
Which transcription factor is able to control the migration of NC cells?
slug. When slug is inhibited, neural crest cells are unable to migrate
How is slug able to control Nc migration?
regulate certain genes encoding cell adhesion molecules
