neural crest Flashcards
what gives rise to the brain?
neural plate. develops from ectodermal cells
BMP prevents neural plate formation. What is the embryo’s mechanism for forming the neural plate then?
Nodal enhances the production of noggin and chordin whose main job is to restrict BMP activity. they restrict BMP activity in the midline so the neural plate can form there. the edge areas with high levels of BMP retains ectoderm that becomes epidermis.
what do the neural crest cells do after the neural tube has formed and they meet in the middle?
they migrate. once they start migrating, you cant tell them apart from other cells
what cells do neural crest cells give rise to?
pigment cells
sensory
adrenal cells
muscle and connective tissue
neurons and glia of cranial ganglia
what is the BMP levels found in the neural plate, neural crest, and epidermis respectively
low BMP-neural plate
intermediate BMP- neural crest
High BMP- epidermis
(look at top pic)
which molecule is responsible for defining the boundaries of each of the 3 sections?
Snail starts the first cascade but it includes BMP and FGF
what are the two steps in initiating neural crest migration?
- neural crest cells must turn from epithelial cells to mesenchymal cells through lose of their cadherin (adhesion protein/desmosomes)
- in order to have a space to migrate into, they use the help of GAGs thus hyaluronic acid is secreted into the space where they will migrate to
in the mutation in mice that alter pigmentation and cause sterility, what could be defective in the migratory cells to cause two phenotypes?
you have a defect in a ligand and the receptor. The receptor is a kinase called C-Kit and the ligand is called Steel Factor
do C-Kit mutations happen in humans and what is the presentation?
you see a deficit in the pigments. Where you have a light spot on the forehead and a light spot on the stomach
if the neural crest cells that are supposed to migrate into the gut fail to do so, what disease can this cause and what is the presentation?
Hirscgsprung’s disease. gut cannot empty leading to constipation.
What is the difference between C-kit/Steel factor and c-Ret and GDNF?
the first deals with the neural crest cells that become pigment cells and the second are the ones that migrate to the gut and colonize (hirschsprungs disease)
what actually determines where in the gut the neural crest cells will colonize?
the factor is actually made at the location that the body wants the neural crest cells to colonize. SO first large group of GDNF factors are made in the stomach so that is where the majority of the cells migrate to. but you want some in the colon too so the GDNF factors are produces in the colon, the neural crest cells sense that and lesser amount of them migrate to the colon
DiGeorge syndrome is characterized by defects in the pharyngies why?
neural crest cells migrate into the pharyngeal arches and if that is disrupted, you get DiGeorge syndrom. they then move down to the outflow track of the heart- so patients have heart defects too
what is the genetic etiology of the DiGeorge
its a deletion in human chromosome 22 that takes out oer 30 genes and affect 1/4000 births
what is Tbx and where is it located?
Tbx is a transcription factor implicated in the cause of DiGeorge syndrome. It is located entirely in the Pharynx and none in the neural crest. defect in these cells cause a defect in the pharynx and thus DiGeorge syndrome
what is the relationship between Tbx and Crkl?
Tbx gives the neural crest cells a normal environment to grow but then you still need Crkl to further help the growth of the neural crest cells in the pharynx
