20 Flashcards
What are the key features of neural crest cells?
They form along the entire length of the most dorsal part of the neural tube, they undergo an EMT for migration, they differentiate into many different cell types, they migrate along specific streams, and migration is directed by chemotaxis and repulsion mediated by proteins like ephrins and their receptors.
What is required for neural crest cells to become migratory?
An EMT, which requires a loss of E-cadherin.
What are the main regions of the neural crest and what do they form?
- Vagal and sacral - form the gut
- Trunk - S6 to the tip of the tail, they form the dorsal root ganglion and the adrenal gland
- Cranial - form cartilage and bone in the brain/head, this is the only neural crest able to form bone
- Cardiac - the first 4 somites
Summarize some important neural crest derivatives.
PNS - neurons, neuroglial cells, schwann cells
Endocrine and paraendocrine - Adrenal medulla
Pigment cells - epidermal pigment cells except for retina
Facial cartilage and bones
Connective tissue - corneal endothelium, tooth papillae
How is the ENS formed and what is its role?
Glial-derived neurotrophic factor (GDNF) produced by the gut attracts neural crest cells with RET RTK receptors, this forms the ENS which is important for peristalsis.
What does a deficiency of GDNF or RET cause?
Hirschprung’s disease: failure of neural crest cells to migrate to the colon, reduced enteric neurons in colon and reduced or absent peristalsis. Faeces accumulates.
What are the two paths of trunk neural crest cell migration and what do they form?
Path 1: ventral. First. NC cells migrate in the anterior through the somites and become dorsal root ganglia (sensory neurons), sympathetic ganglia (chain ganglia ventral to roots), and the adrenal medulla.
Path 2: Dorsolateral. NC cells (melanoblasts) migrate later and become melanocytes
How do anterior and posterior somite sclerotomes form vertebral bones?
The posterior-most part of a somite groups up with the anterior-most part of the somite posterior to it.
How does ephrin in the sclerotome restrict neural crest cell migration?
It is a ligand beared in the posterior sclerotome cell membrane so it does not diffuse, it repels the neural crest cells and forces them to go anteriorly. Thus, cellular repulsion keeps the neural crest cells anteriorly.
What receptor pathways are involved in trunk cell migration pathway two?
Kit receptor tyrosine kinase. The receptor is present on neural crest cells, the SCF ligand is secreted by dermal cells which keeps these cells alive and proliferating and activates melanoblast specific genes through the TF MITF, making the neural crest now a melanoblast.
What happens in Kit mutations?
There isn’t enough or not enough functional Kit, the melanoblasts undergo apoptosis and this signaling affects the most ventral parts of the embryo (the forehead and tummy).
How many pharyngeal arches are there in vertebrates? In humans, specifically?
Five. We only have four, and so do other mammals.
What are pharyngeal arches composed of?
Ectoderm (neural crest and surface) and mesoderm.
What are the bone derivatives of the first pharyngeal arch?
The incus and malleus (from NC), mandible, maxilla, temporal bone regions (NC)
What are the bone derivatives of the second pharyngeal arch?
Stapes, styloid processes of temporal bone, part of hyoid bone of neck (all from NC cartilage)
