Neural Crest Flashcards
What induces neural crest into non-neuronal ectoderm?
- BMPs and Wnts
- inhibitory actions of noggin and chordin
What induces neural crest from mesoderm?
-FGF-8
While in the neural tube, neural crest cells are what? What helps form tight junctions?
- epithelial
- cadherins and other CAMs are important in forming tight junctions
What are the factors involved in neural crest breaking free?
- 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
What are the three migratory pathways of neural crest migration?
- ventral/sympathoadrenal path: first emigrating cells
- ventrolateral path: second wave of emigrating cells
- dorsolateral path: last wave of emigrating cells
What are the migratory neural crest substrates? Ligand/receptors?
-basal lamina is preferable
-extracellular matrix components
+fibronectin
+laminin
+type IV collagen
-ligand/receptor pair guidance molecules
+Robo/Slit
+neuropilin/semaphorin
+ephrin/eph
Early migratory neural crest cells:
-have most potential for differentiation
Later migratory neural crest cells:
-can only differentiate into cells characteristic of more dorsal locations
+spinal ganglia
Late migratory neural crest cells:
-can only form melanoblasts
What are the neural crest cell divisions?
-trunk neural crest
+sympathoadrenal lineage
+sensory lineage
+melanocyte lineage
- cranial neural crest
- circumpharyngeal neural crest
- cardiac neural crest
- vagal crest
Neural crest pathways extend from where?
-somite 6 caudally
Outline the sympathoadrenal pathway.
-follows intersomitic blood vessels around and between somites
Outline the ventrolateral pathway.
-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
Outline the dorsolateral pathway.
-migrate just beneath ectoderm
What happens to neural crest cells that take the sympathoadrenal lineage?
-gives rise to:
+adrenal chromatin cells
+adrenergic sympathetic neurons
+cholinergic sympathetic neurons
What happens to neural crest from the sensory/ventrolateral lineage?
- dorsal root ganglia
- Schwann cells
What happens to neural crest from the melanocyte/dorsolateral lineage?
-melanocytes
Cranial neural crest are thought to have been involved in evolution of what? Where do they arise from?
Vertebrate head
-cells arise from region of prosomere 1-3 and migrate as a continuous sheet over much of the head
What inhibits neural crest cells from arising anterior to diencephalon?
-Dickkopf-1
Cells arising from diencephalon posteriorly through R3 do not express what?
-Hox genes
Cells from R4 and posteriorly DO express what?
-Hox genes
Neural crest cells from R1-R2 -> pharyngeal arch 1
- does not require Hox influence
Neural crest cells from R4 -> pharyngeal arch 2
-requires Hoxa2 to keep it from becoming first arch
Neural crest cells from R6-R7 -> pharyngeal arch 3
-requires Hox3
Where does circumpharyngeal neural crest arise from?
-areas of somites 1-7
What does the circumpharyngeal ridge do?
- 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
Where does cardiac neural crest arise from?
-somites 1-3
Cardiac neural crest migrate toward the heart and give rise to what?
- septa that divide conus arteriosus into aortic and pulmonary arteries
- leaflets of semilunar valves
- thymus, thyroid, parathyroid glands
Where does vagal neural crest come from?
-arises from circumpharyngeal crest and exit from levels of somites 1-7
What is vagal neural crest associated with?
- gut enteric system (parasympathetic)
- dorsal root ganglia
- few sympathetic ganglia
What is Waardenburg’s syndrome?
-genetic disorder most often characterized by varying degrees of deafness, minor defects in structures arising from neural crest and pigmentation anomalies
What is DiGeorge syndrome?
- deletion of small piece of chromosome 22
- associated with truncus arteriosus and tetralogy of Fallot
What are neurofibromas?
-a benign nerve sheath tumor in the peripheral nervous system
Neural crest cells originate from where? What are they initially?
- lateral margins of the neural plate
- neural crest cells are initially epithelial in nature and then transform into mesenchymal cells for migratory purposes
