Exam 2 - Neural Crest Cells

why are neural crest cells sensitive?

because they are migratory!

neural crest migration is..

bilateral

lineage segregation (4)

in the neural tube can become:
1) neurons
2) glia
3) cartilage
4) melanocyte

NC cell specification depends on..

position and location; signal received based on BMP and Wnts levels

delamination of NC cells

-cells in a layer leave independently and don't form a new layer

-after being specified, the first visible induction of NC cells is epithelial mesenchymal transition (EMT) in preparation for leaving the neural tube; NC cells lose their adhesive junctions and separate from the epithelium in the process of delamination

cadherin

keeps cells attached; cells receive a signal to NOT express cadherin in order to migrate & become pre-migratory NC cells

Rac1

localized where microfilaments grow

RhoA

disassembles the microfilaments on the trailing end of the cell; is expressed when cells are told to stop expressing cadherin -> starts migratory phase

RhoB

expressed in NC cells as they delaminate

contact inhibition of locomotion

occurs when 2 migratory cells make contact resulting in changes in their cytoskeletons and new protrusive extensions away from the point of contact, causing the cells to disperse

collective migration

some NC cells migrate as groups -> requires some cell-to-cell adhesion mediated by low cadherin levels

trunk cell migration (2 major pathways)

1) ventrolateral
2) dorsolateral

dorsolateral pathway

-cells travel over top of mesoderm between epidermis and dermis

-all pigment cells in vertebrates (except those of pigmented retina) are derived from NC cells

ventrolateral pathway

-cells travel ventrally through the anterior sclerotome; the cells here must decide whether to migrate BETWEEN the somites or THROUGH them

-early NC cells migrate between to form sympathetic ganglia

-semaphorin-3F repels NC cells and eventually blocks this pathway

-late NC cells are blocked by semaphorin-3F and migrate through somites to form dorsal root ganglia and ventral root

how do NC cells know which pathway to take?

ephrin expression! the earliest migrating cells are inhibited from using the dorsolateral pathway by ephrin secreted by the sclerotome; NO ephrin = YES dorsal migration; cells will take ventrolateral pathway when ephrin IS expressed

cranial NC cells

-use chemotactic migration -> chase and run

-chase = SDF1 is detected by NC cells making them migrate toward placode cell that's emitting it

-run = placode cell runs away due to contact inhibition

-eventually form some facial bones, trachea, cartilage etc.

cardiac NC cells

migrate dorsolaterally to take up residence in developing heart