Exam 2 - Ectoderm, Neural Crest Cells & Axonal Specificity

motor neurons are made in the...

lower 1/2 of the neural tube

interkinetic nuclear migration

-the cells of the germinal neuroepithelium span the width of the epithelium (1 cell thick) but the cell nuclei are at different height in the epithelium

-the nuclei migrate up and down because they're at different points of their cell cycle

interkinetic nuclear migration types (2)

1) progenitor cell undergoes asymmetric division, renewing itself and generating a neuron
2) progenitor cell undergoes symmetric division generating 2 new progenitor cells

-these 2 types of growth are important as the neural tube keeps growing in order to maintain stem cell populations

-only happens to cells that can migrate out of the ventricular zone (aka migratory cells) that arose from asymmetric division of a progenitor cell

directed neuronal migration is regulated by...

-reelin!

-moderate levels stop a cell from migrating

-high levels allow for migration by changing shape

-any neuronal cell can migrate, so they all express high levels of reelin

-mutated / disrupted reelin STOPS migration out of the neuronal tube to form the brain

asymmetric radial glia division

mediated by Par3 and Notch; Par3 expressed at high levels in progenitor cells -> asymmetric inheritance

neural crest cells can form... (4)

1) neurons and glial cells
2) epinephrine-producing cells of adrenal gland
3) pigment-containing cells of epidermis
4) many skeletal and connective tissue components of the head

neural crest cell migration

-receive a moderate level of BMP -> will delaminate from the neural tube

-they need a signal to be able to do this

regionalization of the neural crest (4)

1) cranial
2) cardiac
3) trunk
4) vagal and sacral