neurodevelopment 2 (Neurogenesis and Neural Differentiation)

pleiotrophy

One gene has many roles

• ex: Shh codes for eye cups, motor neurons, and floor plate

redundancy

many genes have same roles

• ex: noggin and chordin both work towards neural plate differentiation

symmetrical division

progenitor cells expand to create two identical cells

asymmetrical division

progenitor cell divides to create a progenitor and neuroglia

interkinetic nuclear migration

cell cycle dependent migration within neuroepithelial cells/radial glia

cell cycle during INM

S/G1= move away from the ventricular zone to SVZ

G2/M= move towards the ventricular zone

Mature cells (neurons first, then glia) move through the intermediate zone into the marginal zone

chick experiement

mark progenitor cell with a virus to see what daughter cells it creates

cortex development order

symetric progenitors→asymetric neurogenic→ symmetric neurogenic → gliogenic

Birthdating

done w/ BrDu or thymidine

tangenital migration

neurons move parallel to the brain surface (usually inhibitory neurons/interneurons while radial are excitatory)

RMS

Cells move from the lateral ventricle towards rostoral brain for olfactory bulb formation, held by astrocytes

glomerulus

structure within bulb where sensory neurons connect to mitral neurons, which are connected to granular neurons 1:1 (must travel through cribiform plate)

olfactory placode

create GnRH cells which move from nose to hypothalamus in order to create pituitary gland

cerebellar organization

external granule layer= granule cell precursors

molecular (outer)= purkinje dendrites, parallel fibers of granule cells

purkinje= cells,

granule (inner) = granule neurons and bergmann astrocytes

Granule migration

1. granule tangetially travel from rhombic lip

2. mature purkinje release Shh

3. granules undergo mitosis

4. granules travel inward along bergmann glia

5. purkinje and parellel fiber connect

weaver mice

mutation in granule cells, limiting moving inward

reeler mice

abscence of reelin to signal to glia, causing uncoordinated movement inward

reelin

signals which zone neurons (such as Purkinje cells) should stop during development by binding to ApoER2 receptors which releases Dab1 in cells

Neural crest fate

Pharyngeal arches create the PNS and face structures, which are determined by intrinsic and extrinsic factors that must travel through the basal lamina

To create PNS/moto neurons, ephrin repulsion from posterior somites causes anterior formation

BMP and rostoral= cranial structure

proliferative fraction

# of cells that remain in the cell cycle (progenitor cells/expansion)

quit fraction

# of cells that leave the cell cycle (differentiated/neurogenic)

spatial regulation

where a cell is located determines fate (ex morphogen gradient)

temporal regulation

when a cell differentiates determines fate (only certain signals at specific times)

ommatidia

light detecting unit in athropod eye with 8 photoreceptor neurons differentiated by furrow gradient movement (7th is for UV)

ommatidia lateral inhibition

delta from a neighbor cell binds to notch of daughter cell for progenitor while the other daughter cell inherits numb, causing a different fate

ectoderm neural differentiation

BMP=epithelium → epidermis

noggin/chordin= neuroectoderm → neural tube

Neural tube differentiation

Dorsal releases BMP/Wnts → PNS

Ventral releases Shh and Notch → gliogenesis → olgiodenrocytes or astrocytes

DELTA= NEURON NOTCH=GLIA

parasympathetic

cholinergic and cranial

adrenergic

sympathetic and trunk

transplanted neural crest cells

when cholernergic and adrenergic cells were transplated sacrally or thoracically, they adopted the new fate based on location and neighbors (FATE NON PREDETERMINED) this changes the older the neurons bexome (young can tranasplant to old but not vice versa)

retinal histogenesis

a single sheet of retinal progenitor cells generates all retinal neuron and glial cell types in a precise temporal order with RGCs first and then rods

neoteny

humans are most similar to anscesteral juvinille phase than other adult primates