Neural ( Neural Crest, Neural Tube, Neurons)

Neurulation

Ectoderm separates into surface ectoderm, neural crest, and neural tube

Neural Crest Cells

Migratory multipotent cells that form PNS, pigment cells, craniofacial structures

Cranial Neural Crest

Forms facial bones, cartilage, neurons; defects → craniofacial disorders

Cardiac Neural Crest

Forms heart outflow tract; defects → congenital heart defects

Trunk Neural Crest

Forms DRG neurons, sympathetic ganglia, melanocytes

Vagal/Sacral Neural Crest

Forms enteric nervous system; defects → Hirschsprung disease

Neural Crest EMT

Sox9, Snail, Slug, Twist enable migration

Cadherin Sorting

N-cadherin (neural) vs E-cadherin (epidermis) separates tissues

Roof Plate

High BMP → dorsal neural tube → sensory neurons

Floor Plate

Shh → ventral neural tube → motor neurons

Rho

Forms stress fibers and contraction

Rac

Forms lamellipodia (movement)

Cdc42

Forms filopodia (sensing)

Growth Cone

Guides axon movement via environmental cues

Attractant Cue

Pulls axon toward signal

Repellent Cue

Pushes axon away

Netrin (UNC-40)

Attracts axons

Netrin (UNC-5)

Repels axons

Slit/Robo

Prevents recrossing of midline

Ephs/Ephrins

Repel cells → restrict migration

Semaphorins/Neuropilins

Repel axons → guide pathfinding

Apoptosis (Neurons)

Removes excess neurons for proper circuit formation

Survival Signals

Target tissues release growth factors to prevent apoptosis