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Neural Crest Cells Biology 4361 July 24, 2008

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Neural Crest Cells

Biology 4361

July 24, 2008

Neural Crest ­ Overview

Neural crest derivatives

NC cell specification and migration

NC regions

Trunk

Vagal

Cardiac

Cranial

Ectodermal Derivatives

Neural crest – “4 th germ layer”

Neural Crest Derivatives

T. Halliday, 1980

Lora Bryson

Styracosaurus albertensis

© Franco Andreone

J. Briscoe

Michael Sereda, M. D.

Neural Crest Derivatives

Neural Crest Cells

Neurons, Schwann cells, pigment cells

Initiation – interactions between neural plate and presumptive epidermis ­ NC undergos epithelial­to­mesenchymal transformation

­ stimulated by Wnts, BMPs, FGFs

Neural Crest Migration

S.J Kimber

Migration pathways are controlled by extracellular matrices and by chemotactic factors ­ permissive and instructive signals ­ negative signals also

Soluble factors also control migration of certain NC cell populations; e.g. glial­derived neurotrophic factor ­ produced by the gut mesenchyme attracts vagal and sacral NC cells

Neural Crest Regions forebrain

Vagal Cardiac

Trunk

Sacral

hindbrain midbrain

Cranial

(named after the vagus nerve – innervates the heart)

Trunk Neural Crest

Ventrolateral

forebrain

Vagal

hindbrain midbrain

Sacral

Ventrolateral – early migration; into and through the anterior (not posterior) half of each somite

­ cells that travel through the somite form sympathetic ganglia, adrenal medulla, aortic nerve clusters

­ cells that remain in the somite = dorsal root ganglia (sensory neurons)

Two migration pathways:

somite

Trunk Neural Crest

Ventrolateral

Dorsolateral

forebrain

Vagal

hindbrain midbrain

Sacral

Dorsolateral – later migration; travel between ectoderm and somite mesoderm; later move into epidermis ­ form melanocytes

Ventrolateral – early migration; into and through the anterior (not posterior) half of each somite

Two migration pathways:

Vagal and sacral neural crest cells generate the parasympathetic (enteric) ganglia of the gut

Vagal and Sacral Neural Crest forebrain

Cardiac

hindbrain midbrain

Cranial

Trunk

Cranial (cephalic) neural crest cells form craniofacial mesenchyme; creates (among others) ­ facial cartilage and bone ­ cranial neurons ­ glia ­ connective tissue

Cranial Neural Crest

Cranial NC cells also enter pharyngeal arches and pouches; form ­ thymic cells ­ odontoblasts of tooth primordia ­ bones of the middle ear and jaw

forebrain

hindbrain midbrain

Cranial

Cranial NC Migration into Pharyngeal Arches

Neural crest cell migrate into pharyngeal arches

Human embryo 31 d

Pharyngeal arches

12

3

4

Mammalian Facial Development

upper and lower jaws

Nasal placode

Stomodeum

NC cells contribute: skeletal elements (face, hyoid, etc.) cartilage elements (e.g. in trachea) inner ear bones cranial nerves (V, VII, IX, X,)

Neural Crest Cells in Head and Face

Bone – Intramembranous Ossification ­ NC­derived mesenchyme condenses into nodules ­ some become osteoblasts – secrete collagen­proteoglycan osteoid matrix – binds calcium

­ osteocytes – osteoblasts that become embedded in the bony matrix ­ periosteum – membrane surrounding bones

Osteoblasts Osteocytes

Bone spicule – calcifiction

Cranial NC cells form facial skeleton:

Cardiac Neural Crest Cells The heart forms in the neck region, just below the pharyngeal arches

Cardiac NC cells form the endothelial lining of the aortic arches ­ also forms the septum between the aorta and pulmonary artery; divides the truncus arteriosus

Cardiac neural crest cells develop into melanocytes, neurons, cartilage, or connective tissue of the 3 rd , 4 th , & 6 th pharyngeal arches

Cardiac Neural Crest forebrain

Vagal Cardiac

hindbrain midbrain

Cranial

Trunk

Sacral