Neural Crest and Cranial Placodes

both neural crest and cranial placodes are induced at

the boarder of the neural plate

cranial placodes form at

most anterior boarder region

neural crest form

lateral to the neural plate from anterior to posterior

an initial WNT signal followed by BMP induces

cranial placodes

an initial WNT signal that is sustained, along with BMP signaling induces

neural crest

sustained WNT and BMP signaling induces

epidermis

the neural crest is called the

4th germ layer

neural crest forms a variety of cell types:

peripheral nerves, schwann cells, melanocytes, adrenal medulla, bones, cartilage

neural crest cells form at the boarder of the

neural plate and surface ectoderm

during neurulation, the neural crest will

undergo EMT, delaminate from the dorsal neural tube, and begin migration

delamination

the process where individual cells detach from an epithelial layer

protein RhoB promotes

cytoskeletal rearrangement

delamination requires

requires changes in the cytoskeleton that disrupt apical/basal polarity and changes in cell-cell adgesion mediated by cadherins

surface ectoderm expresses

E-cadherin

neural ectoderm expresses

N-cadherin

neural crest express

Cadherin-6B

different cadherin expression leads to

self-sorting

neural crest cells in contact promotes

reorganization of the cytoskeleton

contact inhibition promotes movement of neural crest cells

away from the midline

neural crest in all regions form

melanocytes, glia and schwann cells, melinges of brain and spinal cord, neurons

cranial neural crest generates

bone, cartilage, muscle, odontoblasts, neurons in cranial nerves

cardiac neural crest are a subregion of the

cranial neural crest

cardiac neural crest generate

the septum that separates the pulmonary artery from the aorta and the endothelium of the aortic arch arteries

trunk neural crest form

sensory neurons of the dorsal root ganglia, sympathetic ganglia, adrenal medulla, nerve clusters surrounding the aorta

vagal neural crest form at

the cranial neural crest and trunk neural crest boundary region

vagal neural crest form the majority of the

enteric nervous system

enteric nervous system

parasympathetic ganglia in the gut

sacral neural crest are at

the most posterior locations and contribute to the posterior enteric nervous system

migratory neural crest cells are

multipotential

newly induced neural crest progenitors are multipotent and can generate

cartilage, glia, melanocytes and neurons

neural crest along the anterior to posterior axis experience different

patterning cues that limit potential

migratory neural crest will

enter different environments and respond to difference signals to promote different cell fates

WNT and BMP signals at the neural plate boarder start a

neural crest transcriptional profile (a gene regulatory network)

somites

paraxial mesoderm, generate vertebrae and muscle

the first trunk neural cells to migrate from the neural tube

are repelled from the lateral pathway by signals in the ECM

trunk neural crest will move

in between the somites along the medial pathway and form the sympathetic ganglia

a secreted protein semaphorin-3F will

accumulate in between the somites and repel neural crest cells from this route

trunk neural crest will now

migrate through the anterior portion of each somite

trunk neural crest migration through anterior expresses

ECM proteins fibronectin and laminin which support migration

semaphorin-3F is

a repulsive guidance cue that binds to the receptor neuropilin-2

Ephrin is also

a repulsive guidance cue, which binds to Eph receptors

ephrin and semaphorin-3F are expressed in

the posterior somite

neural crest avoid _ when migrating through the anterior somite

ephrin and semaphorin-3F cues

repuslive guidance cues prevent

trunk neural crest cells from entering the gut

repulsive guidance cues are absent in

the region of the migrating vagal and sacral neural crest

GDNF is

an attractive guidance cue that binds to the Ret receptor, drawing vagal and sacral neural crest into the gut

enteric neurons grow towards

GDNF

late migrating neural crest cells that migrate along the lateral pathway will enter the

skin and forma melanoblasts

melanoblasts

stem cells for pigment

lateral migrating neural crest express

EphB2, a Eph receptor and are attracted towards the lateral path

mutations in genes for dorsolateral migrating neural crest and melanoblast

cause pigmentation defects

the face and skull of vertebrate embryos are largely generated from

cranial neural crest cells

cranial neural crest retain the

potency to generate bones, cartilage and muscles

mouse embryos deficient in neural crest do not

form a face

pharyngeal/brachial arches

paired bars of mesenchymal tissue covered by endoderm internally and ectoderm externally, found near pharynx of vertebrate embryos and form gill supports in fish, skeletal and connective tissue in the face, jaw, mouth and larynx in other vertebrates

the mesenchyme is a mix of

neural crest and paraxial and lateral plate mesoderm

cranial neural crest from rhombomeres of the hindbrain will

migrate into specific pharyngeal arches

cranial neural crest from the midbrain migrate into

frontonasal process, which forms the forehead and middle of the nose

neural crest cells from pharyngeal arches 3, 4, 6 migrate into

the outflow track of the developing heart and form the septum that separates the pulmonary artery from the aorta

cardiac neural crest also contribute to

thyroid, parathyroid, and thymus glands, which will form in the pharyngeal arch region

cranial placodes

thickenings in the surface ectoderm of the head that produce sensory and non-sensory structures, including the anterior pituitary gland, the olfactory epithelium, the lens of the eye, the inner ear, and parts of the cranial nerves

cranial placodes are derived from

common pre-placodal domain

the intermediate placode is the

trigeminal placode that produces the 5th cranial nerve

posterior placodes

otic (inner ear), epibranchial (7,9 and 10 cranial nerves)

anterior placodes

adenohypophyseal, olfactory placode, lens placode

the pre-placodal region is induced in the

non-neural ectoderm adjacent to the neural plate and neural crest, initial WNT signal followed by intermediate BMP

the induction of the pre-placodal region produces a

transcriptional response that includes Six1/4 and Eya1/2